Note: Descriptions are shown in the official language in which they were submitted.
~32803~
SOFT TISSUE PAPER
CONTAINING NONCATIONIC SURFACTAHT
~OLFGANG U. SPENDEL
TECHNICAl FIEL~
This invention relates, in general, to tissue paper; and more
! specifically, to high bulk tissue paper having an enhanced tactile
sense of softness.
BACKGROUND OF IHEIU~o~ QN
Soft tissue paper is generally preferred for disposable paper
towels, and facial and toilet tissues. Ho~ever, known methods and
means for enhancing softness of tissue paper generally adversely
affect tensile strength. Tissue paper product design is,
therefore, generally, an exercise in balancing softness against
tensile strength.
1~ Both ~echanical and chemical means have been introduced in
the pursuit of making soft tissue paper: tissue paper which is
perceived by users, through their tactile sense, to be soft. A
well known mechanical method of increasing tensile strength of
paper made from cellulosic pulp is by mechanically refining the
pulp prior to papermaking. In general, greater refining results
in greater tensile strength. However, consistent with the
foregoing discussion of tissue tensile strength and softness,
increased mechanical refining of cellulosic pulp negatively
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impacts tissue paper softness, all other aspects of the
papermaking furnish and process being unchanged.
A variety of chemical treatments have been proposed to
increase the tactile sense of softness of tissue paper sheets.
For example, it was disclosed in German Patent 3,420,940, Kenji
Hara et al, to dip, impregnate, or spray dry tissue paper with a
combination of a vegetable, animal, or synthetic hydrocarbon oil
and a silicone oil such as dimethylsilicone oil. Among other
benefits, the silicone oil is said to impart a silky, so~t feeling
to the tissue paper. This tissue paper, contemplated for toilet
paper applications, suffers from disposal complications when
flushed through pipe and sewer systems in that the oils are
hydrophobic and will cause the tissue paper to float, espec1ally
with the passage of time subsequent to treatment with the oils.
Another disadvantage is high cost associated with the apparent
high levels of the oils contemplated.
It has also been disclosed to treat tissue paper and the
furnish used to make tissue paper with certain chemical debond;ng
agents. For example, U.S. Patent 3,844,880, Meisel Jr. et al,
issued October 29, 197~, teaches that the addition of a chemical
debonding agent to the furnish prior to sheet formation leads to a
softer sheet of tissue paper. The chemical debonding agents used
in the Meisel Jr. et al process are preferably cationic. Other
references, e.g., U.S. Patent 4,158,594, 8ecker et al, issued
January I9, l979 and Armak Company, of Chicago, Illinois, in their
bulletin 76-17 (1977) have proposed the app1ication of cationic
debonders subsequent to sheet formation. Unfortunately, cationic
debonders in general have certain disadvantages associated with
their use in tissue paper softening applications. In particular,
some low ~olecular weight catignic debonders may cause excessive
irritation upon contact with human skin. Higher molecular weight
cationic debonders may be more difficult to apply in low levels to
tissue paper, and also tend to have undesirable hydrophobic
effects upon the tissue paper. Additionally, the cationic
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3 132803~
debonder treatments of these references tend to decrease tensile
strength to such an extent that the use of substantial levels of
resins, latex, or other dry strength additives is required to
provide commercially acceptable levels of tensile strength. Such
dry strength additives add substantial raw materials cost to the
tissue paper due to the relatively high level of additive required
to provide sufficient dry strength. Furthermore, many dry
strength additives have a deleterious affect on tissue softness.
It has now been discovered that treating tissue with a
noncationic surfactant results in significant improvement in the
tissue paper's tensile/softness relationship relative to
traditional methods of increasing softness. That is, the
noncationic surfactant treatment of the present invention greatly
; enhances tissue softness, and any accompanying decrease in tensi1e
strength can be offset by traditional methods of increasing
tensile strength such as increased mechanical reflning. It has
further been discovered that the additlon of an effective amount
of a blnder, such as starch, will at least partially offset any
reduction in tensile strength and/or increase in lint~ng
propensity that results from the noncationic surfactant.
While the present invention relates to improving the softness
of paper in general, it pertains in particular to improving the
tactile perceivable softness of high bulk, creped tissue paper.
Representative high bulk, creped tissue papers which are quite
soft by contemporary standards, and which are susceptible to
softness enhancement through the present invention are disclosed
in the following U.S. Patents: 3,301,746, Sanford and Sisson,
issued January 31, 1967; 3,974,025; Ayers, issued August 10, 1976;
3,9~4,771 Morgan Jr. et al, issued ~ovember 30, 1976; 4,191,609,
Trokhan, issued March 4, 1980 and 4,637,859, Trokhan; issued
January 20, 1987. Each of these papers is characterized by a
pattern of dense areas: areas more dense than their respective
remainders, such dense areas resulting from being compacted during
papermaking as by the crossover knuckles of imprinting carrier
4 132803~
fabrics. Other high bulk, soft tissue papers are
disclosed in U.S. Patent 4,300,981, Carstens, issued
November 17, 1981; and 4,440,597, Wells et al, issued
April 3, 1984. Additionally, achieving high bulk tissue
paper through the avoidance of overall compaction prior
to final drying is disclosed in U.S. Patent 3,821,068,
Shaw, issued June 28, 1974; and avoidance of overall
compaction in combination with the use of debonders and
elastomeric bonders in the papermaking furnish is
disclosed in U.S. Patent 3,812,000, Salvucci Jr., issued
May 21, 1974.
It is an object of an aspect of this invention to
provide ti~sue paper which has an enhanced tactile sense
of softness.
It is an object of an aspect of this invention to
provide tissue paper which has increased tactile
softness at a particular level of tensile strength
relative to tissue paper which has been softened by
conventional techniques.
These and other ob~ect~ are obtained using the
present invention, as will be seen from the following
disclosure.
SUMM~R~ OF THE INVENTION
An aspect of this invention is as follows:
Tissue paper having a basis weight of from about 10
to about 65 grams per square meter, and density of about
0.6 grams or less per cubic centimeter, said paper
comprising cellulosic fibers, an effective amount of an
alkyl glycoside surfactant, said effective amount of
alkyl glycoside surfactant being from about 0.01% to
about 2.0% alkyl glycoside surfactant based on the dry
fiber weight of said tissue paper, and an effective
amount of a starch binder material, said effective
amount of starch being from about 0.01% to about 2.0%
based on the dry fiber weight of said tissue paper.
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4a 1328035
In one aspect of the invention, tissue paper is
provided having a basis weight of from about 10 to about
65 g/m2, fiber density of about 0.6 g/cc or less, and
which comprises an effective amount of a noncationic
surfactant additive to effect enhanced softness. The
noncationic surfactant is, preferably, applied to a wet
tissue web. Preferably, the tissue paper comprises from
about 0.01% to about 2 percent of the noncationic sur-
factant additive, based on the dry fiber weight of the
tissue paper; and, more preferably, the amount of such
an additive is from about 0.05 to about 1.0 percent. An
especially unexpected benefit of the noncationic surfactant
treatment of the tissue paper at the preferred
noncationic surfactant levels discussed above, is the
high level of tactile softness, at a given tensile
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s 132803~ :
strength, relative to conventional methods for increasing
softness, such as decreasing the level of mechanical refining.
That is, the addition of the noncationic surfactant makes it
possible to provide soft tissue paper at the ~esired tensile
strength by, for example, maintaining or increasing the level of
mechanical refining.
Noncationic surfactants which are suitable for use in the
present invention include anionic, nonionic, ampholytic and
zwitterionic surfactants. Preferably, the noncationic surfactant
is a nonionic surfactant, with nonionic alkylglycosides being
especially preferred. Also, preferably, the surfactant is
substantially nonmigratory in situ after the tissue paper has been
manufactured in order to substantially obviate post-manufacturing
changes in the tissue paper's properties which might otherwise
result from the inclusion of surfactant. This may be achieved,
for instance, through the use of noncationic surfactants having
melt temperatures greater than the temperatures commonly
encountered during storage, shipping, merchandising, and use of
tissue paper product embodiments of the invention: for example,
melt temperatures of about 50-C or higher.
Tissue paper comprising a noncationic surfactant in
accordance with the present invention may further comprise an
effective amount of a binder material such as starch to offset any
increase in linting propensity or reduction of tensile strength,
which would otherwise result from the incorporation of the
surfactant material. Preferably, the binder material is added to
a wet tissue web. Surprisingly, it has been found that surface
treatment of tissue paper with a noncationic surfactant and starch
mixture resu1ts in tissue which is softer for a given tensile
strength than tissue which has been treated with noncationic
surfactant alone. The effective amount of binder material is
preferably from about 0.01 to about 2 percent on a dry fiber
weight basis of the tissue paper.
132803~
A particularly preferred tissue paper embodiment of the
present invention comprises from about O.OS to about 1.0 percent
of a nonionic surfactant material; and from about 0.l to about 1.0
percent starch, all quantities of these additives being on a dry
fiber weight basis of the tissue paper.
The present invention is described in more detail below.
DETAIlED D~SCRIPTION OF THE INVENTION
Briefly, the present invention provides tissue paper having
an enhanced softness through the incorporation of a noncationic
surfactant additive. Any reduction in tensile strength of the
tissue paper resulting from the addition of the noncationic
surfactant can be offset by conventional methods of increasing
tensile strength, such as increased mechanical refining, thereby
yielding a softer paper at a given tensile strength. Such tissue
paper may further include an effective amount of a binder material
such as starch to offset any exacerbation of linting propensity
and/or reduction of tissue paper tensile strength which may be
precipitated by the addition of the noncationic surfactant.
Surprislngly, the combination of surfactant and starch treatments
has been found to provide greater softness benefits for a given
tensile strength level than the softness benefits obtained by
treatment with the noncationic surfactant alone. This is totally
unexpected because the isolated effect of the binder treatment is
ts increase strength and consequently decrease softness of the
tissue paper.
~hile not wishing to be bound by a theory of operation or to
otherwise limit the present invention, tissue paper embodiments of
the present inYention are generally characterized as being ~ithin
a tri-parametric domain defined by empirically determined ranges
of the following parameters: first, the ratio of their Total
Flexibility to their Total Strength; second, their Physiological
Surface SMoothness; and third, their Slip-And-Stick Coefficient of -
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~32803~
Friction. For example, tests conducted in accordance with the
following procedures defined by the present invention's
tri-parametric domain as: a ratio of Total Flexibility to Total
Tensile Strength of about 0.13 or less; Physiological Surface
Smoothness of about O.9S or less; and a Slip-and-Stick Coefficient ~:
of Friction of about 0.033 or less for pattern densified tissue
papers, and about 0.038 or less for tissue paper embodiments
having substantially uniform densities. By way of contrast, all
contemporary tissue papers which have been tested and which do not
embody the present invention fell outside this tri-parametric
domain. These parameters and tests are discussed below.
FLEXIBIllTY and TOTAL F~ ILITY
:
Flexibility as used herein is defined as the slope of the
secant sf the graph-curve derived from force vs. stretch X data
which secant passes through the origln (zero X stretch, zero
force) and through the point on the graph-curve where the force
per centimeter of width is 20 grams. For example, for a sample
which stretches 10% (i.e., 0.1 cm/cm of length) wlth 20 grams of
force per cm of sample width, the slope of the secant through (OX,
O) and (lOX, 20) is 2.0 using the formula:
Y2 Y
Slope ~ ------------
X2 - Xl
Total Flexibility as used herein means the geometric mean of
the machine-direction flexibility and cross-machine-direction
flexib~lity. Mathematically, this ~s the square root of the
product of the machine-direction flexibility and cross-machine-
direction flexibility in grams per cm.
TOTAL TENSILE STRENGTH
Total tensile strength as used herein means the geometric
mean of the machine and cross-machine breaking strengths in grams
per cm of sample width. ~athematically, ~his is the square root
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132803~ ~
of the product of the machine and cross-machine direction breaking
strengths in grams per cm of sample width.
~ABY FACTOR
The ratio of Total Flexibility to Total Tensile Strength has
been determined to be a factor ~hich characterizes embodiments of
the invention as being strong yet having high bulk softness. This
ratio is hereby dubbed the ~ABY Factor.
Total Flexibility
~A8Y Factor ~ ------------------------
Total Tensile Strength
For instance, a sample having a Total Flexibility of 20 g/cm, and
a Total Tensile Strength of 154 g/cm has a ~ABY Factor of 0.13.
Briefl~, tactile perceivable softness of tissue paper is
inversely related to its ~ABY Factor; and limited empirical data
indicate that tissue paper embodiments of the present invention
have ~ABY Factors of about 0.13 or less. Also, note that the ~ABY
Factor is dimensionless because both Flexibility and Total Tensile
Strength as defined above are in g/cm, their ratio is
dimensionless.
PHYSIOLOGICAL SURFACE SMQQTHNESS
Physiological surface smoothness as used herein is a factor
5herein,after the PSS Factor) derived from scanning machine-
direction tissue paper samples with a profilometer (described
be10w) having a diamond stylus, the profilometer being installed
in a surface test apparatus such as, for example, Surface Tester
KES-FB-4 which is available from KATO TECH CO., LTD., Karato-Cho,
Nishikiyo, Minami-Ku, Koyota, Japan. In this tester, a sample of
tissu~ is mounted on a motorized drum, and a stylus is gravita-
tiona11y biased towards the drum at the 12 o'clock position. The ;
drum is rotated to provide a sample velocity of one (1) mi11imeter
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~ 132803S
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per second, and moves the sample 2 cm. with respect to the probe.
Thus, the probe scans a 2 cm length of the sample. ~he
profilometer comprises means for counterbalancing the stylus to ~:
-. provide a normal force of 270 mg. Basically, the instrument
senses the up and down displacements (in mm) of the stylus as a 2
cm length of sample is scanned under the profilometer probe. The
resulting stylus-amplitude vs. stylus-distance-scanned data are
digitized, and then converted to a stylus-amplitude vs. frequency
spectrum by performing a Fourier Transform using the Proc Spectra
standard program available from SAS Institute Inc., Post Office
Box 10066, Raleigh, North Carolina 27605. This identifies
spectral components in the sample's topography; and the frequency
spectral data are then adjusted for human tactile responsiveness
as quantified and reported by Verrillo (Ronald T. Verrillo,
~Effect of Contractor Area on the Vibrotactile Threshold~, The
Journal of thc Accoust kal Society of America, 35, 1962 (1963)).
However, whereas Verrtllo's data are in the time domain (i.e.,
cycles per secondJ, and physiologtcal surface smoothness ls
related to finger-to-sample velocity, Verrillo-type data are
~o converted to a spatial domain ~i.e., cycles per millimeter) using
65 mm/sec as a standard finger-to-sample velocity factor.
Finally, the data are integrated from zero (O) to ten (10) cycles
per millimeter. The result is the PSS Factor. Graphically, the
PSS Factor is the area under the Verrillo-adjusted frequency
?~ (cycles/mm) vs. stylus amplitude curve bet~een zero (0) and ten
(10) cycles per millimeter. Preferably, DSS Factors are average
values derived from scanning multiple samples (e.g., ten samples),
both forward and backward. ~
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The profilometer described above comprises, more
specifically, a Gould Surfanalyzer Equipment Controller
~21-1330-20428, Probe ~21-3100-465, Oiamond stylus tip (0.0127 mm
radius) ~21-0120-00 and stylus tip extender ~22-0129-00 all
available from Federal Products, Providence, RI. The profilometer
probe assembly is fitted with a counterbalance, and set up as
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lO 1328035 :
depicted in Figure 22 of United States patent 4,300,981 (referenced hereinbefore).
SLIP-AND-STICK COEFFICIENT OF FRICTION
Slip-and-stick coefficient of friction (hereinafter S&S COF) is defined as the mean
deviation of the coefficient of friction. It is dimensionless. It may be determined using
commercially available test apparatus such as, for example, the Kato Surface Tester identified
above which has been fitted with a stylus which is configured and disposed to slide on the
surface of the sample being scanned: i.e., a fritted glass disk. When a sample is scanned as
described above, the instrument senses the lateral force on the stylus as the sample is moved
thereunder: i.e., scanned. The lateral force is called the frictional force; and the ratio of
frictional force to stylus weight is the coefficient of friction, mu. The instrument then solves
the following equation to determine S&S COF for each scan of each sample.
sOx / ~ / d
S&S COF +
sOx d"
in which
is the ratio of frictional force to probe loading;
is the average value of ~; and
X is 2 cm.
Returning now to the Detailed Description of The Invention, the present invention --
noncationic surfactant treated tissue papers having enhanced tactile responsiveness -- includes
but is not limited to: conventionally felt-pressed tissue paper; pattern densified tissue paper
such as exemplified by Sanford-Sisson and its progeny; and high bulk, uncompacted tissue
paper such as exemplified by Salvucci. The tissue paper may be of a homogenous
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13~803~ :~
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or multilayered construction; and tissue paper products made
therefrom may be of a single-ply or multi-ply construction. ~he
tissue paper preferably has a basis weight of between about lO
g/m2 and.about 65 g/m2, and density of about 0.60 g/cc or less.
Preferably, basis weight will be below about 35 g/m2 or less; and
density ~ill be about 0.30 g/cc or less. Host preferably, density
will be between about 0.04 g/cc and about 0.20 g/cc.
Papermaking fibers which may be utilized for the present
invention include fibers derived from wood pulp. Other cellulosic
fibrous pulp fibers, such as cotton linters, bagasse, etc., can be
utilized and are intended to be within the scope of this
invention. Synthetic fibers, such as rayon, po1yethylene and
! polypropylene fibers, may also be utilized in combination with
natural cellulosic fibers. One exemplary polyethylene fiber which
may be utilized is PulpexTM, available from Hercules, Inc. (~
mington, Delaware).
Applicable wood pulps include chemical pulps made by the
Kraft, sulfite, and sulfate processes; and mechanical pulps
including, for example, groundwood, thermomechanical pulp and
chemically modified thermomechanical pulp. Chemical pulps,
however, are preferred since they impart a superior tactile
perceivable softness to tissue sheets made therefrom. Pulps may
be utilized which are derived from both deciduous trees which are
sometimes referred to as ~hardwoodn; and coniferous trees which
are sometimes referred to as "softwoodn.
In addition to papermaking fibers, the papermaking furnish
used to make tissue paper structures may have other components or
materials added thereto: for example, wet-strength and temporary
wet-strength resins.
Types of noncationic surfactants which are suitable for use
in the present invention include anionic, nonionic, ampholytic,
and zwitterionic surfactants. Mixtures of these surfactants can
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132803~
12
also be u~ed. As used herein the term noncationic
surfactants shall include all of such types of -~
surfactants. The preferred noncationic surfactants are
anionic and nonionic surfactants with nonionic
surfactants being most preferred. The noncationic
surfactants preferably have alkyl chains containing
eight or more carbon atoms.
A. Nonionic Surfactants
Suitable nonionic surfactants are generally
disclosed in U.S. Patent 3,929,678, Laughlin et al,
issued December 30, 1975, at column 13, line 14 through
column 16, line 6, incorporated herein by reference.
Classes of useful nonionic surfactants include:
1. The condensation products of alkyl phenols
with ethylene oxide. These compounds include the
condensation products of alkyl phenols having an alkyl
group containing from about 8 to about 12 carbon atoms
in either a straight chain or branched chain
con~iguration with ethylene oxide, the ethylene oxide
being present in an amount equal to from about 5 to
about 25 moles of ethylene oxide per mole of alkyl
phenol. Examples of compounds of this type include
nonyl phenol condensed with about 9.5 moles of ethylene
oxide per mole o~ phenol; dodecyl phenol condenRed with
about 12 moles of ethylene oxide per mole of phenol;
dinonyl phenol condensed with about 15 moles of ethylene
oxide per mole of phenol; and diisooctyl phenol
condensed with about 15 moles of ethylene oxide per mole
of phenol. Commercially available nonionic surfactants
of this type include IgepalTM C0-630, marketed by the
GAF Corporation; and Triton~M X-45, X-114, X-100, and
X-102, all marketed by the Rohm & Haas Company.
2. The condensation products of aliphatic
alcohols with from about 1 to about 25 moles of ethylene
35 oxide. The alkyl chain of the aliphatic alcohol can -~
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1328035
either be straight or branched, primary or secondary,
and generally contains from about 8 to about 22 carbon
atoms. Particularly preferred are the condensation
products of alcohols having an alkyl group containing
from about 10 to about 20 carbon atoms with from about 4
to about 10 moles of ethylene oxide per mole of alcohol~
Examples of such ethoxylated alcohols include the
condensation product of myristyl alcohol with about 10
moles of ethylene oxide per mole of alcohol; and the
condensation product of coconut alcohol (a mixture of
fatty alcohols with alkyl chains varying in length from
10 to 14 carbon atoms) with about 9 moles of ethylene
oxide. Examples of commercially available nonionic
surfactants of this type include TergitolTM 15-S-9 (the
condensation product of Cll-C15 linear alcohol with 9
moles ethylene oxide), marketed by Union Carbide
Corporation; NeodolTM 45-9 (the condensation product of
C14-C15 linear alcohol with 9 moles of ethylene oxide),
Neodol 23-6.5 (the condensation product of C12-C13
linear alcohol with 6.5 moles of ethylene oxide),
NeodolTM 45-7 (the condensation product of C14-C15
linear alcohol with 7 moles of ethylene oxide), NeodolTM
45-4 (the condensation product of C1~-C15 linear alcohol
with 4 moles of ethylene oxide), marketed by Shell
Chemical Company, and KyroTM EOB (the condensation
product of C13-C15 linear alcohol with 9 moles ethylene
oxide), marketed by The Procter ~ Gamble Company.
3. The condensation product~ of ethylene oxide
with a hydrophobic base formed by the condensation of
propylene oxide with propylene glycol. The hydrophobic
portion of these compounds has a molecular weight of
from about 1500 to about 1800 and exhibits water
insolubility. The addition of polyoxyethylene moieties
to this hydrophobic portion tends to increase the water
solubility of the molecule as a whole, and the liquid
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1328035
14
character of the product is retained up to the point
where the polyoxyethylene content is about 50% of the
total weight of the condensation product, which
corresponds to condensation with up to about 40 moles of
ethylene oxide. Examples of compounds of this type
include certain of the commercially available PluronicTM
surfactants, marketed by Wyandotte Chemical Corporation.
4. The condensation products of ethylene oxide
with the product resulting from the reaction of
propylene oxide and ethylenediamine. The hydrophobic
moiety of these products consists of the reaction
product of ethylenediamine and excess propylene oxide,
and generally has a molecular weight of from about 2500
to about 3000. This hydrophobic moiety is condensed
with ethylene oxide to the extent that the condensation
product contains from about 40% to about 80% by weight
of polyoxyethylene and has a molecular weight of from
about 5,000 to about 11,000. Examples of this type of
nonionic surfactant include certain of the commercially
available TetronicTM compound~, marketed by Wyandotte
Chemical Corporation.
5. Semi-polar nonionic surfactants, which include
water-soluble amine oxides containing one alkyl moiety
of from about 10 to about 18 carbon atoms and 2 moieties
selected from the group consisting of alkyl groups and
hydroxyalkyl groups containing from about 1 to about 3
carbon atoms; water-soluble phosphine oxides containing
one alkyl moiety of from about 10 to about 18 carbon
atoms and 2 moieties selected from the group consisting
of alkyl groups and hydroxyalkyl groups containing from
about 1 to about 3 carbon atoms; and water-soluble
sulfoxides containing one alkyl moiety of from about 10
to 18 carbon atoms and a moiety selected from the group
consisting of alkyl and hydroxyalkyl moieties of from
35 about 1 to 3 carbon atoms. -
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1328035
14a
Preferred semi-polar nonionic surfactants are the
amine oxide surfactants having the formula
R3(oH4)xNR52
wherein R3 is an alkyl, hydroxyalkyl, or alkyl phenyl
group or mixtures thereof containing from about 8 to
about 22 carbon atoms; R4 is an alkylene or
hydroxyalkylene group containing from about 2 to about 3
carbon atoms or mixtures thereof: x is from O to about
A
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15 1328035
3; and each R5 is an alkyl or hydroxyalkyl group containing from
about I to about 3 carbon atoms or a polyethylene oxide group
containing from about I to about 3 ethylene oxide groups. The R5
groups can be attached to each oeher, e.g., through an oxygen or
nitrogen atom, to form a ring structure.
Preferred amine oxide surfactants are Clo-C18 alkyl dimethyl
amine oxides and Cg-C12 alkoxy ethyl dihydroxy ethyl amine oxides.
6. Alkylpolysaccharides disclosed in U.S. Patent 4,565,647,
Llenado, issued January 21, 1986, having a hydrophobic group
containing from about 6 to about 30 atoms, preferably from about
10 to about 16 carbon atoms and a polysaccharide, e.g., a
polyglycoside, hydrophilic group containing from about 1-1/2 to
about 10, preferably from about 1-1/2 to about 3, ~ost preferably
from about 1.6 to about 2.7 saccharide units. Any reducing
saccharide containing 5 or 6 carbon atoms can be used, e.g.,
glucose, galactose and galactosyl moieties can be substituted for
the glucosyl moieties. (Optionally the hydrophobic group is
attached at the 2-, 3-, 4-, etc. positions thus giving a glucose
or galactose as opposed to a glucoside or galactoside.) The
intersaccharide bonds can be, e.g., between the l-position of the
additional saccharide units and the 2-, 3-, 4-, and/or 6-
positions on the preceding saccharide units.
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Optionally, and less desirably, there can be a
polyalkyleneoxide chain joining the hydrophobic moiety and the
polysaccharide moiety. The preferred alkyleneoxide is ethylene
oxide. Typical hydrophobic groups include alkyl groups, either
saturate or unsaturated, branched or unbranched containing from
about 8 to about 18, preferably from about 10 to about 16, carbon
atoms. Preferably, the alkyl group is a straight chain saturated
alkyl group. The alkyl group can contain up to 3 hydroxy groups
and/or the polyalkyleneoxide chain can contain up to about 10,
preferably less than 5, alkyleneoxide moieties. Suitable alkyl
polysaccharides are octyl, nonyldecyl, undecyldodecyl, tridecyl, ~ -
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132803~
16
tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl, di-
tri-, tetra-, penta-, and hexaglucosides, galactosides,
lactosides, g1ucoses, fructosides, fructoses and/or ga1actoses.
Suitable mixtures include coconut alkyl, di-, tri-, tetra-, and
pentaglucosides and tallow alkyl tetra-, penta-, and
hexaglucosides.
Alkylpolyglycosides are particularly preferred for use in the
present invention. The preferred alkylpolyglycosides have the
formula
R20(CnH2nO)t(91YCsYl )x
wherein R2 is selected from the group consisting of alkyl,
alkylphenyl, hydroxyalkyl, hydroxyalkylphenyl, and mixtures
thereof in which the alkyl groups contain from about 10 to about
18, preferably from about 12 to about 1~, carbon atoms; n is 2 or
3, preferably 2; t is from O to about 10, preferably 0; and x is
from about 1-l/2 to about 10, preferably from about 1-1/2 to about
3, most preferably from about 1.6 to about 2.7. The glycosyl is
preferably derived from glucose. To prepare these compounds, the
alcohol or alkylpolyethoxy alcohol is formed first and then
reacted with glucose, or a source of glucose, to form the
glucoside (attachment at the 1-position). The additional glycosyl
units can then be attached between their 1-position and the
preceding glycosyl units 2-, 3-, 4- and/or 6-position, pre~erably
predominately the 2-position.
Commercially available alkylglycosides include alkylglycoside
polyesters such as CrodestaTM SL-40 which is available from Croda,
Inc. (New York, NY) and alkylglycoside polyethers as described in
U.S. Patent 4,011,389, issued to ~. K. Langdon, et al, on March 8,
1977. Alkylglycosides are additionally disclosed in U.S. Patent
3,598,865, Lew, issued August 1971; U.S. Patent 3,721,633,
Ranauto, issued March 1973; U.S. Patent 3,772,269, Lew, issued
November 1973; U.S. Patent 3,640,998, Mansfield et al, issued
February 1972; U.S. Patent 3,839,318, Mansfield. issued October
.
,
.
1328035
17
1974; and U.S. Patent 4,223,129, Roth et al., issued in
September 1980.
7. Fatty acid amide surfactants having the
formula
0
R6 _ C - NR72
wherein R6 is an alkyl group containing from about 7 to
about 21 (preferably from about 9 to about 17) carbon
atoms and each R7 is selected from the group consisting
of hydrogen, Cl-C4 alkyl, Cl-C4 hydroxyalkyl, and
-~C2H4)x where x varies from about 1 to about 3.
Preferred amides are C8-C20 ammonia amides, mono-
ethanolamides, diethanolamides, and isopropanolamides.
B. Anionic Surfactants
Anionic surfactants suitable for use in the present
invention are generally disclosed in U.S. Patent
3,929,678, Laughlin et al, issued December 30, 1975, at
column 23, line 58 through column 29, line 23. Classes
of useful anionic surfactants include:
1. Ordinary alkali metal soaps, such as the
sodium, potassium, ammonium and alkylolammonium salts of
higher fatty acids containing from about 8 to about 24
carbon atoms, preferably from about 10 to about 20
carbon atoms. Preferred alkali metal soaps are sodium
laurate, sodium stearate, sodium oleate and potassium
palmitate.
2. Water-soluble salts, preferably the alkali -
metal, ammonium and alkylolammonium salts, of organic
sulfuric reaction products having in their molecular
structure an alkyl group containing from about 10 to
about 20 carbon atoms and a sulfonic acid or sul~uric
acid ester group. (Included in the term "alkyl" is the
alkyl portion of acyl groups.)
,
:
fA
. . .
- ;
18 ~328~3~
Examples of this group of anionic surfactants are the sodium
and potassium alkyl sulfates, especially those obtained by
sulfating the higher alcohols (Cg-Clg carbon atoms), such as those
roduced by reducing the glycerides of tallo~ or coconut oil; and
the sodium and potassium alkylben2ene sulfonates in which the
alkyl group contains from about 9 to about 15 carbon atoms, in
straight chain or branched chain configuration, e.g., those of the
type described in U.S. Patent 2,220,099, Guenther et al, issued
November 4, 1940, and U.S. Patent 2,~7,383, Lewis, issued December
26, 1946. Especially useful are linear straight chain
alkylbenzene sulfonates in which the average number of carbon
atoms in the alkyl group is from about 11 to about 13, abbreviated
as Cll-C13LAS.
I
Another group of preferred anionic surfactants of thls type
are the alkyl polyethoxylate sulfates, part kularly those in which
the alkyl group contains from about lO to about 22, preferably
from about 12 to about 18 carbon atoms, and wherein the
. polyethoxylate chain contains from about 1 to about 15 ethoxylate
moieties, preferably from about 1 to about 3 ethoxylate moieties.
Other anionic surfactants of this type include sodium alkyl
glyceryl ether sulfonates, especially those ethers of higher
alcohols derived from tallow and coconut oil; sodiu~ coconut oil
fatty acid monoglyceride su1fonates and sulfates; sodium or
potassium salts of alkyl phenol ethylene oxide either sulfates
containing from about 1 to about 10 units of ethylene oxide per
molecule and wherein the alkyl groups contain from about 8 to
about 12 carbon atoms; and sodium or potassium salts of alkyl
ethylehe oxide ether sulfates containing about 1 to about 10 units
of ethylene oxide per molecule and wherein the alkyl group
contains from about 10 to about 20 carbon atoms.
Also included are water-soluble salts of esters of
alpha-sulfonated fatty acids containing fro~ about 6 to about 20
carbon atoms in the fatty acid group and from about 1 to about lO
carbon atoms in the ester group; water-soluble salts of
2-acylox~-alkane-1-sulfonic acids containi~c rom about 2 to a~ou
19 1328035
9 carbon atoms in the acyl group and from about 9 to
about 23 carbon atoms in the alkane moiety; alkyl ether
sulfates containing from about 10 to about 20 carbon
atoms in the alkyl group and from about 1 to about 30
moles of ethylene oxide; water-soluble salts of olefin
sulfonates containing from about 12 to about 24 carbon
atoms; and beta-alkyloxy alkane sulfonates containing
from about 1 to about 3 carbon atoms in the alkyl group
and from about 8 to about 20 carbon atoms in the alkane
moiety.
3. Anionic phosphate surfactants.
4. N-alkyl substituted succinamates.
C. Ampholytic Su~factants
Ampholytic surfactants can be broadly described as ^~
aliphatic derivatives of secondary or tertiary amines,
or aliphatic derivatives of heterocyclic secondary and
tertiary amines in which the aliphatic radical can be
straight or branched chain and wherein one of the
aliphatic substituents contains from about 8 to about 18
carbon atoms and at least one of the aliphatic
6ubstituents contains an anionic water-solubilizing
group, e.g. ~ carboxy, sulfonate, sulfate. See U.S.
Patent 3,929,678, Laughlin et al, issued December 30,
1975, column 19, line 38 through column 22, line 48, for
examples of ampholytic surfactants useful herein.
D. Zwitterionic Surfactants
Zwitterionic surfactants can be broadly described
as derivatives of secondary and tertiary amines,
derivatives of heterocyclic secondary and tertiary
amines, or derivatives of quaternary ammonium, quater-
nary phosphonium or tertiary sulfonium compounds. See
U.S. Patent 3,929,678, Laughlin et al, issued December
30, 1975, column 19, line 38 through column 22, line 48,
for examples of zwitterionic surfactants useful herein.
The above listings of exemplary noncationic
surfactants are in fact intended to be merely exemplary
' ' -
.' '. :,
132803~
in nature, and are not meant to limit the scope of the
invention. Additional noncationic surfactants useful in
the present invention and listings of their commercial
sources can be found in McCutcheon's Detergents and
Emulsifiers, North American Ed. pages 312-317 (1987).
The noncationic surfactant can be applied to tissue
paper as it is being made on a papermaking machine or
thereafter: either while it is wet (i.e., prior to final
drying) or dry (i.e., after final drying). However, it
has been found that greater softness benefits are
obtained by addition of the noncationic surfactant to a
wet web. Without being bound by theory, it is believed
that addition of the noncationic surfactant to a wet web
allows the surfactant to interact with the tissue before
the bonding structure has been completely set, resulting
in a softer tissue paper than obtained by treating a dry
tissue web with a noncationic surfactant. Preferably,
an aqueous mixture containing the noncationic surfactant
is sprayed onto the tissue paper as it courses through
the papermaking machine: for example, and not by way of
limitation, referring to a papermaking machine of the
general configuration disclosed in Sanford-Sisson
(reference hereinbefore), either before the predryer, or
after the predryer. Addition of the noncationic
surfactant to the wet end of the paper machine (i.e.,
the paper furnish) is impractical due to low retention
levels of the surfactant and excessive foaming.
As di~cus6ed above, the noncationic surfactant is
preferably applied subsequent to formation of the wet
web and prior to drying to completion. In a typical
procQss, the web i8 formed and then dewatered prior to
application of the noncationic surfactant in order to
reduce the loss of noncationic surfactant due to drainage
~ ~ .
A
... .. , . . .. . . . . . . . -.. ~.. .. . , - . .. ~ .. . . . . . . .
~ ~ 1328035 : :
21
of free water. ~he noncationic surfactant is preferably, applied
to the wet web at a fiber consistency levels of between IOX and
about 807., more preferably between about 15% and about 35%, in the
. manufacture of conventional1y pressed tissue paper; and to a wet
S web having a fiber consistency of between about 20% and about 35%
in the manufacture of tissue paper in papermaking machines wherein
the newly formed web is transferred from a fine mesh Fourdrinier
to a relatively coarse imprinting/carrier fabric. This is because
it is preferable to make such transfers at sufficiently low fiber
consistencies that the fibers have substantial mobility during the
transfer; and it is preferred to apply the noncationic surfactant
after their mobility has substantially dissipated as water removal
progresses through the papermaking machine. Also, addition of the
noncationic surfactant at higher fiber consistencies assures
greater retention in and on the paper: i.e., less noncationic
surfactant is lost in the water being drained from the ~eb to
increase lts fiber consistency. Surprisingly, retention rates of
noncationic surfactant applied to wet webs are high even though
the noncationic surfactant is applied under conditions wherein it
is not ionically substantive to the fibers. Retention rates in
excess of about 90% are expected at the preferred fiber
consistencies without the utilization of chemical retention aids.
Methods of applying the noncationic surfactant to the web
include spraying and gravure printing. Spraying, has been found
to be economical, and susceptible to accurate control over
quantity and distribution of noncationic surfactant, so is most
preferred. Other methods which are less preferred include
deposition of the noncationic suifactant onto a forming wire or
fabric which is then contacted by the tissue web; and
incorporation of the noncationic surfactant into the furnish prior
to web formation. Equipment suitable for spraying noncationic
surfactant containing liquids onto wet webs include external mix,
air atomizing nozzles such as the 2 mm nozzle available from
,',
,. ;. , ~ -
~.
22 1328035 : ~
V.I.B. Systems, Inc., Tucker, Georgia. ~quipment suitable for
printing noncationic surfactant eontaining liquids onto wet webs
includes rotogravure printers.
The noncationic surfactant should be applied uniformly to the
wet tissue paper web so that substantially the entire sheet
benefits from the tactile effect of noncationic surfactant.
Applying the noncationic surfactant to the wet tissue ~eb in
continuous and patterned distributions are hoth within the scope
of the invention and meet the above criteria.
Noncationic surfactant can be applied to dry paper ~ebs by
the same methods previously discussed with respect to ~et paper
web noncationic surfactant treatments.
Preferably, as stated hereinbefore, the noncationic
surfactant is substantially nonmtgratory in situ after the tissue
paper has been manufactured in order to substantially obviate
post-manufacturing changes in the tissue paper's properties which
might otherwise result from the incluslon of noncationic
surfactant. This may be achieved, for instance, through the use
of noncationic surfactants having melt temperatures greater than
the temperatures commonly encountered during storage, shipping,
merchandising, and use of tissue paper product embodiments of the
invention: for example, melt temperatures of about 50'C or
higher. Also, the noncationic surfactant is preferably water-
soluble when applied to the wet web. ~ ~
It has been found, surprisingly, that low levels of a ~ -
noncationic surfactant applied to tissue paper structures can
provide an enhanced tactile sense of softness without the aid of
additional materials such as oils or lotions. Importantly, these
benefits can be obtained for many of the embodiments of the
present invention in combination with tensile strengths within the
ranges desirable for toilet paper application. Preferably, tissue
paper treated with noncationic surfactant in accordance with the
,
~,'-',
132~03~ ::
23
:..
present invention comprises about 2% or less noncationic
surfactant. It is an unexpected benefit of this invention that
tissue paper treated with about 2% or less noncationic surfactant
. can have imparted thereto substantial.softness by such a lo~ ~evel
of noncationic surfactant. :
The level of noncationic surfactant applied to tissue paper
to provide the aforementioned softness/tensile benefit ranges from
about 0.01% to about 2X noncationic surfactant retained by the
tissue paper, more preferably, from about O.OSX to about I.0%
based on the dry fiber ~eight of the tissue paper.
As stated hereinbefore, it is also desirable .to treat
noncationic surfactant containing tissue paper w~th a relatively
low level of a binder for lint control and/or to increase tensile
strength. As used herein, the term 'binder~ refers to the various
wet and dry ~trength addit~ves known in the art. Starch has been
found to be the preferred binder for use in the present invention.
Preferably, the tissue paper is treated with an aqueous solution
of starch and, also preferably, the sheet is moist at the time of
application. In addition to reducing linting of the f nished
tissue paper product, low levels of starch also imparts a ~odest
improvement in the tensile strength of tissue paper ~ithout
imparting boardiness (i.e., stiffness) which would result from
additions of high levels of starch. Also. this provides tissue
paper having improved strength/softness re'ationship compared to
tissue paper which has been strengthened by traditional methods
of increasing tensile strength: for example, sheets having
increased tensile strength due to increased refining of the pulp;
or through the addition of other dry strength additives.
Surprisingly, it has been found that the combination of
noncationic surfactant and starch treatments results in greater
softness benefits for a given tensile strength level than the
softness benefits obtained by treating tissue paper ~ith a
noncationic surfactant alone. This result is especially
surprising since starch has traditionally been used to build
strength at the expense of softness in applications ~herein
132803~
softness is not an important characteristic: for example,
paperboard. Additionally, parenthetically, starch has been used
as a filler for printing and ~riting paper to improve surface
printability.
In general, suitable starch for practicing the present
invention is characterized by water solubility, and
hydrophilicity. Exemplary starch materials include corn starch
and potato starch, albeit it is not ~ntended to thereby limit the
scope of suitable starch materials; and ~axy corn starch that is
known industrially as amioca starch is particularly preferred.
Amioca starch differs from common corn starch in that it is
entirely amylopectin, whereas common corn starch contains both
amplopectin and amylose. Various unique characteristics of amioca
starch are further described in ~Amioca - The Starch From ~axy
Corn~, H, H. Schopmeyer, Food Industries, December 1945, pp.
106-108 (Vol. pp. 1~76-1~78).
The starch can be in granular or dispersed form, albeit
granular form is preferred. The starch is preferably sufficiently
cooked to induce swelling of the granules. More preferably, the
starch granules are swollen, as by cooking, to a point just prior
to dispersion of the starch granule. Such highly swollen starch
granules shall be referred to as being ~fully cooked.~ The
conditions for dispersion in general can vary depending upon the
size of the starch granules, the degree of crystallinity of the
granules, and the amount of amylose present. Fully cooked amioca
starch, for example, can be prepared by heating an aqueous slurry
of about 4% consistency of starch granules at about l90'F (about
88-C) for between about 30 and about 40 minutes. - ;
Other exemplary starch materials which may be used include
modified cationic starches such as those modified to have nitrogen
containing groups such as amino groups and methylol groups
attached to nitrogen, available from National Starch and Chemical
Company, (Bridgewater, New Jersey). Such modified starch
materials have heretofore been used primarily as a pulp furnish
.
: - . . .
25 1328~3~ ~
additive to increase wet and/or dry strength. However when
applied in accordance with this invention by application to a wet
tissue paper web they may have reduced effect on wet strength
relative to wet-end addition of the same modified starch
materials. Considering that such modified starch materials are
more expensive than unmodified starches, the latter have generally
been preferred.
The starch should be applied to the tissue paper while the
paper is in a moist condition. The starch based material is added
to the tissue paper web, preferably when the web has a fiber
consistency of about 80X or less. Noncationic starch materials
are suff;ciently retained in the web to provide an observable
effect on softness at a particular strength level relative to in-
creased refining; and, are preferably applied to wet t1ssue webs
having fiber consistencies between about lOX and about 80%, more
preferably, between about 15% and 35X.
.
Starch is preferably applied to tissue paper webs in an
aqueous solution. Methods of application include, the same pre-
viously described with reference to application of noncationic
surfactant: preferably by spraying; and, less preferably, by
printing. The starch may be applied to the tissue paper web
simultaneously with, prior to, or subsequent to the addition of
noncationic surfactant.
At least an effective amount of starch to provide lint
control and concomitant strength increase upon drying relative to
a non-starch treated but otherwise identical sheet is preferably
applied to the sheet. Preferably, between about 0.01% and about
2.0X of starch is retained in the dried sheet, calculated on a dry
fiber weight basis; and, more preferably, between about 0.l% and
about 1.0% of starch-based material is retained.
Analysis of the amounts of treatment chemicals herein re-
tained on tissue paper webs can be performed by any method
accepted in the applicable art. For example. the 1evel of
:
132803~ :
26
nonionic surfactants, such as alkylglycosides. retained by the
tissue paper can be determined by extraction in an organic solvent
followed by gas chromatography to determine the level of
surfactant in the extracti-the level of anianic surfactants, such
as linear alkyl sulfonates, can be determined by water extraction
followed by colorimetry analysis of the extract; the level of
starch can be determined by amylase digestion of the starch to
glucose followed by colorimetry analysis to determine glucose
level. These methods are exemplary, and are not meant to exclude
other methods which may be useful for determining levels of
particular components retained by the tissue paper.
Hydrophilicity of tissue paper refers, in general, to the
propensity of the tissue paper to be wetted with water.
Hydrophilicity of tissue paper may be somewhat quantified by
determining the period of time required for dry tissue paper to
become completely wetted with water. This period of time is
referred to as ~wetting tlme.~ In order to provide a consistent
and repeatabte test for wetting time, the following procedure may
be used for wetting time determinations: first, a dry (greater
than 90% fiber consistency level) sample unlt sheet, approximately
~-3/8 inch x 4-3/~ inch (about 11.1 cm x 12 cm) of tissue paper
structure is provided; second, the sheet is folded into four (4)
juxtaposed quarters, and then crumpled into a ball approximately
0.~5 inches (about 1.9 cm) to about 1 inch (about 2.5 cm) in
diameter; third, the balled sheet is placed on the surface of a
body of distilled water at 72-F (about 22-C), and a timer is
simultaneously started; fourth, the timer is stopped and read when
wetting of the balled sheet is completed. Complete wetting is
observed visually.
The preferred hydrophilicity of tissue paper depends upon its
intended end use. It is desirable for tissue paper used in a
variety of applications, e.g., toilet paper, to comple~ely wet in - ~-
a relatively short period of time to prevent clogging once the
toilet is flushed. Preferably, wetting time is 2 minutes or less.
, ~ ".
,~ '' '.
2~ 132803~ ~
More preferably, ~etting time is 30 seconds or less. Most
preferably, wetting time is lO seconds or less.
Hydrophilicity characters of tissue paper embodiments of the
present invention may, of course, be determined immediately after
manufacture. However, substantial increases in hydrophobicity may
occur during the first two weeks after the tissue paper is made:
i.e., after the paper has aged two (2) weeks fo110wing its
manufacture. Thus, the above stated ~etting times are preferably
measured at the end of such two week period. Accordingly, wetting
times measured at the end of a two week aging period at room
temperature are referred to as ~two week wetting times.~
.: .
The density of 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 approprlate unit converslons
incorporated therein. Caliper of the tissue paper, as used
herein, is the thickness of the paper when subjected to a
compresslve load of 95 g/in2 (15.5 g/cm2).
The following examples illustrate the practice of the present
invention but are not intended to be limiting thereof.
~XAMPLE I
The purpose of this example is to illustrate one method that
can be used to make soft tissue paper sheets treated with a
noncationic surfactant in accordance with the present invention.
A pilot scale Fourdrinier papermaking machine is used in the
practice of the present invention. The paper machine has a
layered headbox having a top chamber, a center chamber, and a
bottom chamber. ~here applicable as indicated in the following
examples, the procedure described below also applies to such later
examples. Briefly, a first fibrous slurry comprised primarily of
short papermaking fibers is pumped through the top and bottom
,. ' : .
~ ,~
28 13280~`~
headbox chambers and, simultaneously, a second fibrous slurry
comprised primarily of long papermaking fibers is pumped through
the center headbox chamber and delivered in superposed re1ation
- onto the Fourdrinier wire to form thereon a three-layer embr~onic
web. The level of mechanical refining of the second fibrous slurry
(composed of long papermaking fibers) is increased to offset any
tensile strength loss due to the noncationic surfactant treatment.
The first slurry has a fiber consistency of about 0. llX and its
fibrous content is Eucalyptus Hardwood Kraft. The second slurry
has a fiber consistency of about 0.15% and its fibrous content is
Northern Softwood Kraft. Dewatering occurs through the
fourdrinier wire and ls assisted by a deflector and vacuum boxes.
The Fourdrinier wire is of a 5-shed, satin weave configuration
hav~ng 87 machine-direction and 76 cross-mach~ne-direction ~ono-
filaments per inch, respectively. The edbryonic wet web is
transferred from the Fourdr1nier wire, at a f~ber consistency of
about 22X at the polnt of transfer, to a carrier fabric having a
5-shed satln weave , 35 machine-direct~on and 33
cross-mach~ne-direct~on monofilaments per lnch,respectively. The
non-fabric side of the web is sprayed with an aqueous solution
containing a noncationic surfactant, further described below, by a
2 mm spray nozzle located directly opposite a vacuum dewatering
box. The sprayed web is carried on the carrier fabric past the
vacuum dewatering box, through blow-through predryers after which
the web is transferred onto a Yankee dryer. The other process and
machine conditions are listed below. The fiber consistency is
about 27% after the vacuum dewatering box and, by the action of
the predryers, about 65% prior to transfer onto the Yankee dryer; -
creping adhesive comprising a 0.25% aqueous solution of polyvinyl
alcohol is spray applied by applicators; the fiber consistency is ;
increased to an estimated 9g% before dry creping the web with a
doctor blade. The doctor blade has a bevel angle of about 24
degrees and is positioned with respect to the Yankee dryer to
provide an 1mpact angle of about 83 degrees; the Yankee dryer is
operated at about 350-F (177-C); the Yankee dryer is operated at
abut 800 fpm (feet per minute) (about 244 meters per minute). The
dry creped web is then passed between two salender rolls. The
.- ~,
:
.::
29 I 3 2 8 ~ 3
two calender rolls are biased together at roll ~eight and operated
at surface speeds of 660 fpm (about 201 meters per minute).
The aqueous solution sprayed through the spray nozzle onto
the wet web contains CrodestaTMSL-40 an alkyl glycoside polyester
nonionic surfactant. The concentration of the nonionic surfactant
in the aqueous solution is adjusted until about 0.15%, based upon
the weight of the dry fibers, is retained on the web. The
votumetric flo~ rate of the aqueous solution through the nozzle is
about 3 gal./hr.-cross-direction ft (about 37 liters/hr-meter).
The retention rate of the nonionic surfactant applied to the web,
in general, is about 90%.
~he resulttng tissue paper has a basis weight of 30g/m2, a
denstty of .lOg/cc, and contatns O.lSX b~ wetght, of the alkyl
glycoside polyester nontontc surfactant.
The resulttng tissue paper ts htghly wettable and has
enhanced tacttle softness.
EXAMPLE II
The purpose of this example is to il1ustrate one method that
can be used to make soft tissue paper sheets wherein the tissue
paper is treated with noncationic surfactant and starch.
A 3-layer paper sheet is produced in accordance with the
hereinbefore described process of Example I. The tissue web is,
in addition to betng treated with a noncationic surfactant as
described above, also treated ~ith full~ cooked amioca starch
prepared as described in the specification. The starch is applied
simultaneously with the noncationic surfactant as part of the
aqueous solution sprayed through the papermachine spray nozzle.
Concentratton of the starch in the aqueous solution is adjusted so
that the level of amtoca starch retained is about 0.2%, based upon
3~ the weight of the dry fibers. The resulting tissue paper has a
basis weight of 30g/m2, a density of .IOg,cc, and contains O.lSX
-.
1328035
~o
by weight of CrodestaTM SL-40 nonionic surfactant and
0.2~ by weight of the cooked amioca starch.
Importantly, the result is a soft tissue sheet having
enhanced softness and strength, and lower propensity
for lint than the sheet treated only with the
noncationic surfactant.
