U.S. patent application number 14/575583 was filed with the patent office on 2015-06-25 for bulk and stiffness enhancement in papermaking.
The applicant listed for this patent is Nanopaper, LLC. Invention is credited to Gangadhar Jogikalmath, Andrea Schneider, David S. Soane.
Application Number | 20150176214 14/575583 |
Document ID | / |
Family ID | 48290757 |
Filed Date | 2015-06-25 |
United States Patent
Application |
20150176214 |
Kind Code |
A1 |
Jogikalmath; Gangadhar ; et
al. |
June 25, 2015 |
BULK AND STIFFNESS ENHANCEMENT IN PAPERMAKING
Abstract
The present invention provides formulations for papermaking and
methods for their use. In embodiments, the formulations include a
treatment agent and a fluid carrier, where the treatment agent
includes a volatile debonder or a polymer composition exhibiting a
lower critical solution temperature. Methods for treating a paper
product to increase its bulk or its stiffness are also disclosed,
in addition to paper products formed from such methods.
Inventors: |
Jogikalmath; Gangadhar;
(Cambridge, MA) ; Soane; David S.; (Chestnut Hill,
MA) ; Schneider; Andrea; (Hyde Park, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Nanopaper, LLC |
Cambridge |
MA |
US |
|
|
Family ID: |
48290757 |
Appl. No.: |
14/575583 |
Filed: |
December 18, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13672015 |
Nov 8, 2012 |
8926796 |
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14575583 |
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61557519 |
Nov 9, 2011 |
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61584489 |
Jan 9, 2012 |
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Current U.S.
Class: |
162/164.6 |
Current CPC
Class: |
D21H 17/56 20130101;
D21H 21/18 20130101; D21H 21/16 20130101; D21H 21/22 20130101; D21H
17/54 20130101; D21H 17/36 20130101; D21H 17/72 20130101; D21H
17/06 20130101 |
International
Class: |
D21H 21/22 20060101
D21H021/22; D21H 17/54 20060101 D21H017/54; D21H 17/06 20060101
D21H017/06; D21H 21/16 20060101 D21H021/16 |
Claims
1. A formulation for use in a sizing step for a paper product,
comprising: a treatment agent, wherein the treatment agent
comprises a volatile debonder or a polymer composition exhibiting a
lower critical solution temperature; and a fluid carrier with which
the treatment agent forms an emulsion or a solution.
2. The formulation of claim 1, wherein the volatile debonder is
evaporable from the paper product during the sizing step.
3. The formulation of claim 1, wherein the polymer composition has
a higher affinity for cellulose fibers in the paper product when a
temperature of the paper product is above a transition temperature
than when the temperature is below the transition temperature.
4. The formulation of claim 1, wherein the treatment agent is
formulated in an aqueous solution or emulsion for dispersal by
spraying on the paper product.
5. The formulation of claim 1, wherein the treatment agent is
dispersible within a sizing solution used during the sizing
step.
6. The formulation of claim 1, wherein the treatment agent
comprises a polyetheramine.
7. The formulation of claim 1, wherein the treatment agent is a
bulking agent.
8. The formulation of claim 1, wherein the treatment agent is a
stiffening agent.
9. A method for treating a paper product to increase its bulk,
comprising: preparing a bulking formulation as an aqueous solution
or emulsion, wherein the bulking formulation comprises a volatile
debonder or a polymer composition exhibiting a lower critical
solution temperature; applying the bulking formulation to the paper
product during a sizing step of papermaking; and drying the paper
product, thereby treating the paper product to increase its
bulk.
10. The method of claim 7, wherein the bulking formulation is
applied to the paper product by spraying.
11. The method of claim 7, wherein the bulking formulation is
blended with a sizing solution, and wherein the sizing solution is
applied to the paper product during the sizing step.
12. The method of claim 7, further comprising evaporating the
volatile debonder from the paper product.
13. The method of claim 7, further comprising raising the
temperature of the paper product above a transition temperature,
wherein the polymer composition has a higher affinity for cellulose
fibers above the transition temperature than it does below the
transition temperature, and wherein raising the temperature of the
paper product above the transition temperature increases the bulk
of the paper product.
14. A method for treating a paper product to increase its
stiffness, comprising: preparing a stiffening formulation as an
aqueous solution or emulsion, wherein the bulking formulation
comprises a volatile debonder or a polymer composition exhibiting a
lower critical solution temperature; applying the stiffening
formulation to the paper product during a sizing step of
papermaking; applying a starch-containing formulation to the paper
product; and drying the paper product, thereby treating the paper
product to increase its stiffness.
15. The method of claim 14, wherein the stiffening formulation is
applied to the paper product by spraying.
16. The method of claim 14, wherein the stiffening formulation is
blended with a sizing solution, and wherein the sizing solution is
applied to the paper product during the sizing step.
17. The method of claim 14, further comprising evaporating the
volatile debonder from the paper product.
18. The method of claim 14, further comprising raising the
temperature of the paper product above a transition temperature,
wherein the polymer composition has a higher affinity for cellulose
fibers above the transition temperature than it does below the
transition temperature, and wherein raising the temperature of the
paper product above the transition temperature increases the bulk
of the paper product.
19. A method for incorporating an advantageous compound into a
paper product, comprising: preparing a bulking or stiffening
formulation as an aqueous solution or emulsion, wherein the bulking
formulation comprises a volatile debonder or a polymer composition
exhibiting a lower critical solution temperature; preparing an
additive formulation comprising the advantageous compound as an
aqueous solution or emulsion; applying the bulking or stiffening
formulation to the paper product during a sizing step of
papermaking; applying the additive formulation to the paper
product; and drying the paper product, wherein the advantageous
compound is incorporated into the paper product following the step
of drying the paper product.
20. The method of claim 19, wherein the advantageous compound
comprises starch.
21. The method of claim 19, wherein the advantageous compound is
selected from the group consisting of an oil/grease resistance
agent, an optical brightener, an ink binder, a dust preventer, a
water repellent, a stiffener, a biocide, a biomolecule for
controlled release, a superabsorbent polymer, a gloss strength
builder, a colorant, an adhesion-release agent, a diagnostic sensor
agent, a filtration assist agent, a targeted capture/sequestrants
agent and a biomedical component.
22. A paper product formed by the method of claim 14.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 13/672,015, filed on Nov. 8, 2012, which claims the benefit of
U.S. Provisional Application Ser. No. 61/557,519, filed Nov. 9,
2011 and U.S. Provisional Application Ser. No. 61/584,489, filed
Jan. 9, 2012. The entire contents of the above applications are
incorporated by reference herein.
FIELD OF THE APPLICATION
[0002] This application relates generally to debonders for
enhancing bulk and stiffness in paper products.
BACKGROUND
[0003] The customer judges the quality of paper products by
evaluating a combination of properties, including smoothness,
gloss, brightness and feel. In particular, tactile feedback
indicating a higher caliper (thickness) for the paper conveys the
impression that the product is of high quality. Making paper
thicker, though, typically involves using more pulp, so that the
paper is heavier and more expensive. To produce a thicker paper
without incorporating additional pulp, the papermaking industry has
identified a number of inexpensive particulate additives that act
as low-density fillers to create the feel of a thicker paper while
decreasing weight and cost. Examples include EXPANCEL.RTM. (Akzo
Nobel) and OMNIBULK.RTM. (Kemira).
[0004] Such fillers, however, can impair the strength and
resiliency of the final product, and do not hold up well under the
forces applied during calendaring. Therefore, a need exists in the
industry for formulations and methods to enhance the bulk of paper
products while yielding sheets that remain strong and flexible.
Desirably, such formulations and methods are compatible with
existing papermaking techniques and equipment.
[0005] In addition to bulk, paper industry also desires an
improvement in stiffness of paper products. There is particularly
need for such improvement in packaging industry where rigidity is
necessary for structural reasons and fine papers where rigidity is
necessary to ensure that the paper can undergo repeated bending in
copying and printing processes yet retain its dimensional
stability.
SUMMARY
[0006] Disclosed herein, in embodiments, are formulations for use
in a sizing step for a paper product, comprising: a treatment
agent, wherein the treatment agent comprises a volatile debonder or
a polymer composition exhibiting a lower critical solution
temperature; and a fluid carrier with which the treatment agent
forms an emulsion or a solution. In embodiments, the volatile
debonder is evaporable from the paper product during the sizing
step. In embodiments, the polymer composition has a higher affinity
for cellulose fibers in the paper product when a temperature of the
paper product is above a transition temperature than when the
temperature is below the transition temperature. In embodiments,
the treatment agent is formulated in an aqueous solution or
emulsion for dispersal by spraying on the paper product. In
embodiments, the treatment agent is dispersible within a sizing
solution used during the sizing step. In embodiments, the bulking
agent comprises a polyetheramine. Examples of such polyetheramines
that can be used include, for example, the JEFFAMINE.RTM. class of
polymers. In embodiments, the treatment agent is a bulking agent.
In other embodiments, the treatment agent is a stiffening
agent.
[0007] Also disclosed herein, in embodiments, are methods for
treating a paper product to increase its bulk, comprising preparing
a bulking formulation as an aqueous solution or emulsion, wherein
the bulking formulation comprises a volatile debonder or a polymer
composition exhibiting a lower critical solution temperature;
applying the bulking formulation to the paper product during a
sizing step of papermaking; and drying the paper product, thereby
treating the paper product to increase its bulk. In embodiments,
the bulking formulation is applied to the paper product by
spraying. In embodiments, the bulking formulation is blended with a
sizing solution, and the sizing solution is applied to the paper
product during the sizing step. In embodiments, the methods further
comprise evaporating the volatile debonder from the paper product.
In embodiments, the methods further comprise raising the
temperature of the paper product above a transition temperature,
wherein the polymer composition has a higher affinity for cellulose
fibers above the transition temperature than it does below the
transition temperature, and wherein raising the temperature of the
paper product above the transition temperature increases the bulk
of the paper product.
[0008] Further disclosed herein, in embodiments, are methods for
treating a paper product to increase its stiffness, comprising
preparing a stiffening formulation as an aqueous solution or
emulsion, wherein the stiffening formulation comprises a volatile
debonder or a polymer composition exhibiting a lower critical
solution temperature; applying the stiffening formulation to the
paper product during a sizing step of papermaking; applying a
starch-containing formulation to the paper product; and drying the
paper product. In embodiments, the stiffening formulation is
applied to the paper product by spraying. In embodiments, the
stiffening formulation is blended with a sizing solution, and the
sizing solution is applied to the paper product during the sizing
step. In embodiments, the methods further comprise evaporating the
volatile debonder from the paper product. In embodiments, the
methods further comprise raising the temperature of the paper
product above a transition temperature, wherein the polymer
composition has a higher affinity for cellulose fibers above the
transition temperature than it does below the transition
temperature, and wherein raising the temperature of the paper
product above the transition temperature increases the stiffness of
the paper product.
[0009] In other embodiments, methods are disclosed herein for
incorporating an advantageous compound into a paper product,
comprising: preparing a bulking or stiffening formulation as an
aqueous solution or emulsion, wherein the bulking or stiffening
formulation comprises a volatile debonder or a polymer composition
exhibiting a lower critical solution temperature; preparing an
additive formulation comprising the advantageous compound as an
aqueous solution or emulsion; applying the bulking or stiffening
formulation to the paper product during a sizing step of
papermaking; applying the additive formulation to the paper
product; and drying the paper product, wherein the advantageous
compound is incorporated into the paper product following the step
of drying the paper product. In embodiments, the advantageous
compound comprises starch. In embodiments, the advantageous
compound is selected from the group consisting of an oil/grease
resistance agent, an optical brightener, an ink binder, a dust
preventer, a water repellent, a stiffener, a biocide, a biomolecule
for controlled release, a superabsorbent polymer, a gloss strength
builder, a colorant, an adhesion-release agent, a diagnostic sensor
agent, a filtration assist agent, a targeted capture/sequestrants
agent and a biomedical component.
[0010] In addition, paper products are disclosed herein that are
formed by the aforesaid methods.
BRIEF DESCRIPTION OF THE FIGURES
[0011] FIG. 1 shows a schematic diagram of a papermaking
process.
[0012] FIG. 2 shows HLB values of debonding agents.
[0013] FIGS. 3A and 3B show microscopy images of paper
cross-sections.
[0014] FIG. 4 shows a graph of caliper increase for different
debonder concentrations.
[0015] FIG. 5 shows bulking improvement as a function of debonder
concentration in starch sizing solution.
[0016] FIG. 6 shows normalized tensile strength of treated paper
vs. control.
[0017] FIG. 7 shows normalized caliper of treated paper vs.
control.
[0018] FIG. 8 shows a graph of stiffness of treated paper vs.
control.
[0019] FIG. 9 shows a graph of viscosity for cooked starch with
various amounts of TPnB additive.
[0020] FIG. 10 shows a graph of stiffness of treated paper vs.
control.
DETAILED DESCRIPTION
A. Debonders as Bulking Agents
[0021] Disclosed herein are formulations and methods for adding
bulk to sheet paper by using debonders. It has been unexpectedly
discovered that various debonding agents can be used advantageously
as treatment agents to enhance the bulk of sheet paper products,
both uncoated free sheets and coated free sheets (e.g., light
weight coated, super calendared). Not to be bound by theory, it is
understood that a debonding agent can reduce hydrogen bonds between
cellulose fibers, acting as a spacer molecule to separate the
cellulose fibers during their processing. Thus, the debonding agent
can prevent capillary action from consolidating the cellulose
fibers during the drying process, so that these fibers do not
consolidate as densely, resulting in a sheet having increased
caliper.
[0022] As shown in FIG. 1, a papermaking assembly 102 can comprise
a number of elements that process the pulp to form the final sheet
product. As shown in the Figure, a headbox 104 is provided to
introduce the pulp slurry (not shown) into the papermaking assembly
102. At Point A, debonders as described herein can be introduced
into the papermaking process before it passes into the headbox. A
vacuum section 108 removes some of the liquid from the pulp slurry.
At Point B, debonders as described herein can be introduced into
the papermaking process, before the vacuum section 108 to improve
penetration of the debonders. A press section 110 removes more
liquid from the pulp slurry as it is formed into a paper web. At
point D, after the press section 110, debonders as described herein
can be introduced into the papermaking process. A drying section
112 removes more of the moisture from the paper web. The paper web
can then pass into a size press 116 for imparting starch or other
binder based sizing to the paper (either on one side or both sides
of the paper). Debonders as described herein can be introduced into
the size press solution, or can be metered onto the size press 116
to be incorporated into the paper. The paper then passes into a
dryer 118 for final drying.
[0023] 1. Volatile Debonders as Bulking Agents
[0024] In embodiments, volatile debonders can be introduced into
the papermaking process at discrete points, such as Points A, B, D
or C as depicted in FIG. 1. A volatile debonder is an agent that is
capable of interacting with cellulose pulp to decrease the
intermolecular forces in the paper web, but is also capable of
evaporating under processing temperatures so that there is minimal
residual debonder when the paper web is pressed into final
form.
[0025] As would be understood by skilled artisans, during the early
stages of drying the cellulose fibers are not bonded to each other.
Adding a volatile debonder, as disclosed herein, to the paper web
prior to drying (e.g., at Point A, Point B or Point D in FIG. 1)
can serve to keep the cellulose fibers apart. As drying progresses,
the cellulose fibers in the paper web are normally drawn together.
The presence of a volatile debonder interferes with this bond
formation and holds the fibers apart. As drying progresses, though,
the volatile debonder evaporates, but the cellulose fibers remain
spaced apart from each other. This condition, where the paper
fibers are spaced apart from each other as the paper dries, results
in a product with greater bulk.
[0026] In other embodiments, volatile debonders can be added to the
paper sheet after the drying process, for example at Point C in
FIG. 1. Such debonders can be added, during the size press process,
for example, by being incorporated into the size press solution, or
by being applied separately to the paper web before it enters the
size press, or during the size press process. Volatile debonders
added during the size press process can act upon the paper sheet to
space apart the fibers, thereby increasing the bulk of the paper
sheet. When the sheet is dried again following size pressing, the
volatile debonders are driven off so that the paper sheet is
virtually free of residual debonder.
[0027] In embodiments, volatile debonders useful as bulking agents
can be derived from a class of organic molecules that can be
volatilized using the high temperatures available in the paper
making process. These organic molecules capable of acting as
volatile debonders can be added to the wet-end or the size press.
The volatile debonders do not affect the wet-strength of the
wet-web, resulting in lower breaks and allowing the paper machine
to run at higher speeds than is possible with traditional debonder
systems. The debonding occurs as the minority component of volatile
debonder in the white water concentrates while the web moves along
the drying section, so that consolidation of the cellulose fiber
mat is prevented. The volatile debonder then can be removed in the
final stages of drying such that the dry sheet is debonded, has a
higher caliper and does not contain residua of the debonding
agent.
[0028] As an example, a volatile debonder can be added, in
embodiments, to the wet end of the papermaking process: for
example, on the wet web after the head box, to the wet web before
the press section, or after the press section but before the
dryers. In embodiments, the volatile debonder can be added as shown
in FIG. 1, at Point A, Point B or Point C. In embodiments, the
volatile debonder can also be added, for example by spraying or
topically applying the volatile debonder formulation at relevant
points during the papermaking process, for example at Points A, B
or C.
[0029] In embodiments, the volatile debonder can be added to the
size press application system. The volatile debonder can then
separate the cellulose fibers and increase the caliper, while
volatilizing in the secondary dryer section. In embodiments, the
volatile debonder can be mixed into a water-based sizing solution,
which can comprise agents such as water, cooked starch, hydrophobic
chemicals, colors, brightening agents, and the like.
[0030] A formulation comprising a bulking agent can be termed a
bulking formulation. In embodiments, formulations are prepared
where the bulking agent is a water-soluble debonder, but where the
water and the active debonder ingredient can form an azeotropic
mixture that allows both water and debonder to be evaporated
together at a working temperature for the papermaking process. An
azeotrope is a mixture of two or more liquids, the composition of
which does not change upon distillation. Such liquid mixtures
behave like a single substance in that the vapor produced by
partial evaporation of liquid has the same composition as the
liquid. Thus, the mixtures distill at a constant temperature
without change in composition and cannot be separated by normal
distillation.
[0031] In embodiments, active debonder ingredients can be selected
that have specific hydrophilic or hydrophobic properties, but that
are still water-soluble and capable of forming azeotropic mixtures
with water that can be evaporated at a working temperature for the
papermaking process. In embodiments, a positive azeotropic mixture
can be formed, for example one having a constant boiling point
lower than the boiling point of water. In other embodiments, a
negative azeotropic mixture can be formed. Advantageously, the
azeotrope formed by the water and the volatile debonder is designed
so that both agents boil off at the processing temperature of the
pulp during the drying stage of papermaking, approximately
110-180.degree. C., with the presence of the volatile debonder
acting to keep the paper fibers sufficiently separated that they
are less likely to form intermolecular bonds. Although certain of
these compounds boil at temperatures higher than that of paper
processing/drying, the fact that they form azeotropes helps in
their removal during the drying temperatures encountered in the
papermaking process. Once the sheet is dried at temperatures of
>90.degree. C., the molecules evaporate, leaving behind a very
small amount, or no residue and a sheet with enhanced bulk.
[0032] Not to be bound by theory, it is understood that during the
early stages of the drying process in papermaking, the pulp enters
the drying section of the mill containing about 60% water. The free
water in the pulp acts as a capillary attractant, pulling the
cellulose fibers towards each other. As the free water is driven
off during drying, the fibers are drawn even closer together as
intermolecular bonding takes place. This normal process of
papermaking yields a strong paper sheet.
[0033] When the volatile debonders disclosed herein are used as
bulking agents, the intermolecular processes in the paper product
are different, as is the final result. In embodiments, the
water-soluble volatile debonders as disclosed herein can act as
spacers to separate the cellulose fibers, so that they do not draw
close enough to form hydrogen bonds during drying. The spacing
between the pulp fibers produced by the debonder decreases the
fibers' capacity for intermolecular bonding, just as occurs with
traditional organic debonders. The co-presence of the debonder
molecules and the water molecules impairs the ability of the
cellulose fibers to form bonds; because the debonder and water form
an azeotropic mixture, their co-presence is assured throughout the
evaporation process, so that the distance between the cellulose
fibers is maintained. Furthermore, because the volatile debonders
disclosed herein evaporate along with the water during drying, the
final product does not contain undesirable organic residua.
[0034] 2. Lower Critical Solution Temperature Debonders as Bulking
Agents
[0035] In embodiments, certain polymers having lower critical
solution temperature (LCST) properties can be used as bulking
agents. Without being bound by theory, it is understood that these
polymers exhibit a temperature-dependent solubility phenomenon
called Lower Critical Solution Temperature (LCST). Such agents,
e.g., certain polymers such as those containing ethylene oxide and
propylene oxide monomers, are soluble in water or aqueous solutions
at temperatures below the LCST, while heating the solutions leads
to polymer precipitation from the solution above the LCST. In
embodiments, the LCST property of these polymers can be used as
additives during the papermaking process to enhance bulk, relying
on the differences in temperature during papermaking to cause and
maintain their deposition on the paper fibers. In embodiments, the
solubility of these polymers is temperature-dependent, so that the
polymer is soluble at lower temperatures, but is insoluble at
higher temperatures: thus, when the temperature rises in a mixture
containing the LCST polymer in solution with cellulose fibers, the
LCST polymer tends to deposit on the fiber surfaces. The presence
of the polymer on the fiber surfaces can inhibit fiber-fiber
attractions due to hydrogen bonding, so that the fibers assume a
spaced-apart configuration. With the increased spacing between the
fibers, the fiber density per unit volume decreases, and the bulk
of the final product increases.
[0036] In embodiments, LCST polymers can be used for bulk
enhancement of paper products where the polymer has a higher
affinity for cellulose fibers above its transition temperature. In
some embodiments, a bulking agent can include a LCST polymer
(either a portion of or the entirety of the molecule) or other
material exhibiting a lower critical solution temperature (e.g., a
copolymer containing ethylene oxide and propylene oxide units) that
can allow it to deposit on the cellulose fibers as the temperature
is increased, for example during the drying or size press steps of
papermaking. With reference to FIG. 1, a LCST polymer can be
applied during the wet end of papermaking, at Point A or Point B,
or during the size press process, for example at Point C. When
applying a LCST polymer as a bulking agent during the size press
process, it can, in embodiments, be incorporated into the size
press solution, or applied separately to the paper web before it
enters the size press or during the size press process.
[0037] In embodiments, a treatment agent can be selected for use as
a bulking agent at a specified phase of the papermaking process.
For the fabrication of fine sheet paper, for example, the
papermaking machine operates at a high speed. Accordingly, it may
be less desirable to use a bulking/debonding agent during the wet
phase of papermaking, where it can impair the strength of the sheet
as it moves across the papermaking machinery. For these
applications, the bulking/debonding agent can be added during the
size press process. Volatile debonding/bulking agents and LCST
agents can be used during the size press process. In embodiments,
the use of these agents can be combined with other additives and
formulations that comprise the size press solution, such as starch,
fiber, ash, particulates and the like. In embodiments, the
debonding/bulking agents as disclosed herein are suitable for use
in the production of uncoated free sheet paper as well as coated
free sheet paper.
B. Exemplary Bulking Agents
[0038] In embodiments, a class of molecules having a range of HLB
values (HLB: hydrophilic lipophilic balance, where a value of 0
means a completely hydrophobic molecule and a value closer to 20
indicates a hydrophilic molecule) that are miscible with water can
be used as bulking agents in accordance with this disclosure. In
embodiments, these molecules can be used as volatile debonders,
because they have varying boiling points that can be selected in
accordance with their attraction to the underlying surface so that
they change the surface energy (and hence the wetting or
non-wetting characteristics of the surface) in a temporary manner.
In embodiments, these molecules can be used as bulking agents.
[0039] In embodiments, volatile molecules useful as bulking agents
are water-miscible. In embodiments, certain of these molecules can
form azeotropic mixtures with boiling points that are compatible
with the operating temperatures of the papermaking process. In
embodiments, the azeotropic mixture formed between the volatile
bulking agent and water will evaporate during drying. In
embodiments the volatile bulking agent compounds can be sprayed
onto a wet paper web during the papermaking process.
[0040] One such class of molecules includes glycol ethers having
aliphatic and/or aromatic side chains. As examples, a number of
glycol ethers having advantageous properties as volatile debonders
are included in the DOWANOL.RTM. line of solvents (DOW Corp.,
Midlands Mich.). In other embodiments, glycol ethers having
advantageous properties include those manufactured as Acrosolv
products from Lyondell-Basell (Houston, Tex. USA) or Eastman
solvents from Eastman Chemicals (Kingsport, Tenn. USA).
[0041] Other useful molecules include other Ethylene glycol ethers,
such as Ethylene glycol monomethyl ether, Ethylene glycol monoethyl
ether, Ethylene glycol monopropyl ether, Ethylene glycol
monoisopropyl ether, Ethylene glycol monobutyl ether, Ethylene
glycol monobenzyl ether, and the like, and other glycol ether
acetates such as Ethylene glycol methyl ether acetate, Ethylene
glycol monethyl ether acetate, Ethylene glycol monobutyl ether
acetate, and the like. Molecules with higher molecular weights have
higher boiling points, a factor that can influence selection as a
volatile debonder for papermaking. In embodiments, tripropylene
glycol n-butyl ether and tripropylene glycol methyl ether (both
with higher molecular weights than certain other glycol ethers)
have advantageous properties as volatile debonders. In other
embodiments, propylene glycol n-Butyl ether and dipropylene glycol
n-butyl ether (both hydrophobic on the HLB scale) have advantageous
properties as volatile debonders. Other molecules suitable include
branched alkyl alcohols such as Masurf NRW-N (Mason Chemical
Company, IL).
[0042] The extent of debonding, and hence the bulking, can be
controlled by the amount of debonder added to the wet paper web and
the choice of debonder with a hydrophobic HLB value. In
embodiments, volatile debonder compounds have boiling points
varying from 100.degree. C. to 290.degree. C. These molecules can
be added to the wet-end white water system at concentrations
ranging from 0.001 to 1% by weight of the white water in the
system. Volatile debonders can be advantageously added in the range
0.001% to 0.1% by weight. In embodiments, volatile debonder
compounds can be sprayed in water solution onto a wet moving web,
or added thereto as an emulsion, as described below in more
detail.
[0043] Molecules with lower HLB values can also be used that have a
lower boiling point than the drying temperatures of the paper
process when faster evaporation may be desirable. As an example,
propylene glycol methyl ether is useful for this purpose. It is
understood that the more hydrophobic glycol ethers typically have a
lower solubility in water, so that when such molecules are used as
volatile debonders with a high loading by fiber weight, it may be
useful to emulsify them to facilitate their dispersion in an
aqueous mixture. For example, a suitable cationic surfactant or
other emulsifying agent can be used to enable binding of the
hydrophobic glycol ether to the anionic cellulose fibers in the
wet-end of the papermaking process.
[0044] As an example, tripropylene glycol n-butyl ether
(DOWANOL.RTM. TPnB) has a solubility limit of .about.2.5 wt %. If a
loading higher than 3% is required, emulsification can be carried
out to create a stable suspension of the TPnB in water at this
concentration. Suitable emulsifiers for these purposes can include
surfactants such as polyetheramines. As an example, a Jeffamine
polyetheramine such as Jeffamine XTJ 502 compound could be used for
emulsification of Dowanol TPnB if a loading higher than 3% by
weight is desired.
[0045] In embodiments, emulsified mixtures having low HLB values
can be added to the wet end of the papermaking line. For example,
if a polyetheramine such as a Jeffamine is used as the emulsifying
agent, the primary amine in the Jeffamine molecule can act as an
anchor that binds the debonder to the cellulose fiber surface. In
other embodiments, a primary amine such as is present in the
Jeffamine emulsifier could act as an anchor group thereby binding
the debonder to the fiber surface. In other embodiments, the
volatile bulking agent molecules can also be sprayed onto moving
webs. Because of their volatility, they are able to exert their
effects during the drying stages of papermaking, but they then
evaporate off and leave no residuum to impair the hydrophilic
nature of a final paper product. Similarly, emulsions and
azeotropic mixtures and solutions containing volatile debonders can
also be added to the sizing solution at the size press.
[0046] In other embodiments, polymers having LCST properties can be
used as bulking agents, as described above. As utilized within the
present application, the term "polymer" refers to a molecule
comprising repeat units, wherein the number of repeat units in the
molecule is greater than about 10 or about 20. Repeat units can be
adjacently connected, as in a homopolymer. The units, however, can
be assembled in other manners as well. For example, a plurality of
different repeat units can be assembled as a copolymer. If A
represents one repeat unit and B represents another repeat unit,
copolymers can be represented as blocks of joined units (e.g.,
A-A-A-A-A-A . . . B-B-B-B-B-B . . . ) or interstitially spaced
units (e.g., A-B-A-B-A-B . . . or A-A-B-A-A-B-A-A-B . . . . ), or
randomly arranged units. In general, polymers include homopolymers,
copolymers (e.g., block, inter-repeating, or random), cross-linked
polymers, linear, branched, and/or gel networks, as well as polymer
solutions and melts. Polymers can also be characterized as having a
range of molecular weights from monodisperse to highly
polydisperse. A "type of polymer" refers to a polymer formed from a
particular set of repeat units, e.g., A units and B units. A
designated polymer type can or cannot have all the polymer
molecules be of the same molecular weight and/or have the repeat
units oriented identically.
[0047] Polymer compositions useful as bulking agents can be
configured in a number of different dispositions, e.g., having a
polymer where at least one section of the polymer exhibits LCST
behavior. These include polymers where the segments are known to
exhibit LCST behavior to those skilled in the art. As examples,
suitable debonders can include polymers having segments such as
polyalkylene oxides (e.g., polyethylene oxide (PEO) or
polypropylene oxide (PPO) or a mix of such oxides),
ethyl(hydroxyethyl)cellulose, poly(N-vinylcaprolactam),
poly(methylvinyl ether), poly(N-isopropylacrylamide), and
derivatives of such including those understood by ones skilled in
the art. In some embodiments, the polymer composition can comprise
only uncharged species. In embodiments, for example, the polymer
composition can be at least substantially free of polyelectrolytes
(e.g., being substantially or totally free of charges associated
with the polymer structure). Thus, in some embodiments utilizing
uncharged polymers, the transition temperature of a
fiber-containing composition and/or the behavior of a debonder
agent, can be substantially dictated by the LSCT of the polymer as
opposed to the charges of a specie interacting with fibers.
[0048] Polymer composition can include a homopolymer, a copolymer,
or a blend of polymers. A blend of polymers can include polymers of
different types, e.g., a blend of at least one homopolymer and one
copolymer, a blend of copolymers, a blend of a type of polymer
where the molecules differ in molecular weight and/or branching. In
some embodiments, a blend of polymers of a bulking agent can be
disposed as an emulsion (e.g., a blend of a polymer rich in
polypropylene oxide segments and a polymer rich in polyethylene
oxide segments). The emulsion can allow polymers having different
solubilities to be blended to form an appropriate debonding
agent.
[0049] In some cases, the polymers can have a character that is
different from that of conventional ammonium salts used as
debonders (e.g., being anionic or neutral in nature).
Alternatively, or in addition, the presence of an anchoring group
(such as a cationic group or a chemical group such as epoxy or
anhydride) in a component of the agent can enhance the stability of
the attachment of the agent to a cellulose fiber.
[0050] In some embodiments, the polymer composition can be
formulated to impart a selected transition temperature range for
the cellulose composition. For instance, it can be advantageous to
select the polymer composition such that the transition temperature
is in the range of temperatures relevant to a papermaking process,
e.g., selecting the polymer composition such that wet end
processing of paper typically takes place at temperatures below the
transition temperature and drying takes place at temperatures above
the transition temperature. Accordingly, in some embodiments the
components of the polymer composition (e.g., the polymers of a
blend or the blocks of a copolymer) of a debonder agent are
selected such as to impart a transition temperature for the
fiber-containing composition in a range from about 5.degree. C. to
about 95.degree. C. For example, a polymer composition can be
designed to achieve a certain LCST, and thus impart a corresponding
transition temperature when the composition acts as a portion of a
bulking agent in a fiber-containing composition, by utilizing a
first component having a designated LCST and another component to
modify the first LCST.
[0051] In some particular embodiments, polymers having different
alkylene oxide segment types can be utilized to tailor a transition
temperature in a range from about 5.degree. C. to about 95.degree.
C. For instance, polymers made of propylene oxide monomers exhibit
a LCST of about 5-10.degree. C. while those made with ethylene
oxide exhibit a LCST of .about.90.degree. C. These transition
temperatures are concentration and molecular weight dependent, and
can also be affected by the presence of other components in a
fiber-containing composition. In particular, the ratio of EO and PO
blocks in the molecule can determine the LCST of the resulting
copolymer. A copolymer formed using these components can have an
LCST that falls between these two temperatures, depending on the
relative content of EO and PO blocks in the polymer. Likewise, a
blend of polypropylene oxide polymers and polyethylene oxide
polymers can also be used with the transition temperature dictated
at least in part by the sizes of the individual polymers and their
relative amounts.
[0052] Not to be bound by any particular theory, it is believed
that the bulking molecule binds to the pulp because the temperature
of the aqueous environment reduces the solubility of either or both
the EO or the PO units. In case of block copolymers that contain EO
and PO blocks, increasing the temperature of the polymer solution
in presence of the pulp can lead to selective precipitation of
either the EO or the PO block onto the pulp fibers. The debonder
molecule can be chosen such that the transition temperature of the
composition would be in the range of temperatures seen on a
papermaking line. For example, a composition with a transition
temperature of 35.degree. C. can be deposited into the wet slurry
in the headbox where it would precipitate onto the fibers due to
the fact that the temperature in the headbox is higher
(.about.45.degree. C.) than the transition temperature of the
debonder.
[0053] In some embodiments, commercially available polymers can
display certain advantageous properties of a hydrophilic debonder
imparting a transition temperature that allows its precipitation
during the drying phase of papermaking, as described above, along
with its reversion to a hydrophilic state at room temperature. For
example, the PLURONIC.RTM. line of polyethylene oxide
(PEO)-polypropylene oxide (PPO) block copolymers (BASF) display
these properties when used according to the systems and methods
disclosed herein, as described in Examples below.
[0054] In other embodiments, a molecule can be prepared that
self-assembles around cellulose fibers, thereby preventing hydrogen
bonding between neighboring fibers and leading to bulking of the
final product. As examples, debonder molecules according to these
systems and methods can include oligomeric or polymeric segments
including ethyleneoxide (EO) or propyleneoxide (PO) segments or a
combination of the two with the segments varying in sizes from n=2
to 10000. In embodiments, the temperature-sensitive solubility
behavior of the PPO and PEO blocks in the polymer backbone can
produce an affinity towards the cellulose fibers when the
temperature of the solution is above the transition temperature of
either of the EO or PO based blocks, so that the polymer attaches
itself to the cellulose fiber.
[0055] In other embodiments, the LCST of a polymer composition, and
thus the transition temperature, can be changed by the use of
chaotropic salts such as those based on potassium, sodium, and
calcium. In some embodiments, for example, potassium salts function
well as chaotropic agents for EO based polymers, with the EO blocks
self-assembling around potassium ions forming a crown-ether like
structure. The presence of chaotropic salts can alter the solution
behavior of the debonders by precipitating them out of solution at
temperatures lower than the actual LCST. Without being bound by
theory, it is understood that adding salt to the polymer can change
the structure of water around the molecules, leading to an
association of the polymer with the salt and subsequent
precipitation, effectively lowering the LCST of the polymer. For
example, if a PEO-containing polymer has an LCST of 90.degree. C.,
the presence of a chaotropic salt in the solution (preferably
sodium based) can lower the LCST. Other polymer/salt systems can
exhibit similar behaviors, for example, systems using NaCl and the
like, whereby a polymer/salt arrangement can self-assemble around
the cellulosic fibers. The LCST of the polymer in solution can also
be changed by adding suitable surfactants, for example sodium
dodecylsulfate or sodium laureth sulfate. For example, addition of
sodium dodecylsulfate to a solution of Pluronic L31 [PEO-PPO-PEO]
increased the LCST by about 5.degree. C.
C. Debonders and Increased Stiffness
[0056] It would be understood by those of ordinary skill in the art
that an increase in bulk, as effected by treatment agents such as
the debonders and/or bulking agents described herein, can result in
a concomitant increase in stiffness. As bending stiffness is
directly proportional to the cube of the thickness for a simple
plate like a paper sheet, a doubling of thickness improves the
stiffness by 2.sup.3 times (or 8 times). However, it has been
unexpectedly discovered that debonders and/or bulking agents as
described herein can increase the stiffness of a paper sheet beyond
the amount predicted by the increase in bulk alone. Thus, treatment
agents such as the debonders and/or bulking agents described herein
can act as stiffening agents. A formulation comprising a stiffening
agent can be termed a stiffening formulation.
[0057] Not to be bound by theory, the use of a treatment agent such
as a debonder and/or bulking agent as described herein can separate
the fibers within the paper sheet, creating voids within the paper
that allow the ingress of the starch in the size press mix. The
additional starch imparts more stiffness to the paper product,
beyond the stiffness attributable to the increase in bulk.
Moreover, the debonders and/or bulking agents described herein can
act as plasticizers for the starch used in size press applications,
thereby contributing to an increase in stiffness. Without being
bound by theory, and in addition to any other mechanisms for
viscosity reduction, it can be postulated that a treatment agent,
e.g., a co-solvent bulking agent as described herein, can cause the
starch molecules themselves to contract and thereby reduce system
viscosity.
[0058] Plasticizers reduce the amount of water needed for a wet mix
to achieve fluidic properties for dispersal and the plasticizers
(or co-solvents) also cause the starch molecules to contract by
reducing contact with water molecules thereby further reducing the
viscosity. By decreasing the viscosity of the starch mix, treatment
agents such as the debonding or bulking agents disclosed herein
allow improved penetration of the starch into the fibrous web, so
that there is a greater amount of stiffness-producing starch in the
final sheet; such treatment agents therefore act as stiffening
agents.
[0059] It is understood by skilled artisans that certain optimal
viscosity is desirable for starch solutions added in the size
press, so that the starch can be distributed advantageously onto
the dried paper sheet. Starch in its cooked form absorbs water,
though, and binds it tightly, so that the typical starch solution
for size press applications has a high viscosity with a very low
starch content. Starch pick-up of wet paper is directly
proportional to the viscosity of the sizing solution and the solids
content of it. A viscous starch solution with low starch content
will result in suboptimal levels of starch in the final paper
product, with less desirable stiffness properties. While the starch
content can be increased using conventional technologies, the
viscosity also increases, interfering with the distribution of the
starch within the fibrous network.
[0060] By contrast, the treatment agents described herein can
increase the solids (starch) content of the sizing solution without
increasing the viscosity, allowing improved starch pick-up and
distribution within the paper product. When such a treatment agent
(e.g., a bulking/debonding agent as disclosed herein), is added to
a starch solution, it acts as a plasticizer, so that less water is
needed to achieve the optimal viscosity. One example of such a
plasticizing agent is the glycol-ether class of debonders described
previously. This plasticizing effect can impart additional benefits
by facilitating the drying process for the starch-sized paper
products.
[0061] In another embodiment, the sizing solution containing a
treatment agent such as a bulking/debonding/co-solvent agent as
described herein can also contain a crosslinkable polymer such as
pectin or alginate. Pectin can be crosslinked into a gel with the
help of bivalent ions such as Ca++. Upon drying, the gel forms a
stiff film, enhancing the rigidity of the paper it is applied to.
The pectin crosslinking can be facilitated by an external calcium
ion source such as a calcium-containing salt, or by deliberate
dissolution of PCC that is contained in the paper, having been
added in the wet-end. In an embodiment, a size-press solution
containing pectin can have a lower pH (less than 5) to facilitate
dissolution of PCC, thereby releasing Ca++ ions and enabling
crosslinking of pectin to form a rigid paper.
[0062] In embodiments, therefore, the debonder molecules as
disclosed herein can act as viscosity reducers for the sizing
solution, while also acting as bulking agents that do not remain in
the final paper product. The use of minute amounts of these
treatment agents as co-solvents (i.e., co-ingredients in the
aqueous solution) leads to simultaneous bulking and stiffening,
with the stiffening increasing disproportionately to the increase
in bulk. This phenomenon is demonstrated by the experiments
illustrated in FIG. 10 and described in Example 13 below. As shown
in the graph in FIG. 10, the incorporation of a bulking agent alone
(here, TPnB at 1% and 0.3%) shows improvement in stiffness compared
to the starch sized paper (normalized to starch 4%), due to the
accompanying bulking which has a power law relation to stiffness.
However, a significant and unexpected improvement in stiffness
occurs when the bulking agent is combined with starch. It is
hypothesized, without being bound by theory that the
bulking/debonding effect of the TPnB creates pathway and space for
the starch to penetrate and occupy within the interstices of the
paper thereby strengthening and stiffening the paper upon drying.
The impact upon stiffness of this phenomenon is enhanced by the
effect of the bulking/debonding agent on the viscosity of the
starch solution, whereby a lowered viscosity improves its ability
to penetrate the fibrous network.
[0063] In embodiments, these same phenomena (debulking and
viscosity reduction) can be employed to improve the penetration of
other advantageous compounds into a fibrous matrix, for example in
papermaking. Such advantageous compounds can include oil/grease
resistance agents, optical brighteners, ink binders, dust
preventers, water repellents, stiffeners, biocides, biomolecules
for controlled release, gloss strength builders, colorants,
adhesion release agents, and other performance-enhancing agents
(e.g., diagnostic sensors, biomedical components, filtration
assists, targeted capture/sequestrants agents, and the like). In an
embodiment, superabsorbent polymers can be added to a fibrous
matrix using these technologies, with the superabsorbent polymer
being packaged so as not to imbibe moisture due to the presence of
the plasticizer/co-solvent.
EXAMPLES
Materials
[0064] In the examples below, the following materials were used
(unless otherwise indicated, percentages are weight percentages):
[0065] Softwood pulp [0066] Processed pulp sheets (670 GSM basis
weight) [0067] Poly propylene oxide polymer (PPO) [0068] Copolymers
of PPO and PEO (Polyethyeleneoxide) in the Pluronics series of
polymers from BASF [0069] Butyl Carbitol (Dow) [0070] Butyl
Cellusolve (Dow) [0071] DOWANOL.RTM. compounds as listed in the
following Table 1:
TABLE-US-00001 [0071] TABLE 1 DOWANOL .RTM. compounds (DOW Corp.,
Midland, MI) Evaporation Name MW time and temp. HLB DPM
(dipropylene 148.2 Mid to slow Hydrophilic ~8.2 glycol methyl
evaporating, ether) bp = 190 C., flp = 75 C. DPnB (dipropylene
190.3 Slow evaporating, Hydrophobic ~6.8 glycol n-butyl bp = 230
C., ether) flp = 100.4 C. DPnP (dipropylene 176.2 Slow evaporating,
Hydrophilic/ glycol n-propyl bp = 213 C., Hydrophobic ~7.2 ether)
flp = 88 C. PGDA (propylene 160 Bp = 190 C., glycol diacetate) flp
= 95 C. PM (Propylene 90.1 Fast evaporating, Hydrophilic ~8.3
glycol methyl bp = 120 C., ether) flp = 31 C. PnB (propylene 132.2
Fast evaporating, Hydrophobic ~6.9 glycol n-Butyl bp = 171 C.,
ether) flp = 63 C. PnP (propylene 118.2 Fast evaporating,
Hydrophilic/ glycol n-propyl bp = 149 C., hydrophobic ~7.4 ether)
flp = 48 C. PPh (propylene 152.2 Slow evaporating, Very hydro-
glycol phenyl bp = 243 C., phobic ~5.9 ether) flp = 115 C. TPM
(Tripropylene 206.3 Slow evaporating, Hydrophilic ~8 glycol methyl
bp = 243 C., ether) flp = 121 C. TPnB (tripropylene 248.4 Slow
evaporating, Hydrophobic ~6.6 glycol n-butyl bp = 274 C., ether)
flp = 126 C. DMM (dipropylene 162.23 bp = 175 C., Aprotic ~7 glycol
dimethyl flp = 65 C. ether)
The HLB properties for these products are set forth on FIG. 2.
[0072] JEFFAMINE.RTM. products (Huntsman Chemicals)
TABLE-US-00002 [0072] TABLE 2 JEFFAMINE .RTM. compounds Jeffamine
D-2000 diamine Polyetheramine Jeffamine D-400 Jeffamine M-2070
Jeffamine XTJ 548 Jeffamine XTJ-500 diamine (EO based)
Polyetheramines ED-600 Jeffamine XTJ-501 diamine (EO based)
Polyetheramine ED-900 Jeffamine XTJ-502 diamine (EO based)
Polyetheramine ED-2003 Jeffamine XTJ-505 (M600) Jeffamine XTJ-506
(M-1000) Jeffamine XTJ-507 (M-2005) Jeffamine XTJ-507 (M2005)
monoamine polyetheramine Jeffamine XTJ-509 (T-3000) triamine
Polyetheramine Jeffamine XTJ-542 (Diamine, M~1000, based on
[poly(tetramethylene ether glycol)]/PPG copolymer) Jeffamine
XTJ-559 (Diamine, M~1000, based on [poly(tetramethylene ether
glycol)]/PPG copolymer) Jeffamine XTJ-576 (SD-2001) (D-2000 based
but both ends are secondary amine) Jeffamine XTJ-585 (SD-401)
(D-400 based but both ends are secondary amine)
Example 1
Handsheet Preparation
[0073] To prepare handsheets of .about.200 grams per square meter
(GSM) a 0.5% fluff pulp slurry was thoroughly dispersed using an
overhead mixer. To this, appropriate amounts of 2% Dowanol solution
were added to create a specific concentration of the Dowanol in the
water, as described in the Examples below. These constituents were
mixed for 30 s and then put into the handsheet mold. Shear was
applied using an overhead stirrer mixing at 1100 rpm for 5 seconds,
700 rpm for 5 seconds, and then 400 rpm for 5 seconds. Following
this, the sample in the mold was allowed to drain and vacuum was
applied to remove excess water. The resultant sheet was blotted,
pressed, and dried in rings in the oven at 110.degree. C. for 14
minutes.
Example 2
Caliper Measurements
[0074] The thickness or the caliper was measured using a digital
caliper for paper strips treated with volatile debonders by dipping
1'' by 6'' strips of 670 GSM basis weight paper strips for
approximately 30 seconds in 50 mL centrifuge tubes containing
solutions containing debonder compounds in deionized water at
concentration ranging from 1%/wt, to 0.01%/wt until the strips were
saturated. The resulting samples were then pressed and dried at
110.degree. C. for 20 minutes. For these experiments, samples were
prepared using compounds listed in the materials section, with an
untreated sample as the control.
Example 3
Tensile Strength Measurement
[0075] Tensile tests were conducted on control and experimental
samples using an Instron 3343. Samples of sheets for tensile
testing were initially cut into 1 inch (in) wide strips with a
paper cutter, and then attached within the Instron 3343. The gauge
length region was set at 4 in and the crosshead speed was 1
in/minute. Thickness was measured to provide stress data as was the
weight to be able to normalize the data by weight of samples. The
strips were tested to failure with an appropriate load cell. At
least three strips from each control or experimental handsheet
sample were tested and the values were averaged together.
Example 4
Measurement of Cross Section Using Caliper and Microscopy
[0076] Microscopic images were captured with a Zeiss Axio
microscope using an EC Epiplan-NEOFLUAR 20.times. objective lens
and digitalized with an Axio MRCS camera. Cross sections in MD and
CD were prepared using a 15T sterile disposable scalpel and
straight-edge. Microscopic images were digitally analyzed with
AxioVision Rel. 4.8.2 for Zeiss. An example of microscopy images
showing bulking improvement is shown in FIG. 3. FIG. 3A shows the
microscopic image of a control sample. FIG. 3B shows a microscopic
image of a sample that was treated with a 1% solution of TPnB
glycol ether in 4% starch solution.
Example 5
Wet End Addition of Volatile Debonder
[0077] Handsheet samples were prepared using the method in Example
1. Dowanol TPnB were applied to the handsheets at concentrations of
0.01%, 0.025%, 0.049%. The caliper of the handsheet samples was
measured using the methods in Example 2. The results of these tests
are shown in the graph in FIG. 4. As shown in this Figure,
handsheet samples treated with TPnB showed a greater increase in
caliper as a function of its concentration in the white water, with
a maximum caliper increase of about 8% with a TPnB concentration of
0.025%.
Example 6
Thermogravimetry (TG) and TG-Mass Spectrometry (TG-MS) Testing
[0078] Samples were prepared using the method in Example 1, using
0%, 0.049%, and 0.095% Dowanol TPnB. Other samples were prepared
with the same concentrations but with skipping the drying step from
Example 1. The wet samples were tested using TG to examine any
changes in the weight loss profile, and the dry samples were tested
using TG-MS to determine the amount of the residual debonder on the
fibers. It was observed that the use of the volatile debonder did
not significantly affect the weight loss of the wet sample. These
tests also did not demonstrate any residual debonder on the dry
sample (TG-MS scan profiles were the same for controls and treated
samples).
Example 7
Preparation of Sizing Solutions with Bulking Additives
[0079] Bulking solutions were prepared from a 4% cooked starch
stock solution. The stock solution was prepared by heating 4%
solids by weight granulated ethylated starch in deionized water.
The mixture was heated to 65.degree. C. while stirring and held at
constant temperature for 10 minutes and immediately cooled in an
ice bath. Starch solution samples were taken during and after
cooking to ensure complete cooking and no degradation. Viscosity of
the stock starch solution was tested at room temperature
(20.degree. C.) at 60, 100, and 150 rpm. Bulking solutions were
made by adding undiluted debonding agent/bulking agent to stock
starch solution.
Example 8
Size Press Application of Debonder to Improve Sheet Bulking
[0080] Sheet bulking samples were prepared by cutting 1''.times.1''
squares and 1''.times.7'' strips (CD) from unsized sheets, weighed,
and dipped into the bulking solutions for 10 seconds each. Control
samples were dipped into deionized water (blank) and starch stock
solution. After dipping, they were placed between two metal plates
and pressed with a constant-pressure metal roller. They were dried
on a speed dryer at 150 degrees C. and re-weighed after
conditioning to 50% relative humidity. The results of these tests
are set forth in the graphs on FIG. 5.
Example 9
Tensile Strength of Papers with Improved Bulking
[0081] The effect of debonding molecules in the sizing solution was
investigated as a function of TPnB concentration in 4% starch
solution. The graph in FIG. 6 shows that there is no tensile
strength loss when TPnB is added at concentrations up to 0.3%,
while higher concentrations up to 0.3% show a tensile loss of
10-20% is observed when normalized by the sample sized with starch
alone.
Example 10
Screening of Debonding Chemicals
[0082] A selection of glycol ethers, including TPnB, TPM and BCAR,
were compared to PPO-containing molecules such as Jeffamine XTJ-500
and Jeffamine D-2000 by using the protocol described in Examples 2
and 8. The graph in FIG. 7 shows the bulking improvement obtained
by an addition of 0.5% by weight of each debonding molecule to a 4%
starch sizing solution.
Example 11
Taber Stiffness analysis
[0083] The prepared sheets containing cooked starch and TPnB were
conditioned to 45% RH for 2 hours. The samples were prepared using
a 1.50''.times.2.75'' Triple Cut Specimen Shear (Model 104-11,
Taber Industries, N. Tonawanda, N.Y., USA), with 5 samples per
condition in the machine direction. The samples were then tested on
a Taber V-5 Stiffness Tester (Model 150-B, Taber Industries, N.
Tonawanda, N.Y., USA) with a Ten Unit Compensator Weight (for
samples between 0-10 Taber Stiffness Units). In accordance with the
method as expressed in TAPPI 489, each sample was tested 15 degrees
in the left and right direction and the stiffness was recorded as
an average of the two readings, in Taber Stiffness Units. The
readings were recorded and are expressed as an average per
condition (n=5) and are shown in FIG. 8.
Example 12
Measurement of Viscosity of Starch Solutions
[0084] A solution of cooked 8% Penford Gum 270 ethylated starch was
prepared. 250 mL of the solution was transferred to a glass beaker
and heated to 55.degree. C. on a constant-temperature stir plate in
conjugation with a Brookfield Rheometer (Model LVDV-III+,
Brookfield Engineering Laboratories, Middleboro, Mass., USA) with
external control (Rheocalc V2.4 Software) that was zeroed and
fitted with an LV-2 spindle. A viscosity reading was taken of the
cooked 8% starch solution, and then 0.25 mL (0.1%) TPnB was added.
After 5 minutes of mixing, another reading was taken. This was
repeated for readings at 0.2%, 0.3%, 0.4% and 0.5%. After 0.5%,
0.625 mL (0.25%) TPnB was added and a reading of 0.75% TPnB
concentration was taken, after 5 minutes another 0.625 mL was added
and a reading of 1% TPnB was taken. The viscosity vs. TPnB
concentration graph is shown in FIG. 9.
Example 13
Taber Stiffness Analysis
[0085] Samples were prepared and tested as set forth in Example 11.
Results are set forth in FIG. 10. The data in the graph of FIG. 10
demonstrate the benefit in improved stiffness obtained by using the
bulking agent with starch in the sizing solution.
EQUIVALENTS
[0086] While specific embodiments of the subject invention have
been disclosed herein, the above specification is illustrative and
not restrictive. While this invention has been particularly shown
and described with references to preferred embodiments thereof, it
will be understood by those skilled in the art that various changes
in form and details may be made therein without departing from the
scope of the invention encompassed by the appended claims. Many
variations of the invention will become apparent to those of
skilled art upon review of this specification. Unless otherwise
indicated, all numbers expressing reaction conditions, quantities
of ingredients, and so forth, as used in this specification and the
claims are to be understood as being modified in all instances by
the term "about." Accordingly, unless indicated to the contrary,
the numerical parameters set forth herein are approximations that
can vary depending upon the desired properties sought to be
obtained by the present invention.
[0087] While this invention has been particularly shown and
described with references to preferred embodiments thereof, it will
be understood by those skilled in the art that various changes in
form and details may be made therein without departing from the
scope of the invention encompassed by the appended claims.
* * * * *