PAPER MAKING PROCESS AND STARCH COMPOSITIONS COMPRISING A CROSSLINKING AGENT FOR USE IN SAME

PROCEDE DE FABRICATION DU PAPIER ET COMPOSITIONS D'AMIDON COMPRENANT UN AGENT DE RETICULATION DESTINEES A ETRE UTILISEES DANS CE PROCEDE

English Abstract

The present invention relates to methods for manufacturing paper or paperboard
with improved strength and drainage by introduction into the fiber furnish,
prior to sheet formation, an aqueous starch dispersion of a gelatinized, self-
retaining starch, and an aldehyde generating compound or a glyoxal releasing
compound. The present invention further relates to pre-gelatinized starch
compositions comprising an aqueous mixture of a pre-gelatinized starch and an
aldehyde generating compound or a glyoxal releasing compound.

French Abstract

La présente invention porte sur des procédés de fabrication du papier ou de carton ayant une meilleure résistance et un meilleur drainage par introduction dans la composition fibreuse, avant la formation des feuilles, une dispersion aqueuse d'un amidon autorétentif, gélatinisé et d'un composé générant un aldéhyde ou d'un composé libérant un éthanedial. La présente invention porte également sur des compositions d'amidon prégélatinisées comprenant un mélange aqueux d'un amidon prégélatinisé et d'un composé générant un aldéhyde ou d'un composé libérant un éthanedial.

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 suitable for use in making paper or paperboard;
incorporating a gelatinized starch composition into the fiber slurry, wherein
the gelatinized starch composition comprises:
gelatinized starch; and
an aldehyde generating compound capable of forming at least two or more
covalent bonds to functional groups present in the starch or fiber when the
aldehyde
generating compound is heated above an activation temperature;
forming the paper or paperboard sheet;
heating the paper or paperboard sheet at a temperature above the activation
temperature of the aldehyde generating compound which is sufficient to dry the
paper
or paperboard sheet.
2. The method of claim 1, wherein a paper sheet is prepared by the
method of manufacture.
3. The method of claim 1, wherein a paperboard sheet is prepared by the
method of manufacture.
4. The method of claim 1, wherein the starch is self-retaining.
5. The method of claim 4, wherein the starch is a net cationic starch.
6. The method of claim 4, wherein the starch is pregelatinized self-
retaining starch selected from potato, corn or wheat starch.
7. The method of claim 1, wherein the gelatinized starch composition
comprises between 0.5% to 50% aldehyde generating compound based on the dry
weight of the starch and aldehyde generating compound.
-31-

8. The method of claim 1, wherein the aldehyde generating compound
reacts with starch or gelatinized starch with a rate sufficiently slow to
permit storage
of the composition for at least one day at room temperature.
9. The method of claim 8, wherein the aldehyde generating compound
reacts with starch or gelatinized starch at a sufficiently slow rate to permit
storage of
the composition for at least one week at room temperature.
10. The method of claim 8, wherein the aldehyde generating compound
reacts with starch or gelatinized starch at a sufficiently slow rate to permit
storage of
the composition for at least three weeks at room temperature.
11. The method of claim 1, wherein the gelatinized starch composition
further comprises at least one aldehyde blocking compound capable of blocking
aldehyde residues.
12. The method of claim 11, wherein the aldehyde blocking compound
loading is at least 10 molar % of the aldehyde generating compound.
13. The method of claim 11, wherein the aldehyde blocking compound is
selected from the group consisting of C1-20alcohols, C2-20alkylene glycols,
and C1-
alkylamines.
14. The method of claim 11, wherein the aldehyde blocking compound is
selected from the group consisting of methanol, ethanol, propanol, ethylene
glycol,
glycerin, propylene glycol and urea.
15. The method of claim 1, wherein the aldehyde generating compound is
a glyoxal releasing compound.
16. The method of claim 15, wherein the glyoxal releasing compound is a
reaction product of at least one molar equivalent of glyoxal with between
about 0.25
and about 5 molar equivalents of one or more stabilizing agents.
-32-

17. The method of claim 16, wherein the glyoxal releasing compound
thermally degrades at the temperature sufficient to dry paper or paperboard
thereby
releasing one or more equivalents of glyoxal.
18. The method of claim 17, wherein the thermally released glyoxal forms
crosslinks between two starch moieties or between a starch moiety and fiber by
reacting with functional groups of the starch moiety or fiber to form covalent
bonds.
19. The method of claim 16, wherein the glyoxal releasing compound is a
reaction product of
at least one molar equivalent of glyoxal; and
between about 0.5 and about 5 molar equivalents of stabilizing agents selected
from the group consisting of optionally substituted urea, optionally
substituted
thiourea, optionally substituted imidazolidin-2-one, and optionally
substituted
tetrahydro-pyrimidin-2-one.
20. The method of claim 11, wherein the aldehyde generating compound is
a reaction product of
at least one molar equivalent of glyoxal; and
between about 1 and about 3 molar equivalent of stabilizing agents selected
from the group consisting of urea, thiourea, 4,5-dihydroxy-imidazolidin-2-one,
and 4-
hydroxy-5-(C1-10-alkyl)-tetrahydro-pyrimidin-2-one.
21. The method of claim 19, wherein the glyoxal releasing compound is a
compound according to Formula I:
<IMG>
wherein
-33-

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,
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;
R3 is independently selected at each occurrence of R3 from the group
consisting of hydrogen, optionally substituted C1-20alkyl, and blocked glyoxal
residues, where the blocked glyoxal residue is a 1-hydroxy-2-(protected
aldehyde
residue)-ethan-1-yl group; and
wherein the aldehyde generating compound according to Formula I thermally
degrades to generate at least one equivalent of glyoxal when heated above an
activation temperature.
22. The method of claim 21, wherein the aldehyde generating compound is
a glyoxal releasing compound.
23. The method of claim 22, wherein
R1 and R2 are independently selected from the group consisting of hydrogen,
hydroxyl, 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 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.
24. The method of claim 22, wherein
X1 and X2 are NR3;
A is a single bond;
-34-

B is a carbonyl or thiocarbonyl group; and
R1 and R2 are independently selected from hydroxyl, C1-6alkoxy, or blocked
glyoxal residues.
25. The method of claim 22, 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, hydroxyl, C1-6alkoxy, or
blocked glyoxal residues; and
R3 is 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.
26. The method of claim 22, wherein the glyoxal releasing compound
comprises at least one compound selected from the group consisting of
compounds of
the formulae:
<IMG>
-35-

27. The method of claim 1, wherein the gelatinized starch composition
further comprises a cationic starch containing at least one ammonium salt.
28. A gelatinized starch composition for use strengthening paper or
paperboard, the composition comprising:
a self retaining gelatinized starch;
at least one aldehyde blocking compound capable of blocking aldehyde
residues; and
an aldehyde generating compound according to the Formula I:
<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,
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;
R3 is independently selected at each occurrence of R3 from the group
consisting of hydrogen, optionally substituted C1-20alkyl, and blocked glyoxal
residues, where the blocked glyoxal residue is a 1-hydroxy-2-(protected
aldehyde
residue)-ethan-1-yl group;
wherein the aldehyde generating compound according to Formula I thermally
degrades to generate at least one equivalent of aldehyde when heated above an
activation temperature; and
-36-

wherein the aldehyde blocking compound loading is at least 10 molar % of the
aldehyde generating compound.
29. The gelatinized starch composition of claim 28, wherein the aldehyde
generating compound is a glyoxal releasing compound.
30. The gelatinized starch composition of claim 29, wherein the glyoxal
releasing compound reacts with starch or gelatinized starch with a rate
sufficiently
slow to permit storage of the composition for at least one day at room
temperature.
31. The gelatinized starch composition of claim 29, wherein the glyoxal
releasing compound reacts with starch or gelatinized starch at a sufficiently
slow rate
to permit storage of the composition for at least one week at room
temperature.
32. The gelatinized starch composition of claim 29, wherein the glyoxal
releasing compound reacts with starch or gelatinized starch at a sufficiently
slow rate
to permit storage of the composition for at least three weeks at room
temperature.
33. The gelatinized starch composition of claim 29, wherein the glyoxal
releasing compound is capable of forming at least two or more covalent bonds
to
functional groups present in the starch or fiber when the glyoxal releasing
compound
is heated above an activation temperature.
34. The gelatinized starch composition of claim 29, wherein the starch is a
cationic starch.
35. The gelatinized starch composition of claim 29, wherein the starch is
selected from potato, corn or wheat starch.
36. The gelatinized starch composition of claim 29, wherein the aldehyde
blocking compound is selected from the group consisting of C1-20alcohols, C2-
20alkylene glycols, and C1-20alkylamines.
-37-

37. The gelatinized starch composition of claim 29, wherein the aldehyde
blocking compound is selected from the group consisting of methanol, ethanol,
propanol, ethylene glycol, and propylene glycol.
38. The gelatinized starch composition of claim 29, wherein
R1 and R2 are independently selected from the group consisting of hydrogen,
hydroxyl, 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 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.
39. The gelatinized starch composition of claim 29, wherein
X1 and X2 are NR3;
A is a single bond;
B is a carbonyl or thiocarbonyl group; and
R1 and R2 are independently selected from hydroxyl, C1-6alkoxy, or stabilized
glyoxal residues.
40. The gelatinized starch composition of claim 29, 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, hydroxyl, C1-6alkoxy, or
stabilized glyoxal residues; and
R3 is 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.
-38-

41. The gelatinized starch composition of claim 29, wherein the glyoxal
releasing compound comprises at least one compound selected from the group
consisting of is compounds of the formulae:
<IMG>
-39-

Description

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PAPER MAKING PROCESS AND STARCH COMPOSITIONS COMPRISING A
CROSSLINKING AGENT FOR USE IN SAME
BACKGROUND OF THE INVENTION
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 present invention further provides starch compositions suitable
for use
in the methods of making paper or paperboard materials with increased strength
provided by the invention., The compositions comprise at least one type of
gelatinized
starch and 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.
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
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

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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. .
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
_2_

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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.
As an alternative approach, it would be desirable to have a starch composition
including a stabilized aldehyde generating compound or a stabilized glyoxal
compound that is activated upon drying of the formed paper and paperboard
materials. It would also be desirable to provide methods of making paper and
paperboard with increased strength using such starch compositions.
SUMMARY OF THE INVENTION
The present invention provides storage stabile, pre-gelatinized starch
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 strength using less pre-
gelatinized starch composition 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.
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In accord with the present invention, a method for manufacturing paper and
paperboard materials with increased strength, the method comprising the steps
of
providing a storage stabile, gelatinized starch composition comprising
gelatinized starch and 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
when the aldehyde generating compound is heated above an activation
temperature;
providing a fiber slurry suitable for use in making paper or paperboard;
incorporating a gelatinized starch composition into the fiber slurry;
forming a paper or paperboard sheet; and
heating the paper or paperboard sheet at a temperature above the activation
temperature of the aldehyde generating compound and which is sufficient to dry
the
paper or paperboard sheet
The present invention also provides gelatinized starch compositions which are
suitable for strengthening paper prepared by the methods of the invention
where the
starch composition comprises a mixture of
a self retaining gelatinized starch;
at least one aldehyde blocking compound capable of blocking aldehyde
residues; and
an aldehyde generating compound according to the Formula I:
/B\
X~ X2
R~ A RZ
wherein
A is an optionally substituted methylene group, an optionally substituted a,~-
CZ_4-alkylene, 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;
-4-

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Rl and Rz are independently selected from the group consisting of hydrogen,
hydroxyl, optionally substituted C1_zoalkyl, 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, optionally substituted Ci_zoalkyl, a blocked
dialdehyde
compound (e.g., a stabilized dialdehyde compound) comprising at least two
protected
aldehyde residues, and a blocked glyoxal residue, where the blocked glyoxal
residue
is a 1-hydroxy-2-(protected aldehyde residue)-ethan-1-yl group;
wherein the aldehyde generating compound according to Formula I thermally
degrades to generate at least one equivalent of glyoxal or a compound
comprising two
or more aldehyde residues when heated above an activation temperature; and
wherein the aldehyde blocking compound loading is at least 10 molar % of the
aldehyde generating compound.
Preferred aldehyde generating compounds according to Formula I include
glyoxal releasing compounds such as those compounds in which (i) A is a single
bond
and Rl and Rz are hydroxyl, or (ii) R3 contains a glyoxal residue that can
generate
glyoxal; or compounds satisfying both conditions (i) and (ii).
Other aspects of the invention are discussed infiAa.
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.
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For the purposes of the present invention, the term "aldehyde generating
compound" refers to materials that upon activation by heat will 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 thermal
degradation
and compounds capable of generating one or more aldehyde groups in sequence
such
that two or more covalently connected aldehyde residues are generated during
the
thermal degradation 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 upon activation by heat will 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 releasing group is hindered from forming a free or active
aldehyde
group under the current conditions present.
For the purposes of the present invention, the term "stabilizing agent" refers
to
any compound or combination of compounds capable of forming a cyclic ring
structure which comprises one or more equivalents of glyoxal as a part of the
ring
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.
-6-

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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.
Typically preferred aldehyde blocking agents release or unmask the aldehyde
group at
elevated temperatures such as the temperature used to dry paper or paperboard.
DETAILED DESCRIPTION OF THE INVENTION
Self retaining gelatinized starch compositions of the present invention
comprise an aqueous dispersion containing at least one self retaining
gelatinized
starch and at least one aldehyde generating compound or glyoxal releasing
compound
that are suitable for imparting increased strength to paper. Preferred aqueous
self
retaining gelatinized starch compositions of the invention comprise at least
one
glyoxal releasing compound comprising at least one blocked glyoxal residue
which is
capable of generating reactive aldehyde groups and/or releasing glyoxal upon
heating
the glyoxal releasing compound. Typically preferred aqueous self retaining
gelatinized starch compositions of the invention are resistant to gelation and
viscosity
increase during storage, particularly when stored at a temperature of
40°C or less.
Moreover, preferred gelatinized starch compositions of the invention have a
sufficiently low viscosity to permit the composition to flow.
The self retaining gelatinized starch compositions of the present invention
are
particularly useful for manufacturing paper or paperboard sheet having
increased
strength at the same basis weight, or having the same strength with reduced
basis
weight. The methods for manufacturing paper or paperboard typically comprise
providing a fiber slurry suitable for use in making paper; incorporating a
gelatinized
starch composition into the fiber slurry; forming the paper and paperboard
materials;
heating the paper and paperboard materials at a temperature above the
activation
temperature of the aldehyde generating compound or glyoxal releasing compound
and
which is sufficient to dry the paper.

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Starch sources useful in the practice of the present invention include, for
example, potato, corn, waxy corn, red milo, white milo, wheat, tapioca, and
the like.
Preferred starch sources include potato, corn and wheat. Preferably, the
starch
composition comprises a self retaining starch, i.e. a starch having a net
cationic
charge. In particular starches containing cationic or a combination of
cationic and
anionic functional groups;, the so-called amphoteric starches, including all
the known
commercial cationic and amphoteric starches, can be used. More preferably, the
starch composition, which comprises a commercial pregelatinized cationic
starch such
as, but not limited to, those sold by Penford, Grain Processing Corporation
(GPC),
National Starch, Raisio and Staley, are suitable for use in the compositions
and paper
making methods provided by the invention.
In addition to the pre-gelatinized starches, any of the mill cooked starches
commonly used in the wet-end of the paper machine can be used if cooled prior
to
addition of the glyoxal releasing compound.
Gelatinized starch composition suitable for use in the paper making methods
of the invention generally comprise between about 0.5% to about 50% of at
least one
aldehyde generating compound or glyoxal releasing compound based on the
combined dry weight of the starch and aldehyde generating compound or glyoxal
releasing compound. Preferred gelatinized starch compositions comprise between
about 0.5 % and about 10, or 15, or 20, or 25, or 30% by dry weight of at
least one
aldehyde generating compound or glyoxal releasing compound.
The gelatinized starch compositions of this invention can be used alone or in
combination with other separately added strength developing additives commonly
used in papermaking. These include cationic guar gum, cationic hemicelluloses,
chitosan, anionic polyacrylamide strength resins as described in U.S. Patent
5,543,446, cationic reactive polyacrylamide strength resins as described in
U.S. Patent
3,556,932, and the various types of commercial wet strength resins including
the
common and well known aminopolyamide- epichlorohydrin and melamine- or urea-
formaldehyde resins. They also can be used in combination with the separately
added
_g_

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starch added to the wet end or as a surface treatment, as is commonly
practiced in the
papermaking process to develop strength or improve other aspects of
papermaking.
In particularly preferred methods of the invention, the aldehyde generating
compound thermally degrades at the temperature sufficient to dry paper thereby
releasing or generating enough aldehyde groups to crosslink the starch and/or
fiber.
Preferred aldehyde generating compounds generate one or more equivalents of
glyoxal and/or glyoxal equivalents during the thermal degradation. More
preferably,
at least a portion of the released glyoxal from the thermal degradation of the
aldehyde
generating compound reacts with functional groups present in the starch or on
the
fiber surface to form covalent crosslinks between two starch molecules or
particles or
between starch and fiber.
In preferred methods of making paper provided by the invention, the aldehyde
generating compound is a glyoxal releasing compound which comprises a reaction
product of at least one molar equivalent of glyoxal with between about 0.25
and about
5 molar equivalents of one or more stabilizing agents. More preferably, the
glyoxal
releasing compound comprises the reaction product of between one and three
equivalents of glyoxal and between one and two, three or four equivalents of
one or
more stabilizing agents.
Typically preferred stabilizing agents suitable for use in the glyoxal
releasing
compounds or aldehyde generating compounds of the invention include those
chemical compounds capable of reacting with at least one and preferably at
least two
aldehyde groups to form one or two thermally labile functional groups which
release
an unblocked aldehyde functional group when heated above an activation
temperature. In preferred embodiments, the activation temperature is between
about
75°C and about 250°C, more preferably the activation temperature
is between about
90°C and about 150 °C.
In preferred methods of making paper, the gelatinized starch composition may
comprise a glyoxal releasing compound prepared by the reaction of
at least one molar equivalent of glyoxal; and
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between about 0.5 and about 3 molar equivalents of stabilizing agents selected
from the group consisting of optionally substituted urea, optionally
substituted
thiourea, optionally substituted imidazolidin-2-one, and optionally
substituted
tetrahydro-pyrimidin-2-one.
In certain preferred methods of making paper provided by the present
invention, the gelatinized starch composition further comprises one or more
aldehyde
blocking compounds which are capable of reversibly blocking residual aldehyde
residues present in the gelatinized starch composition, e.g., unblocked
aldehyde
groups in the aldehyde generating compound, the glyoxal releasing compound or
aldehyde groups present in glyoxal containing byproducts which may be
generated
during the synthesis of the glyoxal releasing compound. In preferred
embodiments,
aldehyde blocking compounds can be selected from amines, particularly alkyl
amines,
alcohols such as alkanols, alkylene glycals and other aldehyde blocking
compounds,
which liberate a free aldehyde upon exposure to elevated temperatures. Certain
preferred aldehyde blocking compounds include, for example, methanol, ethanol,
1-
and 2-propanol, propylene glycol, and the like.
In preferred papermaking methods of the invention, the gelatinized starch
composition may further comprise one or more optionally substituted
Cl_2oalcohol,
optionally substituted CZ_ZOalkylene glycol or a combinations thereof may be
also
incorporated, as an aldehyde blocking compound to block residual aldehydes
present
in the aldehyde generating compound, the glyoxal releasing compound or
aldehyde
groups present in byproducts produced during the preparation of the glyoxal
releasing
compound.
More preferably, paper making methods of the invention comprise the use of a
glyoxal releasing compound which is the reaction product of
between 0.5 and 2 molar equivalent of glyoxal; and
between about 1 and about 3 molar equivalent of stabilizing agents selected
from the group consisting of urea, thiourea, 4,5-dihydroxy-imidazolidin-2-one,
and 4-
hydroxy-5-(C~_~o-alkyl)-tetrahydro-pyrimidin-2-one.
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Particularly preferred gelatinized starch compositions which are suitable for
use in the paper making processes of the invention include compositions in
which the
glyoxal releasing compound is the reaction product of glyoxal and at least one
stabilizing agent selected from urea, thiourea, 4,5-dihydroxy-imidazolidin-2-
one, and
4-hydroxy-5-(C~_~o-alkyl)-tetrahydro-pyrimidin-2-one and further comprise at
least 10
molar percent of an aldehyde blocking compound selected from propylene glycol,
methanol, ethanol, n-propanol, and isopropanol.
In other preferred methods of making paper, the aldehyde generating
compound is a compound according to Formula I:
X~ X2
R~ A R2
wherein
A is an optionally substituted methylene group, an optionally substituted a,c~-
Cz_4alkylene, or a single bond;
B is carbonyl, thiocarbonyl, or an optionally substituted 1,2-ethylene
residue;
X~ and Xz are independently selected from the group consisting of oxygen and
NR3;
R~ and Rz are independently selected from the group consisting of hydrogen,
hydroxyl, optionally substituted CI_zoalkyl, optionally substituted
CI_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 C1_zoalkyl, and blocked glyoxal
residues, where the blocked glyoxal residue is a 1-hydroxy-2-(protected
aldehyde
residue)-ethan-1-yl group;
wherein the aldehyde generating compound according to Formula I thermally
degrades to generate at least one equivalent of a poly(aldehyde) compound when
heated above an activation temperature; and
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wherein the aldehyde blocking compound loading is at least 10 molar % ofthe
aldehyde generating compound.
Preferred aldehyde generating compounds of Formula (I) are glyoxal releasing
compounds. More preferred glyoxal releasing compounds according to Formula I
include those compounds wherein (i) A is a single bond and Rl and RZ are
hydroxyl,
or (ii) R3 contains a glyoxal residue that can generate glyoxal, or compounds
satisfying both conditions (i) and (ii).
Preferred glyoxal releasing compounds according to Formula I which are
suitable for use in the paper making methods of the invention include those
compounds in which:
Rl and R2 are independently selected from the group consisting of hydrogen,
hydroxyl, 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 a blocked glyoxal residue selected from the group consisting of 1,2-
dihydroxy-2-(C1~-alkoxy)-ethan-1-yl, 1,2-dihydroxy-2-(3-hydroxypropoxy)-ethan-
1-
y1, and 1,2-dihydroxy-2-(2-hydroxypropoxy)-ethan-1-yl.
Other preferred glyoxal releasing compounds according to Formula I which
are suitable for use in the paper making methods of the invention include
those
compounds in which:
XI and X2 are NR3;
A is a single bond;
B is a carbonyl or thiocarbonyl group; and
Rl and RZ are independently selected from hydroxyl, C~_6alkoxy, or blocked
glyoxal residues.
Still other preferred glyoxal releasing compounds according to Formula I
which are suitable for use in the paper making methods of the invention
include those
compounds in which:
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Xl and X2 are NR3;
A is a l,l-CI_6alkylene group;
B is a carbonyl or thiocarbonyl group;
Rl and RZ are independently selected from hydrogen, hydroxyl, C~_6alkoxy, or
blocked glyoxal residues; and
R3 is a blocked glyoxal residue selected from the group consisting of 1,2-
dihydroxy-2-(Cl~-alkoxy)-ethan-1-yl, 1,2-dihydroxy-2-(3-hydroxypropoxy)-ethan-
1-
yl, and 1,2-dihydroxy-2-(2-hydroxypropoxy)-ethan-1-yl.
Particularly preferred aldehyde generating compound or glyoxal releasing
compounds suitable for use in the paper making processes of the invention
include,
but are not limited to, the following compounds:
O
HN NH
HO OH
OH HO O OH OH
O ~ O
N N
OH ~ OH
HO OH ; and
OH HO O OH OH
O ~ O
N N
OH OH
HO
Each of which may optionally be mixed with one or more aldehyde blocking
compounds such as from propylene glycol, methanol, ethanol, n-propanol, and
isopropanol. More preferably the glyoxal releasing compounds are admixed with
at
least 10, 15, 20, 25, or more molar percent of an aldehyde blocking compound.
While
not wishing to be bound by theory, addition of the aldehyde blocking compound
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generally prevents the aldehyde generating compound or glyoxal releasing
compound
from comprising unblocked aldehyde residues and thereby increases the
stability of
gelatinized starch compositions comprising one or more aldehyde generating
compound or glyoxal releasing compound provided by the invention.
Other preferred methods of the invention include those in which the starch
component of the starch composition further comprises a cationic starch which
is
functionalized with at least one ammonium salt. More preferably, the ammonium
salts incorporated into the starch composition comprises an alkylated ammonium
cation and a small counter anion. Particularly preferred ammonium salts
include
tetraalkylammonium halide salts, N-alkyl pyridinium halide salts, or salts
generated
from the use of Dow QuatTM 180, a common canonizing agent for preparing
cationic
starch.
15:
Preferred starch compositions of the invention comprise a self retaining
starch,
i.e. a starch having a net cationic charge. In particular, commercial
pregelatinized
cationic starch such as, but not limited to, those sold by Penford, Grain
Processin
Corporation (GPC), National Starch, Raisio and Staley are suitable for use in
the
gelatinized starch compositions provided by the invention. Starch sources such
as
potato, corn, waxy corn, red milo, white milo, wheat, tapioca, and the like
may be
used. Preferred starch sources include potato, corn and wheat.
In addition to the pre-gelatinized starches any of the mill cooked starches
commonly used in the wet-end of the paper machine may be used if cooled prior
to
addition of the aldehyde generating compound or glyoxal releasing compound.
Gelatinized starch compositions of the invention typically comprise between
about 0.5% to about 50% of at least one aldehyde generating compound or
glyoxal
releasing compound based on the combined dry weight of the starch and aldehyde
generating compound or glyoxal releasing compound.
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The gelatinized starch compositions of the invention comprise the use of an
aldehyde generating compound or a glyoxal releasing compound which is stable
in the
presence of starch at about room temperature. That is, gelatinized starch
compositions of the invention comprise an aldehyde generating compound or a
glyoxal releasing compound which does not substantially react with starch at
room
temperature, that is the reaction with starch is sufFciently sluggish as to
preclude the
accumulation of significant amounts of the reaction product during routine
storage
time periods.
In particularly preferred gelatinized starch compositions of the invention,
the
aldehyde generating compound or glyoxal releasing compound thermally degrades
at
the temperature sufficient to dry paper or paperboard thereby releasing one or
more
equivalents of glyoxal or reactive aldehyde groups. More preferably, at least
a
portion of the aldehyde groups released from the thermal degradation of the
aldehyde
generating compound or glyoxal releasing compound reacts with functional
groups of
the starch or fiber to form covalent crosslinks between two starch moieties or
between
a starch moiety and a fiber.
In preferred gelatinized starch compositions of the invention, composition
comprises:
a self retaining gelatinized starch;
at least one aldehyde blocking compound capable of blocking aldehyde
residues of glyoxal; and
an aldehyde generating compound according to the Formula I:
B
x ~ ~x2
R~ A R2
wherein
A is an optionally substituted methylene group, an optionally substituted C2_
4alkylene group, or a single bond;
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B is carbonyl, thiocarbonyl, or an optionally substituted 1,2-ethylene
residue;
Xl andaX2 are independently selected from the group consisting of oxygen and
NRs;
R~ and RZ are independently selected from the group consisting of hydrogen,
hydroxyl, optionally substituted C1_2oalkyl, optionally substituted
C1_ZOalkoxy,
optionally substituted urea, optionally substituted thiourea, or
Rl and R~, 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~_2oalkyl, and blocked glyoxal
residues, where the blocked glyoxal residue is a 1-hydroxy-2-(protected
aldehyde
residue)-ethan-1-yl group;
wherein the aldehyde generating compound according to Formula I thermally
degrades to generate at least one equivalent of glyoxal when heated above an
activation temperature; and
wherein the aldehyde blocking compound loading is at least 10 molar % of the
glyoxal releasing compound.
Preferred aldehyde generating compounds of Formula (I) are glyoxal releasing
compounds. More preferred glyoxal releasing compounds according to Formula I
include those compounds wherein (i) A is a single bond and Rl and R2 are
hydroxyl,
or (ii) R3 contains a glyoxal residue that can generate glyoxal, or compounds
satisfying both conditions (i) and (ii).
Particularly preferred gelatinized starch compositions of the invention
include
those compositions which are a homogeneous solution or a dispersion in an
aqueous
media.
Other preferred gelatinized starch composition comprise an aldehyde
generating compound or a glyoxal releasing compound according to Formula I
wherein the aldehyde generating compound or glyoxal releasing compound reacts
with starch or gelatinized starch with a rate sufficiently slow to permit
storage of the
composition for at least one day at room temperature. More preferably, the
gelatinized starch composition is stable for at least three days or for at
least seven
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days. Particularly preferred gelatinized starch compositions are stable for
two weeks
or more or for a month or more.
Other preferred gelatinized starch composition of the invention include those
compositions in which the aldehyde blocking compound is selected from the
group
consisting of C1_ZOalcohols, CZ_2oalkylene glycols, and C1_2oalkylamines. More
preferably the aldehyde blocking compound is selected from the group
consisting of
methanol, ethanol, propanol (n-propanol, isopropanol, or a mixture thereof),
ethylene
glycol, and propylene glycol.
Yet other preferred gelatinized starch composition of the invention include
glyoxal releasing compounds according to Formula I wherein
R~ and R2 are independently selected from the group consisting of hydrogen,
hydroxyl, methanol, ethanol, urea, 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, methyl, and ethyl, or
R3 is a blocked glyoxal residue selected from the group consisting of 1,2-
dihydroxy-2-(C1.~-alkoxy)-ethan-1-yl, 1,2-dihydroxy-2-(3-hydroxypropoxy)-ethan-
1-
y1, and 1,2-dihydroxy-2-(2-hydroxypropoxy)-ethan-1-yl.
Additional preferred gelatinized starch composition of the invention include
glyoxal releasing compounds according to Formula I wherein
XI and X2 are NR3;
A is a single bond;
B is a carbonyl or thiocarbonyl group; and
Rl and R2 are independently selected from hydroxyl, CI_6alkoxy, or blocked
glyoxal residues.
Still other preferred gelatinized starch composition of the invention include
glyoxal releasing compounds according to Formula I wherein
X~ and XZ are NR3;
A is a 1,1-C~_6alkylene group;
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B is a carbonyl or thiocarbonyl group;
R~ and R2 are independently selected from hydrogen, hydroxyl, C~_6alkoxy, or
blocked glyoxal residues; and
R3 is a stabilized glyoxal residue selected from the group consisting of 1,2-
dihydroxy-2-(CIA-alkoxy)-ethan-1-yl, 1,2-dihydroxy-2-(3-hydroxypropoxy)-ethan-
1-
y1, and 1,2-dihydroxy-2-(2-hydroxypropoxy)-ethan-1-yl.
Particularly preferred gelatinized starch composition of the invention include
aldehyde generating compounds or glyoxal releasing compounds according to
Formula I, wherein the aldehyde generating compound or glyoxal releasing
compound comprises at least one compound selected from the group consisting of
compounds of the formulae:
O
HN NH
HO OH-
OH OH
O
O ~ \H
H ; and
n
An aqueous self retaining gelatinized starch composition comprises a starch
which is self retaining due to a net cationic charge. The net charge of the
starch also
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assists the gelatinized starch in absorbing and retaining the aldehyde
generating
compounds or glyoxal releasing compound from the aqueous media of the
composition. The net charge of the starch may also increase the strength of
the
interaction between the starch and aldehyde generating compounds or glyoxal
releasing compound and the surface of the slightly anionic fiber of the pulp
slurry.
Although not wishing to be bound by theory, the gelatinized starch
composition, e.g., the essentially unreacted mixture of gelatinized starch and
an
aldehyde generating compounds, are incorporated into the pulp slurry of the
wet end
of the paper manufacturing process in an essentially unreacted form. After
consolidation of the paper or paperboard web, exposure of the web, which
comprises
the gelatinized starch composition, to temperatures sufficient to dry the
sheet under
commercial paper drying conditions, which also induces degradation of the
aldehyde
generating compound, thereby releasing reactive aldehyde groups or glyoxal
compounds having reactive aldehyde residues or a combination thereof. After
release
from the aldehyde generating compound, the reactive aldehyde groups or glyoxal
compounds having reactive aldehyde residues react with functional groups,
particularly hydroxyl and amine groups, from one or more starch molecules or
moieties or the fiber surface to generate covalent bonds.
Gelatinized starch compositions provided by the invention may be prepared by
any suitable method of forming an admixture of the aqueous starch solution and
the
aldehyde generating compound. Typically the aldehyde generating compound is
added to the aqueous starch solution and the combined material is intimately
mixed to
form a substantially homogeneous composition. Although the mixing process may
be
carried out at room temperature, it is often desirable to gently heat the
mixture while
mixing to reduce the viscosity of the aqueous starch solution. In general,
warming the
mixture to between about 25°C and about 40°C is sufficient to
reduce the viscosity
without degradation of the aldehyde generating compound or initiating a
reaction
between the starch and the aldehyde generating compound. The blending or
mixing
of the starch and aldehyde generating compound is typically complete in less
than 24
hours and is preferably complete in less than about 12, 8, or 6 hours. In
particularly
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preferred methods of making the gelatinizes starch compositions of the
invention the
mixing or blending step is complete in between about 1 and about 3 hours.
The shelf life of the gelatinized starch composition is typically dependent
upon, among other things, the concentration of the starch, the concentration
of the
aldehyde generating compound, the rate at which the starch will degrade back
to its
crystalline form and the rate at which the aldehyde generating compound reacts
with
the starch at ambient or storage temperature.
The shelf life measurements as used herein refer to the ability of the
gelatinized starch composition to be transferred between storage and reactor
vessels
by traditional pumping means used in the papermaking industry. The gelatinized
starch compositions of the invention comprising of at least one aldehyde
generating
compound or glyoxal releasing compound, has generally reached its' shelf life
limit
when the gelatinized starch composition can not be pumped from the storage
vessel.
A typical starch composition can be defined to be transferable if its
viscosity is less
than 15000 cps.
Stability of the gelatinized starch compositions of the invention are
typically
measured based upon the viscosity measurement of the composition. In general,
any
gelatinized starch composition of the invention which has a viscosity of
10,000 cPs or
less after about one (1), two (2), or three (3) weeks, or more preferably
after one
month, is considered to have sufficient stability. Viscosity of the
gelatinized starch
compositions are routinely, measured suing a Brookfield viscometer having a #4
spindle rotating at 10 or 20 rpm.
In preferred methods of making paper provided by the present invention the
aldehyde generating compound or the glyoxal releasing compound is generally a
polar, non-ionic compound and, consequently, has minimal affinity for direct
interacting with fiber present in the pulp slurry which is weakly anionic.
Applicants
have surprisingly discovered that the preferred aldehyde generating compound
or
glyoxal releasing compounds interact with cationic starch molecules and are
localized
to the fiber of the paper slurry when the cationic starch adheres to the fiber
surface.
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Although not wishing to be bound by theory, the interaction between the
cationic
starch and the aldehyde generating compound or glyoxal releasing compound is
likely
due, in part, to dipole or electrostatic interactions between the starch and
the aldehyde
generating compound or glyoxal releasing compound.
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, h-propyl, i-
propyl, n-
butyl, s-butyl, t-butyl, n-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 C1_4 alkyl as used herein includes alkyl groups consisting of
1 to 4
carbon atoms, which may contain a cyclopropyl moiety. Suitable examples are
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.
"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.
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"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, n-
hexoxy, 2-hexoxy, 3-hexoxy, and 3-methylpentoxy. Alkoxy groups typically have
1
to about 8 carbon atoms, more typically 1 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.
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.
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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 dried 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 4,5-dihydroxy-imidazolidin-2-one and at
least one aldehyde blocking compound
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 SS°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
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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.
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
releasing
compound provided in Example 1. The mixture was prepared by mixing the glyoxal
releasing 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 releasing compound from Example 1 into a Penford PAR 6048AR at
90°C
over 30 minutes with agitation (pre-reaction process). Iri both 3C and 3D the
glyoxal
releasing 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 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 releasing 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 3G). Moreover, treatment of the gelatinized
starch
composition under the conditions of the pre-reaction process reduces the
stability of
the starch composition.
EXAMPLE 4: Dry Strength Evaluation of Paper Manufactured with a Gelatinized
Starch Composition Comprising the Compound of Example 2 as the Glyoxal
releasing 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 releasing compound provided in Example 2. The
mixture was prepared by mixing the glyoxal releasing 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.
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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 releasing 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
releasing 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 releasing compound of Example 2 was added to the gelatinized
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
amount of reaction by-products were then removed from the reaction flask by
vacuum
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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
releasing compound formed by the reaction is represented by the structure, as
follows:
OH
~O CH3
CH / v3
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
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PAR 6048AR and the glyoxal releasing compound provided in Example 5. The
mixture was prepared by mixing the glyoxal releasing compound into the Penford
PAR 6048AR (25%) at 32°C over 1 hour with agitation. The resulting
mixture had
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 releasing 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
releasing 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 III
Sample Description Dry TensileShelf 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 pr~°'~~~+;~~ n~paper Manufactured using
V~i~h-A
Gelatinized Starch Composition In Which The Glyoxal releasing 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 releasing compound provided by Example 1 and Penford PAR
6048AR cationic potato starch (7%:93% by weight of glyoxal releasing
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.
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The paper manufacturing method using the gelatinized starch composition having
a
glyoxal releasing 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 grams) and was stirred and warmed to 65°C.
Urea (50% in
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:
OF
O~ O
HO OH
Example 9 - Demonstration of Stability for glyoxal releasing compounds in a
self
retaining starch solution.
Penford PAR 6048AR cationic potato starch was blended with the glyoxal
releasing
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
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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.
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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