PAPER MAKING PROCESS AND CROSSLINKING COMPOSITIONS FOR USE IN SAME

PROCEDE DE FABRICATION DU PAPIER ET COMPOSITIONS DE RETICULATION DESTINEES A CE PROCEDE

English Abstract

The present invention relates to methods for manufacturing paper or paperboard
with improved strength, the methods comprising the addition of an aqueous
aldehyde generating compound or a glyoxal releasing compound into or onto a
fiber furnish prior to drying of the paper or paperboard sheet.

French Abstract

La présente invention porte sur des procédés de fabrication du papier ou du carton dont la résistance est améliorée, ces procédés consistant à ajouter un composé générant un aldéhyde aqueux ou un composé libérant le glyoxal dans ou sur une composition de fibres avant de sécher la feuille de papier ou de carton .

Claims

What is claimed is:
1.~A method for manufacturing paper or paperboard sheet with increased
strength, the method comprising the steps of:
providing a fiber slurry and a gelatinized starch composition, each of which
is
suitable for use in making paper or paperboard;
providing at least one crosslinker composition comprising at least one
aldehyde generating compound capable of forming at least two or more covalent
bonds to functional groups present in the starch or fiber of the web;
mixing the gelatinized starch composition and the crosslinker composition;~
adding the mixture of gelatinized starch composition and crosslinker
composition to the fiber slurry contemporaneously to mixing the gelatinized
starch
composition and the crosslinker composition; and
forming the paper or paperboard sheet.
2. ~The method of claim 1, wherein the gelatinized starch composition and
the crosslinker composition are mixed together in a batch process prior to
addition to
the fiber slurry.
3. ~The method of claim 1, wherein the gelatinized starch composition and
the crosslinker composition are mixed together in a continuous flow process
prior to
addition to the fiber slurry.
4. ~The method of claim 1, wherein the gelatinized starch composition and
the crosslinker composition are mixed together less than about 1 hour prior to
addition
to the fiber slurry.
5.~The method of claim 1, wherein the gelatinized starch composition and
the crosslinker composition are mixed together less than about 30 minutes
prior to
addition to the fiber slurry.
-33-

6. ~The method of claim 1, wherein the gelatinized starch composition and
the crosslinker composition are mixed together less than about 10 minutes
prior to
addition to the fiber slurry.
7. ~The method of claim 1, wherein the gelatinized starch composition and
the crosslinker composition are mixed together less than about 1 minute prior
to
addition to the fiber slurry.
8. ~The method of claim 1, wherein a paper sheet is prepared by the
method of manufacture.
9. ~The method of claim 1, wherein a paperboard sheet is prepared by the
method of manufacture.
10. ~The method of claim 1, wherein the starch is self-retaining.
11. ~The method of claim 10, wherein the starch is a cationic starch.
12. ~The method of claim 10, wherein the starch is pregelatinized self-
retaining starch selected from potato, corn or wheat starch.
13. ~The method of claim 1, wherein the crosslinker composition comprises
between about 0.001% to about 80% aldehyde generating compound by weight in an
aqueous media.
14. ~The method of claim 13, wherein the crosslinker composition does not
comprise starch or gelatinized starch.
15. ~The method of claim 13, wherein the crosslinker composition is stable
in the absence of starch, gelatinized starch, or pulp fiber for at least one
week and
reacts at a temperature of greater than about 25°C to form covalent
bonds with starch,
gelatinized starch or pulp fiber in less than an hour.
-34-

16. ~The method of claim 13, wherein the crosslinker composition
comprises at least one equivalent of a compound having at least two aldehyde
residues and between about 0.25 and about 5 equivalents of one or more
stabilizing
compounds.
17. ~The method of claim 16, wherein the compound having at least two
aldehyde residues is glyoxal.
18. ~The method of claim 16, wherein the stabilizing agent is a linear,
branched or cyclic organic molecule having at least two functional groups
capable of
blocking an aldehyde residue.
19. ~The method of any one of claims 1 through 18, wherein the crosslinker
composition further comprises at least one aldehyde blocking agent.
20. ~The method of claim 19, wherein the crosslinker composition
comprises at least 0.1 molar equivalent of aldehybe blocking agent relative to
the
aldehyde generating compound.
21. ~The method of claim 19, wherein the crosslinker composition
comprises at least one aldehyde blocking agent selected from urea, thiourea,
amines,
alkanols, alkane diols, and alkylene glycols.
22. ~The method of claim 1, wherein the aldehyde generating compound is
a compound of Formula I:
<IMG>~
-35-

Z is monovalent or divalent urea, monovalent or divalent .alpha..omega.-C2-
8alkanediol,
C2-8alkylene glycol, poly(ethylene glycol) having a molecular weight of less
than
about 20,000, .omega.-amino-.alpha.-C2-8alkanol or Z is a 5 to 7 member
optionally substituted
heterocyclic group having one ring nitrogen atom, at least one additional ring
heteroatom selected from N, O, or S, and zero or one oxo substitutents;
n is 0, 1, or 2;
m is 0 or 1;
n' = n if m = 1 or n' = 0 if m = 0, wherein at least one of m and n is not
zero.
23. The method of claim 1, wherein the aldehyde generating compound is
a compound of Formula II:
<IMG>~
wherein
A is an optionally substituted methylene group, an optionally substituted C2-
4alkylene group, or a single bond;
B is carbonyl, thiocarbonyl, or an optionally substituted 1,2-ethylene
residue;
X1 and X2 are independently selected from the group consisting of oxygen and
NR3;
R1 and R2 are independently selected from the group consisting of hydrogen,
hydroxy, optionally substituted C1-20alkyl, optionally substituted C1-
20alkoxy,
optionally substituted urea, optionally substituted thiourea, or
R1 and R2, taken in combination, form a N,N'-divalent urea;
R3 is independently selected at each occurrence of R3 from the group
consisting of hydrogen, 1-hydroxy-ethan-2-al-1-yl group, or a blocked glyoxal
residue.
24. The method of claim 1, wherein the aldehyde generating compound is
a compound of Formula III:
-36-

<IMG>~
wherein
each of X1, X2, and X3 are independently selected from the group consisting of
CH or N; and
R4 and R5 are independently selected at each occurrence of R4 and R5 in
Formula III from the group selected from hydrogen, a 1-hydroxy-ethan-2-al-1-yl
group, or a blocked glyoxal residue; or
one or more occurrences of NR4R5 in Formula III, taken in combination form
an optionally substituted N-piperazinyl residue.
25. The method of claim 24, wherein each of X1, X2, and X3 is nitrogen.
26. The method of claim 24, wherein one or more occurrences of NR4R5 in
Formula III, taken in combination form an optionally substituted N-2,3,5,6-
tetrahydroxypiperazinyl residue.
27. The method of claim 24, wherein the aldehyde generating compound is
a compound of Formula IV:
-37-

<IMG>
wherein
each of X1, X2, and X3 are independently selected from the group consisting of
CH or N; and
R6 is independently selected at each occurrence from the group selected from
optionally substituted alkyl, optionally substituted carboxamide.
28. The method of claim 27, wherein R6 is independently selected at each
occurrence from -C(O)NH2 or -C(O)NHCH(OH)CHO.
29. A method for manufacturing paper or paperboard sheet with increased
strength, the method comprising the steps of:
providing a fiber slurry and a gelatinized starch composition, each of which
is
suitable for use in making paper or paperboard;
providing at least one crosslinker composition comprising at least one
aldehyde generating compound capable of forming at least two or more covalent
bonds to functional groups present in the starch or fiber of the web;
preparing a paper or paperboard web comprising pulp fiber and at least one
starch prepared by mixing the gelatinized starch composition and the fiber
slurry;
-38-

contacting the web with the crosslinker composition under conditions
conducive to formation at least two or more covalent bonds to functional
groups
present in the starch or fiber of the web.
30. ~The method of claim 29, wherein the method of manufacture further
comprises the step of drying the paper or paperboard web.
31. ~The method of claim 30, wherein the crosslinker composition is
contacted with the web prior to the drying process.
32. ~The method of claim 30, wherein the crosslinker composition is
contacted with the paper or paperboard web after the drying step has removed
at least
a portion of moisture from the paper or paperboard web.
33. ~The method of claim 29, wherein the crosslinker composition increases
at least one of the wet strength or the dry strength of the paper or
paperboard prepared
by the method of manufacture.
34. ~The method of claim 1, wherein the crosslinker composition comprises
between about 0.001% to about 80% aldehyde generating compound by weight in an
aqueous media.
35. ~The method of claim 34, wherein the crosslinker composition does not
comprise starch or gelatinized starch.
36. ~The method of claim 34, wherein the crosslinker composition is stable
in the absence of starch, gelatinized starch, or pulp fiber for at least one
week and
reacts at a temperature of greater than about 25°C to form covalent
bonds with starch,
gelatinized starch or pulp fiber in less than an hour.
37. ~The method of claim 34, wherein the crosslinker composition
comprises at least one equivalent of a compound having at least two aldehyde
-39-

residues and between about 0.25 and about 5 equivalents of one or more
stabilizing
compounds.
38. The method of claim 37, wherein the compound having at least two
aldehyde residues is glyoxal.
39. The method of claim 37, wherein the stabilizing agent is a linear,
branched or cyclic organic molecule having at least two functional groups
capable of
blocking an aldehyde residue.
40. The method of any one of claims 29 through 39, wherein the
crosslinker composition further comprises at least one aldehyde blocking
agent.
41. The method of claim 40, wherein the crosslinker composition
comprises at least 0.1 molar equivalent of aldehybe blocking agent relative to
the
aldehyde generating compound.
42. The method of claim 40, wherein the crosslinker composition
comprises at least one aldehyde blocking agent selected from urea, thiourea,
amines,
alkanols, alkane diols, and alkylene glycols.
43. The method of claim 29, wherein the aldehyde generating compound is
a compound of Formula I:
<IMG>
wherein
Z is monovalent or divalent urea, monovalent or divalent .alpha.,.omega.C2-
8alkanediol,
C2-8alkylene glycol, poly(ethylene glycol) having a molecular weight of less
than
-40-

about 20,000, .omega.-amino-.alpha.-C2-8alkanol or Z is a 5 to 7 member
optionally substituted
heterocyclic group having one ring nitrogen atom, at least one additional ring
heteroatom selected from N, O, or S, and zero or one oxo substitutents;
n is 0, 1, or 2;
m is 0 or 1;
n' = n if m = 1 or n' = 0 if m = 0, wherein at least one of m and p is not
zero.
44. The method of claim 29, wherein the aldehyde generating compound is
a compound of Formula II:
<IMG>
wherein
A is an optionally substituted methylene group, an optionally substituted C2-
4alkylene group, or a single bond;
B is carbonyl, thiocarbonyl, or an optionally substituted 1,2-ethylene
residue;
X1 and X2 are independently selected from the group consisting of oxygen and
NR3;
R1 and R2 are independently selected from the group consisting of hydrogen,
hydroxy, optionally substituted C1-20alkyl, optionally substituted C1-
20alkoxy,
optionally substituted urea, optionally substituted thiourea, or
R1 and R2, taken in combination, form a N,N'-divalent urea;
R3 is independently selected at each occurrence of R3 from the group
consisting of hydrogen, 1-hydroxy-ethan-2-al-1-yl group, or a blocked glyoxal
residue.
45. The method of claim 29, wherein the aldehyde generating compound is
a compound of Formula III:
-41-

<IMG>~
wherein
each of X1, X2, and X3 are independently selected from the group consisting of
CH or N; and
R4 and R5 are independently selected at each occurrence of R4 and R5 in
Formula III from the group selected from hydrogen, a 1-hydroxy-ethan-2-al-1-yl
group, or a blocked glyoxal residue; or
one or more occurrences of NR4R5 in Formula III, taken in combination form
an optionally substituted N-piperazinyl residue.
46. The method of claim 45, wherein each of X1, X2, and X3 is nitrogen.
47. The method of claim 45, wherein one or more occurrences of NR4R5 in
Formula III, taken in combination form an optionally substituted N-2,3,5,6-
tetrahydroxypiperazinyl residue.
48. The method of claim 45, wherein the aldehyde generating compound is
a compound of Formula IV:
-42-

<IMG>
wherein
each of X1, X2, and X3 are independently selected from the group consisting of
CH or N; and
R6 is independently selected at each occurrence from the group selected from
optionally substituted alkyl, optionally substituted carboxamide.
49. The method of claim 48, wherein R6 is independently selected at each
occurrence from -C(O)NH2 or -C(O)NHCH(OH)CHO.
50. The method of claim 29, wherein the glyoxal generating compound is a
compound according to Formula II-a:
<IMG>~~
wherein
-43-

A is an optionally substituted methylene group, an optionally substituted C2-
4alkylene group, or a single bond;
B is carbonyl, thiocarbonyl, or an optionally substituted 1,2-ethylene
residue;
X1 and X2 are independently selected from the group consisting of oxygen and
NR3;
R1 and R2 are independently selected from the group consisting of hydrogen,
hydroxy, optionally substituted C1-20alkyl, optionally substituted C1-
20alkoxy,
optionally substituted urea, optionally substituted thiourea, or
R1 and R2, taken in combination, form a N,N'-divalent urea;
R3 is independently selected at each occurrence of R3 from the group
consisting of hydrogen, optionally substituted C1-20alkyl, and unblocked and
blocked
glyoxal residues, where unblocked glyoxal residue is a 1-hydroxy-2-ethanal-1-
yl
group and the blocked glyoxal residue is a 1-hydroxy-2-(protected aldehyde
residue)-
ethan-1-yl group; or
R3 is a 1,2-dihydroxyethylene residue coupled to two rings according to
Formula I; and
wherein the aldehyde generating compound according to Formula I degrades
to generate at least one equivalent of glyoxal when the crosslinking
composition is
contacted with starch or pulp fiber.
51. The method of claim 50, wherein
R1 and R2 are independently selected from the group consisting of hydrogen,
hydroxy, methanol, ethanol, urea, or
R1 and R2, taken in combination, form a N,N'-divalent urea;
R3 is independently selected at each occurrence of R3 from the group
consisting of hydrogen, methyl, and ethyl, or
R3 is an unblocked glyoxal residue or a blocked glyoxal residue selected from
the group consisting of 1,2-dihydroxy-2-(C1-4-alkoxy)-ethan-1-yl, 1,2-
dihydroxy-2-(3-
hydroxypropoxy)-ethan-1-yl, and 1,2-dihydroxy-2-(2-hydroxypropoxy)-ethan-1-yl.
52. The method of claim 50, wherein~
X1 and X2 are NR3;
A is a single bond;
-44-

B is a carbonyl or thiocarbonyl group; and
R1 and R2 are independently selected from hydroxy, C1-6alkoxy, or blocked
glyoxal residues.
53. The method of claim 50, wherein
X1 and X2 are NR3;
A is a 1,1-C1-6alkylene group;
B is a carbonyl or thiocarbonyl group;
R1 and R2 are independently selected from hydrogen, hydroxy, C1-6alkoxy, and
R3 is an unblocked glyoxal residue or a blocked glyoxal residue selected from
the group consisting of 1,2-dihydroxy-2-(C1-4-alkoxy)-ethan-1-yl, 1,2-
dihydroxy-2-(3-~
hydroxypropoxy)-ethan-1-yl, and 1,2-dihydroxy-2-(2-hydroxypropoxy)-ethan-1-yl.
54. The method of claim 50, wherein the glyoxal generating compound is a
compound according to Formula V:
<IMG>
wherein
m is an integer from 0 to about 1000;
A is an optionally substituted methylene group, an optionally substituted C2-
4alkylene group, or a single bond;
B is carbonyl, thiocarbonyl, or an optionally substituted 1,2-ethylene
residue;
R1 and R2 are independently selected from the group consisting of hydrogen,
hydroxyl, optionally substituted C1-20alkyl, optionally substituted C1-
20alkoxy,
optionally substituted urea, optionally substituted thiourea, or
R1 and R2, taken in combination, form a N,N'-divalent urea;
-45-

R3 is independently selected at each occurrence of R3 from the group
consisting of hydrogen, optionally substituted C1-20alkyl, and unblocked and
blocked
glyoxal residues, where unblocked glyoxal residue is a 1-hydroxy-2-ethanal-1-
yl
group and the blocked glyoxal residue is a 1-hydroxy-2-(protected aldehyde
residue)-
ethan-1-yl group; or
R4 is a 1,2-dihydroxyethylene residue; or
R4 is a telechelic oligiomer comprising 2n+1 glyoxal residues alternating with
n groups selected from the group consisting of .alpha.,.omega.-alkane diols,
alkylene glycols, and
poly(ethylene glycol); and
n is an integer of from 0 to about 100;
wherein the aldehyde generating compound according to Formula V degrades
to generate at least one equivalent of glyoxal when the crosslinking
composition is
contacted with starch or pulp fiber.
55. The method of claim 50, wherein the glyoxal generating compound is a
compound according to Formula VI:
<IMG>
wherein
p is an integer from 1 to about 1000;
Z is independently selected at each occurrence from the group consisting of
optionally substituted urea, optionally substituted thiourea, optionally
substituted
guanidine, optionally substituted alkylene glycol, optionally substituted
.alpha.,.omega.-
akanediol, optionally substituted poly(ethylene glycol), optionally
substituted
imidazolidin-2-one, and optionally substituted tetrahydro-pyrimidin-2-one;
wherein the aldehyde generating compound according to Formula VI degrades
to generate at least one equivalent of glyoxal when the crosslinking
composition is~
contacted with starch or pulp fiber.
-46-

R5 is hydrogen, alkoxy, hydroxyalkoxy, amino, hydroxy, mono and dialkyl
amino, optionally substituted alkane diol, optionally substituted urea, or
optionally
substituted alkylene glycol; and
R6 is hydrogen, optionally substituted alkyl, optionally substituted alkanoyl,
optionally substituted unblocked glyoxal residue, or blocked glyoxal residues.
56. The method of claim 55, wherein
Z is urea, thiourea, C210.alpha.,.omega.-alkanediol, C2-10alkylene glycol, or
poly(ethyleneglycol) having between 2 and about 100 glycol repeat units;
-47-

Description

CA 02545476 2006-05-09
WO 2005/071162 PCT/US2005/000458
PAPER MAKING PROCESS AND CROSSLINK1NG COMPOSITIONS FOR USE
IN SAME
BACKGROUND OF THE INVENTION
1. Field of the Invention.
The present invention provides methods of manufacturing paper and
paperboard materials having increased strength, and more particularly provides
a
method of making paper and paperboard materials possessing increased wet and
dry
strength. The methods of the invention comprise addition of a crosslinker
composition comprising at least one aldehyde generating compound, or more
preferably a glyoxal releasing compound, which typically is activated during
the
drying process of the paper making process. The aldehyde generating compound,
or
more preferably the glyoxal releasing compound is combined with the dilute
starch
prior to the wet end of the paper making process. In certain other methods of
the
invention the aldehyde generating compound is contacted with-a preformed paper
or
paperboard web formed from a mixture comprising a fiber slurry and a
gelatinized
starch composition.
2. Background.
Industrial starch may be utilized in a wide variety of paper making
applications, such as a coating binder or surface treatment for paper and
paperboard
materials, and as a strength and retention wet end additive in papermaking.
Starch
compositions are frequently prepared as an aqueous dispersion which is capable
of
being added to the pulp slurry. For many commercial applications starch is
gelatinized prior to addition of the starch to the pulp slurry, and may be
carried out by
the starch provider or the paper manufacturer. Gelatinization typically occurs
after
starch granules are dispersed as a slurry in water and the resultant aqueous
slurry is
heated to a temperature of 50° C or more, and more typically to a
temperature of 95°
C or more. In certain gelatinization methods, the starch granules are heated
to a

CA 02545476 2006-05-09
WO 2005/071162 PCT/US2005/000458
temperature of more than 100 °C, such as starch gelatinized using a
commercial jet
cooker or another pressurized steam cooker. Under such conditions starch
grains tend
to absorb water, swell and eventually rupture to allow starch fragments and
molecules
to disperse in the water. This process of rupturing and dispersion is
generally referred
to as "gelatinization" and is an irreversible reaction, resulting in a
relatively thick
starch dispersion:
The crosslinking of starch with multi-functional reagents, which are reactive
with starch hydroxyl groups, is well known. Glyoxal and polyaldehyde compounds
and resins have been previously utilized as crosslinkers. Simple mixing of
glyoxal
with a starch dispersion rapidly affords a gel. However, glyoxal is infinitely
soluble
in water and does not interact efficiently with other chemicals or
compositions,
particularly heterogeneous materials dispersed in small quantities in large
volumes of
water, e.g., such as gelatinized starch molecules or cellulosic fibers present
in the wet-
end of the paper making process. Thus, addition of glyoxal or other low
molecular
weight crosslinkers directly to the wet-end of the papermaking process has not
been
found to provide benefit to end product of the paper making process.
U.S. Patent 6,303,000 issued to Floyd et al. (Floyd'000) discloses gelatinized
starch compositions crosslinked with a glyoxal resin and the use of same in
paper
making. The crosslinked starch composition of Floyd'000 comprise the reaction
product formed by heating starch with a blocked glyoxal resin such as those
resins
recited in U.S. Patent 4,695,606 (Floyd, '606) during the gelatinization
process. The
heating process forms a gelatinized starch that is crosslinked by the glyoxal
resin.
More particularly, Floyd '000 discloses the addition of a crosslinked
gelatinized starch
composition to the wet end of the paper making process. In other words, prior
to
addition to the wet end, the starch is heated with the blocked glyoxal resin
to
gelatinize the starch and induce a crosslinking reaction between the glyoxal
and the
starch. The Floyd '000 patent further discloses that the glyoxal resin can be
pre-mixed
with the starch prior to the gelatinization heating step or added during the'
starch
gelatinization process. Floyd suggests that pre-mixing the starch and blocked
glyoxal
resin prior to the gelation process or addition of the blocked glyoxal resin
during the
gelatinization process, affords superior material having improved shelf
stability.
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WO 2005/071162 PCT/US2005/000458
The Floyd '606 patent describes paper binder compositions comprising a
mixture of an acrylic or vinyl polymer with a blocked glyoxal resins, e.g.,
such as the
reaction product of glyoxal and a urea or a cyclic urea. More particularly,
the blocked
glyoxal resin is a condensation polymer of glyoxal blocked with urea, cyclic
ureas
such as ethylene urea, 4,5-dihydroxyethylene urea and propylene urea,
carbamates,
glycols, or polyols.
In Floyd '000 the addition levels of the gelatinized starch composition
demonstrated to affect a significant improvement in paper or paperboard
strength are
relatively high at the level of 40 1b or more dry starch composition per ton
of dry pulp.
It is well known in the art of papermaking that significant issues may occur
when
relatively high levels of starch are used to produce paper, including high
cost, high
levels of effluent Biological Oxygen Demand (BOD), reduction in paper opacity,
machine deposits, and problems with dewatering and drying the paper or
paperboard
leading to reduced production rates. It would thus be desirable to have paper
strength
compositions that are effective at lower levels of usage.
A variety of polymeric stabilizing agents have been recited which are capable
of stabilizing at lest one aldehyde residue of a plurality of glyoxal
compounds. More
particularly a variety of polyacrylamide or copolymers of acrylamide and an
unsaturated aliphatic carboxylic acid, which have a plurality of glyoxal
equivalents
attached to the polymer chain through pendant amide groups of the acrylamide
residues.
U.S. Patent 3,556,932 teaches poly(acrylamide) substituted with glyoxal, e.g.,
a polymer chain with -C(O)NHCH(OH)CHO side chains.
U.S. Patent 5,543,446 teaches terpolymers composed of (meth)acrylamide
mononomers; unsaturated aliphatic carboxylic acid monomers, and a di-or
polyvinyl
monomer. The terpolymers can be used to increase the wet strength of a paper
web
during the paper making process.
-3-

CA 02545476 2006-05-09
WO 2005/071162 PCT/US2005/000458
International patent publication, WO 00/11046 teaches a copolymer of
acrylamide and an a,(3-unsaturated carboxylic acid which has been modified
with a
dialdehyde such as glyoxal.
Various disclosures have been prepared which teach stabilizing glyoxal with
polyacrylamide and the use of polyacrylamide/glyoxal resins in paper making
processes.
As an alternative approach, it would be desirable to have a crosslinking
composition including a stabilized aldehyde generating compound or a
stabilized
glyoxal compound that is capable of crosslinking starch molecules and/or pulp
fiber
particles upon application of the crosslinking composition to a paper or
paperboard
web. It would also be desirable to provide methods of making paper and
paperboard
with increased strength using such crosslinking compositions.
SUMMARY OF THE INVENTION
The present invention provides storage stabile, crosslinking compositions that
include at least one glyoxal releasing compound or at least one aldehyde
generating
compound. These compounds facilitate a process of manufacturing paper or
paperboard having improved wet and/or dry strength than previous paper or
paperboard manufacturing processes. Preferably, the manufacturing processes of
certain embodiments of the invention provide paper or paperboard materials
with
equivalent strength and a reduced basis weight when compared to paper or
paperboard
materials made with previous paper manufacturing processes.
In accord with the present invention, a method for manufacturing paper and
paperboard materials, the method comprising the steps of
providing a fiber slurry and a gelatinized starcli composition, each of which
is
suitable for use in making paper or paperboard;
providing at least one crosslinker composition comprising at least one
aldehyde generating compound capable of forming at least two or more covalent
bonds to functional groups present in the starch or fiber of the web;
mixing the gelatinized starch composition and the crosslinker composition;
-4

CA 02545476 2006-05-09
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adding the mixture of gelatinized starch composition and crosslinker
composition to the fiber slurry contemporaneously to mixing the gelatinized
starch
composition and the crosslinker composition; and
forming the paper or paperboard sheet.
Preferred crosslinker compositions comprise one or more equivalents of an
aldehyde generating compound typically comprising one or more equivalents of
at
least one compound having two or more aldehyde resuides. Typically preferred
aldehyde generating compounds of the invention include those compounds
according
to any one of Formula I, II, III, VI, V or VI.
Other aspects of the invention are discussed infra.
For purposes of the present invention, the term "self retaining starch" means
any starch, that through its functionality, has the property of being retained
effectively
in the paper or paperboard web during the process of sheet consolidation
during the
papermaking process. Though not limited to the general description, this
usually
requires that the starch have a net cationic charge for retention on the
generally
anionic fibers used to make paper and paperboard.
Thus, a "self retaining gelatinized starch" is added to the papermaking slurry
at some point before consolidation of the paper web and is substantially
retained or
adsorbed onto the fiber components of the slurry and becomes a component of
the
paper or paperboard . -
For the purposes of the present invention, the term "aldehyde generating
compound" refers to materials that degrade at ambient or elevated temperatures
upon
exposure to starch, gelatinized starch, or pulp fiber to generate compounds
containing
two or more reactive aldehyde residues that are then available for reaction
with
functional groups that generally react in an aqueous environment with aldehyde
groups. Moreover, the term aldehyde generating compound includes those
compounds capable of generating polyaldehyde compounds upon degredation and
compounds capable of generating one or more aldehyde groups in sequence such
that
-5-

CA 02545476 2006-05-09
WO 2005/071162 PCT/US2005/000458
two or more covalently connected aldehyde residues are generated during the
depredation of the aldehyde generating compound. Particularly preferred
aldehyde
generating compounds release glyoxal or generate one or two aldehyde groups
which
are derived from glyoxal.
For the purposes of the present invention, the term "glyoxal releasing
compound" refers to materials that degrade at ambient or elevated temperatures
upon
exposure to starch, gelatinized starch, or pulp fiber to generate compounds
containing
reactive glyoxal moieties that are then available for reaction with functional
groups
that generally react in an aqueous environment with glyoxal. In general,
glyoxal
releasing compounds are a subset of aldehyde generating compounds.
For the purposes of the present invention, the term "blocked aldehyde residue"
refers to structures in which at least one aldehyde group is hindered from
forming free
or active aldehyde groups under storage or wet end paper making conditions.
Similarly, the term "blocked glyoxal residue," as used herein, refers to
structures in
which the glyoxal generating group is hindered from forming a free or active
aldehyde group under the current conditions present. The term "unblocked
glyoxal
residue," as used herein, refers to structures in which at least one glyxoal
aldehyde
residue is present as a reactive aldehyde group, i.e., a CHO group.
For the purposes of the present invention, the term "stabilizing agent" refers
to
any compound or combination of compounds capable of forming a linear,
branched,
or cyclic structure which comprises one or more equivalents of glyoxal as a
part of the
linear, branched or cyclic structure or as a substituent thereof. Preferred
stabilizing
agents are capable of masking, blocking or otherwise protecting one, or
preferably,
two aldehyde functional groups of glyoxal from undergoing undesired reactions
prior
to the drying step of the paper making process.
For the purposes of the present invention, the term "aldehyde blocking agent"
refers to any compound or combination of compounds capable of masking,
blocking
or otherwise protecting an aldehyde functional group and preferably are
capable of
masking or blocking aldehyde functional groups in an aqueous environment.
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Typically preferred aldehyde blocking agents release or unmask the akdehyde
group
at elevated temperatures such as the temperature used to dry paper or
paperboard.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a method for manufacturing paper or
paperboard sheet with increased strength, the method comprising the steps of
providing a fiber slurry and a gelatinized starch composition, each of which
is
suitable for use in making paper or paperboard;
providing at least one crosslinker composition comprising at least one
aldehyde generating compound capable of forming at least two or more covalent
bonds to functional groups present in the starch or fiber of the web;
mixing the gelatinized starch composition and the crosslinker composition;
adding the mixture of gelatinized starch composition and crosslinker
composition to the fiber slurry contemporaneously to mixing the gelatinized
starch
composition and the crosslinker composition; and
forming the paper or paperboard sheet.
In preferred methods of manufacturing paper comprising pre-mixing of a
gelatinized starch and the crosslinker composition and addition of the mixture
to a
figure slurry, the gelatinized starch composition and the crosslinker
composition are
mixed together in a batch process or in a continuous flow process prior to
addition to
the fiber slurry. In certain preferred methods of the invention the mixing of
the
gelatinized starch composition and the crosslinker composition occurs within
less than
about 1 hour prior to addition to the fiber slurry, or more preferably less
than about 30
minutes or less than 10 minutes prior to addition to the fiber slurry. In
certain
particularly preferred embodiments, the gelatinized starch composition and the
crosslinker composition are mixed together less than about 5 minutes or less
than
about 1 minute prior to addition to the fiber slurry.
The invention also provides a method for manufacturing paper or paperboard
sheet with increased strength, the method comprising the steps of

CA 02545476 2006-05-09
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providing a fiber slurry and a gelatinized starch composition, each of which
is
suitable for use in making paper or paperboard;
providing at least one crosslinker composition comprising at least one
aldehyde generating compound capable of forming at least two or more covalent
bonds to functional groups present in the starch or fiber of the web;
preparing a paper or paperboard web comprising pulp fiber and at least one
starch prepared by mixing the gelatinized starch composition and the fiber
slurry;
contacting the web with the crosslinker composition under conditions
conducive to formation at least two or more covalent bonds to functional
groups
present in the starch or fiber of the web.
Suitable crosslinking compositions suitable far use in the paper making
methods of the present invention include one or more of the following
compositions,
each of which comprises one or more compounds according to Formula I, II-a,
II, III,
IV, V, or VI and may optionally further comprise one or more aldehyde blocking
agents.
Preferred methods for manufacturing paper or paperboard sheet provided by
the present invention are suitable for the preparation of paper or paperboard
sheets
which have increased strength. Typically the methods of the invention comprise
the
steps of
providing a fiber slurry and a gelatinized starch composition, each of which
is
suitable for use in making paper or paperboard;
providing at least one crosslinker composition comprising at least one
aldehyde generating compound capable of forming at least two or more covalent
bonds to functional groups present in the starch or fiber of the web;
mixing the gelatinized starch composition and the crosslinker composition;
adding the mixture of gelatinized starch composition and crosslinker
composition to the fiber slurry contemporaneously to mixing the gelatinized
starch
composition and the crosslinker composition; and
forming the paper or paperboard sheet.
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Typically the gelatinized starch composition and the crosslinker composition
can be mixed in any fashion such that the two reagents from an admixture prior
to
addition to the paper slurry. Typically, the gelatinized starch composition
and the
crosslinker composition are admixed in either a continuous flow process during
the
process of addition to the paper slurry or the reagents are admixed in a batch
process
prior to addition of the mixture to the paper slurry in aliquots.
In certain preferred paper making methods of the invention the gelatinized
starch composition and the crosslinker composition are introduced into the
paper
slurry using manifold capable of delivering each reagent continuously or in
regularly
distributed portions over a specified time interval., More preferably, the
gelatinized
starch composition and the crosslinker composition are admixed in a mixing
chamber
which has been incorporated into the manifold which transfers gelatinized
starch
composition and the crosslinker composition from the reagent containers to the
paper
slurry delivered to the "head box" of the paper manufacturing mill. In certain
other
methods of theinvention, the aldehyde generating compound may be administered
to a
fiber web during the formation or initial drying steps of the paper or
paperboard
making process. Typically preferred application methods include spraying of
the
aldehyde generating compound onto the fiber web.
In certain preferred processes of the invention the gelatinized starch
composition and the crosslinker composition are admixed together in a
continuous
flow process prior to addition to the fiber slurry. Any device or mixing
apparatus
used to mix two or more fluids from two or more fluid streams to form a single
fluid
mixture are suitable for use in the methods of the present invention.
Typically the
manifold delivering the gelatinized starch composition and the crosslinker
composition to the fiber slurry are combined either in a pre-mixing chamber or
the
manifold pipes for the gelatinized starch composition and the crosslinker
composition
are joined by a "T" joint, a "Y" joint or another branch point capable of
mixing two or
more fluid flows into a single fluid effluent.
In certain preferred methods of the invention, the gelatinized starch
composition and the crosslinker composition are mixed together less than about
1
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CA 02545476 2006-05-09
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hour prior to addition to the fiber slurry. More preferably, the gelatinized
starch
composition and the crosslinker composition are mixed together less than about
30
minutes prior to addition to the fiber slurry or less than about 10 or about 5
minutes
prior to addition to the fiber slurry.
Other preferred methods for manufacturing paper or paperboard sheet
provided by the present invention are suitable for the preparation of paper or
paperboard sheets which have increased strength. Typically the methods of the
invention comprise the steps of
providing a fiber slurry and a gelatinized starch composition, each of which
is
suitable for use in making paper or paperboard;
providing at least one crosslinker composition comprising at least one
aldehyde generating compound capable of forming at least two or more covalent
bonds to functional groups present in the starch or fiber of the web;
preparing a paper or paperboard web comprising pulp fiber and at least one
starch prepared by mixing the gelatinized starch composition and the fiber
slurry;
contacting the web with the crosslinker composition under conditions
conducive to formation at least two or more covalent bonds to functional
groups
present in the starch or fiber of the web.
Crosslinking compositions of the present invention comprise an aqueous
solution or dispersion containing at least one aldehyde generating compound or
glyoxal releasing compound that are suitable for imparting increased wet
and/or dry
strength to paper or paperboard. Preferred aqueous crosslinking compositions
of the
invention comprise at least one glyoxal releasing compound comprising at least
one
blocked or unblocked glyoxal residue which is capable of generating reactive
aldehyde groups and/or releasing glyoxal upon contacting the glyoxal releasing
compound with starch, gelatinized starch, pulp fiber or a combination thereof.
Typically preferred aqueous crosslinker compositions of the invention are
storage
stable, particularly when stored at a temperature of 40°C or less.
The crosslinker compositions of the present invention are particularly useful
for manufacturing paper or paperboard sheet having increased strength at the
same
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basis weight, or having the same strength with reduced basis weight. The
methods for
manufacturing paper or paperboard typically comprise providing a paper or
paperboard web; contacting the web with at least one crosslinker composition
of the
present invention; and heating the paper or paperboard web at a temperature
which is
sufficient to dry the paper. Typically the crosslinker composition is applied
to the
web before the drying step or after the web has been partially dried. The
paper
produced by the manufacturing methods of the invention may have various
desirable
physical properties depending upon the order of the crosslinker composition
addition
step and the drying step.
Preferred crosslinker compositions for use in the methods of strengthening
paper or paperboard provided by the present invention include those
crosslinker
compositions comprising:
an aqueous media; and
a monomeric or oligomeric aldehyde generating compound comprising
at least one equivalent of a dialdehyde or polyaldehyde compound; and
between 0.25 and about 5 equivalents of a stabilizing agent which is
capable of reacting with two or more aldehyde residues.
In certain particularly preferred crosslinker compositions are substantially
free of materials capable of irreversibly reacting with aldehyde generating
compounds
of the crosslinker composition. More preferably, the crosslinker compositions
of the
invention do not comprise starch or gelatinized starch. The invention further
provides
crosslinker compositions which are storage stable in the absence of starch,
gelatinized
starch, or pulp fiber for at least one week and reacts at a temperature of
less than
100°C to form covalent bonds with starch, gelatinized starch or pulp
fiber in less than
an hour.
In other preferred embodiments, the invention provides crosslinker
composition which comprise an aldehyde generating compound which releases
glyoxal.
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In certain preferred embodiments, the crosslinker composition comprises an
aldehyde generating compound having at least one stabilizing agent which is
selected
from linear, branched or cyclic organic molecules having at least two
functional
groups capable of blocking an aldehyde residue. Typically preferred
stabilizing
agents are selected from the group consisting of optionally substituted urea,
optionally
substituted thiourea, optionally substituted guanidine, optionally substituted
alkylene
glycol, optionally substituted a,~-akanediol, optionally substituted
polyethylene
glycol), optionally substituted imidazolidin-2-one, optionally substituted
tetrahydro-
pyrimidin-2-one, and combinations thereof.
In certain particularly preferred embodiments, the stabilizing agent has a
molecular weight of less than 1000 g/mol. More preferably, the stabilizing
agent
having a molecular weight of 1000g/mol or less is selected from optionally
substituted
urea, optionally substituted thiourea, optionally substituted guanidine,
optionally
substituted alkylene glycol, optionally substituted a,~-akanediol, optionally
substituted polyethylene glycol), optionally substituted imidazolidin-2-one,
optionally substituted tetrahydro-pyrimidin-2-one, and combinations thereof.
In yet other embodiments, the present invention provides crosslinking
compositions which further comprise one or more aldehyde blocking compounds
which are present in the crosslinking composition at between about 0 and about
20
molar % of the aldehyde generating compound. Certain preferred aldehyde
blocking
compounds are selected from the group consisting of C1_2oalcohols,
CZ_2oalkylene
glycols, and C1_2oalkylamines, and the like. Particularly preferred aldehyde
blocking
compound include methanol, ethanol, propanol, ethylene glycol, and propylene
glycol, and the like.
Certain preferred crosslinker compositions, which are suitable for use in the
paper manufacturing methods of the invention, comprise an aldehyde generating
compound or a glyoxal generating compound which is a compound according to
Formula I:
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OH OH
Z /O
O~ Z
OH OH
n' n
m I
wherein
Z is monovalent or divalent urea, monovalent or divalent a,c~-CZ_$alkanediol,
C2_8alkylene glycol, polyethylene glycol) having a molecular weight of less
than
about 20,000, w-amino-a-C2_galkanol or Z is a 5 to 7 member optionally
substituted
heterocyclic group having one ring nitrogen atom, at least one additional ring
heteroatom selected from N, O, or S, and zero or one oxo substitutents;
n is 0, 1, or 2;
mis0orl;
n' = n if m = 1 or n' = 0 if m = 0, wherein at least one of m and n is not
zero.
Other preferred crosslinker compositions, which are suitable for use in the
paper manufacturing methods of the invention, comprise an aldehyde generating
compound or a glyoxal releasing compound which is a compound according to
Formula II:
/B\
R~ A R2 II
wherein
A is an optionally substituted methylene group, an optionally substituted CZ_
4alkylene group, or a single bond;
B is carbonyl, thiocarbonyl, or an optionally substituted 1,2-ethylene
residue;
X~ and Xa are independently selected from the group consisting of oxygen and
NR3;
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Rl and R2 are independently selected from the group consisting of hydrogen,
hydroxy, optionally substituted C~_2oalkyl, optionally substituted
C~_ZOalkoxy,
optionally substituted urea, optionally substituted thiourea, or
Rl and Rz, taken in combination, form a N,N'-divalent urea;
R3 is independently selected at each occurrence of R3 from the group
consisting of hydrogen, 1-hydroxy-ethan-2-al-1-yl group, or a blocked glyoxal
residue.
Certain preferred crosslinker compositions of the present invention comprise
an aldehyde generating compound or a glyoxal releasing compound which is a
compound according to Formula II-a:
/B\
X1 X2
R~ A Rz II-a
wherein
A is an optionally substituted methylene group, an optionally substituted Cz_
4alkylene group, or a single bond;
B is carbonyl, thiocarbonyl, or an optionally substituted 1,2-ethylene
residue;
Xl and XZ are independently selected from the group consisting of oxygen and
NR3;
Rl and Rz are independently selected from the group consisting of hydrogen,
hydroxy, optionally substituted C~_ZOalkyl, optionally substituted
C1_ZOalkoxy,
optionally substituted urea, optionally substituted thiourea, or
RI and R2, taken in combination, form a N,N'-divalent urea;
R3 is independently selected at each occurrence of R3 from the group
consisting of hydrogen, optionally substituted C~_zoalkyl, and unblocked and
blocked
glyoxal residues, where unblocked glyoxal residue is a 1-hydroxy-2-ethanal-1-
yl
group and the blocked glyoxal residue is a 1-hydroxy-2-(protected aldehyde
resxdue)-
ethan-1-yl group; or
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R3 is a 1,2-dihydroxyethylene residue coupled to two rings according to
Formula I; and
wherein the aldehyde generating compound according to Formula I degrades
to generate at least one equivalent of glyoxal when the crosslinking
composition is
contacted with starch or pulp fiber.
Preferred compounds of Formula II or II-a, which are suitable for use in the
crosslinking compositions of the invention include those compounds in which:
Rl and R2 are independently selected from the group consisting of hydrogen,
hydroxy, methanol, ethanol, urea, or
RI and R2, taken in combination, form a N,N'-divalent urea;
R3 is independently selected at each occurrence of R3 from the group
consisting of hydrogen, methyl, and ethyl, or
R3 is an unblocked glyoxal residue or a blocked glyoxal residue selected from
the group consisting of 1,2-dihydroxy-2-(C~_4-alkoxy)-ethan-1-yl, 1,2-
dihydroxy-2-(3-
hydroxypropoxy)-ethan-1-yl, and 1,2-dihydroxy-2-(2-hydroxypropoxy)-ethan-1-yl.
Other preferred compounds of Formula II or II-a, which are suitable for use in
the crosslinking compositions of the invention include those compounds in
which:
Xl and X2 are NR3;
A is a single bond;
B is a carbonyl or thiocarbonyl group; and
Rl and RZ are independently selected from hydroxy, C~_6alkoxy, or blocked
glyoxal residues.
Still other preferred compounds of Formula II or II-a, which are suitable for
use in the crosslinking compositions of the invention include those compounds
in
which:
X1 and XZ are NR3;
A is a 1,1-C1_6alkylene group;
B is a carbonyl or thiocarbonyl group;
R~ and RZ are independently selected from hydrogen, hydroxy, or C~_6alkoxy,
and
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R3 is an unblocked glyoxal residue or a blocked glyoxal residue selected from
the group consisting of 1,2-dihydroxy-2-(C~_ø-alkoxy)-ethan-1-yl, 1,2-
dihydroxy-2-(3-
hydroxypropoxy)-ethan-1-yl, and 1,2-dihydroxy-2-(2-hydroxypropoxy)-ethan-1-yl.
Other preferred aldehyde generating compounds provided by the invention
which are suitable for use in the methods of the invention comprise
substituted
triaminoheteroaromatic and substituted triaminobenzene compounds according to
Formula III:
I5 14
/N X~ N
Ra ~ ERs
Xs ~ X2
N
Rs/ \ R4 III
wherein
each of Xl, X2, and X3 are independently selected from the group consisting of
CH or N; and
R4 and RS are independently selected at each occurrence of Ra and RS in
Formula III from the group selected from hydrogen, a 1-hydroxy-ethan-2-al-1-yl
group, or a blocked glyoxal residue; or
one or more occurrences of NR4R5 in Formula III, taken in combination form
an optionally substituted N-piperazinyl residue.
Particularly preferred compounds of Formula III include 1, 3, 5-triazine
compounds, e.g., compounds of Formula III in which each of Xl, X2, and X3 is
nitrogen.
Other preferred compounds of Formula III include those compounds in which
one or more, or preferably each occurrence of NR4R5, taken in combination,
forms an
optionally substituted N-2,3,5,6-tetrahydroxypiperazinyl residue. Particularly
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preferred compounds of Formula III, in which NR4R5, taken in combination,
forms a
N-2,3,5,6-tetrahydroxypiperazinyl residue include compounds of Formula IV:
OH
R6 HO /R6
'N
/X~ N
HO ~ OOH
OH X3 ~ X2 OH
HO N OH
HO N OH
Rs IV
wherein '
each of Xl, X2, and X3 are independently selected from the group consisting of
CH or N; and
R6 is independently selected at each occurrence from the group selected from
optionally substituted alkyl, optionally substituted carboxamide.
Preferred aldehyde generating compounds of formula IV include those
compounds in which R6 is independently selected at each occurrence from -
C(O)NH2
or -C(O)NHCH(OH)CHO.
Yet other preferred aldehyde generating compounds which are suitable for use
in the methods of manufacturing paper provided by the invention include those
compounds according to V:
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R3 ~N'R4 N~B~N~Rs
wR2 R~ wA wR2
m V
wherein
m is an integer from 0 to about 1000;
A is an optionally substituted methylene group, an optionally substituted Cz_
4alkylene group, or a single bond;
B is carbonyl, thiocarbonyl, or an optionally substituted 1,2-ethylene
residue;
Rl and Rz are independently selected from the group consisting of hydrogen,
hydroxy, optionally substituted C1_zoalkyl, optionally substituted
C1_zoalkoxy,
optionally substituted urea, optionally substituted thiourea, or
Rl and Rz, taken in combination, form a N,N'-divalent urea;
R3 is independently selected at each occurrence of R3 from the group
consisting of hydrogen, optionally substituted C~_zoalkyl, and unblocked and
blocked
glyoxal residues, where unblocked glyoxal residue is a 1-hydroxy-2-ethanal-1-
yl
group and the blocked glyoxal residue is a 1-hydroxy-2-(protected aldehyde
residue)-
ethan-1-yl group; or
R4 is a 1,2-dihydroxyethylene residue; or
R4 is a telechelic oligiomer comprising 2n+1 glyoxal residues alternating with
n groups selected from the group consisting of a,w-alkane diols, alkylene
glycols, and
polyethylene glycol); and
n is an integer of from 0 to about 100;
wherein the aldehyde generating compound according to Formula II degrades
to generate at least one equivalent of glyoxal when the crosslinking
composition is
contacted with starch or pulp fiber.
Other preferred compounds of Formula I, which are suitable for use in the
crosslinking compositions of the invention include those compounds according
to
Formula VI:
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R6 Z Rs
VI
wherein
p is an integer from 1 to about 1000;
Z is independently selected at each occurrence from the group consisting of
optionally substituted urea, optionally substituted thiourea, optionally
substituted
guanidine, optionally substituted alkylene glycol, optionally substituted a,t~-
akanediol, optionally substituted polyethylene glycol), optionally substituted
imidazolidin-2-one, and optionally substituted tetrahydro-pyrimidin-2-one;
wherein the aldehyde generating compound according to Formula VI degrades
to generate at least one equivalent of glyoxal when the crosslinking
composition is
contacted with starch or pulp fiber.
R5 is hydrogen, alkoxy, hydroxyalkoxy, amino, hydroxy, mono and dialkyl
amino, optionally substituted alkane diol, optionally substituted urea, or
optionally
substituted alkylene glycol; and
R6 is hydrogen, optionally substituted alkyl, optionally substituted alkanoyl,
optionally substituted unblocked glyoxal residue, or blocked glyoxal residues.
Certain preferred aldehyde generating compounds or glyoxal generating
compounds according to Formula VI, include those compounds wherein
Z is urea, thiourea, CZ_ioa,w-alkanediol, C2_loalkylene glycol,
poly(ethyleneglycol) having between 2 and about 100 glycol repeat units.
Certain particularly preferred aldehyde generating compounds and glyoxal
generating compound, which are suitable for use in the crosslinking
compositions of
the present invention, include compounds of the formulae:
HO ~ OH
HN NH O~N N~O
~OH HO~OH
HO
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H ~O
HO O OH O
~N O OH H
O~N N N OH ~ N NH2
H2N N
HO~OHHO OH H
OH OH
OH O OH
O O~O O~O
O~N~N~ ~n
H H n = 2, 3, 4, or 5
OH OH
OH OH OH OH
O HN
O ~O O~O PEG~O~O
OH OH OH H
p O~ HON N~OH
OH H
OH H
H2N~N N~NH2
H OH
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CA 02545476 2006-05-09
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HzN
HO N OH
HO ~N OH
H2N' \-O
/O
HO NH OH OH HN OH
~ OH HO
O"N O
HO N~N~N~OH
HO HO\ ~ OH N~N OH
~O ~ 1~'O
HO N\ /N\ /N\ ~O HO N OH
N~IN IOH HO N OH
HN
O~
~OH
In accord with the present invention, a method for manufacturing paper and
paperboard materials, the method comprising the steps of
providing a paper or paperboard web comprising pulp fiber and at least one
starch;
contacting the web with at least one crosslinker composition comprising at
least one aldehyde generating compound capable of forming at least two or more
covalent bonds to functional groups present in the starch or fiber of the web.
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In certain preferred methods of the invention, a paper sheet is prepared by
the
method of manufacture. In other preferred methods of the invention, a
paperboard
sheet is prepared by the manufacturing method.
In certain embodiments, the crosslinker composition is contacted with the web
before the drying process commences or after partial drying of the web. In
certain
preferred embodiments, it may be beneficial to contact the web with one or
more
crosslinker compositions at various times in the paper making process. For
example,
one or more different crosslinker compositions are contacted with the web
prior to
commencing the,drying step and second crosslinker composition, which may be
the
i
same or different from the first crosslinker composition is contacted with the
web
after a first drying step partially dries the sheet.
Typically the methods of manufacture provide at least one of increased wet
strength or increased dry strength of the web or the paper or paperboard sheet
prepared by the method of manufacture.
Preferred crosslinker compositions which are suitable for use in the methods
of the present invention include any of the crosslinker compositions provided
herein
or a mixture of two or more such crosslinker compositions added simultaneously
or
separately to the paper making process. Certain preferred crosslinker
compositions
suitable for use in the paper or paperboard making methods of the present
invention
include those compositions comprising glyoxal generating compounds or at least
one
compound according to Formula I, II, III, IV, V, VI or a subformula thereof.
As used herein, "alkyl" is intended to include both branched and straight-
chain
saturated aliphatic hydrocarbon groups, having the specified number of carbon
atoms.
Examples of alkyl include, but are not limited to, methyl, ethyl, n-propyl, i-
propyl, n-
butyl, s-butyl, t-butyl, rz-pentyl, and s-pentyl. Preferred alkyl groups are
C1-6 alkyl
groups. Especially preferred alkyl groups are methyl, ethyl, propyl, butyl,
and 3-
pentyl. The term C~_4 alkyl as used herein includes alkyl groups consisting of
1 to 4
carbon atoms, which may contain a cyclopropyl moiety. Suitable examples are
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methyl, ethyl, and cyclopropylmethyl. The term "alkyl" is also intended to
include
cycloalkyl and cycloalkylalkyl groups where there term "cycloalkyl" is used as
defined herein.
"Cycloalkyl" is intended to include saturated ring groups, having the
specified
number of carbon atoms, such as cyclopropyl, cyclobutyl, cyclopentyl, or
cyclohexyl.
Cycloalkyl groups typically will have 3 to about 8 ring members.
"Alkenyl" is intended to include hydrocarbon chains of either a straight or
branched configuration comprising one or more unsaturated carbon-carbon bonds,
which may occur in any stable point along the chain, such as ethenyl and
propenyl.
Alkenyl groups typically will have 2 to about 8 carbon atoms, more typically 2
to
about 6 carbon atoms.
I S "Alkynyl" is intended to include hydrocarbon chains of either a straight
or
branched configuration comprising one or more carbon-carbon triple bonds,
which
may occur in any stable point along the chain, such as ethynyl and propynyl.
Alkynyl
groups typically will have 2 to about 8 carbon atoms, more typically 2 to
about 6
carbon atoms.
"Alkoxy" represents an alkyl group as defined above with the indicated
number of carbon atoms attached through an oxygen bridge. Examples of alkoxy
include, but are not limited to, methoxy, ethoxy, n-propoxy, i-propoxy, n-
butoxy, 2-
butoxy, t-butoxy, n-pentoxy, 2-pentoxy, 3-pentoxy, isopentoxy, neopentoxy, h-
hexoxy, 2-hexoxy, 3-hexoxy, and 3-methylpentoxy. Alkoxy groups typically have
1
to about 8 carbon atoms, more typically I to about 6 carbon atoms.
In the papermaking process wood pulp is prepared, bleached if required,
cleaned, and run through a series of beaters or refiners until it is a fine
slush. At this
point fillers and other additives, such as the gelatinized starch compositions
of the
invention, can be mixed in. When preparation is complete, the slush is pumped
onto a
fast-moving wire screen where it becomes consolidated into a continuous web or
sheet of paper or paperboard.
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As the consolidating web travels with the moving wire, excess water is
drained away leaving a crude paper or paperboard sheet. The sheet is then
squeezed
between rollers or presses to remove some of the remaining water and to ensure
uniform thickness and smoothness. Finally, the web is run over a series of
heated
rollers or heating devices to remove most of the remaining water. The paper
may be
"finished" in any number of ways, including but not limited to, surface
treatments,
calendaring, or coating. The finished paper is spooled onto 'parent rolls'
termed the
reel.
EXAMPLES
The present invention is further illustrated by the following examples which
should not be construed as limiting in any way. The contents of all cited
references
(including literature references, issued patents, published patent
applications) as cited
throughout this application are hereby expressly incorporated by reference.
The
practice of the present invention will employ, unless otherwise indicated,
conventional techniques, which are within the skill of the art. Such
techniques are
explained fully in the literature.
In the following example, laboratory handsheets were prepared using the MK
sheet forming device in semi-automatic mode. Pulp was beaten to 300 CSF
(Canadian Standard Freeness) using a laboratory beater. Additions were made to
a
1% slurry of the pulp prior to addition to the headbox. Sheets (12 x 12") were
formed
using conventional practice, pressed, and dryed at 120°C using 2 passes
through a
felted rotating cylinder dryer. A pass is one rotation around the heated drum.
The
speed of this rotation is adjustable. For this study.the rotation took 1
minute. The pulp
slurries were prepared in ordinary tap water without pH adjustment. Old
Corrugated
Containers (OCC) was obtained from commercial box clippings.
EXAMPLE 1: Preparation of a mixture of 3,4-dihydroxy-imidazolidin-2-one and at
least one aldehyde blocking compound
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A 1000m1 flask was charged with glyoxal (40% in water, 145 grams, 1 mole)
and the contents of the flask were stirred and warmed to 55°C. Urea
(50% in water,
120 grams, 1 mole) was added to the stirred glyoxal solution over four hours
at 55 °C.
To this mixture propylene glycol (38 grams, 0.5 moles) and a catalytic amount
of
sulfuric acid (98%, typically about 1 gram) was added. The reaction mixture
was then
heated to 70°C for two hours to generate the product, of which the
predominant
reaction produce had the structure, as follows:
O
HN NH
HO~ OH
EXAMPLE 2: Preparation of a Cyclic Glyoxal with Pendant Blocked Glyoxal
Residues.
A 1000m1 flask was charged with glyoxal (40% in water, 435 grams, 3 moles)
and the contents of the flask were stirred and warmed to 55°C. Urea
(50% in water,
120 grams, 1 mole) was added to the stirred glyoxal solution over two hours at
55 °C.
A catalytic amount of sulfuric acid (98%, typically about 1 gram) was added to
the
reaction mixture to accelerate the cyclization reaction. The reaction mixture
was
allowed to stir for four hours and then propylene glycol (152 grams, 2 moles)
was
added. The reaction mixture was then heated to 70°C for two hours to
generate the
product, of which the predominant reaction produce had the structure, as
follows:
OH HO O OH OH
O ~ O
N N
OH ~ OH
HO OH
EXAMPLE 3: Dry Strength Evaluation Of Paper Manufactured With A Gelatinized
Starch Composition Comprising The Compound Of Example 1 As The Glyoxal
Releasing Compound.
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A handsheet study demonstrating strength improvements included one
handsheet set prepared without a starch additive and three sets of sheets with
different
starch compositions. Handsheets are 15 gm (12 in x 12 in). Sample 3A was a
control
OCC .furnish with no additives. Sets 3B thru 3D were made with the identical
furnish
and conditions but a different starch additive was used in each set.
Set 3B contained a cationic pregelatinized potato starch (Penford PAR
6048AR, available from Penford Products, Inc.), at 10 lb/ton and is referred
to herein
as the "starch'only" control. Set 3C was prepared with a gelatinized starch
composition comprising a mixture of Penford PAR 6048AR and the glyoxal
generating compound provided in Example 1. The mixture was prepared by mixing
the glyoxal generating compound into the Penford PAR 6048AR (25%) at
32°C over
1 hour with agitation. The resulting mixture had a solids content of 23.7%. by
weight
Set 3D was prepared using the same gelatinized starch composition as was
used in Set 3C except that the gelatinized starch composition was prepared by
mixing
the glyoxal generating compound from Example 1 into a Penford PAR 6048AR at
90°C over 30 minutes with agitation (pre-reaction process). In both 3C
and 3D the
glyoxal generating compound was blended into Penford PAR 6048AR at 10% by
weight dry on dry. The combination was added to the OCC slurry at 10 lb/ton.
Table I
Sample Description Dry Tensile Shelf Life
3A fiber control46.04 NA
3B starch control47.26 6 months
3C cold blend 57.65 3 months
3D pre-reacted 55.72 3 weeks
The results demonstrate that the dry strength of the paperboard was improved
when the glyoxal generating compound was added to the starch. Performance in
terms of strength development and stability are best when the material is
added to the
starch under mild conditions (example 3C). Moreover, treatment of the
gelatinized
starch composition under the conditions of the pre-reaction process reduces
the
stability of the starch composition.
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EXAMPLE 4: Dry Strength Evaluation of Paper Manufactured With A Gelatinized
Starch Composition Comprising The Compound Of Example 2 As The Glyoxal
Generating Compound.
A handsheet study demonstrating strength improvements included one
handsheet set prepared without a starch additive and three sets of sheets with
different
starch compositions. Handsheets are 15 gm (12 in x 12 in). Sample 4A was a
control
OCC furnish with no additives. Sets 4B thru 4D were made with the identical
furnish
and conditions but a different starch additive was used in each set.
Set 4B contained a cationic pregelatinized potato starch (Penford PAR
6048AR), at 10 lb/ton and is referred to herein as the "starch only" control.
Set 4C
was prepared with a gelatinized starch composition comprising a mixture of
Penford
PAR 6048AR and the glyoxal generating compound provided in Example 2. The
mixture was prepared by mixing the glyoxal generating compound into the
Penford
PAR 6048AR (25%) at 32°C over 1 hour with agitation. The resulting
mixture had a
solids content of 23.7% by weight.
Set 4D was prepared using the same gelatinized starch composition as was
used in Set 4C except that the gelatinized starch composition was prepared by
mixing
the glyoxal generating compound from Example 2 into Penford PAR 6048AR at
90°C
over 30 minutes with agitation (pre-reaction process). In both 4C and 4D the
glyoxal
generating compound was blended into Penford PAR 6048AR at 10% by weight dry
on dry. The combination was added to the OCC slurry at 10 lb/ton.
Table II
Sample Description Dry TensileShelf Life
4A fiber control46.04 NA
4B starch control47.26 6 months
4C cold blend 52.47 1.5 days
4D pre-reacted ND < 1 hour
The results demonstrate that the dry strength of the paperboard was improved
when the glyoxal generating compound of Example 2 was added to the gelatinized
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starch composition. Performance in terms of strength development and stability
were
best when the material was added to the starch under the mild conditions
(example
4C). Treatment of the gelatinized starch composition with harsh conditions,
such as
those of set 4D, resulted in a gelatinized starch composition that was not
usable for
use in commercial applications, due in part to a short shelf life.
EXAMPLE 5 Preparation of Cyclic Amide with Pendent Blocked Glyoxal Units
Sodium bicarbonate (7.5 grams) was introduced into a sealed nitrogen filled
round bottom flask fixed with heating, cooling, reflux, distillation, pH
probe,
temperature probe and constant pressure addition apparatus. Formaldehyde (37%
in
water, 172 grams, 2 moles) was then added to the flask. Propionaldehyde (116
grams,
2 moles) was then slowly added to the reaction mixture over 2 hours at
30°C. Upon
complete addition of the propionaldehyde, the reaction solution was heated to
45°C
for 4 hours. Urea (120grs (2 moles)) was then added and the temperature of the
reaction mixture increased to 60°C for 2 hours. Residual raw materials
and a small
amounts of reaction by-products were then removed from the reaction flask by
vacuum distillation. Sulfuric acid (98%, 6.25 grams) was added to the material
remaining in the flask after distillation and the reaction mixture was held at
60°C for 4
hours.
Glyoxal (40% by weight in water; 290 grams, 2 moles) and propylene glycol
(152 grams, 2 moles) were added sequentially at 55°C to the reaction
mixture. The
reaction mixture was allowed to stir for an hour after complete addition of
each
reagent, e.g., glyoxal and propylene glycol.
The reaction mixture was returned to room temperature and the pH was
adjusted to about 6.5 by addition of sodium bicarbonate. The predominate
glyoxal
generating compound formed by the reaction is represented by the structure, as
follows:
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CH3
CH3
OH
EXAMPLE 6: Dry Strength Evaluation of Paper Manufactured With A Gelatinized
Starch Composition Comprising The Compound Of Example 5 As The Glyoxal
Releasing Compound.
A handsheet study demonstrating strength improvements included one
handsheet prepared without a starch additive and three sets of sheets with
different
starch compositions. Handsheets are 15 gm (12 in x 12 in). Sample 6A was a
control
OCC furnish with no additives. Sets 6B thru 6D were made with the identical
furnish
and conditions but a different starch additive was used in each set.
Set 6B contained a cationic pregelatinized potato starch (Penford PAR
6048AR), at 10 lb/ton and is referred to herein as the "starch only" control.
Set 6C
was prepared with a gelatinized starch composition comprising a mixture of
Penford
PAR 6048AR and the glyoxal generating compound provided in Example 5. The
mixture was prepared by mixing the glyoxal generating compound into the
Penford
PAR 6048AR (25%) at 32°C over 1 hour with agitation. The resulting
mixture had a
solids of 23.7%.
Set 6D was prepared using the same gelatinized starch composition as was
used in Set 6C except that the gelatinized starch composition was prepared by
mixing
the glyoxal generating compound from Example 5 into Penford PAR 6048AR at
90°C
over 30 minutes with agitation (pre-reaction process). In both 6C and 6D the
glyoxal
generating compound was blended into Penford PAR 6048AR at 10% by weight dry
on dry. The combination was added to the OCC slurry at 10 lb/ton.
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Table III
Sample Description Dry Tensile ~~ Shelf
Life
6A fiber control46.04 NA
6B starch control47.26 6 months
6C cold blend 57.47 1 month
6D pre-reacted 56.41 5 days
EXAMPLE 7 Production Scale Paper Manufactured using A Gelatinized Starch
Composition In Which The Glyoxal Generating Compound Is The Compound
Provided By Example 1
A 10 tote trial of a gelatinized starch composition was prepared by mixing the
comprising a glyoxal generating compound provided by Example 1 and Penford PAR
6048AR cationic potato starch (7%:93% by weight of glyoxal generating
compoundatarch) to give a final combined concentration of 21% (less than 3000
cps).
The gelatinized starch composition was added to the paper making process at
several
locations in the wet end of the paper making process, such as the suction side
of the
machine chest fan pump and the suction side of the pressure screen. During
this trial
the average dosage rate of the gelatinized starch composition was about 10
pounds per
ton.
The paper manufacturing method using the gelatinized starch composition having
a
glyoxal generating compound provided by Example 1 provides the following
benefits:
(1) reduced the basis weight of the paperboard by approximately 1.5%; (2)
increased
the speed of the machine by approximately 6%; (3) maintained the ring crush
and
Mullen test parameters of the paperboard while the speed was increased and the
basis
weight was reduced; (4) increased drainage from the consolidated web; (5)
reduced
filler machine chest turbidity; and (6) reduced white water turbidity.
EXAMPLE 8: Preparation of a Cyclic Glyoxal Compound with Pendant Glyoxal
Residues and no aldehyde blocking.
A 1000m1 flask was charged with glyoxal (40% in water, 435 grams, 3 moles)
and sulfuric acid (98%, 2 grs) and was stirred and warmed to 65°C. Urea
(50% in
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water, 120 grams, 1 mole) was added to the stirred glyoxal solution over four
hours at
65 °C. The reaction mixture was held for two hours at 70°C to
generate the product,
of which the predominant reaction product had the structure, as follows:
HO
O O
OH
Example 9 - Demonstration of Stability for glyoxal generating compounds in a
self
retaining starch solution.
Penford PAR 6048AR cationic potato starch was blended with the glyoxal
generating
compounds taken from example 1, 5, and 8. In addition, unreacted/unblocked
glyoxal
,was used as a comparison. The blending was done at ambient temperature and
for 30
minutes. The blend ratio and starch solids are listed in Table IV. A
Brookfield RV
viscometer (spindle #5 / 10 rpm / 25°C) was used to measure the
viscosity.
Table IV
10% Active Starch Solids
15% Active crosslinker
CrosslinkerGlyoxal Example Example Example #5
#1 #8
Viscosity
2 Hours Gel (O.Shr)300 cPs Gel (O.Shr)350 cPs
4 Hours Gel 300 cPs Gel 300 cPs
6 Hours Gel 300 cPs Gel 300 cPs
8 Hours Gel 300 cPs Gel 300 cPs
24 Hours Gel 300 cPs Gel 300 cPs
The results in Table IV demonstrate that the blocked aldehyde containing
compounds of type demonstrated in Examples 1 and 5 can produce stable mixtures
with starch while unblocked aldehyde containing compounds, like that of
example 8,
and glyoxal will not produce stable mixtures with starch.
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The disclosures of all articles and references mentioned in this application,
including patents, are incorporated herein by reference.
The invention and the manner and process of making and using it, are now
described in such full, clear, concise and exact terms as to enable any person
skilled in
the art to which it pertains, to make and use the same. It is to be understood
that the
foregoing describes preferred embodiments of the present invention and that
modifications may be made therein without departing from the spirit or scope
of the
present invention as set forth in the claims. To particularly point out and
distinctly
claim the subject matter regarded as invention, the following claims conclude
this
specification.
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