Note: Descriptions are shown in the official language in which they were submitted.
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HIGHLY SUBSTANTIVE SOFT TISSUE
Backgiround of the Invention
Absorbent paper products such as paper towels, facial tissues and
other similar products are designed to include several important
properties. For example, the products should have good bulk, a soft feel
and should be highly absorbent. The product should also have good
strength, even when wet, and should resist tearing. Unfortunately, it is
very difficult to produce a high strength paper product that is also soft.
Usually, when steps are taken to increase one property of the product,
other characteristics of the product are adversely affected.
For instance, strength is typically increased by the addition of
certain strength or bonding agents to the product. Although the strength
of the tissue product is increased by such bonding agents, the resulting
tissue product is generally not soft. As a result, various softening agents
can be applied to the tissue product to reduce fiber bonding within the
paper product and thereby increase softness.
However, by reducing fiber bonding with a softening agent, the
strength of the tissue product is also significantly reduced. In particular,
when applied, softening agents often cause excessive "debonding" and
compete with conventional strength agents for bonding sites. As such,
most tissues can only accommodate limited amounts of a softening agent.
Moreover, even when applied at such limited amounts, the softening
agent can nevertheless result in a much weaker tissue product due to the
displacement of some of the bonding agent from the bonding sites. This
weaker tissue product can exhibit substantial amounts of lint and slough
production.
As such, a need currently exists for a tissue product that is soft, but
also possesses sufficient strength. In particular, a need currently exists
for a tissue product that can be applied with a softening agent without
adversely affecting the strength characteristics of the tissue so that
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2
tearing, lint production, and/or slough is not significantly increased.
Summay of the Invention
The present invention is directed to providing a tissue made from a
multi-layered paper web having two outer layers. In general, the outer
layers) can be made from a variety of fibrous materials. For example, in
one embodiment, various cellulosic fibers, such as softwood fibers,
hardwood fibers, etc., can be utilized in the outer layer(s).
According to the present invention, the outer layers) are configured
to have an increased number of bonding sites to accommodate sufficient
amounts of more than one additive. A bonding site generally refers to
various substituents located on a fiber, such as hydroxy groups, that are
capable of bonding to an additive. To increase the number of bonding
sites, any of a variety of mechanisms can be utilized. In one embodiment,
the outer fayer(s) contains some high-average length fibers (i.e., generally
greater than about 1.2 mm) that are fibrillated. Fibrillation can provide an
increase in the surface area of a fiber, thereby providing an increased
number of sites for bonding to an additive, such as a bonding or softening
agent. In some embodiments, the high-average length fibers are
fibrillated to an extent such that the resulting fibers have a Canadian
Standard Freeness ("CSF") (TAPPI T227m-58) between about 400 to
about 800, and more particularly, between about 500 CSF to about 700
CSF.
In another embodiment, the outer layers) can also contain a blend
of high-average length fibers (fibrillated or un-fibrillated) and low-average
length fibers (i.e., generally less than about 1.2 mm). Similar to
fibrillation,
a blend of differently sized fibers can also provide an increased number of
bonding sites in accordance with the present invention. When utilized,
low-average length fibers can generally be incorporated into the outer
layers) in any desired amount. Typically, a fiber blend used in an outer
layer of the present invention contains about 50% to about 95% by weight
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3
of low-average length fibers, and more particularly between about 60% to
about 90%.
By providing an increased number of bonding sites, various
additives, such as bonding and softening agents, can be applied to the
outer layers) of a tissue of the present invention without substantially
competing with each other for the same bonding sites. As such, a tissue
of the present invention can be applied with higher levels of a softening
agent without adversely affecting the strength of the tissue and without
causing substantial lint and slough production. As used herein, the term
"slough" generally refers to the wearing away of any part of the tissue by
rubbing the tissue against a surface.
For instance, a tissue made according to the present invention can
be applied with a softening agent in an amount from about 1 kilogram per
metric ton of fiber weight (kg/MT) to about 60 kg per metric ton of fiber
weight, and more particularly between about 10 kg/MT to about 35 kg/MT,
without resulting in substantial lint or slough. Moreover, it has also been
discovered that the tissue can retain at least about 75% of the softening
agent, and more particularly between about 80% to about 96% of the
softening agent, without having substantial increases in slough or lint
production.
A tissue of the present invention can generally be formed according
to a variety of papermaking processes known in the art. In particular, any
process capable of forming a multi-layered paper web can be utilized in
the present invention. For example, a papermaking process of the
present invention can utilize creping, embossing, wet-pressing, through-
drying, through-dry creping, uncreped through-drying, double creping, as
well as other steps ih forming the multi-layered paper web.
Various features and aspects of the present invention are
discussed in greater detail below.
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Brief Description of the Drawings
A full and enabling disclosure of the present invention, including the
best mode thereof to one of ordinary skill in the art, is set forth more
particularly in the remainder of the specification, including reference to the
accompanying figures in which:
Figure 1 is a graphical representation of geometric tensile strength
(GMT) versus the add-on level of a softening agent for various
embodiments of the present invention in which the paper web comprises
fibers that have been fibrillated for 0 minutes, 6 minutes, and 12 minutes;
and
Figure 2 is a graphical representation of geometric tensile strength
(GMT) versus the add-on level of a softening agent for various
embodiments of the present invention in which the paper web comprises a
blend of eucalyptus fibers and "Longlac-19" fibers.
Repeat use of reference characters in the present specification and
drawings is intended to represent same or analogous features or
elements of the present invention.
Detailed Description of Representative Embodiments
Reference now will be made in detail to the embodiments of the
invention, one or more examples of which are set forth below. Each
example is provided by way of explanation of the invention, not limitation
of the invention. In fact, it will be apparent to those skilled in the art
that
various modifications and variations can be made in the present invention
without departing from the scope or spirit of the invention. For instance,
features illustrated or described as part of one embodiment, can be used
on another embodiment to yield a still further embodiment. Thus, it is
intended that the present invention cover such modifications and
variations as come within the scope of the appended claims and their
equivalents.
In general, the present invention is directed to tissues having
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improved softness and having smooth, low friction surfaces. Moreover, it
has been discovered that by producing a tissue having multiple layers in
accordance with the present invention, the outer layers) can have an
increased number of bonding sites. As.such, a tissue of the present
5 invention can not only exhibit improved softness, but also retain adequate
strength when either dry or wet. Furthermore, because the tissues can
retain adequate strength, they generally have low slough and do not
produce a substantial amount of lint when used.
As stated, tissues made according to the present invention can
generally be formed in a variety of ways. In particular, the tissue can be
formed into a single or multi-ply tissue, so long as the tissue contains
more than one layer. For example, in one embodiment of the present
invention, a single ply tissue can be formed from one multi-layered paper
web. In another embodiment, a three-ply tissue can be formed from three
single or multi-layered paper webs that are adhesively attached to each
other. Normally, the basis weight of a tissue made according to the
present invention is from about 10 grams per square meter to about 50
grams per square meter.
lNhen forming a tissue of the present invention, it is typically
desired that the tissue have at least three layers. For example, in one
embodiment, the tissue can include two outer layers surrounding an inner
layer. However, it should be understood that a tissue of the present
invention need not comprise three layers. In fact, any number of layers
can be utilized as long as the resulting tissue has at least two outer layers.
As stated, a tissue of the present invention typically includes two
outer layers that surround at least one inner layer. In general, an outer
and/or inner layer of the tissue can be formed from any of a variety of
materials. In particular, a variety of natural and/or synthetic fibers can be
used. For example, some suitable natural fibers can include, but are not
to, nonwoody fibers, such as abaca, sabai grass, milkweed floss fibers,
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pineapple leaf fibers; softwood fibers, such as northern and southern
softwood kraft fibers; hardwood fibers, such as eucalyptus, maple, birch,
aspen, and the like. In addition, furnishes including recycled fibers may
also be utilized. Moreover, some suitable synthetic fibers can include, but
are not limited to, hydrophilic synthetic fibers, such as rayon fibers and
ethylene vinyl alcohol copolymer fibers, as well as hydrophobic synthetic
fibers, such as polyolefin fibers.
In one embodiment, an outer and/or inner layer of the present
invention can contain fibers having a "high-average length". As used
herein, the phrase "high-average length" generally refers to fibers having
an average fiber length greater than about 1.2 mm, and usually from
about 1.5 mm to about 6 mm. Illustrative examples of suitable pulps
include southern pines, northern softwood kraft pulps, red cedar, hemlock,
black spruce, and mixtures thereof. Exemplary commercially available
long pulp fibers suitable for the present invention include those available
from Kimberly-Clark Corporation under the trade designations "Longlac-
19," "Coosa River-54," "Coosa River-56" and "Coosa River-57". For
example, in one embodiment, northern softwood kraft fibers can be used
to form the inner layer. Northern softwood kraft fibers typically have a
fiber length of about 1.8 mm to about 2.5 mm.
In some embodiments, fibers having a "low-average length" can
also be utilized in an inner and/or outer layer of the present invention. As
used herein, the phrase "low-average fiber length" refers to fibers having
an average fiber length of less than about 1.2 mm, usually from about 0.7
mm to about 1.2 mm. Examples of low-average length fibers can include
certain grades of virgin hardwood pulp and secondary (i.e., recycled) fiber
pulp from sources such as, for example, newsprint, reclaimed paperboard,
and office waste. One particular example of fibers having a low-average
length suitable for use in the present invention are hardwood fibers, such
as eucalyptus fibers, which generally average from about 0.8 mm to about
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7
1.2 mm in length. By utilizing fibers having a low average fiber length,
such as eucalyptus fibers, a layer of the present invention can be
imparted with certain beneficial properties. For instance, low-average
length fibers can provide uniform formation, increased softness, enhanced
brightness, as well as increased opacity. Moreover, low-average length
fibers, such as eucalyptus fibers, can also change the pore structure of
the paper, thereby greatly increasing the wicking ability of the paper web.
In order to strengthen the tissue, various bonding agents (e.g., wet-
strength or dry strength agents) can be applied in accordance with the
present invention. Particular bonding agents that may be used include
latex compositions, such as acrylates, vinyl acetates, vinyl chlorides, and
methacrylates. Some water soluble bonding agents may also be used
including polyacrylamides (e.g. glyoxylated polyacrylamides), polyvinyl
alcohols, and carboxymethyl cellulose. In one embodiment, the bonding
agent used in the present invention comprises an ethylene vinyl acetate
copolymer. In particular, the ethylene vinyl acetate copolymer can be
cross-linked with N-methyl acrylamide groups using an acid catalyst.
Suitable acid catalysts include ammonium chloride, citric acid, and malefic
acid.
Although not required, the bonding agent is generally applied to a
layer such that it does not cover the entire layer. In particular, because
the bonding agents can adversely affect the absorbency of a paper web, it
is generally desired to minimize the amount of bonding agent applied.
Thus, according to the present invention, the bonding agent is normally
applied to each side of a paper layer so as to cover from about 30% to
about 60% of the surface area of the web. More particularly, in most
applications, the bonding agent will cover from about 40% to about 50% of
the surface area of each side of a layer. The total amount of bonding
agent applied to each side of a layer is typically in the range of from about
4% to about 7% by weight, based upon the total weight of the layer. In
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other words, the bonding agent is applied to each side of the web at an
add on rate of about 2% to about 3.5% by weight. At these amounts, the
bonding agent can penetrate the paper layer from about 25% to about
40% of the total thickness of the web. In most applications, the bonding
agent should not penetrate over 50% of the layer but should at least
penetrate from about 10% to about 15% of the thickness of the layer.
In addition, the bonding agent can be applied to a layer in a
preselected pattern. In one embodiment, for instance, the bonding agent
can be applied in a reticular pattern, such that the pattern is
interconnected forming a net-like design on the surface. In an alternative
embodiment, however, the bonding agent can be applied to the web in a
pattern that represents a succession of boat-shaped dots. Applying the
bonding agent in discrete shapes, such as dots, may provide sufficient
strength to the layer without covering a substantial portion of the surface
area. In some embodiments, the pattern applied to each side of the layer
is compressed such that the dots are small and are arranged close
together.
Although the application of bonding agents can vastly improve
some properties of the tissue, they can also have an adverse affect on
other properties. For instance, bonding agents can significantly improve
strength and tear resistance, but can undesirably decrease the softness of
the tissue.
As such, a tissue of the present invention can be treated with a
chemical debonding or "softening" agent to impart a "soft feel" to the
tissue product. Some softening agents are also believed to act as
lubricants or friction reducers. Generally speaking, a softening agent can
be added to the fiber slurry during the pulping process or can be added
directly into the head box. Moreover, if desired, a softening agent can
also be applied at other stages of the wet-end of a papermaking process
or applied directly onto the outer layers) of a dried tissue sheet. For
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instance, in one embodiment, discrete surface deposits of the softening
agent can be applied to the tissue, as described in U.S. Patent No.
5,814,188 to Vinson, et al., which is incorporated herein in its entirety by
reference thereto.
Any material having an affinity to fibers and that is capable of
enhancing the soft feel of a tissue product can generally be used as a
softening agent in the present invention. For instance, the softening
agents of the present invention can be cationic, amphoteric, and can be a
variety of combinations thereof, to facilitate bonding to the fibers of a
tissue layer. Moreover, various non-ionic softening agents can also be
utilized, particularly when used in conjunction with cationic and/or
amphoteric softening agents. Examples of suitable softening agents can
include, but are not limited to, quaternary ammonium compounds,
imidazolinium compounds, bis-imidazolinium compounds, diquaternary
ammonium compounds, polyquaternary ammonium compounds,
phospholipid deriviatives, polydimethylsiloxanes and related cationic and
non-ionic silicone compounds, fatty & carboxylic acid derivatives, mono-
and polysaccharide derivatives, pofyhydroxy hydrocarbons, etc.
Some specific examples of suitable softening agents are given
below:
1. Quaternary ammonium compounds having the following basic
structure:
R1
~
+
i,,, x_
-
R4 RZ
R3
Wherein
X= halide, methyl sulfate, ethyl sulfate, lactate, or other compatible
counterion;
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R1 can be hydrogen, C1 - C6 alkyl or hydroxyalkyl; and
R2, R3, R4 can be the same or different, any linear or branched,
saturated or unsasturated, substituted or non-substituted, with or without
ethoxylation, with or without propoxylation, aliphatic hydrocarbon moiety
5 of greater than 8 carbon chain length, preferably between 8 - 30 carbon
chain length;
or
R1
R4 - ~ Ra X_
R3 J
Wherein
X= halide, methyl sulfate, ethyl sulfate, lactate, or other compatible
counterion;
R1, R2 can be the same or different, hydrogen, C1 - C6 alkyl or
hydroxyalkyl; or R1 can be hydrogen, C1 - C6 alkyl or hydroxyalkyl;
R2 can be benzyl or epoxy; and
R3, R4 can be the same or different, any linear or branched, saturated or
unsasturated, substituted or non-substituted, with or without ethoxylation,
with or without propoxylation, aliphatic hydrocarbon moiety of greater
than 8 carbon chain length, preferably between 8 - 30 carbon chain
length;
or
R1
- _
R4 ~ R2 X
R3
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Wherein
X= halide, methyl sulfate, ethyl sulfate, lactate, or other compatible
counterion;
R1, R2, R3 can be the same or different, hydrogen, C1 - C6 alkyl or
hydroxyalkyl; R4. can be any linear or branched, saturated or
unsasturated, substituted or non-substituted, with or without ethoxylation,
with or without propoxylation, aliphatic hydrocarbon moiety of greater
than 8 carbon chain length, preferably between 8 - 30 carbon chain
length;
2. Quaternary ammonium compounds having the following basic
structure:
R1
R4 -~~ R2 ~_
R3
Wherein
X= halide, methyl sulfate, ethyl sulfate, lactate, or other compatible
counterion;
R1, R2, R3 can be the same or different, hydrogen, C1 - C6 alkyl or
hydroxyalkyl; and
R4 are selected from any of the following two groups:
O H O
II t
(CHZ)m - O - C- Rs / (CH2)m - N- C- Rs
- (CH2)n - (CH~)n
\ (CHZ)P - O - C- R6 \ (CH2)P -N - C- R6
0l ~ I~
H O
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n=2-6;
m=0-6
p=1-6; and
R5, R6 can be the same or different, any linear or
branched, saturated or unsasturated, substituted or non-
substituted, with or without ethoxylation, with or without
propoxylation, aliphatic hydrocarbon moiety of greater than
8 carbon chain length, preferably between 8 - 30 carbon
chain length
or
R1
R4 -~ R2 X_
R3
Wherein
X= halide, methyl sulfate, ethyl sulfate, lactate, or other compatible
counterion;
R1, R2 can be the same or different, hydrogen, C1 - C6 alkyl or
hydroxyalkyl; and
R3, R4 can be selected in any combination from the following two
groups:
O H O
II I
- (CH2)m - O - C- Rs - (CH2)m - N- C- Rs
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m=2-6; and
R5 can be any linear or branched, saturated or
unsasturated, substituted or non-substituted, with or
without ethoxylation, with or without propoxylation,
aliphatic hydrocarbon moiety of greater than 8 carbon
chain length, preferably between 8 - 30 carbon chain
length.
3. Quaternary ammonium compounds having the following basic
structure:
+/CZH\
R- H N' 'O X-
\'C~/H/4
wherein
X= halide, methyl sulfate, ethyl sulfate, lactate, or other compatible
counterion;
R is selected from the following group:
H O
I
- (CH2)m - I~- C- RS
m=2-6; and
R5 can be any linear or branched, saturated or
unsaturated, substituted or non-substituted, with or without
ethoxylation, with or without propoxylation, aliphatic
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hydrocarbon moiety of greater than 8 carbon chain length,
preferably between 8 - 30 carbon chain length.
4. Imidazolinium compounds having the following basic structures:
IHs
N+
RI / X_
N
Rz
wherein
X=halide, methyl sulfate, ethyl sulfate, lactate, or other compatible
counterion;
R1 can be any linear or branched, saturated or unsaturated, substituted
or non-substituted, with or without ethoxylation, with or without
propoxylation, aliphatic hydrocarbon moiety of greater than 8 carbon
chain length, preferably between 8 - 30 carbon chain length; and
R2 can be selected from any of the following two groups:
fl H 1l
- (CI~z)m - O - C- Rs - (CHZ)m - N- C_ Rs
m=2-6; and
R5 can be any linear or branched, saturated or
unsaturated, substituted or non-substituted, with or without
ethoxylation, with or without propoxylation, aliphatic
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hydrocarbon moiety of greater than 8 carbon chain length,
preferably between 8 - 30 carbon chain length.
5
5. Bis-imidazolinium compounds having the following basic structure:
H
2
C ~ CHs
CH~N~ CHz H2C~N~
-N - (CHz)n - N-C\
R1 Rz
Wherein
X=halide, methyl sulfate, ethyl sulfate, lactate, or other compatible
counterion;
R1, R2 can be the same or different, aliphatic hydrocarbons, linear or
branched, saturated or unsaturated, substituted or non-substituted, with
or without ethoxylation, with or without propoxylation, preferably C8
C30; or R1, R2 can be selected in any combination from any of the
following two groups:
H O O
I!
- (CH2)m -1V- C- Rs - (CI I2)m - O - C- Rs
m=2-6; and
R5 can be any linear or branched, saturated or
unsaturated, substituted or non-substituted, with or without
ethoxylation, with or without propoxylation, aliphatic
hydrocarbon moiety of greater than 8 carbon chain length,
preferably between 8 - 30 carbon chain length.
6. Diquaternary ammonium compounds having the following basic
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structure
++
1 ~4
R2- ~ - (CH2)n- ~ - RS 2X-
R3 R6
Wherein
X=halide, methylsuffate, ethylsulfate or other compatible counterion;
n=2 - 8;
R, R4 may be the same or different, are H, CH3, or (CHZ)mOH where
m=1-4;
R2 ,R3 ,R5 ,R6 may be the same or different, are from the following
groups:
(i). --(CH2)P OH, where p=1-6;
or
(ii). O
- (CZH4O)q -C- R
where q=1-10, R=aliphatic, C8 - C30, saturated or
unsaturated, normal or branched;
or
(I
- (CH2)r -N- C- R.
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where r=1-10, R'=aliphatic, C8 - C30, saturated or
unsaturated, normal or branched;
or
(iv).
QH
-(CHa)s - CI H -(CH~)t- R"
where s=1-10, t=1-4, R"=aliphatic, C8 - C30, saturated or
unsaturated, normal or branched.
7. Polyquaternary ammonium compounds having the following basic
structure:
1 ~4
R2-N (CH2)n- + RS (m+1) X'
R3 R6
m
20.
Wherein
X=halide, methylsulfate, ethylsulfate or other compatible counterion;
n=2 - 8;
m=1 or greater;
R2, R5 may be the same or different, are aliphatic, C8 - C30, saturated or
unsaturated, normal or branched;
or (CHZ)q--CHOH--R' where q=1-6, and R'= aliphatic, C8 - C30, saturated
or unsaturated, normal or branched;
or (CHZ)~ -O--R" where r=1-6, and R"= aliphatic, C8 - C30, saturated or
unsaturated, normal or branched; and
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R1 ,R4 ,R3 ,R6 may be the same or different, are H, CH3, or (CHZ)mOH
where m=1-6; or aliphatic, C8 - C30, saturated or unsaturated, normal or
branched.
8. Phospholipid Derivatives having the following basic structure:
(1 )
+ O
- ~ CH2CHOHCI~O P- (B)y + xA + a
-~ x
wherein,
x= 1 - 3;
x+Y=3~
a=0 - 2;
B=O- or OM;
A=an anion;
M=a cation;
R, R1, R2 can be the same or different, are alkyl, substituted
alkyl, alkyl aryl or alkenyl groups of up to 30 carbon atoms;
or
(2)
II + O
R -N- CH CHOHCH O IP- (B)y + xA + aM
2 2
R2 x
wherein
x=1-3;
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x+y=3;
a=0 - 2;
B=O- or OM;
A=an anion;
M=a cation;
R1, R2 can be the same or different, are alkyl, hydroxyalkyl,
carboxyalkyl, C1 - C6, or propoxyalkylene, C1 - C10; or R1, R2 and the
nitrogen
they are attached to may represent an N-heterocycle; and
R has the following structure:
t
- (CH2)m - N- C- Rs
wherein
m=2 -6;
R4 = hydrogen or alkyl, hydroxyalkyl or alkenyl of up to 6
carbons, or cycloalkyl of up to 6 carbons or
polyoxyalkylene of up to carbons; and
R5 = alkyl, alkenyl, alkoxy or hydroxyalkyl, C5 - C30, or
aryl or alkylaryl of up to C30.
or
(3)
++
i1 o
+ N~ R. 2A_
R -N- CH2CHOHCH20 - ~~ OCHZCHOHCHz -
Rz OM Rz
wherein
A=an anion;
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M=a cation;
R, R1, R2 can be the same or different, are alkyl, substituted alkyl, alkyl
aryl
or alkenyl groups of up to 30 carbons; and
R' has the following structure:
5 R4 O
I
- (CHa)m - N- C- R6
wherein
m=2 -6;
10 R4=hydrogen or alkyl, hydroxyalkyl or alkenyl of up to 6
carbons, or cycloalkyl of up to 6 carbons or
polyoxyalkylene of up to carbons; and
R6 has the following structure:
~= o
N
IH3 IH3 ( ~ H2)n ~ Hs
CH3 -li-O ~i-O 1i-0 li-CH3
CH3 CH3 ~ CH3 CH3
p q
where
n>_3;
p= 1-1000; and
q= 1-25.
9. Polydimethylsiloxanes and related silicone compounds having the
following structures:
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(1)
CH3 CH3 CH3 CH3 ++
R Si Z Si O Si Z Si R 2X-
CH3 CH3 CH3 CH3
Wherein
R=alkyl or aliphatic hydrocarbons, C8 - C30, normal or branched, saturated
or unsaturated, substituted or unsubstituted;
z= -- alkyl -- O -- alkyl --, alkyl groups having at least 1 carbon;
x=alkoxy, halide, methyl sulfate, ethyl sulfate, lactate or other compatible
counterion; and
n=1 to 50;
or
(2)
Hs ~ H3 ~ H3 ~ H3 I H3
CH3 -li -Si O- Ii O- Ii O- li-CH3
CH3 Rl ~ Rz ( IHz)a CH3
z
(~ CzHa)b
(~~.Ha)d
~CH2CHOHCI~
IR
wherein
x= 0 to 1000;
x, y, z = 1 to 1000;
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R1, R2 can be the same or different, are alkyl or hydroxyalkyl, C1 - C20
or phenyl;
a= 1-4;
b,c,d= 0-20;
Y=halide, methyl sulfate, ethyl sulfate or other compatible counterion; and
R can be selected from among the following four groups:
R3 -~ ~ Rs
R4
where
R3, R4, R5 can be the same or different, are selected from
hydroxyalkyl or alkyl group, C1- C4; or aliphatic group, C8 - C30,
normal or branched, saturated or unsaturated, substituted or
unsubstituted;
R6 ~ - OHa)n -N- C- R~
R7
where, R6 = hydroxyalkyl or alkyl C1-C6; or
R6, R7, R8 can be the same or different, are selected from
aliphatic group, C8 - C30, normal or branched, saturated or
unsaturated, substituted or unsubstituted; and
n=1 -6;
or
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23
where
R6, R7 can be the same or different, are alkyl or hydroxyalkyl, C1
- C6;
R8=aliphatic, C8 - C30, normal or branched, saturated or
unsaturated, substituted or unsubstituted; and
n=1 -6;
or
where
R6-hydroxyalkyl or alkyl, C1 - C6;
n=1 -6;
R7=
II
- (CH2)m-N- C- R9
m=1 - 6; and
. R9= aliphatic, C8 - C30, normal or branched, saturated or
unsaturated, substituted or unsubstituted;
or
where
R6=hydroxyalkyl or alkyl, C1 - C6;
R7=
O
II
- (CH2)m=C- O -R9
m'=1 - 6; and
R9= aliphatic, C8 - C30, normal or branched, saturated or
unsaturated, substituted or unsubstituted;
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24
N+
N
Ri i
where
R10, R11 can be the same or different, are selected from aliphatic
group, C8 - C30, normal or branched, saturated or unsaturated,
substituted or unsubstituted;
or
R11=
where
H II
- (CH~)o -N-C-Riz
0=1 - 6; and
R12= aliphatic, C8 - C30, normal or branched, saturated or
unsaturated, substituted or unsubstituted.
(iv)
'+
Ri2 ~ - Ri4
RI3
wherein
R12, R13=C1 - C6, alkyl or hydroxyalkyl;
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R14= --(CHZ)P -- C --O --R15;
P=1 - 6; and
R15= aliphatic, C8 - C30, normal or branched, saturated or
unsaturated, substituted or unsubstituted;
5
or
R12 = C1 - C6 alkyl or hydroxyalkyl;
R13, R14 can be the same or different, and selected from the
10 following two groups:
O
II
/ (CH2)r - O - C- Ri 6
15 - (CHa)q
(CHa)s -O-C- Ri7
0I
O
or
H O
I I
/ (CH2)r° -N-C-R18
- (CHa)q'
(CHa)s' -N II Ri9
H O
where
q~ G'=1 - 6~
r, r', s, s'=0 - 6; and
R16, R17, R18, R19 can be the same or different,
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26
are aliphatic, C8 - C30, normal or branched,
saturated or unsaturated, substituted or
unsubstituted.
or
R12=R13=C1-C6 alkyl or hydroxyalkyl;
R14=
O
1o II
- (G~I2)m- O- C- R15
m = 1-6
R15 =C8=C30 aliphatic, normal or branched, saturated or
unsaturated, substituted or unsubsituted.
or
(3)
Hs ~H3 ~H3 I Hs
CH3 - ~ i- O Ii - O ~i - O $i - CH3
CH3 CH3 X C~CH3 Y CHs
~Hz
and R
IHs ~H3 IH3
R- (CHz)n-Si- O Ii - O ~i --(CHz)n -R
I
CH3 CH3 X CH3
and
H3 ~Hs ~ H3
R- (CHz)n-Si- O ~i - O $i - CH3
II
CH3 CH3 X CH3
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27
wherein
R=amine, carboxy, hydroxy or epoxy;
n>_3;
x=1 - 1000;
y=1 -25.
or
(4)
I H3 ~H3 ~H3 I H3
CHs -S i O-~ i O-~ i O ~i-CHs
-
CHs CHs (CHZ)a CHs
n ~ m
H2
~HOH
~Hz
CHs ~+ CHs
~H2
COO-
Wherein
n=1 - 1000; and
m=1 - 100.
or
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(5)
H3 ~H3 ~H3 ~ H3
CH3 -Si O-~i O-~i O-~i-CH3
CH3 CH3 CH3
x ~ y
(~hzCH20)m
(CH2CHa0)n -Rl
CI H3
Wherein
R=alkyl, C1 - C6;
R1=acetate or hydroxy;
n=1 - 100;
m=1 - 100;
x=1 - 1000; and
y=1 - 50.
or
(6)
CH3 ~ i - RxR'y - p - ~ i - CH3
CH3 CH3
wherein
x=1 - 1000;
y=1 - 100;
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R' has the following structure:
H3
O- 1i-
CH3
and R is selected from the following two groups:
(i).
Hs
o - Ii I,_
(CI z)a
0
(~zH40)b
(~3H6o)C
(CzHao)d
CH3
Ii
CHz ~ ~ (CHz)m - N- C- R"
CH3
where
Y=halide, methyl sulfate, ethyl sulfate or other compatible
counterion;
R" = aliphatic, C8 - C30, saturated or unsaturated, normal
or branched;
a,e = 1-4;
b, c, d = 0-20; and b+c+d>_1.
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or
H3
O- Ii
5 ( IHz)a
(~ZHaO)b
(CraHsO)e
(CZH40)d
10 O ~ i H3 H O
I
O HII1~ (CHZ)e - N-C- R"
CH3
where
15 R" = aliphatic, C8 - C30, saturated or unsaturated, normal
or branched;
a,e = 1-4;
b, c, d = 0-20; and
b+c+d>_1.
10. Fatty and carboxylic acid derivatives having the following structures:
RD(C3HsC)x(CHaCH20)y -(CH2)m-C- p- (CH2CH20)zR'
wherein
R= alkyl or aliphatic, normal or branched, saturated or unsaturated, C8 -
C30;
R'=alkyl, normal or branched, C1 - C24 or aliphatic, normal or branched,
saturated or unsaturated, C8 - C30;
m=0 - 100, more specifically 0 - 10, and still more specifically 1 - 6;
x=0 - 500, more specifically 0 - 20, and still more specifically 0 - 10;
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31
y=2 - 1000, more specifically 2 - 200 and still more specifically 6 -100;
z=0 - 1000, more specifically 0 - 200, and still more specifically 0 - 100.
in addition to the softening agents mentioned specifically above,
any of a variety of other chemicals known to soften or lubricate a tissue
can also be used in accordance with the present invention. Examples of
such chemicals can include, but are not limited to, fatty dialkyl quaternary
amine salts, mono fatty alkyl tertiary amine salts, primary amine salts,
imidazoline quaternary salts, silicone quaternary salt and unsaturated fatty
alkyl amine salts. Other suitable chemicals include, long-fatty acid derived
compounds including esters, salts, soaps, and quaternary ammonium
compounds, polyols with hydrophobic and hydrophilic characteristics, etc.
Still other suitable softening agents are disclosed in U.S. Patent Nos.
5,529,665 to Kaun and 5,558,873 to Funk, et al., which are incorporated
herein in their entirety by reference thereto. In particular, Kaun discloses
the use of various cationic silicone compositions as softening agents.
One commercially available softening agent is available from the
Quaker Chemical Company of Conshohocken, Pennsylvania, under the
trade designation "Quaker 2008." The addition of certain softening agents
in the amount of, for example, 1 to 4 percent, by weight, of the composite
also appears to reduce the measured static and dynamic coefficients of
friction and improve the abrasion resistance of the continuous filament-
rich side of the composite fabric. In this embodiment, the softening agent
can be added to the fiber slurry in an amount from about 0.2% to about
1 % by weight, based on the total weight of fibers present within the slurry.
In one embodiment, the softening agent can be a quaternary lotion,
such as a quaternary silicone spray. For instance, the composition can
include a silicone quaternary ammonium chloride. One commercially
available silicone glycol quaternary ammonium chloride suitable for use in
the present invention is ABIL SW marketed by Goldschmidt Chemical
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32
Company of Essen, Germany. Quaternary silicone compositions can be
particularly useful as softening agents in the present application because
they bond with the cellulosic fibers contained within the base web. By
bonding to the cellulosic fibers, the composition does not transfer onto the
user's skin when the tissue product is used. In one embodiment, the
softening agent is applied to one side of the layer in an amount from
about 0.4% to aboufi 2% by weight and particularly from about 0.4% to
about 1.4% by weight, based upon the weight of the layer.
in an alternative embodiment, the softening agent can also contain
anti-microbial agents for destroying germs that come in contact with the
layer. For instance, one particular commercially available softening spray
having anti-microbial properties is DOW 5700 marketed by the Dow-
Corning Corporation of Midland, Michigan. DOW 5700 is a silicone
quaternary spray that contains anti-microbial agents. In a further
embodiment, the softening agent can also include a fragrance or odor
maskant. The fragrance can be added to the softening agent in order to
mask the smell of the silicone composition or can be added to give the
resulting tissue product a desired and aesthetic scent.
Besides the above mentioned materials, it should be understood
that any other additive, agent, or material can be added to a tissue of the
present invention, if desired. For example, various additives can be
applied to a tissue of the present invention to aid in retention of the
softening agent. Examples of such retention aids are described in U.S.
Patent No. 5,830,317 fio Vinson et al., which is incorporated herein in its
entirety by reference thereto.
Unfortunately, the use of even small amounts of a softening agent
in the tissue can sometimes cause excessive degradation of the web
surface(s), thereby resulting in significant increases in slough and lint
production. This degradation is believed to be at least partially due to the
propensity of the softening agent to compete with the bonding agent for
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33
"bonding sites" on an outer layer of a tissue. In particular, a softening
agent may occupy "bonding sites" normally utilized by the bonding agent.
As used herein, a "bonding site" generally refers to a substituent of a fiber
to which various materials can bond. For example, common bonding sites
for cellulosic fibers can include hydroxy substifiuents to which cationic
softening and bonding agents are attracted. Thus, although a softening
agent can provide a soft, lubricated surface feel, it can also cause surface
degradation by lessening the ability of the bonding agent to bond to the
fibers.
As such, in accordance with the present invention, various
mechanisms can be employed to allow the tissue to have a soft,
lubricated feel without resulting in substantial surface degradation, slough
and (int production. In particular, one or both of the outer layers of the
tissue can be appropriately configured to have an increased number of
bonding sites. It is believed that the increased number of bonding sites
can allow for bonding of the softening agent to the fibers without
significantly interFering with the bonding of the bonding agent to the fibers.
By providing such an increased number of bonding sites, it has
been discovered that the outer layers of a tissue can handle increased
loads of a softening agent without resulting in substantial losses in
strength. In fact, it has been discovered that a tissue produced according
to the present invention can be applied with a softening agent in an
amount from about 1 kilogram per metric ton of fiber weight (kg/MT) to
about 60 kg per metric ton of fiber weight, and more particularly between
about 10 kg/MT to about 35 kg/MT. Moreover, it has also been
discovered that the tissue can retain at least about 75% of the softening
agent, and more particularly between about 80% to about 96% of the
softening agent.
In accordance with the present invention, one or both of the outer
layers can comprise any of a variety of materials capable of providing a
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34
sufficient number of bonding sites to allow a soft, yet strong tissue to be
formed therefrom. In addition to providing increased bonding sites, the
fibers of the outer layers) can also prevent lint from escaping the center
of the tissue and further enhance the strength of the tissue.
In this regard, one embodiment of the present invention includes
the use of one or more outer layers that contain at least some fibers
having a "high-average length". As stated above, the phrase "high-
average length" generally refers to fibers having an average fiber length
greater than about 1.2 mm, and usually from about 1.5 mm to about 6
mm. When utilized, fibers having a high-average length can provide a
tissue product that is not only soft and strong, but also low in slough and
lint production. For instance, softwood fibers, such as northern and
southern softwood kraft fibers, are some examples of suitable high-
average length fibers that can be used in outer (ayer(s) of the present
invention.
In some embodiments, to further enhance the ability of such fibers
to be sufficiently soft and strong, the high-average length fibers can also
be fibrillated to increase the number of bonding sites available to the
softening agent and/or bonding agent. Fibrillation generally refers to the
random splitting of fibers into minute fibrous elements or fibrils. By
fibriliating a fiber, its surface area can, in some instances, be dramatically
increased so as to provide an increased number of bonding sites.
Fibrillation can be accomplished according to any of a variety of
well-known methods. For example, fibrillation can be accomplished
through mechanical agitation, such as described in U.S. Patent Nos.
4,608,292 to Lassen or 4,701,237 to Lassen, which are incorporated
herein in their entirety by reference thereto. Moreover, fibrillation can also
be accomplished through other methods, such as by contacting fihe fibers
with a fibrillation-inducing medium. For instance, U.S. Patent Nos.
5,759,926 to Pike et al., 5,895,710 to Sasse et al., and 5,935,883 to Pike,
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which are incorporated herein in their entirety by reference thereto,
describe a variety of fibrillation-inducing mediums that can be used in the
present invention, such as hot water, steam, air/steam mixtures, etc.
When the fibers are fibrillated, as described above, the extent of
5 fibrillation can generally vary. In fact, any amount of fibrillation can
provide at least some increase in the number of available bonding sites,
and thus provide increased strength and softness. Nevertheless, in most
embodiments, it is typically desired that the high-average length fibers are
fibrillated to an extent such that the resulting fibers have a Canadian
10 Standard Freeness ("CSF") (TAPPI T227m-58) between about 400 to
about 800, and more particularly, between about 500 CSF to about 700
CSF. Canadian Standard Freeness is generally a measurement of the
drainage properties of fibers as a result of refinement. For example, 800
CSF represents a relatively low amount of pulp refinement, while 400 CSF
15 represents a relatively high amount of pulp refinement.
In addition to, or in combination with, the use of fibrillated fibers,
fibers having a iow-average length can also be combined or blended with
fibers having a high-average length (fibrillated or un-fibrillated) to provide
the desired increase in the number of available bonding sites. For
20 example, in one embodiment, eucalyptus fibers having a low-average
length can be combined with softwood fibers having a high-average
length. Moreover, in another embodiment, eucalyptus fibers can be
combined with softwood fibers, some-of which have been fibrillated as
described above. When utilized, low-average length fibers can generally
25 be incorporated into the outer layers) in any desired amount. Typically, a
fiber blend used in an outer layer of the present invention contains about
50% to about 95% by weight of low-average length fibers, and more
particularly between about 60% to about 90%.
A tissue of the present invention can generally be formed according
30 to a variety of papermaking processes known in the art. In particular, it
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36
should be understood fihat the present invention is not limited to any
particular papermaking process. In fact, any process capable of forming a
tissue having multiple layers can be utilized in the present invention. For
example, a papermaking process of the present invention can utilize
creping, embossing, wet-pressing, through-drying, through-dry creping,
uncreped through-drying, double creping, as well as other steps in forming
the multi-layered paper web. For example, in one embodiment of the
present invention, the tissue can be formed using an uncreped through-
drying technique, such as disclosed in U.S. Patent Nos. 5,048,589 to
Cook, et al. and 5,399,412 to Sudall, et al., which are incorporated herein
in their entirety by reference thereto. Still other methods of forming
tissues are also described and disclosed in U.S. Patent No. 5,129,988 to
Farrinaton. Jr. and in U.S. Patent No. 5,494,554 to Edwards. et al., which
are both incorporated herein in their entirety by reference thereto.
Tissues, such as facial tissues, made according to the present
invention provide many advantages and benefits over conventional tissue
products. The facial tissues have improved facial softness, low surface
friction, low lint production, low slough, high wet strength, and good tear
resistance. in particular, due to the number of bonding sites readily
available to both the bonding agent and softening agent, high loads of
softening agent can be handled by the tissue without causing substantial
slough and lint production.
The present invention may be better understood with reference to
the following examples:
EXAMPLE 1
The ability of a tissue of the present invention to effectively
retain a softening agent was demonstrated. In general, to determine the
retention of the softening agent, a sample of tissue having a basis weight
of about 18.5 pounds per ream was weighed and extracted in a sealed
container for a given amount time on a flatbed shaker at ambient
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conditions. After the extraction, the tissue was removed and the extract
was allowed to settle. The extract was then analyzed by an ultraviolet
spectrometer. After the percent extracted was calculated, the add-on
percentage was determined by an add-on correlation curve, such as
described below.
Construction of Add-On Correlation Curve
InitiaNy, 5.00 grams of the tissue was weighed out for each
replicate (three samples for each add-on level and three untreated
samples) and placed into a sealable container. Four levels of add-on (i.e.,
0.1, 0.3, 0.8, and 1.0%) were utilized to generate the curve. Thus, three
blank samples and three samples for each add-on level were tested,
resulting in 15 total samples.
Two sets of spiking solutions were then prepared to supply the
required add-on levels (1000 and 5000 ppm). Specifically, 1.250 and
6.250 grams of the C-6001 softening agent were placed into 50 ml
beakers. Thereafter, the softening agents were combined with distilled
water and transferred to a 1000 ml flask. The solutions were then shaken
and allowed to dissolve. The add-on levels were formed as follows:
Add-on Level 1000ppm 5000ppm
0.1 % 5mL -
0.3% l5mL -
0.8% - 8mL
1.0% - 10mL
Once formed, the spike solution was applied to the tissue samples
and dried for 48 hours in a 60 degree Celsius oven. Thereafter, 100 ml of
methanol was added to the dried, spiked tissue samples and sealed in the
containers. The solutions were then placed in a flatbed shaker and
extracted for a given amount of time (i.e., 1/2 hour to 16 hours). The tissue
samples were then removed so that the extract could settle. A transfer
pipette was used to deliver a certain amount of the solution for UV
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38
absorbance readings at 238 nm wavelength. A 1/10 dilution was required
for some add-on tissue samples to obtain an adequate reading. Blanks
were read with and without this dilution. A 1/10 dilution reading was used
for 1/10 dilution samples and a no-dilution reading was used for the no-
dilution samples. For each add-on level, the mean absorbence readings
for each of the 3 replicates was subtracted from the value read from the
blanks.
The percent extracted was then calculated from the ppm reading
from the standard curve (imidazoline). In particular,
No Dilution:
Extracted = ppm reading X 0.1 X 100/5000
1/10 Dilution:
Extracted - ppm reading X 0.1 X 10 X 100/5000
An Add-on Correlation curve was then constructed with the percent
extracted values. The best fitting curve (first or second order) was
selected.
Sample Test
After developing the add-on correlation curve, replicates of three
multi-layered tissue samples having basis weights of about 18.5 pounds
per ream were produced and applied with a softening agent in accordance
with the present invention. Each sample contained an outer layer of
varying blends of "Longlac-19", which is available from Kimberly-Clark
Corporation, and eucalyptus fibers. A Witco C-6001 imidazoline-based
softener was applied to each sample in an amount of 0.4% by weight,
based upon the weight each respective paper web.
After being applied with the imidazoline-based softener, each
sample was then tested using the above-mentioned procedure to
determine the total amount of softener that was retained on the tissue
upon application. Specifically, 5.00 grams of the softening agent treated
tissue sample was placed in a specimen container, to which 100 ml of
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39
methanol was added . The specimen containers were placed on the
flatbed shaker and extracted for the same amount time as the spike and
recovery samples. The tissue was removed and the extracts were
allowed to settle. The extracts were then read at 238 nm wavelength,
wherein the sample reading was subtracted from the blank absorbance
reading. The "ppm" of the softening agent was then used to calculate the
percent extracted value. Using the Add-on correlation curve, the percent
add-on was then calculated from the percent extracted value. The
retention efficiency was then calculated, i.e. the percentage of softener
that was retained upon the tissue web. The results are given below in
Table 1:
TABLE 1: Imidazoline Softener Retention
Eucalyptus Longlac-19ImidazolineImidazolineRetention
Fibers (wt. Fibers Target (wt.Detected Efficiency
5 %) (Wt.%) %) (Wt. %) (%)
~
100 0 0.4 0.318 79.5
50 50 0.4 0.326 81.5
30 70 0.4 0.383 95.8
As indicated by Table 1, the ability of a tissue to retain a softening
agent is enhanced by the use of high-average length fibers in a fibrous
blend with low-average length fibers.
EXAMPLE 2
The ability of a tissue of the present invention to effectively
retain a softening agent and to be applied with a softening agent without a
substantial loss in strength was demonstrated. Twelve tissue samples
having a basis weight of about 18.5 pounds per ream were produced
having an outer layer of fibrillated "Longlac-19" fibers, which are available
from Kimberly-Clark Corporation, in accordance with the present
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invention. Specifically, the fibers of each sample were fibrillated at
varying degrees using conventional refining machinery such that three of
the tissue samples had a Canadian Standard Freeness of 681, four of the
tissue samples had a Canadian Standard Freeness of 600, and five of the
5 tissue samples had a Canadian Standard Freeness of 525, as determined
by TAPPI Standard Method T227m-58. A Witco C-6027 imidazoline-
based softener softening agent was then applied to each sample at
varying levels as indicated in Figure 1. After being applied with the
imidazoline-based softener, each sample was then tested to determine
10 the total amount of softener that was retained on the tissue upon
application in accordance with the procedures set forth in Example 1.
In addition, the strength of each sample applied with the
imidazoline-based softener was also tested. In particular, the geometric
mean tensile strength ("GMT") was calculated as the square root of the
15 product of the machine direction tensile strength and the cross-machine
direction tensile strength. The units of GMT strength are grams per 3
inches of sample width, but are simply referred to herein as "grams".
Tensile strengths were determined in accordance with TAPPi test method
T 494 om-88 using flat gripping surFaces, a specimen width of 3 inches, a
20 length of 6 inches, and a crosshead speed of about 10 inches per minute.
The results are illustrated in Figure 1. As shown, for example, the
paper web containing fibers having a Canadian Standard Freeness of 525
achieved a high softening add-on level without a substantial loss in tensile
strength.
25 EXAMPLE 3
The ability of a tissue of the present invention to effectively
retain a softening agent and to be applied with a softening agent without a
substantial loss in strength was demonstrated. Two sets, each containing
three tissue samples having basis weights of about 18.5 pounds per
30 ream, were produced and applied with a softening agent in accordance
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41
with the present invention. One set of samples contained an outer layer
of 100% eucalyptus fibers and the other set of samples contained an
outer layer of 50% eucalyptus fibers and 50% "Longlac-19" fibers, which
are available from Kimberly-Clark Corporation. A Witco C-6001
imidazoline-based softener was then applied to each sample at varying
levels.
After being applied with the imidazoline-based softener, each
sample was then tested as set forth in Example 1 to determine the total
amount of softener retained on the tissue. In addition, the strength of
each sample applied with the imidazoline-based softener was also tested
as set forth in Example 2.
The results are illustrated in Figure 2. As shown, the paper web
containing eucalyptus and "Longlac-19" fibers had the highest extracted
softening level (i.e., retention), while the paper web containing only
eucalyptus fibers had the lowest retention of the softening agent.
Moreover, as shown, the paper web containing eucalyptus and "Longlac-
19" fibers had the highest GMT value, while the web containing only
eucalyptus fibers has the lowest GMT value.
EXAMPLE 4
The ability of a tissue of the present invention to efFectively
reduce stough was demonstrated. Two tissue samples having basis
weights of about 18.5 pounds per ream were produced, wherein one
sample contained an outer layer having only eucalyptus fibers and the
other sample contained an outer layer having 50% "Longlac-19" fibers,
which are available from Kimberly-Clark Corporation, and 50% eucalyptus
fibers. A Witco C-6001 imidazoline-based softener was applied to each
sample in an amount of 8 kilogram per metric ton of each respective
paper web. .
After being applied with the imidazoline-based softener, each
sample was then subjectively tested by a group of panelists to determine
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42
the amount of dry and wet slough generated by the tissues. Specifically,
for evaluating dry slough, each panelist rubbed their thumb against the
tissue samples and visually assessed the slough generated. Moreover,
for evaluating wet slough, each panelist rubbed their wetted thumb
against the tissue samples and visually assessed the slough generated.
The tissue sample containing only eucalyptus fibers was observed to have
more dry and wet dough than the tissue sample containing eucalyptus
fibers and Longlac-19 fibers.
Although various embodiments of the invention have been
described using specific terms, devices, and methods, such description is
for illustrative purposes only. The words used are words of description
rather than of limitation. It is to be understood that changes and
variations may be made by those of ordinary skill in the art without
departing from the spirit or scope of the present invention, which is set
forth in the following claims. In addition, it should be understood that
aspects of the various embodiments may be interchanged both in whole
or in part. Therefore, the spirit and scope of the appended claims should
not be limited to the description of the preferred versions contained
therein.
25
