Note: Descriptions are shown in the official language in which they were submitted.
CA 02288687 2003-02-17
PIGMENTED ADHESIVE COMPOSITION FOR LAMINATING TISSUE PAPER
PRODUCTS AND METHODS FOR PRODUCING SUCH COMPOSITIONS
GELD OF THE jHVENTION
The present invention relates to adhesive compositions for laminating mufti-
ply
cellulosic fibrous structures such as tissue paper products, to methods for
producing
such adhesive compositions, and tissue products laminated using such adhesive
compositions.
Paper products are well known in everyday life. Certain types of paper
products are
referred to as 'tissue, and are used for paper toweling, facial tissue, and
bath tissue.
Tissue paper products may comprise a single ply, but frequently comprise two
or
more plies. As used herein, a "ply" refers to a single sheet taken off a
forming wire,
or the equivalent thereof, and dried without additional fibers 'being added
thereto.
Of course, a ply may be layered with different types of fibers in each layer.
Layering
provides the benefits that a central layer may comprise relatively strong
fibers to
impart strength to the tissue paper product. Outboard of the central layer may
be
shorter fibers which impart a soft tactile sensation to the user. Layering may
be
advantageously accomplished by commonly assigned U.S. Patent 3,994,771, issued
November 30, 1976 to Morgan, Jr. et ai.. .
Frequently, two or more plies are joined together to make a paper product.
Joining
multiple plies together provides the advantage that the resulting laminate has
a lower
bending modulus than a single ply of equivalent thickness. This provides the
benefit
that, again, a softer tactile sensation is perceived by the user. Absorbency
and caliper
are typically improved as well. Furthermore, joining three plies together
allows the
CA 02288687 2003-02-17
7
paper product t.o have different central and outboard plies in the laminate,
to provide
strength and softness respectively.
Mufti-ply tissue products are typically cellulosic. As used herein,
"cellulosic" refers
to a paper product comprising at least about fifty weight percent or at least
about
fifty volume percent cellulosic fibers including, but not limited to, cotton
linters,
rayon, bagasse, and more preferably wood pulps, such as softwoods (gymnosperms
or coniferous) or hardwoods (angiosperms or deciduous), which fibers may be
recycled. The balance of the fibers may be synthetic, such as polyolefin or
polyester.
Cellulosic plies are frequently joined together by the use of an adhesive.
Adhesive
joining of cellulosic plies is advantageously described in commonly assigned
U.S.
Patent 5,143,77b, issued September 1, 1992 to Givens.
However, adhesive joining of multiple cellulosic plies in a paper product can,
and
has, led to unsatisfactory performance. Particularly, paper products used as
paper
toweling, facial tissue, and bath tissue must have the proper ply bond
strength. As
used herein, "ply bond strength" refers to the force necessary to separate two
adjacent plies from one another as described below.
Frequently tissue paper products, particularly paper toweling, are wetted in
use. If
the wet ply bond strength is insufficient, the plies separate in use and the
paper
product is destroyed. While it would seem an easy matter to simply increase
the wet
ply bond strength, the dry ply bond strength is directly coupled to the wet
ply bond
strength. In the prior art, as the wet ply bond strength increases to the
proper level,
the dry ply bond strength becomes too great. When the dry ply bond strength is
too
great, softness and absorbency are typically reduced.
Commonly assigned U.S. Patent 5,858,554 in the names of Neal, et al.
discloses combinations of nonionic adhesive materials that provide dry ply
bond strength to such adhesively joined plies and cationic wet strength resins
that provide wet ply bond strength. Such adhesive compositions have been
found to provide adhesively laminated mufti ply paper.
CA 02288687 2003-02-17
3
products with adequate wet ply bond strength without having a dry ply bond
strength that is too great.
It is also desirable to provide a user with a signal that such laminated paper
toweling maintains its wet ply bond strength when the paper product becomes
wetted during use. As is known in the art, many laminated paper towel
products are provided with an aesthetically pleasing pattern of embossments
with a laminating adhesive being disposed on the distal ends of such
embossments for joining the plies together. It is also known that the pattern
of
~o embossments disappe<~rs when paper toweling becomes wetted. Commonly
assigned I.I.S. Patent 5,834,099 in the names of Steinhardt, et al. discloses
the use of indicator means to maintain a pleasing pattern when paper toweling
becomes wetted. One of the means disclosed therein is a laminating adhesive
further comprising an opacifier, such as titanium dioxide. However, titanium
dioxide pigment dispersions as are commonly available, also typically
comprise an anionic polymer to aid in preventing such dispersions from
flocculating and settling out. Combining such anionically stabilized
dispersions
with cationic wet strength resins as have been found to provide enhanced wet
ply bond strength would result in an adhesive composition that further
2o provides a visual signal of the enhanced wet ply bond strength. However,
the
incompatibility of anionic materials and cationic materials is well known in
the
art.
Thus there is a need for adhesive campositions that also comprise an
2s anionically stabilized pigment dispersion that have improved enhanced wet
ply bond strength. There is also a need for methods of blending anionically
stabilized pigment dispersions and cationic wet strength resins to form such
pigmented adhesive compositions. There is a still further need for pigmented
adhesive compositions having minimal pigment particle agglomeration so as
3o to maximize the opacifying power of such pigmented adhesive compositions
and for methods capable of minimizing such agglomeration.
CA 02288687 2003-02-17
4
The Applicants have discovered certain compositions and methods that
address such needs as will be readily apparent when considered in reference
to the following description and when taken in conjunction with the
accompanying examples.
SUMMARY OF THE INVENTION
The present invention provides an adhesive composition suitable for
laminating a multi-ply cellulosic paper product. The adhesive composition
o comprises a mixture of
(a) from about 2% to about 7% by weight of a water-soluble or water
dispersible dry strength binder material;
(b) from about 0.05% to about 5 % by weight of a water-soluble cationic wet
strength resin;
(c) from about 7% to about 30% by weight of an anionically stabilized
pigment; and
(d) from about 5$% to about 91 % by weight water.
The adhesive composition is preferably manufactured using energizing means
that transfer at least about 5 watts per kilogram to the adhesive composition.
Such transfer provides sufficient energy to the composition as it is being
manufactured, to effectively separate the cationic wet strength resin .and the
anionically stabilized pigment (i.e. the energizing means effectively
maintains
a positive charge density) minimizing agglomeration of the pigment particles
and subsequent adhesive instability (e.g. coacervation~.
All percentages, ratios, and proportions herein are by weight unless otherwise
specified.
In accordance with one embodiment of the present invention, there is
provided an adhesive composition far laminating an absorbent paper product,
CA 02288687 2004-02-24
4a
the adhesive composition comprising:
from about 2% to about 7% by weight of one of a water-soluble dry strength
binder material and a water dispersible dry strength binder material;
from about 0.05% to about 5% by weight of a water soluble, cationic wet
strength resin;
from about 7% to about 30% by weight of pigment particles suspended in the
adhesive composition, the pigment particles having a median particle size;
an anionic dispersion aid for pigment; and
from about 58% to about 91 % by weight water wherein the pigment particles
have a median unsonicated particle size of at most 2.5 times the mean
particle size in a dispersion of pigment alone.
In accordance with another embodiment of the present invention, there is
provided a method for producing a pigmented adhesive composition, said
method comprising the steps of:
a) providing an aqueous solution or dispersion of a wet strength
resin;
b) providing energizing means wherein said energizing means has
a capability of transferring at least 5 watts per kilogram of power
to said first resin solution or dispersion;
c) energizing said wet strength resin solution or dispersion with
said energizing means;
d) providing an aqueous dispersion of pigment particles, said
pigment particles having a mean particle size;
CA 02288687 2004-02-24
4b
e) mixing said pigment dispersion into said wet strength resin
solution or dispersion using said energizing means;
f) providing an aqueous solution or dispersion of a dry strength
binder; and
g) mixing said dry strength binder solution or dispersion into said
mixture of said wet strength resin solution with said pigment
dispersion using said energizing means to form said pigmented
adhesive composition, wherein the median unsonicated particle
size of said pigment particles in said pigmented adhesive
composition is at most 2.5 times the median unsonicated
particle size of said pigment particles in said pigment dispersion.
The present invention is described in more detail below.
DETAILED DESCRIPTION OF THE INVENTION
While this specification concludes with claims particularly pointing out and
distinctly claiming the subject matter regarded as the invention, it is
believed
that the
CA 02288687 2003-02-17
~J
invention can be better understood from a reading of the following detailed
description and of the appended example.
As used herein, the term "comprising" means that the various components,
ingredients, or steps, can be conjointly employed in practicing the present
invention. Accordingly, the term "comprising" encompasses the more
restrictive terms "consisting essentially of" and "consisting of .
The present invention comprises pigmented adhesive compositions that are
o suitable for joining two or more plies of tissue so as to maximize the
opacifying properties of the pigment, methods for producing such
compositions, and paper products laminated using such compositions. The
plies are cellulosic, as described below, and may be made according to the
same manufacturing process, or according to different manufacturing
processes.
The Flies
Each ply may have a plurality of embossments protruding outwardly from the
2o plane of the ply towards an adjacent ply. The adjacent ply likewise may
have
opposing protuberances protruding towards the first ply. If a three ply paper
product is desired, the central ply may have embossments extending
outwardly in both directions, although a central ply having no embossments or
unidirectional embossments may be feasible.
The plies may be made according to commonly assigned U.S. Patents
4,637,859, issued January 20, 1987 to Trokhan or 4,191,609, issued March 4,
1980 to Trokhan. Alternatively, the plies may be made using the uncreped,
through air dried technology described in European Patent Application
0 617 164 A1, published on September 28, 1994 or conventionally dried using
felts as is known in the art.
For the present invention, each ply may have a basis weight of about 8 to
about 30 pounds per 3,000 square feet (13 to 48 g/m2), and preferably
between about 11 and about 18 pounds per 3,000 square feet (18 and 29
g/m2), and preferably has a
CA 02288687 2003-02-17
composition of hardwood andlor softwood processed by any of the means well
known in the art.
The fibers comprising the plies of the paper product are preferably
cellulosic, such
as cotton linters, rayon or bagasse; and more preferably are wood pulp, such
as soft
woods (gymnosperms or coniferous) or hard woods (angiosperms or deciduous). As
used herein, a laminated paper product is considered "cellulosic" if the
laminated
paper product comprises at least about 50 weight percent or at least about SO
volume
percent cellulosic fibers, including but not limited to those fibers listed.
above. The
balance of the fibers comprising the laminated paper product may be synthetic,
such
as polyolefin or polyester. A cellulosic mixture of wood pulp fibers
comprising
softwood fibers having a length of about 2.0 to about 4.5 millimeters and a
diameter
of about 25 to about 50 micrometers, and hardwood fibers having a length of
less
than about 1.7 millimeters and a diameter of about 12 to about 25 micrometers
has
been found to work well for the laminated paper products described herein.
If wood pulp fibers are selected for the multi-ply paper products of the
present
invention, the fibers may be produced by any pulping process including
chemical
processes, such as sulfite, sulfate and soda processes; and mechanical
processes such
as stone groundwood. Alternatively, the fibers may be produced by combinations
of
chemical and mechanical processes or the fibers may be produced by a process
which recycles waste paper products. The type, combination, and processing of
the
fibers used are not critical to the present invention. The hardwood and
softwood
fibers may be layered throughout the thickness of the laminated paper products
or
homogeneously blended therein.
The Adhesive Com osp itian
The plies of the mufti-piy paper product are adhesively joined together using
a
pigmented adhesive composition prepared according to the present invention.
The
adhesive composition is preferably applied to the embossments of at least one
ply.
Of course, the adhesive can be applied to the embossments of both plies. An
adhesive according to the present invention comprises a mixture of a dry
strength
binder (e.g., a fully hydrolyzed polyvinyl alcohol adhesive), a cationic wet
strength
CA 02288687 1999-11-09
WO 98/50482 PCT/US98/09149
7
resin (e.g., a thermosetting cationic resin), and an anionically stabilized
titanium
dioxide slurry. A particularly preferred adhesive composition comprises
between
about 58 and about 90 parts water, 2 to 7 parts dry strength binder solids,
0.05 to 5
parts cationic wet strength resin solids, and 7 to 30 parts titanium dioxide
pigment.
Each of these types of compounds will be described in detail below.
Importantly, to achieve satisfactory wet and dry ply bond strength and
satisfactory
signal intensity in the finished laminated tissue product of the present
invention, the
adhesive composition must be delivered to the plies at an appropriate level.
Suitable
delivery methods are discussed in the Ply Embossing and Lamination section
below.
It is also important that the components of the adhesive composition be
delivered in
the right proportions. One of skill in the art will recognize that the
absolute
concentrations of the solid components of the composition can be varied within
certain limits (e.g. to control viscosity of the composition) as long as the
adhesive
solids delivered to the plies are sufficient to provide satisfactory wet and
dry ply
bond strength and satisfactory signal intensity. Specifically, it is important
that the
ratio of dry strength binder solids to cationic wet strength resin solids be
within an
acceptable range so as to provide adequate wet ply bond strength without
having a
dry ply bond strength that is too great. It is also important that the ratio
of
cationically charged material solids to anionically charged material solids be
within
an acceptable range so as to provide stable adhesive compositions having
sufficient
signal intensity.
Specifically, the Applicants have found that:
1 ) The ratio of dry strength binder solids to wet strength resin solids
should not
exceed about 6:1 in order to have an acceptable balance between wet ply bond
strength and dry ply bond strength. Preferably, the ratio is less than about
4:1.
2) The ratio of anionically charged material solids to canonically charged
material solids should be such that the charge density of the final adhesive
composition is at least about 25 microequivalents per gram (as will be
recognized by
those having skill in the art, the specific weight ratios will depend on the
charge
density of the individual materials). For the preferred materials discussed
herein, this
CA 02288687 2003-02-17
8
means the ratio of anie .ically charged pigment solids (pigment solids plus
anionic
suspension aid solids) to cationic solids (wet strength resin solids or other
canonically charged solids added to maintain a net positive charge density)
should
be less than about 40:1. Preferably, the ratio of anionic solids to cationic
solids is
less than about 30:1. More preferably, the ratio is less than about 15:1.
Drv strength Binder Materials
The adhesive composition of the present invention contains as an essential
component from about 2% to about 7%, preferably from about 3.5% to about 6.5%
by weight of a dry strength binder material chosen from the following group of
TM
materials: polyacrylam~ae (such as Accostrength 711 produced by CyTec
Industries
'TM
of West Patersan, NJ); starch (such as Redi$OND 5320, 2005, and 3030)
available
TM
from National Starch and Chemical Company, Bridgewater, NJ, or Amylose 1100,
TM
2200 or Salvitose available from Avebe America, Princeton, NJ; polyvinyl
alcohol
TM
(such as Evanol 71-30, supplied by the DuPont Corporation of Wilmington, DE);
and/or guar or locust bean gums. Preferably, the dry strength binder materials
are
selected from the group consisting of polyvinyl alcohol, starch based resins,
and
mixtures thereof. The dry strength binder materials act to ensure that the
multi-ply
paper products of the present invention have adequate dry ply bond strength.
In particularly preferred adhesive compositions according to the present
invention,
the dry strength binder comprises polyvinyl alcohol. The polyvinyl alcohol
cpmponent can be of any water-soluble nr water-dispersible molecular weight
,sufficient to form an adhesive film. Generally, a weight average molecular
weight of
from about 40,000 to about 120,000, more preferably from 70,000 to 90,000 is
preferred. Polyvinyl alcohol in solid form is commercially available under
several
trademarks such as ELVANOL~ (DuPont), GELVATOL~ (Monsanto) VINOL~ (Air
Products) and POVAL~ (KLIRARAY). These grades have a degree of hydrolysis
ranging from about 80 to about l00%. Those skilled in the art will appreciate
that
lowering the degree of hydrolysis and the molecular weight will improv<: water
solubility but will reduce adhesion. Therefore the properties of the polyvinyl
alcohol
will have to be optimized for the specific application. A particularly
preferred
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WO 98/50482 PCT/US98/09149
9
polyvinyl alcohol is Evanol 71-30, supplied by the DuPont Corporation of
Wilmington, DE. Evanol 71-30 has a weight average molecular weight of about
77,000 and degree of hydrolysis of about 99%.
Alternatively, the dry strength binder can comprise a starch. In general, a
suitable
starch for practicing the present invention is characterized by water
solubility or the
ability to form stable dispersions that are hydrophilic. Exemplary starch
materials
include corn starch and potato starch, albeit it is not intended to thereby
limit the
scope of suitable starch materials. Waxy corn starch that is known
industrially as
amioca starch is preferred. Amioca starch differs from common corn starch in
that it
is entirely amyiopectin, whereas common corn starch contains both amplopectin
and
amylose. Various unique characteristics of amioca starch are further described
in
"Amioca - The Starch from Waxy Corn", H. I-I. Schopmeyer, Food Industries,
December 1945, pp. 106-108 (Vol. pp. 1476-1478}. The starch can be in granular
or
dispersed form. One preferred starch, RediBOND, comes as a dispersed ready to
use
material. Granular starches such as Amylose 1100 are 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 190 °F (about 88
°C) for between
about 30 and about 40 minutes. Other exemplary starch materials which may be
used
include modified cationic or anionic 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,
NJ).
Considering that such modified starch materials are more expensive than
unmodified
starches, the latter have generally been preferred.
CA 02288687 1999-11-09
WO 98/50482 PCT/US98109149
Wet Strength Resin Materials
The adhesive composition of the present invention also contains as an
essential
component from about 0.05% to about 5.0%, preferably from about 0.1% to about
2.5% by weight of a wet strength resin material chosen from the following
group of
materials: polyamide-epichlorohydrin resins, glyoxalatcd polyacrylamides
resins,
styrene-butadiene latexes; insolubilized polyvinyl alcohol; urea-formaldehyde;
polyethyleneimine; chitosan polymers and mixtures thereof. Preferably, the wet
strength resins are water-soluble cationic resins selected from the group
consisting of
polyamide-epichlorohydrin resins, glyoxalated polyacrylamide resins,
polyethyleneimine resins, and mixtures thereof.
Polyamide-epichlorohydrin resins axe cationic wet strength resins which have
been
found to be of particular utility. Preferably, the polyamide-epichlorohydrin
resin
comprises a water-soluble polymeric reaction product of epichlorohydrin, and a
water-soluble polyamide having secondary amine groups. The ratio of
epichlorohydrin to secondary amine groups of said polyamide is preferably from
about 0.5 to 1 to about 2 to 1. Preferably, the water-soluble polyamide is
derived
from reacting a polyalkylene polyamine and a saturated aliphatic dibasic
carboxylic
acid containing from about 3 to 10 carbon atoms. Preferably the mole ratio of
polyalkylene to dibasic carboxylic acid is from about 0.8 to 1 to about 1.5 to
1.
Preferably the saturated aliphatic dibasic carboxylic acid is adipic acid and
the
polyakylene polyamine is diethylene triamine. Most preferably, the water-
soluble
polyamide contains recurring groups of the formula
O O
II II
- N(C°H~nHN),~- CRC
wherein n and x are each 2 or more and R is the divalent hydrocarbon radical
of the
dibasic carboxylic acid containing from about 3 to 10 carbon atoms. Resins of
this
type are commercially available under the trademarks KYMENE~"' (Hercules,
Inc.)
and CASCAMID~ (Borden). An essential characteristic of these resins is that
they
are phase compatible with the polyvinyl alcohol, i.e., they do not phase-
separate in
the presence of aqueous polyvinyl alcohol.
CA 02288687 2003-02-17
11
Suitable types of such resins are described in U.S. Patent No. 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 resin is Hercules, Inc. of Wilmington, DE, which markets such
resins under the tradernarks Kymene~ 557H KymeneQ 557LX, and Kymene~
557ULX, with Kymene~ 557LX being preferred.
Base-activated polyamide-epichlorohydrin resins which are also useful in the
present invention are also sold by Hercules, Inc. of Wilmington, DE, which
markets such resin under the trademark Kymene~ 450. Other examples of
commercial sources of base-activated polyamide-epichlorohydrin resins are
sold under the Santo Res trademark, such as Santo Res 31, by Monsanto
Company of St. Louis, MO. These types of materials are generally described
in U.S. Patent Nos. 3,855,158 issued to Petrovich on December 17, 1974;
~5 3,899,388 issued to Petrovich on August 12, 1975; 4,129,528 issued to
Petrovich on December 12, 1978; 4,147,586 issued to Petrovich on April 3,
1979; and 4,222,921 issued to Van Eenam on September 16, 1980.
Glyoxalated polyacrylamide resins have also been found to be of utility as wet
2o strength resins. These resins are described in U.S. Patent No. 3,556,932,
issued on January 19, 1971, to Coscia, et al. and 3,556,933, issued on
January 19, 1971, to Williams et al. One commercial source of
polyacrylamide resins is Cytec of Stanford, CT, which markets one such resin
under the trademark Parezr"~ 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.
3o Polyethylenimine type resins may also find utility in the present
invention.
CA 02288687 2003-02-17
12
Pigment
As discussed in the Background of the Invention section above, it is desirable
to provide a user with an indication that desirable properties, such as wet
ply
bond strength, are maintained when adhesively laminated paper products are
wetted. Also as noted above and described in aforementioned U.S. Patent
5,834,099, laminating adhesive compositions comprising a pigment can
provide such a signal.
As is well known, refractive index is one major factor determining thE:
opacifying efficiency of a pigment. Table 1 below compares the refractive
index of pigments commonly used in the paper industry.
Table I
~5 Compound Refractive Index
Titanium Diaxide
Rutile 2.72
Anatase 2.55
Zinc Oxide 2.02
Kaolin Clays
Filler 1.57
Calcined 1.57
Calcium Carbonate
Natural Ground 1.56
3o PCC-Calcite 1.66
Talc 1.57
Precipitated Silica 1.45
s5 To be suitable for use as a pigment for purposes of the present invention,
such inorganic pigmenting materials should have a refractive index greater
than about 1.4. Preferably, the refractive index is greater than about 1.7.
Particularly preferred inorganic pigmenting materials have a refractive index
greater than about 2Ø
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WO 98/50482 PCTNS98/09149
13
In addition to refractive index, the particle size of an opacifier also has a
major effect
on the opacity of the adhesive compositions of the present invention. That is,
for a
given concentration of pigment in an adhesive composition, compositions
comprising pigments having a smaller particle size will be more opaque.
Pigments
suitable for use in the present invention have a median, unsonicated particle
size less
than about 1.4 microns. Preferably, the median particle size is less than
about 0.8
microns. More preferably, the median particle size is less than about 0.6
microns. A
method for measuring median unsonicated particle size is given in the TEST
METHODS section below.
A particularly preferred pigmenting material is titanium dioxide (Ti02}. Two
crystalline forms of Ti02 exist: anatase and ruble. The rutile form is the
most
opaque due to its higher refractive index. In the papermaking art it is known
that a
given opacity can typically be achieved with about 15-20% less rutile than
anatase.
Titanium dioxide is commercially available in both a dry powder form and as a
slurry in water. For purposes of the present invention, the water slurry form
is
preferred because of ease of mixing with other components of the present
adhesive
composition and because the pigment particles are more fully dispersed so as
to
provide better opacity.
In order that Ti02 remain suspended, additional components are included in
commercially available TiO~ slurries. In particular, dispersion aids are used
to insure
that suspended Ti02 particles do not flocculate and settle out. Dispersion
aids are of
two types: stearic stabilizers and electrostatic stabilizers. Stearic
stabilizers surround
the suspended Ti02 particles with an adsorbed layer of a polymer. Stearic
interaction between the polymer layers on different particles prevents the
particles
from approaching closely enough such that they can agglomerate. Typically,
stearically stabilized slurries are quite viscous because of the adsorbed
layer of
polymer. Titanium dioxide particles also can be stabilized electrostatically
by
surrounding them with a charged species. Such species can be either cationic
or
anionic. Because most Ti02 is used by the paint and paper industries which
both
require anionic slurries for their processes, cationic Ti02 slurries are
uncommon. An
example of a suitable anionic electrostatic suspension aid is the sodium
polyacrylate
CA 02288687 2003-02-17
14
described in U.S. Patent 4.503,172, issued in the name of Farrar. et al. on
March ~.
TM
1985. Such a material is available as Dispex N40V manufactured by from Allied
Colloids of Suffolk, VA.
A suitable, commercially available Ti02 slurry is Ti-Pure RPS Vantage Rutile
Paper Slurry which is available from the DuPont Company of Wilmington, DE.
This
material is an anionically stabilized slurry of the rutile form of Ti02 in
water having
a nominal Ti02 solids level of ~I.S%. The median unsonicated particle size of
this
material is typically less than 0.5 microns.
Such a Ti02 slurry has been found to provide a visual signal of desirable wet
in use
properties when the Ti02 pigment is used according to the present invention.
The
Applicants have found that pigmented adhesive compositions according to the
present invention should comprise at least about 7% Ti02 solids to provide a
satisfactory visual signal of desirable wet properties. Ti02 solids levels
greater than
about 30% provide no additional improvement in signal intensity. Preferably,
the
TiO~ solids level should be between about 10% and about 30%. More preferably,
the Ti02 solids level is between about 15% and about 25%. One of skill in the
art
will recognize that, if other pigments are used, the level of pigment will
need to be
adjusted to provide a satisfactory visual signal. As noted above, relative
refractive
index between Ti02 and a potential replacement pigment can provide an initial
indication of how great an adjustment is needed.
TM
Alternatively, organic pigmenting means, such as Ropaque HP91 from Rohm &
fiaas Corp., Philadelphia, PA, may be used to replace at least part of the
titanium
dioxide. Such organic pigmenting means are hollow polymeric spheres that are
provided as a water emulsion. Since the spheres are hollow, light is bent
multiple
times as it passes through a dispersion of such pigments. This multiple
bending
provides an apparent refractive index that provides hiding power comparable to
Ti02. Since, such organic pigmenting means are also anionically stabilized,
the
same issues of incompatibility with cationic wet strength resins that are
discussed
above also affect the stability and opacity of adhesive compositions
comprising
organic pigmenting means.
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An alternative inorganic pigmenting means that may be used as a substitute for
at
least part of the titanium dioxide in adhesive compositions of the present
invention
is silica (e. g. fumed silica, colloidal silica, and the like). A suitable
fumed silica is
AEROSIL 300' which is available from Degussa Corp. of Ridgefield Park, NJ. As
is clearly evident from Example 5, pigmented adhesive compositions comprising
such alternative inorganic pigmenting means provide desirable turbidity and
viscosity as are dscussed above. The Applicants further believe that replacing
part of
the titanium dioxide with silica has the potential to reduce wear in adhesive
compounding and application apparatus because of the small ultimate particle
size
of the silica particles. For example, the AEROSIL 300~ discussed above has an
ultimate particle size of 7 nanometers compared to 0.5 microns for the TiO~
pigment discussed above.
Optional Cationic Additives
As is well known cationic species carry a positive charge and anionic species
carry a
negative charge. One measure of such charges is charge density. A method for
measuring charge density is provided in the TEST METHODS section below. The
Applicants have found that suitable adhesive compositions according to the
present
invention should have a positive charge density. That is, a suitable adhesive
composition according to the present invention is at least slightly cationic
(positive
charge density). The Applicants believe that one of the benefits of the method
of the
present invention is that energizing one of the anionic or the cationic
components of
the composition before beginning to add the other component prevents a
situation
wherein portions of the blend have a negative charge density during addition
of the
remaining charged components of the composition (Such negative charge density,
when the components are mixed under low energy conditions, has been found to
increase the risk of coacervation, separation and loss of opacifier
efficiency). By
providing sufficient energy to the mixing step, formation of substantial
portions of
the blend having a negative charge density and the resulting coacervation are
significantly reduced.
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16
Table 2 lists charge density values for representative components suitable for
use in
the adhesive composition of the present invention.
Table 2
Component Charce density
(Microequivalents/gram
Cationic Materials
Kymene~' 557 LX
RediBond~ 5320 +3243
Anionic Material +264
Ti02 Slurry (Ti-Pure~ RPS)
-48
* 100% solids basis
The relative amounts of such components in a composition will determine the
charge
density of the composition. For example, a composition comprising about 1.5%
Kymene 557LX and about 23% Ti02 prepared according to the method of the
present invention has been found to have a charge density of about +185
microequivalents per gram. On the other hand, a composition comprising about
0.3% Kymene 557LX and about 23% Ti02 has been found to have a charge density
of about -1.7 microequivalents per gram. Preferably, the charge density in the
finished pigmented adhesive composition is at least about +25 microequivalents
per
gram of dispersed solid material. Preferably, the charge density is at least
about +30
microequivalents per gram, more preferably, at least about +50
microequivalents per
gram.
As will be discussed below, the method of the present invention is
particularly
efficient in minimizing pigment agglomeration in pigmented adhesive
compositions
prepared thereby. However, it is still necessary to maintain a minimum
positive
charge density in the finished adhesive composition so as to maximize
stability of
the composition. For example, a particular adhesive composition may not
comprise
enough cationic wet strength resin to maintain a positive charge density which
increases the risk of coacervation and agglomeration. To compensate for such
CA 02288687 2003-02-17
17
insufficient positive charge density, materials having a positive charge
density (i. e.
cationic additives) may he added to the composition. if the charge density
contribution from cationic materials in the composition is insufficient.
Suitable
TM
materials include: cationic starches (such as Celquat L200 as is available
from
National starch and Chemical Co. of Bridgewater, NJ) and quaternary ammonium
compounds (such as are available from Witco Chemical Co. of Dublin, OH as DP-
SC-505-91). A particularly preferred cationic additive is a relatively low
molecular
weight polyamine having a high charge density. A particularly preferred
material of
this type is Cypro~ 515 which has a charge density of about +6400
microequivalents
' per gram (100% solids basis) and is available from Cytec of Stamford, CT as.
For
example, when 0.6% Cypro°' 515 is added to a 0.3% Kymene~ 557 LX
solution prior
to addition of the, Ti02, the composition, afrer addition of the Ti02, has a
charge
density of ~+35 microequivalents per gram rather than -1.7 microequivalents
per
gram described above. Such a charge density has been found to provide an
adequately stable suspension for use as a laminating adhesive.
Adhesive Manufacture
As noted above, a preferred wet strength resin, Kymene~~, is highly cationic
and,
therefore, when Kymene~ is combined with anionically stabilized TiO~ slurries
it
can .react with anionic components of the adhesive composition. such as an
anionically stabilized pigment dispersion, causing stratification and
separation of the
adhesive composition due to coacervation. Example 1 below demonstrates this
behavior.
Surprisingly, the Applicants have found that, by appropriately blending the
above
identified components, the well known difficulties of producing stable
compositions
combining cationic and anionic materials can be overcome.
Specifically, the Applicants have found that by using the method described in
detail
below, wherein one of the anionic or the cationic component of the composition
is
energized before the other of the camponents are added, remarkably stable
pigmented adhesive compositions can be produced. A liquid material is
"energized"
if an "energizing means" is capable of providing at least about 5 watts per
kilogram
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18
as the liquids are being blended. Preferably, the energizing means should be
capable
of delivering at least about 15 watts per kilogram as the liquids are being
blended.
More preferably, the energizing means is capable of delivering at least about
25
watts per kilogram as the liquids are being blended. A method of determining
the
energy delivered (watts per kilogram) is provided in the TEST METHODS section.
Suitable energizing means include: batch mixers providing a high agitator tip
speed,
for example blenders as are available from Sunbeam Corp. of Delray Beach, FL
with
the brand name Osterizer; rotor/stator high shear mixers, as are available
from
Charles Ross & Son, Hauppauge, NY; and in line mixers such as are available
from
Quadro Inc., Millburn, NJ as model Quadro ZC. A particularly preferred
energizing
means is the Breddo Likwifier, Model LOR as supplied by Breddo Likwifier of
Kansas City, MO.
Further, the Applicants have found that, when such methods are used, the
median
particle size of the pigment in the finished adhesive composition is
comparable to
the median unsonicated particle size of the pigment in the original pigment
dispersion. That is, the method of the present invention utilizes such pigment
dispersions in a highly efficient manner so as to provide the adhesive
composition
with maximum opacity.
This efficiency is shown very clearly in Table 3 which compares the turbidity
(turbidity is a measure of opacity-a method to measure turbidity is provided
in
TEST METHODS section) of pigmented adhesive compositions prepared according
to the methods described in Examples 1 and 2 below.
Table 3
Median Unsonicated
Turbiditv Particle Size
(NTU) (microns)
Composition prepared 1217' Two peaks (2.2,
according to method of 17. I )
Example 1
Composition prepared accord- 3467' 0.5
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ing to method of Example 2
*Measured at a concentration of 0.5 grams of adhesive in 1000 milliliters of
water
As can be clearly seen, the adhesive composition prepared according to the
method
of Example 2 (method of the present invention) has a substantially higher
turbidity
(greater opacity) and lower median particle size than the adhesive composition
prepared according to the method of Example 1 (low energy mixing).
Without being bound by theory, the Applicants believe that energizing one of
the
charged components of the composition prior to adding the component having the
opposite charge keeps the pigment particles sufficiently separated so that
agglomeration of pigment particles (with the resulting increase in mean
pigment
particle size) is minimized. The Applicants have found that, when pigmented
adhesive compositions are prepared according to the present invention, the
pigment
particles in such compositions have a mean unsonicated particle size no
greater than
about 2.5 times the mean unsonicated particle size of the pigment in the
pigment
dispersion. Typically, the mean unsonicated particle size of the pigment in
the
pigmented adhesive composition is less than about 1.5 times the mean
unsonicated
particle size of the pigment in the pigment dispersion. The Applicants further
believe
that providing sufficient mechanical energy while the second component is
being
added to the first minimizes interactions between anionic and cationic
species. That
is, coacervation, and the resulting substantial increase in the viscosity of
the
composition (i. e., stratification and gelling), is minimized.
While, as noted above, energizing a first component of the adhesive
composition
prior to adding any of the other components meaningfully minimizes
coacervation
and pigment particle agglomeration, addition order can affect the properties
of the
final adhesive composition. The following describes a particularly preferred
method
of preparing the adhesive compositions of the present invention.
The first step of this preferred method is to provide the requisite quantity
of a
suitable cationic wet strength resin. For example to prepare 100 parts of the
preferred adhesive compositions of the preset invention between about 0.05
parts
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and about 5 parts of a polyamide-epichlorohydrin resin may be provided.
Preferably,
this resin is in a solution comprising between about 10 % by weight and about
15
by weight resin solids. A particularly preferred method provides about 12
parts of a
12.5 % by weight a polyamide-epichlorohydrin resin solution. Optionally, if
the
desired concentration of cationic wet strength resin is too low to maintain a
suitable
charge density (see discussion above), one of the alternative cationic
materials
discussed above may be provided prior to energizing the cationic wet strength
resin
solution.
This polyamide-epichlorohydrin resin solution is then energized by suitable
means
of providing mechanical energy thereto as described above. It is important
that
sufficient energy be provided by this energizing step cause the resin solution
to
become turbulent. For example, the resin solution should not be so highly
viscous
that a substantial portion of the mechanical energy provided is converted into
thermal energy causing the temperature of the solution to rise substantially.
Specifically, the viscosity of the resin solution should be less than about
500
centipoise when measured according the method described in the TEST METHODS
section below. More preferably, the viscosity should be less than about 300
centipoise.
As noted above, suitable energizing means are capable of providing at least
about 5
watts per kilogram of energy to the resin solution provided by the first step.
A
particularly preferred energizing means for purposes of the present invention
is the
Breddo Likwifier, Model LOR.
After energizing the cationic wet strength resin solution, the pigment
dispersion is
added thereto. To produce 100 parts of the preferred pigmented adhesive
composition described above between about 7 and about 30 parts of the pigment
dispersion are added while continuing to provide energy to the liquid. For the
particularly preferred Ti02 dispersion discussed above, about 32 parts of the
71.5
percent by weight dispersion are added.
Preferably, the pigment dispersion is added at a rate so as to insure that the
bulk of
the material in the mixing zone comprises the cationic wet strength solution
or a
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21
dispersion of pigment in the cationic wet strength resin solution. Otherwise,
there
may be insufficient energy to maintain separation of the pigment particles and
minimize coacervation. As used herein, the term "mixing zone" is determined by
the
geometry of specific energizing means chosen and is that volume where energy
is
transferred from the energizing means to the liquid or dispersion being
energized.
The Applicants have found that a useful measure of addition rate is a Delivery
Number. As used herein "Delivery Number" is a dimensionless number which
depends on the addition rate of pigment dispersion, the geometry of the
agitator, and
the rotational velocity of the agitator and can be calculated according to the
following equation:
~_ PigWt __
Q - AddnTime
nd3P
_ RotVcl
where:
Q = Delivery Number
PigWt = Weight of pigment dispersion added (Kg)
AddnTime = Time required to add pigment (seconds)
r = Pigment dispersion density (g/cm3)
RotVel = Rotational velocity of agitator (rpm)
d = Diameter of agitator (cm)
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For example, in preparing a batch of the pigmented adhesive composition of the
present invention the following data were taken:
PigWt = 36.97 Kg;
AddnTime = 240 seconds
r = 2.2 g/cc (TiOz slurry, comprising about 72% Ti02 solids)
RotVel = 1800 rpm
d = 24.3 cm
The resulting Delivery Number is 1.63X10-'. As can be seen from Example 3,
such a
Delivery Number indicates that the pigment dispersion was added to the mixing
zone sufficiently slowly to prevent agglomeration (i.e. the median unsonicated
particle size is substantially less than 1 micron).
The last required step in this preferred method is to add the dry strength
binder
solution (still continuing to provide energy to the liquid). The dry strength
binder
solution is preferably added after the other components because such solutions
typically have a high viscosity and energizing such solutions without an
unacceptable temperature increase is difficult. As noted above, the dry
strength
binder solution preferably comprises a starch based resin or polyvinyl alcohol
in
water. Preferably, the concentration of dry strength binder in such a water
solution is
between about 2% and about 14% and between about 2 and about 7 parts of binder
solids are added to the adhesive composition when preparing 100 parts of the
finished adhesive composition.
Optionally, other components may be added after blending the above materials.
For
example, a portion of dilution water could be held back to allow for final
viscosity
and solids level control to compensate for lot to lot variation in the
individual raw
materials.
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Alternative Adhesive Manufacturing Methods
Addition Order
While the method described above is preferred because it provides maximum
dispersion of the pigment particles and minimizes particle agglomeration,
alternative
methods, particularly alternative addition orders, are also within the scope
of the
present invention. For example, an addition order comprising the following
steps: 1 )
providing a dry strength binder solution; 2) energizing the dry strength
binder
solution; 3) providing an anionically stabilized pigment dispersion; 4) mixing
the
pigment dispersion into the dry strength binder solution to form a pigmented
binder
blend; 5) providing a cationic wet strength resin solution; and 6) mixing the
wet
strength resin solution into the pigmented binder blend is also contemplated
by the
Applicants. Pigmented adhesive compositions prepared according to this
alternative
method have substantially improved opacity, agglomeration reduction and
stability
when compared to Iow energy mixing methods. Specifically, the median
unsonicated
particle size for an adhesive composition comprising the preferred Ti02
pigment
discussed above is about 1.0 microns and the initial separation time is
greater than
24 hours. When these results are compared to the results shown in Table 2
above the
improvement over the low energy mixing method of Example I is obvious.
Energizing Means
An alternative energizing means, suitable for purposes of the present
invention, is a
mixer that provides energy to a liquid medium by forming ultrasonic vibrations
therein (A suitable apparatus is produced by Sonic Corp. of Stratford, CT as
the
Sonolator). The Sonolator is an in-line system that provides ultrasonic
vibrations by
pumping a liquid, a blend of liquids, or a solid dispersion in a liquid
through a
shaped orifice at a high linear velocity. The liquid stream impinges against a
blade
cantilevered in the stream. Flow over the blade causes vibrations in the blade
which
produces cavitation in the stream converting flow energy into
mixing/dispersion
energy.
CA 02288687 2004-02-24
24
After the papermaking process which forms a ply is complete, one or snore
plies may
be embossed and laminated. Embossing/lamination is one means of obtaining a
pattern that is useful in providing a visual indication of desirable
properties when the
embossing/lamination steps are carried out using the pigmented adhesive
composition of the present invention.
Embossing may be accomplished according to the knob-to-knob embossing process
illustrated by commonly assigned U.S. Patent 3,414,459, issued December 3,1968
to
Wells; the nested embossing process illustrated in U.S. Patent 3,556,907,
issued
January 19, 1971 to Nystrand; or a dual ply process illustrated in commonly
assigned U.S. Patent 5,294,475, issued March 15, 1994 to McNeil.
For the embodiments described and claimed herein, the embossments may be
spaced
on a pitch of 0.05 to 0.70 inches and may have an area at the distal end
ranging from
0.001 to 0.100 square inches. Each embossment may be made on a roll having
knobs
which protrude 0 to 0.120 inches from the plane of the roll. The embossments
may
be round, oval shaped, or irregularly shaped.
Each of the embossments has a distal end and the adhesive composition of the
present invention is applied at least a portion of the distal ends to form a
laminated
tissue product according to the present invention. Preferably the adhesive
solids are
applied at a rate of between about 12 and about 20 pounds of adhesive solids
per ton
paper (6 to 10 grams of adhesive solids per kilogram of paper) of to at least
some of
the distal ends on at least one of the tissue plies to form the laminated
tissue product.
More preferably between about 14 pounds of adhesive solids per ton of paper
and
about 18 pounds of adhesive solids per ton of paper (7 grams per kilogram to 9
grams per kilogram) are applied. As used herein, the term "adhesive solids" is
intended to mean the nonaqueous components of the adhesive composition of the
present invention and includes wet strength resins dry strength additives,
Ti02, and
any dispersion aids or other solid materials that may be added to the adhesive
composition.
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A particularly preferred method of embossing and laminating a to produce
laminated
tissue products according tot he present invention is described in Example 4.
The Applicants believe that the following non-limiting examples are
illustrative of
the present invention.
EXAMPLES
Example 1
This example is intended to illustrate the properties of a coacervated mixture
of a
cationic wet strength resin, and anionically stabilized pigment dispersion and
a dry
strength binder solution made using a conventional mixing method.
A pigmented adhesive composition was prepared according to the following
method:
1 ) provide about 13 parts of a cationic wet strength resin solution
comprising about
12.5% Kymene ~' S57LX resin solids and having a pH of about 3.0; 2) begin
agitation of the wet strength resin solution using a Lightnin Model TS2010
mixer,
which is available from Lightnin of Rochester, NY. Such a mixer provides about
1.7
watts per kilogram of power to the solution; 3) with continued agitation add
about
23 parts of a 72% solids Ti02 dispersion (Ti-Pure~ RPS Vantage Rutile Paper
Slurry from DuPont) having a pH of about 8.4; 4) add about 64 parts of a dry
strength additive (ELVANOL 71-30 from DuPont) solution having about 7.4% resin
solids with continued mixing; and 5) add water as necessary with continued
mixing
to provide 100 parts.
Table 4 lists property data obtained on evaluation of this adhesive
composition.
Table 4
Pr~-ty Value
pH 4.3
Median Unsonicated Particle Size (p)
First Peak 17.1
Second Peak 2.2
Turbidity~ 1217
Initial Separation Time 4 Hours
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26
*Measured at a concentration of 0.5 grams of adhesive in 1000 milliliters of
water
Example 2
This example uses the same materials, concentrations, and addition order as
Example 1 but uses the method of the present invention to provide a pigmented
laminating adhesive composition suitable for joining two or more plies of
tissue
paper. Specifically, a laboratory blender (Osterizer as is available from
Sunbeam
Corp. of Delray Beach FL) was used which energizes the liquid with about 110
watts per kilogram.
Table 5 lists property data obtained on evaluation of this adhesive
composition.
Table 5
Property Value
pH 4.3
Median Unsonicated Particle Size (p.) 0.5
Turbidity 3467
Initial Separation Time >4 Weeks
Example 3
This example is intended to demonstrate the use of commercial scale mixing
equipment to prepare pigmented adhesive compositions according to the present
invention.
Apparatus:
Mixer Breddo Likwifier, Model LOR, Size 50 gallon, 30 Hp motor"
adjustable speed (640-2300 rpm) as is available from Breddo Likwifier of
Kansas
City, MO
Impeller 1 ) Standard Disk-Part No. 8-71 I -0004
2) Toothed Disk-Part No. 8-711-0691
CA 02288687 2003-02-17
27
Composition
Comuonent
Cationic Wet Strength Resin 12
Solution
TiO~ Dispersion 32
Dry Strength Additive Solution 55
Water 1
Total 100
Table 6 lists the properties of several pigmented adhesive batches made
according to
various process conditions.
Table 6
Run Disk Bat DeliveryEnerev Median UnsoniratedT
Added
No. T~, Size (rpm)Num (WattlKg)Particle Siu (I~
(K8) (m)
1 Standard11G 1800 1.6210'435.2 0.679 3567
2 Toothed I1G 1800 1.6210'90.3 0.566 3721
3 Toothed 230 1800 1.1510'488.1 0.57? NA
Exa 4
This example discusses the properties of a mufti-ply paper product laminated
using
the pigmented adhesive composition prepared according to the method of Example
2.
Such paper products may be made from two plies of cellulosic fibers as is
commonly
used in Bounty brand paper towels marketed by The Procter & Gamble Company of
Cincinnati, OH and the assignee of the present invention. Each ply is made of
65
percent northern softwood KraR, 35 percent CTMP, and has a basis weight of 14
pounds per 3,000 square feet. Each ply is embossed in a nested embossing
process by
elliptically shaped protuberances having at the distal end a major axis of
0.084 inches,
a minor axis of 0.042 inches and a protuberance height of 0.070 inches. The
CA 02288687 2003-02-17
?s
protuberances are spaced in a concentric diamond pattern on a 45 degree pitch
of
about 0.118 inches. Two complementary plies are made and joined together at a
zero
clearance marrying nip, so that a unitary laminate having about 33
protuberances per
square inch per ply is formed.
The method of Example 3 provides an adhesive composition having 5.75% total
adhesive solids, of which I .5% is Kymene and 4.25% is polyvinyl alcohol. The
adhesive composition also comprises 23% Ti02 solids. This adhesive composition
is
applied to the protuberances of one ply. The total solids of the adhesive
composition
is applied to the paper product. The resulting paper product has a wet ply
bond
strength of 5.~ grams per inch and a dry ply bond strength of 10.4 grams per
inch.
Methods for measuring wet ply bond strength and dry ply bond strength are
described in the TEST METHODS section below.
In Table 7 the wet ply bond strength and the dry ply bond strength of paper
towel
products laminated with adhesive compositions prepared according to the
present
invention are compared to other commercially available paper towels.
Table 7
Wet Ply Bond Dry Ply bond
SamRl_e Manufacturer tr~enQth Stren h
(grams/inch) (grams/inch)
Present InventionAssignee 5.5 10.4
BOUNTY TM Assignee 3.9 10.1
TM
BRAWNY* Tames River 3.1 10.1
TM
SPARKLE* weorgia Pacific3.0 7.0
MARDIS GRAS* ' Ft. Howard 3.4 7.6
TM
VIVA 2-PLY*~TM Scott 3.0 4.4
TM
1~iI-DRI* Kimberly Clark3.4 5.5
* Data from U.S. Patent 5,858,554.
Each of the wet and dry ply bond strengths in Table 6 represents an average of
at
least five samples. Of course, for the dry ply bond strength test, each of the
five
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samples represents an average of four test specimens. As is clearly
demonstrated by
the data shown in Table 7, the adhesive composition of the present invention
provides substantially improved wet ply bond strength while maintaining a dry
piy
bond strength comparable to commercially available paper towels. When paper
towels that are laminated using the adhesive compositions of the present
invention
are immersed in water, the pattern of the pigmented adhesive is clearly
visible.
When the commercially available paper towels listed in Table 7 are similarly
immersed, there is no clearly visible pattern.
Exam
This example is intended to demonstrate the formulation of a pigmented
laminating
adhesive according to the present invention that comprises alternative
materials.
Table 8 lists the composition of a laminating adhesive according to the
present
invention that comprises both an alternative inorganic pigmenting material and
an
optional cationic additive.
Table 8
Com op nent Concentration
(Weight Percent)
Dry Strength Additive' 4.5
Pigment' 18.0
Cationic Wet Strength Resin' 0.3
Optional Cationic Additive4 0.7
Alternative Pigment' 1.0
Water QS 100%
1. ELVANOL~' 71-30
2. Solids provided by Ti-Pure' RPS Vantage Rutile Paper Slurry
3. Kymene~' S57LX
4. Cypro'~ 515
5. Aerosil'~ 300
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The composition is prepared substantially according to the preferred method of
the
present invention using a laboratory blender (Osterizer) to energize the
composition
as the components are blended. Evaluation of the finished composition shows: I
) no
visible separation after 14 days; 2) turbidity comparable to other
compositions of the
present invention-2600 NTU; 3) the whiteness of a thin layer of the adhesive
composition of the present example, when the composition is applied to a
tissue
substrate using metering rods (available from Paul N. Gardner Co., Inc. of
Pompano
Beach, FL as size 8 ) to control coating thickness, is comparable to the
whiteness of
an adhesive composition prepared according to Example 2 applied to a tissue
substrate in the same manner, and 4) viscosity is comparable to other
compositions
of the present invention-170 centipoise.
TEST METHODS
D_rv Piy Bond Streneth
Samples of four finished paper products are provided. Samples are aged for at
least
two weeks after making to allow the adhesive system to fully cure. One three
inch
strip running the entire length of the sample is cut from the center of each
sample.
Two of the strips are cut in the machine direction and the other two are cut
in the
cross machine direction (i.e., between perforations in the machine direction
or
between edges in the cross machine direction). The strips are separated
slightly
along either of the three inch edges, so that each ply is available
independent of the
other. The plies are manually separated until the sample has a gage length of
two
inches.
Each ply is placed in the jaw of a tensile machine. A suitable tensile tester
is a
Model 1451-24 supplied by the Thwing/Albert Corporation of Philadelphia,
Pennsylvania. The crosshead separation speed is set at 20 inches per minute
and
travels 7.5 inches from an initial separation of 2.0 inches. Data is only
recorded for
the last six inches of crosshead travel. All four samples are tested in
tension. The
four numbers are then averaged to give a single ply bond strength
representative of
the product from which all four samples were taken.
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Care must be taken that the portion of the sample yet to be separated by the
tensile
machine does not contact the lower jaw or the lower crosshead of the tensile
machine. If such contact occurs, it will register on the load cell and give a
reading
which is erroneously high. Similarly, care must be taken that the portion of
the
sample yet to be separated does not contact the portion of the sample having
the
plies already separated by the tensile tester. If such contact occurs, it will
falsely
increase the apparent ply bond strength. If either of the aforementioned
contacts
occur, the data point is to be discarded and a new sample tested.
Wet Plv Bond Streneth
Samples of four finished paper products are provided. Samples are aged for at
least
two weeks after making to allow the adhesive system to fully cure. One three
inch
strip running the entire length of the sample (e.g., between perforations for
material
that has been converted into commercial paper toweling)is cut from the center
of
each sample. Two of the strips are cut in the machine direction and the other
two are
cut in the cross machine direction (i.e., between perforations in the machine
direction or between edges in the cross machine direction). The strips are
separated
slightly along either of the three inch edges, so that each ply is available
independent
of the other. The plies are manually separated until the sample has a gage
length of
two inches.
The plies are separated along one of the three inch edges of the sample. 'The
portion
of the sample which has not been separated, i.e., the portion which is not to
be
placed in the jaws of the tensile machine, is immersed in distilled water.
After
immersion, the sample is immediately removed from the water and allowed to
drain
for 60 seconds on a draining rack. The draining rack is provided with a nylon
wire
square mesh. The wires forming the mesh are 0.015 inches diameter on a pitch
of
0.25 inches. The drying rack is oriented at an angle of 45 degrees relative to
the
horizontal. While drying on the drying rack, the sample is oriented so that
the longer
edges of the sample are downwardly aligned with the slope of the drying rack.
The
separated edges of the ply are brought back together in the drying rack so
that the
sample is as smooth as possible, and the sample properly drains excess water.
After
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having been prepared in this manner, the sample is then tested in the tensile
machine
as described above for the dry ply bond strength.
Viscosity
Overview
This method is suitable for measurement of viscosity as a function of shear
rate. The
sample is disposed in a narrow annular volume between two concentric
cylinders.
The inner cylinder rotates at a controlled angular speed, and the resulting
torque or
force generated by the sample between the two cylinders is a measure of the
viscosity of the sample disposed between them.
Annaratus
Viscometer A suitable viscometer is available from Paar Physica USA, Inc. of
Edison, NJ as Model MC 1.
Apparatus Set Un
1 ) Set up the viscometer according to the manufacturer's instructions.
2) Sample and apparatus temperature should be 2311 °C.
Method
1 ) Fill the outer cylinder to the marked level with the sample to be
evaluated.
2) Insert the outer cylinder into the viscometer insuring 'that the inner
cylinder is
centered therein and lock the outer cylinder into place. Allow at least ten
seconds
after locking the outer cylinder into place for the sample to fill the annular
volume
between the two cylinders before beginning a viscosity scan.
3) Set the viscometer to scan between 1 U and 1000 seconds -' and use a ramp
up/ramp down protocol for viscosity measurement. Fifty measurements are made
in
the ramp up portion and fifty measurements in the ramp down portion.
Data Recording_and Analysis
Record the viscosity from each of two samples at shear rates of 100 seconds -'
and
1000 seconds -' shear rate from the ramp down portion of the protocol.
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Charge Density
Overview
Charge density of a dispersion or a colloidal solution can be measured by
measuring
the electrical potential (streaming potential) between a pair of spatially
separated
electrodes one of which is adjacent to a surface of a sample container where
the
particles of the dispersion or the macromolecules from a colloidal solution
have been
caused to adsorb and the other of which is positioned in the free volume of
the
sample container. The counterions for any charged particulate or
macromolecular
species are caused to flow by an oscillating piston setting up the electrical
potential.
The sample is then titrated to a zero streaming potential (i.e. to the
isoelectric point)
with a standard polyelectrolyte having the opposite charge to measure charge
density
in microequivalents per gram.
Apparatus
Particle Charge Detector: A suitable apparatus for measuring charge density is
available from ML1TEK Analytic, Inc. of Marietta, GA as Particle Charge
Detector
PCD 02.
Titrator: A suitable titrator is the Mettler automatic endpoint titrator model
DL21 with two piston burettes which is also available from MUTEK Analytic,
Inc.
of Marietta, GA
Standard Materials
Standard polyelectrolyte solutions are also available from MUTEK Analytic. The
cationic standard is 0.001 N poly-diallyi-dimethyl-ammonium chloride. The
anionic
standard is O.OO1N sodium polyethylene sulfate.
Qpgration
1 ) Set up and calibrate the particle charge detector according to the
manufacturer's
directions. Importantly, the ambient temperature should be greater than
15°C,
preferably about 25°C, for accurate measurement.
2) Set up and calibrate the titrator according to the manufacturer's
instructions.
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3) Rinse the sample cell and the piston of the particle charge detector with
sample.
The sample may be filtered (100 mesh strainer) to remove large particles which
may
interfere with operation of the piston although being only a small portion of
the
charged species.
4) Dispense a controlled amount of sample into the rinsed sample cell. A
preliminary titration may be necessary to determine the amount of sample that
will
require between 0.5 and 15 milliliters of titrant. At least 10 milliliters of
liquid is
required to cover both electrodes. Samples may be diluted with deionized water
to
provide a sample of at least 10 milliliters volume that requires between 0.5
and 15
milliliters of titrant.
5) Insert the piston into the sample container and place the container into
the
particle charge detector, insuring that the electrodes are in contact and the
piston is
engaged with the drive mechanism.
6) Turn the piston on and allow the streaming potential to stabilize (about 2
minutes).
7) Titrate the sample to the isoelectric point using the appropriate
polyelectrolyte
solution. That is, titrate cationic samples with the anionic polyelectrolyte
and titrate
anionic samples with the cationic polyelectrolyte.
Data Recording and Anal.Ysis
I ) Record the amount of titrant required to take the sample to the
isoelectric point.
2) Calculate charge density q (microequivalents per gram) using the following
equation:
L'xCx1000
W
Where: V is the volume of titrant required (milliliters); C is the
polyelectrolyte
concentration (microequivalents per milliliter); and W is the solids content
in the
sample (e.g. for a 10 milliliter sample of a 0.1 % Ti02 suspension, W=0.01
grams)
3) Report the result of each measurement made.
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Particle Size Distribution
Overview
The particle size distribution of the pigment particles formed in the process
of the
present invention may be measured using a light scattering apparatus. Both
coherent
and non-coherent light sources are used, depending on the expected range of
particle
sizes.
A_pnaratus
A suitable apparatus is available from Horiba Instruments, Inc. of Irvine, CA
as
Model LA910. The Horiba LA910 measures the Particle Size Distribution (PSD)
using a scattering system. Both a coherent light source (laser) and a non
coherent
light source are provided for measurement of a wide range of PSDs. This
apparatus
can determine four distributions (Volume, Number, Area and Length) for a given
sample. Software is provided for an attached computer to control the apparatus
and
to convert the light intensity data that is actually measured into any of the
above-
identified distributions. The Volume Distribution is preferred to follow
structural
changes. Median particle size is preferred as a single number descriptor of
PSD so as
to provide a proper description for cases which depart from a normal
distribution.
The Horiba LA910 has capability for low-power sonication (about 40 watts) to
separate aggregates. Measuring the PSD without sonication is preferred to
better
understand any agglomeration that may result from a particular mixing process.
Standard Materials
Calibration Standard NanosphereTM Standard Polystyrene particles as supplied
by
Duke Scientific of
Palo Alto, CA. These
standards are NIST
traceable.
Apparatus Setun
Relative Refractive 2.00-O.OOi
Index (RRI):
Agitation: 3
Circulation: 4
Sonication: Off
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Method
1 ) Set up and calibrate the instrument according to the manufacturer's
instructions.
2) Measure the particle size distribution for a blank (deaerated, deionized
water)
to check the instrument base line by filling the sample cell with the water
and
clicking on measure on the computer screen.
3) Place 150 milliliters of deaerated, deionized water into the sample cell
and
insert the cell into the apparatus.
4) Add the sample dropwise until the light transmission scale (blue scale) as
measured by the apparatus is between about 70% and 75%.
5) Click measure on the computer screen to gather data from the sample and to
determine the particle size distribution of the sample.
Data Recording and A Y,
1 ) Measure particle size distribution for at least two samples.
2) Determine if the distribution is monodisperse of polydisperse.
3) For monodisperse distributions report the median particle size.
4) For polydisperse distributions report the particle size defined by each
peak of
the distribution.
T r idit
Overview
Turbidity is a measure of the opacity/cloudiness of liquid suspensions.
Turbidity is
measured by determining the amount of light scattering due to the suspended
particles.
Instrument
Turbidimeter A suitable turbidimeter is available from HACH Company of
Loveland, CO as Model 2100AN.
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Standard Materials
Standard turbidity materials (StablCal Standards) having turbidity
values of <0.1, 20, 200, 1000, 4000, and 7500 Nephelometric Turbidity Units
(NTU)
are also available from HACH Company.
Method
1 ) Set up and calibrate the turbidimeter according to the manufacturer's
instructions.
2) Dilute 0.4 grams of the pigmented adhesive with 1000 milliliters of water
and mix for one minute. A magnetic stirrer such as the Corning Model PC-351 as
is
available from Coning Glass Works (Corning, NY) is suitable.
3) Allow the diluted sample to equilibrate for 1 minute.
4) Transfer a suitable volume (~30 milliliters) to the sample cell.
S) Measure turbidity according to the manufacturer's instructions.
6) Record the measured turbidity.
Data Recording and Anal,
1 ) Report the turbidity value in Nephelometer Turbidity Units, NTU.
Mixing Ener~v
Overview
Current and voltage are measured and are used to calculate power delivered to
the
energizing means.
Instrument
Power Analyzer A suitable power analyzer is available from Fluke Corp. Of
Everett, WA as a Model 41 B Power Harmonics Analyzer.
Amp Probe A Model 80I-1000s, also available from Fluke Corp. is suitable.
I ) Insure power meter is calibrated according to manufacturer's instructions.
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2) Place the amp probe around one of the three conductors of the electrical
supply line for the energizing means. Attach voltage probes to the other two
conductors of the supply line. The Fluke 41 B calculates a three-phase power
readout
from a simple, single-phase measurement of a balanced three-conductor load.
Power
measurements were sent and recorded to a Microsoft Excel Spread Sheet using
software supplied with the instrument (Fluke View version 3.0).
3) Measure power consumption with the tank empty by placing a small amount
of water around the seal at the bottom. Measure the power consumption for the
entire range of speed for the specific energizing means being evaluated.
4) Record the power reading from the power analyzer every 10 seconds at least
times through each addition step of the adhesive manufacture process described
above. If desired, data acquisition hardware and software can be used to
sample and
record power readings automatically.
Data Recording, and Analysis
1 ) Calculate Net Power for each addition step by subtracting the power
consumption at the run speed from the power consumption while adding a
material.
2) Calculate Net Power per Unit Mass for each step by dividing the Net Power
by the mass of material being energized after the addition step.
3) Report Net Power and Net Power per Unit Mass for each addition step.
