U.S. patent application number 14/276305 was filed with the patent office on 2014-12-11 for debonders for use in papermaking.
This patent application is currently assigned to NANOPAPER, LLC. The applicant listed for this patent is NANOPAPER, LLC. Invention is credited to Lynn D. Bell, Gangadhar Jogikalmath, Scott I. Rabin, David S. Soane.
Application Number | 20140360690 14/276305 |
Document ID | / |
Family ID | 41716680 |
Filed Date | 2014-12-11 |
United States Patent
Application |
20140360690 |
Kind Code |
A1 |
Jogikalmath; Gangadhar ; et
al. |
December 11, 2014 |
DEBONDERS FOR USE IN PAPERMAKING
Abstract
Debonding compositions and methods are disclosed for use in
fibrous compositions such as paper-based products. In some
instances, debonding agents can be combined with fibers (e.g.,
cellulose-based fibers) to produce a material having substantial
wicking properties while decreasing fiber-fiber interactions that
can require substantial energy to overcome in materials processing.
In some instances, the debonding agent can act to create a
paper-based product exhibiting a transition temperature in which
the agent has a higher affinity for the fibers at temperatures
above the transition temperature, and the product exhibiting
enhaced wicking properties at temperatures below the transition
temperature. As an example, a debonding agents can include polymers
or other material exhibiting a lower critical solution temperature.
The disclosed debonding agents can provide benefits over existing
debonding agent formulations such as ammonium salts.
Inventors: |
Jogikalmath; Gangadhar;
(Cambridge, MA) ; Bell; Lynn D.; (Stow, OH)
; Rabin; Scott I.; (Coral Gables, FL) ; Soane;
David S.; (Chestnut Hill, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NANOPAPER, LLC |
Cambridge |
MA |
US |
|
|
Assignee: |
NANOPAPER, LLC
Cambridge
MA
|
Family ID: |
41716680 |
Appl. No.: |
14/276305 |
Filed: |
May 13, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13178053 |
Jul 7, 2011 |
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14276305 |
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PCT/US10/20440 |
Jan 8, 2010 |
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13178053 |
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61143252 |
Jan 8, 2009 |
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Current U.S.
Class: |
162/164.3 |
Current CPC
Class: |
D21H 21/24 20130101;
D21H 17/37 20130101; D21H 17/36 20130101; D21H 21/22 20130101; D21H
17/52 20130101; D21H 17/35 20130101; D21C 9/005 20130101 |
Class at
Publication: |
162/164.3 |
International
Class: |
D21H 17/52 20060101
D21H017/52 |
Claims
1. A fiber-containing composition suitable for use to improve fluid
distribution, comprising: a fibrous material comprising fibers; and
a debonding agent comprising a polymer composition exhibiting a
lower critical solution temperature (LCST), the fiber-containing
composition exhibiting a transition temperature such that: (i) the
debonding agent has a higher affinity for the fibers when the
temperature is above a transition temperature relative to when the
temperature is below the transition temperature; and (ii) the
debonding agent enhances fluid distribution in the fiber-containing
composition when the temperature of the debonding agent is below
the transition temperature relative to when the temperature is
above the transition temperature.
2. The fiber-containing composition of claim 1, wherein the
fiber-containing composition is substantially free of ammonium salt
in an amount capable of substantially affecting wicking of the
fiber-containing composition.
3. (canceled)
4. (canceled)
5. The fiber-containing composition of claim 1, wherein the
debonding agent comprises a plurality of alkylene oxide units.
6. The fiber-containing composition of claim 5, wherein the
debonding agent comprises at least one of polyethylene oxide units
and polypropylene oxide units.
7. The fiber-containing composition of claim 5, wherein the
debonding agent comprises a polymer with two distinct
alkylene-oxide units, each alkylene-oxide unit exhibiting a
different LCST at a given concentration and molecular weight
distribution.
8. (canceled)
9. The fiber-containing composition of claim 1, wherein the
transition temperature is between about 5.degree. C. and about
95.degree. C.
10. (canceled)
11. (canceled)
12. A method of improving wicking of a fiber-based material
comprising: providing a fiber-containing composition comprising a
polymeric debonding agent disposed with a plurality of fibers, a
polymer of the polymeric debonding agent exhibiting lower critical
solution temperature (LCST) behavior; and subjecting the
fiber-containing composition to a temperature below a transition
temperature such that the fiber-containing composition exhibits
enhanced wicking relative to a fiber-containing composition without
the debonding agent.
13. The method of claim 12, wherein the fiber-containing
composition is substantially free of ammonium salt in an amount
capable of substantially affecting wicking of the fiber-containing
composition.
14. (canceled)
15. (canceled)
16. The method of claim 12, wherein the debonding agent comprises a
plurality of alkylene oxide units.
17. The method of claim 12, wherein the debonding agent is
substantially free of a charged specie.
18. (canceled)
19. The method of claim 12, wherein the step of providing the
fiber-containing composition comprises: forming a mixture
comprising at least a portion of the fiber-containing composition
at a temperature below the transition temperature; and drying the
mixture to provide the fiber-containing composition.
20. (canceled)
21. (canceled)
22. The method of claim 19, wherein the step of drying the mixture
comprises subjecting the mixture to a temperature above the
transition temperature.
23. (canceled)
24. (canceled)
25. A method of utilizing a debonder in a paper-based composition,
comprising: inserting a debonder composition in a paper-based
mixture including fibers, the debonder composition comprising: (i)
at least one polymeric component exhibiting a lower critical
solution temperature (LCST), and (ii) at least one modifying
component, the modifying component selected to alter the LCST of
the at least one polymeric component so that the altered LCST falls
within a temperature range between about 5.degree. C. and about
95.degree. C.
26. The method of claim 25, wherein the at least one polymeric
component comprises a first block of a copolymer.
27. The method of any one of claim 26, wherein the at least one
modifying component comprises a second block of the copolymer.
28. The method of claim 27, wherein the copolymer comprises a
plurality of alkylene-oxide unit types.
29. The method of claim 28, wherein the plurality of alkylene-oxide
unit types comprises at least one of an ethylene-oxide and a
propylene oxide.
30. (canceled)
31. (canceled)
32. The method of claim 25, wherein the at least one polymeric
component comprises a first polymer characterized by a first repeat
unit and the at least one modifying comprises a second polymer
characterized by the first repeat unit, the first polymer and the
second polymer differing in at least one of molecular weight,
branching, and the first polymer having a second repeat unit not
present in the second polymer.
33. (canceled)
34. The method of claim 25, further comprising: maintaining the
paper-based mixture at a temperature above a transition temperature
to inhibit adhesion between at least a plurality of fibers of the
paper-based mixture.
35. The method of claim 34, further comprising: maintaining the
paper-based mixture at a temperature below the transition
temperature such that the at least one polymeric component exhibits
hydrophilic behavior.
36. (canceled)
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 13/178,053, filed Jul. 7, 2011, which is a continuation of
International Application No. PCT/US2010/020440, which designated
the United States and was filed on Jan. 8, 2010, published in
English, which claims the benefit of U.S. Provisional Application
No. 61/143,252, filed on Jan. 8, 2009. The entire teachings of the
above applications are incorporated herein by reference.
FIELD OF THE APPLICATION
[0002] This application relates generally to hydrophilic debonders
for defiberizing pulp boards.
BACKGROUND
[0003] Fast wicking of liquids is desirable in many commercial
products such as diapers, personal hygiene, sanitary products, etc.
Usually this is achieved by converting paperboard products into
defiberized fluff pulp that has a high surface area to enable fast
wicking Such fluff pulp is utilized in a variety of different
designs to enable wicking of bodily fluids from the point of
insult.
[0004] Fluff pulp is formed from paperboards made by conventional
papermaking technologies. The absorbent core for hygienic products
is typically manufactured on a continuous production line in which
wood fluff pulp is provided as a sheet (manufactured, for example,
by a wet-laid process) and is defiberized mechanically using means
such as a hammermill. The defiberized fluff pulp is then air-laid
with particles of superabsorbent polymers or other super-absorbent
materials capable of absorbing up to one hundred times their weight
in water, thereby forming the absorbent core for the product.
[0005] Formation of fluff pulp from paperboard depends on
mechanical mechanisms to break the strong intermolecular hydrogen
bonds that form between neighboring cellulose fibers during the
papermaking process. A significant amount of energy is required to
overcome the strength of the intermolecular bonds and break a
paperboard into individual fibers.
[0006] Because the energy required for mechanical breakdown methods
is expensive, alternate technologies have been employed to reduce
the formation of hydrogen bonds during papermaking As an example,
debonder compounds are used for this purpose. Debonders bind to the
fiber surface, preventing the formation of hydrogen bonds by acting
as a spacer between neighboring cellulose molecules and fibers.
[0007] Many approaches in the art use quaternary ammonium salts as
debonders. Such debonders contain a cationic group that attaches
the molecule to the anionic fiber surface, and a hydrophobic chain
that acts like a spacer between cellulose fibers/molecules. With
fewer bonds between fibers, less energy is required to break the
fibers apart. Although these debonders can reduce the energy
required to produce fluff pulp, the hydrophobic moiety decreases
the wicking property of the resulting fluff pulp. Hence there is a
need for an approach that reduces the hydrogen bonding while
unaffecting the hydrophilicity of the fluffed pulp. Desirably, an
appropriate debonder would both decrease the energy of
defiberization and maintain comparable or improved wicking
speeds.
SUMMARY
[0008] In some aspects of the invention, fiber-containing
compositions are disclosed that are suitable for use in improving
fluid distribution in materials such as paper-based materials
and/or at least a portion of an absorbent fiber-based article. The
fiber-containing compositions can include a fibrous material
comprising fibers. A debonding agent can impart the
fiber-containing composition with a transition temperature such
that the debonding agent has a higher affinity for the fibers when
the temperature is above a transition temperature relative to when
the temperature is below the transition temperature, and/or the
debonding agent enhances fluid distribution in the fiber-containing
composition when the temperature of the debonding agent is below
the transition temperature relative to when the temperature is
above the transition temperature. Such fiber-containing
compositions can include, or be substantially free of, a
conventional debonding agent such as a salt (e.g., ammonium salt)
or other charged specie; for example, free of the salt and/or
charged specie such that the presence of any such specie does not
affect the wicking of the fiber-containing composition and/or the
LCST behavior of a polymer composition in the debonding agent.
[0009] In some embodiments of the invention, the debonding agent
comprises a polymer composition exhibiting a lower critical
solution temperature (LCST). The polymer composition can include a
copolymer and/or a blend of different polymer molecules. In
particular embodiments, the debonding agent can comprise a
plurality of alkylene oxide units. In some embodiments, the
debonding agent can comprise at least one of polyethylene oxide
units and polypropylene oxide units. The debonding agent can
comprise a polymer with two distinct alkylene-oxide units, each
alkylene-oxide unit can exhibit a different LCST at a given
concentration and molecular weight distribution. In some
embodiments herein, a debonding agent can be substantially free of
a charged specie (e.g., an ammonium salt, a polyelectrolyte, or
other specie carrying an ionic charge).
[0010] In some embodiments, the fiber-containing composition
exhibits a transition temperature in a range between about
5.degree. C. and about 95.degree. C. In some embodiments, the
fiber-containing compositions disclosed herein can comprise a
transition temperature-modifier capable of changing the LCST of the
debonder agent in the fiber-containing composition. Such a LCST
modifier can comprise at least one of a chaotropic salt and a
surfactant.
[0011] Other aspects of the invention are directed to methods of
improving wicking of a fiber-based material as disclosed herein
(e.g., an absorbent fiber-based article). Such methods can include
the steps of providing a fiber-containing composition comprising a
polymeric debonding agent disposed with a plurality of fibers; and
subjecting the fiber-containing composition to a temperature below
a transition temperature such that the fiber-containing composition
exhibits enhanced wicking relative to a fiber-composition without
the debonding agent.
[0012] The polymeric debonding agent can be consistent with any of
the debonding agents including a polymer composition as disclosed
herein (e.g., a copolymer or a blend of different polymer
molecules). For instance, the polymer composition can exhibit LCST
behavior. In embodiments, the fiber-containing composition
optionally includes an ammonium salt. In another embodiment, the
fiber-containing composition can be free of ammonium salt, or
substantially free of ammonium salt (e.g., in an amount capable of
substantially affecting wicking of the fiber-containing
composition). In embodiments, the debonding agent can comprise a
plurality of alkylene oxide units. In embodiments, the
fiber-containing composition can comprise a transition temperature
modifier capable of changing the LCST of the debonding agent in the
fiber-containing composition, the transition temperature modifier
comprising at least one of a chaotropic salt and a surfactant.
[0013] In some embodiments, the step of providing the
fiber-containing composition comprises forming a mixture comprising
at least a portion of the fiber-containing composition; and drying
the mixture to provide the fiber-containing composition. The step
of forming the mixture, which is optionally performed at a
temperature below the transition temperature, can comprise forming
the mixture with the debonding agent. In embodiments, the debonding
agent can be applied while the mixture is being dried. The step of
drying the mixture can comprise subjecting the mixture to a
temperature above the transition temperature. The step of drying
can comprise using the debonding agent to inhibit hydrogen bonding
between at least some fibers during the step of drying.
[0014] In other aspects of the invention, methods of utilizing a
debonder in a paper-based composition are disclosed. The method can
comprise inserting a debonder composition in a paper-based mixture
including fibers. The debonder composition can include at least one
polymeric component exhibiting a LCST) and at least one modifying
component. The modifying component can be selected to alter the
LCST of the at least one polymeric component so that the altered
LCST falls within a temperature range between about 5.degree. C.
and about 95.degree. C.
[0015] In some embodiments, the at least one polymeric component
comprises a first block of a copolymer. In some embodiments, the at
least one modifying component comprises a second block of the
copolymer. The copolymer can optionally comprise a plurality of
alkylene-oxide unit types. The plurality of alkylene-oxide unit
types can comprise at least one of an ethylene-oxide and a
propylene oxide. The at least one polymeric component can comprise
a first polymer comprising a repeat unit type, and the at least one
modifying component can comprise a second polymer comprising a
different repeat unit type. For instance, the repeat unit type
comprises an alkylene-oxide unit type, and the different repeat
unit type comprises a different alkylene-oxide unit type. In some
embodiments, the at least one polymeric component comprises a first
polymer characterized by a first repeat unit or a selected polymer
type and the at least one modifying comprises a second polymer
characterized by the first repeat unit or the selected polymer
type, the first polymer and the second polymer differing in at
least one of molecular weight, branching, and the first polymer
having a second repeat unit not present in the second polymer. In
some embodiments, the at least one modifying component can comprise
a chaotropic salt and/or a surfactant.
[0016] The methods disclosed herein can further comprise the step
of maintaining the paper-based mixture at a temperature above a
transition temperature to inhibit adhesion between at least a
plurality of fibers of the paper-based mixture. The methods
disclosed herein can further comprise the step of maintaining the
paper-based mixture at a temperature below the transition
temperature such that the at least one polymeric component exhibits
hydrophilic behavior.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Aspects of the present invention will be more fully
understood from the following detailed description taken in
conjunction with the accompanying drawings (not necessarily drawn
to scale), in which:
[0018] FIG. 1 presents a bar graph depicting the measured tensile
strength in lb.sub.f/in and measured wicking time in seconds for
various samples of Example 8, the height of the bars indicating
tensile strength on the left hand side of the graph, and the dots
corresponding to each bar indicating the wicking time on the right
hand side of the graph;
[0019] FIG. 2A presents a bar graph compares the measured tensile
strength in lb.sub.f/in. and measured wicking time in seconds for a
control sample, a sample utilizing an embodiment of the invention,
and a conventional debonder sample tested in Example 8, the height
of the bars indicating tensile strength on the left hand side of
the graph, and the dots corresponding to each bar indicating the
wicking time on the right hand side of the graph;
[0020] FIG. 2B presents a graph of measured wicking time in seconds
against force for debonding in lb.sub.f/in. for the samples plotted
in FIG. 2A, the types of samples are segregated in different
locations of the graph as labeled;
[0021] FIG. 3A presents a graph of measured tensile strength in
lb.sub.f/in. against weight percent concentration of L31 debonder
in accord with the test results of Example 9, the bars
corresponding with the range of tested results;
[0022] FIG. 3B presents a graph of measured wicking time in seconds
against weight percent concentration of L31 debonder in accord with
the test results of Example 9, the bars corresponding with the
range of tested results; and
[0023] FIG. 4 presents a bar graph depicting the measured maximum
load/strip width in lb.sub.f/in. and measured wicking time in
seconds for a control sample, a conventional debonder sample, and a
sample utilizing an embodiment of the invention and the
conventional debonder tested in Example 10, the height of the bars
indicating tensile strength on the left hand side of the graph, and
the dots corresponding to each bar indicating the wicking time on
the right hand side of the graph.
DETAILED DESCRIPTION
[0024] Disclosed herein are systems, compositions, and methods for
making and using debonders to reduce bonding between fibers while
preserving or enhancing wicking properties in a material made using
the fibers (e.g., a fluff pulp). In some embodiments, debonding
agents can be combined with fibers (e.g., cellulose-based fibers)
to produce a material having substantial wicking properties while
decreasing fiber-fiber interactions that can require substantial
energy to overcome in materials processing. The debonding agent can
act to create a paper-based product exhibiting a transition
temperature in which the agent has a higher affinity for the fibers
at temperatures above the transition temperature, and a product
exhibiting enhaced wicking properties at temperatures below the
transition temperature. The disclosed debonding agents can provide
benefits over existing debonding agent formulations, such as
ammonium salts, by exhibiting improved wicking performance while
still decreasing fiber-fiber interactions. Accordingly, in some
embodiments, a debonder agent can be substantially free of salt
and/or charged species. In some instances, the presence of a
charged specie can hinder performance of debonders such as are
disclosed herein (e.g., by decreasing wicking and/or affecting
debonder interactions with the fibers).
[0025] In some embodiments, a debonding agent can include a 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 be useful for enhancing wicking properties of fiber-containing
compositions while hindering fiber-fiber attractions. It is
understood that many agents (e.g., polymers) exhibit a
temperature-dependent solubility phenomenon called Lower Critical
Solution Temperature (LCST). Such agents, including 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.
[0026] In embodiments, the LCST property of certain polymers can be
used to support a class of debonder agents especially suitable for
use in manufacturing liquid wicking materials such as fluff pulp
because the papermaking exposes the pulp and additives to different
temperatures during the manufacturing process. In some embodiments,
the LCST of the debonder agent component acts to provide a
transition temperature in the fiber-containing material utilizing
the debonder agent. While this transition temperature is often
close, if not the same, as the LCST, the presence of the other
components of the material, or other environmental factors or
components, can act to offset the transition temperature from the
LCST. In some embodiments, a debonder can impart a sufficiently low
transition temperature, thereby effectively reducing the solubility
of the debonder at temperatures above the transition temperature.
While not necessarily being limited to any particular theory, it is
believed that the reduction in solubility tends to deposit the
debonder on fiber surfaces, which can help inhibit fiber-fiber
attractions due to hydrogen bonding. At temperatures below the
transition temperature, which may include ambient use temperatures
of a wicking material, it is believed that the debonder can become
soluble, thereby enhancing fluid distribution through the fiber
network, e.g., relative to the use of conventional ammonium salt
debonders which are hydrophobic and hinder wicking between the
fibers.
[0027] It is understood that while many fiber-containing
compositions described herein utilize the described debonders in
the context of making water-based wicking materials, these concepts
can readily be applied to organic-based wicking materials or
non-aqueous based wicking materials. For instance, fibrous
materials could utilize synthetic fibers that are organophilic.
Accordingly, appropriate debonder agents imparting a transition
temperature (e.g., an organophilic polymer composition having a
LCST) such that the agent tends to deposit on the synthetic fiber
above the transition temperature and become soluble below the
transition temperature can also be utilized.
[0028] Embodiments of debonders can be designed to enable addition
at different points along the paper making line. In embodiments,
the debonder molecule can be added at the wet end or after the
slurry has been deposited onto the moving wire, e.g., at a
temperature below the transition temperature such that the debonder
component is water soluble when added to the slurry. In the drying
process of papermaking, the temperature will be elevated above the
transition temperature, causing the debonder component to
precipitate out of solution onto the fiber surface. This
precipitation may help in the drying process by inhibiting the
hydrogen bonding between neighboring fibers. After the sheet is
dried, the temperature of the paper falls below the transition
temperature, so that the molecule reverts back to a hydrophilic
state. This enhances the wicking properties of the dried paper
sheet, because the now-hydrophilic debonder does not prevent flow
of water through the fibrous web, as do many debonders in current
use.
[0029] A variety of debonding agents can be utilized with
embodiments of the present invention. In many instances, various
types of polymer compositions that exhibit LCST behavior can be
utilized. 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.
[0030] Polymer compositions used in debonder agents can be utilized
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.
[0031] 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 debonder 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.
[0032] 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 a debonding agent can enhance the
stability of the attachment of the debonder to a cellulose
fiber.
[0033] In some embodiments, the polymer composition can be
formulated to impart a selected transition temperature range for
the fiber-containing composition utilizing the debonder agent. 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 debonder agent in a
fiber-containing composition, by utilizing a first component having
a designated LCST and another component to modify the first LCST.
In some particular embodiments, polymer 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 around 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.
[0034] Herein, features of a polymer composition utilizing PPO
segments and PEO segments are disclosed. It is understood, however,
that such features can also be imparted generally to other polymer
composition consistent with other embodiments of the present
invention. Accordingly, such features are not confined to PEO/PPO
segment compositions, and can be extended generally to other
polymer compositions that can physically achieve such features,
consistent with embodiments of the present invention.
[0035] Not to be bound by any particular theory, it is believed
that the debonder 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.
[0036] It will be appreciated by those of ordinary skill in the art
that the behavior of the subject polymers as disclosed herein
contrasts with that of other debonders that are hydrophobic at
ambient temperatures. A hydrophobic debonder will impede flow of
water through the fibrous web of the paper product. By contrast,
the hydrophilic character of debonders as disclosed herein can
facilitate water transport through the fibrous web of the paper
product, a desirable behavior in a fluff pulp material.
[0037] 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.
[0038] In other embodiments, a debonder molecule can be prepared
that self-assembles around cellulose fibers, thereby preventing
hydrogen bonding between neighboring fibers. In embodiments, the
debonder molecule can be a polymer.
[0039] 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=2-10000. 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.
[0040] 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.
EXAMPLES
[0041] The following examples are provided to illustrate some
aspects of the present application. The examples, however, are not
meant to limit the practice of any embodiment of the invention.
Materials
[0042] In the examples below, the following materials were used
(unless otherwise indicated, percentages are weight
percentages):
TABLE-US-00001 TABLE A PLURONIC .RTM. polymers (BASF Corp., New
Jersey) Polymer MW v (dynes/cm) wt % PEG Cloud pt (.degree. C.)
Pluronic L31 1100 47 10 37 Pluronic L35 1900 79 50 73 Pluronic L121
4400 33 30 14 Pluronic L81 2800 10 20 Pluronic L64 2900 43 40 58
Pluronic F68 8400 50 80 >100 Pluronic F127 12600 41 >100
TABLE-US-00002 TABLE B PROSOFT .RTM. ammonium salt-containing
debonders (Hercules, Inc., Wilmington DE) PROSOFT .RTM. TQ2021 NE
PROSOFT .RTM. TQ2028
[0043] Softwood pulp [0044] Processed pulp sheets
Example 1
Control Pulp
[0045] A 0.6% slurry was prepared by mixing 84.45 g refurnished
softwood pulp (22.5% solids) in 3 L of water for 6-10 minutes.
Example 2
Handsheet Preparation
[0046] Handsheets were prepared using a Mark V Dynamic Paper
Chemistry Jar and Hand-Sheet Mold from Paper Chemistry Laboratory,
Inc. (Larchmont, N.Y.). The appropriate volume of 0.6% pulp slurry
was functionalized with the appropriate polymer(s) (based on dry
weight), as listed above. Polymer additions were done at 10 minute
intervals. This combined slurry was added to the handsheet maker.
The slurry was mixed at a rate of 1100 RPM for 5 seconds, 700 RPM
for 5 seconds, and 400 RPM for 5 seconds. The water was then
drained off. The subsequent sheet was then transferred off of the
wire, pressed and dried.
Example 3
Tensile Test
[0047] Tensile tests were conducted on samples using an Instron
Model 3343. Samples were cut into 1 in wide strips with a paper
cutter. 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 samples were tested to failure with an appropriate
load cell. At least three strips from each sample were tested and
the values were averaged together.
Example 4
Vertical Wicking Speed Test
[0048] To determine the wicking speed for a sample, a 1'' wide
strip of the paper was prepared. The strip was clamped onto a
fixture such that it hung vertically. A 500 mL beaker was filled
with 100 mL of water and placed below the paper strip on a stage
that could be raised and lowered. The stage was raised such that 5
mm of the bottom of the paper strip was submerged in the water. The
strip was marked with pencil lines above the water level at 1 cm, 2
cm, 3 cm, 4 cm, 5 cm, and 6 cm. Wicking speed was determined by the
time taken by the water level to reach the different heights.
Example 5
Control Handsheets
[0049] Handsheets were produced with the method in Example 2 using
of the solution prepared in Example 1. The final paper weight was
approximately 19 g for the control sheets. The final basis weight
was about 670 gms.
Example 6
Handsheets with Debonders
[0050] Handsheets were produced with the method in Example 2 using
of the solution prepared in Example 1. A debonder selected from the
list in Table A and/or Table B was added at a concentration of up
to 10% of the final paper weight and mixed for 10 minutes into the
solution prepared in Example 1.
Example 7
Control over Precipitation of Polymers in Solution Using Chaotropic
Salt
[0051] By changing the concentration of salt in the solution, the
temperature at which cloudiness was observed in the polymer
solution could be lowered or increased (cloudiness indicating
polymer precipitation). Different concentration solutions of
hydrophilic debonders selected from the list in Table A and/or
Table B were made in water. To these solutions, salt solutions were
added to make 0.1M, 0.2M and 0.3M final salt concentration. The
salts were at least one of sodium chloride, potassium chloride, and
potassium sulfate. The polymer-salt solutions were heated to
different temperatures to observe the onset of precipitation of the
polymer by monitoring cloudy streaks of polymer precipitation from
solutions.
Example 8
Mechanical Strength and Wicking Tests
[0052] Tensile load at failure was measured for paper strips
treated with hydrophilic debonders and conventional debonders
(post-headbox treatment) by dipping 1'' by 6'' strips of 670 GSM
basis weight paper strips in 50 mL centrifuge tubes containing
solutions containing BASF Pluronic polymers in deionized water at
concentration of 1%/wt, until the strips were saturated for
approximately 2 minutes. The samples were then pressed and dried at
110.degree. C. for 45 minutes. The protocol of Example 3 was used
to determine the Energy and Max Load values. Corresponding wicking
speeds were measured using the protocol described in Example 4; the
wicking time corresponded with the time required for the water
level to reach 6 cm. For this experiment, samples were prepared
using polymers listed in Table 1 below, with an untreated sample as
the control. Table 1 and FIG. 1 show the maximum tensile load at
failure along with wicking time.
TABLE-US-00003 TABLE 1 Energy Polymer (lbf/in) Max Load/W (lbf/in)
Wicking Time (s) Ctrl 0.6496 48.35 .+-. 7.18 267 .+-. 24 L31 0.4933
19.48 .+-. 2.28 255 .+-. 17 L35 0.5177 29.81 .+-. 5.45 250 .+-. 28
L121 0.2685 23.49 .+-. 1.48 254 .+-. 18 L81 0.2819 22.35 .+-. 22.35
282 .+-. 16 L64 0.4060 25.90 .+-. 4.99 274 .+-. 27 F68 0.6238 25.02
.+-. 1.80 255 .+-. 13 F127 0.4135 25.77 .+-. 5.13 382 .+-. 17
[0053] FIG. 2A shows the comparison of pulp treated with
conventional debonder such as Prosoft TQ2028, with Pluronic L31
polymer, and untreated control pulp. The samples with debonder
utilized about 1 weight percent of the debonder. The graph of FIG.
2A shows that L31 reduces tensile strength without affecting the
wicking speed while the conventional debonder affects wicking speed
negatively.
[0054] FIG. 2B graphs the results of FIG. 2A in terms of wicking
time against the tensile strength. As the graph suggests, samples
corresponding to virgin fibers have a high tensile strength, which
indicate substantial fiber-fiber interactions. The use of
conventional debonders results in a desired lowering of tensile
strength at the expense of a higher wicking time. The tested new
debonders, in accord with some embodiments of the invention, lower
the tensile strength without resulting in a substantial increase in
wicking time.
Example 9
Concentration Dependence of Debonder
[0055] Samples were prepared by dipping 1'' by 6'' strips of 670
GSM basis weight paper strips in 50 mL centrifuge tubes containing
solutions containing BASF Pluronic polymer L31 in deionized water
at concentrations ranging from 0 to 10%/wt, until the strips were
saturated for approximately 2 minutes. The samples were then
pressed and dried at 110.degree. C. for 45 minutes. The tensile
load at failure was then measured using the apparatus described in
Example 3, and the wicking time was measured using the protocol of
Example 4; the wicking time corresponded with the time required for
the water level to reach 6 cm. Table 2, FIGS. 3A and 3B below show
the results of these tests.
TABLE-US-00004 TABLE 2 Energy Conc. (lbf/in) Max Load/W (lbf/in)
Wicking Time (s) 0 0.9144 73.09 .+-. 5.53 279 .+-. 3 0.01 0.6127
66.53 .+-. 11.16 250 .+-. 3 0.1 0.6183 54.38 .+-. 5.44 241 .+-. 7
0.5 0.4859 36.41 .+-. 8.16 242 .+-. 13 1 0.4142 35.21 .+-. 8.48 255
.+-. 7 1.2 0.3881 28.72 .+-. 5.37 251 .+-. 22 2 0.3211 29.96 .+-.
9.36 256 .+-. 1
Example 10
Synergistic Effect of Conventional and Hydrophilic Debonders
[0056] Samples were made by dipping untreated and
conventional-debonder-treated 1'' by 6'' strips of 670 GSM basis
weight paper in 50 mL centrifuge tubes containing solutions
containing a hydrophilic debonder. For the hydrophilic debonder,
the BASF Pluronic polymer L35 in deionized water was used at
concentration of 1%/wt. Sample strips remained in contact with this
solution for approximately 2 minutes, until the strips were
saturated. The samples were then pressed and dried at 110.degree.
C. for 45 minutes. For each strip, the tensile load at failure was
then measured, using the apparatus described in Example 3 and the
wicking time was measured using the protocol of Example 4; the
wicking time corresponded with the time required for the water
level to reach 6 cm. The results of these tests are shown in FIG.
4.
EQUIVALENTS
[0057] While specific embodiments of the subject invention have
been discussed, the above specification is illustrative and not
restrictive. Many variations of the invention will become apparent
to those skilled in the art upon review of this specification. The
features illustrated or described in connection with one embodiment
may be combined with features of other embodiments. Such
modifications and variations are intended to be included within the
scope of the present invention. Unless otherwise indicated, all
numbers expressing quantities of ingredients, reaction conditions,
and so forth used in the specification and 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 in this specification are approximations that
may vary depending upon the desired properties sought to be
obtained by the present invention. The words "a" and "an" are
equivalent to the phrase "one or more."
[0058] 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.
* * * * *