Note: Descriptions are shown in the official language in which they were submitted.
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SOFT TISSUE PAPER HAVING A CHEMICAL SOFTENING
AGENT APPLIED ONTO A SURFACE THEREOF
FIELD OF THE INVENTION
This invention relates, in general, to tissue paper products. More
specifically, it relates
to tissue paper products having chemical softening agent(s) applied thereon.
BACKGROUND OF THE INVENTION
Sanitary paper tissue products such as facial tissues, toilet tissues and
absorbent towels
share a common need, specifically to be soft to the touch. Softness is a
complex tactile
impression elicited by a product when it is stroked against the skin. The
purpose of being soft is
so that these products can be used to cleanse the skin without being
irritating. Effectively
cleansing the skin is a persistent personal hygiene problem for many people.
Objectionable
discharges of urine, menses, and fecal matter from the perineal area or
otorhinolaryngogical
mucus discharges do not always occur at a time convenient for one to perform a
thorough
cleansing, as with soap and copious amounts of water for example. As a
substitute for thorough
cleansing, a wide variety of tissue and toweling products are offered to aid
in the task of
removing from the skin and retaining the before mentioned discharges for
disposal in a sanitary
fashion. Not surprisingly, the use of these products does not approach the
level of cleanliness
that can be achieved by the more thorough cleansing methods, and producers of
tissue and
toweling products are constantly striving to make their products compete more
favorably with
thorough cleansing methods.
Accordingly, making soft tissue and toweling products which promote
comfortable
cleaning without performance impairing sacrifices has long been the goal of
the engineers and
scientists who are devoted to research into improving tissue paper. There have
been numerous
attempts to reduce the abrasive effect, i.e., improve the softness of tissue
products.
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One area that has been exploited in this regard has been to select and modify
cellulose
fiber morphologies and engineer paper structures to take optimum advantages of
the various
available morphologies. Applicable art in this area include in U.S. Pat. Nos.
5,228,954;
5,405,499; 4,874,465; and 4,300,981.
Another area which has received a considerable amount of attention is the
addition of
chemical softening agents (also referred to herein as "chemical softeners") to
tissue and toweling
products.
As used herein, the term "chemical softening agent" refers to any chemical
ingredient
which improves the tactile sensation perceived by the consumer who holds a
particular paper
product and rubs it across the skin. Although somewhat desirable for towel
products, softness is
a particularly important property for facial and toilet tissues. Such tactile
perceivable softness
can be characterized by, but is not limited to, friction, flexibility, and
smoothness, as well as
subjective descriptors, such as lubricious, velvet, silk or flannel, which
imparts a lubricious feel
to tissue. This includes, for exemplary purposes only, basic waxes such as
paraffin and beeswax
and oils such as mineral oil and silicone oil as well as petrolatum and more
complex lubricants
and emollients such as quaternary ammonium compounds with long alkyl chains,
functional
silicones, fatty acids, fatty alcohols and fatty esters.
Thus, it would be advantageous to provide for the addition of chemical
softeners to
already-dried paper webs either at the so-called dry end of the papermaking
machine or in a
separate converting operation subsequent to the papermaking step. Exemplary
art from this field
includes U.S. Pat. Nos. 5,215,626; 5,246,545; and 5,525,345. While each of
these references
could represent advances over the previous so-called wet end methods
particularly with regard
to eliminating the degrading effects on the papermaking process, none are able
to completely
address the overall reduction of dust that accompanies such applications to
the dry paper web.
One of the most important physical properties related to softness is generally
considered
by those skilled in the art to be the strength of the web. Strength is the
ability of the product, and
its constituent webs, to maintain physical integrity and to resist tearing,
bursting, and shredding
under use conditions. Achieving a high softening potential without degrading
strength has long
been an object of workers in the field of the present invention.
Accordingly, it is an object of the present invention to provide a soft tissue
paper that
emits less dust during use without performance impairing sacrifices such as in
the strength of the
paper.
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SUMMARY OF THE INVENTION
The present invention provides for a tissue paper product having at least one
ply wherein
only one outer surface of the tissue paper product has an aqueous chemical
softening agent
applied and substantially affixed thereto at a concentration ranging from
about 0.45% to about
0.25%. The chemical softening agent provides the tissue paper product with a
raw dispensing
dust value. The raw dispensing dust value is less than about 4893.
The present invention also provides for a tissue paper product having at least
one ply
wherein only one outer surface of said tissue paper product has an aqueous
chemical softening
agent applied and substantially affixed thereto at a concentration ranging
from about 0.45% to
about 0.25%. The chemical softening agent provides the tissue paper product
with a raw dust
per raw lint value. The raw dust per raw lint value is less than about 804.8.
The present invention also provides for a tissue paper product having at least
one ply
wherein only one outer surface of said tissue paper product has an aqueous
chemical softening
agent applied and substantially affixed thereto at a concentration ranging
from about 0.45% to
about 0.25%. The chemical softening agent provides the tissue paper product
with a geometric
mean of dust x lint (GM D x L) value. The GM D x L value is less than about
176.5.
DETAILED DESCRIPTION OF THE INVENTION
As used herein, the term "water soluble" refers to materials that are soluble
in water to at
least 3%, by weight, at 25 C.
As used herein, the terms "tissue paper web, paper web, web, paper sheet and
paper
product" are all used interchangeably to refer to sheets of paper made by a
process comprising
the steps of forming an aqueous papermaking furnish, depositing this furnish
on a foraminous
surface, such as a Fourdrinier wire, and removing the water from the furnish
as by gravity or
vacuum-assisted drainage, forming an embryonic web, transferring the embryonic
web from the
forming surface to a transfer surface traveling at a lower speed than the
forming surface. The
web is then transferred to a fabric upon which it is through air dried to a
final dryness after
which it is wound upon a reel.
The terms "multi-layered tissue paper web, multi-layered paper web, multi-
layered web,
multi-layered paper sheet and multi-layered paper product" are all used
interchangeably in the
art to refer to sheets of paper prepared from two or more layers of aqueous
paper making furnish
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which are preferably comprised of different fiber types, the fibers typically
being relatively long
softwood and relatively short hardwood fibers as used in tissue paper making.
The layers are
preferably formed from the deposition of separate streams of dilute fiber
slurries upon one or
more endless foraminous surfaces. If the individual layers are initially
formed on separate
foraminous surfaces, the layers can be subsequently combined when wet to form
a multi-layered
tissue paper web.
As used herein, the term "single-ply tissue product" means that it is
comprised of one ply
of un-creped tissue; the ply can be substantially homogeneous in nature or it
can be a multi-
layered tissue paper web. As used herein, the term "multi-ply tissue product"
means that it is
comprised of more than one ply of un-creped tissue. The plies of a multi-ply
tissue product can
be substantially homogeneous in nature or they can be multi-layered tissue
paper webs.
As used herein, the term "substantively affixed chemical softening agent" is
defined as a
chemical agent which imparts lubricity or emolliency to tissue paper products
and also possesses
permanence with regard to maintaining the fidelity of its deposits without
substantial migration
when exposed to the environmental conditions to which products of this type
are ordinarily
exposed during their typical life cycle. Waxes and oils for example are
capable of imparting
lubricity or emolliency to tissue paper, but they suffer from a tendency to
migrate because they
have little affinity for the cellulose pulps which comprise the tissue papers
of the present
invention. While not wishing to be bound by theory, the substantively affixed
chemical softeners
of the present invention are believed to interact with the cellulose by
covalent, ionic, or
hydrogen bonding any of which are sufficiently potent to stem migration under
normal
environmental conditions.
Preferably, the substantively affixed chemical softening agents comprise
quaternary
ammonium compounds. Preferred quaternary compounds have the formula:
(R1)4-m - N+ - [RZ]m X
wherein:
mislto3;
R1 is a C1 -C6 alkyl group, hydroxyalkyl group, hydrocarbyl or substituted
hydrocarbyl group, alkoxylated group, benzyl group, or mixtures thereof;
R2 is a C14-C22 alkyl group, hydroxyalkyl group, hydrocarbyl or substituted
hydrocarbyl group, alkoxylated group, benzyl group, or mixtures thereof;
and
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X- is any softener-compatible anion are suitable for use in the present
invention.
Preferably, each Rl is methyl and X- is chloride or methyl sulfate.
Preferably, each R2 is
C16-C18 alkyl or alkenyl, most preferably each R2 is straight-chain C18 alkyl
or alkenyl.
Optionally, the R2 substituent can be derived from vegetable oil sources.
Such structures include the well-known dialkyldimethylammonium salts (e.g.
ditallowdimethylammonium chloride, ditallowdimethylammonium methyl sulfate,
di(hydrogenated tallow)dimethyl ammonium chloride, etc.), in which R1 are
methyl groups, R2
are tallow groups of varying levels of saturation, and X- is chloride or
methyl sulfate.
As discussed in Swern, Ed. in Bailey's Industrial Oil and Fat Products, Third
Edition,
John Wiley and Sons (New York 1964) tallow is a naturally occurring material
having a variable
composition. Table 6.13 in the above-identified reference edited by Swern
indicates that
typically 78% or more of the fatty acids of tallow contain 16 or 18 carbon
atoms. Typically, half
of the fatty acids present in tallow are unsaturated, primarily in the form of
oleic acid. Synthetic
as well as natural "tallows" fall within the scope of the present invention.
It is also known that
depending upon the product characteristic requirements the saturation level of
the ditallow can
be tailored from non hydrogenated (soft) to touch, partially or completely
hydrogenated (hard).
All of above-described levels of saturations are expressly meant to be
included within the scope
of the present invention.
Particularly preferred variants of these softening agents are what are
considered to be
mono or diester variations of these quaternary ammonium compounds having the
formula:
(R1)4-m - N+ - [(CHZ)n - Y - R31m X
wherein:
Y is --O--(O)C--, or --C(O)--O--, or --NH--C(O)--, or --C(O)--NH--;
mislto3;
nisOto4;
each R1 is a C1 -C6 alkyl group, hydroxyalkyl group, hydrocarbyl or
substituted
hydrocarbyl group, alkoxylated group, benzyl group, or mixtures thereof;
each R3 is a C13 -C.21 alkyl group, hydroxyalkyl group, hydrocarbyl or
substituted
hydrocarbyl group, alkoxylated group, benzyl group, or mixtures thereof; and
X- is any softener-compatible anion.
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Preferably, Y=--O--(O)C--, or --C(O)--O--; m=2; and n=2. Each R1 substituent
is
preferably a C1 -C3, alkyl group, with methyl being most preferred.
Preferably, each R3 is C13-
C17 alkyl and/or alkenyl, more preferably R3 is straight chain C15-C17 alkyl
and/or alkenyl, C15-
C17 alkyl, most preferably each R3 is straight-chain C17 alkyl. Optionally,
the R3 substituent can
be derived from vegetable oil sources.
As mentioned above, X- can be any softener-compatible anion, for example,
acetate,
chloride, bromide, methylsulfate, formate, sulfate, nitrate and the like.
Preferably X- is chloride
or methyl sulfate.
Specific examples of ester-functional quaternary ammonium compounds having the
structures detailed above and suitable for use in the present invention may
include the diester
dialkyl dimethyl ammonium salts such as diester ditallow dimethyl ammonium
chloride,
monoester ditallow dimethyl ammonium chloride, diester ditallow dimethyl
ammonium methyl
sulfate, diester di(hydrogenated)tallow dimethyl ammonium methyl sulfate,
diester
di(hydrogenated)tallow dimethyl ammonium chloride, and mixtures thereof.
Diester ditallow
dimethyl ammonium chloride and diester di(hydrogenated)tallow dimethyl
ammonium chloride
are particularly preferred. These particular materials are available
commercially from Witco
Chemical Company Inc. of Dublin, Ohio under the tradename "ADOGEN SDMC".
Typically, half of the fatty acids present in tallow are unsaturated,
primarily in the form
of oleic acid. Synthetic as well as natural "tallows" fall within the scope of
the present invention.
It is also known that depending upon the product characteristic requirements,
the saturation level
of the ditallow can be tailored from non hydrogenated (soft) to touch,
partially or completely
hydrogenated (hard). All of above-described levels of saturations are
expressly meant to be
included within the scope of the present invention.
It will be understood that substituents Rl, R2 and R3 may optionally be
substituted with
various groups such as alkoxyl, hydroxyl, or can be branched. As mentioned
above, preferably
each Rl is methyl or hydroxyethyl. Preferably, each R2 is C12-C18 alkyl and/or
alkenyl, most
preferably each R2 is straight-chain C16-C18 alkyl and/or alkenyl, most
preferably each R2 is
straight-chain C18 alkyl or alkenyl. Preferably R3 is C13-C17 alkyl and/or
alkenyl, most
preferably R3 is straight chain C15-C17 alkyl and/or alkenyl. Preferably, X-
is chloride or methyl
sulfate. Furthermore the ester-functional quaternary ammonium compounds can
optionally
contain up to about 10% of the mono(long chain alkyl) derivatives, e.g., (R2)2
-N+--((CH2)2 OH)
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((CH2)2 OC(O)R3) X- as minor ingredients. These minor ingredients can act as
emulsifiers and
can be useful in the present invention.
Other types of suitable quaternary ammonium compounds for use in the present
invention are described in U.S. Pat. Nos. 5,543,067; 5,538,595; 5,510,000;
5,415,737; and
European Patent Application No. 0 688 901 A2.
Di-quat variations of the ester-functional quaternary ammonium compounds can
also be
used, and are meant to fall within the scope of the present invention. These
compounds have the
formula:
0 (Rl)2 (Rl)2 0
II I I II
R1 - C - O - (CH2)2 - N+ - (CH2)n N+ - (CH2)2 - O - C - R3 2 X-
In the structure named above each Rl is a C1-C6 alkyl or hydroxyalkyl group,
R3 is C11-
C21 hydrocarbyl group, n is 2 to 4 and X- is a suitable anion, such as a
halide (e.g., chloride or
bromide) or methyl sulfate. Preferably, each R3 is C13-C17 alkyl and/or
alkenyl, most preferably
each R3 is straight-chain C15-C17 alkyl and/or alkenyl, and Rl is a methyl.
While not wishing to be bound by theory, it is believed that the ester
moiety(ies) of the
quaternary compounds provides a measure of biodegradability. It is believed
the ester-functional
quaternary ammonium compounds used herein biodegrade more rapidly than do
conventional
dialkyl dimethyl ammonium chemical softeners.
The use of quaternary ammonium ingredients before is most effectively
accomplished if
the quaternary ammonium ingredient is accompanied by an appropriate
plasticizer. The
plasticizer can be added during the quaternizing step in the manufacture of
the quaternary
ammonium ingredient or it can be added subsequent to the quaternization but
prior to the
application as a chemical softening agent. The plasticizer is characterized by
being substantially
inert during the chemical synthesis, but acts as a viscosity reducer to aid in
the synthesis and
subsequent handling, i.e. application of the quaternary ammonium compound to
the tissue paper
product. Preferred pasticizers are comprised of a combination of a non-
volatile polyhydroxy
compound and a fatty acid. Preferred polyhydroxy compounds include glycerol
and
polyethylene glycols having a molecular weight of from about 200 to about
2000, with
polyethylene glycol having a molecular weight of from about 200 to about 600
being
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particularly preferred. Preferred fatty acids comprise C6-C23 linear or
branched and saturated or
unsaturated analogs with isostearic acid being the most preferred.
While not wishing to be bound by theory, it is believed that a synergism
results from the
relationship of the polyhydroxy compound and the fatty acid in the mixture.
While the
polyhydroxy compound performs the essential function of viscosity reduction,
it can be quite
mobile after being laid down thus detracting from one of the objects of the
present invention, i.e.
that the deposited softener be substantively affixed. The inventors have now
found that the
addition of a small amount of the fatty acid is able to stem the mobility of
the polyhydroxy
compound and further reduce the viscosity of the mixture so as to increase the
processability of
compositions of a given quaternary ammonium compound fraction.
Alternative embodiments of preferred substantively affixed chemical softening
agents
comprise well-known organo-reactive polydimethyl siloxane ingredients,
including the most
preferred - amino functional polydimethyl siloxane.
A most preferred form of the substantively affixed softening agent is to
combine the
organo-reactive silicone with a suitable quaternary ammonium compound. In this
embodiment
the organo-reactive silicone is preferred to be an amino polydimethyl siloxane
and is used at an
amount ranging from 0 up to about 50% of the composition by weight, with a
preferred usage
being in the range of about 5% to about 15% by weight based on the weight of
the polysiloxane
relative to the total substantively affixed softening agent.
The soft tissue paper of the present invention preferably has a basis weight
ranging from
between about 5 g/m2 and about 120 g/m2, more preferably between about 10 g/m2
and about 55
g/m2, and even more preferably between about 10 g/m2 and about 30 g/m2. The
soft tissue paper
of the present invention preferably has a density ranging from between about
0.01 g/m3 and
about 0.19 g/cm3, more preferably between about 0.03 g/m3 and about 0.6 g/cm3,
and even more
preferably between about 0.1 g/cm3 and 0.2 g/cm3.
The soft tissue paper of the present invention further comprises papermaking
fibers of
both hardwood and softwood types wherein at least about 50% of the papermaking
fibers are
hardwood and at least about 10% are softwood. The hardwood and softwood fibers
are most
preferably isolated by relegating each to separate layers wherein the tissue
comprises an inner
layer and at least one outer layer.
The tissue paper product of the present invention is preferably creped, i.e.,
produced on a
papermaking machine culminating with a Yankee dryer to which a partially dried
papermaking
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web is adhered and upon which it is dried and from which it is removed by the
action of a
flexible creping blade.
Creping is a means of mechanically compacting paper in the machine direction.
The
result is an increase in basis weight (mass per unit area) as well as dramatic
changes in many
physical properties, particularly when measured in the machine direction.
Creping is generally
accomplished with a flexible blade, a so-called doctor blade, against a Yankee
dryer in an on
machine operation.
A Yankee dryer is a large diameter, generally 8-20 foot drum which is designed
to be
pressurized with steam to provide a hot surface for completing the drying of
papermaking webs
at the end of the papermaking process. The paper web which is first formed on
a foraminous
forming carrier, such as a Fourdrinier wire, where it is freed of the copious
water needed to
disperse the fibrous slurry is generally transferred to a felt or fabric in a
so-called press section
where de-watering is continued either by mechanically compacting the paper or
by some other
de-watering method such as through-drying with hot air, before finally being
transferred in the
semi-dry condition to the surface of the Yankee for the drying to be
completed.
While the characteristics of the creped paper webs, particularly when the
creping process
is preceded by methods of pattern densification, are preferred for practicing
the present
invention, uncreped tissue paper is also a satisfactory substitute and the
practice of the present
invention using uncreped tissue paper is specifically incorporated within the
scope of the present
invention. Uncreped tissue paper, a term as used herein, refers to tissue
paper which is non-
compressively dried, most preferably by through-drying. Resultant through air
dried webs are
pattern densified such that zones of relatively high density are dispersed
within a high bulk field,
including pattern densified tissue wherein zones of relatively high density
are continuous and the
high bulk field is discrete.
To produce un-creped tissue paper webs, an embryonic web is transferred from
the
foraminous forming carrier upon which it is laid, to a slower moving, high
fiber support transfer
fabric carrier. The web is then transferred to a drying fabric upon which it
is dried to a final
dryness. Such webs can offer some advantages in surface smoothness compared to
creped paper
webs.
Tissue paper webs are generally comprised essentially of papermaking fibers.
Small
amounts of chemical functional agents such as wet strength or dry strength
binders, retention
aids, surfactants, size, chemical softeners, crepe facilitating compositions
are frequently included
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but these are typically only used in minor amounts. The papermaking fibers
most frequently
used in tissue papers are virgin chemical wood pulps. Additionally, filler
materials may also be
incorporated into the tissue papers of the present invention.
Embodiments of the present invention wherein the substantively affixed
softening agent
comprises a quaternary ammonium compound further comprise from about 1% to
about 50% of
a polyhydroxy compound and from about 0.1% to about 10% of a fatty acid, each
as a
percentage of the weight of the quaternary ammonium compound.
Polyhydroxy compounds useful in this embodiment of the present invention
include
polyethylene glycol, polypropylene glycol and mixtures thereof.
Fatty acids useful in this embodiment of the present invention comprises C6-
C23 linear,
branched, saturated, or unsaturated analogs. The most preferred form of such a
fatty acid is
isostearic acid.
One particularly preferred chemical softening agent contains from about 0.1%
to about
70% of a polysiloxane compound.
Polysiloxanes which are applicable to chemical softening compositions of the
present
invention include polymeric, oligomeric, copolymeric, and other multiple
monomeric siloxane
materials. As used herein, the term polysiloxane shall include all of such
polymeric, oligomeric,
copolymeric, and other multiple-monomeric materials. Additionally, the
polysiloxane can be
straight chained, branched chain, or have a cyclic structure.
Preferred polysiloxane materials include those having monomeric siloxane units
of the
following structure:
R 1
I
3i O
RZ
wherein, Rl and Rl for each siloxane monomeric unit can independently be any
alkyl, aryl,
alkenyl, alkaryl, aralkyl, cycloalkyl, halogenated hydrocarbon, or other
radical. Any of such
radicals can be substituted or unsubstituted. Rl and R2 radicals of any
particular monomeric unit
may differ from the corresponding functionalities of the next adjoining
monomeric unit.
Additionally, the radicals can be either a straight chain, a branched chain,
or have a cyclic
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structure. The radicals Rl and R2 can, additionally and independently be other
silicone
functionalities such as, but not limited to siloxanes, polysiloxanes, and
polysilanes. The radicals
Rl and R2 can also contain any of a variety of organic functionalities
including, for example,
alcohol, carboxylic acid, and amine functionalities.
Reactive, organo-functional silicones, especially amino-functional silicones
are preferred
for the present invention.
Preferred polysiloxanes include straight chain organopolysiloxane materials of
the
following general formula:
.... RI R7 R9 R4
1 1 . F.1 .1
R Z- Si O Si - O Si - 0 Si R 5
I I I I
R g R g L R 10 R 6
a b
wherein each Rl -R9 radical can independently be any C1-Clo unsubstituted
alkyl or aryl radical,
and Rlo of any substituted C1-Clo alkyl or aryl radical. Preferably each R1 -
R9 radical is
independently any C1- C4 unsubstituted alkyl group those skilled in the art
will recognize that
technically there is no difference whether, for example, R9 or Rlo is the
substituted radical.
Preferably the mole ratio of b to (a+b) is between 0 and about 20%, more
preferably between 0
and about 10%, and most preferably between about 1 Io and about 5 Io.
In one particularly preferred embodiment, R1 -R9 are methyl groups and Rlo is
a
substituted or unsubstituted alkyl, aryl, or alkenyl group. Such material
shall be generally
described herein as polydimethylsiloxane which has a particular functionality
as may be
appropriate in that particular case. Exemplary polydimethylsiloxane include,
for example,
polydimethylsiloxane having an alkyl hydrocarbon Rlo radical and
polydimethylsiloxane having
one or more amino, carboxyl, hydroxyl, ether, polyether, aldehyde, ketone,
amide, ester, thiol,
and/or other functionalities including alkyl and alkenyl analogs of such
functionalities. For
example, an amino functional alkyl group as Rlo could be an amino functional
or an aminoalkyl-
functional polydimethylsiloxane. The exemplary listing of these
polydimethylsiloxanes is not
meant to thereby exclude others not specifically listed.
Viscosity of polysiloxanes useful for this invention may vary as widely as the
viscosity
of polysiloxanes in general vary, so long as the polysiloxane can be rendered
into a form which
can be applied to the tissue paper product herein. This includes, but is not
limited to, viscosity as
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low as about 25 centistokes to about 20,000,000 centistokes or even higher.
High viscosity
polysiloxanes which themselves are resistant to flowing can be effectively
deposited by
emulsifying with a surfactant or dissolution into a vehicle, such as hexane,
listed for exemplary
purposes only.
While not wishing to be bound by theory, it is believed that the tactile
benefit efficacy is
related to average molecular weight and that viscosity is also related to
average molecular
weight. Accordingly, due to the difficulty of measuring molecular weight
directly, viscosity is
used herein as the apparent operative parameter with respect to imparting
softness to tissue
paper.
References disclosing polysiloxanes include U.S. Pat. Nos. 2,826,551;
3,964,500;
4,364,837; 5,059,282; 5,529,665; 5,552,020; and British Patent 849,433.
It is anticipated that wood pulp in all its varieties will normally comprise
the tissue
papers with utility in this invention. However, other cellulose fibrous pulps,
such as cotton
linters, bagasse, rayon, etc., can be used and none are disclaimed. Wood pulps
useful herein
include chemical pulps such as, sulfite and sulfate (sometimes called Kraft)
pulps as well as
mechanical pulps including for example, ground wood, ThermoMechanical Pulp
(TMP) and
Chemi-ThermoMechanical Pulp (CTMP). Pulps derived from both deciduous and
coniferous
trees can be used.
Hardwood pulps and softwood pulps, as well as combinations of the two, may be
employed as papermaking fibers for the tissue paper of the present invention.
The term
"hardwood pulps" as used herein refers to fibrous pulp derived from the woody
substance of
deciduous trees (angiosperms), whereas "softwood pulps" are fibrous pulps
derived from the
woody substance of coniferous trees (gymnosperms). Blends of hardwood Kraft
pulps,
especially eucalyptus, and northern softwood Kraft (NSK) pulps are
particularly suitable for
making the tissue webs of the present invention. A preferred embodiment of the
present
invention comprises the use of layered tissue webs wherein, most preferably,
hardwood pulps
such as eucalyptus are used for outer layer(s) and wherein northern softwood
Kraft pulps are
used for the inner layer(s). Also applicable to the present invention are
fibers derived from
recycled paper, which may contain any or all of the above categories of
fibers.
In one preferred embodiment of the present invention, which utilizes multiple
papermaking furnishes, the furnish containing the papermaking fibers which
will be contacted
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by the particulate filler is predominantly of the hardwood type, preferably of
content of at least
about 80% hardwood.
Optional Chemical Additives
Other materials can be added to the aqueous papermaking furnish or the
embryonic web
to impart other characteristics to the product or improve the papermaking
process so long as they
are compatible with the chemistry of the substantively affixed softening agent
and do not
significantly and adversely affect the softness, strength, or low dusting
character of the present
invention. The following materials are expressly included, but their inclusion
is not offered to be
all-inclusive. Other materials can be included as well so long as they do not
interfere or
counteract the advantages of the present invention.
It is common to add a cationic charge biasing species to the papermaking
process to
control the zeta potential of the aqueous papermaking furnish as it is
delivered to the
papermaking process. These materials are used because most of the solids in
nature have
negative surface charges, including the surfaces of cellulosic fibers and
fines and most inorganic
fillers. One traditionally used cationic charge biasing species is alum. More
recently in the art,
charge biasing is done by use of relatively low molecular weight cationic
synthetic polymers
preferably having a molecular weight of no more than about 500,000 and more
preferably no
more than about 200,000, or even about 100,000. The charge densities of such
low molecular
weight cationic synthetic polymers are relatively high. These charge densities
range from about
4 to about 8 equivalents of cationic nitrogen per kilogram of polymer. One
example material is
Cypro 514®, a product of Cytec, Inc. of Stamford, Conn. The use of such
materials is
expressly allowed within the practice of the present invention.
The use of high surface area, high anionic charge microparticles can improve
the
formation, drainage, strength, and retention of the product. Exemplary high
anionic charge
microparticles would be known to those of skill in the art. By way of non-
limiting example,
common materials for this purpose could include silica colloid, or bentonite
clay. The
incorporation of such materials is expressly included within the scope of the
present invention.
If permanent wet strength is desired, the group of chemicals: including
polyamide-
epichlorohydrin, polyacrylamides, styrene-butadiene latices; insolubilized
polyvinyl alcohol;
urea-formaldehyde; polyethyleneimine; chitosan polymers and mixtures thereof
can be added to
the papermaking furnish or to the embryonic web. Polyamide-epichlorohydrin
resins are cationic
wet strength resins which have been found to be of particular utility.
Suitable types of such
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14
resins are described in U.S. Pat. Nos. 3,700,623 and 3,772,076. One commercial
source of useful
polyamide-epichlorohydrin resins is Hercules, Inc. of Wilmington, Del., which
markets such
resin under the mark Kymene 557H®).
Many paper products must have limited strength when wet because of the need to
dispose of them through toilets into septic or sewer systems. If wet strength
is imparted to these
products, it is preferred to be fugitive wet strength characterized by a decay
of part or all of its
potency upon standing in presence of water. If fugitive wet strength is
desired, the binder
materials can be chosen from the group consisting of dialdehyde starch or
other resins with
aldehyde functionality such as Co-Bond 1000.RTM offered by National Starch and
Chemical
Company, Parez 750.RTM offered by Cytec of Stamford, Conn. and the resin
described in U.S.
Pat. No. 4,981,557.
If enhanced absorbency is needed, surfactants may be used to treat the tissue
paper webs
of the present invention. The level of surfactant, if used, is preferably from
about 0.01% to about
2.0% by weight, based on the dry fiber weight of the tissue paper. The
surfactants preferably
have alkyl chains with eight or more carbon atoms. Exemplary anionic
surfactants are linear
alkyl sulfonates, and alkylbenzene sulfonates. Exemplary nonionic surfactants
are
alkylglycosides including alkylglycoside esters such as Crodesta SL-40.RTM
which is available
from Croda, Inc. (New York, N.Y.); alkylglycoside ethers as described in U.S.
Pat. No.
4,011,389, issued to W. K. Langdon, et al. on Mar. 8, 1977; and
alkylpolyethoxylated esters
such as Pegosperse 200 ML available from Glyco Chemicals, Inc. (Greenwich,
Conn.) and
IGEPAL RC-520.RTM available from Rhone Poulenc Corporation (Cranbury, N.J.).
The present invention is further applicable to the production of multi-layered
tissue paper
webs. Multilayered tissue structures and methods of forming multilayered
tissue structures are
described in U.S. Pat. Nos. 3,994,771; 4,300,981; 4,166,001; and European
Patent Publication
No. 0 613 979 Al. The layers preferably comprise different fiber types, the
fibers typically being
relatively long softwood and relatively short hardwood fibers as used in multi-
layered tissue
paper making. Multi-layered tissue paper webs resultant from the present
invention comprise at
least two superposed layers, an inner layer and at least one outer layer
contiguous with the inner
layer. Preferably, the multi-layered tissue papers comprise three superposed
layers, an inner or
center layer, and two outer layers, with the inner layer located between the
two outer layers. The
two outer layers preferably comprise a primary filamentary constituent of
relatively short paper
making fibers having an average fiber length between about 0.5 and about 1.5
mm, preferably
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less than about 1.0 mm. These short paper making fibers typically comprise
hardwood fibers,
preferably hardwood Kraft fibers, and most preferably derived from eucalyptus.
The inner layer
preferably comprises a primary filamentary constituent of relatively long
paper making fiber
having an average fiber length of least about 2.0 mm. These long paper making
fibers are
typically softwood fibers, preferably, northern softwood Kraft fibers.
Preferably, the majority of
the particulate filler of the present invention is contained in at least one
of the outer layers of the
multi-layered tissue paper web of the present invention. More preferably, the
majority of the
particulate filler of the present invention is contained in both of the outer
layers.
The tissue paper products made from single-layered or multi-layered un-creped
tissue
paper webs can be single-ply tissue products or multi-ply tissue products.
The term "dust" is used herein to refer to the tendency of a tissue paper web
to release
fibers or particulate fillers as measured in a controlled abrasion test,
described infra. Dust can
be related to strength since the tendency to release fibers or particles is
directly related to the
degree to which such fibers or particles are anchored into the structure. As
the overall level of
anchoring is increased, the strength will be increased. However, it is
possible to have a level of
strength which is regarded as acceptable but have an unacceptable level of
dust. This is because
dust can be localized. For example, the surface of a tissue paper web can be
prone to dust, while
the degree of bonding beneath the surface can be sufficient to raise the
overall level of strength
to quite acceptable levels. In another case, the strength can be derived from
a skeleton of
relatively long papermaking fibers, while fiber fines or the particulate
filler can be insufficiently
bound within the structure. The tissue paper webs of the present invention are
relatively low in
lint. Levels of lint below about 12 are preferable, and below about 10 are
more preferable.
The multi-layered tissue paper webs of to the present invention can be used in
any
application where soft, absorbent multi-layered tissue paper webs are
required. Particularly
advantageous uses of the multi-layered tissue paper web of this invention are
in toilet tissue and
facial tissue products. Both single-ply and multi-ply tissue paper products
can be produced from
the webs of the present invention.
Application of a Chemical Softening Agents to Paper Webs
In accordance with the present invention, chemical softening agents may be
applied to a
paper web by any application method known in the industry such as, for
example, spraying,
printing, extrusion, brushing, by means of permeable or impermeable rolls
and/or pads. In a first
embodiment, the claimed softening agent may be applied to a paper web with a
slot die.
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Specifically, the chemical softening agent may be extruded onto the surface of
a paper web via a
heated slot die. The slot die may be any suitable slot die or other means for
applying chemical
softening agent to the paper web. The slot die or other glue application means
may be supplied
by any suitable apparatus. For example, the slot die may be supplied by a
heated hopper or drum
and a variable speed gear pump through a heated hose. The chemical softening
agent is
preferably extruded onto the surface of the paper web at a temperature that
permits the chemical
softening agent to bond to the paper web. Depending on the particular
embodiment, the
chemical softening agent can be at least partially transferred to rolls in a
metering stack (if used)
and then to the paper web.
Additionally, the chemical softening agent may be applied to a paper web by an
apparatus comprising a fluid transfer component. The fluid transfer component
preferably
comprises a first surface and a second surface. The fluid transfer component
further preferably
comprises pores connecting the first surface and the second surface. The pores
are disposed
upon the fluid transfer component in a non-random pre-selected pattern. A
fluid supply is
operably (or fluidly) connected to the fluid transfer component such that a
fluid (such as the
chemical softening agent) may contact the first surface of the fluid transfer
component. The
apparatus further comprises a fluid motivating component. The fluid motivating
component
provides an impetus for the fluid to move from the first surface to the second
surface via the
pores. The apparatus further comprises a fluid receiving component comprising
a paper web.
The paper web comprises a fluid receiving (or outer) surface. The fluid
receiving surface may
contact droplets of fluid formed upon the second surface. Fluid may pass
through pores from
the first surface to the second surface and may transfer to the fluid
receiving surface.
The fluid transfer component may comprise a hollow cylindrical shell. The
cylindrical
shell may be sufficiently structural to function without additional internal
bracing. The
cylindrical shell may comprise a thin outer shell and structural internal
bracing to support the
cylindrical shell. The cylindrical shell may comprise a single layer of
material or may comprise
a laminate. The laminate may comprise layers of a similar material or may
comprise layers
dissimilar in material and structure. In one embodiment the cylindrical shell
comprises a
stainless steel shell having a wall thickness of about 0.125 inches (3 mm). In
another
embodiment (not shown) the fluid transfer component may comprise a flat plate.
In another
embodiment the fluid transfer component may comprise a regular or irregular
polygonal prism.
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The fluid application width of the apparatus may be adjusted by providing a
single fluid
transfer component of appropriate width. Multiple individual fluid application
components may
be combined in a series to achieve the desired width. In a non-liniiting
example, a plurality of
stainless steel cylinders each having a shell thickness of about 0.125 inches
(3 mm) and a width
of about 6 inches (about 15 cm) may be coupled end to end with an appropriate
seal - such as an
o-ring seal between each pair of cylinders. In this example, the number of
shells combined may
be increased until the desired application width is achieved.
The fluid transfer component preferably further comprises pores connecting the
first
surface and the second surface. Connecting the surfaces refers to the pores
each providing a
pathway for the transport of a fluid from the first surface to the second
surface. In one
embodiment, the pores may be formed by the use of electron beam drilling as is
known in the
art. Electron beam drilling comprises a process whereby high energy electrons
impinge upon a
surface resulting in the formation of holes through the material. In another
embodiment, the
pores may be formed using a laser. In another embodiment, the pores may be
formed by using a
drill bit. In yet another embodiment, the pores may be formed using electrical
discharge
machining as if known in the art.
In one embodiment, an array of pores may be disposed to provide a uniform
distribution
of fluid droplets to maximize the ratio of fluid surface area to applied fluid
volume. In one
embodiment, this may be used to apply a chemical softening agent in a pattern
of dots to
maximize the potential for adhesion between two surfaces for any volume of
applied chemical
softening agent.
The pattern of pores upon the second surface may comprise an array of pores
having a
substantially similar diameter or may comprise a pattern of pores having
distinctly different pore
diameters. In an alternative embodiment, the array of pores may comprise a
first set of pores
having a first diameter and arranged in a first pattern. The array further
comprises a second set
of pores having a second diameter and arranged in a second pattern. The first
and second
patterns may be arranged to interact each with the other.
Alternatively, the chemical softening agent may be sprayed directly onto the
surface of a
paper web using equipment suitable for such a purpose and as well known to
those of skill in the
art.
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Analytical and Testing Procedures
A. Density
The density of multi-layered tissue paper, as that term is used herein, is the
average
density calculated as the basis weight of that paper divided by the caliper,
with the appropriate
unit conversions incorporated therein. Caliper of the multi-layered tissue
paper, as used herein,
is the thickness of the paper when subjected to a compressive load of 95 g/in2
(15.5 g/cm2).
B. Dispensing Dust Test Method
Dust is measured using a particle counter commercially available (Sympatec
QICPIC,
Sympatec GmbH, Am Pulverhaus 1, 38678 Clausthal-Zellerfeld, Germany). The
instrument is
used according to the manufacturer's recommendation and a frame rate of 400
frames/sec is
selected. The particle size range is set to 20 to 10,000 micrometers.
Sympatec's standard chute
for guiding particles into the instrument was modified by removing the flights
within the chute
and by attaching a funnel to the top of the chute. The funnel is constructed
of stainless steel and
has 4 trapezoidal sides, 14 inches (35.6 cm) across the wide part (top),
tapering to 2 inches (5.1
cm) wide at the bottom, i.e. point of attachment with the chute. The trapezoid
sides are 12
inches (30.5 cm) long. A vacuum is attached to the exit of the instrument to
create an air flow
through the instrument, and consequently the chute and the funnel. The vacuum
is sufficient to
create an airspeed entering the funnel of 470 feet/min (14.3 Km/min). The
airspeed is measured
using an Extech Instruments ThermoAnemometer Mode1407113 and Anemometer metal
probe,
SN Q138487. The probe was mounted in a plastic tube in a square of foam
(necessitated by the
square shape of the funnel). The probe assembly was placed in the funnel so
that the foam sealed
against the funnel walls and the anemometer was centered above the shaft
opening. The linear
flow was calculated for the bottom of the funnel where the drop shaft begins
(the 2-inch x 2-inch
(5.08 cm x 5.08cm) opening).
To perform the dust test, sanitary tissue product is dispensed, i.e. pulled
apart at the
perforations, manually at the top of the funnel to release dust. The force to
rupture the product
at the perforations is a function of the dispensing tensile and the operator
merely applies enough
force directly in tension across the perforations to dispense the product in a
manner typical of
tissue dispensing. Care should be taken not to tear the product across any
perforations, rather it
should be dispensed by pulling directly in tension across the perforations.
The dust fibers and/or
particles so liberated are directed into a modified Sympatec chute and the
chute delivers them to
the measurement zone of the instrument by gravity and vacuum.
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The QICPIC measures the number of particles passing through the measurement
zone
using dynamic image analysis. Five perforations are separated per measurement
and the Raw
Dispensing Dust value is simply the total number of particles counted.
The raw data needs to be normalized for width of the product at the
perforations. The
Raw Dispensing Dust value is multiplied by the width of the product at the
perforations in
inches and divided by 4.27. This result is the Dispensing Dust value. Products
more than
about 6 inches (15.24 cm) wide should be pre-cut in width with scissors to
4.27 inches (10.85
cm) wide prior to testing to prevent being too wide to dispense properly in
tension.
The Normalized Dispensing Dust value is determined by any one of the following
relationships: 1) Dispensing Dust value divided by Dispensing Tensile and
multiplied by 150
yields the Tensile Normalized Dispensing Dust value; 2) Dispensing Dust Value
divided by Lint
test result and multiplied by 7 yields the Lint Normalized Dispensing Dust
value; and 3)
Dispensing Dust value divided by the product Density and multiplied by 0.08
yields the Density
Normalized Dispensing Dust value.
The calculated dust valves as related to the application rate to the paper web
(in lb/ton)
and application method (spray, extrusion, or printing) compared to a non-
treated paper web area
provided in Table 1 below.
Table 1. Calculated Dust Valves (in # particles) Compared to Application Rate
of Chemical
Softening Agent to Substrate and Application Method and Dust Reduction
Application Rate of Chemical Softening Spray Extrusion Print None
Agent to Substrate (particles) (particles)
(particles) (particles)
101b/ton 6435 5080 6485 7510
Percent Dust Reduction 14.3% 32.4% 13.6% ------
201b/ton 5815 5325 ------ 7510
------ ------
Percent Dust Reduction 22.6% 29.1%
C. Lint
The amount of lint generated from a tissue product is determined with a
Sutherland Rub
Tester. This tester uses a motor to rub a weighted felt 5 times over the
stationary toilet tissue.
The Hunter Color L value is measured before and after the rub test. The
difference between
these two Hunter Color L values is calculated as lint.
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Sample Preparation
Prior to the lint rub testing, the paper samples to be tested should be
conditioned
according to Tappi Method #T4020M-88. Here, samples are preconditioned for 24
hours at a
relative humidity level of 10 to 35% and within a temperature range of
22° to 40°
C. After this preconditioning step, samples should be conditioned for 24 hours
at a relative
humidity of 48 to 52% and within a temperature range of 22° to
24° C. This rub
testing should also take place within the confines of the constant temperature
and humidity
room.
The Sutherland Rub Tester may be obtained from Testing Machines, Inc.
(Amityville,
N.Y., 11701). The tissue is first prepared by removing and discarding any
product which might
have been abraded in handling, e.g. on the outside of the roll. For multi-ply
finished product,
three sections with each containing two sheets of multi-ply product are
removed and set on the
bench-top. For single-ply product, six sections with each containing two
sheets of single-ply
product are removed and set on the bench-top. Each sample is then folded in
half such that the
crease is running along the cross direction (CD) of the tissue sample. For the
multi-ply product,
make sure one of the sides facing out is the same side facing out after the
sample is folded. In
other words, do not tear the plies apart from one another and rub test the
sides facing one
another on the inside of the product. For the single-ply product, make up 3
samples with the wire
side out and 3 with the non-wire side out. Keep track of which samples are
wire side out and
which are non-wire side out.
Obtain a 30-inch x 40-inch (76.2 cm x 101.6 cm) piece of Crescent #300
cardboard from
Cordage Inc. (800 E. Ross Road, Cincinnati, Ohio, 45217). Using a paper
cutter, cut out six
pieces of cardboard having dimensions of 2.5 inches x 6 inches (6.35 cm x
15.24 cm). Puncture
two holes into each of the six cards by forcing the cardboard onto the hold
down pins of the
Sutherland Rub tester.
If working with single-ply finished product center, and carefully place, each
of the 2.5-
inch x 6-inch (6.35 cm x 15.24 cm) cardboard pieces on top of the six
previously folded
samples. Make sure the 6-inch (15.24 cm) dimension of the cardboard is running
parallel to the
machine direction (MD) of each of the tissue samples. If working with multi-
ply finished
product, only three pieces of the 2.5-inch x 6-inch (6.35 cm x 15.24 cm)
cardboard will be
required. Center and carefully place each of the cardboard pieces on top of
the three previously
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21
folded samples. Once again, make sure the 6-inch (15.24 cm) dimension of the
cardboard is
running parallel to the machine direction (MD) of each of the tissue samples.
Fold one edge of the exposed portion of tissue sample onto the back of the
cardboard.
Secure this edge to the cardboard with adhesive tape obtained from 3M Inc.
(3/4-inch (1.91 cm)
wide Scotch Brand, St. Paul, MN). Carefully grasp the other over-hanging
tissue edge and
snugly fold it over onto the back of the cardboard. While maintaining a snug
fit of the paper onto
the board, tape this second edge to the back of the cardboard. Repeat this
procedure for each
sample.
Turn over each sample and tape the cross direction edge of the tissue paper to
the
cardboard. One half of the adhesive tape should contact the tissue paper while
the other half is
adhering to the cardboard. Repeat this procedure for each of the samples. If
the tissue sample
breaks, tears, or becomes frayed at any time during the course of this sample
preparation
procedure, discard and make up a new sample with a new tissue sample strip.
If working with multi-ply converted product, there will now be 3 samples on
the
cardboard. For single-ply finished product, there will now be 3 wire-side out
samples on
cardboard and 3 non-wire side out samples on cardboard.
Felt Preparation
Obtain a 30-inch x 40-inch (76.2 cm x 101.6 cm) piece of Crescent #300
cardboard from
Cordage Inc. (800 E. Ross Road, Cincinnati, Ohio, 45217). Using a paper
cutter, cut out six
pieces of cardboard having dimensions of 2.25 inches x 7.25 inches (5.72 cm x
18.42 cm). Draw
two lines parallel to the short dimension and down 1.125 inches (2.86 cm) from
the top and
bottom most edges on the white side of the cardboard. Carefully score the
length of the line with
a razor blade using a straight edge as a guide. Score it to a depth about half
way through the
thickness of the sheet. This scoring allows the cardboard/felt combination to
fit tightly around
the weight of the Sutherland Rub tester. Draw an arrow running parallel to the
long dimension of
the cardboard on this scored side of the cardboard.
Cut the six pieces of black felt (F-55 or equivalent from New England Gasket,
550
Broad Street, Bristol, Conn. 06010) to the dimensions of 2.25 inches x 8.5
inches x 0.0625
inches (5.72 cm x 21.59 cm x 0.16 cm). Place the felt on top of the unscored,
green side of the
cardboard such that the long edges of both the felt and cardboard are parallel
and in alignment.
Make sure the fluffy side of the felt is facing up. Also allow about 0.5 inch
(1.27 cm) to
overhang the top and bottom most edges of the cardboard. Snuggly fold over
both overhanging
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22
felt edges onto the backside of the cardboard with Scotch brand tape. Prepare
a total of six of
these felt/cardboard combinations.
For best reproducibility, all samples should be run with the same lot of felt.
Obviously,
there are occasions where a single lot of felt becomes completely depleted. In
those cases where
a new lot of felt must be obtained, a correction factor should be determined
for the new lot of
felt. To determine the correction factor, obtain a representative single
tissue sample of interest,
and enough felt to make up 24 cardboard/felt samples for the new and old lots.
As described below and before any rubbing has taken place, obtain Hunter L
readings
for each of the 24 cardboard/felt samples of the new and old lots of felt.
Calculate the averages
for both the 24 cardboard/felt samples of the old lot and the 24
cardboard/felt samples of the
new lot.
Next, rub test the 24 cardboard/felt boards of the new lot and the 24
cardboard/felt
boards of the old lot as described below. Make sure the same tissue lot number
is used for each
of the 24 samples for the old and new lots. In addition, sampling of the paper
in the preparation
of the cardboard/tissue samples must be done so the new lot of felt and the
old lot of felt are
exposed to as representative as possible of a tissue sample. For the case of 1-
ply tissue product,
discard any product which might have been damaged or abraded. Next, obtain 48
strips of tissue
each two usable units (also termed sheets) long. Place the first two usable
unit strip on the far
left of the lab bench and the last of the 48 samples on the far right of the
bench. Mark the
sample to the far left with the number "1" in a 1 cm by 1 cm area of the
corner of the sample.
Continue to mark the samples consecutively up to 48 such that the last sample
to the far right is
numbered 48.
Use the 24 odd numbered samples for the new felt and the 24 even numbered
samples
for the old felt. Order the odd number samples from lowest to highest. Order
the even numbered
samples from lowest to highest. Now, mark the lowest number for each set with
a letter "W."
Mark the next highest number with the letter "N." Continue marking the samples
in this
alternating "W"/"N" pattern. Use the "W" samples for wire side out lint
analyses and the "N"
samples for non-wire side lint analyses. For 1-ply product, there are now a
total of 24 samples
for the new lot of felt and the old lot of felt. Of this 24, twelve are for
wire side out lint analysis
and 12 are for non-wire side lint analysis.
Rub and measure the Hunter Color L values for all 24 samples of the old felt
as
described below. Record the 12 wire side Hunter Color L values for the old
felt. Average the
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23
12 values. Record the 12 non-wire side Hunter Color L values for the old felt.
Average the 12
values. Subtract the average initial un-rubbed Hunter Color L felt reading
from the average
Hunter Color L reading for the wire side rubbed samples. This is the delta
average difference
for the wire side samples. Subtract the average initial un-rubbed Hunter Color
L felt reading
from the average Hunter Color L reading for the non-wire side rubbed samples.
This is the delta
average difference for the non-wire side samples. Calculate the sum of the
delta average
difference for the wire side and the delta average difference for the non-wire
side and divide this
sum by 2. This is the uncorrected lint value for the old felt. If there is a
current felt correction
factor for the old felt, add it to the uncorrected lint value for the old
felt. This value is the
corrected Lint Value for the old felt.
Rub and measure the Hunter Color L values for all 24 samples of the new felt
as
described below. Record the 12 wire side Hunter Color L values for the new
felt. Average the
12 values. Record the 12 non-wire side Hunter Color L values for the new felt.
Average the 12
values. Subtract the average initial un-rubbed Hunter Color L felt reading
from the average
Hunter Color L reading for the wire side rubbed samples. This is the delta
average difference
for the wire side samples. Subtract the average initial un-rubbed Hunter Color
L felt reading
from the average Hunter Color L reading for the non-wire side rubbed samples.
This is the delta
average difference for the non-wire side samples. Calculate the sum of the
delta average
difference for the wire side and the delta average difference for the non-wire
side and divide this
sum by 2. This is the uncorrected lint value for the new felt.
Take the difference between the corrected Lint Value from the old felt and the
uncorrected lint value for the new felt. This difference is the felt
correction factor for the new
lot of felt.
Adding this felt correction factor to the uncorrected lint value for the new
felt should be
identical to the corrected Lint Value for the old felt.
The same type procedure is applied to two-ply tissue product with 24 samples
run for the
old felt and 24 run for the new felt. But, only the consumer used outside
layers of the plies are
rub tested. As noted above, make sure the samples are prepared such that a
representative
sample is obtained for the old and new felts.
Care of 4-Pound (1.8 KO Wei~zht
The four pound weight has four square inches of effective contact area
providing a
contact pressure of one pound per square inch. Since the contact pressure can
be changed by
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24
alteration of the rubber pads mounted on the face of the weight, it is
important to use only the
rubber pads supplied by the manufacturer (Brown Inc., Mechanical Services
Department,
Kalamazoo, Mich.). These pads must be replaced if they become hard, abraded or
chipped off.
When not in use, the weight must be positioned such that the pads are not
supporting the
full weight of the weight. It is best to store the weight on its side.
Rub Tester Instrument Calibration
The Sutherland Rub Tester must first be calibrated prior to use. First, turn
on the
Sutherland Rub Tester by moving the tester switch to the "cont" position. When
the tester arm is
in its position closest to the user, turn the tester's switch to the "auto"
position. Set the tester to
run 5 strokes by moving the pointer arm on the large dial to the "five"
position setting. One
stroke is a single and complete forward and reverse motion of the weight. The
end of the
rubbing block should be in the position closest to the operator at the
beginning and at the end of
each test.
Prepare a tissue paper on cardboard sample as described above. In addition,
prepare a
felt on cardboard sample as described above. Both of these samples will be
used for calibration
of the instrument and will not be used in the acquisition of data for the
actual samples.
Place this calibration tissue sample on the base plate of the tester by
slipping the holes in
the board over the hold-down pins. The hold-down pins prevent the sample from
moving during
the test. Clip the calibration felt/cardboard sample onto the four pound
weight with the
cardboard side contacting the pads of the weight. Make sure the cardboard/felt
combination is
resting flat against the weight. Hook this weight onto the tester arm and
gently place the tissue
sample underneath the weight/felt combination. The end of the weight closest
to the operator
must be over the cardboard of the tissue sample and not the tissue sample
itself. The felt must
rest flat on the tissue sample and must be in 100% contact with the tissue
surface. Activate the
tester by depressing the "push" button.
Keep a count of the number of strokes and observe and make a mental note of
the
starting and stopping position of the felt covered weight in relationship to
the sample. If the total
number of strokes is five and if the end of the felt covered weight closest to
the operator is over
the cardboard of the tissue sample at the beginning and end of this test, the
tester is calibrated
and ready to use. If the total number of strokes is not five or if the end of
the felt covered weight
closest to the operator is over the actual paper tissue sample either at the
beginning or end of the
test, repeat this calibration procedure until 5 strokes are counted the end of
the felt covered
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weight closest to the operator is situated over the cardboard at the both the
start and end of the
test.
During the actual testing of samples, monitor and observe the stroke count and
the
starting and stopping point of the felt covered weight. Recalibrate when
necessary.
Hunter Color Meter Calibration
Adjust the Hunter Color Difference Meter for the black and white standard
plates
according to the procedures outlined in the operation manual of the
instrument. Also run the
stability check for standardization as well as the daily color stability check
if this has not been
done during the past eight hours. In addition, the zero reflectance must be
checked and
readjusted if necessary.
Place the white standard plate on the sample stage under the instrument port.
Release the
sample stage and allow the sample plate to be raised beneath the sample port.
Using the "L-Y", "a-X", and "b-Z" standardizing knobs, adjust the instrument
to read the
Standard White Plate Values of "L", "a", and "b" when the "L", "a", and "b"
push buttons are
depressed in turn.
Measurement of Samples
The first step in the measurement of lint is to measure the Hunter color
values of the
black felt/cardboard samples prior to being rubbed on the tissue. The first
step in this
measurement is to lower the standard white plate from under the instrument
port of the Hunter
color instrument. Center a felt covered cardboard, with the arrow pointing to
the back of the
color meter, on top of the standard plate. Release the sample stage, allowing
the felt covered
cardboard to be raised under the sample port.
Since the felt width is only slightly larger than the viewing area diameter,
make sure the
felt completely covers the viewing area. After confirming complete coverage,
depress the L push
button and wait for the reading to stabilize. Read and record this L value to
the nearest 0.1 unit.
If a D25D2A head is in use, lower the felt covered cardboard and plate, rotate
the felt
covered cardboard 90 degrees so the arrow points to the right side of the
meter. Next, release the
sample stage and check once more to make sure the viewing area is completely
covered with
felt. Depress the L push button. Read and record this value to the nearest 0.1
unit. For the
D25D2M unit, the recorded value is the Hunter Color L value. For the D25D2A
head where a
rotated sample reading is also recorded, the Hunter Color L value is the
average of the two
recorded values.
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Measure the Hunter Color L values for all of the felt covered cardboards using
this
technique. If the Hunter Color L values are all within 0.3 units of one
another, take the average
to obtain the initial L reading. If the Hunter Color L values are not within
the 0.3 units, discard
those felt/cardboard combinations outside the limit. Prepare new samples and
repeat the Hunter
Color L measurement until all samples are within 0.3 units of one another.
For the measurement of the actual tissue paper/cardboard combinations, place
the tissue
sample/cardboard combination on the base plate of the tester by slipping the
holes in the board
over the hold-down pins. The hold-down pins prevent the sample from moving
during the test.
Clip the calibration felt/cardboard sample onto the four pound weight with the
cardboard side
contacting the pads of the weight. Make sure the cardboard/felt combination is
resting flat
against the weight. Hook this weight onto the tester arm and gently place the
tissue sample
underneath the weight/felt combination. The end of the weight closest to the
operator must be
over the cardboard of the tissue sample and not the tissue sample itself. The
felt must rest flat on
the tissue sample and must be in 100% contact with the tissue surface.
Next, activate the tester by depressing the "push" button. At the end of the
five strokes
the tester will automatically stop. Note the stopping position of the felt
covered weight in
relation to the sample. If the end of the felt covered weight toward the
operator is over
cardboard, the tester is operating properly. If the end of the felt covered
weight toward the
operator is over sample, disregard this measurement and recalibrate as
directed above in the
Sutherland Rub Tester Calibration section.
Remove the weight with the felt covered cardboard. Inspect the tissue sample.
If torn,
discard the felt and tissue and start over. If the tissue sample is intact,
remove the felt covered
cardboard from the weight. Determine the Hunter Color L value on the felt
covered cardboard as
described above for the blank felts. Record the Hunter Color L readings for
the felt after
rubbing. Rub, measure, and record the Hunter Color L values for all remaining
samples.
After all tissues have been measured, remove and discard all felt. Felts
strips are not
used again. Cardboards are used until they are bent, torn, limp, or no longer
have a smooth
surface.
Calculations
Determine the delta L values by subtracting the average initial L reading
found for the
unused felts from each of the measured values for the wire side and the non-
wire side of the
sample. Recall, multi-ply-ply product will only rub one side of the paper.
Thus, three delta L
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27
values will be obtained for the multi-ply product. Average the three delta L
values and subtract
the felt factor from this final average. This final result is termed the lint
for the 2-ply product.
For the single-ply product where both wire side and non-wire side measurements
are
obtained, subtract the average initial L reading found for the unused felts
from each of the three
wire side L readings and each of the three non-wire side L readings. Calculate
the average delta
for the three wire side values. Calculate the average delta for the three non-
wire side values.
Subtract the felt factor from each of these averages. The final results are
termed a lint unit for
the non-wire side and a lint unit for the wire side of the single-ply product.
By taking the
average of these two values, an ultimate lint unit is obtained for the entire
single-ply product.
D. Total Tensile
Insert the flat face clamps into the unit and calibrate the tester according
to the
instructions given in the operation manual of the Thwing-Albert Intelect II.
Set the instrument
crosshead speed to 4.00 in/min (10.2 cm/min) and the 1st and 2nd gauge lengths
to 2.00 inches
(5.1 cm). The break sensitivity should be set to 20.0 grams and the sample
width should be set to
1.00 inch (2.54 cm) and the sample thickness at 0.025 inches (0.6 cm).
A load cell is selected such that the predicted tensile result for the sample
to be tested lies
between 25% and 75% of the range in use. For example, a 5000 gram load cell
may be used for
samples with a predicted tensile range of 1250 grams (25% of 5000 grams) and
3750 grams
(75% of 5000 grams). The tensile tester can also be set up in the 10% range
with the 5000 gram
load cell such that samples with predicted tensiles of 125 grams to 375 grams
could be tested.
Take one of the tensile strips and place one end of it in one clamp of the
tensile tester.
Place the other end of the paper strip in the other clamp. Make sure the long
dimension of the
strip is running parallel to the sides of the tensile tester.
After inserting the paper test strip into the two clamps, the instrument
tension can be
monitored. If it shows a value of 5 grams or more, the sample is too taut.
Conversely, if a period
of 2-3 seconds passes after starting the test before any value is recorded,
the tensile strip is too
slack.
Start the tensile tester as described in the tensile tester instrument manual.
The test is
complete after the crosshead automatically returns to its initial starting
position. Read and record
the tensile peak load in units of grams from the instrument scale or the
digital panel meter to the
nearest unit.
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If the reset condition is not performed automatically by the instrument,
perform the
necessary adjustment to set the instrument clamps to their initial starting
positions. Insert the
next paper strip into the two clamps as described above and obtain a tensile
reading in units of
grams. Obtain tensile readings from all the paper test strips. It should be
noted that readings
should be rejected if the strip slips or breaks in or at the edge of the
clamps while performing the
test.
Unit of Measure: grams/inch per sample width (e.g. 1.0 inches (2.54 cm));
Total Dry
Strength is the arithmetic sum of the MD + CD tensile
E. Measurement of Panel Softness of Tissue Papers
Ideally, prior to softness testing, the paper samples to be tested should be
conditioned
according to Tappi Method #T4020M-88. Here, samples are preconditioned for 24
hours at a
relative humidity level of 10 to 35% and within a temperature range of 22 to
40 C. After this
preconditioning step, samples should be conditioned for 24 hours at a relative
humidity of 48 to
52% and within a temperature range of 22 C to 24 C.
Ideally, the softness panel testing should take place within the confines of a
constant
temperature and humidity room. If this is not feasible, all samples, including
the controls, should
experience identical environmental exposure conditions.
Softness testing is performed as a paired comparison in a form similar to that
described
in "Manual on Sensory Testing Methods", ASTM Special Technical Publication
434, published
by the American Society for Testing and Materials 1968 and is incorporated
herein by reference.
Softness is evaluated by subjective testing using what is referred to as a
Paired Difference Test.
The method employs a standard external to the test material itself. For
tactile perceived softness
two samples are presented such that the subject cannot see the samples, and
the subject is
required to choose one of them on the basis of tactile softness. The result of
the test is reported
in what is referred to as Panel Score Unit (PSU). With respect to softness
testing to obtain the
softness data reported herein in PSU, a number of softness panel tests are
performed. In each test
ten practiced softness judges are asked to rate the relative softness of three
sets of paired
samples. The pairs of samples are judged one pair at a time by each judge: one
sample of each
pair being designated X and the other Y. Briefly, each X sample is graded
against its paired Y
sample as follows:
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1. a grade of plus one is given if X is judged to may be a little softer than
Y, and a grade
of minus one is given if Y is judged to may be a little softer than X;
2. a grade of plus two is given if X is judged to surely be a little softer
than Y, and a
grade of minus two is given if Y is judged to surely be a little softer than
X;
3. a grade of plus three is given to X if it is judged to be a lot softer than
Y, and a grade
of minus three is given if Y is judged to be a lot softer than X; and, lastly:
4. a grade of plus four is given to X if it is judged to be a whole lot softer
than Y, and a
grade of minus 4 is given if Y is judged to be a whole lot softer than X.
The grades are averaged and the resultant value is in units of PSU. The
resulting data are
considered the results of one panel test. If more than one sample pair is
evaluated then all sample
pairs are rank ordered according to their grades by paired statistical
analysis. Then, the rank is
shifted up or down in value as required to give a zero PSU value to which ever
sample is chosen
to be the zero-base standard. The other samples then have plus or minus values
as determined by
their relative grades with respect to the zero base standard. The number of
panel tests performed
and averaged is such that about 0.2 PSU represents a significant difference in
subjectively
perceived softness.
E. Calculations
Geometric Mean
The values for geometric mean (GM) are determined by taking the square root of
the
product of the desired measured values. By way of non-limiting example, the GM
of D x L is
the square root of the product of D x L (dust x lint). Similarly, the GM of D
x TT is the square
root of the product of D x TT (dust x total tensile)
All results are in units of grams/inch. For purposes of this specification,
the tensile
strength should be converted into a"specific total tensile strength" defined
as the sum of the
tensile strength measured in the machine and cross machine directions, divided
by the basis
weight, and corrected in units to a value in meters.
Examples
Any suitable process for making fibrous structures, such as tissue paper
products, known
in the art may be used to form a fibrous web having substantially machine
direction oriented
linear channels in the present invention.
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The following Example illustrates a non-limiting example for a preparation of
a sanitary
tissue product comprising a fibrous structure according to the present
invention on a pilot-scale
Fourdrinier fibrous structure making machine.
An aqueous slurry of Eucalyptus (Aracruz Brazilian bleached hardwood kraft
pulp) pulp
fibers is prepared at about 3% fiber by weight using a conventional repulper.
This slurry is
passed through a stock pipe toward a multi-layered, three-chambered headbox of
a Fourdrinier
wet laid papermaking machine.
Separately, an aqueous slurry of Eucalyptus fibers is prepared at about 3% by
weight
using a conventional re-pulper. This slurry is passed through a stock pipe
toward the multi-
layered, three-chambered headbox of a Fourdrinier wet laid papermaking
machine.
Finally, an aqueous slurry of NSK (Northern Softwood Kraft) fibers of about 3%
by
weight is made up using a conventional re-pulper. This slurry is passed
through a stock pipe
toward the multi-layered, three-chambered headbox of a Fourdrinier wet laid
papermaking
machine.
In order to impart temporary wet strength to the finished fibrous structure, a
1%
dispersion of temporary wet strengthening additive (e.g., Parez 750) is
prepared and is added to
the NSK fiber stock pipe at a rate of about 3.0 lbs. per ton (1.36 Kg/908Kg)
of total fiber. The
temporary wet strength agent is also added to each of the Eucalyptus thick
stock pipe at a rate of
about 0.5 lbs. per ton (0.23Kg/908Kg) of total fiber. The absorption of the
temporary wet
strengthening additive is enhanced by passing the treated slurry through an in-
line mixer. The
NSK and eucalyptus fiber slurries are diluted with white water at the inlet of
their respective fan
pumps to consistencies of about 0.15% based on the total weight of the
respective slurries. The
three slurries are spread over the width of the Fourdrinier, but maintained as
separate streams in
the multi-chambered headbox until they are deposited onto a forming wire on
the Fourdrinier.
The fibrous structure making machine has a layered headbox having a top
chamber, a
center chamber, and a bottom chamber. The eucalyptus fiber slurry is pumped
through the top
headbox chamber, the eucalyptus fiber slurry is pumped through the bottom
headbox chamber
(i.e. the chamber feeding directly onto the forming wire) and, finally, the
NSK fiber slurry is
pumped through the center headbox chamber and delivered in superposed relation
onto the
Fourdrinier wire to form thereon a three-layer embryonic web, of which about
33% of the top
side is made up of the eucalyptus blended fibers, 33% is made of the
eucalyptus fibers on the
bootom side and 33% is made up of the NSK fibers in the center. Dewatering
occurs through
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the Fourdrinier wire and is assisted by a deflector and vacuum boxes. The
Fourdrinier wire is of
a 5-shed, satin weave configuration having 87 machine-direction and 76 cross-
machine-direction
monofilaments per inch, respectively. The speed of the Fourdrinier wire is
about 750 feet (228.6
m) per minute (fpm).
The embryonic wet web is transferred from the Fourdrinier wire, at a fiber
consistency of
about 15% at the point of transfer, to a patterned drying fabric. The speed of
the patterned
drying fabric is the same as the speed of the Fourdrinier wire. The drying
fabric is designed to
yield a pattern of substantially machine direction oriented linear channels
having a continuous
network of high density (knuckle) areas. This drying fabric is formed by
casting an impervious
resin surface onto a fiber mesh supporting fabric. The supporting fabric is a
45 x 52 filament,
dual layer mesh. The thickness of the resin cast is about 11 mils above the
supporting fabric.
Further de-watering is accomplished by vacuum assisted drainage until the web
has a
fiber consistency of about 20% to 30%.
While remaining in contact with the patterned drying fabric, the web is pre-
dried by air
blow-through pre-dryers to a fiber consistency of about 65% by weight.
After the pre-dryers, the semi-dry web is transferred to the Yankee dryer and
adhered to
the surface of the Yankee dryer with a sprayed creping adhesive. The creping
adhesive is an
aqueous dispersion with the actives consisting of about 22% polyvinyl alcohol,
about 11%
CREPETROL A3025, and about 67% CREPETROL R6390. CREPETROL A3025 and
CREPETROL R6390 are commercially available from Hercules Incorporated of
Wilmington,
Del. The creping adhesive is delivered to the Yankee surface at a rate of
about 0.15 Io adhesive
solids based on the dry weight of the web. The fiber consistency is increased
to about 97%
before the web is dry-creped from the Yankee with a doctor blade.
The doctor blade has a bevel angle of about 25 degrees and is positioned with
respect to
the Yankee dryer to provide an impact angle of about 81 degrees. The Yankee
dryer is operated
at a temperature of about 350 F (177 C) and a speed of about 750 fpm (228.6
m/min). The
fibrous structure is wound in a roll using a surface driven reel drum having a
surface speed of
about 656 fpm (199.95 m/min). The fibrous structure may be subsequently
converted into a
two-ply sanitary tissue product having a basis weight of about 25.5 g/m2. For
each ply, the outer
layer having the eucalyptus fiber furnish is oriented toward the outside in
order to form the
consumer facing surfaces of the two-ply sanitary tissue product. The resulting
sanitary tissue
paper product is very soft, flexible and absorbent.
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Chemical Softening Agent Preparation
By way of non-limiting example, Karlinal (a quaternary ammonium compound that
is a
blend of cationic and nonionic surfactants in water (CAS #27344-41-8) and
available from
Calvary Industries 9233 Seward Road, Fairfield, Ohio) was provided at three
specific percent
active levels (0.25%, 0.30%, and 0.45%) in order to determine the optimum
percent active level
to achieve the target parametric variables. Karlinal at 0.45% active is
generally the neat Karlinal
as provided by the supplier. This solution was applied directly to the web
substrate as provided
by the supplier. Karlinal at 0.25% and 0.30% were prepared by dilution with
water of the neat
Karlinal solution. Water was added to the neat Karlinal in the following ratio
to achieve the
0.25% active level: neat Karlinal - 6250 ml, water - 4750 ml. Water was added
to the neat
Karlinal in the following ratio to achieve the 0.30% active level: neat
Karlinal - 7500 ml, water
- 3500 ml. After the specific ratios of neat Karlinal and water were combined,
the resulting
solution was mixed by hand.
Application Methods
Extrusion coating (also known to those of skill in the art as slot die
coating) is a liquid
application method where a fluid, such as the Karlinal solution prepared
supra, is forced through
a die slot via a metering pump. The fluid is then transferred to a moving web
through contact
with the slot. Fluid add-on rates are controlled by varying the metering pump
delivery rate.
Spray application is accomplished by the use of a spray header consisting of
seven
individual spray nozzles. Fluid, such as the Karlinal solution prepared supra,
is forced through a
manifold to each of the seven spray nozzles via a metering pump. Fluid flow
out of the spray
nozzles is aided by a steady flow of air. Additional streams of air are
directed at the stream of
fluid from the spray nozzle tips to atomize the fluid into small droplets.
Fluid add-on rates are
controlled by varying the metering pump delivery rate. Distribution of the
small droplets of fluid
across the web is controlled by varying the volume of air atomizing the fluid,
and by varying the
distance of the spray header to the web.
Tissue products produced by the above methods were measured for the parametric
attributes discussed above. The resulting directly measured values and any
resulting calculated
values are provided in Tables 2 and 3 hereto.
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Table 2. Raw Dust, Lint, Total Tensile, Geometric Mean (Dust x Lint, and
Geometric Mean
(Dust x Total Tensile) vs. Percent Solids - slot extrusion application
Solids Dust Lint Dust/Lint Total GM (D x L) GM (D x TT)
Application (# particles) Tensile
% (g/in)
0.25 4337 5.69 762.2 498.2 157.1 1470
0.25 4286 5.84 733.9 521.7 157.8 1495
0.30 3907 6.03 647.9 485.3 153.8 1377
0.45 4319 5.83 740.8 529.2 158.1 1512
0.45 4631 5.80 798.4 467.6 164.6 1471
Table 3. Raw Dust, Lint, Total Tensile, Geometric Mean (Dust x Lint, and
Geometric Mean
(Dust x Total Tensile) vs. Percent Solids - spray application
Solids Dust Lint Dust/Lint Total GM (D x L) GM (D x TT)
Application (# particles) Tensile
% (g/in)
0.25 4581 6.20 738.9 476.6 169.0 1478
0.25 4720 6.52 723.4 446.1 176.5 1451
0.30 4562 6.44 708.4 484.9 171.7 1487
0.30 4281 6.61 647.7 451.8 169.1 1391
0.45 4893 6.08 804.8 491.6 172.7 1551
0.45 4135 5.81 711.7 469.6 155.6 1394
The soft tissue paper having a substantively affixed chemical softening agent
extruded
thereon of the present invention preferably has the substantively affixed
chemical softening
agent extruded thereupon at a concentration (solids %) ranging from about
0.45% to about
0.23%, more preferably ranging from about 0.40% to about 0.29%, and most
preferably at about
0.34%. The soft tissue paper having a substantively affixed chemical softening
agent extruded
thereon of the present invention preferably has a dust value of less than
about 4557, more
preferably ranges from about 4557 to about 3797, even more preferably from
about 3956 to
about 3797. Based upon the information provided in Tables 1 and 2, supra, the
application of a
substantively affixed softening agent to paper products of the present
invention by extrusion of
the chemical softening agent upon the surface of the paper product preferably
provides a dust
value that approximately satisfies the equation:
Dust = 4069.8 - (805.4 x solids %) + (59446.3 x (solids % - 0.336)2).
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The soft tissue paper having a substantively affixed chemical softening agent
extruded
thereon of the present invention preferably has the substantively affixed
chemical softening
agent sprayed thereupon at a concentration (solids %) ranging from about 0.45%
to about
0.25%, more preferably ranging from about 0.40% to about 0.30%, and most
preferably at about
0.35%. The soft tissue paper having a substantively affixed chemical softening
agent sprayed
thereon of the present invention preferably has a dust value of less than
about 4543, more
preferably ranges from about 4543 to about 4318, even more preferably from
about 4378 to
about 4318. Based upon the information provided in Tables 1 and 2, supra, the
application of a
substantively affixed softening agent to paper products of the present
invention by spray
application of the chemical softening agent upon the surface of the paper
product preferably
provides a dust value that approximately satisfies the equation:
Dust = 4803.9 - (1388.9 x solids %) + (25974.1 x (solids % - 0.336)2).
The soft tissue paper having a substantively affixed chemical softening agent
extruded
thereon of the present invention preferably has a dust/raw lint value of less
than about 808, more
preferably ranges from about 808 to about 618, even more preferably from about
770 to about
618, yet more preferably ranging from about 671 to about 618, and most
preferably ranging
from about 651 to about 618. Based upon the information provided in Tables 1
and 2, supra, the
application of a substantively affixed softening agent to paper products of
the present invention
by extrusion of the chemical softening agent upon the surface of the paper
product preferably
provides a value of dust per raw lint that approximately satisfies the
equation:
Dust/Raw Lint = 712.2 - (276.4 x solids %) + (14080.9 x (solids % - 0.336)2).
The soft tissue paper having a substantively affixed chemical softening agent
sprayed
thereon of the present invention preferably has a dust/raw lint value of less
than about 758, more
preferably ranges from about 758 to about 665, even more preferably ranging
from about 731 to
about 665, yet more preferably ranging from about 691 to about 665, and most
preferably
ranging from about 678 to about 665. Based upon the information provided in
Tables 1 and 2,
supra, the application of a substantively affixed softening agent to paper
products of the present
invention by spray application of the chemical softening agent upon the
surface of the paper
product preferably provides a value of dust per raw lint that approximately
satisfies the equation:
Dust/Raw Lint = 692.6 - (83.9 x solids %) + (8010.3 x (solids % - 0.336)2).
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The soft tissue paper having a substantively affixed chemical softening agent
extruded
thereon of the present invention preferably has a geometric mean dust x total
tensile (GM DxTT)
value of less than about 1492, more preferably ranges from about 1492 to about
1343, even
more preferably from about 1483 to about 1343, yet more preferably ranging
from about 1381 to
about 1343, and most preferably ranging from about 1377 to about 1343. Based
upon the
information provided in Tables 1 and 2, supra, the application of a
substantively affixed
softening agent to paper products of the present invention by extrusion of the
chemical softening
agent upon the surface of the paper product preferably provides a geometric
mean of dust
multiplied by total tensile strength value that approximately satisfies the
equation:
GM DxTT = 1462.2 - (347.7 x solids %) + (14399.8 x (solids % - 0.336)2).
The soft tissue paper having a substantively affixed chemical softening agent
sprayed
thereon of the present invention preferably has a geometric mean dust x total
tensile (GM DxTT)
value of less than about 1480, more preferably ranges from about 1480 to about
1432, even
more preferably ranging from about 1472 to about 1432, yet more preferably
ranging from about
1445 to about 1432, and most preferably ranging from about 1441 to about 1432.
Based upon
the information provided in Tables 1 and 2, supra, the application of a
substantively affixed
softening agent to paper products of the present invention by spray
application of the softening
agent upon the surface of the paper product preferably provides a geometric
mean of dust
multiplied by total tensile strength value that approximately satisfies the
equation:
GM DxTT = 1452.1 - (59.4 x solids %) + (3635.0 x (solids % - 0.336)2).
The soft tissue paper having a substantively affixed chemical softening agent
extruded
thereon of the present invention preferably has a geometric mean dust x lint
(GM DxL) value of
less than about 163, more preferably ranges from about 163 to about 153, even
more preferably
from about 161 to about 153, yet more preferably ranging from about 156 to
about 153, and
most preferably ranging from about 155 to about 153. Based upon the
information provided in
Tables 1 and 2, supra, the application of a substantively affixed softening
agent to paper
products of the present invention by extrusion of the softening agent upon the
surface of the
paper product preferably provides a geometric mean of dust multiplied by lint
value that
approximately satisfies the equation:
CA 02686724 2009-10-29
WO 2008/135900 PCT/IB2008/051642
36
GM DxL = 152.2 - (2.44 x solids %) + (620.9 x (solids % - 0.336)2).
The dimensions and values disclosed herein are not to be understood as being
strictly
limited to the exact dimension and values recited. Instead, unless otherwise
specified, each such
dimension and/or value is intended to mean both the recited dimension and/or
value and a
functionally equivalent range surrounding that dimension nand/or value. For
example, a
dimension disclosed as "40 mm" is intended to mean "about 40 mm".
All documents cited in the Detailed Description of the Invention are, in
relevant part,
incorporated herein by reference; the citation of any document is not to be
construed as an
admission that it is prior art with respect to the present invention. To the
extent that any
meaning or definition of a term in this document conflicts with any meaning or
definition of the
same term in a document incorporated by reference, the meaning or definition
assigned to that
term in this document shall govern.
While particular embodiments of the present invention have been illustrated
and
described, it would be obvious to those skilled in the art that various other
changes and
modifications can be made without departing from the spirit and scope of the
invention. It is
therefore intended to cover in the appended claims all such changes and
modifications that are
within the scope of this invention.
