Note: Descriptions are shown in the official language in which they were submitted.
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HIGH EFFICIENCY WET STRENGTH RESINS FROM NEW CROSS-LINKERS
FIELD
100011 Embodiments disclosed generally related to strengthening resins. More
particularly, such
embodiments relate to strengthening resins that can include a polyamine
partially cross-linked
with a bridging moiety and having azetidinium ions, where the bridging moiety
can be derived
from a functionally symmetric cross-linker and methods for making and using
same.
BACKGROUND
[0002] Paper is sheet material containing interconnected small, discrete
fibers. The fibers are
usually formed into a sheet on a fine screen from a dilute water suspension or
slurry. Paper
typically is made from cellulose fibers, although occasionally synthetic
fibers are used. Paper
products made from untreated cellulose fibers lose their strength rapidly when
they become wet,
i.e., they have very little "wet strength". Wet strength of ordinary paper is
only about 5% of its
dry strength. The wet strength of paper is defined as the resistance of the
paper to rupture or
disintegration when it is wetted with water. See U.S. Patent No. 5,585,456. To
overcome this
disadvantage, various methods of treating paper products have been employed.
[0003] Wet strength resins applied to paper are either of the "permanent" type
or the "temporary"
type, which are defined by how long the paper retains its wet strength after
immersion in water.
While wet strength retention is a desirable characteristic in packaging
materials, it presents a
disposal problem because paper products having such characteristics are
degradable only under
undesirably severe conditions. Some resins impart temporary wet strength and
are suitable for
sanitary or disposable paper uses; however, these resins often suffer from one
or more
drawbacks. For example, the wet strength of the resins is generally of a low
magnitude (about
one-half of the level achievable for permanent-type resins), the resins can be
easily attacked by
mold and slime, and/or the resins can only be prepared as dilute solutions.
[0004] Conventional resins, which are able to provide permanent wet strength
to paper, typically
are obtained by modifying polyamidoamine polymers such as A, with
epichlorohydrin (B)
("epi") to form polyamidoamine (PAE)-epichlorohydrin resin.
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0
(A) (B)
100051 Conventional resin syntheses capitalize on the difunctional nature of
epichlorohydrin to
use the epoxy and chlorine groups for both cross-linking and generation of
quaternary nitrogen
sites. In these conventional resins, the asymmetric functionality of
epichlorohydrin leads to ring
opening upon reaction of its epoxy group with secondary amines, followed by
the pendant
chlorohydrin moiety either intra-molecularly cyclizing to generate azetidinium
functionality or
inter-molecularly (cross-linking) with another polyamidoamine molecule. Thus,
the first step of
reacting polyamidoamine prepolymer A with epi B occurs with ring-opening of
the epoxy group
by secondary amine groups of the prepolymer backbone at relatively low
temperature. New
functionalized polymer C having chlorohydrin pendant groups is generated, and
this process
typically results in little or no significant change in the prepolymer
molecular weight.
0
CI (C)
100061 The second step involves two competing reactions of the pendant
chlorohydrin groups: 1)
an intramolecular cyclization which generates a cationic azetidinium chloride
functionality, in
which no increase in molecular weight is observed; and 2) an intermolecular
alkylation reaction
to cross-link the polymer, which significantly increases its molecular weight.
The results of both
reactions are illustrated in the PAE-epichlorohydrin resin structure D. In
practice, the alkylation
of epichlorohydrin, the intra-molecular cyclization and the cross-linking
reactions are occurring
simultaneously, but at different rates.
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0
0 OH
0 0
0 H Cie
OH
CI (D)
[0007] The finished wet strength polymer product contains a small amount of
residual pendant
chlorohydrin as illustrated in structure D, and a 3-carbon cross-linked group
with 2-hydroxyl
functionality, with a fairly large amount of quaternary azetidinium chloride
functionality. The
product also can contain substantial amounts of the epichlorohydrin hydrolysis
products 1,3-
DCP, and 3-CPD.
OH OH
a CI
I ,3-dichloro-2-propanol 3-chloropropane-1,2-diol
1,3-DCP 3-CPD
[0008] The relative rates of the three main reactions in this conventional
method, namely the
pendant chlorohydrin formation (ring opening), cyclization to azetidinium ion
groups
(cationization), and cross-linking (intermolecular alkylation), are
approximately 140:4:1,
respectively, when carried out at room temperature. Therefore, the pendant
chlorohydrin groups
form very quickly from ring opening reaction of the epichlorohydrin epoxide
and the secondary
amine in the prepolymer. This first step is performed at lower temperature
(for example, around
25 C to 30 C).
[0009] In the second step, the chlorohydrin groups relatively slowly cyclize
to form cationic
azetidinium groups. Even more slowly, cross-linking occurs, for example, by:
1) a tertiary
amine, for example, of a chlorohydrin pendent group reacting with moiety
secondary amine;
and/or 2) intermolecular alkylation of a tertiary amine with a pendant
chlorohydrin moiety.
[0010] In order to maintain practical utility for minimum reaction cycle
times, the conventional
manufacturing process typically requires that the reaction mixture be heated
to increase the
reaction rates, for example to about 60 C to about 70 C. Usually, reactions
are also carried out
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at high solids content in order to maximize reactor throughput and provide
finished wet strength
resins at the highest solids possible to minimize shipping costs. High
concentration favors the
slower, inter-molecular reaction. Under these high temperature and high
concentration
conditions, the reaction rates between intramolecular cyclization and cross-
linking become
competitive. Thus, one problem encountered in the conventional manufacturing
process is that
the cross-linking reaction rate becomes fast enough that the desired viscosity
end-point
(molecular weight) is achieved at the expense of azetidinium ion group
formation. If the reaction
was allowed to continue beyond the desired viscosity end-point in order to
generate higher levels
of azetidinium groups, the reaction mixture would likely gel and form a solid
mass.
100111 Since both high azetidinium group content and high molecular weights
are useful for
maximum wet strength efficiency of PAE resins, azetidinium group formation and
cross-linking
desirably are maximized without gelling the product or providing a product
that gels during
storage. These conditions, coupled with the desire for high solids to minimize
shipping costs,
have been limiting aspects of the formation of higher efficiency wet strength
resin products.
[0012] There is a need, therefore, for improved strengthening resins, e.g.,
for imparting
appropriate levels of wet strength to paper products, and methods for making
and using same.
SUMMARY
[0013] Strengthening resins and methods for making and using same are
provided. In at least
one example, a strengthening resin can include a polyamine partially cross-
linked with a bridging
moiety and having azetidinium ions. The bridging moiety can be derived from a
functionally
symmetric cross-linker. The functionally symmetric cross-linker can be or
include a
diisocyanate, a 1,3-dialkyldiazetidine-2,4-dione, a dianhydride, a diacyl
halide, a dienone, a
dialkyl halide, or any mixture thereof
[0014] In at least one example, a method for making a strengthening resin can
include reacting a
polyamine and a functionally symmetric cross-linker to produce a partially
cross-linked
polyamine. The functionally symmetric cross-linker can be or include a
diisocyanate, a 1,3-
dialkyldiazetidine-2,4-dione, a dianhydride, a diacyl halide, a dienone, a
dialkyl halide, or any
mixture thereof The partially cross-linked polyamine can be reacted with an
epihalohydrin to
produce a strengthening resin having azetidinium ions.
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100151 In at least one example, a method for strengthening paper can include
contacting fibers
with a strengthening resin. The strengthening resin can be or include a
polyamine partially
cross-linked with a bridging moiety and having azetidinium ions. The bridging
moiety can be
derived from a functionally symmetric cross-linker. The functionally symmetric
cross-liner can
be or include a diisocyanate, a 1,3-dialkyldiazetidine-2,4-dione, a
dianhydride, a diacyl halide, a
dienone, a dialkyl halide, or any mixture thereof.
DETAILED DESCRIPTION
100161 Strengthening resins, e.g., wet strength resins, processes for making
the strengthening
resins, and processes of treating paper to impart strength using the
strengthening resins are
provided. The use of functionally-symmetric ("symmetric") cross-linkers and,
optionally, mono-
functional modifiers and separating into discrete steps the reaction of a
polyamine with the
functionally symmetric cross-linker from the reaction of the partially cross-
linked polyamine
with an epihalohydrin, e.g., epichlorohydrin, new strengthening resins, e.g.,
wet strength resins,
with enhanced properties and/or improved flexibility in the synthesis thereof
are provided. In
addition to providing generally improved wet tensile development over current
technologies, the
products and method can provide higher azetidinium ion content, additional
degrees of reactive
functionalization, maximized molecular weight, and/or good storage stability.
100171 The polyamine cross-linking is distinct from the "cationization"
process of halohydrin-
functionalization and cyclization, a feature that affords substantial
flexibility in tailoring the
degree of cationic functionality, molecular weight, and/or other resin
properties. The
functionally-symmetric cross-linkers and the optional mono-functional
modifiers used to effect
cross-linking and functionalization of the polyamine can be different from the
reagent used to
impart cationic charge to the resin. Specifically, the reaction of the
polyamine with the
functionally symmetric cross-linker can be separate from the reaction of the
partially cross-
linked polyamine with the epihalohydrin. For example, the functionally-
symmetric (or simply
"symmetric") cross-linker can be employed in this first step, which may
provide substantial
control over the cross-linking architecture and properties of the partially
cross-linked
prepolymer, such as a polyamine or polyamidoamine prepolymer. The step of
imparting cationic
charge to the resin, the "cationization" process, can use any epihalohydrin,
e.g., epichlorohydrin
to generate the azetidinium ion functionality.
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100181 The methods for making the strengthening resins can also reduce the
amount of
epichlorohydrin by-products as compared to the amount generally found in
conventional
polyamidoamine-epichlorohydrin strengthening resins that are not prepared by
this process. For
example, the strengthening resins can have substantially reduced levels of 1,3-
dichloro-2-
propanol (1,3-DCP or "DCP") and 3-chloropropane-1,2-diol (3-CPD or "CPD"; also
MCPD for
monochloropropane diol), which generally accompany epichlorohydrin wet
strength resin
synthesis.
100191 In some examples, the method for making the strengthening resin, e.g.,
wet strengthening
resin, can include reacting a polyamine, which may be referred to herein as a
polyamine
prepolymer, with a functionally symmetric cross-linker to produce a partially
cross-linked
polyamine. As such, the polyamine can be partially cross-linked with a
bridging moiety and the
bridging moiety can be derived from the functionally symmetric cross-linker.
An epihalohydrin
can be added to the partially cross-linked polyamine to produce a halohydrin-
functionalized
polymer. The halohydrin-functionalized polymer can be cyclized to form a resin
having
azetidinium moieties. As such, the strengthening resin can be or include the
polyamine partially
cross-linked with the bridging moiety and have azetidium ions or moieties.
100201 If desired, the process can further include reacting the polyamine with
a deficiency of a
mono-functional modifier that includes one secondary amine-reactive moiety. If
the polyamine
is reacted with a deficiency of the mono-functional modifier, the reaction can
occur before,
during, or after the polyamine is reacted with the symmetric cross-linker, or
at different
combinations of these times.
100211 In one example, the polyamine can have the following structure:
H H
N N
w(p)
100221 where R can be alkyl, hydroxyalkyl, amine, amide, aryl, heteroaryl or
cycloalkyl. In
structure P, w can be an integer from 1 to about 10,000. As provided in the
definitions section,
the R groups such as "alkyl" or "hydroxyalkyl" are intended to provide a
convenient description
in which the conventional rules of chemical valence apply; therefore, R of
structure P may be
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described as alkyl or hydroxyalkyl, which is intended to reflect the "R" group
is divalent and
may alternatively be described as alkylene or hydroxyalkylene.
100231 The most widely used and most effective wet strength resin products
generally are
derived from polyamidoamine (PAA) prepolymers reacted with epichlorohydrin, to
form so-
called polyamidoamine-epichlorohydrin (PAE) resins. Therefore, when the
polyamine is or
includes a polyamidoamine prepolymer, it is intended that the resin is not
limited to
polyamidoamine-based systems, but is applicable to any amine-containing
polymer (polyamine)
such as structure P and other amine-containing polymers.
100241 Epichlorohydrin is a difunctional compound having different, hence
"asymmetric",
chemical functionalities, epoxy and chlorine groups. This asymmetric
functionality allows
epichlorohydrin to ring open upon reaction with the epoxy group with secondary
amines,
followed by the pendant chlorohydrin moieties being used for both: 1)
intramolecular cyclization
to generate a cationic azetidinium functionality; or 2) intermolecular cross-
linking the polymer to
increase molecular weight. Epichlorohydrin resin structure D illustrates the
results of both
reactions in a polyamidoamine-epichlorohydrin (PAE) resin.
100251 This disclosure provides for foimulations and processes for making
strengthening resins,
e.g., wet strength resins, with increased levels of cationic charge from
enhanced azetidinium ion
content (greater charge density), additional functionality, optimized or
maximized molecular
weights, high solids contents, and/or lower concentrations of DCP and CPD. In
an aspect, the
disclosed method separates the resin synthesis into two separate and
controllable steps. The first
constructs an intermediate molecular weight, cross-linked prepolymer, prepared
by reacting the
polyamine prepolymer with a functionally-symmetric cross-linker. Unlike the
function of the
asymmetric cross-linker epichlorohydrin, the symmetric cross-linkers of this
disclosure utilize
the same moiety for reaction with both prepolymer secondary amine groups to
effect cross-
linking. If desired, monofunctional groups can be used before, after, or
during the cross-linking
step to impart additional functionality to a prepolymer without the cross-
linking function. The
second step utilizes epichlorohydrin to impart cationic functionality without
it being required for
any cross-linking function, by using a reduced amount of epichlorohydrin to
maximize
azetidinium ion formation on the polymer. This process stands in contrast to
conventional
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practice which is limited by the need to optimize competing azetidinium ion
folination and cross-
linking mechanisms that occur simultaneously.
Polyamine Prepolymer
100261 A range of polyamines (polyamine prepolymers) can be used as a
precursor to the wet
strength resins disclosed herein. The polyamines can be or include primary
and/or secondary
amine moieties that are linked with at least one spacer,
[0027] By way of example, in one aspect, the polyamine, which may be referred
to herein as a
polyamine prepolymer, can have the following structure:
H H
N N
W(p)
[0028] where R can be, for example, alkyl, hydroxyalkyl, amine, amide, aryl,
heteroaryl or
cycloalkyl. In structure P, w can be an integer from 1 to about 10,000, 1 to
about 5,000, 1 to
about 3,000, 1 to about 1,000, 1 to about 100, or 1 to about 10. These "R"
groups, for example
"alkyl", are intended to provide a convenient description of the specified
groups that are derived
from formally removing one or more hydrogen atoms (as needed for the
particular group) from
the parent group. Therefore, the term "alkyl" in structure P would apply the
conventional rules
of chemical valence to apply, but would include, for example, an "alkanediyl
group" which is
formed by formally removing two hydrogen atoms from an alkane (either two
hydrogen atoms
from one carbon atom or one hydrogen atom from two different carbon atoms).
Such an alkyl
group can be substituted or unsubstituted groups, can be acyclic or cyclic
groups, and/or may be
linear or branched unless otherwise specified. A "hydroxyalkyl" group includes
one or more
hydroxyl (OH) moieties substituted on the "alkyl" as defined.
[0029] In this aspect and unless otherwise indicated, R of structure P can be
an alkyl moiety that
is linear (straight chain) or branched. Moiety R can also be a cycloalkyl,
that is, a cyclic
hydrocarbon moiety having from 1 to about 25 carbon atoms. For example, R can
have from 1
to 25, from 1 to 20, from 1 to 15, from 1 to 12, from 1 to 10, from 1 to 8,
from 1 to 6, or from 1
to 4 carbon atoms. Also by way of example, R can have from 2 to 10, 2 to 8, 2
to 6, or 2 to 4
carbon atoms, In a further aspect, R can be a C1 moiety, a C2 moiety, a C3
moiety, a C4 moiety, a
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C5 moiety, a C6 moiety, a C7 moiety, a Cg moiety, a C9 moiety, a Cm moiety, a
C11 moiety, a C12
moiety, a C13 moiety, a C14 moiety, a C15 moiety, a C16 moiety, a C17 moiety,
a Cig moiety, a C19
moiety, a C20 moiety, a C21 moiety, a C22 moiety, a C23 moiety, a C24 moiety,
a C25 moiety, a C26
moiety, a C27 moiety, a C28 moiety, a C29 moiety, a C30 moiety.
[0030] In the polyamine having structure P illustrated supra, R also can be a
poly-primary
amine, such as polyvinyl amine and its copolymers. Examples of a poly-primary
amine that can
constitute R in structure P include, but are not limited to the following
structures, as well as
copolymers with olefins and other unsaturated moieties, where n can be an
integer from 1 to
about 25:
................................ CH2 .. CH- -I's
a
n
H2N
[0031] Alternatively, n can be an integer from 1 to about 20, 1 to about 15, 1
to about 12, 1 to
about 10, or 1 to about 5. In another aspect, n can be 1, 2, 3, 4, 5, 6, 7, 8,
9, 10, 11, 12, 13, 14,
15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25.
[0032] Suitable polyamines (polyamine prepolymers) for use in preparing the
resins of this
disclosure include, but are not limited to, polyalkylene polyamines, such as
polyethylenepolyamines including diethylenetriamine (DETA),
triethylenetetramine (TETA),
aminoethyl piperazine, tetraethylenepentamine,
pentaethylenehexamine, N-(2-
aminoethyl)piperazine, N,N-bi s(2-aminoethyl)-ethyl enedi amine,
diaminoethyl
triaminoethylamine, piperazinethyl triethylenetetramine, and the like. Also
useful in preparing
polyamines for use in the resin preparations of this disclosure include,
ethylene diamine, low
molecular weight polyamidoamines, polyvinylamines, polyethyleneimine (PEI) and
copolymers
of vinyl amine with other unsaturated co-polymerizable monomers such as vinyl
acetate and
vinyl alcohol.
[0033] According to an aspect of polyamine prepolymer P, w is a number range
corresponding
to the polyamine prepolymer Mw mol number from about 2,000 to about 1,000,000.
The Mw
molecular weight of polyamine prepolymer P can also can be from about 5,000 to
about 750,000,
about 7,500 to about 500,000, about 10,000 to about 200,000, about 20,000 to
about 150,000, or
about 30,000 to about 100,000.
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Polyamidoamine Prepolymer
[0034] A range of polyamidoamine prepolymers also can be used as a precursor
to the wet
strength resins according to this disclosure. The polyamidoamine prepolymers
can be made by
the reaction of a polyalkylene polyamine having at least two primary amine
groups and at least
one secondary amine group with a dicarboxylic acid, in a process to form a
long chain polyamide
containing the recurring groups as disclosed herein. In one aspect, the
polyamidoamine
prepolymer can have the following structure:
0 0
HWH (X),
[0035] where RI is (CH2)m where m is 2, 3, 4, or 5; R2 is (CH2)n where n is 2,
3, or 4; w is 1, 2,
or 3; and p is a number range corresponding to the polyamidoamine prepolymer
Mw molecular
weight from about 2,000 to about 1,000,000. The Mw molecular weight also can
be from about
5,000 to about 100,000, about 7,500 to about 80,000, about 10,000 to about
60,000, about 20,000
to about 55,000, or about 30,000 to about 50,000.
[0036] In an aspect, the polyamidoamine prepolymer can have the following
structure:
- 0 0
H 00,
[0037] where R3 is (CH2)q where q is ranging from 0 to 40; and r is a number
range
corresponding to the polyamidoamine prepolymer Mw molecular weight from about
2,000 to
about 1,000,000. Similarly, the Mw molecular weight also can be from about
5,000 to about
100,000, about 7,500 to about 80,000, about 10,000 to about 60,000, about
20,000 to about
55,000, or about 30,000 to about 50,000. Thus, in the structure (CH2)q, q can
also range from 0
to about 40, 0 to about 35, 0 to about 30, 0 to about 25, 0 to about 20, 0 to
about 15, 0 to about
12, 1 to about 40, 1 to about 35, 1 to about 30, 1 to about 25, 1 to about 20,
1 to about 15, 1 to
about 12, 1 to about 10, 1 to about 8, or 1 to about 6.
[0038] In another example, the polyamidoamine prepolymer can have the
following structure:
_____________________________________________________ CJ
(z),
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100391 where n is 1 to 8; p is 2 to 5; and m is 0 to 40, and similar molecular
weight ranges apply.
100401 As disclosed, suitable polyamidoamines are generally prepared by
reacting a dicarboxylic
acid (diacid), or a corresponding dicarboxylic acid halide or diester thereof,
with a polyamine
such as a polyalkylene polyamine. Suitable polyamines include those polyamines
(polyamine
prepolymers) disclosed herein that can be used as precursors for the wet
strength resins
themselves. For example, useful polyamidoamines can be made by reacting
suitable
polyalkylene polyamines, such as polyethylenepolyamines including
ethylenediamine itself,
diethylenetriamine (DETA), triethylenetetramine (TETA), aminoethyl piperazine,
tetraethylenepentamine, pentaethylenehexamine, N-(2-aminoethyl)piperazine, N,N-
bis(2-
aminoethyl)-ethylenediamine, diaminoethyl triaminoethylamine,
piperazinethyl
triethylenetetramine, and the like, with polycarboxylic acids such as
succinic, glutaric, 2-
methylsuccinic, adipic, pimelic, suberic, azelaic, sebacic, undecanedioic,
dodecandioic, 2-
methylglutaric, 3,3-dimethylglutaric and tricarboxypentanes such as 4-
carboxypimelic; alicyclic
saturated acids such as 1,2-cyclohexanedicarboxylic, 1-3-
cyclohexanedicarboxylic, 1,4-
cyclohexanedicarboxylic and 1-3-cyclopentanedicarboxylic; unsaturated
aliphatic acids such as
maleic, fumaric, itaconic, citraconic, mesaconic, aconitic and hexane-3-
diotic; unsaturated
alicyclic acids such as 44-cyclohexenedicarboxylic; aromatic acids such as
phthalic, isophtalic,
terephthalic, 2,3 -naphthal enedi carboxyli c, benzene-1,4-diacetic, and
heteroaliphatic acids such
as diglycolic, thiodiglycolic, dithiodiglycolic, iminodiacetic and
methyliminodiacetic. Usually,
diacids and their related diesters of the formula RO2C(CH2) iiCO2R (where n =
Ito 10 and R ¨
H, methyl, or ethyl) and mixtures thereof are preferred. Adipic acid is
readily available and is
often used.
100411 Other suitable polyamines can include JEFFAMINE polyetheramines,
available from
Huntsman. The JEFFAMINE polyetheramines contain primary amino groups attached
to the
teuninus of a polyether backbone. The polyether backbone is based propylene
oxide (PO),
ethylene oxide (EO), or mixed EO/PO. Other JEFFAMINE products can contain
other
backbone segments and can have varied reactivity provided by hindering the
primary amine or
through secondary amine functionality.
Low molecular weight JEFFAMINES , e.g.,
JEFFAMINE D-230, can be acceptable, as well as higher molecular weight
JEFFAMINES ,
e.g., JEFFAMINE D-2000.
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Symmetric Cross-Linker
100421 Generally, the secondary amines of the polyamines can be reacted with
the one or more
symmetric cross-linkers. In one example, the reaction of the secondary amines
of the polyamine
and the symmetric cross-linker can provides a greater degree of control over
the cross-linking
process, and an intermediate cross-linked prepolymer that has a higher
molecular weight than the
starting prepolymer. The viscosity end-point and thus the molecular weight of
the intermediate
can be easily pre-determined and controlled, at least in part, by the amount
of the symmetric
cross-linker employed. The cross-linking reaction can proceed to an end-point
as the cross-
linker is consumed and stop when consumption of the cross-linker is complete.
A decreased and
measureable amount of secondary amine functionality will remain available for
further
functionalization.
100431 In this cross-linking step, the polyamine can be reacted with a
deficiency of the
symmetric cross-linker, based on the total amount of secondary amines
available for cross-
linking, to provide a partially cross-linked polyamine. Thus, the partially
cross-linked polyamine
has a higher molecular weight than the polyamine, even though it is an
intermediate in the
process and it retains a portion of the secondary amine groups present in the
polyamine. In a
further aspect, the partially cross-linked prepolymer retains a majority of
the secondary amine
groups present in the polyamine, because less than 50% of the stoichiometry
amount of
symmetric cross-linker can be used.
100441 Based on the prepolymer repeating unit having a single secondary amine
subject to
reaction, and the symmetric cross-linker having two reactive moieties, a
stoichiometric reaction
of prepolymer to cross-linker requires a 2:1 molar ratio, and practically, a
2:1 or higher molar
ratio of prepolymer to cross-linker is utilized. In one aspect, the symmetric
cross-linker to
prepolymer molar ratios can be selected to provide more than 0%, but less than
50%, less than
45%, less than 40%, less than 35%, less than 30%, less than 25%, less than
20%, less than 15%,
less than 10%, less than 5%, less than 4%, less than 3%, less than 2%, less
than 1%, less than
0.75%, or less than 0.5% of the stoichiometric ratio of cross-linker to
prepolymer. These values
reflect the combined molar amounts when using more than one symmetric cross-
linker.
100451 The polyamine can be reacted with the symmetric cross-linker in the
presence of water or
in the absence of water. In one example, the polyamine can be reacted with the
symmetric cross-
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linker in an aqueous medium, e.g., water or water containing mixtures. In
another example, the
polyamine can be reacted with the symmetric cross-linker in a non-aqueous
medium, e.g., a non-
aqueous solvent or diluent. In another example, the polyamine can be reacted
with the
symmetric cross-linker in the absence of any other liquid medium whether
aqueous or non-
aqueous. The non-aqueous medium, e.g., solvent or diluent, can be non-reactive
with the
polyamine, the symmetric cross-linker, and/or the partially cross-linked
polyamine. If the
polyamine is reacted with the symmetric cross-linker in a non-aqueous medium
or in the absence
of any other liquid medium to produce the polyamine partially cross-linked
with a bridging
moiety, the polyamine partially cross-linked with a bridging moiety can be
maintained free or
substantially free of any water or can be mixed with water.
[0046] Examples of symmetric cross-linkers can include, but are not limited
to, one or more
diisocyanates, one or more 1,3-dialkyldiazetidine-2,4-diones, one or more
dianhydrides, one or
more diacyl halides, one or more dienones, one or more dialkyl halides, or any
mixture thereof
Other examples of symmetric cross-linkers can include, but are not limited to,
one or more di-
acrylate compounds, one or more a bis(acrylamide) compounds, one or more di-
epoxide
compounds, one or more polyazetidinium compounds, one or more N,N'-methylene-
bis-
methacrylamides, one or more poly(alkylene glycol) diglycidyl ethers, or any
mixture thereof. In
at least one example, the symmetric cross-linker can include at least one of:
(1) a diisocyanate, a
1,3-dialkyldiazetidine-2,4-dione, a dianhydride, a diacyl halide, a dienone,
and a dialkyl halide
and at least one of: (2) a di-acrylate compound, a bis(acrylamide) compound, a
di-epoxide
compound, a polyazetidinium compound, N,N'-methylene-bis-methacrylamide, and a
poly(alkylene glycol) diglycidyl ether.
[0047] The diisocyanate can be unblocked or blocked. Illustrative unblocked
diisocyanates can
include, but are not limited to, 4,4'-methylene diphenyl diisocyanate
(methylene diphenyl
diisocyanate, MDI); toluene-2,4-diisocyanate (toluene diisocyanate, TDI); 1,6-
hexane
diisocyanate (hexamethylene diisocyanate, HDI); 5-i socyanato-1 -(i
socyanatomethyl)- 1 ,3,3 -
trimethyl-cyclohexane (isophorone diisocyanate, IPDI), or any mixture thereof.
Illustrative
blocked diisocyanates can include, but are not limited to, bis-caprolactam
blocked 4,4'-
methylene diphenyl diisocyanate; 4,4'-methylene diphenyl diisocyanate bis(2-
buanone oxime)
adduct, bis-(3,5-dimethylpyrazole) blocked 4,4'-methylene diphenyl
diisocyanate, or any mixture
thereof Commercially available blocked diisocyanates can include, but are not
limited to, the
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TRIXENE(R3 BI products available from Baxenden Chemicals such as TRIXENE BI
7641, 7642,
7674, 7675, 7950, 7951, 7960, 7961, 7963, and 7982, and the RUCO-Guard
products available
from Rudolf Group such as RUCO-Guard XCR, XTN, FX 8011, FX 8021, NET, TIE, and
WEB.
[0048] Illustrative 1,3-dialkyldiazetidine-2,4-diones can include, but are not
limited to, 1,3-
diazetidine-2,4-dione; 1,3-dimethy1-1,3-diazetidine-2,4-dione; 1,3-diethyl-1,3-
diazetidine-2,4-
dione; 1,3-Dipheny1-1,3-diazetidine-2,4-dione; or any mixture thereof.
Illustrative dianhydrides
can include, but are not limited to, pyromellitic dianhydride; ethylene glycol
bis (trimellitic
anhydride); 4,4'-bisphenol A dianhydride, or any mixture thereof. Illustrative
diacyl halides can
include, but are not limited to, oxalyl chloride, oxalyl bromide, succinyl
chloride, benzene-1,2-
dicarbonyl dichloride, benzene-1,2-dicarbonyl bromide, phthaloyl chloride, or
any mixture
thereof Illustrative dienones can include, but are not limited to, 1,7-
octadiene-3,6-dione; bis(2-
propen-1-one)-(1,4-benzene), or any mixture thereof Illustrative dialkyl
halides can include, but
are not limited to, 1,2-dichloroethane; 1,2-dibromoethane; 1,2-diiodoethane;
1,2-
dichloropropane; 1,2-dibromopropane; 1,3-dichloropropane; 1,3-dibromopropane;
1,3-
diiodopropane; 1,4-bis(chloromethyl)benzene; 1,4-bis(bromomethyl)benzene, or
any mixture
thereof
[0049] Other useful symmetric cross-linkers can include, but are not limited
to, any one or more
of the following:
0 0
, where R4 is (CH2)t, and where t is 1, 2, or 3;
0 , where x is from 1 to about 100;
cH3 0 , where y is from 1 to about 100;
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p oH, o
..--'" =-='''''' -A 1:14-
, where x' + y' is from 1 to
about 100; and/or
0
%.,...,..)L
- z
0 , where z is from Ito about 100; including
any
combination thereof.
100501 Specific examples of symmetric cross-linkers can be or include, N,N'-
methylene-bis-
acrylamide, N,N'-methylene-bis-methacrylamide, poly(ethylene glycol)
diglycidyl ether,
poly(propylene glycol) diglycidyl ether, polyethylene glycol diacrylate,
polyazetidinium
compounds, and any combination thereof.
100511 In accordance with a further aspect, the symmetric cross-linker can be
selected from or
can include certain polymers or co-polymers that have a type of functional
moiety that is reactive
with secondary amines, that is, that can function as a symmetric cross-linker
according to this
disclosure. In one aspect, these polymeric symmetric cross-linkers can be
polymers or
copolymers that include azetidinium functional groups. These polymeric
symmetric cross-
linkers can be, for example, copolymers of acrylates, methacrylates, alkenes,
dienes, and the like,
with azetidinium-functionalized monomers such as 1-isopropy1-3-
(methacryloyloxy)-1-
methylazetidinium chloride Q or 1,1-dially1-3-hydroxyazetidinium chloride R,
the structures of
which are illustrated.
H2C.xCH3 V \ 11/
H3C.,...0 Ne Cle
H3C N¨= 0
YCle
CH3 OH
Q R
100521 The polymeric symmetric cross-linkers also can be or can include, for
example,
copolymers of acrylates, methacrylates, alkenes, dienes, and the like, with
other azetidinium-
functionalized monomers such as compounds S, T, or U, as shown here.
CA 02987852 2017-11-29
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:C1430SO2P eff,OSOPIPi
- H
HCI C2 I 3C \C=C}12 C1)4
\c/
0
/ C
II :it 'd 1i3c.
t2
112
[0053] In this aspect, the symmetric cross-linker can be selected from or can
include a
copolymer of an acrylate, a methacrylate, an alkene, or a diene, with an
azetidinium-
functionalized monomer selected from Q, R, S, T, U, and a combination thereof,
where the
fraction of azetidinium-functionalized monomer to acrylate, methacrylate,
alkene, or diene
monomer in the copolymer can be from about 0.1% to about 12%. In a further
aspect, the
fraction of azetidinium-functionalized monomer to acrylate, methacrylate,
alkene, or diene
monomer in the copolymer can be from about 0.2% to about 10%, about 0.2% to
about 10%,
about 0.5% to about 8%, about 0.75% to about 6%, or about 1% to about 5%.
Examples of these
types of symmetric cross-linker polymers and co-polymers can be found in the
following
references: Y.Bogaert, E.Goethals and E.Schacht, Makromol. Chem., 182, 2687-
2693 (1981);
M.Coskun, H.Erten, K.Demirelli and M.Ahmedzade, Polym. Degrad Stab., 69, 245-
249 (2000);
and U.S. Patent Number 5,510,004.
[0054] In accordance with an aspect, the symmetric cross-linker can be
selected from or can
include a minimally azetidinium-functionalized polyamidoamine. That is,
polyamidoamine can
have minimal azetidinium functionalization, which is the reactive moiety in
this type of
symmetric cross-linker. In this case, the cross-linking function is effected
by the azetidinium
moieties, which can react with secondary amines of the polyamidoamine
prepolymer.
Polyamidoamines that are suitable for preparing minimally azetidinium-
functionalized
polyamidoamines are the same general structures and formulas that can be used
for the
preparation of the resin itself, such as structures X, Y, and Z illustrated
herein. An example of a
minimally azetidinium-functionalized polyamidoamine suitable for use as a
symmetric cross-
linker is illustrated in the following structure:
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0
0 e cie
"
0
0
P
OH (X);
100551 where p equal to or greater than 2, the q/p ratio is from about 10 to
about 1000, and the
structure includes at least two azetidinium moieties that function to cross-
link, and that qualify a
structure such as X as a functionally symmetric cross-linker. As the q/p ratio
indicates, there is a
small fraction of azetidinium moieties as compared to acid and amine residues.
Moreover, the
polyamidoamine X also can have the structure where the q/p ratio is from about
12 to about 500,
about 14 to about 400, about 16 to about 300, about 18 to about 200, or about
20 to about 100,
One type of minimally azetidinium-functionalized polyamidoamine is provided
in, for example,
U.S. Patent No. 6,277,242.
100561 As illustrated by the molar ratios of the symmetric cross-linker to the
polyamine, e.g.,
PAE prepolymer, generally, a relatively small fraction of the available
secondary amine sites are
subject to cross-linking to form the branched or partially cross-linked
polyamidoamine
prepolymer. In addition to the molar ratios provided herein, for example, the
symmetric cross-
linker to prepolymer molar ratios can be selected to provide from 0.01% to 5%
of the
stoichiometric ratio of cross-linker to prepolymer. In a further aspect, the
symmetric cross-linker
to prepolymer molar ratios can provide from 0.1% to 4%, 0.2% to 3.5%, 0.3% to
3%, 0.4% to
2.5%, 0.5% to 2%, or 0.6% to 1.5% of the stoichiometric ratio of cross-linker
to prepolymer.
These values reflect the combined molar amounts when using more than one
symmetric cross-
linker.
100571 By way of example, using a polyamidoamine prepolymer derived from
adipic acid and
diethylenetriamine (DETA) as an example, and cross-linking the prepolymer
using methylene-
bis-acrylamide (MBA), the partially cross-linked polyamidoamine prepolymer can
be illustrated
by the following structure:
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0
H
0
Rx
0
N N N
0 (X);
[0058] where the Rx bridging moiety has the structure:
0 0
Rx =
H H
[0059] This illustration does not reflect the use of any mono-functional
modifiers (infra) in
addition to the symmetric cross-linker.
Mono-Functional Modifier
[0060] The secondary amine groups of the polyamines also can be reacted with
one or more
mono-functional compounds to impart any desired chemical functionality to the
prepolymer.
The mono-functional compounds have a reactive group able to react with
secondary or primary
amine and a non-reactive part which can be cationic (to increase the cationic
charge density),
hydrophilic or hydrophobic (to adjust the interaction with non-ionic segments
of the cellulose
fibers). As desired, the polyamine can be reacted with a deficiency of a mono-
functional
modifier that can include one secondary amine-reactive moiety either before,
during, or after, the
step of reacting the polyamine with a deficiency of the symmetric cross-
linker. Further, the
reaction with a stoichiometric deficiency of a mono-functional modifier can
also be carried using
any combination of reaction or addition before, during, or after, reaction
with the symmetric
cross-linker.
[0061] For example, in an aspect, the mono-functional modifier can be selected
from or can
include a neutral or cationic acrylate compound, a neutral or cationic
acrylamide compound, an
acrylonitrile compound, a mono-epoxide compound, or any combination thereof.
According to a
further aspect, the mono-functional modifier can be selected from or can
include an alkyl
acrylate, acrylamide, an alkyl acrylamide, a dialkyl acrylamide,
acrylonitrile, a 2-alkyl oxirane, a
2-(allyloxyalkyl)oxirane, a hydroxyalkyl acrylate, an co -(acryloyloxy)-
alkyltrimethylammonium
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compound, an w-(acrylamido)-alkyltrimethylammonium compound, and any
combination
thereof Examples of mono-functional modifiers are illustrated below.
0 9
p
\
H2CH ,...,0 CH H
4 CH¨s< ,,
' \"r''' C'''
H2C NH2 iH2CN 2
-- , -R "==14
/
6õ
ii
\R
H2C=CH H2C=CH H2C¨CH1
\>==0 H2C=CH \ /
\ \-= .. ,, 0 4,t
d
/ ......................................
d F=0
\ HN
,CH2 d \ ,,,,, 2
i cli
H2C \pH' $ ,
H2C----CH \00'"
\ ..
H2C i \ \ $
µcH2 H2C .................. +,õ cH3 0
OH H3C \.,
--, CH3
H3µ..
rt., CH3
100621 For example, the mono-functional modifier can be or include at least
one of: methyl
acrylate; alkyl acrylate; acrylamide; N-methylacrylamide; N,N-
dimethylacrylamide;
acrylonitrile; 2-methyloxirane; 2-ethyloxirane; 2-propyloxirane; 2-
(allyloxymethyl)oxirane; 2-
hydroxyethyl acrylate; 2-(2-hydroxyethoxy)ethyl acrylate; 2-(acryloyloxy)-
N,N,N-
trimethylethanaminium; 3-(acryloyloxy)-N,N,N-trimethylpropan-1-aminium; 2-
acrylamido-
N,N,N-trimethylethanaminium; 3-acrylamido-N,N,N-trimethylpropan-1-aminium; and
1-
isopropy1-3-(methacryloyloxy)-1-methylazetidinium chloride. Depending upon the
structure of
the modifier, it is seen that upon reaction of these compounds with secondary
or primary amine,
the portion that is non-reactive toward the amine can impart cationic charge
to assist in
increasing the cationic charge density, can alter the hydrophilic or
hydrophobic characteristics,
for example to adjust the interaction with non-ionic segments of the cellulose
fibers, and/or can
affect other properties of the resulting intermediate cross-linked prepolymer.
100631 The mono-functional modifier can be reacted with the polyamine in an
amount from a
low of about 0.0001 moles, about 0.0005 moles, about 0.001 moles, about 0.005
moles, or about
0.01 moles to a high of about 0.05 moles, about 0.07 moles, about 0.1 moles,
about 0.15 moles,
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or about 0.2 moles per mole of secondary amine groups. For example, the mono-
functional
modifier can be reacted with the secondary amine groups of the polyamine in an
amount of about
0.0001 moles to about 0.1 moles per mole of the secondary amine groups.
Halohydrin-Functionalized Polymer and Intramolecular Cyclization
100641 Generally, by separating into discrete steps the reaction of the
polyamine with the cross-
linkers from the reaction of the intermediate cross-linked prepolymer with the
epichlorohydrin,
the second reaction step requires less epichlorohydrin than conventional
methods to reach the
desired end-point. Further, this second reaction step can be effected under
reaction conditions
which favor optimized azetidinium group formation over further cross-linking.
The asymmetric
functionality of epichlorohydrin is useful in this functionalization to allow
a relatively facile
reaction of the epoxy group with secondary amines to form a pendant
chlorohydrin moiety,
followed by an intramolecular cyclization of the pendant chlorohydrin to
generate a cationic
azetidinium functionality. This latter intramolecular cyclization can utilize
heating of the
halohydrin-functionalized polymer.
100651 In an aspect, the second reaction step can be carried out using any
epihalohydrin, such as
epichlorohydrin, epibromohydrin, and epiiodohydrin, or any combination
thereof. For example,
epichlorohydrin can be used. When reciting epichlorohydrin in this disclosure,
such as in
structures or reaction schemes, it is understood that any of the
epihalohydrins can be used in the
process.
100661 By way of example, using the partially cross-linked polyamidoamine
prepolymer
illustrated supra that was derived from adipic acid and DETA and cross-linking
using MBA, the
epichlorohydrin functionalization product can illustrated by the following
structure, termed a
"halohydrin-functionalized polymer."
CA 02987852 2017-11-29
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CI
OH
CI
0
N
0
Rx
0
H
0
(Y)
[0067] As before, this illustration does not reflect the use of any mono-
functional modifiers in
addition to the symmetric cross-linker. The reaction of epihalohydrins such as
epichlorohydrin is
generally tailored to consume a high percentage or the remaining secondary
amine moieties in
generating the halohydrin-functionalized polymer, in this case, a chlorohydrin-
functionalized
polymer.
[0068] The formation of the halohydrin-functionalized polymer can be carried
out using a range
of epichlorohydrin molar ratios. For example, this reaction can be carried out
using an excess of
epichlorohydrin. The stoichiometric reaction of epichlorohydrin with a
secondary amine group
requires a 1:1 molar ratio of epichlorohydrin with a secondary amine. In an
aspect, from about
0.8 mole to about 3 moles of epichlorohydrin per mole of secondary amine can
be used.
Alternatively, from about 0.9 mole to about 2.5 moles of epichlorohydrin per
mole of secondary
amine, about 1.0 mole to about 2.0 moles, about 1.1 mole to about 1.7 moles,
about 1.2 mole to
about 1.5 moles, about 1.25 mole to about 1.45 moles of epichlorohydrin per
mole of secondary
amine can be used. For example, the moles of moles of epichlorohydrin per mole
of secondary
amine can be about 0.8, about 0.9, about 1.0, about 1.1, about 1.2, about 1.3,
about 1.4, about
1.5, or about 1.6.
[0069] The amount of the symmetric cross-linker and epihalohydrin can be
sufficient to produce
a strengthening resin that can have substantially no secondary amine groups.
This result can be
effected by using the molar amounts and ratios disclosed herein, but resin
compositions prepared
by this disclosure can include substantially no secondary amine groups even
when molar
amounts and ratios outside those recited are used. By substantially no
secondary amine groups,
it is intended to mean that less than 10% of the original secondary amines in
the starting PAE
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resin prior to the cross-linking, functionalization, and cationization
reactions remain.
Alternatively, less than 5%, less than 2%, less than 1%, less than 0.5%, less
than 0.2%, less than
0.1%, less than 0.01%, less than 0.005%, or less than 0.001% of the original
secondary amines in
the starting PAE resin can remain.
100701 The halohydrin (typically chlorohydrin)-functionalized polymer can be
converted to a
wet-strength resin by subjecting the polymer to cyclization conditions to form
azetidinium ions.
The functionalized polymer can be heated to form the azetidinium ions. In
contrast to the
conventional method in which heating induces both cross-linking and
cyclization, the cross-
linking portion of this process is complete when the cyclization is carried
out, thereby affording
greater process control and the ability to more closely tailor the desired
properties of the
resulting resin. Also in contrast to the conventional method, the processes
discussed and
described herein can reduce and/or minimize the formation of the
epichlorohydrin by-products
1,3-dichloro-2-propanol (1,3-DCP or "DCP") and 3-chloropropane-1,2-diol (3-CPD
or "CPD")
remaining in the resin can be reduced or minimized.
100711 The concentration of epichlorohydrin 1,3-dichloro-2-propanol (1,3-DCP)
remaining in
the strengthening resin at 25% solids (DCP @ 25%) can be less than about
15,000 ppm, less than
about 14,000 ppm, less than about 13,000 ppm, less than about 12,000 ppm, less
than about
11,500 ppm, less than about 11,000 ppm, less than about 10,500 ppm, less than
about 10,000
ppm, less than about 8,000 ppm, less than about 6,000 ppm, or less than about
5,000 ppm.
100721 The following resin composition structure Z illustrates the results of
the cyclization step
to form the quaternary nitrogen ("cationization") based on the chlorohydrin-
functionalized
polymer Y shown supra, which has been subjected to conditions sufficient to
intramolecularly
cyclize the pendant chlorohydrin to impart azetidinium functionality.
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OH
0
9
CI 0
R-
0
4, IR] e cP
H N N NH
(11) 0
OH (Z)
100731 In the process for forming the resin compositions, the resin
composition is generated by
subjecting the halohydrin-functionalized polymer to cyclization conditions
sufficient to convert
the halohydrin groups to form azetidinium ions. At least a portion of the
halohydrin groups can
be cyclized to form azetidinium ions or moieties. In one example, at least 90%
of the halohydrin
groups can be cyclized to form azetidinium ions. Alternatively, at least 95%,
at least 97%, at
least 98%, at least 98.5%, at least 99%, at least 99.5%, at least 99.7%, at
least 99.8%, or at least
99.9% of the halohydrin groups can be cyclized to form azetidinium ions.
100741 Additional steps in the resin processing can be used, for example, to
adjust the solids
content of the composition, beyond those described in detail above. For
example, the resin
composition can be generated by converting the halohydrin-functionalized
polymer to an
azetidinium functionalized polymer. Following this step, the pH polymer
composition can be
adjusted such that the pH of the resin composition can be from about 2 to
about 4.5.
Alternatively, the pH of the resin can be from about 2.2 to about 4.2, about
2.5 to about 4, or
about 2.7 to about 3.7. In another example, the pH of the polymer composition
can be adjusted
to a pH from a low of about 2, about 2.1, about 2.2, about 2.3, about 2.4,
about 2.5, about 2.6, or
about 2.7 to a high of about 3, about 3.2, about 3.4, about 3.6, about 2.8,
about 4, about 4.2, or
about 4.5, when measured at a temperature of about 25 C. This pH adjustment
step also may be
followed by the step of adjusting the solids content of the composition from
about 10% to about
50% to form the strengthening resin. Alternatively, the solids content of the
composition can be
adjusted from about 15% to about 40% or about 20% to about 30% to form the
strengthening
resin. In another example, the strengthening resin can have a solids content
of about 25%.
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[0075] The resulting strengthening resin can have a charge density that is
enhanced over that of
conventional resins. For example, the strengthening resin can have a charge
density of about 2 to
about 4 mEq/g of solids. Alternatively, the strengthening resin can have a
charge density from
about 2.25 to about 3.5 mEq/g of solids, about 2.3 to about 3.35 mEq/g of
solids, about 2.4 to
about 3.2 mEq/g of solids, or about 2.5 to about 3.0 mEq/g of solids.
[0076] The resulting strengthening resin also can have a ratio of azetidinium
ions to amine
residues in the strengthening resin, which we abbreviate by "Azet", from about
0.4 to about 2.3.
The Azet ratio also can be from about 0.5 to about 1.9, about 0.6 to about
1.6, or about 0.7 to
about 1.3. In another example, the ratio of azetidinium ions to secondary
amine moieties in the
resin can be from about 0.4 to about 1. The Azet ratio can be measured by
quantitative 13C NMR
by comparing the methylene carbons of the azetidinium versus the methylenes of
the acid residue
in the backbone.
[0077] In another example the strengthening resin can have a Mw molecular
weight from about
0.02 x 106 to about 3.0 x 106. Alternatively, the resins that can have a Mw
molecular weight
from about 0.05 x 106 to about 2.5 x 106, about 0.1 x 106 to about 2.0 x 106,
about 0.5 x 106 to
about 1.5 x 106, or about 1 x 106 to about 1.0 x 106. In another example, the
resin that can have
a Mw molecular weight from about 0.05 x 106 to about 1.7 x 106. The Mw
molecular weight
also can be from about 0.6 x 106 to about 1.6 x 106, about 0.7 x 106 to about
1.5 x 106, about 0.8
x 106 to about 1.3 x 106, or about 0.9 x 106 to about 1.1 x 106.
[0078] The strengthening resin can have an azetidinium equivalent weight,
defined as the degree
of polymerization multiplied times the Azet ratio, or (degree of
polymerization)x(Azet), of from
about 1,600 to about 3,800. Alternatively, the azetidinium equivalent weight
can be from about
1,800 to about 3,500, or about 2,000 to about 2,900.
[0079] The strengthening resin can also possess various combinations of the
disclosed
properties. For example, the strengthening resin can exhibit or possess at
least two, at least three,
at least four, or at least five of the disclosed properties of charge density,
Azet ratio, Mw
molecular weight, azetidinium equivalent weight, 1,3-DCP content, halohydrin
groups are
cyclized to form azetidinium ions, and the like. For example, the
strengthening resin can exhibit
or possess at least two, at least three, at least four, or all five of the
following characteristic
features: (a) a charge density of about 2.25 to about 3.5 mEq/g of solids; (b)
a ratio of
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CA 02987852 2017-11-29
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azetidinium ions to amide residues in the strengthening resin is from about
0.7 to about 0.9; (c) a
Mw molecular weight from about 0.05 x 106 to about 1.5 x 106; (d) an
azetidinium equivalent
weight of from about 1,800 to about 3,500; and (e) a 1,3-dichloro-2-propanol
(1,3-DCP) content
of less than about 10,000 ppm when the solids content is about 25%.
Comparison with Conventional Wet Strength Resin Systems
[0080] As described for the conventional wet strength resin preparation, the
relative rates of the
three main reactions in this conventional method, namely the pendant
chlorohydrin formation
(ring opening), cyclization to azetidinium ion groups (cationization), and
cross-linking
(intermolecular alkylation), are approximately 140:4:1, respectively, when
carried out at room
temperature. Therefore, the pendant chlorohydrin groups form very quickly from
ring opening
reaction of the epichlorohydrin epoxide and the secondary amine in the
prepolymer using about a
1:1 molar ratio of epichlorohydrin to secondary amine. The chlorohydrin groups
then relatively
slowly cyclize to form cationic azetidinium groups. Even more slowly, cross-
linking occurs, for
example, by: 1) a tertiary amine, for example, of a chlorohydrin pendent group
reacting with an
azetidinium moiety; and/or 2) intermolecular alkylation of a tertiary amine
with a pendant
chlorohydrin moiety. Thus, at the cross-linking stage in the reaction scheme,
there are
substantially no remaining secondary amine groups. Cross-linking results in an
increase in
molecular weight, which is manifested in the increase in resin viscosity.
[0081] In order to maintain practical utility for minimum reaction cycle
times, the manufacturing
process can be carried out under high temperature and high concentration
conditions, where the
reaction rates between intramolecular cyclization and cross-linking become
competitive. Thus,
one problem encountered in the conventional manufacturing process is that the
cross-linking
reaction rate becomes fast enough that the desired viscosity end-point
(molecular weight) is
achieved at the expense of azetidinium ion group formation. If the reaction
was allowed to
continue beyond the desired viscosity end-point in order to generate higher
levels of azetidinium
groups, the reaction mixture would likely gel and form a solid mass.
[0082] Since both high azetidinium group content and high molecular weights
are useful for
maximum wet strength efficiency of PAE resins, azetidinium group formation and
cross-linking
desirably are maximized without gelling the product or providing a product
that gels during
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storage. These conditions, coupled with the desire for high solids to minimize
shipping costs,
have been limiting aspects of the formation of higher efficiency wet strength
resin products.
100831 In contrast, the strengthening resins and processes discussed and
described herein at least
partially address this issue by providing higher azetidinium ion content,
additional degrees of
reactive functionalization, increased molecular weight, and very good storage
stability. The
strengthening resins provide improved wet tensile development over current
technologies when
used in paper, paperboard, tissue and towel applications.
100841 A comparison of wet strength resin properties with standard
commercially available wet
strength resins is provided in the Examples and Tables. The wet strength resin
properties of the
resin prepared according to this disclosure were examined and compared to
standard
commercially available wet strength resin products, including the AA/TRES
series (Georgia-
Pacific) of resins and the KYMENE (Ashland) resins. Both properties of the
resins themselves
and the performance of the resins for imparting wet strength are compared in
the following
tables. The data illustrate (Table 1) significant improvements in resin
properties such as
increased charge density, higher proportion of azetidinium ions to amide
residues, higher
molecular weight, greater azetidinium equivalent weight, and lower byproduct
contaminant were
observed in the disclosed resins as compared to conventional resins.
100851 According to another aspect, there is provided a strengthening resin
for enhancing the wet
strength of paper. A method for preparing the resin or resin composition can
include reacting a
polyamine with a symmetric cross-linker to produce a partially cross-linked
polyamine. An
epihalohydrin can be added to the partially cross-linked polyamine to produce
a halohydrin-
functionalized polymer. The halohydrin-functionalized polymer can be cyclized
to form the
resin having azetidinium moieties.
100861 When the polyamine (polyamine prepolymer) is selected from a
polyamidoamine
prepolymer, a further aspect of this disclosure provides a resin for enhancing
the strength, e.g.,
wet strength, of paper, where the resin includes a polyamidoamine polymer that
is crosslinked
with a bridging moiety derived from the functionally symmetric cross-linker
and has azetidinium
ions. A method for preparing the resin or resin composition can include
reacting a
polyamidoamine (PAA) prepolymer having secondary amine groups with a
deficiency of a
symmetric cross-linker having secondary amine-reactive moieties to provide a
partially cross-
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linked polyamidoamine prepolymer that retains a portion, e.g., a majority, of
the secondary
amine groups present in the polyamidoamine prepolymer. If desired, the
polyamidoamine
prepolymer can be reacted with a deficiency of a mono-functional modifier that
can include one
secondary amine-reactive moiety before, during, or after reaction with the
symmetric cross-
linker. The partially cross-linked polyamidoamine prepolymer can be reacted
with an
epihalohydrin to provide a halohydrin-functionalized polymer. A resin
composition can be
formed by subjecting the halohydrin-functionalized polymer to conditions
sufficient to cyclize at
least a portion of the halohydrin groups to form azetidinium ions.
[0087] Any paper strengthened with the strengthening resin is also an aspect
of this disclosure
and provided for herein. Moreover, a process for treating paper to impart wet
strength, can
include treating fibers used to make the paper with dry resin solids, where
the resin is any resin
in the present disclosure. For example, the process can include treating
fibers used to make a
paper with from about 0.05% to about 2 % by weight dry resin solids based on
the dry weight of
the fibers of a cationic thermosetting resin or resin composition, in which
the resin or resin
composition is made in accordance with this disclosure. The process for
treating paper to impart
wet strength can include treating fibers used to make a paper with from about
0.01% to about 2
% by weight dry resin solids based on the dry weight of the fibers of a
cationic thermosetting
resin composition. Alternatively, the process can employ from about 0.05% to
about 1.8 % by
weight, about 0.075% to about 1.6 % by weight, or about 0.1% to about 1.5 % by
weight dry
resin solids based on the dry weight of the fibers. The fibers can be pulp
fibers.
[0088] Although each resin composition property disclosed herein is explained
in detail
independent of other properties, it is intended that any resin composition
property can occur with
any other resin property or properties in the disclosed resins. For example,
and not as a
limitation, the disclosure of the properties herein encompasses a composition
that can have at
least one, at least two, at least three, at least four, or at least five of
the following properties: a) a
charge density of about 1.0 to about 4.0 mEq/g of solids; b) a ratio of
azetidinium ions to amide
residues in the resin is from about 0.5 to about 0.9.; c) a molecular weight
from about 0.05 x 106
to about 3.0 x 106; d) an azetidinium equivalent weight of from about 1,800 to
about 3,500; and
e) a 1,3-dichloro-2-propanol (1,3-DCP) content of less than about 10,000 ppm
when the solids
content is about 25%.
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[0089] To define more clearly the terms used herein, the following definitions
are provided,
which are applicable to this disclosure unless otherwise indicated, as long as
the definition does
not render indefinite or non-enabled any claim to which that definition is
applied, for example,
by failing to adhere to the conventional rules of chemical valence. If a term
is used in this
disclosure but is not specifically defined herein, the definition from the
IUPAC Compendium of
Chemical Terminology, 2"d Ed (1997) can be applied, as long as that definition
does not conflict
with any other disclosure or definition applied herein, or render indefinite
or non-enabled any
claim to which that definition is applied. To the extent that any definition
or usage provided by
any document incorporated herein by reference conflicts with the definition or
usage provided
herein, the definition or usage provided herein controls.
[0090] While compositions and methods are described in terms of "comprising"
various
components or steps, the compositions and methods can also "consist
essentially of' or "consist
of' the various components or steps.
[0091] Unless otherwise specified, any carbon-containing group for which the
number of carbon
atoms is not specified can have, according to proper chemical practice, 1, 2,
3, 4, 5, 6, 7, 8, 9, 110,
11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or
30 carbon atoms, or
any range or combination of ranges between these values. For example, unless
otherwise
specified, any carbon-containing group can have from 1 to 30 carbon atoms,
from 1 to 25 carbon
atoms, from 1 to 20 carbon atoms, from 1 to 15 carbon atoms, from 1 to 10
carbon atoms, or
from 1 to 5 carbon atoms, and the like. Moreover, other identifiers or
qualifying terms may be
utilized to indicate the presence or absence of a particular substituent, a
particular regiochemistry
and/or stereochemistry, or the presence of absence of a branched underlying
structure or
backbone.
[0092] The term "substituted" when used to describe a group, for example, when
referring to a
substituted analog of a particular group, is intended to describe any non-
hydrogen moiety that
formally replaces a hydrogen in that group, and is intended to be non-
limiting. However,
applicants reserve the right to proviso out any group, for example, to limit
the scope of any claim
to account for a prior disclosure of which Applicants may be unaware. A group
or group may
also be referred to herein as "unsubstituted" or by equivalent tel ___________
ins such as "non-substituted,"
which refers to the original group in which a non-hydrogen moiety does not
replace a hydrogen
28
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within that group. "Substituted" is intended to be non-limiting and include
inorganic substituents
or organic substituents as specified and as understood by one of ordinary
skill in the art.
100931 The term "alkyl group" as used herein is a general term that refers to
a group formed by
removing one or more hydrogen atoms (as needed for the particular group) from
an alkane.
Therefore, an "alkyl group" includes the definition specified by IUPAC of a
univalent group
formed by formally removing a hydrogen atom from an alkane but also includes,
for example, an
"alkanediyl group" which is formed by formally removing two hydrogen atoms
from an alkane
(either two hydrogen atoms from one carbon atom or one hydrogen atom from two
different
carbon atoms) when the context requires or allows, as long as the usual rules
of chemical valence
are applied. An alkyl group can be substituted or unsubstituted groups, can be
acyclic or cyclic
groups, and/or may be linear or branched unless otherwise specified.
100941 The term "cycloalkyl group" as used herein is a general term that
refers to a group formed
by removing one or more hydrogen atoms (as needed for the particular group)
from a
cycloalkane. Therefore, an "cycloalkyl group" includes the definition
specified by IUPAC of a
univalent group formed by formally removing a hydrogen atom from an
cycloalkane but also
includes, for example, an "cycloalkanediyl group" which is formed by formally
removing two
hydrogen atoms from an alkane (either two hydrogen atoms from one carbon atom
or one
hydrogen atom from two different carbon atoms) when the context requires or
allows, as long as
the usual rules of chemical valence are applied. An alkyl group can be
substituted or
unsubstituted groups, can be acyclic or cyclic groups, and/or may be linear or
branched unless
otherwise specified. When two hydrogens are formally removed from cycloalkane
to form a
"cycloalkyl" group, the two hydrogen atoms can be formally removed from the
same ring
carbon, from two different ring carbons, or from one ring carbon and one
carbon atom that is not
a ring carbon.
100951 An "aryl group" refers to a group formed by removing one or more
hydrogen atoms (as
needed for the particular group and at least one of which is an aromatic ring
carbon atom) from
an aromatic compound, specifically, an arene. Therefore, an "aryl group"
includes a univalent
group formed by formally removing a hydrogen atom from an arene, but also
includes, for
example, an "arenediyl group" arising from formally removing two hydrogen
atoms (at least one
of which is from an aromatic hydrocarbon ring carbon) from an arene. Thus, an
aromatic
29
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compound is compound containing a cyclically conjugated hydrocarbon that
follows the Hiickel
(4n+2) rule and containing (4n+2) pi-electrons, where n is an integer from 1
to about 5.
Therefore, aromatic compounds and hence "aryl groups" may be monocyclic or
polycyclic unless
otherwise specified.
100961 A "heteroaryl group" refers to a group formed by removing one or more
hydrogen atoms
(as needed for the particular group and at least one of which is an aromatic
ring carbon or
heteroatom) from an heteroaromatic compound. Therefore, the one or more
hydrogen atom can
be removed from a ring carbon atom and/or from a heteroaromatic ring or ring
system
heteroatom. Thus, a "heteroaryl" group or moiety includes a "heteroarenediyl
group" which
arises by formally removing two hydrogen atoms from a heteroarene compound, at
least one of
which can be a heteroarene ring or ring system carbon atom. Thus, in a
"heteroarenediyl group,"
at least one hydrogen is removed from a heteroarene ring or ring system carbon
atom, and the
other hydrogen atom can be removed from any other carbon atom, including for
example, a
heteroarene ring or ring system carbon atom, or a non-heteroarene ring or ring
system atom.
100971 An "amide" group or moiety refers to a group formed by removing one or
more hydrogen
atoms (as needed for the particular group) from an amide compound, including
an organic amide
compound. Therefore, the one or more hydrogen atom can be removed from a
carboxyl group
carbon, from an amide nitrogen, from any organic moiety bonded to either the
carboxyl group
carbon or the amide nitrogen, or from an organic moiety bonded to the carboxyl
group carbon
and an organic moiety bonded to the amide nitrogen. Often, for example, when
an amide group
links amines in a polyamine, the "amide" group or moiety arises from foimally
removing a
hydrogen atom from each of two organic groups, one bonded to the carboxyl
group and the other
to the amide nitrogen. This term can be used for any amide moiety, whether the
organic groups
of the amide or aliphatic or aromatic.
100981 The use of various substituted analogs or formal derivatives of any of
these groups may
also be disclosed, in which case the analog or formal derivative is not
limited to the number of
substituents or a particular regiochemistry, unless otherwise indicated. For
example, the term
"hydroxyalkyl" refers to a group formed by formally removing one or more
hydrogen atoms (as
needed for the particular group) from the alkyl portion of a hydroxy-
substituted alkane. The
hydroxy-substituted alkane can include one or more hydroxy substituents.
Therefore, a
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"hydroxyalkyl" group includes, for example, a hydroxy-substituted "alkanediyl"
group which is
formed by formally removing two hydrogen atoms from a "hydroxyalkyl" alkane
(either two
hydrogen atoms from one carbon atom or one hydrogen atom from two different
carbon atoms)
when the context requires or allows, as long as the usual rules of chemical
valence are applied.
As indicated for an alkyl group, the alkyl group can be substituted or
unsubstituted groups, can
be acyclic or cyclic groups, and/or may be linear or branched unless otherwise
specified.
100991 The synthesis of standard PAE wet strength resin using adipic acid and
DETA with
epichlorohydrin is shown in Scheme 1. The resin according one or more
embodiments discussed
and described herein using the symmetric cross-linker, methylene bis-
acrylamide (MBA), is
shown in Scheme 2.
0 9
. = ,NFI, 1. Water 0
= =:( 'NH
.CI
2. Epichlorohydrin ,
Prepolymer sr¨OH
3. Exotherm / Cooling
Holde30 C a
1. VVater, 2. Heat, 60.- 65 C 9 Ci -
3. React to Visc Endpoint
\
4. Acicify, 5. Dilute 0
\
"OH
OH
9
\ OH
= /
\
=,/ NZN 714Z1-===,' a ,A.= ,a DCP
.
+ _
-
0
OH
CI .0H CPD
'Cl
Scheme 1
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PCT/US2016/034884
00 0 9
Step #1
NH NH 'NH NH NH
-
9 o
Prepolymer Mw ¨ 40,000 - 50,000 MBA
R1 = (CH)4 Adipic NH NH 'NH
R2= (CH), Glutaric
intermediate cross-linked prepolymer
9 9 9 9
. .
R3 NH NH Step #2
Epichlorohydrin
MBA:= methylene-bis-acrylamide
1.35 Mole / Sec Amine
õCI
HO
OH
o 0 9
N N N . .
NH Ml R Ml NH NH NH R NH NH
o 9
9
N
- "OH
CI
OH intra-molecular cydization pendant chlorohydrin
azetidinium ion
Scheme 2
13C NMR Determination of Azetidinium Ratio in Wet Strength Resins (Azet Ratio)
1001001 The azetidinium ratio, or "Azet" ratio, is the ratio of the polymer
segments containing
azetidinium ion to the total number of polymer segments. A single polymer
segment is defined
by a condensation moiety derived from one diacid molecule (for example, adipic
acid) and one
triamine molecule (for example, diethylenetriamine or DETA), illustrated
below.
OH
0
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[00101] The azetidinium ion ratio is determined by quantitative (inverse gated
heteronuclear
decoupled) '3C NMR spectroscopy, using a relaxation time of 22.5 seconds,
spectral width of
15000 flz (240 ppm) and from 320 to 1024 scans. Measurements were made by
integration of
the methylene peaks in the azetidinium ion and the inner carbons of the adipic
acid portion of the
polymer. The adipic acid portion is assigned to be the total number of polymer
segments. Thus
when the polymer is prepared using adipic acid, the azetidinium ratio is
determined according to
the formula:
Azetidinium Ion Ratio (Azet Ratio) = A(azet) / A(adip), where,
[00102] A(azet) is the integrated area of methylenes from azetidinium ions;
and A(adip) is the
integrated area of methylenes from adipic moiety (total polymer segments).
This method can be
adapted to any resin disclosed herein. Thus, for Adipic Acid based polymers
the azetidinium ion
peak at 74 ppm and the backbone methylene peak at 25 ppm were both integrated
and the
methylene peak at 25 ppm was normalized to 1. For glutaric Acid based
polymers, the
azetidinium ion peak at 74 ppm and the backbone methylene peak at 22 ppm were
both
integrated and the methylene peak at 22 ppm was normalized to 1.
Charge Density of Wet Strength Resins
[00103] The charge density of cationic polyamidoamine-epichlorohydrin (PAE)
wet strength
resins with a typical non-volatile content of about 10% to about 50% were
measured using a
Matek (Muetek) PCD-03 Particle Charge Detector and Titrator as follows. Charge
density was
determined by measuring the streaming current potential of a dilute solution
of the polycationic
resin by titration with a polyanionic solution of polyvinyl sulfate (PVSK).
The non-volatile
content of the PAE resin was predetermined, and the charge density in
milliequivalents (+) per
gram of solids (meq+/g) are reported.
[00104] Under the action of van der Waal forces, the polycationic resin is
preferentially adsorbed
at the surface of the test cell and its oscillating displacement piston, and
as a diffuse cloud of
counter-ions is sheared off the cationic colloids by the liquid flow in the
test cell, a so-called
streaming current is induced. Electrodes in the test cell wall measure this
streaming current. The
PAE resins are titrated with PVSK until the PAE resin reaches the point of
zero charge, and the
original resin charge is calculated from the titrant consumption. The
streaming current is used to
calculate the milliequivalents of cationic charge per gram solid resin
(meq+/gram) as follows:
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PVSK (mL) * PVSK(N) meq +
Charge Density ¨
GramActive Re sin gram
Preparation of Sheets
[00105] The pulp stock used in the handsheet work was unique for each study,
as indicated in
Tables 2, 3, and 4. The resins were added at the lb/ton of pulp solids
indicated in the tables to
the diluted stock consistency indicated in the respective tables (Thick Stock
%), allowing a 2-
minute mixing time. The treated stock was immediately poured into the headbox
of the Noble &
Wood handsheet machine containing pH pre-adjusted water (pH of 7.0). The
target sheet basis
weight was 30 lb/3000 ft2. Each wet sheet was given two passes through the
full load wet press,
and then placed on the 105 C drum dryer without the blotter for 1 minute. All
sets of handsheets
were further cured for 10 minutes at 105 C in a forced air oven. The handsheet
samples were
continued at a constant humidity (50%) and at a constant temperature (73 F)
for 24 hours prior
to testing.
Tensile Measurements
[00106] Dry tensile and wet tensile (test specimens immersed in distilled
water at 23.0 0.2 C)
were tested to measure improved paper dry and wet tensile strength
performance. Dry and wet
tensile are reported for wet and dry breaking length (Wet BL and Dry BL) in
kM/m. Dry tensile
measurement method refers to TAPPI Test Method T494 om-01 (Effective Date Sep.
5, 2001).
Wet tensile measurement method refer to TAPPI Test Method T456 om-03
(Effective Date May
13, 2003).
% Wet/Dry Tensile (/0 W/D Tensile)
[00107] % Wet/Dry Tensile is measured as a percentage of wet to dry tensile,
that is, %W/D BL
(breaking length) is the (wet tensile breaking length)/(dry tensile breaking
length)x100.
Wet and Dry Tear
[00108] Dry tear measurement method refer to TAPPI Test Method T 414-om-04
(Effective date
of Issue May 3, 2004). Wet tear measurement determined by TAPPI Test Method T
414-om-04
(Effective date of Issue May 3, 2004).
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EXAMPLES
[00109] The following examples are provided to illustrate various embodiments
of the disclosure
and the claims. Unless otherwise specified, reagents were obtained from
commercial sources.
The following analytical methods were used to characterize the resins.
Example 1. Preparation of Polyamidoamine Prepolymer I
1001101 A glass reactor with a 5-neck top was equipped with a stainless steel
stirring shaft, a
reflux condenser, temperature probe, and a hot oil bath, To the reactor was
added 500.5 grams
of DETA (diethylenetriamine). The stirrer was turned on and 730 grams of
adipic acid was
added slowly to the reactor over 45 minutes with stirring. The reaction
temperature increased
from 25 C to 145 C during adipic acid addition. After the adipic acid addition
was complete,
the reactor was immersed in a hot oil bath heated to 160 C. At 150 C the
reaction mixture began
to reflux. The reflux condenser was reconfigured for distillation, and
distillate was collected in a
separate receiver. The reaction mixture was sampled at 30 minute intervals.
Each sample was
diluted to 45% solids with water, and the viscosity was measured with
Brookfield viscometer.
When the sample reached 290 cP the distillation condenser was reconfigured to
reflux. Water
was added slowly to the reaction mixture through the reflux condenser to
dilute and cool the
reaction. Water was added to obtain a final solids of 450/s. The viscosity was
290 cP.
Example 2. Preparation of Polyamidoamine Prepolymer
1001111 A glass reactor with a 5-neck top was equipped with a stainless steel
stirring shaft, a
reflux condenser, temperature probe, and a hot oil bath. To the reactor was
added 1574.5 grams
DBE-5 (glutaric acid dimethyl ester, or dibasic ester). The stirrer was turned
on and 1038.9
grams of DETA was added to the reactor with stirring. The reactor was immersed
in a hot oil
bath heated to 100 C. At 90 C the reaction mixture began to reflux. The reflux
condenser was
reconfigured for distillation and distillate was collected in a separate
receiver. The reaction
mixture was sampled at 30 minute intervals. Each sample was diluted to 45%
solids with water,
and the viscosity was measured with Brookfield viscometer. When the sample
reached 220 cP
the distillation condenser was reconfigured to reflux. Water was added slowly
to the reaction
mixture through the reflux condenser to dilute and cool the reaction. Water
was added to obtain
a final solids of 45%. The viscosity was 220 cP.
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Example 3. Preparation of a Wet Strength Resin
[00112] Step I. A glass reactor with 5-neck top was equipped with a glass
stirring shaft and
Teflon paddle, an equal pressure addition funnel, temperature and pH probe,
stainless steel
cooling coils, sample valve, and heating mantle. To the reactor was added
445.64 grams of
Polyamidoamine Prepolymer II from Example 2. Water, 5.25 grams was added and
the stirrer
was started. The reaction mixture was heated to 35 C and 2.028 grams of N, N-
methylene-bis-
acrylamide (Pfaltz & Bauer, Inc.) was added. The reaction mixture was heated
to 60 C and held
at that temperature for 4 hours. The viscosity of the reaction mixture
advanced to 384 cP
(Brookfield-SSA). The intermediate (partially cross-linked) prepolymer mixture
was utilized in-
situ in the following Step 2.
[00113] Step 2. The reaction temperature of the intermediate prepolymer
mixture from Step 1
was adjusted to 25 C, and 88.46 grams of water was added. The reaction
temperature was then
adjusted to 21 C and 121.21 grams of epichlorohydrin was added over 75
minutes. This reaction
mixture was allowed to warm to 25 C over 45 minutes and 446.27 grams of water
was added.
This reaction mixture was heated to 45 C, and after 2 hours was heated to 55
C. After about 4
hours, a mixture of formic acid and sulfuric acid was added to adjust the pH
to 2.87. (Generally,
the pH can be adjusted using any organic acid, mineral acid, or combination
thereof, for
example, acetic acid, formic acid, hydrochloric acid, phosphoric acid,
sulfuric acid, or any
combination thereof) The reaction mixture then was cooled to 25 C, and water
was added to
adjust the solids to 25.0%. The viscosity of the resultant wet strength resin
was 187 cP.
Example 4. Preparation of a Wet Strength Resin
[00114] Step 1. A glass reactor with 5-neck top was equipped with a glass
stirring shaft and
Teflon paddle, an equal pressure addition funnel, temperature and pH probe,
stainless steel
cooling coils, sample valve, and heating mantle. To the reactor was added
1000.00 grams of
Polyamidoamine Prepolymer I from Example 1. The stirrer was started and the
prepolymer was
heated to 40 C. AT, N-Methylene-bis-acrylamide, 15.16 grams (Pfaltz & Bauer,
Inc), was added
slowly while the reaction mixture was heated to 60 C. The reaction mixture
then was held at
60 C for about 2 hours, and the viscosity advanced to 4,630 cP (Brookfield-
SSA), at which point
the viscosity advancement stopped. The reaction was cooled to 25 C. The
intermediate
(partially cross-linked) prepolymer was isolated and stored.
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[00115] Step 2. To the reactor configured as described in Step I was added
366.04 grams of
intermediate (partially cross-linked) prepolymer from Step / above. The
reaction temperature
was adjusted to 25 C and 120.13 grams of water was added. The viscosity of the
reaction
mixture was 837 cP. To the intermediate partially cross-linked prepolymer was
added 77.89
grams of epichlorohydrin at 25 C over 90 minutes. 428.19 Grams of water was
added to the
reaction mixture. The reaction was held at 25 C for 18 hours while sampling
periodically for 13C
N1VIR analysis. During this time the viscosity of the reaction increased from
18 cP to 319 cP
(Brookfield-SSA). This reaction was treated with concentrated sulfuric acid to
adjust the pH to
2.94. The reaction mixture was adjusted to 25.0% solids, and the viscosity was
335 cP.
Example 5. Preparation of a Wet Strength Resin
1001161 Step /. A glass reactor with 5-neck top was equipped with a glass
stirring shaft and
Teflon paddle, an equal pressure addition funnel, temperature and pH probe,
stainless steel
cooling coils, sample valve, and heating mantle. To the reactor was added
449.10 grams of
Polyamidoamine Prepolymer II from Example 2. The stirrer was started, the
reaction mixture
was heated to 30 C, and 6.92 grams of poly(propylene glycol) diglycidyl ether
(Polystar) was
added over 1 hour. The reaction mixture held at 30 C for 1 hour and was then
heated to 60 C, at
which point the viscosity was 416 cP. The reaction mixture was heated at 60 C
for about 4
hours, and the viscosity advanced to 542 cP (Brookfield-SSA). The intermediate
cross-linked
prepolymer was utilized in-situ in Step 2 that follows.
[00117] Step 2. The reaction temperature of the intermediate prepolymer
mixture from Step I
was adjusted to 25 C, and 80.10 grams of water was added. To the reactor was
added 118.79
grams of epichlorohydrin over 75 minutes. The reaction was allowed to warm to
30 C over 45
minutes, and 431.35 grams of water was added. The reaction was warmed to 45 C
over 45
minutes and after 2 hours was heated to 50 C. After about 3.5 hours the
viscosity of the reaction
was about 320 cP (Gardner-Holdt bubble tube), and then a mixture of formic
acid and sulfuric
acid was added to adjust the pH to 3.00. The reaction mixture was cooled to 25
C and water was
added to adjust the solids to 25.0%. The viscosity of the resultant wet
strength resin was 219 cP.
Example 6. Preparation of Handsheets
[00118] A comparison of wet strength resin performance with standard
commercially available
wet strength resins is provided in the examples and data tables. Each data
table indicates the
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stock used in the comparisons and the stock freeness (CSF) is reported. The
resins were added at
the rate shown (lb resin/ton of pulp solids) to a thick stock allowing a 2-
minute mixing time.
The treated stock was immediately poured into the headbox of the Noble & Wood
handsheet
machine containing pH pre-adjusted water.
[00119] The target sheet basis weight is indicated in each set of data in
lb/ft2. Each wet sheet was
given two passes through the full load wet press, and then placed on the drum
dryer at 105 C
without the blotter for 1 minute. All sets of handsheets were further cured
for 10 minutes at
105 C in a forced air oven. The handsheet samples were continued at a constant
humidity (50%)
and at a constant temperature (73 F.) for 24 hours prior to testing. Any
additional conditions are
reported in the Tables. The handsheet samples were continued at a constant
humidity (50%) and
at a constant temperature (73 F.) for 24 hours prior to testing.
[00120] The composition resins were added at the rate (lb/ton) of pulp solids
as indicated with
each data table to thick stock (see Tables) allowing a 2-minute mixing time.
The treated stock
was immediately poured into the headbox of the Noble & Wood handsheet machine
containing
pH pre-adjusted water (pH of 7.0). The target sheet basis weight is indicated
in each Table.
Each wet sheet was given two passes through the full load wet press, and then
placed on the
105 C drum dryer without the blotter for 1 minute. All sets of handsheets were
further cured for
3 minutes at 105 C in a forced air oven. The handsheet samples were continued
at a constant
humidity (50%) and at a constant temperature (73 F.) for 24 hours prior to
testing.
Example 7. Evaluation of Composition Properties and Performance
[00121] A comparison of wet strength resin properties with standard
commercially available wet
strength resins is provided in the following tables. The wet strength resin
properties of the resin
prepared according to this disclosure were examined and compared to standard
commercially
available wet strength resin products, including the Amres series (Georgia-
Pacific) of resins
and the Kymene (Ashland) resins. Both properties of the resins themselves and
the
performance of the resins for imparting wet strength are compared in the
following tables.
[00122] Table 1 illustrates that the wet strength resins prepared according to
this disclosure show
significant improvement in properties as compared to commercially available
resins. For
example, at comparable solids content, the Example 3 resin has significantly
higher charge
density, proportion of azetidinium ions to amide residues, molecular weight,
azetidinium
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equivalent weight, and other properties as compared to conventional resins.
Moreover the
undesired 1,3-dichloro2-propanol (1,3-DCP) content in the resulting resin is
substantially
reduced.
Table 1. Properties of wet strength resin compared to commercially available
resins A
Azet
Product Solids Charge Mw Azet Eq Wt
DCP @ 25%
Ratio
Example 3 25 2.80 0.80 1.00E6 2,690 9,800
Resin 1 25 2.00 0.67 8.00E5 1,753 17,000
Resin 2 25 1.94 0.66 8.00E5 1,727 15,500
Resin 3 25 1.35 0.66 8.00E5 1,727 11,050
Resin 4 21 1.94 0.65 5.75E5 1,222 9,200
Resin 5 12.5 1.85 0.62 6.00E5 1,217 15,800
A Abbreviations are as follows:
Solids is the total solids or non-volatiles in the resin material, including
polymer and any additives.
Charge is the charge density in milliequivalents per gram of solids (meq/g),
measured with a titration test
using a Muetek nitration test.
Azet is the ratio of azetidinium ions to amide residues in the wet strength
resin as measured by quantitative
13C NMR spectroscopy.
Mw is the weight average molecular weight.
Azet Eq Wt is the degree of polymerization multiplied by the Azet ratio, or
(degree of polymerization) x
(Azet).
DCP @ 25% is the concentration of epichlorohydrin hydrolysis by product 1,3-
dichloropropanol (DCP)
remaining in the resin at 25% solids.
[00123] Table 2 illustrates the improvements in wet breaking length of premium
grade
heavyweight towel when treated with the resins according to this disclosure.
Comparisons of the
same properties obtained using conventional resins are provided, with data
measured at different
application rates. Substantial improvements in properties are observed using
resins prepared as
in this disclosure.
Table 2. Performance properties of wet strength resin compared to commercially
available
resins at different application rates A
Wet BL %W/D BL
Product
8 lb/ton 16 lb/ton 8 lb/ton 16 lb/ton
Example 3 1.68 2.30 25.79 35.22
Resin 1 1.46 2.14 21.76 32.11
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Wet BL "AW/D BL
Product
8 lb/ton 16 lb/ton 8 lb/ton 16 lb/ton
Resin 2 1.33 1.96 19.90 29.38
A Conditions: Premium Grade (Bleached Virgin) Heavyweight Towel, Noble & Wood
Sheetformer,
target sheet basis weight 28 lb/3000 sq ft. BSWK, pH 7.54, Thick Stock 2.31%,
stock freeness 584
CSF, CMC 2 lb/ton, Cure for 5 min/105 C.
[00124] Table 3 likewise illustrates the improvements in wet breaking length
of recycled
heavyweight towel when treated with the resins according to this disclosure at
different
application rates (5, 10, and 15 lb composition resin per ton of pulp solids).
Comparisons of the
same properties obtained using conventional resins are provided. In every
case, the substantial
improvement in performance using the disclosed wet strength resins is
illustrated.
Table 3. Performance properties of wet strength resin compared to commercially
available
resins at different application rates. A
Wet BL
Product
lb/ton 10 lb/ton 15 lb/ton
Example #3 1.98 2.40 2.56
Resin 1 1.72 2.02 2.21
Resin 2 1.76 2.01 2.26
Resin 6 1.65 1.74 1.93
A Conditions: 100% Recycled Heavyweight Towel; Noble & Wood Sheetformer, 28
lb/3000 sq ft; pH
7.5; Thick Stock 1.50%, 475 CSF, Dryers 230 F, Cure for 5 min/105 C.
[00125] Similarly, Table 4 illustrates the improvements in wet tensile in
breaking length of
unbleached SW kraft at different application rates (4, 6, and 8 lb composition
resin per ton of
pulp solids) and the % wet/dry tensile as compared to more conventional resin
materials. In each
case, improvement in performance using the disclosed wet strength resins was
observed. The
wet tear was also reported and measured using the designated resins, and
again, at every
application rate the improvement in perfoimance using the disclosed wet
strength resins is
illustrated.
Table 4. Performance properties of wet strength resin compared to commercially
available
resins at different application rates. A
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% Wet/Dry Tensile Wet Tear
Product
4th/ton 6 lb/ton 8 lb/ton 4 lb/ton 6 lb/ton
8th/ton
Example #3 44.22 64.71 80.52 95.33 143.46
170.49
Amres
43.14 58.11 73.11 88.84 120.80 154.24
1110-E
Amres 652 37.93 48.99 62.23 77.45 103.04
133.06
A Conditions: 100% Unbleached SW Kraft, Noble & Wood Sheetformer, 83 lb/3000
sq ft; pH = 6.97,
Thick Stock 2.51%, 714 CSF, 13 lb/ton alum, 4 passes on dryer 230 F, 5 min/105
C cure.
[00126] Embodiments of the present disclosure further relate to any one or
more of the following
paragraphs:
1001271 1. A process for preparing a resin, comprising: a) reacting a
polyamine with a symmetric
cross-linker to produce a partially cross-linked polyamine; b) adding a
epihalohydrin to the
partially cross-linked polyamine to produce a halohydrin-functionalized
polymer; and c)
cyclizing the halohydrin-functionalized polymer to form the resin having
azetidinium moieties.
[00128] 2. The process according to paragraph 1, wherein the polyamine has the
structure
NN
- w
[00129] wherein R is alkyl, hydroxyalkyl, amine, amide, aryl, heteroaryl or
cycloalkyl and w is an
integer from 1 to about 10,000.
[00130] 3. The process according to paragraph 1, wherein the polyamine has
molecular weight of
about 2,000 to about 1,000,000.
[00131] 4. The process according to paragraph 3, wherein the polyamine has
molecular weight of
about 10,000 to about 200,000.
[00132] 5. The process according to paragraph 1, wherein the symmetric cross-
linker is selected
from a diacrylate, a bis(acrylamide), a diepoxide and polyazetidinium
compounds.
[00133] 6. The process according to paragraph 1, wherein the symmetric cross-
linker is selected
from:
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0 0
, wherein R4 is (CH2)t, and wherein t is 1, 2, or 3;
o , wherein x is from 1 to about 100;
cH3 o , wherein y is from 1 to about 100;
0 91,
/ A
, wherein x' + y' is from 1 to about
100;
0
z
0 , wherein z is from 1 to about 100;
o H
N
cie
N
- P
OH , wherein a q/p
ratio
is from about 10 to about 1000;
a copolymer of an acrylate monomer, a methacrylate monomer, an alkene monomer,
or a
diene monomer, with an azetidinium-functionalized monomer selected from
H2cõ.õoH3
H3CH3C.,õ1\0-00 NCI
YC 49
CH3 OH , and a combination thereof, wherein a fraction
of
the azetidinium-functionalized monomer to the acrylate monomer, the
methacrylate monomer,
the alkene monomer, or the diene monomer in the copolymer is from about 0.1%
to about 12%;
and any combination thereof.
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[00134] 7. The process according to paragraph 1, wherein the symmetric cross-
linker is selected
from N,N'-m ethyl ene-bi s-acryl amide, N,N'-m ethyl en e-bi s-m ethacryl
amide, pot y(ethyl en e
glycol) diglycidyl ether, poly(propylene glycol) diglycidyl ether,
polyethylene glycol diacrylate,
polyazetidinium compounds and any combination thereof.
[00135] 8. The process according to paragraph 1, wherein the epihalohydrin is
selected from
epichlorohydrin, epibromohydrin, and epiiodohydrin.
[00136] 9. The process according to paragraph 8, wherein the epihalohydrin is
epichlorohydrin.
[00137] 10. The process according to paragraph 1, further comprising: reacting
the polyamine
with a mono-functional modifier prior to, during, or after treating with the
symmetric cross-
linker.
[00138] 11. The process according to paragraph 10, wherein the mono-functional
modifier is
selected from a neutral or cationic acrylate compound, a neutral or cationic
acrylamide
compound, an acrylonitrile compound, a mono-epoxide compound, or a combination
thereof.
[00139] 12. The process according to paragraph 10, wherein the mono-functional
modifier is
selected from an alkyl acrylate, acrylamide, an alkyl acrylamide, a dialkyl
acrylamide,
acrylonitrile, a 2-alkyl oxirane, a 2-(allyloxyalkyl)oxirane, a hydroxyalkyl
acrylate, an co-
(acryl oyl oxy)-al kyltri m ethylamm oni urn compound, an co -(acryl ami do)-
al kyltri m ethylamm oni urn
compound, and any combination thereof
[00140] 13. The process according to paragraph 10, wherein the mono-functional
modifier
comprises at least one of: methyl acrylate, alkyl acrylate, acrylamide, N-
methylacrylamide, N,N-
dimethylacrylamide, acrylonitrile, 2-methyloxirane, 2-ethyloxirane, 2-
propyloxirane, 2-
(allyloxymethyl)oxirane, 2-hydroxyethyl acrylate, 2-(2-hydroxyethoxy)ethyl
acrylate, 2-
(acryloyloxy)-N,N,N-trimethylethanaminium,
3 -(acryloyl oxy)-N,N,N-trim ethylpropan-1-
aminium, 2-acrylamido-N,N,N-trimethylethanaminium, 3-acrylamido-N,N,N-
trimethylpropan-1-
aminium, and 1-i sopropy1-3 -(m ethacryl oyl oxy)-1-methyl azeti dinium
chloride.
[00141] 14. The process according to paragraph 1, wherein the ratio of
azetidinium ions to
secondary amine moieties in the resin is from about 0.4 to about 1Ø
[00142] 15. The process according to paragraph 1, wherein the concentration of
1,3-dichloro-2-
propanol (1,3-DCP) is less than about 15,000 ppm.
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[00143] 16. The process according to paragraph 1, wherein a pH of the resin is
adjusted using an
acid.
[00144] 17. The process according to paragraph 16, wherein the acid is acetic
acid, formic acid,
hydrochloric acid, phosphoric acid, sulfuric acid, organic acid or mineral
acid or a combination
thereof,
[00145] 18. The process according to paragraph 16, wherein the pH of the resin
is adjusted to
about pH 2.0 to about pH 4.5.
[00146] 19. The process according to paragraph 1, wherein the solids content
of the resin is
adjusted from about 10% to about 50%.
[00147] 20. The process according to paragraph 1, wherein the resin has a
charge density of
about 1.0 to about 4.0 mEq/g of solids.
[00148] 21. The process according to paragraph 1, wherein the resin has a
ratio of azetidinium
ions to amide residues is from about 0.5 to about 0.9.
[00149] 22. The process according to paragraph 1, wherein the resin has a
molecular weight from
about 0.02 x 106 to about 3.0 x 106.
[00150] 23. The process according to paragraph 1, wherein the resin has an
azetidinium
equivalent weight from about 1,800 to about 3,500.
[00151] 24. The process according to paragraph 1, wherein the resin has 1,3-
dichloro-2-propanol
(1,3-DCP) content less than about 10,000 ppm.
[00152] 25. A composition comprising a resin, wherein the resin is prepared by
a process
comprising: a) reacting a polyamine with a symmetric cross-linker to produce a
partially cross-
linked polyamine; b) adding a epihalohydrin to the partially cross-linked
polyamine to produce a
halohydrin-functionalized polymer; and c) cyclizing the halohydrin-
functionalized polymer to
form the resin having azetidinium moieties.
[00153] 26. The composition according to paragraph 25, wherein the polyamine
has the structure
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NN
- w
[00154] wherein R is alkyl, hydroxyalkyl, amine, amide, aryl, heteroaryl or
cycloalkyl and w is an
integer from 1 to about 10,000.
[00155] 27. The composition according to paragraph 25, wherein the polyamine
has molecular
weight of about 2,000 to about 1,000,000.
10H01561 28. The composition according to paragraph 27, wherein the polyamine
has molecular
weight of about 10,000 to about 200,000.
[00157] 29. The composition according to paragraph 25, wherein the symmetric
cross-linker is
selected from a diacrylate, a bis(acrylamide), a diepoxide and polyazetidinium
compounds.
[00158] 30. The composition according to paragraph 25, wherein the symmetric
cross-linker is
selected from:
0 0
, wherein R4 is (CI-12), wherein t is 1, 2, or 3;
o
o , wherein x is from 1 to about 100;
-
cH3 0 , wherein y is from 1 to about 100;
cH, iL\o
0,
, wherein x' + y' is from 1 to about
100;
0
0
- z
0 , wherein z is from 1 to about 100;
CA 02987852 2017-11-29
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o
- o
N
LrN i 9 Ce
0
0
P
OH
, wherein a q/p ratio
is from about 10 to about 1000;
a copolymer of an acrylate monomer, a methacrylate monomer, an alkene monomer,
or a
diene monomer, with an azetidinium-functionalized monomer selected from
H2CyCH3
o
Ne ci
H3c
YCie
CH3 OH , and a combination thereof, wherein
the fraction
of azetidinium-functionalized monomer to the acrylate monomer, the
methacrylate monomer, the
alkene monomer, or the diene monomer in the copolymer is from about 0.1% to
about 12%; and
any combination thereof.
1001591 31. The composition according to paragraph 25, wherein the symmetric
cross-linker is
selected from N,N'-methyl en e-bi s-acryl amide,
N,N'-methylene-bis-methacrylamide,
poly(ethylene glycol) diglycidyl ether, poly(propylene glycol) diglycidyl
ether, polyethylene
glycol diacrylate, polyazetidinium compounds and any combination thereof.
1001601 32. The composition according to paragraph 25, wherein the
epihalohydrin is selected
from epichlorohydrin, epibromohydrin, and epiiodohydrin.
1001611 33.
The composition according to paragraph 32, wherein the epihalohydrin is
epichlorohydrin.
1001621 34. The composition according to paragraph 25, wherein the process
further comprises:
reacting the polyamine with a mono-functional modifier prior to, during, or
after treating with
the symmetric cross-linker.
1001631 35. The composition according to paragraph 34, wherein the mono-
functional modifier is
selected from a neutral or cationic acrylate compound, a neutral or cationic
acrylamide
compound, an acrylonitrile compound, a mono-epoxide compound, or a combination
thereof
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[00164] 36. The composition according to paragraph 34, wherein the mono-
functional modifier is
selected from an alkyl acrylate, acrylamide, an alkyl acrylamide, a dialkyl
acrylamide,
acrylonitrile, a 2-alkyl oxirane, a 2-(allyloxyalkyl)oxirane, a hydroxyalkyl
acrylate, an co-
(acryloyloxy)-alkyltrimethylammonium compound, an co -(acrylamido)-
alkyltrimethylammonium
compound, and any combination thereof.
[00165] 37. The composition according to paragraph 34, wherein the mono-
functional modifier
comprises at least one of: methyl acrylate, alkyl acrylate, acrylamide, N-
methylacrylamide, N,N-
di m ethyl acryl am i de, acrylonitrile, 2-m ethyloxi rane ; 2-ethyloxirane, 2-
prop yl oxi ran e, 2-
(allyloxymethyl)oxirane, 2-hydroxyethyl acrylate, 2-(2-hydroxyethoxy)ethyl
acrylate, 2-
(acryl oyloxy)-N,N,N-trimethylethanaminium,
3 -(acryl oyl oxy)-N,N,N-tri m ethylprop an-1-
aminium; 2-acrylamido-N,N,N-trimethylethanaminium, 3 -acrylami do-N,N,N-trim
ethylprop an-1-
aminium, and 1-i sopropy1-3 -(methacryl oyloxy)-1-methylazetidinium chloride.
[00166] 38. The composition according to paragraph 25, wherein the ratio of
azetidinium ions to
secondary amine moieties in the resin is from about 0.4 to about 1Ø
[00167] 39. The composition according to paragraph 25, wherein the
concentration of 1,3-
dichloro-2-propanol (1,3-DCP) is less than about 15,000 ppm.
[00168] 40. The composition according to paragraph 25, wherein a pH of the
resin is adjusted
using an acid.
[00169] 41. The composition according to paragraph 40, wherein the acid is
acetic acid, formic
acid, hydrochloric acid, phosphoric acid, sulfuric acid, organic or mineral
acid or a combination
thereof.
1001701 42. The composition according to paragraph 40, wherein the pH of the
resin is adjusted
to about pH 2.0 to about pH 4.5.
[00171] 43. The composition according to paragraph 25, wherein the solids
content of the resin is
adjusted from about 10% to about 50%.
[00172] 44. The composition according to paragraph 25, wherein the resin has a
charge density
of about 1.0 to about 4.0 mEq/g of solids.
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[00173] 45. A composition having at least three of the following
characteristics: a) a charge
density of about 1.0 to about 4.0 mEq/g of solids; b) a ratio of azetidinium
ions to amide residues
in the resin is from about 0.5 to about 0.9.; c) a molecular weight from about
0.1 x 106 to about
3.0 x 106; d) an azetidinium equivalent weight from about 1,800 to about
3,500; and e) a 1,3-
dichloro-2-propanol (1,3-DCP) content of less than about 10,000 ppm when the
solids content is
about 25%.
[00174] 46. A paper strengthened with the composition of any one of paragraphs
25-45.
[00175] 47. A process of treating paper to impart wet strength, the process
comprising treating
pulp fibers used to make a paper with a resin composition made by: a) reacting
a polyamine with
a symmetric cross-linker to produce a partially cross-linked polyamine; b)
adding a
epihalohydrin to the partially cross-linked polyamine to produce a halohydrin-
functionalized
polymer; and c) cyclizing the halohydrin-functionalized polymer to form the
resin having
azetidinium moieties.
1001761 48. A strengthening resin comprising a polyamine partially cross-
linked with a bridging
moiety and having azetidinium ions, wherein the bridging moiety is derived
from a functionally
symmetric cross-linker comprising a diisocyanate, a 1,3-dialkyldiazetidine-2,4-
dione, a
dianhydride, a diacyl halide, a dienone, a dialkyl halide, or any mixture
thereof.
1001771 49. A method for strengthening paper, comprising contacting fibers
with a strengthening
resin comprising a polyamine partially cross-linked with a bridging moiety and
having
azetidinium ions, wherein the bridging moiety is derived from a functionally
symmetric cross-
linker comprising a diisocyanate, a 1,3-dialkyldiazetidine-2,4-dione, a
dianhydride, a diacyl
halide, a dienone, a dialkyl halide, or any mixture thereof.
[00178] 50. A method for making a strengthening resin, comprising: reacting a
polyamine and a
functionally symmetric cross-linker to produce a partially cross-linked
polyamine, wherein the
functionally symmetric cross-linker comprises a diisocyanate, a 1,3 -
dialkyldiazetidine-2,4-dione,
a dianhydride, a diacyl halide, a dienone, a dialkyl halide, or any mixture
thereof; and reacting
the partially cross-linked polyamine with an epihalohydrin to produce a
strengthening resin
having azetidinium ions.
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[00179] 51. The strengthening resin or method according to any one of
paragraphs 48 to 50,
wherein the functionally symmetric cross-linker comprises the diisocyante.
[00180] 52. The strengthening resin or method according to any one of
paragraphs 48 to 51,
wherein the diisocyanate is a blocked diisocyanate.
[00181] 53. The strengthening resin or method according to any one of
paragraphs 48 to 52,
wherein the functionally symmetric cross-linker comprises the 1,3-
dialkyldiazetidine-2,4-dione.
[00182] 54. The strengthening resin or method according to any one of
paragraphs 48 to 53,
wherein the functionally symmetric cross-linker comprises the dianhydride.
[00183] 55. The strengthening resin or method according to any one of
paragraphs 48 to 54,
wherein the functionally symmetric cross-linker comprises the diacyl halide.
[00184] 56. The strengthening resin or method according to any one of
paragraphs 48 to 55,
wherein the functionally symmetric cross-linker comprises the dienone.
[00185] 57. The strengthening resin or method according to any one of
paragraphs 48 to 56,
wherein the functionally symmetric cross-linker comprises the dialkyl halide.
[00186] 58. The strengthening resin or method according to any one of
paragraphs 48 to 57,
wherein the functionally symmetric cross-linker further comprises a diacrylate
compound, a
bis(acrylamide) compound, a diepoxide compound, a polyazetidinium compound,
N,N-
methylene-bis-methacrylamide, a poly(alkylene glycol) diglycidyl ether, or any
mixture thereof.
1001871 59. The strengthening resin or method according to any one of
paragraphs 48 to 58,
wherein the polyamine comprises a polyamidoamine.
[00188] 60. The strengthening resin or method according to any one of
paragraphs 48 to 59,
wherein the azetidinium ions are formed by reacting an epihalohydrin and the
polyamine
partially cross-linked with the bridging moiety.
[00189] 61. The strengthening resin or method according to any one of
paragraphs 48 to 60,
wherein the strengthening resin has a charge density of 2.25 mEq/g of solids
to 3.5 mEq/g of
solids.
[00190] 62. The strengthening resin or method according to any one of
paragraphs 48 to 61,
wherein the strengthening resin has an azetidinium equivalent weight of 2,000
to 3,500.
49
[00191] 63. The strengthening resin or method according to any one of
paragraphs 48 to 62,
wherein the strengthening resin has a weight average molecular weight of
900,000 to 1,700,000.
[00192] 64. The strengthening resin or method according to any one of
paragraphs 48 to 63,
wherein the strengthening resin contains less than 10,000 ppm of 1,3-dichloro-
2-propanol.
[00193] 65. The strengthening resin or method according to any one of
paragraphs 48 to 60,
wherein the strengthening resin has a charge density of 2.25 mEq/g of solids
to 3.5 mEq/g of
solids, an azetidinium equivalent weight of 2,000 to 3,500, a weight average
molecular weight of
900,000 to 1,700,000, and contains less than 10,000 ppm of 1,3-dichloro-2-
propanol.
[00194] 66. The strengthening resin or method according to any one of
paragraphs 48 to 65,
wherein the functionally symmetric cross-linker further comprises a di-
acrylate compound, a
bis(acrylamide) compound, a di-epoxide compound, a polyazetidinium compound,
N,N'-
methylene-bis-methacrylamide, and a poly(alkylene glycol) diglycidyl ether, or
any mixture
thereof.
[00195] Certain embodiments and features have been described using a set of
numerical upper
limits and a set of numerical lower limits. It should be appreciated that
ranges including the
combination of any two values, e.g., the combination of any lower value with
any upper value,
the combination of any two lower values, and/or the combination of any two
upper values are
contemplated unless otherwise indicated. Certain lower limits, upper limits
and ranges appear in
one or more claims below. All numerical values are "about" or "approximately"
the indicated
value, and take into account experimental error and variations that would be
expected by a
person having ordinary skill in the art.
[00196] Various terms have been defined above. To the extent a term used in a
claim is not
defined above, it should be given the broadest definition persons in the
pertinent art have given
that term as reflected in at least one printed publication or issued patent.
Date Recue/Date Received 2022-06-21
CA 02987852 2017-11-29
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[00197] While the foregoing is directed to certain illustrative embodiments,
other and further
embodiments of the invention can be devised without departing from the basic
scope thereof, and
the scope thereof is determined by the claims that follow.
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