U.S. patent application number 12/975441 was filed with the patent office on 2011-06-30 for process for enhancing dry strength of paper by treatment with vinylamine-containing polymers and acrylamide-containing polymers.
Invention is credited to Clement L. Brungardt, Jonathan M. McKay, Richard J. Riehle.
Application Number | 20110155339 12/975441 |
Document ID | / |
Family ID | 44063302 |
Filed Date | 2011-06-30 |
United States Patent
Application |
20110155339 |
Kind Code |
A1 |
Brungardt; Clement L. ; et
al. |
June 30, 2011 |
Process for Enhancing Dry Strength of Paper by Treatment with
Vinylamine-Containing Polymers and Acrylamide-Containing
Polymers
Abstract
A process is disclosed for the production of paper with enhanced
dry strength comprising adding to the wet end of a paper machine,
(a) a vinylamine-containing aqueous solution polymer having a
molecular weight of from 75,000 daltons to 750,000 daltons and (b)
an amphoteric or cationic acrylamide-containing aqueous solution
polymer having a molecular weight of from 75,000 daltons to
1,500,000 daltons, wherein the sum of the anionic and cationic
monomers comprises at least 5% on a molar basis of the composition
of the acrylamide-containing polymer.
Inventors: |
Brungardt; Clement L.;
(Oxford, PA) ; McKay; Jonathan M.; (Wilmington,
DE) ; Riehle; Richard J.; (Wilmington, DE) |
Family ID: |
44063302 |
Appl. No.: |
12/975441 |
Filed: |
December 22, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61290670 |
Dec 29, 2009 |
|
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Current U.S.
Class: |
162/164.6 |
Current CPC
Class: |
D21H 17/56 20130101;
D21H 17/37 20130101; D21H 17/35 20130101; D21H 17/375 20130101;
D21H 21/18 20130101 |
Class at
Publication: |
162/164.6 |
International
Class: |
D21H 13/26 20060101
D21H013/26 |
Claims
1. A process for the production of paper, board, and cardboard with
enhanced dry strength comprising adding to the wet end of a paper
machine (a) a vinylamine-containing aqueous solution polymer having
a molecular weight of from 75,000 daltons to 750,000 daltons and
(b) an amphoteric or cationic acrylamide-containing aqueous
solution polymer having a molecular weight of from 75,000 daltons
to 1,500,000 daltons, wherein the sum of the anionic and cationic
monomers comprises at least 5% on a molar basis of the composition
of the acrylamide-containing monomer.
2. The process according to claim 1 wherein the active polymer
content of the vinylamine containing aqueous solution polymer is
from 5% to 30% on a dry weight basis and wherein the
vinylamine-containing polymer has an N-vinylformamide content of at
least 50% on a molar basis of the total monomer charged prior to
hydrolysis, and at least 10% of the N-vinylformamide has been
hydrolyzed in the final polymer.
3. The process according to claim 1 wherein the
vinylamine-containing polymer has a molecular weight of from
150,000 daltons to 500,000 daltons.
4. The process according to claim 1 wherein the
acrylamide-containing aqueous solution polymer contains a sum
cationic and/or amphoteric monomer charge of from 5% to 50% on a
molar basis, and has an active polymer content of from 5% to 50% on
a weight basis.
5. The process according to claim 1 wherein the
acrylamide-containing aqueous solution polymer is cationic and has
a molecular weight of from 75,000 daltons to 750,000 daltons.
6. The process according to claim 1 wherein the
acrylamide-containing aqueous solution polymer is an aqueous
dispersion polymer.
7. The process according to claim 6 wherein the
acrylamide-containing aqueous solution polymer is an aqueous
dispersion polymer having a molecular weight of from 300,000
daltons to 1,500,000 daltons.
8. The process according to claim 6 wherein the
acrylamide-containing aqueous solution polymer is an aqueous
dispersion polymer having a molecular weight of from 400,000
daltons to less than 1,250,000 daltons.
9. The process according to claim 1, wherein the
acrylamide-containing aqueous solution polymer contains a cationic
monomer charge of from 5% to 50% on a molar basis, has an active
polymer content of from 5% to 50% on a weight basis, and comprises
a least one cationic monomer selected from the group consisting of:
diallyldimethylammonium chloride (DADMAC), 2-(dimethylamino)ethyl
acrylate, 2-(dimethylamino)ethyl methacrylate,
2-(diethylaminoethyl) acrylate, 2-(diethylamino)ethyl methacrylate,
3-(dimethylamino)propyl acrylate, 3-(dimethylamino)propyl
methacrylate, 3-(diethylamino)propyl acrylate,
3-(diethylamino)propyl methacrylate,
N-[3-(dimethylamino)propyl]acrylamide,
N-[3-(dimethylamino)propyl]methacrylamide,
N-[3-(diethylamino)propyl]acrylamide,
N-[3-(diethylamino)propyl]methacrylamide,
[2-(acryloyloxy)ethyl]trimethylammonium chloride,
[2-(methacryloyloxy)ethyl]trimethylammonium chloride,
[3-(acryloyloxy)propyl]trimethylammonium chloride,
[3-(methacryloyloxy)propyl]trimethylammonium chloride,
3-(acrylamidopropyl)trimethylammonium chloride, and
3-(methacrylamidopropyl)trimethylammonium chloride.
10. The process according to claim 4, wherein the
acrylamide-containing aqueous solution polymer has an overall
amphoteric charge.
11. The process according to claim 10 wherein the
acrylamide-containing aqueous solution polymer is amphoteric and
has a molecular weight of from 75,000 daltons to 750,000
daltons.
12. The process according to claim 10, wherein the amphoteric
acrylamide-containing aqueous solution is comprised of a
polyelectrolyte complex consisting of an acrylamide-containing
aqueous solution polymer and a cofactor carrying a complementary
charge.
13. The process according to claim 12, wherein the amphoteric
acrylamide-containing aqueous solution is comprised of a
polyelectrolyte complex having a molecular weight of from 100,000
daltons to less than 1,000,000 daltons.
14. The process according to claim 1, wherein the
vinylamine-containing polymer and the acrylamide-containing polymer
are added to the papermachine as a single product blend.
15. The process according to claim 14, wherein the cationic portion
of the acrylamide-containing polymer is generated by at least one
monomer selected from the group consisting of
diallyldimethylammonium chloride (DADMAC),
N-[3-(dimethylamino)propyl]acrylamide,
N-[3-(dimethylamino)propyl]methacrylamide,
N-[3-(diethylamino)propyl]acrylamide,
N-[3-(diethylamino)propyl]methacrylamide,
3-(acrylamidopropyl)trimethylammonium chloride, and
3-(methacrylamidopropyl)trimethylammonium chloride.
16. The process according to claim 15, wherein the cationic portion
of the acrylamide-containing polymer is generated by at least one
monomer selected from the group consisting of
diallyldimethylammonium chloride (DADMAC),
N-[3-(dimethylamino)propyl]acrylamide,
N-[3-(dimethylamino)propyl]methacrylamide,
3-(acrylamidopropyl)trimethylammonium chloride, and
3-(methacrylamidopropyl)trimethylammonium chloride.
17. The process according to claim 1, wherein the
vinylamine-containing polymer and the acrylamide-containing polymer
are added to the wet end of a paper machine in a ratio of
vinylamine-containing polymer to acrylamide-containing polymer of
from 10:1 to 1:50 up to a sum total of 1.25% on a weight basis of
the dry pulp, based on the active polymer solids of the polymeric
products.
18. A paper product produced by the process of claim 1.
Description
[0001] This Application claims priority of U.S. Provisional
Application No. 61/290,670, filed Dec. 29, 2009, the entire
contents of which are herein incorporated by reference.
FIELD OF THE INVENTION
[0002] This invention relates to enhanced dry strength in paper
using a process of treating a pulp slurry with a combination of a
vinylamine-containing polymer and a cationic or amphoteric
acrylamide-containing polymer.
BACKGROUND OF THE INVENTION
[0003] The papermaking industry is constantly seeking new synthetic
additives to improve the dry strength of paper products. Improved
dry strength can give a higher performance product, but also may
allow the papermaker to use less cellulosic fiber to achieve a
particular performance target. Furthermore, the increased usage of
recycled fiber results in a weaker sheet, forcing the papermaker to
either increase basis weight of the sheet or employ synthetic
strength additives. The options that are known have various
economic and technical limitations. For instance, according to U.S.
Pat. No. 6,939,443, the use of combinations of
polyamide-epichlorohydrin (PAE) resins with anionic polyacrylamide
additives with specific charge densities and molecular weights can
enhance the dry strength of a paper product. However, these
combinations also may elevate the wet strength of the resultant
paper to the point that repulping broke paper is extremely
difficult and inefficient.
[0004] Polymers of acrylamide or copolymers incorporating
acrylamide and a monomer such as diallyldimethylammonium chloride,
when treated with a dialdehyde compound such as glyoxal, are widely
known to result in resins that can also enhance the dry strength of
paper significantly, yet have very limited permanent wet strength
properties, allowing the papermaker to easily repulp broke paper.
However, these resins also have their limitations. These additives
either have a very short shelf-life due to viscosity instability,
or are shipped at very low active solids content. Furthermore, when
added in the larger amounts, the performance of such
dialdehyde-modified acrylamide-containing polymers tends to reach a
plateau, making a high-performance product difficult to
manufacture.
[0005] Polyvinylamine resins have become popular in the papermaking
industry not only because they endow a sheet with increased dry
strength, but also because of their easy handling and application
as well as the increased retention and drainage they afford the
paper machine. However, when added in ever increasing amounts, they
have the negative effect of overflocculating the sheet because of
the heavy cationic charge these resins carry. Overflocculation
results in a poorly formed, weaker finished product.
[0006] Other inventions have sought to augment the positive effects
of polyvinylamine. According to U.S. Pat. No. 6,824,650 and
European Patent No. 1,579,071, the combination of polyvinylamine
with glyoxalated polyacrylamide resins in a pulp slurry results in
enhanced product dry strength. However, the aforementioned
drawbacks of glyoxalated polyacrylamides, namely low active solids
of the product and limited viscosity stability of the product, are
clearly in play.
[0007] U.S. Pat. No. 6,132,558 discloses a papermaking system
wherein a pulp slurry is treated first with a highly cationic
polymer, including vinylamine-containing polymers, of molar mass of
5,000 to 3,000,000 daltons, and subsequently with a second cationic
acrylamide-containing polymer of molar mass of more than 4,000,000
daltons, subjected to a shearing stage, then treated with a finely
divided inorganic flocculating agent, such as bentonite, colloidal
silica, or clay.
[0008] US Patent Publication 2008/0000601 discloses a process of
papermaking where the pulp slurry is treated with a polymer,
including vinylamine-containing polymers, of molar mass of more
than 1,000,000 daltons, as well as a second polymer, including
cationic acrylamide-containing polymers, with a molar mass of more
than 2,500,000 daltons, all in the absence of finely divided
inorganic flocculating agents.
[0009] U.S. Pat. No. 6,746,542 discloses a method of papermaking
wherein a pulp slurry is treated with starch that has been modified
at a temperature above the starch gelatinzation temperature with a
highly cationic polymer, including vinylamine-containing polymers,
of molar mass of less than 1,000,000 daltons. The pulp slurry is
subsequently treated with a second polymer, including cationic
acrylamide-containing polymers, with a molar mass of more than
1,000,000 daltons.
[0010] US Patent Publication 2008/0196852 discloses a retention aid
system for papermaking which comprises at least one polymer,
including vinylamine-containing polymers, at least one linear,
anionic polymer of molar mass of more than 1,000,000 daltons, and
at least one particulate, anionic, crosslinked, organic
polymer.
[0011] Combining vinylamine-containing polymers with
acrylamide-containing polymers may be both the simplest and most
effective means for producing a high performance paper product
while maintaining paper machine productivity and repulping broke
paper. However, examples from the prior art that may include these
polymers have significant drawbacks. For instance, previous
examples may require special metering apparatuses, additional steps
for treating starch prior to addition to the pulp slurry, or high
molar mass polymers that may result in overflocculation of the pulp
slurry when added in sufficient amounts to affect dry strength.
BRIEF DESCRIPTION OF THE INVENTION
[0012] Treatment of a pulp slurry with a vinylamine-containing
aqueous solution polymer in combination with a cationic or
amphoteric acrylamide-containing aqueous solution polymers result
in paper with enhanced dry strength.
[0013] This combination is most effective when the active polymer
solids content of the acrylamide-containing aqueous solution
polymer ranges from 5% to 50% by weight, and the content of the sum
of the cationic and anionic monomers in the acrylamide-containing
polymer ranges from 5% to 50% on a molar basis of the total monomer
content, and the molecular weight of the acrylamide-containing
polymer ranges from 75,000 daltons to 1,500,000 daltons.
[0014] The vinylamine-containing polymer is most effective when it
contains at least 50% on a molar basis of N-vinylformamide monomer,
at least 10% of which has been hydrolyzed in the final product and
has a molecular weight in the range of from 75,000 daltons to
750,000 daltons. The aqueous solution containing the
vinylamine-containing polymer has a total polymer solids content of
from 5% to 30% by weight.
[0015] One embodiment of the invention is a process for the
production of paper, board, and cardboard with enhanced dry
strength comprising adding to the wet end of a paper machine (a) a
vinylamine-containing aqueous solution polymer having a molecular
weight of from 75,000 daltons to 750,000 daltons and (b) an
amphoteric or cationic acrylamide-containing aqueous solution
polymer having a molecular weight of from 75,000 daltons to
1,500,000 daltons, where the sum of the anionic and cationic
monomers comprise at least 5% on a molar basis of the composition
of the acrylamide-containing monomer.
[0016] In one embodiment of the process the vinylamine-containing
polymer has an N-vinylformamide content of at least 50% on a molar
basis of the total monomer charged, at least 10% of which has been
hydrolyzed in the final polymer, and an active polymer content of
from 5% to 30% on a weight basis.
[0017] In one embodiment of the process the acrylamide-containing
aqueous solution polymer contains a sum cationic and/or amphoteric
monomer charge of from 5% to 50% on a molar basis, and has an
active polymer content of from 5% to 50% on a weight basis.
[0018] In one embodiment of the process the acrylamide-containing
aqueous solution polymer is of an aqueous dispersion polymer.
[0019] In one embodiment of the process the acrylamide-containing
aqueous solution polymer contains a cationic monomer charge of from
5% to 50% on a molar basis, has an active polymer content of from
5% to 50% on a weight basis, and comprises a least one cationic
monomer selected from the group consisting of
diallyldimethylammonium chloride (DADMAC), 2-(dimethylamino)ethyl
acrylate, 2-(dimethylamino)ethyl methacrylate,
2-(diethylaminoethyl) acrylate, 2-(diethylamino)ethyl methacrylate,
3-(dimethylamino)propyl acrylate, 3-(dimethylamino)propyl
methacrylate, 3-(diethylamino)propyl acrylate,
3-(diethylamino)propyl methacrylate,
N-[3-(dimethylamino)propyl]acrylamide,
N-[3-(dimethylamino)propyl]methacrylamide,
N-[3-(diethylamino)propyl]acrylamide,
N-[3-(diethylamino)propyl]methacrylamide,
[2-(acryloyloxy)ethyl]trimethylammonium chloride,
[2-(methacryloyloxy)ethyl]trimethylammonium chloride,
[3-(acryloyloxy)propyl]trimethylammonium chloride,
[3-(methacryloyloxy)propyl]trimethylammonium chloride,
3-(acrylamidopropyl)trimethylammonium chloride, and
3-(methacrylamidopropyl)trimethylammonium chloride.
[0020] In one embodiment of the process the acrylamide-containing
aqueous solution polymer has an overall amphoteric charge.
[0021] In one embodiment of the process the amphoteric
acrylamide-containing aqueous solution is comprised of a
polyelectrolyte complex consisting of an acrylamide-containing
aqueous solution polymer and a cofactor carrying an opposing
charge.
[0022] In one embodiment of the process the vinylamine-containing
polymer and the acrylamide-containing polymer are a single product
blend and the cationic portion of the amphoteric
acrylamide-containing polymer is generated by at least one monomer
selected from the group consisting of diallyldimethylammonium
chloride (DADMAC), N-[3-(dimethylamino)propyl]acrylamide,
N-[3-(dimethylamino)propyl]methacrylamide,
N-[3-(diethylamino)propyl]acrylamide,
N-[3-(diethylamino)propyl]methacrylamide,
3-(acrylamidopropyl)trimethylammonium chloride, and
3-(methacrylamidopropyl)trimethylammonium chloride.
[0023] In one embodiment of the process the vinylamine-containing
polymer and the acrylamide-containing polymer are added to the wet
end of a paper machine in a ratio of vinylamine-containing polymer
to acrylamide-containing polymer of from 10:1 to 1:50 up to a sum
total of 1.25% on a weight basis of the dry pulp, based on the
active polymer solids of the polymeric products.
[0024] One embodiment of the invention is the paper product
produced by the process of adding to the wet end of a paper machine
(a) a vinylamine-containing aqueous solution polymer having a
molecular weight of from 75,000 daltons to 750,000 daltons and (b)
an amphoteric or cationic acrylamide-containing aqueous solution
polymer having a molecular weight of from 75,000 daltons to
1,500,000 daltons, where the sum of the anionic and cationic
monomers comprise at least 5% on a molar basis of the composition
of the acrylamide-containing monomer.
[0025] In another embodiment, the invention relates to the method
of treating a cellulosic pulp slurry in the wet end of a paper
machine with (a) a vinylamine-containing polymer and (b) a cationic
or amphoteric acrylamide-containing aqueous solution polymer. It is
preferred that the vinylamine-containing polymer is added to the
pulp slurry first, followed by the acrylamide-containing
polymer.
DETAILED DESCRIPTION OF THE INVENTION
[0026] As used herein, the singular terms "a" and "the" are
synonymous and used interchangeably with "one or more" or "at least
one" unless the context clearly indicates a contrary meaning.
Accordingly, for example, reference to "a compound" herein or in
the appended claims can refer to a single compound or more than one
compound.
[0027] As used herein and unless otherwise stated, the terms
"vinylamine-containing polymers," is understood to mean
homopolymers of vinylamine (e.g., polyvinylamine or fully
hydrolyzed polyvinylformamide), copolymers of vinylamine with other
comonomers, partially hydrolyzed polyvinylformamide, partially
hydrolyzed vinylformamide copolymers, vinylamine terpolymers,
vinylamine homo- and copolymers manufactured by the Hofmann
modification of acrylamide polymers, or vinylamine containing
polymers that are chemically modified after polymerization.
Examples may include those described in US Patent Publication
number 2009/0043051 or number 2008/0196851.
[0028] As used herein and unless otherwise stated, the term
"acrylamide-containing polymer" refers to the cationic or
amphoteric acrylamide-containing aqueous solution polymer.
[0029] As used herein and unless otherwise stated, the term
"aqueous solution polymer" refers to a polymer that forms a fully
homogenous solution in water when diluted to 1% on a dry solids
basis, in the absence of any cosolvent. For instance, an aqueous
solution polymer does not include oil-in-water or water-in-oil
emulsions. Examples of aqueous solution polymers may include
aqueous dispersion polymers, such as are described in U.S. Pat.
Nos. 5,541,252 and 7,323,510 as well as US Patent Publications
number 2002/198317 and number 2008/0033094.
[0030] The invention is based in the discovery that the performance
of a paper machine and the paper products derived thereby can be
greatly enhanced by the treatment of the pulp slurry with a
vinylamine-containing polymer in combination with an
acrylamide-containing polymer with particular molecular weight and
charge attributes as described below. Use of a
vinylamine-containing polymer alone provides both strength and
drainage performance in the papermaking system; however, when added
in ever-increasing amounts, the performance of the paper product
first levels off, and then deteriorates, largely due to
overflocculation of the forming paper web. It has unexpectedly been
found that the addition of vinylamine-containing polymer in
conjunction with the addition of aqueous solution
acrylamide-containing polymers having substantial amphoteric or
cationic charge results in a product with strength performance
beyond that which can be attained by using vinylamine-containing or
acrylamide-containing polymers alone; moreover, the excellent
drainage performance achieved by using a vinylamine-containing
polymer can be substantially maintained using such a combination of
polymers.
[0031] The vinylamine-containing polymer is most effective when its
molecular weight is from 75,000 daltons to 750,000 daltons, more
preferably of from 100,000 daltons to 600,000 daltons, most
preferably of from 150,000 daltons to 500,000 daltons. The
molecular weight can be from 150,000 daltons to 400,000 daltons.
Below the molecular weight threshold of 75,000 daltons, little to
no strength performance is observed, and substantial drainage
performance enhancement is not observed. The vinylamine-containing
polymer is not cooked with starch prior to addition to the pulp
slurry. A vinylamine-containing polymer above the molecular weight
of 750,000 daltons will generally negatively affect formation at
dosages required for dry strength enhancement because of the
tendency to overflocculate the sheet, resulting in lower strength.
An aqueous solution vinylamine-containing polymer above 750,000
daltons either is typically made at such high viscosities as to
render product handling extremely difficult, or alternatively is
made in such low product polymer solids as to render the product
not cost effective to store and ship.
[0032] The active polymer solids percentage of the
vinylamine-containing polymer ranges of from 5% to 30%, more
preferably from 8% to 20% by weight of the total
vinylamine-containing polymer product content. Below 5% active
polymer solids, higher molecular weight aqueous solution polymers
may be possible, but the product becomes ineffective with respect
when shipping and transportation costs are accounted for. On the
other hand, as the active polymer solids rises, the molecular
weight of the polymer must decrease overall so that the aqueous
solution is still easily pumpable. Thus, a practical relationship
can be drawn between the total polymer solids of the
vinylamine-containing polymer product and the molecular weight of
such a polymer, and a correlation can be drawn between these
parameters and polymer performance.
[0033] The performance of the vinylamine-containing polymer is
influenced by the amount of primary amine present in the product.
The vinylamine moiety is typically generated by acidic or basic
hydrolysis of N-vinylacylamide groups, such as N-vinylformamide,
N-vinylacetamide, or N-vinyl propionamide, most preferably
N-vinylformamide. The vinylamine-containing polymer is most
effective in enhancing the dry strength of a paper product and/or
the drainage performance of a papermaking system when the amount of
N-vinylformamide is at least 50% on a molar basis of the hydrolyzed
polymer. After hydrolysis, at least 10% of the N-vinylformamide
originally incorporated into the resultant polymer should be
hydrolyzed. Without wishing to be bound by theory, the hydrolyzed
N-vinylformamide group may exist in various structures in the final
polymer product such as primary or substituted amine, amidine,
guanidine, or amide structures, either in open chain or cyclical
forms after hydrolysis.
[0034] The acrylamide-containing polymer is most effective when it
contains a substantial amount of a positively charged comonomer(s).
Without wishing to be bound by theory, the positively charged
monomer allows the acrylamide-containing polymer to adhere to the
cellulose fibers due to a charge-charge interaction with negatively
charged substances in the pulp slurry, including, but not limited
to: pulp fibers, hemicellulose, oxidized starch commonly found in
recycled cellulose furnish, anionic strength aids such as
carboxymethylcellulose, and anionic trash. The incorporation of
cationic groups into the acrylamide-containing polymer is generally
not detrimental to the drainage performance of the papermaking
system. Without wishing to be bound by theory, the hydrogen-bonding
components of the acrylamide-containing polymer, such as amide
groups, are effective in enhancing the dry strength of the paper
product.
[0035] Suitable comonomers used to impart cationic charge to the
polymer include, but are not limited to, diallyldimethylammonium
chloride (DADMAC), 2-(dimethylamino)ethyl acrylate,
2-(dimethylamino)ethyl methacrylate, 2-(diethylaminoethyl)
acrylate, 2-(diethylamino)ethyl methacrylate,
3-(dimethylamino)propyl acrylate, 3-(dimethylamino)propyl
methacrylate, 3-(diethylamino)propyl acrylate,
3-(diethylamino)propyl methacrylate,
N-[3-(dimethylamino)propyl]acrylamide,
N-[3-(dimethylamino)propyl]methacrylamide,
N-[3-(diethylamino)propyl]acrylamide,
N-[3-(diethylamino)propyl]methacrylamide,
[2-(acryloyloxy)ethyl]trimethylammonium chloride,
[2-(methacryloyloxy)ethyl]trimethylammonium chloride,
[3-(acryloyloxy)propyl]trimethylammonium chloride,
[3-(methacryloyloxy)propyl]trimethylammonium chloride,
3-(acrylamidopropyl)trimethylammonium chloride, and
3-(methacrylamidopropyl)trimethylammonium chloride. Such cationic
monomers can affect the performance of the cationic or amphoteric
polymer when incorporated into the polymer backbone.
[0036] The amount of cationic monomer incorporated into a polymer
may be from 5% to 50% on a molar basis of all the monomers
incorporated into the acrylamide-containing polymer in the case of
a cationic polymer. In the case of an amphoteric polymer, the
amount of the cationic monomer plus the amount of an anionic
monomer described below may be from 5% to 50%, more preferably from
15% to 40%, on a molar basis of all the monomers incorporated into
the acrylamide-containing polymer. The acrylamide-containing
polymer may be cross-linked with an agent such as methylene
bisacrylamide (MBA) provided the molecular weight and charge
guidelines are met as described herein.
[0037] The incorporation of an anionic comonomer into the
acrylamide-containing polymer along with the cationic comonomer,
forming an amphoteric acrylamide-containing polymer, is also
effective in enhancing the dry strength of a paper product made
thereby. Without wishing to be bound by theory, the anionic
comonomer allows the amphoteric polymer to form a coacervate
complex with a wide variety of substances found in a recycled pulp
slurry, including, but not limited to: a vinylamine-containing
polymer, a cationically charged flocculant or coagulant, cationic
or amphoteric starch, polyamidoamine-epichlorohydrin wet strength
aids, or another amphoteric acrylamide-containing polymer.
Moreover, the combination of cationic and anionic monomers in the
acrylamide-containing polymer either enhances or does not
negatively affect the drainage performance of a papermaking system
when compared to an acrylamide-containing polymer using only an
anionic comonomer. Suitable anionic comonomers include, but are not
limited to, acrylic acid, methacrylic acid, itaconic acid, itaconic
anhydride, maleic anhydride, maleic acid, styrene sulfonate, vinyl
sulfonate, 2-acrylamido-2-methylpropane sulfonate (AMPS).
Alternatively, such substructures may be generated by hydrolysis of
a precursor structure (e.g. generation of methacrylic acid in the
polymer backbone via hydrolysis of methyl methacrylate after the
formal polymerization). The amount of charged monomer incorporated
into the acrylamide-containing polymer may affect the performance
of the polymer. Such anionic monomers may be used in an amphoteric
acrylamide-containing polymer, and the amount of the anionic
monomer plus the amount of a cationic monomer described above may
be from 5% to 50% on a molar basis of all the monomers incorporated
into the acrylamide-containing polymer. The acrylamide-containing
polymer may be cross-linked with an agent such as methylene
bisacrylamide (MBA) provided the molecular weight and charge
guidelines are met as described herein.
[0038] The properties of an amphoteric aqueous solution
acrylamide-containing polymer as defined above can also be
effectively produced by the use of an acrylamide-containing
polyelectrolyte complex. When combined with a vinylamine-containing
polymer, such an acrylamide-containing polyelectrolyte complex may
also produce benefits similar to those described above when
vinylamine-containing polymers are combined with cationic or
amphoteric acrylamide-containing polymers. Although polyelectrolyte
complexes in various forms have been disclosed, such as in European
Patent Publication No. 1,918,455 A1, herein we disclose the
unexpected result that the effectiveness of such polyelectrolyte
complexes in generating dry strength beyond what the
polyelectrolyte complex may provide on its own, may be achieved
when they are used in combination with vinylamine-containing
polymers. An acrylamide-containing polyelectrolyte complex contains
an acrylamide-containing polymer of either cationic, amphoteric, or
anionic charge, as well as a second polymer of a complementary
charge. For example, an anionic acrylamide-containing polymer made
by polymerization of acrylamide with one of the suitable anionic
monomers listed above can form a polyelectrolyte complex with a
cationic polymer, which may or may not include acrylamide. Such
cationic polymers include, but are not limited to,
alkylamine-epichlorohydrin polymers, cationic acrylamide-containing
polymers as described above, polyamidoamine-epichlorohydrin
polymers, and polyethyleneimine polymers. The acrylamide-containing
polyelectrolyte complex may also comprise a cationic
acrylamide-containing polymer and an anionic polymer. Such anionic
polymers include, but are not limited to, polymers and copolymers
of (meth)acrylic acid, polymers and copolymers of maleic acid, and
carboxymethyl cellulose. The acrylamide-containing polyelectrolyte
complex may be added to the papermaking slurry either as a single
blended product or as two separate products, most preferably as a
single blended product. The amphoteric polyelectrolyte complex
carries a net charge, expressed in milliequivalents per gram
(meq/g) of polymer active content. The amphoteric polyelectrolyte
complex is generally most stable and useful in combination with
vinylamine-containing polymers when the net charge is in the range
of from -2 meq/g to +2 meq/g, more preferably of from -1 meq/g to
+1 meq/g. The particle size is also an important parameter of the
amphoteric polyelectrolyte complex. The complex is most useful when
the particle size ranges of from 0.1 microns to 50 microns, more
preferably from 0.2 to 5 microns. Other guidelines for active
polymer solids, the preferred methods for adding the
acrylamide-containing polymer to the pulp slurry, and the ratio of
the vinylamine-containing polymer to the acrylamide-containing
polymer apply to the total formulation of the acrylamide-containing
polyelectrolyte complex, not only the acrylamide-containing polymer
portion of the complex.
[0039] The acrylamide-containing aqueous solution polymer, whether
it is characteristically a cationic polymer, amphoteric polymer, or
amphoteric polyelectrolyte complex as defined above, most
effectively enhances the dry strength of a paper product when its
molecular weight is greater than 75,000 daltons. A molecular weight
less than 75,000 daltons is not easily retained in the sheet, and
above all does not endow paper with significant dry strength
properties, although it could be manufactured in such a way is to
have a polymer solids content above 50% on a weight basis. However,
an acrylamide-containing polymer of greater than 1,500,000 daltons,
and especially greater than 2,500,000 daltons may show significant
drawbacks. Although at lower dosages, such high molar mass polymers
may give good drainage performance, attaining high dry strength
typically requires higher dosages of polymers. Such a polymer can
significantly overflocculate the sheet when added at a dosage that
might significantly impact dry strength, thereby resulting in poor
formation and/or poor dry strength. In one embodiment, the
molecular weights of the cationic or amphoteric
acrylamide-containing aqueous solution polymers can be in the range
of from 75,000 to less than 1,500,000 daltons, or can be from
100,000 to less than 1,250,000 daltons, or can be from 100,000 to
less than 1,000,000 daltons. Moreover, a polymer of this molecular
weight is generally synthesized via emulsion or reverse emulsion
polymerization, thereby adding significant cost, inconvenience, and
environmental and safety risk. For instance, oil or other
hydrocarbon, such as mineral oil, is required in the formulation of
a reverse emulsion product which adds significant cost to the
product but does not by itself add value to the product;
significant additional make-down equipment used to store, agitate,
dilute, and invert the emulsions; additional chemicals are needed
to break or invert the emulsion; and emulsion- or reverse
emulsion-type polymers also contain significant amounts of volatile
organic compounds, creating a significant health and/or safety
hazard. An aqueous solution acrylamide-containing polymer of
molecular weight greater than 1,500,000 daltons may in theory be
achieved in a product; however, such a product would likely be less
than 5% polymer solids, rendering such a product less useful, cost
effective, and convenient to a papermaker, or would be made be of
such a high viscosity that the product handling would be extremely
difficult. Thus, a practical relationship between the total polymer
solids and molecular weight generally exists and a general
correlation can be drawn between these parameters and polymer
performance.
[0040] In one embodiment, the acrylamide-containing polymer is an
aqueous dispersion polymer. Acrylamide-containing polymers made by
way of aqueous dispersion polymerization of either a cationic or
amphoteric nature are of special practical importance when combined
with vinylamine-containing polymers. Specific examples are
described in U.S. Pat. No. 7,323,510 as well as US Patent
Publication No. 2008/0033094. These aqueous solution polymers may
have molecular weights of from 300,000 daltons to 1,500,000
daltons, or from 400,000 daltons to less than 1,250,000 daltons,
while maintaining polymer solids content of from 10% to 50% on a
weight basis. These polymers are of a molecular weight that is
somewhat less than traditional flocculants, and are thus less
effective than higher molecular weight acrylamide-containing
polymers as retention and drainage polymers at low dosage levels,
but may generate excellent drainage performance when used at dosage
levels adequate for dry strength enhancement without
overflocculating a forming cellulosic sheet. Without wishing to be
bound by theory, the interaction of vinylamine-containing polymers
either with aqueous dispersion acrylamide-containing polymers or
with other components of a papermaking system including but not
limited to oxidized starch, hemicellulose, or anionic trash, may
create especially extensive hydrogen-bonding networks, providing
additional dry strength to a paper product without any substantial
negative effects on the drainage performance of the papermaking
system.
[0041] The vinylamine-containing polymer and the
acrylamide-containing polymer may be combined together in a
single-product blend. Ratios of the vinylamine-containing polymer
to the acrylamide containing polymer range of from 10:1 to 1:50,
more preferably in the range of from 5:1 to 1:10, more preferably
in the range of from 3:1 to 1:5, most preferably in the range of
from 2:1 to 1:4.
[0042] Total amounts of the polymer blend may be added to the pulp
slurry in the wet end of the paper machine in amounts of from 0.05%
to 1.25% of the weight of dry pulp on a total polymer solids basis.
Blends can be made with vinylamine containing polymers and either
cationic or amphoteric acrylamide-containing polymers, but most
preferably with cationic acrylamide-containing polymers. Without
wishing to be bound by theory, anionic components of amphoteric
acrylamide-containing polymers may interact in an ionic fashion
with cationic components of vinylamine-containing polymers,
particularly primary amine groups, to form gels and high viscosity
products that are not useful for papermaking. Without wishing to be
bound by theory, polymers containing cationic monomers with ester
groups, for example, 2-[(acryloyloxy)ethyl]trimethylammonium
chloride, can react in aqueous solutions with primary amine groups
in the vinylamine-containing polymer to form amide groups, or can
hydrolyze to generate the above-mentioned anionic moieties, either
of which may form a gelled or prohibitively high viscosity product
which is not useful in papermaking. Moreover, the hydrolysis of the
relatively expensive cationic acrylate group represents a
significant financial loss when considering the cationic
acrylamide-containing polymer. Without wishing to be bound by
theory, amide-containing cationic monomers, such as
3-(acrylamidopropyl)trimethylammonium chloride or
diallyldimethylammonium chloride (DADMAC) are resistant both to
hydrolysis in aqueous solutions as well as reaction with primary
amine groups, making them preferred as cationic monomers in the
acrylamide-containing polymer to be blended with the
vinylamine-containing polymer.
[0043] Vinylamine-containing polymers and acrylamide-containing
polymers can be added during the papermaking process in the wet end
either in the thick stock, or in the thick stock; either before or
after a shear point. The acrylamide-containing polymer may be added
first in the wet end of the paper machine, followed by the
vinylamine-containing polymer; the acrylamide-containing polymer
may be added at the same point separately in the wet end of the
paper machine as the vinylamine-containing polymer; the
acrylamide-containing polymer may be added at the same point in the
wet end of a paper machine as a single product blend; or, more
preferably, the vinylamine-containing polymer may be added first in
the wet end of the paper machine, followed by the
acrylamide-containing polymer. The vinylamine-containing polymer is
not reacted with starch prior to addition to the pulp slurry.
[0044] The vinylamine-containing polymer and the
acrylamide-containing polymer may be added to the wet end of a
paper machine in a ratio of from 1:50 to 10:1 of
vinylamine-containing polymer to acrylamide-containing polymer as a
ratio of polymer solids; more preferably in a ratio of from 1:10 to
5:1, more preferably in the range of from 1:5 to 3:1, most
preferably in the range of from 1:5 to 2:1. Total amounts of the
polymer blend may be added to the pulp slurry in the wet end of the
paper machine in amounts of 0.05% to 1.25% of the weight of dry
pulp on a total polymer solids basis.
[0045] In another embodiment, this invention can be applied to any
of the various grades of paper that benefit from enhanced dry
strength including but not limited to linerboard, bag, boxboard,
copy paper, container board, corrugating medium, file folder,
newsprint, paper board, packaging board, printing and writing,
tissue, towel, and publication. These paper grades can be comprised
of any typical pulp fibers including groundwood, bleached or
unbleached Kraft, sulfate, semi-mechanical, mechanical,
semi-chemical, and recycled. They may or may not include inorganic
fillers.
[0046] The embodiments of the invention are defined in the
following Examples. It should be understood that these Examples are
given by way of illustration only. Thus various modifications of
the present invention in addition to those shown and described
herein will be apparent to those skilled in the art from the
foregoing description. Although the invention has been described
with reference to particular means, materials and embodiments, it
is to be understood that the invention is not limited to the
particulars disclosed, and extends to all equivalents within the
scope of the appended claims.
EXAMPLES
[0047] Polyvinylamine is abbreviated as PVAm. Size exclusion
chromatography (SEC) was used to measure molecular weight. The
analysis was accomplished using gel permeation columns (CATSEC
4000+1000+300+100) and Waters 515 series chromatographic equipment
with a mixture of 1% NaNO.sub.3/0.1% Trifluoroacetic acid in 50:50
H.sub.2O:CH.sub.3CN as the mobile phase. The flow rate was 1.0
mL/min. The detector was a Hewlett Packard 1047A differential
refractometer. Column temperature was set at 40.degree. C. and the
detector temperature was at 35.degree. C. The number average
(M.sub.n) and weight average molecular weight (M.sub.w) of the
polymers were calculated relative to the commercially available
narrow molecular weight standard poly(2-vinyl pyridine).
[0048] The net charges or charge densities (Mutek) of the ionized
polymers in the present invention were measured at pH 7.0 using a
colloid titration method. Charge density (meq/g) is the amount of
net charge per unit weight, in milliequivalents per gram of active
polymer. The polymer sample is titrated with a titrant of opposing
charge. For net cationic polymers, the titrant used is potassium
polyvinyl sulfate (PVSK), and for net anionic polymers the titrant
used is polydimethyldiallylammonium chloride (DADMAC). The titrant
is added until a 0 mV potential is achieved using an autotitrator
(Brinkmann Titrino) at a fixed titration rate (0.1 mL/dose, 5 sec)
and a Mutek particle charge detector (Model PCD 03, BTG, Mutek
Analytic Inc., 2141 Kingston Ct., Marietta, Ga., USA) signifying
end point detection.
[0049] Linerboard paper was made using a papermaking machine. The
paper pulp was a 100% recycled medium with 50 ppm hardness, 25 ppm
alkalinity, 2.5% GPC D15F oxidized starch (Grain Processing Corp.,
Muscatine, Iowa) and 2000 uS/cm conductivity. The system pH was 7.0
unless indicated otherwise, and the pulp freeness was about 380 CSF
with the stock temperature at 52.degree. C. The basis weight was
100 lbs per 3000 ft.sup.2. Unless otherwise indicated, Stalok 300
cationic starch (Tate & Lyle PLC, London, UK) and PerForm.RTM.
PC 8713 flocculant (Hercules Incorporated, Wilmington, Del.) were
added to the wet end of the paper machine in the amount of 0.5% and
0.0125% of dry pulp, respectively. Vinylamine-containing and
acrylamide-containing polymers as described in the above examples
were added as dry strength agents to the wet end of the papermaking
machine at the indicated levels, expressed as a percentage of
weight of polymer active versus dry paper pulp. It is generally
accepted that the dosages typically used for dry strength polymers
on the pilot paper machine are much greater (i.e. at least double)
what a commercial paper machine may use. Ring crush, dry Mullen
burst, and dry tensile tests were used to measure the dry strength
effects. All dry strength results are expressed as a percentage of
the dry strength of paper made without a dry strength resin.
[0050] Drainage efficiency of the various polymeric systems was
compared using one of two tests. One test is the Canadian Standard
Freeness (CSF) Test. The dose of polymer active varied as is
indicated in the tables. The results are summarized in the
following tables and the drainage performances of these
compositions are expressed as percentage increase over the
blank.
[0051] Another method for evaluation of the performance of the
drainage process is the vacuum drainage test (VDT). The device
setup is similar to the Buchner funnel test as described in various
filtration reference books, for example see Perry's Chemical
Engineers' Handbook, 7th edition, (McGraw-Hill, New York, 1999) pp.
18-78. The VDT consists of a 300-ml magnetic Gelman filter funnel,
a 250-ml graduated cylinder, a quick disconnect, a water trap, and
a vacuum pump with a vacuum gauge and regulator. The VDT test was
conducted by first setting the vacuum to 10 inches Hg, and placing
the funnel properly on the cylinder. Next, 250 g of 0.5 wt. % paper
stock was charged into a beaker and then the required additives
according to treatment program (e.g., starch, vinylamine-containing
polymer, acrylamide-containing polymer, flocculants) were added to
the stock under the agitation provided by an overhead mixer. The
stock was then poured into the filter funnel and the vacuum pump
was turned on while simultaneously starting a stopwatch. The
drainage efficacy is reported as the time required to obtain 230 mL
of filtrate. The results of the two drainage tests were normalized
and expressed as a percentage of the drainage performance observed
versus a system that did not include the vinylamine-containing and
acrylamide-containing polymers.
[0052] Polymer A is a vinylamine-containing polymer such as
Hercobond.RTM. 6363 (available from Hercules Incorporated,
Wilmington, Del.) with a molecular weight in the range of 100,000
daltons to 500,000 daltons with an active polymer solids content of
9% to 15%, an N-vinylformamide charge of from 75% to 100%, with a
range of hydrolysis from 50% to 100%.
[0053] Polymer B is a vinylamine-containing polymer such as such as
Hercobond.RTM. 6350 (available from Hercules Incorporated,
Wilmington, Del.) with a molecular weight in the range of 100,000
daltons to 500,000 daltons with an active polymer solids content of
9% to 15%, an N-vinylformamide charge of from 75% to 100%, with a
range of hydrolysis from 30% to 75%.
[0054] Polymer C is an amphoteric acrylamide-containing polymer
such as Hercobond.RTM. 1205 (available from Hercules Incorporated,
Wilmington, Del.) with a molecular weight in the range of 100,000
daltons to 500,000 daltons with an active polymer solids content of
10% to 25% and a sum total monomer charge of anionic and cationic
monomers of from 8% to 20% of the total monomer charge.
[0055] Polymer D is a cationic acrylamide-containing polymer such
as Hercobond.RTM. 1200 (available from Hercules Incorporated,
Wilmington, Del.) with a molecular weight in the range of 100,000
daltons to 500,000 daltons, an active polymer solids content of 10%
to 25% and a cationic monomer charge of 20% to 40%.
[0056] Comparative Polymer E is an anionic acrylamide-containing
polymer such as Hercobond.RTM. 2000 (available from Hercules
Incorporated, Wilmington, Del.) with an anionic monomer charge in
the range of from 5% to 20%.
[0057] Polymer F and Polymer G are cationic acrylamide-containing
aqueous dispersion polymers such as Praestaret.RTM. K325 and K350,
respectively (available from Ashland Inc., Covington, Ky.) with a
molecular weight in the range of 500,000 daltons to 1,500,000
daltons, an active polymer solids content of 20% to 45% and a
cationic monomer charge of 10% to 40%.
[0058] Polymer H is an amphoteric acrylamide-containing
polyelectrolyte complex such as Hercobond.RTM. 1822 (available from
Hercules Incorporated, Wilmington, Del.) with a molecular weight in
the range of 100,000 daltons to 500,000 daltons with an active
polymer solids content of 10% to 25%, and a net charge of from -2
meq/g to +2 meq/g.
[0059] Polymer K is a cationic acrylamide-containing polymer such
as Praestamin.RTM. CL (available from Ashland Inc., Covington, Ky.)
with a molecular weight in the range of 100,000 daltons to 400,000
daltons with an active polymer solids content of 15% to 30%. The
cationic comonomer in Polymer K is
3-(acrylamidopropyl)trimethylammonium chloride. Polymer K can be
blended with vinylamine-containing polymers such as Polymer A and
Polymer B to form a single product.
Example 1
[0060] Table 1 shows the results of a pilot paper machine trial
using Polymer A, amphoteric Polymer C, and cationic Polymer D. The
pH of the system was adjusted to 6.5. Alum (Croydon, Pa.) and
HipHase 35 rosin size (Hercules, Inc., Wilmington, Del.) were used
in the amount of 0.5% and 0.3% of dry pulp, respectively. OptiPlus
1030 amphoteric starch (National Starch, Bridgewater, N.J.) was
added in the place of Stalok 300 cationic starch, still used at
0.5% of dry pulp.
TABLE-US-00001 TABLE 1 Strength and drainage properties of paper
made with Polymer A and an acrylamide containing polymer. Entry
Additive 1 % Additive 2 % Dry Tensile Dry Mullen Burst Ring Crush
Drainage 1 -- -- -- -- 100 100 100 100 2 Polymer A 0.050 -- --
102.4 106.2 105.7 110 3 Polymer A 0.125 -- -- 103.2 110.2 108.7 131
4 -- -- Polymer C 0.100 104.5 105.7 104.8 107 5 -- -- Polymer C
0.250 103.8 113.0 110.1 110 6 Polymer A 0.050 Polymer C 0.100 102.8
108.0 110.4 121 7 Polymer A 0.125 Polymer C 0.100 112.8 116.8 112.6
142 8 Polymer A 0.088 Polymer C 0.175 106.5 112.7 117.8 137 9
Polymer A 0.050 Polymer C 0.250 110.4 109.2 114.2 121 10 Polymer A
0.125 Polymer C 0.250 108.9 121.0 116.9 153 11 -- -- Polymer D
0.100 103.2 93.1 104.6 129 12 -- -- Polymer D 0.250 106.5 106.2
109.9 150 13 Polymer A 0.050 Polymer D 0.100 103.2 98.2 107.0 137
14 Polymer A 0.125 Polymer D 0.100 105.1 108.3 111.4 137 15 Polymer
A 0.088 Polymer D 0.175 107.7 113.0 110.9 150 16 Polymer A 0.050
Polymer D 0.250 104.6 107.7 109.5 142 17 Polymer A 0.125 Polymer D
0.250 106.8 117.4 107.2 147
[0061] Table 1 shows that strength could be markedly improved by
addition of the acrylamide-containing polymer, and that drainage
performance was maintained if not improved by adding more of the
acrylamide-containing polymer. It is noted that the dosages
typically used for dry strength polymers on the pilot paper machine
are much greater (i.e. at least double) than what is comparably
effective on a commercial paper machine. For example if 0.10% of
additive is an effective amount for a dry strength polymer on the
pilot paper machine then the effective amount on the commercial
machine would be about 0.05% or less.
Example 2
[0062] Table 2 shows the drainage performance of three different
acrylamide-containing polymer additives using the same whitewater
and pulp as indicated in the strength testing illustrated in Table
1. The drainage performance was evaluated using the CSF test as
indicated above. Entries 18 to 23 are shown for comparison.
TABLE-US-00002 TABLE 2 Drainage properties of pulp made using
multiple acrylamide-containing polymers with Polymer A. % of dry %
of % of Entry Additive 1 pulp Additive 2 dry pulp drainage 1 -- --
-- -- 100 2 Polymer A 0.050 -- -- 110 3 Polymer A 0.125 -- -- 131 4
-- -- Polymer C 0.100 107 5 -- -- Polymer C 0.250 110 6 Polymer A
0.050 Polymer C 0.100 121 7 Polymer A 0.125 Polymer C 0.100 142 8
Polymer A 0.088 Polymer C 0.175 137 9 Polymer A 0.050 Polymer C
0.250 121 10 Polymer A 0.125 Polymer C 0.250 153 11 -- -- Polymer D
0.100 129 12 -- -- Polymer D 0.250 150 13 Polymer A 0.050 Polymer D
0.100 137 14 Polymer A 0.125 Polymer D 0.100 137 15 Polymer A 0.088
Polymer D 0.175 150 16 Polymer A 0.050 Polymer D 0.250 142 17
Polymer A 0.125 Polymer D 0.250 147 18 -- -- Comparative Polymer E
0.100 96 19 -- -- Comparative Polymer E 0.250 94 20 Polymer A 0.050
Comparative Polymer E 0.100 110 21 Polymer A 0.125 Comparative
Polymer E 0.100 134 22 Polymer A 0.088 Comparative Polymer E 0.175
118 23 Polymer A 0.050 Comparative Polymer E 0.250 104 24 Polymer A
0.125 Comparative Polymer E 0.250 134
[0063] Table 2 demonstrates that the drainage performance of the
pulp slurry is weaker when the anionic acrylamide-containing
polymer (Comparative Polymer E) is used compared to the amphoteric
and cationic acrylamide-containing polymers (Polymer C and Polymer
D). It is noted that the dosages typically used for dry strength
polymers on the pilot paper machine are much greater (i.e. at least
double) than what is comparably effective on a commercial paper
machine. For example if 0.10% of additive is an effective amount
for a dry strength polymer on the pilot paper machine then the
effective amount on the commercial machine would be about 0.05% or
less.
Example 3
[0064] Table 3 shows results of a pilot paper machine trial using a
vinylamine-containing polymer and a cationic acrylamide containing
polymer. In this example, as in all following examples, the pH was
maintained at 7.0, no alum was included in the furnish, and no
sizing agents were employed.
TABLE-US-00003 TABLE 3 Results of pilot paper machine trial at pH
7.0 and in the presence of Polymer B and cationic
acrylamide-containing Polymer D. Entry Additive 1 % Additive 2 %
Dry Tensile Dry Mullen Burst Ring Crush Drainage 1 -- -- -- -- 100
100 100 100 2 Polymer B 0.100 -- -- 96.3 95.7 100.9 98 3 Polymer B
0.300 -- -- 102.5 104.0 112.4 137 4 -- -- Polymer D 0.100 104.5
108.6 107.1 109 5 -- -- Polymer D 0.300 105.7 107.4 106.0 115 6
Polymer B 0.100 Polymer D 0.100 100.8 95.2 105.6 134 7 Polymer B
0.300 Polymer D 0.100 110.1 109.9 116.6 120 8 Polymer B 0.200
Polymer D 0.200 112.9 115.8 119.9 118 9 Polymer B 0.100 Polymer D
0.300 115.7 123.0 113.7 115 10 Polymer B 0.300 Polymer D 0.300
110.4 120.2 111.3 112
[0065] Table 3 demonstrates that high dosages of the two polymers,
excellent strength performance can be achieved when the two
chemicals were added together compared to their performance alone.
This method allows the papermaker to achieve greater efficiency in
chemical use, and the added strength achieved when the two
chemicals are added together allows the papermaker to reduce the
usage of the expensive vinylamine-containing Polymer B. It is noted
that the dosages typically used for dry strength polymers on the
pilot paper machine are much greater (i.e. at least double) than
what is comparably effective on a commercial paper machine. For
example if 0.10% of additive is an effective amount for a dry
strength polymer on the pilot paper machine then the effective
amount on the commercial machine would be about 0.05% or less.
Example 4
[0066] Table 4 shows a pilot paper machine trial employing an
amphoteric acrylamide-containing polymer in combination with the
vinylamine-containing polymer. This trial was performed under
conditions similar to Example 3 above. However, in this case, the
amphoteric acrylamide-containing Polymer C was used, rather than
the cationic acrylamide-containing Polymer D.
TABLE-US-00004 TABLE 4 Results of pilot paper machine trial with
Polymer B and amphoteric acrylamide-containing Polymer C. Entry
Additive 1 % Additive 2 % Dry Tensile Dry Mullen Burst Ring Crush
Drainage 1 -- -- -- -- 100 100 100.0 100 2 Polymer B 0.100 -- --
98.9 104.7 102.2 105 3 Polymer B 0.300 -- -- 104.3 123.5 108.0 143
4 -- -- Polymer C 0.100 100.4 103.0 102.4 102 5 -- -- Polymer C
0.300 100.9 101.9 103.9 109 6 Polymer B 0.100 Polymer C 0.100 102.1
108.1 104.1 95 7 Polymer B 0.300 Polymer C 0.100 101.2 116.4 110.7
142 8 Polymer B 0.200 Polymer C 0.200 103.3 112.3 109.8 119 9
Polymer B 0.100 Polymer C 0.300 103.0 112.8 105.3 105 10 Polymer B
0.300 Polymer C 0.300 106 107.9 117.4 131
[0067] Table 4 shows that Mullen Burst and Ring Crush can be
especially enhanced with the treatment with the two polymers in
tandem versus the polymers in isolation. The drainage performance
was affected only marginally. It is noted that the dosages
typically used for dry strength polymers on the pilot paper machine
are much greater (i.e. at least double) than what is comparably
effective on a commercial paper machine. For example if 0.10% of
additive is an effective amount for a dry strength polymer on the
pilot paper machine then the effective amount on the commercial
machine would be about 0.05% or less.
Example 5
[0068] Table 5 shows the effect of combining aqueous dispersion
polymers with the vinylamine-containing Polymer B.
TABLE-US-00005 TABLE 5 Addition of aqueous dispersion Polymers F
and G to Polymer B to achieve enhanced strength Entry Additive 1 %
Additive 2 % Dry Tensile Dry Mullen Burst Ring Crush Drainage 1 --
-- -- -- 100 100 100 100 2 Polymer B 0.100 -- -- 99.0 107.6 105.4
117 3 Polymer B 0.300 -- -- 101.8 109.8 107.7 138 4 -- -- Polymer F
0.100 101.0 105.3 104.0 124 5 -- -- Polymer F 0.300 102.8 102.4
110.6 155 6 Polymer B 0.100 Polymer F 0.100 97.5 104.6 104.1 136 7
Polymer B 0.300 Polymer F 0.100 104.2 111.8 111.0 135 8 Polymer B
0.200 Polymer F 0.200 104.1 116.9 110.7 140 9 Polymer B 0.100
Polymer F 0.300 105.5 110.4 109.1 157 10 Polymer B 0.300 Polymer F
0.300 108.3 119.2 114.6 125 11 -- -- Polymer G 0.100 98.6 98.4
102.2 123 12 -- -- Polymer G 0.300 99.5 102.3 101.2 151 13 Polymer
B 0.100 Polymer G 0.100 101.1 101.0 106.7 134 14 Polymer B 0.300
Polymer G 0.100 104.9 118.5 108.9 142 15 Polymer B 0.200 Polymer G
0.200 103.6 114.8 110.2 145 16 Polymer B 0.100 Polymer G 0.300
105.4 109.7 106.7 153 17 Polymer B 0.300 Polymer G 0.300 107.2
130.0 111.7 139
[0069] Table 5 demonstrates that drainage can be maintained while
achieving significantly enhanced levels of dry strength with
aqueous dispersion polymers. It is noted that the dosages typically
used for dry strength polymers on the pilot paper machine are much
greater (i.e. at least double) than what is comparably effective on
a commercial paper machine. For example if 0.10% of additive is an
effective amount for a dry strength polymer on the pilot paper
machine then the effective amount on the commercial machine would
be about 0.05% or less.
Example 6
[0070] Table 6 shows the combination of vinylamine-containing
Polymer B with an amphoteric acrylamide-containing polyelectrolyte
complex Polymer H.
TABLE-US-00006 TABLE 6 Pilot paper machine trial using an
amphoteric acrylamide-containing polyelectrolyte complex Polymer H
with Polymer B. Polymer B Polymer H Dry Entry added (%) added (%)
Dry Tensile Mullen Burst Ring Crush 1 0.0 0.0 100 100 100 2 0.0 0.2
99.9 100.8 100.6 3 0.0 0.4 101.1 104.0 102.9 4 0.0 0.6 98.2 103.6
101.5 5 0.1 0.0 93.2 97.7 97.0 6 0.1 0.2 96.6 93.8 100.9 7 0.1 0.4
102.4 102.9 100.9 8 0.1 0.6 102.0 103.5 102.3 9 0.2 0.0 96.6 97.8
101.4 10 0.2 0.2 101.8 107.3 109.1 11 0.2 0.4 109.2 109.5 110.8 12
0.2 0.6 110.4 114.4 112.4 13 0.3 0.0 97.5 102.4 105.3 14 0.3 0.2
107.4 116.0 112.6 15 0.3 0.4 115.6 122.1 115.1 16 0.3 0.6 114.7
121.6 116.2
[0071] Table 6 shows that results comparable to amphoteric
acrylamide-containing polymers can be achieved by using the
amphoteric acrylamide containing polyelectrolyte complex. Excellent
dry strength levels were achieved, at additive levels at which
performance typically begins to level off. It is noted that the
dosages typically used for dry strength polymers on the pilot paper
machine are much greater (i.e. at least double) than what is
comparably effective on a commercial paper machine. For example if
0.10% of additive is an effective amount for a dry strength polymer
on the pilot paper machine then the effective amount on the
commercial machine would be about 0.05% or less.
Example 7
[0072] Table 7 shows dry strength and drainage testing results
using a single product blend of Polymer K and Polymer B. Regardless
of the ratio of the two polymers in the blend, the additive was
used at a dosage level of 0.3% versus the dry pulp.
TABLE-US-00007 TABLE 7 Use of a single-product blend of Polymer K
and B to achieve enhanced dry strength Polymer K: Active solids Dry
Dry Mullen Ring Wet Entry Polymer B (%) Tensile Burst Crush Tensile
Drainage 1 0:4 12.7 101.9 105.5 108.6 373.7 159.6 2 1:3 14.6 105.7
110.7 109.4 347.9 149.0 3 1:1 17.2 107.9 108.7 108.0 297.5 127.2 4
3:1 20.8 108.2 108.8 109.7 200.9 109.0
[0073] Table 7 illustrates that using a single product blend of a
vinylamine-containing polymer and a cationic acrylamide-containing
polymer, improved dry strength results can be obtained in the dry
tensile and dry mullen burst categories while offering comparable
ring crush results. The single product blend is especially useful
in that it offers the papermaker the ease of adding a single
product to the paper machine, but the different blend ratios make
it possible to tune the product to the papermaker's needs. For
instance, if lower wet strength is needed to reduce repulping
energy, a single product blend can be made to meet that need while
maintaining or improving dry strength properties. Or, if the paper
machine is already running near its maximum speed, the amount of
drainage the product provides can be matched to the papermaker's
need without compromising dry strength. Furthermore, the single
product blend can have a significantly higher active solids content
without negatively impacting dry strength, thus reducing ecological
impact due to transportation of low solids content freight to the
paper mill.
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