U.S. patent application number 11/120878 was filed with the patent office on 2006-11-09 for high molecular weight compact structured polymers, methods of making and using.
Invention is credited to Jeffrey R. Cramm, Pious V. Kurian, Peter E. Reed, Michael R. St. John, Winston Su.
Application Number | 20060249269 11/120878 |
Document ID | / |
Family ID | 37308476 |
Filed Date | 2006-11-09 |
United States Patent
Application |
20060249269 |
Kind Code |
A1 |
Kurian; Pious V. ; et
al. |
November 9, 2006 |
High molecular weight compact structured polymers, methods of
making and using
Abstract
A structured water soluble polymer produced by polymerization of
amine-containing monomers or pre-formed polymers is described.
Various structured polymers are prepared and characterized. The
structured polymers are particularly valued in the papermaking
industry.
Inventors: |
Kurian; Pious V.; (Aurora,
IL) ; Reed; Peter E.; (Plainfield, IL) ; St.
John; Michael R.; (Chicago, IL) ; Su; Winston;
(Naperville, IL) ; Cramm; Jeffrey R.; (Batavia,
IL) |
Correspondence
Address: |
NALCO COMPANY
1601 W. DIEHL ROAD
NAPERVILLE
IL
60563-1198
US
|
Family ID: |
37308476 |
Appl. No.: |
11/120878 |
Filed: |
May 3, 2005 |
Current U.S.
Class: |
162/168.3 ;
162/168.2; 526/303.1; 526/319 |
Current CPC
Class: |
D21H 21/18 20130101;
C08F 220/60 20130101; D21H 17/45 20130101; C08F 220/56 20130101;
D21H 17/375 20130101; C08F 220/34 20130101 |
Class at
Publication: |
162/168.3 ;
162/168.2; 526/303.1; 526/319 |
International
Class: |
D21H 21/18 20060101
D21H021/18; D21H 17/45 20060101 D21H017/45; D21H 17/00 20060101
D21H017/00 |
Claims
1. A water-soluble structured polymer, which is the product of the
polymerization reaction of monomers comprising one or more
amine-containing groups, selected from: a. an ethylenically
unsaturated primary, secondary, or tertiary amine and mixtures
thereof, b. a pre-formed polymer comprising a secondary or tertiary
amine; and c. optionally, at least one of acrylamide or
methacrylamide; wherein the structured polymer has a weight-average
molecular weight of from about 100,000 to about 5,000,000; an
apparent conformation coefficient of less than or equal to about
0.40 in sodium nitrate solution having a pH of about 3; and a
greater than or equal to about 80% solubility as determined by
SEC/MALLS.
2. The structured polymer of claim 1, wherein the solubility is
equal to or greater than about 90% as determined by SEC/MALLS.
3. The structured polymer of claim 1, wherein the structured
polymer is characterized by a weight-average molecular weight of
from about 100,000 to about 3,000,000.
4. The structured polymer of claim 1, wherein the polymer is
characterized by a weight-average molecular weight of from about
500,000 to about 2,000,000.
5. An improved dry strength additive for paper comprising a
structured polymer of claim 1.
6. The structured polymer of claim 5, which comprises, as a
copolymer component or copolymer components polymerizing: a.
acrylamide; and b. one or more of an ethylenically unsaturated
amine monomer of formula (I):
H.sub.2C.dbd.CR.sub.1-C(O)-A-(CH.sub.2).sub.mNR.sub.2R.sub.3
wherein R.sub.1 is hydrogen or a linear or branched saturated or
unsaturated alkyl group of 1 to 5 carbons; A is 0 or; NR.sub.4,
wherein R.sub.4 represents hydrogen or an alkyl group of from 1 to
5 carbons; m is 1, 2, 3, or 4; and R.sub.2 and R.sub.3 are
independently hydrogen, linear or branched saturated or unsaturated
alkyl group of 1 to 5 carbons, or R.sub.2 and R.sub.3 together with
the nitrogen atom to which they are attached form a 5- or
6-membered ring optionally containing 1 or 2 additional heteroatoms
selected from N, O or S; and salts thereof.
7. The structured polymer of claim 6, which comprises, as a
copolymer component or copolymer components polymerizing acrylamide
with one or more compounds of formula (1), wherein A represents
oxygen or NH and/or R.sub.1 represents hydrogen or methyl or salts
thereof.
8. The structured polymer of claim 5, which comprises, as a
copolymer component or copolymer components polymerizing: a)
acrylamide; and b) one or more ethylenically unsaturated monomer
selected from the group consisting of
dimethylaminoethylmethacrylate (DMAEM), dimethylaminoethylacrylate
(DMAEA), dimethylaminopropyl methacrylamide (DMAPMA), and
dimethylaminopropyl acrylamide (DMAPAA) and salts thereof.
9. The structured polymer of claim 5, which comprises, as a
copolymer component or copolymer components polymerizing a
pre-formed polymer to which acrylamide has been grafted.
10. The structured polymer of claim 9, wherein the pre-formed
polymer is poly(amidoamine) or DADMAC/DMAPMA copolymer and salts
thereof.
11. The structured polymer of claim 5 which comprises, as a
copolymer component or copolymer components polymerizing
monoallylamine (MAA), diallyamine, and triallylamine and mixtures
thereof.
12. A process for preparing a structured polymer of claim 1,
wherein the polymer is derived from at least one amine monomer
composition contained within a reaction mixture prepared by: a)
providing an aqueous solution of about >1 mole % ethylenically
unsaturated amine monomer based on total mer units present in the
final polymer; b) initiating polymerization of the amine monomer
with an oxidant of greater than about 1 mole % based on total mer
units in the final polymer at a temperature of below about 60 C at
a rate sufficient to obtain the desired structured polymer as
measured by SEC/MALLS and; c) adjusting the pH of the solution
during polymerization to at least about 4 or above; and d)
recovering the resulting structured amine-containing polymer.
13. The process of claim 12, wherein the oxidant is a
persulfate.
14. The process of claim 13, wherein the oxidant, the amine monomer
and chain transfer agent are added to the polymerization reaction
in either a semi-continuous or continuous manner during
polymerization.
15. A process for preparing the structured dry strength polymer of
claim 5, wherein the polymer is derived from polymerizing an amine
monomer composition contained within a reaction mixture prepared
by: a) providing an aqueous solution of about greater than about 1%
mole percent of ethylenically unsaturated amine monomer of claim 5,
based on the total moles of mer units in the polymer, and salts
thereof; b) greater than about 50% mole percent acrylamide, based
on the total moles of mer units present in the final polymer; c)
initiating polymerization with an oxidant added in an amount of
about 1-5 mole percent, based on the total moles of mer units in
the polymer; d) adjusting the pH of the solution during
polymerization to at least about 4 or above, and e) recovering the
resulting structured polymer and salts thereof.
16. The process of claim 15, wherein the ethylenically unsaturated
amine monomer is added in a semi-batch addition.
17. The process of claim 15, wherein the oxidant is a
persulfate.
18. A process for preparing a structured polymer of claim 9,
wherein the polymer is derived from copolymer component Or
copolymer components within a reaction mixture prepared by: a)
Providing an aqueous solution of a pre-formed polymer comprising a
secondary or tertiary amine; b) Mixing with acrylamide monomer such
that the amine to acrylamide mole ratio is greater than one mole
percent; c) Initiating polymerization of the acrylamide monomer
with an oxidizing initiator at pH greater than seven and
temperature below 60 C d) Recovering the resulting structured
amine-containing -polymer.
19. The process of claim 18, wherein the pre-formed polymer is
poly(amidoamine) or DADMAC/DMAPMA copolymer and salts thereof.
20. The process of claim 18, wherein the oxidant is a
persulfate.
21. The process of claim 18, further comprising a chain transfer
agent added to the polymerization reaction in either a
semi-continuous or continuous manner during polymerization.
22. A process for improving the internal dry strength of paper
comprising treating an aqueous suspension of papermaking fibers
with a structured polymer, wherein the structured polymer is
characterized by: a) a weight-average molecular weight of from
about 100,000 to about 5,000,000; b) an apparent conformation
coefficient of less than or equal to 0.40 in 0.1 M sodium nitrate
solution having a pH of about 3; and c) a greater than or equal to
80% solubility as determined by SEC/MALLS; wherein the resulting
structured polymer is derived from copolymer component or copolymer
components comprising (i) optionally acrylamide or methacrylamide;
(ii) an amine-containing group selected from the group consisting
of an ethylenically unsaturated primary, secondary, or tertiary
amine and mixtures thereof; or (iii) a pre-formed polymer
comprising a secondary or tertiary amine.
23. A dry strength additive of claim 5, wherein an effective amount
of the polymer ranges from about 0.1 lb/tn to about 30 lb/tn of
said additive per ton of finished paper.
24. A dry strength additive of claim 5, wherein an effective amount
of said polymer ranges from about 0.5 lb/tn to about 20 lb/tn of
said additive per ton of finished paper.
25. A dry strength additive according to claim 5, wherein an
effective amount of said polymer ranges from about 0.5 lb/tn to
about 6 lb/tn of said additive per ton of finished paper.
26. A method of increasing the dry strength of a paper material
wherein one or more structured polymer s according to claim 5 is
applied to or incorporated into the papermaking process.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to materials and methods for
the preparation of high molecular weight compact structured
water-soluble polymers. These polymers are particularly useful in
the paper making industry.
BACKGROUND OF THE INVENTION
[0002] Structured polymers and copolymers have attracted
considerable attention over the past decades due to new and
improved properties of the resulting polymers. The term
"structured" as used herein with respect to synthetic polymers is
intended to designate non-linear polymers.
[0003] Polymers such as acrylamide polymers have been used
throughout the papermaking process as dry strength agents, drainage
agents, retention aids, coagulants, dispersants, etc. Dry strength
is an important property, which must be met at some minimum level
to meet the end use for paper and paperboard products. Acrylamide
containing polymers are well known in the paper industry to provide
dry strength. Linear acrylamide polymers having a weight-average
molecular weight range from about 50,000 to somewhat greater than
5,000,000 have conventionally been used as dry strength agents.
Existing acrylamide based commercial examples include acrylic acid
(AA)/acrylamide (AcAm) copolymer, glyoxalated
diallyldimethylammonium chloride (DADMAC)/AcAm, and an amphoteric
polymer composed of AcAm/itaconic
acid/dimethylammoniumethylmethacryl ate
(DMAEM)/dimethylammoniumethylacrylate benzyl chloride quat (DMAEA
BCQ). These commercial strength agents suffer from various
drawbacks including handling issues, paper machine process issues
or inadequate dry strength. Demands in modern paper industry have
resulted in need for improved dry strength agents. In addition to
allowing papermakers to achieve their product strength
specifications, the dry strength additive enables papermakers to
reduce basis weight, substitute low cost fiber, increase filler
loading, increase machine speeds and modify sheet properties.
SUMMARY OF THE INVENTION
[0004] A water-soluble structured polymer having a weight-average
molecular weight of from about 100,000 to about 5,000,000 is
provided. This polymer is obtained by polymerizing one or more
amine-containing unsaturated monomers or polymers. The
polymerization reaction is a reaction mixture of at least one of
amine-containing groups comprising ethylenically unsaturated
primary, secondary, or tertiary amines and mixtures thereof, a
pre-formed polymer comprising a secondary or tertiary amine; and
optionally, at least one of acrylamide or methacrylamide. The
resulting structured polymer has an apparent conformation
coefficient of less than or equal to about 0.40 in sodium nitrate
solution, measured at a pH of about 3 and a greater than or equal
to about 80% solubility as determined by SEC/MALLS techniques.
[0005] A number of water-soluble structured polymers are derived
from the polymerization reaction of monomers comprising one or more
amine-containing groups. A high molecular weight water-soluble
structured polymer is obtained from polymerizing one or more
ethylenically unsaturated amine monomers. A non-acrylamide based
terpolymer was obtained from copolymer components of monoallylamine
(MAA), diallyamine (DAA), and triallylamine (TAA) and mixtures
thereof.
[0006] An acrylamide based high molecular weight water-soluble
structured polymer is provided from polymerization of acrylamide
and one or more of ethylenically unsaturated amine monomers. For
example, a reaction mixture may contain acrylamide (AcAm) and
dimethylaminoethylmethacrylate (DMAEM) resulting in structured
AcAm/DMAEM copolymers.
[0007] Polymer components comprising a pre-formed polymer to which
acrylamide has been grafted result in another type of structured
polymer. Pre-formed polymers, include, but not limited to,
poly(amidoamine) or diallyldimethylammonium chloride
(DADMAC)/dimethylaminopropyl methacrylamide (DMAPMA) copolymer.
[0008] The structured polymers are useful as improved dry strength
additive for papermaking process. The characteristics of dry
strength structured polymers are identified by: [0009] a) a
weight-average molecular weight of from about 100,000 to about
5,000,000; [0010] b) an apparent conformation coefficient of less
than or equal to about 0.40 in sodium nitrate solution having a pH
of about 3; and [0011] c) a greater than or equal to about 80%
solubility as determined by SEC/MALLS technique.
[0012] Dry strength agents include, but are not limited to,
co-monomers of (a) acrylamide; and (b) one or more ethylenically
unsaturated monomers. Monomers including but not limited to
dimethylaminoethylmethacrylate (DMAEM), dimethylaminoethylacrylate
(DMAEA), dimethylaminopropyl methacrylamide (DMAPMA), and
dimethylaminopropyl acrylamide (DMAPAA) and salts thereof.
DETAILED DESCRIPTION OF THE INVENTION
A. Definitions
As used herein, the terms set forth below are meant to designate
the following:
[0013] "About" is equal to, greater or less than 2 digital units on
either side of the reference number.
[0014] "Structured polymer" refers to a compact non-linear polymer
with controlled branching as prepared by the polymerization process
disclosed herein, the structure of which includes any deviation
from linearity in the backbone polymer chain.
[0015] "An ethylenically unsaturated primary, secondary, or
tertiary amine" refers to amine containing compounds having
carbon-carbon double bonds that are reactive towards free radical
polymerization.
[0016] "Monomer" refers to a polymerizable allylic, vinylic or
acrylic compound.
[0017] "A pre-formed polymer comprising a secondary or tertiary
amine" is a polymer backbone containing amine groups.
[0018] "Weight-average molecular weight" refers to the molecular
weight average of polymer determined by static light scattering
measurement, specifically by
Size-Exclusion-Chromatography/Multi-Angle-Laser-Light-Scattering
(SEC/MALLS) technique. The instant structured polymer has a
weight-average molecular weight of from about 100,000 to about
5,000,000.
[0019] "Apparent conformation coefficient" is defined by the slope
of the double logarithmic plot (root-mean-square-radius versus
molecular weight of polymer) obtained from the ASTRA software
(Wyatt Technology), specifically the top 20% of molecular weight
distribution of polymer eluted from SEC columns is calculated.
[0020] "SEC" refers to Size-Exclusion-Chromatography that is a
chromatography technique for polymer separation based on
hydrodynamic volume of polymer.
[0021] ""MALLS" refers to Multi-Angle-Laser-Light-Scattering
instrument (DAWN DSP-F) provided by Wyatt Technology
[0022] "Improved dry strength additive" refers to the compact
structured acrylamide polymer preferably containing acrylamide
and/or methacrylamide in a proportion of 50 mole % or more,
preferably 75-99 mole %, and especially 85-95 mole % which when
added to the papermaking process increases dry strength by about
5%.
[0023] "Batch addition" refers to a chemical addition process in
which all the reaction components are added to the reactor before
the reaction commences and then held under controlled conditions
until the desired endpoint is reached.
[0024] "Semi-batch" refers to as a chemical process in which one or
more of the reaction components are added (in part or in whole)
after the reaction commences. A "semi-batch addition" refers to the
reaction component that is added over the course of the
reaction.
[0025] "Oxidant" refers to polymerization initiators including, but
not limited to, persulfate and peroxide types, ammonium persulfate,
potassium persulfate, sodium persulfate, hydrogen peroxide,
tert-butylhydroperoxide benzoyl peroxide and tert-butyl
peroxide.
B. Characterization of Monomers
[0026] One or more primary, secondary or tertiary amine-containing
monomers provide the structured polymers of the invention. Specific
examples of monomers providing structured polymers include amines
such as N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl
methacrylate, N,N-dimethylaminoethyl acrylate,
N,N-dimethylaminopropyl methacrylamide, and
N,N-dimethylaminopropylacrylamide, vinylamine, monoallylamine,
(MAA) diallylamine and triallylamine and salts thereof.
[0027] The ethylenically unsaturated monomers employed in this
invention may further include anionic, non-ionic, cationic,
hydrophobic and hydrophilic types.
[0028] Exemplary anionic monomers include unsaturated carboxylic
acids such as acrylic acid, methacrylic acid, itaconic acid, maleic
acid and fumaric acid, and salts thereof; and vinylsulfonic acid,
styrenesulfonic acid and acrylamidomethylpropanesulfonic acid, and
salts thereof.
[0029] Examples of non-ionic monomers include, but are not limited
to, acrylamide, methacrylamide, N-vinylmethylacetamide, N-vinyl
methyl formamide, vinyl formamide, vinyl acetate, vinyl
pyrrolidone, methyl methacrylate, methacrylic esters, other acrylic
or ethylenically unsaturated esters, styrene, and
acrylonitrile.
[0030] Illustrative examples of cationic monomers include
quaternary amines salts such as N,N-dimethylaminoethyl
methacrylate, N,N-diethylaminoethyl methacrylate,
N,N-dimethylaminoethyl acrylate, N,N-dimethylaminopropyl
methacrylamide, and N,N-dimethylaminopropylacrylamide; and salts
thereof (including quaternary salts). Examples of quaternary salts
include dimethyldiallyammonium chloride and dimethyl aminoethyl
acrylate methyl chloride quat.
[0031] Exemplary hydrophobic monomers include N-alkyl
(meth)acrylamide derivatives such as N,N-di-n-propylacrylamide,
N-n-butylacrylamide, N-n-hexylacrylamide, N-n-hexylmethacrylamide,
N-n-octylacrylamide, N-n-octylmethacrylamide,
N-tert-octylacrylamide, N-dodecylacrylamide, and
N-n-dodecylmethacylamide; N-(.omega.-glycidoxyalkyl)
(meth)acrylamide derivatives such as N,N-diglycidylacrylamide,
N,N-diglycidylmethacrylamide, N-(4-glycidoxybutyl)acrylamide,
N-(4-glycidoxybutyl)methacrylamide,
N-(5-glycidoxypentyl)acrylamide, and N(6-glycidoxyhexyl)acrylamide;
(meth)acrylate derivatives such as methyl (meth)acrylate, ethyl
(meth)-acrylate, butyl (meth)acrylate, lauryl (meth)acrylate,
2-ethylhexyl (meth)acrylate, and glycidyl (meth)acrylate; olefins
such as acrylonitrile, methacrylonitrile, vinyl acetate, vinyl
chloride, vinylidene chloride, ethylene, propylene, and butene;
styrene; .alpha.-methylstyrene; butadiene; and isoprene
[0032] Illustrative examples of hydrophilic monomers include
acetoneacrylamide, N,N-dimethylacrylamide,
N,N-dimethylmethacrylamide, N-ethylmethacrylamide,
N-ethylacrylamide, N,N-diethylacrylamide, N-propylacrylamide,
N-acryloylpyrrolidine, N-acryloylpiperidine, N-acryloylmorpholine,
hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl
methacrylate, hydroxypropyl acrylate, various methoxypolyethylene
glycol (meth)acrylates, and N-vinyl-2-pyrrolidone.
[0033] One or more of the above monomers may be used in the process
for preparing the polymer of this invention. For example one
acrylamide based monomer is used as monomer to prepare a water
soluble structured polymer. For example, a cationic monomer
reaction mixture may contain acrylamide and dialkylaminoalkyl
acrylate (as acid salt or quaternary salt) with dialkylaminoalkyl
acrylate. An anionic monomer containing system can include
acrylamide and acrylic acid monomer along with amine monomer needed
to provide structure.
C. Characteristics of the Structured Polymers
[0034] The structured polymers of this invention exhibit a high
molecular weight, a compact solution structure, and a high
water-solubility due to the introduction of branches accomplished
by the unique polymerization process.
[0035] The advantages of the instant structured polymer of this
invention are reflected in the apparent conformation coefficient,
solubility and high molecular weight as determined by SEC/MALLS
technique. A low value of the apparent conformation coefficient is
indicative of 3-dimensional structuring while the good polymer
recovery indicates that the structuring has not led to gel-like
structures, which are less active. The apparent conformation
coefficient is determined from SEC/MALLS measurements using the top
20% of the molecular weight distribution. The slope of the
conformation plot defines the apparent conformation coefficient and
differentiates structured polymers from linear polymers. The
ability of the polymers to elute from SEC column is indicative of
polymer solubility in dilute solution. Polymers structured through
too much cross-linking or branching have a tendency to form
insoluble fractions, and these fractions do not pass through the
SEC column under the conditions. The specialized polymerization
conditions employed does not introduce a crosslinking agent to
produce the polymers of the instant invention, and this is thought
to allow the polymers to display high water-solubility along with a
high molecular weight, compact structure. The instantly claimed
structured polymers are characterized by an apparent conformation
coefficient of less than or equal to about 0.4 and concurrent
solubility greater than or equal to about 80% as measured by
SEC/MALLS technique. Exemplary apparent conformation coefficients
less than about 0.4 or less with about greater than 90% are
exhibited by the majority of the resulting polymers. For example, a
structured AcAm/DMAEM (90/10 mole ratio) copolymer exhibits an
apparent conformation coefficient of about 0.3, 100% recovery,
1,000,000 weight-average molecular weight as determined by
SEC/MALLS technique.
[0036] Acrylamide copolymers were polymerized with DMAEM and DMAPMA
under conditions expected to provide branching from alkyl group
attached to the amine. Illustrative structured cationic copolymers
AcAm/DMAEM (90/10), AcAm/DMAPMA (90/10), DMAPAA/AcAm/MAA(monoallyl
amine) and DMAPMA/DMAPAA/AcAm/MAA exhibited apparent conformation
coefficients less than about 0.4 and greater than 90% SEC
recovery.
D. Structure Determination
[0037] The unique three-dimensional structure of polymers as
described in "examples" was determined by a size-exclusion
chromatography/multi-angle laser light scattering (or SEC/MALLS)
technique. Size exclusion chromatography (SEC) was performed by
using a series of TSK-GEL PW columns from TOSOH BIOSCIENCE, a
multi-angle laser light scattering detector (MALLS, model: DAWN
DSP-F) and an interferometric refractometer (OPTILAP DSP) from
Wyatt Technology. The aqueous mobile phase contained 0.1 molar
sodium nitrate, phosphate buffer solution (pH 3) and a small amount
of sodium azide. Data collection and analysis were performed with
ASTRA software from Wyatt Technology. A Debye model and a 3.sup.rd
order detector fit method were employed in data analysis.
[0038] The ability of SEC/MALLS technique to determine molecular
weight and size of polymer at each elution volume slice is of great
important for the determination of polymer conformation. An
apparent conformation coefficient is defined by the slope of the
double logarithmic plot of root-mean-square radius versus molecular
weight of polymer. A typical linear random-coil polymer in a good
solvent has a value between 0.5 and 0.6 (ref: P. J. Wyatt "Review:
Light scattering and the absolute characterization of
macromolecules." Analytica Chimica Acta. 272 (1993). A
three-dimensional structured polymer is obtained when the apparent
conformation coefficient deviates from that measured for a linear
polymer. For example, the value of a branched polymer is lower than
0.5 because of compact structure. The apparent conformation
coefficient of polymers as described in "examples" was determined
from top 20% of molecular weight distribution. All of the samples
for SEC/MALLS analysis were pre-filtered with a syringe filter
(Acrodisc.RTM. from PALL, pore size: 1.2 .mu.m, diameter: 25 mm) to
protect columns. The solubility of polymer is determined from
polymer recovery that is the percentage of polymer eluted from SEC
columns.
E. Polymerization Process Characterization
[0039] The structured polymers are prepared by an aqueous
polymerization reaction employing a redox reaction between the
amine of the amine-containing monomer and an oxidizing initiator.
As a polymerization process for the acrylamide polymer in the
present invention, radical polymerization is preferred. As a
polymerization solvent, a polar solvent such as water, an alcohol
or dimethylformamide is preferred. Aqueous solution polymerization
is however preferred when the acrylamide polymer is used as a paper
strength agent. In the case of aqueous water polymerization, an
organic solvent such as an alcohol can be used in combination to
such an extent that the dispersibility would not be impaired by
deposition or precipitation of the polymer
[0040] The polymerization of the acrylamide polymer in the present
invention can be conducted by such a batch process that all the
monomers are charged at once in a reaction vessel and are then
polymerized. To obtain an aqueous solution having a high
concentration of 22% or more, it is however more desired to conduct
the polymerization by such a semi-batch process that the
polymerization is conducted while adding dropwise a portion of or
the entire portion of the monomers. This semi-batch polymerization
process makes it possible not only to facilitate removal of
polymerization heat from a solution containing monomers at high
concentrations but also to control the molecular structure, for
example, to facilitate the formation of the polymer into a uniform
branched and compact structure.
[0041] No particular limitation is imposed on the polymerization
initiator as long as it is an oxidant. A water-soluble
polymerization initiator is preferred. The polymerization initiator
can be added either at once or dropwise to the aqueous solution of
the monomers. Specific examples of the polymerization initiator
include, as persulfate and peroxide types, ammonium persulfate,
potassium persulfate, sodium persulfate, hydrogen peroxide, benzoyl
peroxide and tert-butyl peroxide.
[0042] To achieve the desired compact structure of the claimed
polymers, the polymerization process comprises initiating an
aqueous solution of minimum of about 1 mole % amine monomer and any
other co-monomers with a minimum of about 1 mole % (based on total
moles of monomer(s)) of oxidant, such as persulfate. During
polymerization, the reaction temperature below about 60 C with a pH
of about 4 or above provides optimal results.
[0043] Optionally, crosslinking is controlled by adding a suitable
chain transfer agent (during or after polymerization), or by
reducing the pH below about 3 after most of the monomers have
polymerized.
[0044] A polymer useful as a dry strength agent is prepared with
the general process described above, except acrylamide is the
predominant co-monomer. In addition, the weight average MW of the
polymer must be >100,000 g/mol. Enhanced dry strength effects
were obtained from polymers prepared from semi-batch addition of
the anine monomer during polymerization. The other factors
enhancing performance of the resulting polymer may include the use
of monomer, which may dictate the need for semi-batch addition
versus batch addition over the course of polymerization.
F. Activity Characterization
[0045] The polymers and aqueous solutions so obtained can exhibit
various excellent effects as paper strength agents. Use of the
acrylamide polymers according to the present invention as paper
strength agents is described in further detail.
[0046] Dry strength was evaluated using standard procedures for
handsheet making and testing. The paper stock used was 80/20 wt %
of unrefined bleached hardwood kraft dry lap and unrefined bleached
softwood kraft dry lap. Dry lap furnish was diluted with tap water
of pH=7.9, conductivity=267 microS/cm. Treatment of the stock prior
to sheet making included the addition of dry strength agent for two
minutes followed by addition of a cationic retention aid.
[0047] Handsheet making was conducted with a Noble & Woods
handsheet former utilizing a single nip felted press and drum dried
to bone dry conditions. Sheet strength was evaluated as tensile
index, STFI index, and burst ratio using TAPPI standard methods.
Sheet (basis) weights and apparent sheet densities (calculated from
caliper and basis weight) were evaluated as check on the sheet
making procedure and to ensure that strength comparisons were made
at equal apparent sheet densities.
EXAMPLES
[0048] The foregoing may be better understood by reference to the
following examples, which are presented for purposes of
illustration and are not intended to limit the scope of this
invention.
Example 1
Synthesis of Structured AcAm/DMAEM with Semi-Batch Addition of
Amine Monomer
[0049] Synthesis was carried out in a standard 1500 mL laboratory
reactor equipped with a stainless steel stirring assembly (a
half-moon Teflon blade and a non pitched impeller). The reactor was
also equipped with heating and cooling capability. 243 g AcAm
solution (49.5%) was added to a 1000 mL flask followed by 0.20 g
EDTA, 16.36 g DMAEM, 647.84 g distilled water. 4.70 g sulfuric acid
was added to adjust the pH to .about.7.0. This solution was
transferred to the reactor and cooled to 15.degree. C. 7.50 g
Sodium persulfate was dissolved in a beaker with 38 g of water and
kept on the side. 3.0 g Sodium hypophosphite was dissolved in 12 g
of water and placed in a syringe attached to a syringe pump. 14 g
DMAEM was placed in a separate syringe attached to a syringe pump.
2.40 g sulfuric acid was dissolved in 11 g distilled water and kept
in a beaker. The reaction was initiated with the addition of SPS
solution at once and at the same started 2 ml/min addition of DMAEM
and Sodium hypophosphite from the syringe pumps. At the end of
reaction (about 6 minutes) the acid solution was added to kill the
reaction and stabilize the product.
Example 2
Synthesis of AcAm/DMAEM: Batch Process
[0050] Synthesis was carried out in a standard 1500 mL laboratory
reactor equipped with a stainless steel stirring assembly (a
half-moon Teflon blade and a non pitched impeller). The reactor was
also equipped with heating and cooling capability. 243 g AcAm
solution (49.5%) was added to a 1000 mL flask followed by 0.20 g
EDTA, 30.36 g DMAEM, 644.84 g distilled water. 6.70 g sulfuric acid
was added to adjust the pH to .about.7.0. This solution was
transferred to the reactor and cooled to 15.degree. C. 7.50 g
Sodium persulfate (SPS) was dissolved in a beaker with 38 g of
water and kept on the side. 5.0 g Sodium hypophosphite was
dissolved in 12 g of water and placed in a syringe attached to a
syringe pump. 1.40 g sulfuric acid was dissolved in 11 g distilled
water and kept in a beaker. The reaction was initiated with the
addition of SPS solution at once and at the same time started 2
ml/min addition Sodium hypophosphite from the syringe pumps. At the
end of reaction (about 6 minutes) the acid solution was added to
kill the reaction and stabilize the product.
[0051] Either process can be used in polymerization of co-monomers
such as DMAPMA, DMAPAA, DMAEA with AcAm under similar batch or semi
batch process.
Example 3
Synthesis of AcAm/DMAPMA Copolymer by Semi-Batch Addition
[0052] A 250 mL resin flask equipped with a mechanical stirrer and
a nitrogen inlet was charged with 78 grams deionized water
containing 128 ppm EDTA. In separate beaker, a monomer solution
comprised of 30 parts of 50 wt. % aqueous acrylamide and 4 parts
DMAPMA were combined, and the resulting solution was purged with
nitrogen for 30 minutes and then charged to a syringe. In a similar
fashion, an initiator solution was prepared, by combining 4 parts
water, 0.75 parts 50 wt. % sodium hydroxide, and 1.12 parts sodium
persulfate, and placed in a syringe. A post-treat solution
comprised of 0.5 parts sodium hypophosphite monohydrate dissolved
in 2 parts water was also prepared.
[0053] The water in the reactor was stirred and purged with
nitrogen for 20 minutes. Then a continuous feed of the monomer
solution to the reactor was started, followed by the commencement
of a continuous feed of the initiator solution. The monomer
solution was fed at a rate of about 7 mL/hr, and the initiator
solution was fed at a rate of about 0.5 mL/hr. The reaction
viscosity was carefully monitored until it reached a point, after
about 58 minutes, where mixing was difficult and the reactor
contents began to pull away from the reactor walls. At this point,
the pre-prepared post-treat solution was added immediately to the
reaction. The viscosity decreased and the reactor contents were
cooled and dispensed, providing a structured AcAm/DMAPMA (90/10)
copolymer solution.
Example 4
Synthesis of Structured Poly(DMAPAA) Homopolymer
[0054] To a 100 mL resin flask was added 33 g water. Separately, a
monomer and initiator solutions were prepared. The monomer solution
was comprised of 10 g DMAPAA dissolved in 31.7 g water and adjusted
to pH 9 with 4.83 g concentrated HCl. The initiator solution was
comprised of 0.2 sodium persulfate dissolved in a mixture of 0.13 g
50% NaOH and 7 g water. Both solutions were added over 2 hours to
the stirring, nitrogen-purged resin flask contents. The reactor
contents were allowed to mix further for 1 hour and then treated
with 1.5 g concentrated HCl and 0.05 g sodium persulfate. The
product, comprised of an 11.3 wt. % solution of structured
poly(DMAPAA) homopolymer.
Example 5
Synthesis Using Pre-Formed Polymer: AcAm/DADMAC/DMAPMA
[0055] In a 200 ml glass reactor equipped with a paddle stirrer,
nitrogen purge tube, and condenser was mixed 16.5 g of a 30.1%
aqueous solution of a DADMAC/DMAPMA backbone polymer and 70.2 g of
DI water. The mole ratio of DADMAC to DMAPMA was 80:20. Acrylamide
monomer, 10.3 g of a 49% aqueous solution, and
diethylenetriaminepentaacetic acid pentasodium salt, 0.2 g of a 2%
aqueous solution, were added to the backbone polymer solution. The
pH of the resulting mixture was raised to 11 with NaOH. The
solution was stirred at 200 rpm and purged with nitrogen for 30
minutes to remove all oxygen. Sodium persulfate, 2.4 g of a 5%
aqueous solution, was added to the solution at 24.degree. C. The
reaction temperature gradually increased to 38.degree. C. in 60
minutes as the polymerization progressed, and the solution became
viscous. A warm water bath was used to hold the temperature between
40 and 45.degree. C. for 3 hr. The polymerization of acrylamide
reached 97% conversion.
Example 6
Example Using Pre-Formed Polymer Poly(Amidoamine)
[0056] In a 200 ml glass reactor equipped with a paddle stirrer,
nitrogen purge tube, and condenser was mixed a poly(amidoamine)
backbone, 6.9 g of a 50% aqueous solution, and distilled (DI)
water, 58.6 g. The poly(amidoamine) was made from adipic acid and
diethylenetriamine. Acrylamide monomer, 23.6 g of a 49% aqueous
solution, and diethylenetriaminepentaacetic acid pentasodium salt,
0.3 g of a 2% aqueous solution, were added to the backbone polymer
solution. The pH of the resulting mixture was raised to 11 with
Na.sub.2CO.sub.3. The solution was stirred at 200 rpm and purged
with nitrogen for 30 minutes to remove all oxygen. Sodium
persulfate, 9.66 g of a 20% aqueous solution, was added to the
solution at 25.degree. C. The reaction temperature increased to
55.degree. C. in 5 minutes as the polymerization progressed, and
the solution became viscous. A warm water bath was used to hold the
temperature at about 50.degree. C. for 5 hr. The polymerization of
acrylamide reached 99.8% conversion. After cooling to 25.degree. C.
the pH was reduced to 7.1 with H.sub.2SO.sub.4.
Example 7
Synthesis of AcAm-Free Poly(Allylamines)
[0057] No acrylamide was used to synthesize this polymer. The
polymer was made from a 72:23:5 mole ratio mixture of
monoallylamine, diallylamine, and triallylamine using a thermally
activated azo initiator at high temperature in water.
[0058] In a 500 ml glass reactor equipped with a paddle stirrer,
nitrogen sparge tube, and condenser was mixed DI water, 76.8 g, and
hydrochloric acid, 92.3 g of a 37% aqueous solution. After cooling
the acid solution in an ice bath, a mixture of allylamine, 38.5 g,
diallylamine, 20.9 g, and triallylamine, 6.4 g, was added dropwise
to the acid. The temperature of the reactor contents was kept below
30.degree. C. during this charging step. The monomer solution was
then purged with nitrogen at 25-30.degree. C. and a slurry of
2,2'-azobis[2-methyl-N-(2-hydroxyethyl) propionamide], 5.0 g in 10
g DI water, was added. The reactor contents were heated to
85.degree. C. for 3 hr. After observing no viscosity increase, the
reactor contents were further heated to 95.degree. C. for 11 hr.
The solution became very viscous. DI water, 84 g, was added before
cooling to room temperature. The concentration of unreacted amines
in this product were measured by gas chromatography. The
conversions of the mono, di, and triallylamine to polymer were 45%,
83% and 94%, respectively. The concentration of the structured
polyamine in this sample was 12.2%.
Comparative Example
Synthesis of Linear AcAm/DMAPMA Copolymer
[0059] The DMAPMA monomer (3.16 g), acrylamide monomer (24.34 g of
a 50 wt. % solution), and water (56 g) were combined in a beaker
and adjusted to pH 4 with concentrated HCl (about 1.95 g,
representing a small molar excess over the amount of DMAPMA used).
The reaction solution was charged to a 250 mL resin flask equipped
with a mechanical stirrer and a nitrogen inlet, and then purged
with nitrogen for 20 minutes. Sodium persulfate, 0.3 g, was added
and the reaction was allowed to stir overnight. The reaction was
then diluted with 10 g water and post-treated with a solution of
0.5 g sodium hypophosphite monohydrate dissolved in 1.5 g water.
This provided a linear AcAm/DMAPMA solution polymer for comparative
purposes.
Example 8
Comparison of Apparent Conformation Coefficients of Linear
Polyacrylamide, Linear or Structured AcAm/DMAEM and AcAm/DMAPMA
Copolymers
[0060] Copolymers were synthesized under conditions for providing
linear or structured AcAm copolymers. Evaluation of the apparent
conformation coefficients in Table 1 indicates that the linear
polymers (1* through 3*) have apparent coefficient values of
greater than or equal to about 0.50 in contrast to non-linear
structured copolymers (4* through 6** and 8** through 10**) with
reduced values of about 0.25 to 0.30, which are consistent with
polymer structuring. All structured polymers in Table 1 exhibited
SEC column recovery greater than or equal to 80% solubility
characteristic of water-soluble structured polymers described
herein. TABLE-US-00001 TABLE 1 Measured Properties of Linear vs.
Structured (AcAm/DMAEM orAcAm/DMAPMA 90/10 mole M.sub.w by SEC/ SEC
% Conformation Samples Composition MALLS Recovery Coefficient 1*
AcAm 1300,000 100 0.57 2* AcAm 1900,000 100 0.59 3* AcAm/DMAEM
1200,000 80 0.50 4** AcAm/DMAEM 1100,000 100 0.25 5** AcAm/DMAEM
950,000 97 0.25 6** AcAm/DMAEM 1000,000 100 0.30 7.sup.b AcAm/DMAEM
28,000 -- -- 8** AcAm/DMAEM 1100,000 100 0.29 9** AcAm/DMAEM
810,000 98 0.28 10** AcAm/DMAPMA.sup.c 1000,000 100 0.28 *linear;
**structured .sup.aThe apparent conformation coefficient was
determined from the high MW polymer fraction, i.e. top 20% of the
eluted polymers. .sup.bWas made by hydrolyzing sample 6.
.sup.cBased on dn/dc of polyacrylamide.
[0061] It is evident that each structured acrylamide copolymer in
Table 1 meet the parameters characterizing the polymers of the
invention. Linear acrylamide polymers were prepared in the absence
of conditions allowing controlled branching technique. Any
polymerization process according to the prior art technique cannot
provide a polymer having such a novel structure and excellent
physical properties.
Example 9
Dry Strength Results Correlated to Apparent Conformation
Coefficient
Dry Strength Testing Protocol:
Dry strength was evaluated using standard procedures for handsheet
making and testing. The paper stock used and its treatment prior to
sheet making are described as follows:
Stock Used for Dry Strength Testing
52.0 liters thin stock at 1.0 wt %; 520 grams total fiber
Fiber Composition: 80 wt % unrefined BHWK dry lap (CSF=560 mls)
[0062] 20 wt % unrefined BSWK dry lap (CSF=750 mls) Consistency:
1.01 wt % (measured) Dilution Water: Naperville tap water, pH=7.9,
conductivity=267 microS/cm Stock Treatment Conditions for Dry
Strength Testing
[0063] Dosing Volumes--2700 mls @ 1.0 wt % total volume to split
into 5 500 mls/Sheet TABLE-US-00002 Dosing Sequence 750 rpms with 2
turbine props, time, sec Event 2 in dia 0 Start 10 Add strength
Additive 130 Add cationic 2 min 10 sec retention aid 150 Stop and
make Sheets 2 min 30 sec
[0064] Product Make Up TABLE-US-00003 Cationic retention aid 0.169
wt % product 4 ml = 0.5 lb/ton product for 2700 mls Strength
Additives 0.675 wt % actives 1 ml = 0.5 lb/ton actives for 2700
mls
[0065] Handsheet making was conducted with a Noble & Woods
handsheet former utilizing a single nip felted press and drum dried
to bone dry conditions. Sheet strength was evaluated as tensile
index, STFI, and burst ratio using TAPPI standard methods. Sheet
(basis) weights and apparent sheet densities (calculated from
caliper and basis weight) were evaluated as check on the sheet
making procedure and to ensure that strength comparisons were made
at equal apparent sheet densities.
A. Dry Strength Test Results for Selected AcAm Copolymers
[0066] As shown in Table 2, the structured polymers of this
invention are superior to linear polymer (3*, Table 1) as well as
commercial dry strength additives used in manufacturing of paper
products. Use of these polymers allows for equivalent dry strength
at lower polymer dose compared to currently available dry strength
agents.
[0067] A common theme throughout all the strength tests is that the
structured copolymers demonstrate excellent activity throughout.
Clearly, those polymers in Table 1 exhibiting apparent conformation
coefficients consistent with polymer structuring exhibit dry
strength activity much greater than the linear polymer. Method of
preparation enhanced activity for two copolymers. Both AcAm/DMAEM
copolymers with semi-batch addition of chain transfer agent (8**
& 9**) and the AcAm/DMAPMA copolymer (10**) were structured
polymers which exhibited dry strength activity superior to a
commercial dry strength agent. The two copolymers was added all at
the beginning (4**) did not show this enhanced activity, semi-batch
addition procedure is preferred at least for the AcAm/DMAEM
TABLE-US-00004 TABLE 2 Summary of strength data from structured
polymers of Table 1 Mean Tensile Mean STFI Mean Burst Dose Index
Index (klb.sub.f- Ratio Samples lb/ton (Nm/g) ft/lb) (psi/lb/1000
ft.sup.2) None 0 18.03 4.531 0.676 Commercial agent 4 20.44 5.031
0.989 Commercial agent 8 24.60 5.422 1.336 3 4 19.43 4.743 0.763 3
8 20.40 5.035 0.869 4 4 20.50 4.818 0.895 4 8 21.45 5.067 1.119 5 4
21.62 5.288 1.027 5 8 24.61 5.497 1.201 6 4 20.71 4.771 0.937 6 8
21.71 5.237 1.072 7 4 19.28 4.812 0.756 7 8 18.61 4.765 0.743 8 4
21.96 5.511 1.069 8 8 23.40 5.510 1.243 9 4 21.85 5.300 1.114 9 8
24.11 5.573 1.235 10 4 22.39 5.105 1.143 10 8 25.01 5.757 1.293
[0068] Each aqueous solution of an acrylamide structured polymer
according to the present invention is, as shown in Table 2 have
superior paper strength. These polymers are therefore economically
excellent. When this polymer is used as a paper strength agent, it
can exhibit comparable or better performance compared with
conventional paper strength agents and is evidently excellent
B. Dry Strength Activity for AcAm/DMAPMA and AcAm/DMAPAA
Copolymers, AcAm/DMAPAA/MAA (Monoallylamine) Terpolymer and a
AcAm/DMAPMA/DMAPAA/MAA Tetrapolymer.
[0069] The polymers selected for the expanded evaluation are
described in Table 3. The physical properties of these polymers are
also reported in Table 3. Table 4 shows that all these polymers are
good-performing polymers with apparent conformation coefficients
consistent with polymer structuring, i.e. <0.40. Activity
comparisons are made with commercial strength agents in Table 4,
which were shown to be more active than linear polymers in Table 2.
Additionally, all the SEC recoveries were high indicating good
solubility. TABLE-US-00005 TABLE 3 Structured Acrylamide Polymer
Descriptions Polymer M.sub.w by Composition Conc. SEC/ SEC %
Conformation Sample mole ratio wt % MALLS.sup.a recovery.sup.a
Coefficient.sup.a 11 AcAm/ 14.3 1300,000 98 0.30 DMAPAA/ MAA,
88/10/2 12 AcAm/ 15 2000,000 100 0.28 DMAPMA/ DMAPAA/ MAA, 88/5/5/2
13 AcAm/ 15 1300,000 100 0.37 DMAPAA, 90/10 14 AcAm/ 15 1100,000
100 0.32 DMAPMA 90/10 .sup.abased on dn/dc of polyacrylamide
[0070] TABLE-US-00006 TABLE 4 Tensile Index, STIFI Index and Burst
Ratio data for Structured Acrylamide Polymers Dose, lb/ton
Commercial agent 11 12 13 14 Absolute Tensile Index (Nm/g) 0 21.20
21.20 21.20 21.20 21.20 2 23.43 25.27 24.54 26.49 25.50 4 25.13
29.57 28.91 27.46 27.96 6 27.42 28.68 28.71 29.66 28.60 8 31.47
29.79 32.54 31.92 36.04 Absolute STFI Index (klb.sub.f-ft/lb) 0
5.21 5.21 5.21 5.21 5.21 2 5.49 5.68 5.65 5.53 5.70 4 5.50 6.34
6.55 6.26 6.12 6 5.93 6.23 6.32 6.50 6.19 8 6.24 6.42 6.56 6.62
6.78 Absolute Burst Ratio (psi/lb/1000 ft.sup.2) 0 0.77 0.77 0.77
0.77 0.77 2 0.94 1.09 1.17 1.15 1.13 4 1.02 1.21 1.38 1.35 1.34 6
1.20 1.44 1.57 1.51 1.31 8 1.20 1.51 1.58 1.57 1.31
C. Dry Strength Activity of AcAm Grafted DADMAC/DMAPMA Copolymers
of Example 5
[0071] Dry strength results of structured polymers characterized in
Table 5 are presented in Table 6. Inspection of Table 6 indicates
the DADMAC/DMAPMA grafted with AcAm polymer (21) provides relative
dry strength activity compared to commercial agent, which in turn
was shown to provide greater dry strength activity than
unstructured linear acrylamide polymers. The structured polymers of
the type previously described (15-20) again demonstrated good dry
strength activity, and the best activity was observed with these
types of polymers. These data show that structuring can be achieved
starting with amine containing polymers as well as with amine
containing monomer. TABLE-US-00007 TABLE 5 Structured
Amine-Containing Acrylamide Polymers Polymer M.sub.w by Composition
Conc., SEC/ SEC % Conformation Sample mole ratio wt % MALLS.sup.a
recovery.sup.a Coefficient.sup.a 15 AcAm/ 15 1300,000 100 0.29
DMAPMA 90/10 16 AcAm/ 15 660,000 100 0.38 DMAPMA 90/10 17 AcAm/ 15
1200,000 100 0.27 DMAPMA 95/5 18 AcAm/ 15 1100,000 100 0.30 DMAEM
90/10 19 AcAm/ 15 1000,000 100 0.33 DMAPMA/ DMAEM, 90/5/5 20 AcAm/
15 1300,000 100 0.37 DMAPAA 90/10 21 AcAm/ 10 1900,000 94 0.30
DADMAC/ DMAPMA 70/24/6 .sup.abased on dn/dc of polyacrylamide
[0072] TABLE-US-00008 TABLE 6 Tensile Index, STFI Index, Burst
Ratio Strength Data for Structured AcAm Polymer in Table 5 Dose Ave
Tensile Ave STFI Treatment lb/ton Index Index Ave Burst ratio None
0 19.42 4.925 0.717 Commercial agent 4 22.16 5.491 0.949 21 4 23.65
5.646 1.098 15 4 20.40 5.242 0.838 16 4 23.72 5.443 0.965 18 4
23.98 5.568 0.996 17 4 24.01 5.465 1.003 19 4 24.41 5.774 1.112 20
4 25.89 5.840 1.146 Commercial agent 8 25.82 5.822 1.317 21 8 24.30
5.963 1.390 15 8 23.20 5.679 1.044 16 8 24.10 5.521 1.163 18 8
28.04 6.138 1.166 17 8 25.91 5.833 1.223 19 8 28.18 6.266 1.280 20
8 28.26 6.213 1.281
D. Dry Strength Activity of Structured Amine Polymer Prepared from
Monoallylamine, Diallylamine, and Triallylamine Mixture.
[0073] The polymers in Table 7 were evaluated for their dry
strength activity in the same way as previously described except
that bleached kraft fiber refined in a Valley Beater to 360 mls CSF
(Canadian Standard Freeness) was used. TABLE-US-00009 TABLE 7
Polymers Evaluated in Refined Bleached Kraft Pulp Sample
Composition Polymer Conc., wt % 22 MAA/DAA/TAA 12.2 Initial
Monomer: 72/23/5 mole Monomer Conversion, %: 45/83/94 Polymer
composition: 57.6/34/8.4 mole 23 90/10 mole ratio AcAm/DMAPMA
15.0
[0074] The dry strength results are shown in Table 8. As expected
based on earlier results, the branched AcAm/DMAPMA copolymer (23)
performs very well and demonstrates dry strength activity much
greater than two commercial products. The polyallylamine polymer
(22) also was found to have the same enhanced activity as
structured polymer (23). TABLE-US-00010 TABLE 8 Tensile Index, STFI
Index, Burst Ratio strength data for polymer in Table 7 Dose,
lb/ton Commercial agent 22 23 Tensile Index (Nm/g) 0 47.85 47.85
47.85 3 42.44 56.61 47.11 6 43.86 63.07 52.56 9 48.59 56.09 48.22
STFI Index (klb.sub.f-ft/lb) 0 9.412 9.412 9.412 3 9.379 9.645
9.598 6 9.443 9.949 10.066 9 9.742 9.816 9.751 Burst Ratio
(psi/lb/1000 ft.sup.2) 0 2.796 2.796 2.796 3 3.021 3.351 3.362 6
3.287 3.585 3.505 9 3.563 3.643 3.672
The data shown in Tables 2-8 exemplify the paper strength agent
activity (burst index, Tensile Index and STFI) as identified by the
parameters set forth in the present invention.
* * * * *