U.S. patent application number 12/169268 was filed with the patent office on 2008-10-30 for composition for increasing cellulosic product strength and method of increasing cellulosic product strength.
Invention is credited to ERIC J. BECKMAN, WILLIAM EAMON CARROL, CHRISTIAN JEHN RENDU.
Application Number | 20080264590 12/169268 |
Document ID | / |
Family ID | 31996777 |
Filed Date | 2008-10-30 |
United States Patent
Application |
20080264590 |
Kind Code |
A1 |
CARROL; WILLIAM EAMON ; et
al. |
October 30, 2008 |
COMPOSITION FOR INCREASING CELLULOSIC PRODUCT STRENGTH AND METHOD
OF INCREASING CELLULOSIC PRODUCT STRENGTH
Abstract
A composition includes water; at least one hydrophilic polymer
containing at least two groups which are independently the same or
different a primary amine group or a secondary amine group and at
least one saccharide containing a reducible function as described
above. The hydrophilic polymer and the saccharide are mixed to form
a reaction mixture and reacted to increase the viscosity of the
reaction mixture. The reaction is then substantially terminated by
reducing the pH of the composition.
Inventors: |
CARROL; WILLIAM EAMON;
(OREFIELD, PA) ; RENDU; CHRISTIAN JEHN;
(ANDREZIEUX CEDEX, FR) ; BECKMAN; ERIC J.;
(ASPINWALL, PA) |
Correspondence
Address: |
BARTONY & HARE, LLP
1806 FRICK BUILDING, 437 GRANT STREET
PITTSBURGH
PA
15219-6101
US
|
Family ID: |
31996777 |
Appl. No.: |
12/169268 |
Filed: |
July 8, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10799793 |
Mar 12, 2004 |
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12169268 |
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10252262 |
Sep 23, 2002 |
7090745 |
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10799793 |
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60410375 |
Sep 13, 2002 |
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Current U.S.
Class: |
162/164.5 ;
162/164.6 |
Current CPC
Class: |
C08L 39/02 20130101;
C09D 139/02 20130101; D21H 17/56 20130101; C08L 39/00 20130101;
C09D 133/14 20130101; D21H 21/18 20130101; D21H 17/36 20130101;
D21H 17/06 20130101 |
Class at
Publication: |
162/164.5 ;
162/164.6 |
International
Class: |
D21H 21/20 20060101
D21H021/20 |
Claims
1. A composition comprising: water; at least one hydrophilic
polymer containing at least two groups which are independently the
same or different a primary amine group or a secondary amine group
and at least one saccharide containing a reducible function, the
hydrophilic polymer and the saccharide being mixed to form a
reaction mixture and reacted until to increase the viscosity of the
reaction mixture, the reaction then being substantially terminated
by reducing the pH of the composition.
2. The composition of claim 1 wherein the predetermined viscosity
of the composition is at least 20 cp at 80.degree. C. when the
reaction is substantially terminated.
3. The composition of claim 1 wherein the predetermined viscosity
of the composition is in the range of approximately 20 cp to 100 cp
at 80.degree. C. when the reaction is substantially terminated.
4. The composition of claim 1 wherein the predetermined viscosity
of the composition is in the range of approximately 20 cp to 60 cp
at 80.degree. C. when the reaction is substantially terminated.
5. The composition of claim 1 wherein the predetermined viscosity
of the composition is in the range of approximately 20 cp to 40 cp
at 80.degree. C. when the reaction is substantially terminated.
6. The composition of claim 2 wherein the predetermined viscosity
of the composition at reduced pH is no greater than 80 cp at
23.degree. C.
7. The composition of claim 1 wherein the pH of the composition is
greater than 7 during reaction and reduced to less than 7 to
substantially terminate the reaction.
8. The composition of claim 1 wherein the pH of the composition is
greater in the range of approximately 10 to 12 during reaction and
reduced to 6 or less to substantially terminate the reaction.
9. The composition of claim 8 wherein the pH of the composition is
reduced to a pH in the range of approximately 4 to 6 to
substantially terminate the reaction.
10. The composition of claim 8 wherein the pH of the composition is
reduced to a pH in the range of approximately 5 to 6 to
substantially terminate the reaction.
11. The composition of claim 1 wherein the reducing saccharide is a
monosaccharide, a disaccharide or a polysaccharide.
12. The composition of claim 1 wherein the polymer is partially
hydrolyzed poly(N-vinylformamide), partially hydrolyzed vinyl
acetate/N-vinylformamide copolymer, hydrolyzed
acrylonitrile/N-vinylformamide copolymer, amine functional
polyacrylamide, acrylic acid/vinylamine copolymer, maleic
anhydride/maleic acid copolymers with N-vinylformamide/vinylamine,
N-vinylformamide/vinylamine polymers with vinyl sulfonate comonomer
units, NVF/vinylamine copolymers with at least one cationic
monomer, allylamine polymer, diallylamine polymer,
allylamine/diallylamine copolymer, urea/formaldehyde condensation
polymers, melamine/formaldehyde condensation polymers, amidoamine
polymers, amine/epichlorohydrin polymers, poly(ethyleneimine),
hydrolyzed poly(2-alkyl-2-oxazoline) or partially hydrolyzed
poly(2-alkyl-2-oxazoline).
13. The composition of claim 1 wherein the polymer is a copolymer
of vinyl amine and vinyl alcohol.
14. The composition of claim 1 wherein the saccharide is at least
one of glucose, lactose, or 2-deoxy-D-ribose
15. The composition of claim 1 wherein the water, the hydrophilic
polymer and the reducing saccharide are contacted at approximately
a temperature of approximately 25.degree. C. or below and
subsequently heated to induce a crosslinking reaction of the
hydrophilic polymer and the reducing saccharide.
16. The composition of claim 15 wherein the pH of the composition
is at least 10 during the reaction.
17. The composition of claim 12 wherein the polymer is an
NVF/vinylamine copolymer with diallyldimethylammonium chloride or
with a cationic acrylate comonomer.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/799,793, filed Mar. 12, 2004, which is a continuation
in part application of U.S. patent application Ser. No. 10/252,262,
filed Sep. 23, 2002, now U.S. Pat. No. 7,090,745, which claims the
benefit of U.S. Provisional Patent Application Ser. No. 60/410,375,
filed Sep. 13, 2002, the disclosures of which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates generally to crosslinking
compositions suitable, for example, to increase the strength (that
is, wet and/or dry strength) of cellulosic products (including, for
example, paper and other products made from cellulosic pulp) and to
methods of increasing the strength of cellulosic products using
such compositions.
[0003] For many years, the paper-making industry has sought ways of
increasing the strength of paper. In that regard, papers fabricated
without some additional means of reinforcement thereof can fall
apart upon wetting or when subjected to mechanical stress in the
dry state. Typically, a material is added to the wet pulp to
improve the strength thereof during the formation of sheets prior
to ultimate drying. Maintaining paper strength upon wetting is
desirable in many applications, including bathroom tissue, paper
towels, napkins, and the like. Moreover, additives which increase
the strength of a wet paper often increase the dry strength of that
paper. Increased dry strength is desirable, for example, in various
packaging applications.
[0004] A number of wet- and dry-strength increasing additives are
known in the art. However, such compositions typically include one
or more components which are environmentally unfriendly or even
toxic.
[0005] For example, some wet-strength additives are condensation
products of urea and formaldehyde. Polyamine can be added to make
such resins cationic. Other wet-strength additives include
organochlorine crosslinked amidoamine compounds. A discussion of
wet-strength additives and their mechanisms is presented in "The 65
Mechanism of Wet-Strength Development in Paper: A Review," by
Herbert H. ESPY, Tappi Journal, Vol. 78, No. 4, pages 90-97 (April
1995 as well as in "Chemistry of Paper Wet-Strength. I. A Survey of
Mechanisms of WetStrength Development," by Lars WESTFELT, Cellulose
Chemistry and Technology, Vol. 13, pages 813-825 (1979), the
contents of which are incorporated by reference as though set forth
in full herein.
[0006] Chemical compositions purported to increase paper wet
strength while being chemically benign or environmentally friendly
are set forth in U.S. Pat. No. 6,146,497, which describes a
composition including (a) a water-soluble polymeric material
comprising at least one nucleophilic polymer, (b) a phenolic
compound (phenols or polyphenols) and (c) a component (an oxidizing
agent) capable of converting the phenolic compound into a quinone
compound. Sugars in conjunction with their corresponding oxidases
are contemplated as potential oxidizing agents for the phenolic
component of the composition of U.S. Pat. No. 6,146,497. Many
phenolic compound, however, are environmentally undesirable.
Moreover, many oxidizing agents are also environmentally
undesirable (for example, potassium dichromate and potassium
permanganate).
[0007] It thus remains desirable to develop improved,
environmentally friendly compositions for increasing paper wet
and/or dry strength.
SUMMARY OF THE INVENTION
[0008] In one aspect, the present invention provides a composition
comprising at least one hydrophilic polymer containing primary
(--NH.sub.2) and/or secondary (--NHR) amine groups (that is,
hydrophilic polymer contains or includes at least two groups which
are independently the same or different a primary amine group or a
secondary amine group) and at least one saccharide containing a
reducible function. In general, the R substituent upon the
secondary amine is not limited. Strong electron withdrawing groups
are not preferred as such groups can reduce the nucleophilic nature
of the secondary amine. In many cases, R is an alkyl group. The
amine groups can be pendant groups on the polymer or incorporated
into the polymer backbone. In general, the hydrophilic polymer must
include at least two amine groups (per a polymer chain) to enable
crosslinking.
[0009] Such an amine functional polymer/reducible saccharide
combination has been found to undergo an unexpected cross-linking
reaction upon the application of heat. The compositions of the
present invention can, for example, be used as cross-linking agents
in paper strengthening applications. As used herein, the term
"polymer" refers to a compound having multiple repeat units (or
monomer units) and includes the term "oligomer," which is a polymer
that has only a few repeat units. The term polymer also includes
copolymers which is a polymer including two or more dissimilar
repeat units (including terpolymers--comprising three dissimilar
repeat units--etc.). The polymers used in the compositions of the
present invention can be homopolymers and/or copolymers.
[0010] Hydrogels have found use in the paper industry, for example,
as absorbent materials. In that regard, hydrogels have been used as
absorbent materials in diapers for a number of years. Surprisingly,
the present inventors have discovered that the compositions of the
present invention, which form hydrogels, can also be used to
increase both the wet strength and dry strength of paper and other
cellulosic products. While the hydrophilic polymers of the present
invention form hydrogels with reducing sugars in aqueous solution,
cross-linking can be controlled (for example, by control of
temperature as described below) allowing application of the
hydrophilic polymer and the saccharide to wet pulp (that is, paper
or cellulosic fibers) and binding to the pulp prior to substantial
cross-linking. Typically, a pre-formed hydrogel would not be able
to effectively bind to cellulosic fibers as a result of its high
viscosity.
[0011] Polymers suitable for use in the present invention include,
but are not limited to, partially hydrolyzed poly(N-vinylformamide)
(that is, a copolymer of NVF and vinylamine), partially hydrolyzed
vinyl acetate/NVF copolymer (that is, a polymer with vinyl acetate,
vinyl alcohol, NVF and vinylamine repeat units); hydrolyzed
acrylonitrile/NVF copolymer; (available as a commercial product
from Mitsubishi and containing acrylonitrile, acrylamide, amidine,
NVF and vinylamine units), amine functional polyacrylamide (for
example, prepared via Hoffman degradation of polyacrylamide),
acrylic acid/vinylamine copolymer, maleic anhydride/maleic acid
copolymers with NVF/vinylamine, NVF/vinylamine polymers with vinyl
sulfonate comonomer units, NVF/vinylamine copolymers with cationic
monomers such as diallyldimethylammonium chloride and/or cationic
acrylate comonomers, allylamine/diallylamine polymers and
copolymers, urea/formaldehyde and melamine/formaldehyde
condensation polymers, amidoamine polymers (prepared from
dicarboxylic acids and polyfunctional amines),
amine/epichlorohydrin polymers, poly(ethyleneimine), and hydrolyzed
or partially hydrolyzed poly(2-alkyl-2-oxazoline). One hydrophilic
polymer or a mixture of two or more such polymers can be used in
compositions of the present invention.
[0012] In general, polymers having a broad range of number average
molecular weight (Mw) are suitable for use in the present
invention. Preferably, the molecular weight of the polymers is at
least approximately 500. More preferably, the molecular weight is
in the range of approximately 30,000 to approximately 100,000.
Polymers having molecular weight in excess of 100,000 can be used,
but water solubility can decrease for such polymers as molecular
weight increases beyond approximately 100,000.
[0013] The reducible saccharides used in the present invention can
be monosaccharides, disaccharides, trisaccharides etc, (for
example, sugars) or polysaccharides (for example, starch or
cellulose). Polysaccharides are typically a combination of nine or
more monosaccharides. Reducible saccharides or reducing saccharides
include a reducing group, function or functionality which is
typically an aldehyde group (--C(O)H) or a hemiacetal group
##STR00001##
which is another form of an aldehyde when the saccharide is in a
cyclic conformation. Examples of reducing saccharides suitable for
use in the present invention include, but are not limited to, the
sugars glucose, lactose, and 2-deoxy-D-ribose. To decrease costs,
the saccharide is preferably a monosaccharide (for example,
glucose), a disaccharide (for example, lactose) or a polysaccharide
(for example, starch).
[0014] The composition can, for example, further include a base.
Examples of suitable bases include, but are not limited to, sodium
hydroxide, potassium hydroxide, ammonia or calcium carbonate.
[0015] In one embodiment, the polymer is a copolymer of vinyl amine
and vinyl alcohol. Preferably, the copolymer is at least 0.5% by
weight of vinyl amine. More preferably, the copolymer is at least
3% by weight of vinyl amine. Even more preferably, the copolymer is
at least 6% by weight of vinyl amine. Copolymers having well in
excess of 6% by weight of vinyl amine are suitable for use in the
present invention. In several embodiments for example, copolymer
can be at least 12% by weight of vinyl amine.
[0016] A broad range of mole ratios of amine to reducing saccharide
is suitable for use in the present invention. In one embodiment,
the mole ratio of amine groups to reducing saccharide is in the
range of approximately 1:4 to approximately 8:1. More preferably,
the mole ratio of amine groups to reducing saccharide is in the
range of approximately 1:2 to approximately 8:1. In general,
increasing amine content results in stiffening of the resultant
gel. One skilled in the art can readily determine an appropriate
amine content for a desired set of properties for the resultant
gel.
[0017] In another aspect, the present invention provides a
composition including water; at least one hydrophilic polymer
containing at least two groups which are independently the same or
different a primary amine group or a secondary amine group and at
least one saccharide containing a reducible function as described
above. In this aspect of the present invention, the hydrophilic
polymer and the saccharide are mixed to form a reaction mixture and
reacted (that is, crosslinked) until or so that the viscosity of
the composition increases. The crosslinking reaction is then
substantially terminated (prior to completion) by reducing the pH
of the composition (for example, by adding an acid such a aqueous
hydrochloric acid). The viscosity of the composition can, for
example, be at least 20 cp at 80.degree. C. when the crosslinking
reaction is terminated. In one embodiment, the viscosity of the
composition is in the range of approximately 20 cp to 100 cp at
80.degree. C. when the reaction is terminated. The viscosity of the
composition can further, be in the range of approximately 20 cp to
60 cp at 80.degree. C. when the reaction is terminated. The
viscosity of the composition can also be in the range of
approximately 20 cp to 40 cp at 80.degree. C. when the reaction is
terminate. Preferably, the viscosity of the reduced pH composition
is no greater than 80 cp at room temperature (that is,
approximately 22.degree. C.).
[0018] The pH of the composition can, for example, be greater than
7 during reaction and reduced to less than 7 to substantially
terminate the reaction. Preferably, the pH of the composition is at
least 10 (and, more preferably, in the range of approximately 10 to
12) during reaction and reduced to 6 or less to substantially
terminate the reaction. In one embodiment, the pH of the
composition is reduced to a pH in the range of approximately 4 to 6
to substantially terminate the reaction. In another embodiment, the
pH of the composition is reduced to a pH in the range of
approximately 5 to 6 to substantially terminate the reaction. The
compositions of the present invention can be stored for extended
periods of time at a pH of 6 or less (and, for example, at room
temperature) prior to causing further crosslinking (for example, in
the strengthening of paper).
[0019] In another aspect, the present invention provides a method
of increasing the strength of a cellulosic product including the
step of contacting a wet cellulosic pulp with a composition as
described above. In one embodiment, wet cellulosic pulp (for
example, wet paper pulp) and the composition are contacted at a
temperature below approximately 50.degree. C., or more typically,
at room temperature or below (that is, at approximately 25.degree.
C. or below) and subsequently heated to induce cross-linking. For
example, the cellulosic pulp and the composition can be heated to a
temperature of at least 50.degree., at least 70.degree. or at least
90.degree..
[0020] In still a further aspect, the present invention provides a
method of increasing the strength of a cellulosic pulp product
including the steps of: contacting wet cellulosic pulp with a
composition comprising (i) at least one hydrophilic polymer
containing at least two groups which are independently the same or
different a primary amine group or a secondary amine group and at
least one saccharide containing a reducible function, the
hydrophilic polymer and the saccharide of the composition having
been reacted in a crosslinking reaction prior to contacting the
composition with the cellulosic pulp product to increase the
viscosity the composition; and, after contacting the cellulosic
pulp with the composition, causing the crosslinking reaction
between the hydrophilic polymer and the saccharide of the
composition to proceed further.
[0021] In one embodiment, prior to contacting the wet cellulosic
pulp with the composition, the hydrophilic polymer and the
saccharide are mixed to form a reaction mixture and reacted (that
is, crosslinked) until the viscosity of the composition increases.
The reaction is then substantially terminated by reducing the pH of
the composition as described above. Upon addition of such
compositions to wet cellulosic pulp, a further crosslinking (and a
resultant further increase in viscosity) is promoted by a basic
environment and heating. After addition of the composition to the
wet cellulosic pulp and further crosslinking, the wet cellulosic
pulp is dried to form a cellulosic pulp product (for example,
paper, tissue, cardboard etc.).
[0022] In still another aspect, the present invention provides a
composition formed from a mixture of water, cellulosic pulp, at
least one hydrophilic polymer containing at least two groups which
are independently the same or different a primary amine group or a
secondary amine group and at least one saccharide containing a
reducible function.
[0023] The compositions and methods of the present invention
substantially increase both the wet and dry strength of paper and
other cellulosic products. The compositions can also be used as,
for example, strengthening additives in other materials. The
compositions of the present invention can be added to the
cellulosic fibers as individual components or as a pre-gel made by
the partial reaction of the polymer(s) or copolymer(s) and the
reducible saccharide component(s). No oxidizing agents, phenolic
compounds, formaldehyde or organohalo compounds are required in the
compositions and methods of the present invention. In general, no
environmentally undesirable components are used in the compositions
and methods of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 illustrates a study of gel time at various
temperatures for a composition including a copolymer of vinyl amine
and vinyl alcohol (6 wt % vinyl amine) and D-glucose at a 1:1
sugar/copolymer ratio.
[0025] FIG. 2 illustrates the effect of addition of base upon gel
time.
[0026] FIG. 3 illustrates a study of gel time at various sugar:
copolymer ratios for a composition including a copolymer of vinyl
amine and vinyl alcohol and D-glucose.
[0027] FIG. 4 illustrates a study of gel time at various sugar:
copolymer ratios for a composition including a copolymer of vinyl
amine and vinyl alcohol and lactose.
[0028] FIG. 5 illustrates the viscosity of a composition including
a copolymer of vinyl amine and vinyl alcohol (6 wt % vinyl amine)
and D-glucose at a 1:1 sugar/copolymer ratio as a function of
time.
[0029] FIG. 6 sets forth a schematic representation of a Maillard
reaction.
DETAILED DESCRIPTION OF THE INVENTION
[0030] As discussed above, during paper processing, material is
added to the wet pulp to improve the strength during the formation
of sheets prior to ultimate drying. Preferably, the additive
material or composition exhibits a relatively low viscosity during
addition (to fully absorb into the pulp), then cures as temperature
increases. Because paper comes into intimate contact with people,
the strength-enhancing material is preferably relatively
environmentally benign.
[0031] In the present invention, environmentally friendly or benign
compositions are used to increase the wet strength (as well as the
dry strength) of paper. When individual polymer chains interact,
chemical or physical crosslinking may occur. This crosslinking
results in a three-dimensional highly branched network of
polymers.
[0032] When these networks become swollen with water they form
hydrophilic gels, known as hydrogels. Hydrogels possess unique
physical properties having attributes of both solids and liquids.
Solid-like properties can be attributed to the strength of the
crosslinked polymer networks. Whereas, fluid like properties result
from the fact that the hydrogel is typically composed of over 80%
water. The dual nature of their physical properties makes hydrogels
particularly interesting and useful, in both industry and
research.
[0033] The present inventors have discovered that water soluble
polymers having primary and/or secondary amine groups undergo a
crosslinking reaction in the presence of a reducing saccharide such
as a reducing sugar. Reducing sugars are sometimes referred to
herein simply as sugars.
[0034] Several examples of the present invention are described
using compositions including polymers with vinyl amine repeat
groups and at least one of several reducing sugars. Vinyl amine
homopolymer was found to form crosslinked polymer networks or gels
in the presence of a reducing sugar. Moreover, copolymers of vinyl
amine and at least one other monomer were also found to form
crosslinked polymer networks or gels in the presence of a reducing
sugar. In many instances, use of a copolymer of vinyl amine and at
least one other monomer is preferable to use of a vinyl amine
homopolymer in the present invention given the expense of the vinyl
amine monomer. In a number of studies of the present invention,
representative copolymers of vinyl amine and vinyl alcohol were
used. Such copolymers are also sometimes referred to herein as
poly(vinylalcohol)/poly(vinylamine) or PVOH/PVAm copolymers.
[0035] Aqueous solutions of poly(vinylalcohol)/poly(vinylamine)
copolymer and a number of sugars were found to gel readily at
temperatures between approximately 50 and 100.degree. C. In a
series of initial experiments, known amounts of sugars were mixed
with a copolymer of vinyl amine and vinyl alcohol (12 wt % vinyl
amine) to form a 40% solution (in water) by weight. The mixtures
were heated to various temperatures and held for varying lengths of
time. Gelation was determined to be the point where a Teflon stir
bar ceased to move.
[0036] Vinyl amine is required for gelation to occur. In that
regard, homopolymers of vinyl alcohol did not gel in the presence
of sugar at elevated temperature. Homopolymers of vinyl amine or
copolymers of vinyl amine and vinyl alcohol gelled readily under
these conditions. Reducing saccharide (for example, sugar) is also
required for gelation-vinyl amine homopolymers and copolymers of
vinyl amine and vinyl alcohol did not gel without the presence of
sugar. Gelation occurs over a wide range of amine: sugar
(saccharide) ratios.
[0037] Gelation occurred in the presence of 2-deoxy-D-ribose,
suggesting that the osazone mechanism was not responsible for
crosslinking. On the other hand, gelation did not occur when using
sucrose, suggesting that Maillard chemistry (known from food
chemistry) is involved in the crosslinking and hence gelation.
Prior studies suggest that no mutagenicity results from products of
the Maillard reaction when disaccharides are employed. Lactose, for
example, allows for gelation in the compositions and systems of the
present invention. Although it is believed that the Maillard
chemistry is involved in gelation in the compositions of the
present invention, the present invention is not limited to any
particular mechanism of gelation.
[0038] Increasing temperature increases the rate of the
reaction/gelation. In several experiments with a 12% (wt) amine
sample, for example, the time for gelation dropped with increasing
temperature from 335 minutes (50.degree. C.) to 113 minutes
(60.degree. C.) to 50 minutes (70.degree. C.) to 24 minutes
(80.degree. C.) to less than 10 minutes at (90.degree. C.). FIG. 1
illustrates graphically the effect of increasing temperature on gel
time for a copolymer of vinyl amine and vinyl alcohol having 6%
(wt) vinyl amine. Addition of acid (for example, H.sub.2SO.sub.4)
slowed the gelation reaction, while addition of a base (for
example, NaOH) accelerated the gelation reaction (see FIG. 2).
[0039] FIGS. 3 and 4 illustrate studies of the effect of mole ratio
of sugar to copolymer (6% by weight amine) for D-glucose and
lactose, respectively. In general, sugar concentration only
slightly effected gel time. Moreover, the type of sugar used did
not greatly affect gelation time. Lactose was found to be slightly
better than D-glucose in these studies.
[0040] A number of experiments were performed to explore the
ability of the gel to strengthen wet paper, as summarized below.
The PVOH/PVAm:glucose 2:1 sample clearly showed improved wet
strength over PVOH/PVAm without sugar and is substantially superior
to the control paper and to glucose coated paper. These results
demonstrate the effectiveness of the compositions of the present
invention in improving the wet strength and the dry strength of
paper. The temperature dependence of the rate of cross-linking of
the compositions of the present invention allows time to apply the
relatively low-viscosity mixtures of hydrophilic polymer and
reducing saccharide of the present invention to pulp fibers, with
strength properties developing in the finished sheet. Dehydration
readily occurs in the paper sheet upon drying to form a
strengthening cross-linked matrix.
[0041] In the experiments of Tables 1 and 2, a sample of PVOH/PVAm
(12 wt % vinyl amine; medium molecular weight) was dissolved at 4
wt % in distilled water. A sample of glucose was also dissolved at
4 wt % in distilled water. These samples were applied to Whatman #4
filter paper to provide even coverage.
TABLE-US-00001 TABLE 1 Dry Result Coat Weight (weight of coating/
Dry Strength Sample Description weight of paper) (lbs) Control
Paper 0 5.43 PVOH/PVAm 0.124 15.3 Glucose 0.137 4.1
PVOH/PVAm:glucose 2:1 0.118 11.7
TABLE-US-00002 TABLE 2 Wet Results Coat Weight (weight of coating/
Wet Strength Sample Description weight of paper) (lbs.) Control
Paper 0 0.095 PVOH/PVAm 0.085 0.81 Glucose 0.134 0.128
PVOH/PVAm:glucose 0.081 3.26
[0042] In several other experiments, a sample of PVOH/VAm (12 mole
% vinyl amine repeat units) was dissolved at 6 wt % in distilled
water. In these experiments, the composition including the
hydrophilic polymer PVOH/PVAm and a reducing sugar (for example,
D-glucose) was reacted prior to contact with a wet cellulosic pulp
to first increase the viscosity of the composition. Increasing the
viscosity of the composition can, for example, result in better
binding of the composition to the wet cellulosic pulp. The
crosslinking reaction can be terminated prior to completion by, for
example, reducing the pH of the composition through the addition of
an acid. Preferably, the pH of the composition is reduced to a pH
in the range of 4 to 6. It was discovered that, the compositions of
the present invention can be stored for extended periods of time at
a pH of 6 or less without substantial further crosslinking
reaction. Upon addition of such compositions to wet cellulosic
pulp, a further crosslinking (and a resultant further increase in
viscosity) is promoted by a basic environment and heating. The
compositions of the present invention can, for example, be added to
wet cellulosic pulp in the range of approximately 0.05 to 2 wt % on
the basis of the weight dry cellulosic pulp. The compositions of
the present invention can also be added in the range of
approximately 0.1 to 1 wt % based upon the weight of the dry
cellulosic pulp. The compositions of the present invention can
further be added in the range of approximately 0.1 to 0.5 wt %
based upon the weight of the dry cellulosic pulp.
[0043] Experimental
[0044] Materials. All chemicals were used without further
purification. Poly(vinylalcohol) (98-99%, Mw 31,000-50,000),
D-glucose (A.C.S. reagent) and 2-deoxy-D-ribose (97%) were
purchased from Aldrich Chemical Co. Sucrose (A.C.S. reagent) was
purchased from J. T. Baker Chemical. Lactose (A.C.S. reagent) was
purchased from E.M. Science. L-ribose (99.5%) was purchased from
Acros Organics. The poly(vinylalcohol)/poly(vinylamine) copolymers
(6 and 12% amine, medium M.sub.W) were donated by Air Products and
Chemicals Inc.
[0045] Instrumentation. Infrared spectra (IR) were obtained on an
ATI Mattson FTIR spectrometer. Information obtained was used to
determine chemical changes occurring during gelation.
[0046] Synthesis of poly(vinylamine). Poly(vinylamine) was
synthesized using N-vinyl formamide (NVF). First
poly(vinylformamide) (PNVF) was made by combining 100 mL of the NVF
monomer, 40 mL of DMSO solvent, 61 mg Vazo 88 initiator
(cyclohexane carbonitrile), and 0.5 g RAFT agent in a three-neck
flask. The mixture was then heated at 100.degree. C. for .about.2
hours under nitrogen gas with constant stirring and with reflux
conditions. After heating, the product was diluted in a 50 mL/50 mL
water/ethanol mixture. The product was then precipitated out of
solution using acetone. Product was dried overnight in a vacuum
oven, redissolved in a 120 mL/50 mL water/ethanol mixture and
subsequently precipitated using acetone. The PNVF was hydrolyzed
under basic conditions by combining the polymer, concentrated NaOH
(5% excess) and distilled deionized water in a round bottom flask.
The mixture was then heated at 80.degree. C. for 18 hours, under
reflux conditions and with constant stirring. Adding HCl to the
cold product solution precipitated the product. The product was
then washed with methanol three times and dried in a vacuum oven.
HCl was removed by adding aqueous NaOH. This product was
precipitated in acetone, dried and then washed with butanol.
EXAMPLES
Example 1
[0047] An aqueous solution was prepared by dissolving 7.5 g
D-glucose and 2.5 g poly(vinylalcohol) (PVOH) into distilled,
deionized water in a 25 mL volumetric flask. The solution was clear
with some undissolved polymer. It was, however, pourable. The
solution was transferred to a round bottom flask and heated to
80.degree. C. in an oil bath. Heating was done with constant
stirring and under reflux conditions. Upon completion the solution
remained clear with all polymer dissolved and was still
pourable.
Example 2
[0048] Prior studies suggest that an aqueous solution of PVOH and
D-glucose could be used to form hydrogels by using freezing/thawing
cycles. See Yamaura, K.; Fukada, M.; Tanaka, T.; Tanigami, T. J. of
Applied Polymer Science. 1999, 74, 1298-1303. To study this effect,
a solution was prepared as in example 1. Heating was carried out
using the same procedure as in example 1, but was allowed to reach
a temperature of 90.degree. C. The aqueous solution was then placed
in a -10.degree. C. freezer over 48 hours. After thawing the
solution at room temperature for 1 hour a weak, white hydrogel had
formed. The gel was then placed back in the freezer for 24 hours
and then thawed at room temperature for 1 hour. After which, the
gel appeared visibly stronger. This gel was found to be soluble in
water heated up to 49.degree. C. Neither swelling nor dissolution
was noted when placed in 1M HCl.
Example 3
[0049] Prior studies further suggest that D-glucose was not
necessary for the gelation of poly(vinylalcohol) using the process
in example 2. See Yamaura, K.; Karasawa, K. I.; Tanigami, T.;
Matsuzawa, S. J. of Applied Polymer Science. 1994, 51, 2041-2046.
To study such gelation, a 2.5 g of PVOH was dissolved in distilled,
deionized water in a 25 mL volumetric flask. Heating was carried
out using the same procedure as in example 1, but was allowed to
reach a temperature of 95.degree. C. The solution was then placed
in the freezer at -25.degree. C. for 48 hours. After 1 hour of
thawing at room temperature a gel, similar in appearance to the gel
in Example 2, was produced. The inability of PVOH to form hydrogels
without the freezing/thawing cycle indicated that the amine groups
on copolymers of PVOH and Poly(vinylamine) in the compositions of
the present invention are responsible for gelation.
Example 4
[0050] Poly(vinylamine) (PVA) was also used in trying to make gels.
An excess of PVA was used in the case that some butanol was still
present in the synthesized polymer. 2.8 g of PVA was dissolved in
distilled, deionized water in 25 mL volumetric glassware leaving
room for the addition of D-glucose and more water. A heating gun
was used, as needed, to dissolve polymer. D-glucose was dissolved
in some water in a separate container, added to the other solution
and diluted as necessary. This solution was orange in color and
pourable. Heating was carried out using the same procedure as in
example 1, but was allowed to reach a temperature of 100.degree. C.
A rubbery, dark brown gel began to appear at .about.95.degree. C.
This gel swelled when exposed to both excess water and 1M HCl.
Example 5
[0051] To ensure that the discoloration observed in Example 4 was a
result of gelation and not merely oxidation of the amine, Example 4
was repeated under nitrogen gas. This was done using a three neck
flask, rubber septum and needle. The rubbery, dark brown gel
appeared at .about.93.degree. C. again. This gel was slightly
lighter in color than the gel of Example 5. This gel swelled in
water and in 1M HCl.
Example 6
[0052] To study whether a sugar was necessary for gelation, 1.25 g
of PVA was dissolved in water in a 25 mL volumetric flask. This
solution was then heated to 95.degree. C. using the procedure of
Example 1. No gelation was observed.
Example 7
[0053] The poly(vinylalcohol)/poly(vinylamine) copolymer that was
used for the experiments set forth in Examples 7 through 24
contained 12% amine groups. 2.5 g of the copolymer followed by 7.5
g of D-glucose were dissolved in distilled deionized water using
the procedure outlined in Example 4. This solution was then
transferred to a three-neck flask and heated in an oil bath to
100.degree. C. Heating was carried out under reflux conditions,
with constant stirring and under argon gas. A strong, bright yellow
gel appeared at .about.90.degree. C. This gel swelled when exposed
to excess water and to 1M HCl.
Example 8
[0054] The procedure in example 7 was repeated using 2.5 g
D-glucose. This is a 1:2 mole ratio of amine groups to sugar
molecules. Gelation began to occur at .about.90.degree. C. This gel
was strong and yellow. It swelled in water and 1M HCl.
Example 9
[0055] The procedure of Example 7 was repeated using 1.25 g
D-glucose (a 1:1 mole ratio of amine groups to sugar molecules).
Gelation began to occur at .about.90.degree. C. This gel was a pale
yellow color. This gel is still strong but not as strong as the
previous two examples. Swelling was noted in water and 1M HCl. IR
spectra were taken of the aqueous solution before heating and of
this gel afterwards. Before heating a strong peak was seen around
1680 cm.sup.-1, which is typical of a primary amine peak. After
heating this peak became much smaller, more typical of a secondary
amine. Another unidentified peak appeared after heating at
.about.1090 cm.sup.-1.
Example 10
[0056] The procedure of Example 7 was repeated using 0.61 g
D-glucose (a 2:1 mole ratio of amine groups to sugar molecules).
Gelation began to occur at .about.95.degree. C. This gel was strong
yet somewhat sticky and a clear yellow color. Swelling was noted
when exposed to water and to 1M HCl.
Example 11
[0057] The procedure of Example 7 was repeated using 0.31 g
D-glucose (a 4:1 mole ratio of amine groups to sugar molecules).
Gelation began to occur at .about.100.degree. C. The gel produced
was sticky and almost clear in color. This gel swelled when exposed
to excess water and to 1M HCl.
Example 12
[0058] The procedure of Example 7 was repeated using 0.16 g
D-glucose (a 8:1 mole ratio of amine groups to sugar molecules).
Gelation began to occur at .about.100.degree. C. This gel was
sticky and clear. Swelling occurred when exposed to water and to 1M
HCl.
Example 13
[0059] To test for the possibility of an osazone mechanism L-ribose
was used instead of D-glucose. The procedure followed was similar
to that of example 9 (using a 1:1 mole ratio and the same
conditions). 1.02 g of L-ribose was used. Gelation occurred at
.about.85.degree. C. This gel was strong, sticky and bright orange
in color. This gel swelled when exposed to excess water and to 1M
HCl.
Example 14
[0060] As part of the aforementioned test of reaction mechanism
2-deoxy-D-ribose was also used instead of D-glucose. The procedure
of Example 9 was once again followed, this time using 0.91 g of
2-deoxy-D-ribose. Gelation occurred at .about.85.degree. C. This
gel was also strong and bright orange. The gelation of
2-deoxy-D-ribose indicates that the osazone reaction is not taking
place since it would be unable to occur as a result of the
structure of this sugar. Without limitation to any particular
reaction mechanism in the present invention, a Maillard reaction
mechanism is thus indicated. The gel of this example swelled when
exposed to excess water and to 1M HCl.
Example 15
[0061] Prior studies show that little or no mutagenicity results
from the Maillard reaction when disaccharides, such as lactose, are
involved. See, for example, Brands, C. M. J.; Alink, G. M.;
vanBoekel, M. A. J. S.; Jongen, W. M. F. J. Agric. Food Chem. 2000,
48, 2271-2275. A summary of the Maillard reaction is provided in
FIG. 6. Thus lactose is a good sugar for use in the present
invention. The procedure of Example 9 was used, with 2.45 g of
lactose. A strong, orange gel formed at .about.100.degree. C.
Solubility tests were not carried out on this gel.
Example 16
[0062] Sucrose is a disaccharide lacking active carbonyl groups.
Therefore, sucrose would not be able to form a gel via the Maillard
reaction. See Baynes, J. W.; Monnier, V. M. "The Maillard Reaction
in Aging, Diabetes and Nutrition" 1989; and O'Brien, J.; Nursten,
H. E.; Crabbe, M. J. C.; Ames, J. M. "The Maillard Reaction in
Foods and Medicine" 1998. The procedure from example 9 was once
again repeated. In this example, time 2.33 g of sucrose was used.
The temperature was taken up to 115.degree. C. and gelation was not
observed.
Example 17
[0063] Constant temperature experiments were also carried out. 2.5
g of copolymer followed by 1.25 g of D-glucose were dissolved in
water using a 25 mL volumetric flask as outlined in Example 4.
Heating took place in an oil bath that was maintained at a constant
temperature of 80.degree. C. Heating was done under reflux
conditions, under argon gas and with constant stirring. Gelation
time was noted as the time when the gel became too viscous for the
stir bar to move. In this example gelation time was found to be
23.5 minutes. The gel produced was a clear yellow and sticky. This
gel dissolved in water.
Example 18
[0064] The procedure of Example 17 was repeated using an oil bath
at 70.degree. C. Gelation time was noted as 49.5 minutes. This gel
was weaker and stickier than the previous one. This gel also
dissolved in water.
Example 19
[0065] The procedure of Example 17 was repeated using an oil bath
at 60.degree. C. Gelation time was noted as 113.25 minutes. This
gel was weaker and stickier than the previous one. This gel also
dissolved in water.
Example 20
[0066] The procedure of Example 17 was repeated using an oil bath
at 50.degree. C. Gelation time was noted as 335.0 minutes. This gel
was weaker and stickier than the previous one. This gel also
dissolved in water.
Example 21
[0067] To test the effect of pH on gelation, the procedure of
Example 17 was repeated under acidic conditions. Three drops of
concentrated H.sub.2SO.sub.4 were added to the aqueous solution.
After 120.0 minutes the solution had turned slightly yellow and
appeared to be a pourable gel. This gel was also soluble in
water.
Example 22
[0068] Basic conditions were also examined using the procedure in
example 17. 0.04 g of concentrated NaOH were added to the aqueous
solution. Gelation was noted after 18.2 minutes. This gel was
similar in appearance to that produced in Example 17. This gel was
slightly soluble in excess water.
Example 23
[0069] The gels studied in FIGS. 1 through 5 were synthesized in a
consistent manner. In that regard, 21.25 grams of copolymer was
weighed out into a beaker and set aside for both 6 wt % and 12 wt %
amine copolymers. The sugar was also weighed out in a beaker and
set aside. The amount of sugar added depended on the mole ratio of
sugar to amine, which is indicated in Table 3 below for each
ratio.
TABLE-US-00003 TABLE 3 Molar Ratio (sugar:amine) And Type of Sugar
Amount of Sugar (grams) 1:1 glucose 5.23 2:1 glucose 10.46 4:1
glucose 20.92 1:2 lactose 5.23 1:1 lactose 10.46 2:1 lactose
20.92
The saccharide (sugar):amine rations set forth in Table 3 and FIGS.
3 and 4 are merely the reciprocal of amine:sugar mole ratios.
[0070] Deionized water was measured out in a tall form beaker to
approximately 425 mL. A small amount (.about.1/4) of this water was
put into another tall form beaker and the sugar was added and mixed
thoroughly. The bulk of the water was used to mix with the
copolymer. The mixture of copolymer/water was then put into an oil
bath and mixed to allow the copolymer to dissolve. Next, the
sugar/water mixture was added into the copolymer mixture and the
time was started. The UL adapter was then lowered into the mixture
and the Brookfield viscometer was turned on to a speed of 60 (The
Brookfield viscometer had been earlier calibrated with water). The
readings form the Brookfield were not recorded until after the time
had reached 9 minutes to allow the UL adapter to settle. The time
was then recorded after each minute. The only other change in
procedure occurred when the NaOH was added [50% (w/w/) NaOH in
water solution]. 31 mM of NaOH (or 1 gram of the NaOH in water
solution) was added into the sugar/water mixture before adding it
to the copolymer mixture.
Example 24
[0071] In several studies of the effect of the compositions of the
present invention upon wet and dry strength of paper, a sample of
PVOH/PVAm (12 wt % VAm; medium molecular weight) was dissolved at 4
wt % in distilled water. A sample of glucose was also dissolved at
4 wt % in distilled water. These samples were applied to Whatman #4
filter paper from a 6'' roll using a wire wound rod (RDS40) to
provide even coverage. 50 grams of the 4 wt % solution of PVOH/PVAm
were mixed with 25 grams of the 4 wt % solution of glucose and also
coated on the above noted filter paper using a wire wound rod to
provide even coverage. The samples were placed in an air
circulating oven for 10 minutes at 100.degree. C. The samples were
removed and conditioned at 23.degree. C.; 50.degree./'' RH for 16
hours prior to testing. 1'' wide strips were cut transverse to the
filter paper roll direction and cut into two 3'' long specimens for
dry tensile testing. Samples were also cut into 3'' long specimens
and immersed in water for 30 seconds and tested for wet tensile
strength. The results are set forth in Table 1 and 2 above. The
sample weights were measured to determine coat weights (amount of
additive on the coated paper versus the uncoated paper). Data on an
average of four specimens is set forth in Tables 1 and 2. The
testing rate was 2 in./min. strain rate (2 in. gage length).
Example 25
[0072] The polymer used in this example and the following examples
was a copolymer of vinyl alcohol and vinylamine (PVOH/VAm),
containing 12 mole % vinylamine repeat units, with a medium
molecular weight. Although any reducing sugar may be used,
D-glucose was used in this and the following examples. Twelve (12)
grams of PVOH/VAm were dissolved in 200 grams of water. The
solution was heated to 90.degree. C. and then filtered to remove
any insoluble material. With the solution temperature maintained at
80.degree. C., six grams of D-glucose was added, followed by
sufficient 30% sodium hydroxide solution to bring the solution pH
to at least 10, preferably approximately 12. With continued heating
in the 80-90.degree. C. range the solution converts to a thick
viscous gel. The relationship between time to gelation and
temperature is illustrated in Table 4 for the crosslinking of
PVOH/VAm with D-glucose at a 1:1 mole ratio and a pH of 12.5.
TABLE-US-00004 TABLE 4 Temperature (.degree. C.) Time to gelation
22 66 hours 30 28 hours 40 22 hours 50 5 hours 60 40 minutes 80
10-20 minutes
Example 26
[0073] As in Example 25, twelve grams of PVOH/VAm were dissolved in
200 grams of water, heated to 90.degree. C. and filtered to remove
insoluble material. Maintaining the solution temperature at
80.degree. C., six grams of D-glucose were added, followed by
sufficient 30% aqueous sodium hydroxide to bring the solution pH to
at least 10. The initial viscosity was 17 cps. After approximately
twenty minutes at 80.degree. C., the viscosity had risen to 40 cps.
Once the viscosity reached 40 cps, the solution pH was adjusted to
6 by addition of 33% hydrochloric acid solution. The viscosity was
measured as 22 cps at 80.degree. C. and 80 cps at 23.degree. C. The
solution does not gel and can be stored at room temperature for
several weeks without any evidence of gel formation.
Example 27
[0074] A dynamic handsheet maker (Techpap) was employed to make
paper samples for testing. Sixteen (16) grams of dry cellulosic
fiber were used to make a slurry in water at 1% consistency. The pH
of the slurry was adjusted to the desired level and the
acid-stabilized PVOH/VAm/D-glucose from Example 26 added at a level
of 0.5 weight % (equivalent to 10 lb/ton) based on the amount of
dry fiber in the slurry. The rotation speed of the handsheet maker
was set at 680 rpm and pressure applied to form the paper sheet.
The wet paper web was pressed and dried at 115.degree. C. for eight
minutes. The paper sheets were conditioned at 23.degree. C. and 50%
relative humidity for one day. The treated paper sheets were then
tested for wet tensile, dry tensile and burst strength using
standard tests. The results were normalized to allow for
differences in thickness and grammage for each sheet.
Example 28
[0075] Paper sheets were made up as in Example 27, both with and
without the polymer additive. The PVOH/VAm/D-glucose solution was
heated for 30 minutes at 80.degree. C. before adding to the fiber
suspension. The final viscosity (at room temperature) was 80 cps.
The results are summarized in Table 5.
TABLE-US-00005 TABLE 5 Additive None PVOH/VAm/D-glucose pH 5.5 5.5
DBL (km) 3.646 4.173 WBL (km) 0.054 0.332 WBL/DBL (%) 1.5 8.00 In
Table 5, "DBL" refers to Dry breaking length, while "WBL" refers to
Wet breaking length
Example 29
[0076] Paper sheets were made as in Example 27, using the PVOH/VAm
both with and without added D-glucose. The copolymer/glucose
solution was heated at 80.degree. C. for 30 minutes before use and
the final viscosity at room temperature was 68 cps. The results are
summarized Table 6.
TABLE-US-00006 TABLE 6 Additive None PVOH/VAm PVOH/VAm/D-glucose pH
5.5 8 8 DBL (km) 3.646 3.934 3.912 WBL (km) 0.054 0.326 0.361
WBL/DBL (%) 1.50 8.30 9.20
Example 30
[0077] Paper sheets were made as in Example 27, both with and
without polymer additive. The PVOH/VAm/D-glucose was heated at
80.degree. C. until a final viscosity of 225 cps (as measured at
room temperature) was reached. The results are summarized in Table
7.
TABLE-US-00007 TABLE 7 Additive None PVOH/VAm/D-glucose pH 5.5 5.5
DBL (km) 3.646 4.39 WBL (km) 0.054 0.352 WBL/DBL (%) 1.50 8.01
Example 31
[0078] Paper sheets were made as in Example 27, both with and
without polymer additive. The PVOH/VAm/D-glucose samples were
heated for different times at 60.degree. C. prior to use. The
results are summarized in Table 8.
TABLE-US-00008 TABLE 8 PVOH/ PVOH/ PVOH/ VAm/D- VAm/D- VAm/D-
Additive None glucose glucose glucose Reaction Time -- 12 22 33
(mins) Viscosity -- 53 71 83 (cps) pH 5.5 5.5 5.5 5.5 DBL (km)
3.291 3.37 3.638 3.61 WBL (km) 0.051 0.357 0.373 0.367 WBL/DBL (%)
1.5 10.6 10.3 10.2
Example 32
[0079] A paper-making trial was conducted on a pilot-scale paper
machine. The machine used was a Fourdrinier (width 25 inches), with
a nominal paper output of 160 lbs paper per hour. The pulps used
were old corrugated containers (OCC) and a mix of OCC with recycled
newsprint. Polymer was added in the range of 2-10 lbs/ton on a dry
basis. Sample sheets were cut from the paper reel and conditioned
in the same fashion as the hand-sheets in Example 27. Results were
normalized for thickness and weight. The PVOH/VAm solution was
prepared as in Example 26, filtered and stored in a drum. D-glucose
was added to this stock solution, pH adjusted to 12 and the
solution was then heated to 80.degree. C., while monitoring
viscosity. Measured viscosities were below 100 cps during use of
the solution.
Example 33
[0080] Paper was made on the pilot machine using old corrugated
containers (OCC) as the fiber source. The paper produced was 26-28
lbs per 1,000 square feet, with a caliper of approximately 9.0. A
base sheet was produced with no additive. Then PVOH/VAm/D-glucose
(P) was fed to the paper stock at a rate to give a 2 to 10 lb per
ton (0.1-0.5%) application level on a dry basis. Results are
summarized in Table 9. Properties reported were measured in the
machine direction.
TABLE-US-00009 TABLE 9 P P P P P Additive None (0.1%) (0.2%) (0.3%)
(0.4%) (0.5%) DBL (km) 6.407 6.469 6.005 6.402 5.903 5.917 WBL (km)
0.38 0.25 0.45 0.50 0.47 0.51 WBL/DBL (%) 5.9 3.9 7.5 7.8 8.0 8.5
Burst Index 2.683 2.878 2.804 2.787 2.711 2.597
Example 34
[0081] Paper was made as in Example 33, but using a mixture of OCC
and old newsprint as fiber source. A base sheet was produced with
no additive. Then PVOH/PVAm/D-glucose (P) was added at levels
sufficient to give 6 and 8 lb/ton (0.3 and 0.4%) application
levels. Properties reported were measured in the machine direction
and are summarized in Table 10.
TABLE-US-00010 TABLE 10 Additive None P (0.3%) P (0.4%) DBL (km)
5.598 5.654 5.715 WBL (km) 0.19 0.35 0.52 WBL/DBL (%) 3.4 6.2 9.1
Burst Index 2.489 2.473 2.672
Example 35
[0082] The procedure of Example 34 was repeated, using
PVOH/VAm/D-glucose (P) solution that had been aged for several
hours to an increased viscosity. The polymer was added at levels
sufficient to give 6 and 8 lb/ton (0.3 and 0.4%) application
levels. Properties reported were measured in the machine direction
and are summarized in Table 11.
TABLE-US-00011 TABLE 11 Additive None P (0.3%) P (0.4%) DBL (km)
5.598 5.524 5.909 WBL (km) 0.19 0.47 0.58 WBL/DBL (%) 3.4 8.5 9.8
Burst Index 2.489 2.676 2.837
[0083] The foregoing description and accompanying drawings set
forth preferred embodiments of the invention at the present time.
Various modifications, additions and alternative designs will, of
course, become apparent to those skilled in the art in light of the
foregoing teachings without departing from the scope of the
invention. The scope of the invention is indicated by the following
claims rather than by the foregoing description. All changes and
variations that fall within the meaning and range of equivalency of
the claims are to be embraced within their scope.
* * * * *