Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1 328335
PROCESS FOR PREP~RIHG
SOFT TISSUE PAPER TREATED
WITH NOHCATIONIC SURFACTAN~
~OLFGANG U. SPENDEL
S TECHNICAL FIELD
This invention relates, in general, to a process for
preparing tissue paper; and ~ore specifically, to a process for
preparing high bulk tissue piper having an enhanced tactile sense
of softness.
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BACKGROUND OF THE INVENTION
Soft tissue paper is generally preferred for disposable paper
towels, and facial and toilet tissues. However, 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.
Both mechanical 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 maJe 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
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1 328335
foregoing discussion of tissue tensile strength and softness,
increased mechanical refining of cellulosic pulp negatively
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 3,420,9~0, 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, soft feeling
to the tissue paper. This tissue paper, contemplated for toilet
paper applications, suffers fro~ disposal complications when
flushed through pipe and sewer systems in that the oils are
hydrophobic and will cause the tissue paper to float, especiall~
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
?O furnish used to make tissue paper with certain chemical debonding
agents. For example, U.S. Patent 3,84~,880, Meisel ~r. et al,
issued October 29, 197q, teaches that the addition of a chemical
debonding agent to the furnish prior to sheet formation 1eads 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, Becker et al, issued
January 19, 1979 and Armak Company, of Chicago, Illinois, in their
bulletin 76-17 (19773 have proposed the application 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 molecular weight cationic 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
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1 3~8335
tissue paper, and also tend to have undesirable hydrophobic
effects upon the tissue paper. Additionally, the cationic
debonder treatments of these references tend to decrease tensile
strength to such an extent that the use of substantial levels of
resins, 1atex, or other dry strength additives is required to
provide commercially acceptable levels of tensile strength. Such
dry strength additives add substantial raw ~aterials 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 wet tissue paper
webs with a noncationic surfactant results in significant
improvement in the tissue paper's tensile/softness relationship
relative to tradit~onal methods of increasing softness. That is,
the noncationic surfactant treatment of the present invention
greatly enhances tissue softness and any acco~panying decrease in
tensile strength can be offset by traditional methods o~ in-
creasing tensile strength such as increased Jechanical refining.
It has further been discovered that the addition of an effective
amount of a binder, such as starch, to the ~et tissue web ~
at least partially offset any reduction in tensile strength andior
increase in linting propensity that results from the noncationic
surfactant.
~hile the present invention re1ates to impr~ving 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;
3,994,771 Morgan Jr. et al, issued November 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
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41 328335
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 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 a process for preparing tissue paper which has
an enhanced tactile sense of softness.
It is an object of an aspect of this invention to
provide a proce~s for preparing 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 objects are obtained using the
present invention, as will be seen from the following
disclosure.
~UMMARY OF THE INVENTION
The present invention encompasses a process for
making soft tis~ue paper. This process includes the
steps of wet laying cellulosic fibers to form a web,
applying to the web, at a fiber consistency of from
about 10% to about 80% (total web weight basis), a
sufficient amount of a water-soluble noncationic
surfactant such that between about 0.01% and about 2.0%
of said noncationic surfactant, dry fiber weight basis,
i6 retained by the tissue paper, and then drying and
cr~ping the web. The resulting
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1 328335
s
tissue paper preferably has a basis weight of from about lO to
about 65 g/m2 and a fiber density of less than about 0.6 g/cc.
The noncationic surfactant is applied subsequent to formation
of the wet web and prior to drying to completion. Surprisingly,
it has been found that noncationic surfactants have high rates of
retention when applied to wet tissue paper web in accordance with
the process disclosed herein. This is especially unexpected
because the noncationic surfactants are applied to the wet webs
under conditions wherein they are not ionically substantive to the
cellulosic fibers. An important benefit of the
noncationic surfactant treatment, applied at the preferred
fiber consistency levels and noncationic surfactant levels
discussed above, is the high level of tactile softness, at a given
tensile strength, relative to conventional methods for increasing
softness, such as decreasing the level of ~echanic-l refining.
That ls, the addition of the noncationic surfactant makes it
possible to provide soft tissue paper at the desired tensile
strength by, for example, maintaining or increasing the level of
~echanical 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
substant1ally nonmigratory in situ after the tissue paper has been
manufactured 1n order to substantially obviate post-manufacturing
changes in the tissue paper's pr.operties ~hich 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.
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1 328335
The process for preparing tissue paper treated with
a noncationic surfactant in accordance with the present
invention may further comprise the step of adding 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 noncationic surfactant
material. Surprisingly, it has been found that surface
treatment of tissue paper with a noncationic surfactant
and starch mixture results in tissue which is softer for
a given tensile strength that tissue which has been
treated with noncationic surfactant alone. The
effective amount of binder material is such that,
preferably, from about 0.01 to about 2 percent, on a dry
fiber weight basis, is retained by the tissue paper.
Other aspects of this invention are as follows: -
A process for making soft tissue paper, said
process comprising the steps of:
(a) wet-laying cellulosic fibers to form a web;
(b) applying to said web, at a fiber consistency
of from about 10% to about 80%, total web weight basis,
a sufficient amount of a water-soluble noncationic
surfactant such that from about 0.01% to about 2.0% of
said noncationic surfactant, based on the dry fiber
weight of said tissue paper, is retained by said web;
(c) applying to said web, at a fiber consistency
of from about 10% to about 80%, total web weight basis,
a sufficient amount of a starch binder material such
that from about 0.01~ to about 2.0% of said starch,
based on the dry fiber weight of said tissue paper, is
retained by said web; and
(d) drying and creping said web;
wherein said tissue paper has a basis weight of
from about 10 to about 65 g/m2 and a density of less
than about 0.60 g/cc.
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- 1 328335
6a
The product made by the process set out
hereinabove.
All percentages, ratios and proportions herein are
by weight, unless otherwise specified.
The present invention is described in more detail
below.
DETAILED DESCRIPTION OF THE INVENTION
Briefly, the present invention provides a process
for preparing tissue paper having an enhanced softness
through the addition of a noncationic surfactant
additive to a wet tissue web. Surprisingly, retention
rates of noncationic surfactant applied to wet webs in
accordance with the present invention are high even
though the noncationic surfactant is applied under
conditions wherein it is not ionically substantive to
the anionic cellulosic fibers. To ensure high retention
rates, the wet web is formed and dewatered prior to
application of the noncationic surfactant in order to
reduce the loss of noncationic surfactant due to
drainage of free water. Importantly, it has been found
that greater softness benefits are obtained by addition
of the ncncationic surfactant to a wet web than through
the addition of a noncationic surfactant to a dry web.
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` 1 328335
Any reduction in tensile strength of the tissue paper
resulting from the addition of the noncationic surfactant can be
offset by conventional ~ethods of increasing tensile strength such
as increased mechanica-l refining of the pulp, thereby yielding a
S softer paper at a given tensile strength. Such process may
further include the addition of an effective amount of a binder
material such as starch to the wet tissue web 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. Surprisingly, 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 to increase strength and
consequently decrease softness of the tissue paper.
The present invention is applicable to tissue paper in
general, including but 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 or multilayered construction; and tissue
paper products made therefrom may be of a single-ply or multi-ply
construction. The t;ssue paper preferably has a basis weight of
between about 10 g/m2 and about 6S 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 will be about 0.30 g/cc or less. Most
preferably, density will be between O.O~i g/cc and about 0.20 g/cc.
Conventionally pressed tissue paper and methods for making
such paper are known in the art. Such paper is typically made by
depositing papermaking furnish on a foraminous forming wire.
This forming wire is often referred to in the art as a Fourdrinier
wire. Once the furnish is deposited on the forming wire, it is
referred to as a web. The web is dewatered by pressing the web
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1 328335
and dried at elevated temperature. The particular
techniques and typical equipment for making webs
according to the process just described are well known
to those skilled in the art. In a typical process, a
low consistency pulp furnish is provided in pressurized
headbox. The headbox has an opening for delivering a
thin deposit of pulp furnish onto the Fourdrinier wire
to form a wet web. The web i8 then typically dewatered
to a fiber consistency of between about 7% and about 25%
(total web weight basis) by vacuum dewatering the
further drying by pressing operations wherein the web is
subjected to pressure developed by opposing mechanical
members, for example, cylindrical rolls. The de-watered
web is then further pressed and dried by a stream drum
apparatus known in the art as a Yankee dryer. Pressure
can be developed at the Yankee dryer by mechanical means
such as an opposing cylindrical drum pressing against
the web. Multiple Yankee dryer drums may be employed,
whereby additional pressing is optionally incurred
between the drums. The tissue paper structures which
are formed are referred to hereinafter as conventional,
pressed, tissue paper structures. Such sheets are
considered to be compacted since the web is subjected to
substantial mechanical compressional forces while the
fibers are moist and are then dried while in a
compressed state.
Pattern densified tissue paper is characterized by
having a relatively high bulk field of relatively low
fiber density and an array of densified zones of
relatively high fiber density. The high bulk field is
alternatively characterized as a field of pillow
regions. The densified zones are alternatively referred
to as knuckle regions. The densified zones may be
discretely spaced within the high bulk field or may be
interconnected, either fully or partially, within the
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1 328335
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high bulk field. Preferred processes for making
pattern densified tissue webs are disclosed in U.S.
Patent No. 3,301,746, issued to Sanford and Sisson on
January 31, 1967, U.S. Patent No. 3,974,025, issued to
Peter G. Ayres on August 10, 1976, and U.S. Patent No.
4,191,609, issued to Paul D. Trokhan on March 4, 1980.
1 328335
In general, pattern densified webs are preferably prepared by
depositing a papermaking furnish on a foraminous forming ~ire such
as a Fourdrinier wire to form a wet web and then juxtaposing the
web against an array of sup~orts. The web is pressed against the
S array of supports, thereby resulting in densified zones in the web
at the locations geographically corresponding to the points of
contact between the array of supports and the wet web. The
remainder of the web not compressed during this operation is
referred to as the high bulk field. Formation of the densified
zones may be accomplished by application of fluid pressure, such
as with a vacuum type device or a blow-through dryer, or by
mechanically pressing the web against the array of supports. The
web is dewatered, and optionally predried, in such a manner so as
to substantially avoid compression of the high bulk field. This
lS is preferably accomplished by fluid pressure, such as with a
vacuum type device or blow-through dr~er, or alternately by
mechanically pressing the web against an array of supports wherein
the high bulk field is not compressed. The operations of
dewatering, optional predrying and formation of the densified
zones may be integrated or partially int~grated to reduce the
total number of processing steps performed. Subsequent to
formation of the densified zones, dewatering, and optional
predrying, the web is dried to completion, preferably still
avoiding mechanical pressing. Preferably, from about 1% to about
14% of the tissue paper sur~ace comprises densified knuckles
having a relative density of at least 70% of the density of the
high bulk field.
¦ The array of supports is preferably an imprinting carrier
fabric having a patterned displacement of ~nuckles which operate
as the array of supports which facilitate the formation of the
densified zones upon application of pressure. The pattern of
¦ knuckles constitutes the array of supports previously referred to.
', Imprinting carrier fabrics are disclosed in U.S. Patent No.
3,301,~46, Sanford and Sisson, issued January 31, 196~, U.S.
Patent No. 3,821,068, Salvucci, Jr. et al.... issued May 21. 1974,
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1 328335
U.S. Patent No. 3,974,025, Ayers, issued August 10, 1976,
U.S. Patent No. 3,573,164, Friedberg et al. issued March
30, 1971 and U.S. Patent No. 3,473,576, Amneus, issued
October 21, 1969.
Preferably, the furnish is first formed into a wet
web on a foraminous forming carrier, such as a Four-
drinier wire. The web is dewatered and transferred to an
imprinting fabric. The furnish may alternately be
initially deposited on a foraminous supporting carrier
which also operates as an imprinting fabric. Once formed,
the wet web is dewatered and, preferably, thermally
predried to a selected fiber consistency of between about
40% and about 80%. Dewatering is preferably performed with
suction boxes or other vacuum devices or with blow-through
dryers. The knuckle imprint of the imprinting fabric is
impressed in the web as discussed above, prior to drying
the web to completion. one method for accomplishing this
is through application of mechanical pressure. This can be
done, for example, by pressing a nip roll which supports
the imprinting fabric against the face of a drying drum,
such as a Yankee dryer, wherein the web is disposed be-
tween the nip roll and drying drum. Also, preferably, the
web is molded against the imprinting fabric prior to com- ~ -
pletion of drying by application of fluid pressure with a
vacuum device such as a suction box, or with a blow-through
dryer. Fluid pressure may be applied to induce impression
of densified zones during initial dewatering, in a sepa- ~ -
rate, subsequent process stage, or a combination thereof.
Uncompacted, nonpattern-densified tissue paper
structure~ are described in U.S. Patent No. 3,812,000
issued to Joseph L. Salvucci, Jr. and Peter N. Yiannos on
May 21, 1974 and U.S. Patent 4,208,459 issued to Henry E.
Becker, Albert L. McConnell, and Richard Schutte on June
17, 1980. In general, uncompacted, nonpattern-densified
tissue paper structures are prepared by depositing a
papermaking furnish on a foraminous forming wire such as a
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1 328335
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fourdrinier wire to form a wet web, draining the web and removing
additional water without mechanical compression until the web has
a fiber consistency of at least 80%, and creping the web. ~ater
is removed from the web by vacuum de~atering and thermal drying.
The resulting structure is a soft but weak high bulk sheet of
relatively uncompacted fibers. Bonding material is preferably
applied to portions of the web prior to creping.
The papermaking fibers utilized for the present invention
will normally 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, polyet-hylene and
polypropylene fibers, may also be utilized in combination with
natural cellulosic fibers. One exemplary polyethylene fiber which
may ~e utilized is PulpexTM~ available from Hercules, Inc.
(~ilmington, Delaware.)
Applicable wood pulps include chemical pulps, such as Kraft,
sulfite and sulfate pulps, as well as mechanical pulps, including,
for example, groundwood, thermomechanical pulp and chemically
modified thermomechanical pulp. Chemical pulps, however, are
preferred since they impart a superior tactile sense of softness
to tissue sheets made therefrom. Pulps derived - from both
deciduous trees (hereinafter, also referred to as ~hardwood~) and
coniferous trees (hereinafter, also referred to as ~softwood~) may
be utilized.
.
In addition to papermaking fibers, the papermaking furnish
used to make tissue paper structures may have other components or
materials added thereto as may be or later become known in the
art. The types of additives desirable will be dependent upon the
particular end use of the tissue sheet contemplated. For example,
in products such as toilet paper, paper towels, facial tissues and
other similar products, high wet strength is a desirable
1 328335
12
attribute. Thus, it is often desireable to add to the
papermaking furnish chemical substances known in the art
as "wet strength" resins.
A general dissertation on the types of wet strength
resins utilized in the paper art can be found in TAPPI
monograph series No. 29, Wet Strength in Paper and Paper
-board, Technical Association of the Pulp and Paper
Industry (New York, 1965). The most useful wet strength
resins have generally been cationic in character. Poly-
amide-epichlorohydrin resins are cationic wet strength
resins which have been found to be of particular utility.
Suitable types of such resins are described in U.S. Patent
Nos. 3,700,623, issued on October 24, 1972 and 3,772,076,
issued on November 13, 1973, both issued to Keim. One
commercial source of a useful polyamide-epichlorohydrin
resins is Hercules, Inc. of Wilmington, Delaware, which
markets such resin under the mark KymemeTM 557H.
Polyacrylamide resins have also been found to be of
utility as wet strength resins. These resins are
described in U.S. Patent Nos. 3,556,932, issued on
January 19, 1971 to Coscia, et al. and 3,556,933, issued
on January l9, 1971 to Williams, et al. One commercial
source of polyacrylamide resins is American Cyanamid Co.
of Stanford, Connecticut, which markets one such resin
25 under the mark ParezTM 631 NC. -
Still other water-soluble cationic resins finding
utility in this invention are urea formaldehyde and
melamine formaldehyde resins. The more common
functional groups of these polyfunctional resins are
nitrogen containing groups such as amino groups and
methylol groups attached to nitrogen. Polyethylenimine
type resins may also find utility in the present invention.
It is to be understood that the addition of chemical
compounds such as the wet strength resins discussed
above to the pulp furnish is optional and is not
necessary for the practice of the present development.
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1 32~335
13
Types of noncationic surfactant which are suitable
for use in the present invention include anionic,
nonionic, ampholytic, and zwitterionic surfactants.
Mixtures of these surfactants can also be used. 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. 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
configuration with ethylene oxide, the ethylene oxide
being present in an amount e~ual 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 of phenol; dodecyl phenol condensed 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 TritonTM X-45, X-114, X-100, and
X 102, all marketed by the Rohm & Haas Company.
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1 328335
14
2. The condensation products of aliphatic
alcohols with from about 1 to about 25 moles of ethylene
oxide. The alkyl chain of the aliphatic alcohol can
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 C-12-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 C14-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 products 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
35 from about 1500 to about 1800 and exhibits water
insolubility. The addition of polyoxyethylene moieties
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1 328335
to this hydrophobic portion tends to increase the water
solubility of the molecule as a whole, and the liquid
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 corres-
ponds 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 propy-
lene 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 compounds,
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 lO 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
about 1 to 3 carbon atoms.
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1 328335
15a
Preferred semi-polar nonionic surfactants are the
amine oxide surfactants having the formula
R3(oH4)xNR52
~ . . . -. . . . . .
1 328335
16
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 thereo'; x is from O to about
53; and each R5 is an alkyl or hydroxyalkyl group containing from
about 1 to about 3 carbon atoms or a polyethylene oxide group
containing from about 1 to about 3 ethylene oxide groups. The R5
groups can be attached to each other, e.g., through an oxygen or
nitrogen atom, to form a ring structure.
10Preferred 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
1510 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, most preferably
from about 1.6 to about 2.7 saccharide units. Any reducing
saccharide containing S or 6 carbon ato~s can be used, e.g.,
ooglucose, galactose and galactosyl moieties can be substituted for
the glucosyl moieties. IOptionally 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 car, be, e.g., between the l-position of the
25additional saccharide units and the 2-, 3-, 4-, and/or 6-
positions on the preceding saccharide units.
Optionally, and less desirably, there can be a
polyalkyleneoxide chain joining the hydrophobic moiety and the
polysaccharide moiety. The preferred alkyleneoxide is ethylene
30oxide. 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 s~raight chain saturated
1 328335
17
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,
tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl, di-,
tri-, tetra-, penta-, and hexaglucosides, galactosides,
lactosides, glucoses, fructosides, fructoses and/or galactoses.
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(91YCosyl )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 i4. carbon atoms; n is 2 or
3, preferably 2; t is from 0 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). ~he additional glycosyl
units can then be attached between their 1-position and the
preceding glycosyl units 2-, 3-, 4- and/or 6-position, preferably
predominately the 2-position.
Commercially available alkylglycosides include alkylglycoside
polyesters such as CrodestaTM SL-40 ~hich 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 9.
,3
'' ' ' ' '' , `, . ,
1 328335
18
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 9ctober 1974; and
U.S. Patent 4,223,129, Roth et al., issued in September
1980.
7. Fatty acid amide surfactants having the
formula
o
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, C1-C4 alkyl, C1-C4 hydroxyalkyl, and -
(C2H4)x where x varies from about l to about 3.
Preferred amides are C8-C20 ammonia amides, mono-
ethanolamides, diethanolamides, and isopropanolamides.
~. 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,
incorporated herein by reference. Classes of useful
anionic surfactants include:
1. Ordinary alkali metal soaps, such as the
sodium, potassium, ammonium and alkylolammoniu~ 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.
A
; . . .
.
1 328335
2. ~ater-soluble salts, preferabl~ 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 sulfuric acid ester group. (Included in the term ~alkyl~
is the alkyl portion of acyl groups.)
Examples of this group of anionic surfactants are the sodium
and potassium alkyl sulfates, especially those obtained by
sulfating the higher alcohols (Cg-C1g carbon atoms), such as those
produced by reducing the glycerides of tallo~ or coconut oil; and
the sodium and potassium alkylbenzene 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, 6uenther et al, issued
November ~, 1940, and U.S. Patent 2,~71,383, 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 C11-C13LAS.
Another group of preferred anionic surfactants of this type
are the alkyl polyethoxylate sulfates, particularly those in which
the alkyl group contains from about 10 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 oi this type include sodium alkyl
glyceryl ether sulfonates, especially those ethers of higher
alcohols derived from tallow and coconut oil; sodium coconut oil
fatty acid monoglyceride sulfonates and sulfates; sodium or
potassium salts of alkyl phenol ethylene oxide either sulfates
containing from about 1 to abo~t 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
1 328335
ethylene 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 from about 6 to
about 20 carbon atoms in the fatty acid group and from
about 1 to about 10 carbon atoms in the ester group;
water-soluble salts of 2-acyloxy-alkane-1-sulfonic acids
lo containing from about 2 to about 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 l to about 3 carbon
atoms in the alkyl ~roup and from about 8 to about 20
carbon atoms in the alkane moiety.
3. Anionic phosphate surfactants.
4. N-alkyl substituted succinamates.
C. Ampholytic Surfactants
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
substituents 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 l9, line 38 through column 22, line 48, for
examples of ampholytic surfactants useful herein.
.;,. - - ~ : : ..
~. ', : : ~ -, ' ' :'
r, , . : ' ~ . :
~;, . . .. . : ' ' .
~ . .
'
1 328335
21
D. Zwitterionic Surfactants
Zwitterionic surfactants can be broadly described as
derivatives of secondary and tertiary amines, derivatives
of heterocyclic secondary and tertiary amines, or deriv-
atives of quaternary ammonium, quaternary phosphonium ortertiary 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 sur-
factants are in fact intended to be merely exemplary
immature, 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 Deteraents and
Emulsifiers, North American Ed. pages 312-317 (1987).
The noncationic surfactant is applied subsequent to
formation of the wet web and prior to drying the com-
pletion. It has been found that addition of the non-
cationic 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.
Therefore, in a typical process, the web i8 formed and then
dewatered prior to noncationic surfactant application in
order to reduce the loss of noncationic surfactant due to
drainage of free water. The noncationic surfactant is
preferably applied to the wet web at a fiber consistency
level of between 10% and about 80% (based on the weight of
the wet web), more preferably between about 15% and about
35%, in the manufacture of conventionally pressed tissue
paper; and to a wet web having a fiber consistency of
between about 20~ and about 35% in the manufacture of
tissue paper in paper-makinq 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
A
- ~ ~
, ~
r~
., , ~
1 328335
22
make such transfers at sufficiently low fiber consistencies that
the fibers have substantial mobility during the transfer; and it
is preferr~d 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 web to
increase its 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 anionic cellulosic fibers.
Retention rates in excess of about 90% are expected at the
preferred fiber consistencies without the utili~ation of chemical
lS retention aids.
The noncationic surfactant should be applied uniformly to the
wet tissue paper web so that substantiall~ the entire sheet
benefits from the tactile effect of noncationic surfactant.
Applying the noncationic surfactant in continuous and patterned
~C distributions are both within the scope of invention and meet the
above criteria.
Methods of uniformly 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. Preferably, an aqueous mixture containing the
noncationic surfactant is sprayed onto the wet tissue web 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 (referenced
hereinbefore), either before the predryer, or after the predryer,
depending on the desired fiber consistency level. A less
preferred method includes deposition of the noncationic surfactant
onto a forming wire or fabric which is then contacted by the
.. ~ . . . :
1 328335
23
tissue web. Equipment suitable for spraying noncationic
surfactant containing liquids onto ~et webs include external mix,
air atomi~ing nozzles, such as the 2 mr nozzle available from
V.I.B. Systems, Inc., Tucker, Georgia. Equipment suitable for
S printing noncationic surfactant containing liquids onto wet webs
includes rotogravure printers.
Preferably, as stated hereinbefore, the noncationic
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 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 s.urfactant is preferably
water-soluble when applied to the wet web.
It has been found, surprisingly, 'lat greater softness
benefits are obtained by addition of the noncationic surfactant to
a wet web, as opposed to a dry web. ~ithout being bound by
theory, it is believed that addition of the noncationic surfactant
to a wet web allows the surfactant to in~eract with the tissue
before the bonding structure has been comple~ely set, resulting in
a softer tissue paper. Preferably, sof~ ~issue prepared in
accordance with the process of the 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 low 1evel of noncationic
surfactant.
The level of noncationic surfactant applied to wet tissue
webs to provide the aforementioned softness benefit ranges from
about 0.01% to about 27. noncationic surfactant retained by the
. ~ , . . .
.~: i, , , , ~ , ,
1 328335
24
tissue paper, more preferably, from about 0.05% to about l.OX
based on the dry fiber weight of the tissue ~aper.
Importantly, addition of the preferred levels of noncationic
surfactant to wet tissue web, as described above, 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 tensile strength can be offset by
traditional methods of increasing tensile strength. Thus, for
example, tissue paper may be made with pulp that has been
subjected to increased refining levels (which increases strength),
and then treated with noncationic surfactant as contemplated
herein to reduce dry strength to the same level as an unmodified
control. The treated tissue paper ~ould be expected to have a
higher level of softness than the control, even though both
products are at the same tens;le strength.
As stated hereinbefore, it is also desirable to treat
noncationic surfactant containing tissue pa~er with 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
~et and dry strength additives known in the art. Starch has been
found to be the preferred binder for use in le present invention.
Preferably, the tissue paper is treated Wi~l an aqueous solution
of starch and, also preferably, the sheet is moist at the time of
application. In addition to reducing linting of the finished
tissue paper product, low levels of starch also imparts a modest
improvement in the tensile strength of ~issue paper without
imparting boardiness (i.e., stiffness) which would result from
additions of high levels of starch. Also, this provides tissue
paper having improved strength/softness relationship compared to
tissue paper which has been strengthened by traditional methods
of increasing tensile strength: for exa~ple, sheets having
increased tensile strength due to increased ~efining of the pulp:
~,~ or through the addition of other dry strengt~ additives.
1 328335
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 with a
noncationic surfactant alone. ~his result is especially
surprising since starch has traditionally been used to build
strength at the expense of softness in app1ications wherein
softness is not an important characteristic: for example,
paperboard. Additionally, parenthetically, starch has been used
as a filler for printing and writing 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 ~t is not intended to thereby limit the
scope of suitable starch materials; and waxy 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 - 'he Starch From ~axy
Corn~, H. H. Schopmeyer, Food Industries, December 1945, pp.
106-108 (Vol. pp. 14~6-1478).
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. 40re 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 a~ about l90 F labout
88-C) for between about 30 and about 40 ~inut~s.
, ~. . . ~ .
,, .
1 32833~
26
Other exemplary starch materials ~hich 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
additive to increase wet and/or dry strength. Ho~ever 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 ~hile the
paper is in a moist condition. The starch based material is added
to the tissue paper web, preferably ~hen the web has a fiber
consistency of about 80X or less. Noncationic starch materials
are sufficiently retained in the web to provide an observable
effect on softness at a particular strength level relative to in-
'O creased refining; and, are preferably applied to wet tissue webs
having fiber consistencies between about lOX and about 80X (based
on the weight of the wet web), more preferably, between about 15X
and 35%.
Starch is preferably applied to tlssue 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 ~eb
simultaneously ~ith, prior to, or subse~uent 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 identi~al sheet is preferably
t ~ . ... ;..... ~
~,;..... . . . .. . . ..
.,;~ . . i ..
.. ~; . . . . . . . .
.j...... . . . . . . . .
i....... . , .. . . ~ . .
1 328335
2~
applied to the sheet. Preferably, a sufficient amount of starch
is added such that between about 0.01% and about 2.0X of starch is
retained in the dried sheet, calculated on a dry fiber weight
basisi and, more preferably,.between about 0.1% and about 1.0% of
S 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 level of
nonionic surfactants, such as alk~lglycosides, 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 extract; the level of anionic surfactants, such
as linear alkyl sulfonates, can be detenmined by water extraction
followed by colorimetry analysis of the extract; the level of
starch can be determined by amylase digestion of the starch to
g1ucose followed by colorimetry analysis to determine glucose
level. ~hese methods are exemplary, and are not meant to exclude
other methods which may be useful for determining levels of
particular components retained b~ 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
2~ referred to as "wetting time.~ In order to provide a consistent
and repeatab1e test for ~etting time, the following procedure may
be used for wetting time determinations: first, a dry (greater
than 90% fiber consistency level) sample unit sheet, approximately
4-3/8 inch x 4-3/~ inch (about 11.1 cm x 12 cm) of tissue paper
3~ structure is provided; second, the sheet is folded into four ~4)
juxtaposed quarters, and then crumpled into a ball approximately
Q.75 inches (about 1.9 cm) to about I inch (about 2.5 cm) in
diameter; third, the balled sheet is placed on the surface of a
body of distilled water at ~2-F (about 22-C), and a timer is
;, . , '' "
28 1328335
simultaneously started; fourth, the timer is stopped and read ~hen
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 completely wet in
a relatively short period of time to prevent clogging once the
toilet is flushed. Preferably, wetting ti~e is 2 minutes or less.
More preferably, wetting time is 30 seconds or less. Most
preferably, wetting time is 10 seconds or less.
Hydrophilicit~ characters of tissue paper embodiments of the
present invention may, of course, be deter~ined immediately after
manufacture. Hswever, substantial increases in hydrophobicity may
occur during the first t~o weeks after the tissue paper is made:
i.e., after the paper has aged two (2) weeks following its
manufacture. Thus, the above stated wetting times are preferably
measured at the end of such two week period. Accordingly, wetting
times measured at the end of a two wee~ aging period at room
temperature are referred to as ~two week wet-ing times."
The density of tissue paper, as that t2rm is used herein, is
the average density calculated as the bas s ~eight of that paper
divided by the caliper, with the appr~riate unit conversions
incorporated therein. Caliper of the ~issue paper, as used
herein, is the thickness of the paper ~hen subjected to a
compressive load of 9S g/jn2 (15.5 g/cm2).
The following examples il1ustrate the practice of the present
invention but are not intended to be limiting thereof.
XAMPl ~ I
1 328335
29
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
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 relation
onto the Fourdrinier wire to for~ thereon a three-layer embryonic
web. The level of ~echanical 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 0.11% 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 is assisted by a deflector and vacuum boxes.
The Fourdrinier wire is of a 5-shed, satin weave configuration
having 87 machine-direction and 76 cross-machine-direction mono-
filaments per inch, respectively. The embryonic wet web i5
transferred from the Fourdrinier wire, at a fiber consistency of
about 22% at the point of transfer, to a carrier fabric having a
5-shed satin weave , 35 machine-direction and 33 cross-machine-
direction monofilaments per inch, 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 wet
web has a fiber consistency of about 22% (total web weight basis)
when sprayed by the aqueous, noncationic surfactant solution. The
sprayed web is carried on the carrier fabric past the vacuum
1 328335
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 vacuu~ dewatering box and, by the action of the
S predryers, about 65% prior to transfer onto the Yankee dryer;creping adhesive comprising a 0.25X aqùeous 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. rhe doctor blade has a bevel angle of about 24
degrees and is positioned with respect to the Yankee dryer to
provide an impact 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 minuteJ (about 244 meters per minute). The
dry creped web is then passed bet~een two calender rolls. The
two calender rolls are biased together at roll weight and operated
at surface speeds of 660 fpm labout 201 meters per minute).
The aqueous solution sprayed through the spray nozzle onto
the wet web contains CrodestaTMSL-~0 an alkyl glycoside polyester
nonionic surfactant. The concentration of the nonionic surfactant
in the aqueous solution is adjusted until about 0.l5Z, based upon
the weight of the dry fibers, is retained on the web. The
volumetric flow rate of the aqueous solution through the nozzle is
about 3 gal./hr.-cross-direction ft (about 3~ liters/hr-meter).
The retention rate of the nonionic surfactant applied to the web,
2j in general, is about 90%.
The resulting tissue paper has a basis weight of 30g/m2, a
density of .IOg/cc, and contains 0.15% by weight, of the alkyl
glycoside polyester nonionic surfactant.
The resulting tissue paper is highly wettable and has
enhanced tactile softness.
XAMPL I I
.,~" ~", .. . . .. .
1 328335
~1 .
The purpose of this example is to illustrate 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 be treated with a
noncationic surfactant as described above, also treated
with fully 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.
Concentration of the starch in the aqueous solution is
adjusted so that the level of amioca starch retained is
' 15 about 0.2%, based upon the weight of the dry fibers.
The resulting tissue paper has a basis weight of 30g/m2,
a density of .lOg/cc, and contains 0.15% by weight of
CrodestaTMSL-40 nonionic surfactant and 0.2% by weight
of the cooked amioca starch. Importantly, the resulting
tissue paper has enhanced tactile softness and has
higher tensile strength and lower propensity for lint
than tissue paper treated only with the noncationic
surfactant.
A
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