U.S. patent application number 12/621848 was filed with the patent office on 2010-10-07 for pulp and paper having increased brightness.
This patent application is currently assigned to INTERNATIONAL PAPER COMPANY. Invention is credited to Xuan Troung Nguyen.
Application Number | 20100252213 12/621848 |
Document ID | / |
Family ID | 38670503 |
Filed Date | 2010-10-07 |
United States Patent
Application |
20100252213 |
Kind Code |
A1 |
Nguyen; Xuan Troung |
October 7, 2010 |
PULP AND PAPER HAVING INCREASED BRIGHTNESS
Abstract
The present invention relates to a method of increasing the
brightness of pulp, pulp made from such methods and methods of
using such pulp.
Inventors: |
Nguyen; Xuan Troung;
(Cincinnati, OH) |
Correspondence
Address: |
INTERNATIONAL PAPER COMPANY
6285 TRI-RIDGE BOULEVARD
LOVELAND
OH
45140
US
|
Assignee: |
INTERNATIONAL PAPER COMPANY
Memphis
TN
|
Family ID: |
38670503 |
Appl. No.: |
12/621848 |
Filed: |
November 19, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11445809 |
Jun 2, 2006 |
7638016 |
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12621848 |
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11358543 |
Feb 21, 2006 |
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11445809 |
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60654712 |
Feb 19, 2005 |
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Current U.S.
Class: |
162/28 ; 162/100;
162/87 |
Current CPC
Class: |
D21H 21/30 20130101;
D21C 9/005 20130101; D21C 9/123 20130101; D21H 21/32 20130101; D21C
9/1026 20130101; D21C 9/14 20130101 |
Class at
Publication: |
162/28 ; 162/87;
162/100 |
International
Class: |
D21C 9/12 20060101
D21C009/12; D21C 3/26 20060101 D21C003/26; D21H 21/32 20060101
D21H021/32 |
Claims
1. A method of making pulp and/or a paper substrate, comprising
contacting a plurality of fibers in solution with at least one
optical brightener after the last bleaching/extraction stage with a
chlorine based bleaching agent.
2. The method according to claim 1, wherein the contacting is
performed at a point in the pulp making or papermaking process
prior to a Blend Chest/Machine Chest Stages.
3. The method according to claim 1, wherein the fibers in solution
are at a consistency of greater than about 4%.
4. The method according to claim 1, wherein the fibers in solution
are a consistency of from 7 to 15%.
5. The method according to claim 1, wherein from 1 to 15 lbs/ton of
OBA is contacted with the fibers.
6. The method according to claim 1, wherein the pH of the solution
during the contacting of the OBA with fibers is from 3.5 to
5.5.
7. The method according to claim 1, wherein the temperature when
the OBA is contacted with the fibers is from 60 to 80.degree.
C.
8. The method according to claim 1, wherein the OBA is contacted
with the fibers for a duration of time of from 0.5 to 6 hours.
9. The method according to claim 1, wherein the contacting is
performed at a point in the pulp making or papermaking process
prior to a refining stage.
10. The method according to claim 1, comprising contacting a
plurality of fibers in solution with at least one optical
brightener after the last bleaching/extraction stage in the absence
of a retention aid.
11. The method according to claim 1, further comprising refining
the fibers and OBA wherein the refining is selected from at least
one member selected from the group consisting of chemical refining,
mechanical refining, thermochemical refining, thermomechanical
refining, and chemithermomechanical refining.
12. The pulp made by the method according to claim 1.
13. The pulp made by the method according to claim 1, wherein the
pulp is bleached chemithermomechanical pulp.
14. The pulp made by the method according to claim 1, wherein the
pulp is fluff pulp.
15. The pulp made by the method according to claim 1, wherein the
pulp is papermaking pulp.
16. The pulp or paper substrate made by the method according to
claim 1, wherein the pulp or paper substrate has an ISO brightness
that is not less than 90.
17. The pulp or paper substrate made by the method according to
claim 1, wherein the pulp or paper substrate has a CIE whiteness
that is not less than 130.
18. The pulp or paper substrate made by the method according to
claim 1, wherein the pulp or paper substrate has a CIE whiteness
that is not less than 130 and an ISO brightness that is not less
than 90.
19. The method according to claim 1, further comprising contacting
additional OBA with the fibers at a coater.
20. The method according to claim 1, further comprising contacting
additional OBA with the fibers at a size press.
Description
[0001] This application claims the benefit of U.S. provisional
application Ser. No. 60/654,712, filed Feb. 19, 2005, and claims
priority from U.S. application Ser. No. 11/358,543, filed Feb. 21,
2006, and entitled "pulp and paper having increased brightness",
which are hereby incorporated, in their entirety, herein by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a method of increasing the
brightness of pulp, pulp made from such methods and methods of
using such pulp.
BACKGROUND OF THE INVENTION
[0003] Bleaching is a common method for increasing the whiteness of
pulp. Industry practice for improving appearance of fluff pulp is
to bleach the pulp to ever-higher levels of brightness (the
Technical Association of the Pulp & Paper Industry ("TAPPI") or
the International Organization for Standardization ("ISO")).
However, bleaching is expensive, environmentally harsh and often is
a source of manufacturing bottleneck. Widespread consumer
preference for a brighter, whiter pulp drives manufacturers to
pursue ever more aggressive bleaching strategies. While highly
bleached pulps are "whiter" than their less-bleached cousins, they
are still yellow-white in color. A yellow-white product is
undesirable. Countless studies suggest that consumers clearly favor
a blue-white over a yellow-white color. The former is perceived to
be whiter, i.e., "fresh", "new" and "clean", while the latter is
judged to be "old", "faded", and "dirty".
[0004] While bleaching directly elevates brightness, it only
indirectly elevates whiteness. Due to the latter, bleaching is not
always the most efficient method for boosting product whiteness.
For example, even after aggressive bleaching, a product's whiteness
can always be extended beyond that achievable with bleaching alone
by judicious addition of colorant.
[0005] The practice of pre-coloring papermaking pulp is not usually
done nor is it necessarily desired. With the former, intentional
alteration of optical properties often ends up degrading product
specifications such as TAPPI brightness, which is undesirable. With
the latter, one runs the risk that colorants may not survive the
unpredictable manufacturing environments of downstream processes.
This is because previously applied colorant can be adversely
affected chemically and/or physically during post-processing
operations resulting in unexpected or undesirable color changes or
even full loss of color. Furthermore, some colorants can be lost or
rendered ineffective during various post-processing operations
disrupting process health and reliability. Therefore, any optical
enhancement is usually accomplished by addition of tinting
colorants, fillers, and/or fluorescent dye during the papermaking
stage. A process for enhancing the whiteness, brightness, and
chromaticity of papermaking fibers has been described in U.S. Pat.
No. 5,482,514. The process relates to adding photoactivators,
particularly water-soluble phthalocyanines, to papermaking fibers
to enhance their optical properties by a catalytic photosensitizer
bleaching process. The resulting bleached papermaking fibers can be
advantageously incorporated into paper sheets.
[0006] With fluff pulp, as well as most pulp and paper products,
TAPPI brightness serves as the de facto standard in lieu of an
industry-specific whiteness specification such as CIE Whiteness
(Commission Internationale d'Eclairage). Because of this,
brightness serves two key roles. First, brightness is a
manufacturing parameter. Second, brightness is a specification for
classifying finished product grades. The implicit, but dubious,
assumption to this day has been that brightness is equivalent to
whiteness. Common papermaking practice is to either add blue
tinting dyes or tinting pigments and/or different types of
blue-violet fluorescent dyes to boost whiteness properties. Tinting
colorants are either finely ground colored pigments suspended in a
dispersant or synthetically produced direct dyes. Tinting dyes have
some affinity to cellulose while tinting pigments have little to
none.
[0007] Fluorescent whitening agents (FWA) or optical brightening
agents (OBA) are used in the pulp and paper industry are of three
types: di-, tetra-, or hexasulphonated stilbene compounds, for
example. These chemicals require ultraviolet (UV) light to excite
fluorescence. While there is strong UV content in daylight, even
common office lights produce enough UV light to permit some
excitation. During papermaking, OBAs are added at the wet end of
papermaking processes, which include for example, the machine chest
and/or the fan pump, where the fiber solution is at low
consistencies that are less than about 3% solids. At these
conventional addition points, much OBA is lost to waste as the OBA
does not necessarily have a strong affinity to the fibers in
solution. Accordingly, the OBA must be added at high concentrations
(lbs/ton of fiber or pulp) in order to achieve high quality fibers
having high brightness and high brightness improvements.
[0008] Accordingly, there exists a need for a pulp having improved
whiteness and brightness. A need also exists for a method for
making whitened/brightened pulp for any use, especially papermaking
and fluff pulp, while using less OBA to obtain such levels of
whiteness and brightness at less cost. The present invention seeks
to fulfill these needs and provides further related advantages.
SUMMARY OF THE INVENTION
[0009] One aspect of this invention relates to a method of
brightening pulp fibers comprising contacting a plurality of the
fibers with at least one optical brightener at any time after the
last bleaching/extraction stage with a chlorine based bleaching
agent and upto and prior to treatment of the fibers with
papermaking chemicals as for example at the. Another aspect of this
invention relates to brightened pulp fibers produced by the method
of this invention preferably having a CIE whiteness that is not
less than 130, an ISO brightness that is not less than 90 or a CIE
whiteness that is not less than 130 and an ISO brightness that is
not less than 90. Yet another aspect of this invention relates to a
paper or paperboard substrate comprising the pulp fibers of this
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1: Graphs of ISO Brightness v.s OBA Level of Handsheets
made from pulp treated with OBA, full data set.
[0011] FIG. 2: Graphs of ISO Brightness v.s OBA Level of Handsheets
made from pulp treated with OBA, dose data set.
[0012] FIG. 3: Graphs of ISO Brightness v.s OBA Level of Handsheets
made from pulp treated with OBA, effect of OBA dose in the presence
of 10 and 20% filler.
[0013] FIG. 4: Graphs of ISO Brightness v.s OBA Level of Handsheets
made from pulp treated with OBA effect of OBA dose in the presence
of 10 and 20% filler, regression lines added.
[0014] FIG. 5: Raman spectra of OBA only and pulp with different
levels of OBA added conventionally.
[0015] FIG. 6: Raman spectra of pulp with different levels of OBA
added according to one aspect of the present invention.
[0016] FIG. 7: Raman spectra of pulp with different levels of OBA
added conventionally and added according to one aspect of the
present invention.
[0017] FIG. 8: Graph of the peak ratio (1604/900cm.sup.-1) within
Raman spectra of pulp with different levels of OBA added
conventionally and added according to one aspect of the present
invention (Hardwood and Softwood) as depicted in Table 10.
[0018] FIG. 9: UV/VIS absorbance at 350 nm of water estract vs.
Actual Amount of OBA on fibers, lbs/ton.
[0019] FIG. 10: OBA peak height vs. OBA added (lbs/ton) via the
conventional addition method and added according to one aspect of
the present invention (Hardwood and Softwood).
[0020] FIG. 11: OBA peak height vs. OBA added (lbs/ton) via the
conventional addition method and added according to one aspect of
the present invention (Hardwood and Softwood).
DETAILED DESCRIPTION OF THE INVENTION
[0021] The present inventor has surprisingly found a method of
efficiently increasing the brightness and whiteness of pulp and
paper while using less OBA applied thereto, thereby providing for a
much more efficient manner of providing a fiber-OBA complex
containing greater fiber-OBA interaction on the whole than
conventional methodologies of creating a fiber-OBA complex. Such a
fiber-OBA complex made by the method according to the present
invention has greater increases in brightness and whiteness than
the fiber alone as compared to traditional methodologies as
described below.
[0022] The present invention relates, in part, to a method of
making pulp. The pulp may be fluff or papermaking pulp. The method
may be used and added to any traditional methods of making
papermaking or fluff pulp. The pulp may be used in any conventional
uses of pulp, including any conventional papermaking processes of
making paper and/or paperboard substrates. Such conventional pulp
and papermaking processes in the pulp, paper and paperboard art may
be found, for example, in "Handbook For Pulp & Paper
Technologies", 2.sup.nd Edition, G. A. Smook, Angus Wilde
Publications (1992) and references cited therein, which are hereby
incorporated, in their entirety, herein by reference.
[0023] A typical pulp/paper making process may include, but is not
limited to, the following stages:
[0024] A. Digesting stage where wood chips are digested to release
pulp fibers from the lignin;
[0025] B. Brownstock Washing Stage where the pulp from the
Digesting Stage is washed;
[0026] C. Bleaching/Extraction Stages where the pulp is extracted
with and bleached with various chemicals such as oxygen in oxygen
delignification, chlorine dioxide, elemental chlorine, peroxide,
ozone, and the like followed by one or more washing stages;
[0027] D. High Density Storage Stage where the bleached/washed pulp
is stored at relatively high density as for example preferably more
than about 7%, more preferably from about 7.5 to about 15%, and
most preferably from about 10 to about 12%;
[0028] E. Low Density Storage Stage where the bleached/washed pulp
is stored at relatively low density as for example preferably equal
to or less than about 7%, more preferably from about 3% to 7%, and
most preferably from about 10 to about 12%;
[0029] F. Pulp Refining Stage where the pulp is refined at a
consistency preferably of from about 4 to about 5%;
[0030] G. Blend Chest/Machine Chest Stages where the pulp having a
consistency preferably from about 3 to about 4% is mixed with wet
end chemicals used in paper making such as fillers, retention aids,
dyes and optical brighteners and the like. Such a traditional
processes may include repeats of any one or more of the
above-mentioned steps. In addition, the present invention may be
combined with traditional methods of adding OBA to fibers, such as
the conventional wet-end addition points as well as size press
addition points and coating addition points, when making paper
and/or paperboard.
[0031] The present invention relates, in part, to a method of
adding OBA to fibers at any point after the last
bleaching/extraction stage with chlorine based bleaching agents
such as elemental chlorine and chlorine dioxide and up to and prior
to treatment of pulp with papermaking chemicals such as in the
Blend Chest/Machine Chest Stages. For example, the pulp fibers can
be treated during any non-chlorine based bleaching/extraction stage
after the last chlorine based bleaching stage, if any. Illustrative
of such non-chlorine bleaching stages are those in which the pulp
is treated with oxygen, ozone, peroxides, per-oxy acids, acid
derivatives of hydrogen peroxide (such as peroxyrnono sulfuric acid
and peroxyacetic acid), dimethyl dioxirane, sodium hydrosulfite,
sodium bisulfite, zinc hydrosulfite and any other non-chlorine
based bleaching such as those described in "The Bleaching of Pulp"
3.sup.rd Ed. RP. Singh, TAPPI PRESS, Atlanta, Ga. 1979. As further
examples, the pulp can be treated with the OBA in High Density
Storage Stage where the bleached/washed pulp is stored at
relatively high density; in Low Density Storage Stage where the
bleached/washed pulp is stored at relatively low density; in Pulp
Refining Stage where the pulp is refined at a consistency
preferably of from about 4 to about 5%; or any combination
thereof.
[0032] The source of the fibers may be from any fibrous plant.
Examples of such fibrous plants are trees, including hardwood and
softwood fibrous trees, including mixtures thereof. In certain
embodiments, at least a portion of the pulp fibers may be provided
from non-woody herbaceous plants including, but not limited to,
kenaf, hemp, jute, flax, sisal, or abaca although legal
restrictions and other considerations may make the utilization of
hemp and other fiber sources impractical or impossible. Either
bleached or unbleached pulp fiber may be utilized in the process of
this invention. The fibers can be recycled fibers, deinked fibers
and/or virgin fibers, but are preferably virgin fibers.
[0033] The pulp of the present invention may contain from 1 to 99
wt %, preferably from 5 to 95 wt %, cellulose fibers originating
from hardwood species and/or softwood species based upon the total
amount of cellulose fibers. This range includes 1, 2, 5, 10, 15,
20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, and
100wt %, including any and all ranges and subranges therein, based
upon the total amount of cellulose fibers.
[0034] When the pulp may contain both hardwood and softwood fibers,
it is preferable that the hardwood/softwood ratio be from 0.001 to
1000. This range may include 0.001, 0.002, 0.005, 0.01, 0.02, 0.05,
0.1, 0.2, 0.5, 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60,
65, 70, 75, 80, 85, 90, 95, 100, 200, 300, 400, 500, 600, 700, 800,
900, and 1000 including any and all ranges and subranges therein
and well as any ranges and subranges therein the inverse of such
ratios.
[0035] Optical brightening agents ("OBAs") used in the practice of
the process of this invention may vary widely and any conventional
OBA used or which can be used to brighten mechanical or Kraft pulp
can be used in the conduct of the process of this invention.
Optical brighteners are dye-like fluorescent compounds which absorb
the short-wave ultraviolet light not visible to the human eye and
emit it as longer-wave blue light, with the result that the human
eye perceives a higher degree of whiteness and the degree of
whiteness is thus increased. This provides added brightness and can
offset the natural yellow cast of a substrate such as paper.
Optical brighteners used in the present invention may vary widely
and any suitable optical brightener may be used. An overview of
such brighteners is to be found, for example, in Ullmann's
Encyclopedia of Industrial Chemistry, Sixth Edition, 2000
Electronic Release, OPTICAL BRIGHTENERS--Chemistry of Technical
Products which is hereby incorporated, in its entirety, herein by
reference. Other useful optical brighteners are described in U.S.
Pat. Nos. 5,902,454; 6,723,846; 6,890,454; 5,482,514; 6,893,473;
6,723,846; 6,890,454; 6,426,382; 4,169,810; and 5,902,454 and
references cited therein which are all incorporated by reference.
Still other useful optical brighteners are described in; and U.S.
Pat. Application Publication Nos. US 2004/014910 and US
2003/0013628; and WO 96/00221 and references cited therein which
are all incorporated by reference. Illustrative of useful optical
brighteners are 4,4'-bis-(triazinylamino)-stilbene-2,2'-disulfonic
acids, 4,4'-bis-(triazol-2-yl)stilbene-2,2'-disulfonic acids,
4,4'-dibenzofuranyl-biphenyls, 4,4'-(diphenyl)-stilbenes,
4,4'-distyryl-biphenyls, 4-phenyl-4'-benzoxazolyl-stilbenes,
stilbenyl-naphthotriazoles, 4-styryl-stilbenes,
bis-(benzoxazol-2-yl) derivatives, bis-(benzimidazol-2-yl)
derivatives, coumarins, pyrazolines, naphthalimides,
triazinyl-pyrenes, 2-styryl-benzoxazole or -naphthoxazoles,
benzimidazole-benzofurans or oxanilides.
[0036] Most commercially available optical brightening agents are
based on stilbene, coumarin and pyrazoline chemistries and these
are preferred for use in the practice of this invention. More
preferred optical brighteners for use in the practice of this
invention are optical brighteners typically used in the paper
industry based on stilbene chemistry such as 1,3,5-triazinyl
derivatives of 4,4'-diaminostilbene-2,2'-disulfonic acid and salts
thereof, which may carry additional sulfo groups, as for example at
the 2, 4 and/or 6 positions. Most preferred are the commercially
available stilbene derivatives as for example those commercially
available from Ciba Geigy under the tradename "Tinopal", from
Clariant under the tradename "Leucophor", from Lanxess under the
tradename "Blankophor", and from 3V under the tradename "Optiblanc"
such as disulfonate, tetrasulfonate and hexasulfonate stilbene
based optical brightening agents. Of these most preferred
commercial optical brightening agents, the commercially available
disulfonate and tetra sulfonate stilbene based optical brightening
agents are more preferred and the commercially available
disulfonate stilbene based optical brightening agents is most
preferred. While the present invention prefers methods and
fiber-OBA complexes using the above-mentioned OBA, the present
invention is in no way limited to such exemplified embodiments and
any OBA may be utilized.
[0037] The present invention relates in part, to a fiber:OBA
complex in which the affinity of the OBA added to the fiber
according to present invention is preferably greater than that when
the OBA is added to the fiber conventionally. When the OBA is added
to the fiber according to the method of the present invention,
there is 30 to 60% reduction in the OBA required to be added than
that of conventional methods and addition points. The reduction may
be 30, 31, 32, 33, 34, 35, 40, 45, 50, 55, 56, 57, 58, 59, and 60%
compared to that required in conventional methods and addition
points, including any and all ranges and subranges therein.
[0038] The increased affinity of the OBA to the fiber may be
measured by extraction methods using any solvent, preferably water,
at any temperature. Because the OBA has increased affinity to the
fiber overall in the present inventive pulps and paper substrates
made therefrom compared to conventional pulp, it will take a longer
period of time for the OBA to be extracted from the pulp:OBA
complex of the present invention (pulp and/or paper) at a given
time period and temperature for a given solvent.
[0039] In addition, the present invention preferably relates to a
method of increasing the penetration of OBA into the cell wall of a
fiber. Preferably, there is a greater amount of OBA that has
penetrated the cell wall of a fiber treated according to the
present invention than that of fibers treated by conventional
methods. More preferably, the amount of OBA present within the cell
wall of the fiber is increased by at least 1% than the amount of
OBA present within the cell wall of fiber that was treated in
conventional methods. However, it is more preferred that the amount
of OBA present within the cell wall of the fiber is increased by at
least 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50,
55, 60, 65, 70, 75, 80, 85, 90, 100, 200, 300, 500, and 1000% than
the amount of OBA present within the cell wall of fiber that was
treated in conventional methods, including any and all ranges and
subranges therein.
[0040] More preferably, at least about 1% of the cell wall of the
is penetrated by the OBA. However, it is more preferred that at
least 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50,
55, 60, 65, 70, 75, 80, 85 or 90% of the cell wall has been
penetrated by OBA, including any and all ranges and subranges
therein.
[0041] The amount of OBA present within the cell wall of fiber may
be measured, for example, by microscopy, more specifically
fluorescent microscopy.
[0042] While any amount of OBA may be added to the fiber so long as
it is added at any point after the last bleaching/extraction stage
and up to and prior to the Blend Chest/Machine Chest Stages, it is
preferable that from 1 to 60 lbs of OBA per ton of fiber, more
preferably not more then 30 lbs/ton, most preferably, not more than
15 lbs/ton OBA/fiber. This range includes 60, 55, 50, 45, 40, 30,
35, 30, 25, 20, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, and
1 lbs of OBA per ton of fiber (lbs/ton) including any and all
ranges and subranges therein.
[0043] In addition, the fiber may be in the solution or slurry, or
added to the solution or slurry at the same time, as the OBA.
Preferably, the fiber is in solution or slurry prior to contacting
the OBA thereto. In one embodiment of the present invention, the
fiber may have any consistency. However, it is preferably to have a
consistency that is equal to or greater than 4% solids, more
preferably, not less than about 5% solids, most preferably, not
less than about 10% solids. In addition, it is preferable that the
fibers have a consistency that is not more than about 35% solids,
preferably not more than 20% solids, more preferably not more than
about 15% solids. These ranges include 2, 3, 4, 5, 6, 7, 8, 9, 10,
11, 12, 13, 14, 15, 16, 17, 18, 19, and 20% solids as the fiber
consistency at the time the OBA is added thereto, including any and
all ranges and subranges therein.
[0044] At the time of the addition of the OBA to the fiber, the pH
may be any pH. Preferably, the pH may range from 2.5 to 8.0, more
preferably from 3.5 to 5.5. This range includes 2.5, 3.0, 3.5, 4.0,
4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, and 8.0, including any and all
ranges and subranges therein.
[0045] At the time of the addition of the OBA to the fiber, the
temperature may be any temperature. However, it is preferable that
means be applied, such as heating, so as to generate a temperature
that is from 35 to 95.degree. C., preferably from 50 to 90.degree.
C., more preferably from 60 to 80.degree. C. This range includes
35, 40, 45, 50, 55, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71,
72, 73, 74, 75, 76, 77, 78, 79, 80, 85, 90 and 95.degree. C.,
including any and all ranges and subranges therein.
[0046] The time in which the OBA is contacted with the fiber may be
for any duration of time. Preferably, the OBA and fiber may be
contacted from 30 minutes to 12 hours, more preferably from 45
minutes to 8 hours, most preferably from 1 hour to 6 hours. This
range includes 0.5, 0.75, 1, 1.25, 1.5, 1.75, 2, 2.25, 2.5, 2.75,
3, 3.25, 3.5, 3.75, 4, 4.25, 4.5, 4.75, 5, 5.25, 5.5, 5.75, 6, 6.5,
7, 7.5, 8, 8.5, 9, 9.5, 10, 11, and 12 hrs, including any and all
ranges and subranges therein.
[0047] At the time of contacting the OBA with the fiber, retention
aids may optionally be present or added therewith. Alum and/or
cationic retention aids are examples of such retention aids.
Examples of retention aids is found in U.S. Provisional Patent
Application 60/660703, filed Mar. 11, 2005, and U.S. Pat. No.
6,379,497, which are hereby incorporated, in their entirety, herein
by reference. However, any retention aid commonly used with OBAs
may be used. While the retention aid may be present in any amount,
or not at all, preferably, the amount of retention aid present is
less than that required during conventional processes and addition
points used to contact OBA with fibers. Most preferably, no
retention aids are used. If retention aids are used, it is
preferable that there is at least a 1% reduction in the amount of
retention aid present as compared to that of conventional methods
and addition points for contacting OBA with fiber. The preferred
reduction is at least 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 50,
60, 75, 100, 200, 300, 500, and 1000% reduction in the amount of
retention aid present in the present invention as compared to
conventional methods and addition points for contacting OBA with
fiber, including any and all ranges and sub-ranges therein.
[0048] While the fiber may be refined at any time, preferably, the
fiber is refined after the OBA is contacted with the fiber.
Therefore, the fiber:OBA complex of the present invention is
refined. Accordingly, any conventional refining may occur,
including but not limited the chemical refining, mechanical
refining, thermochemical refining, thermomechanical refining,
chemithermomechanical refining, etc. may occur. Therefore the pulp
produced may include TMP, CTMP, MP, BCTMP, etc.
[0049] The pulp of the present invention and method of making the
same may be incorporated into any traditional papermaking process.
The pulp and/or paper substrate may also include other conventional
additives such as, for example, starch, mineral and polymeric
fillers, sizing agents, retention aids, and strengthening polymers.
Among the fillers that may be used are organic and inorganic
pigments such as, by way of example, minerals such as calcium
carbonate, kaolin, and talc and expanded and expandable
microspheres. Other conventional additives include, but are not
restricted to, wet strength resins, internal sizes, dry strength
resins, alum, fillers, pigments and dyes. Dyes that are especially
preferably are those of the blue dye type which are capable of
increasing the CIE Whiteness of the pulp and/or paper substrate.
Preferably, pulp and paper substrate of the present invention made
according to the present invention is capable of achieving CIE
Whiteness that is much higher than conventional pulps and
substrates made by conventional methods, even at CIE Whiteness
levels that usually result in decreased ISO brightness levels.
[0050] The pulp and/or paper substrate of the present invention may
have any CIE whiteness, but preferably has a CIE whiteness of
greater than 70, more preferably greater than 100, most preferably
greater than 125 or even greater than 150. The CIE whiteness may be
in the range of from 125 to 200, preferably from 130 to 200, most
preferably from 150 to 200. The CIE whiteness range may be greater
than or equal to 70, 80, 90, 100, 110, 120, 125, 130, 135, 140,
145, 150, 155, 160, 65, 170, 175, 180, 185, 190, 195, and 200 CIE
whiteness points, including any and all ranges and subranges
therein. Examples of measuring CIE whiteness and obtaining such
whiteness in a fiber and paper made therefrom can be found, for
example, in U.S. Pat. No. 6,893,473, which is hereby incorporated,
in its entirety, herein by reference.
[0051] Preferably, the pulp and/or paper substrate of the present
invention has a CIE whiteness that is increased over conventional
pulp and/or paper substrates made by conventional methods. The
preferred increase is at least 2, 3, 4, 5, 10, 15, 20, 25, 30, 35,
40, 50, 60, 75, 100, 200, 300, 500, and 1000% increase in CIE
whiteness as compared to that of conventional pulps, paper
substrates made by conventional methods and addition points for
contacting OBA with fiber, including any and all ranges and
sub-ranges therein.
[0052] The pulp and paper substrate of the present invention may
have any ISO brightness, but preferably greater than 80, more
preferably greater than 90, most preferably greater than 95 ISO
brightness points. The ISO brightness may be preferably from 80 to
100, more preferably from 90 to 100, most preferably from 95 to 100
ISO brightness points. This range include greater than or equal to
80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, and 100 ISO
brightness points, including any and all ranges and subranges
therein. Examples of measuring ISO brightness and obtaining such
brightness in a papermaking fiber and paper made therefrom can be
found, for example, in U.S. Pat. No. 6,893,473, which is hereby
incorporated, in its entirety, herein by reference.
[0053] Preferably, the pulp and/or paper substrate of the present
invention has an ISO brightness that is increased over conventional
pulp and/or paper substrates made by conventional methods. The
preferred increase is at least 2, 3, 4, 5, 10, 15, 20, 25, 30, 35,
40, 50, 60, 75, 100, 200, 300, 500, and 1000% increase in an ISO
brightness as compared to that of conventional pulps, paper
substrates made by conventional methods and addition points for
contacting OBA with fiber, including any and all ranges and
sub-ranges therein.
[0054] The present invention is explained in more detail with the
aid of the following embodiment example which is not intended to
limit the scope of the present invention in any manner.
Comparative Example 1
[0055] Lab experiments were carried out to simulate a commercial
paper making operation, in which T-100, a Clariant's
tetrasulphonated OBA product, was added into three bleached
hardwood Kraft pulp samples. A low speed lab Warring blender was
used for mixing pulp with all chemicals. Prior to the optical
brightener ("OBA") addition, deionized water was added into the 5
gm oven dry pulp sample to reduce its consistency to 1%
consistency. Shortly after the OBA addition, 5 ml of 5% alum
solution of alum was added into the pulp mixture to complete the
attachment of all OBA onto the fiber. After one minute mixing in
the blender, the pulp mixture was dewatered to form a brightness
pad, following the standard Tappi pulp brightness testing
procedure. Three pulp samples and three dosage of T-100 were used
in these experiments. Brightness results on individual pulp
samples, before and after OBA fixation, are as follows:
TABLE-US-00001 TABLE 1 Hardwood #1 Hardwood #2 Hardwood #3
Brightness Brite Brightness Brite Brightness Brite (GE) Gain (GE)
Gain (GE) Gain 0 80.5 0 84.4 0 86.6 0 4 83.1 2.6 87.7 3.3 90.0 3.5
8 84.2 3.7 89.7 5.1 90.4 3.8 16 84.9 4.3 89.4 5.0 90.7 4.1
Comparative Example 2
[0056] Lab experiments were carried out to simulate a commercial
paper making operation in which T-100, a Clariant's
tetrasulphonated OBA product, was added into one southern hardwood
Kraft pulp sample. A low speed lab Warring blender was used for
mixing pulp with all chemicals. Prior to the OBA addition,
deionized water was added into the 5 gm oven dry pulp sample to
reduce its consistency to 1% consistency. For experiments in series
I, shortly after the OBA addition, 5 ml of 5% alum solution of alum
was added into the pulp mixture to complete the attachment of all
OBA onto the fiber. No alum was used for experiments in series II.
For both cases, after one minute mixing in the blender, the pulp
mixture was dewatered to form a brightness pad, following the
standard Tappi pulp brightness testing procedure. Three pulp
samples and three dosage of T-100 were used in these experiments.
Brightness results on individual pulp samples, before and after OBA
fixation, are as follows:
TABLE-US-00002 TABLE 2 Series I - Series II - No Alum With Alum
Brightness Brite Brightness Brite (GE) Gain (GE) Gain 0 84.0 0 84.0
0 3 87.4 3.4 6 89.0 5.0 10 89.7 5.7 20 85.8 1.8 89.1 5.1 40 86.4
2.3 86.2 2.1 60 86.7 2.7 82.2 1.8
TABLE-US-00003 TABLE 3 Series I - Series II - No Alum With Alum
Brightness Brite Brightness Brite (GE) Gain (GE) Gain 0 84.0 0 84.0
8 3 87.4 3.4 6 89.0 5.0 10 89.7 5.7 20 85.8 0.8 89.1 5.1 40 86.4
2.3 86.2 2.1 60 86.7 2.7 82.2 1.8
TABLE-US-00004 TABLE 4 Water Water T-100 Reaction Bathat 60.degree.
C. Bath at 75.degree. C. Charge Time Brightness Brite Brightness
Brite (lbs/ton) (Hours) (GE) Gain (GE) Gain 0 0 88.9 0 88.9 0 2 1
93.0 4.1 91.8 2.9 4 1 93.6 4.6 93.4 4.5 8 1 94.9 6.0 94.7 5.8 0 0
88.9 0 88.9 0 2 5 92.2 3.3 92.0 3.1 4 5 93.6 4.6 92.7 3.8 8 5 94.0
5.1 93.9 4.9
Example 1
[0057] From a commercial IP pulp mill in Southern US, samples of
fully bleached hardwood and softwood Kraft pulp at the exit of the
bleach plant were collected and used in high consistency OBA
fixation experiments. Experimental conditions, including OBA type
and pulp consistency were identical to those described in example
1. The as-received softwood pulp sample has a pH of 5.2 and the pH
for the hardwood pulp sample was 6.7. All experiments were carried
out for a duration of two hours, in 65.degree. C. temperature bath.
Prior to some of experiments on hardwood pulp, dilute hydrochloric
acid solution was also added to the as-received mill pulp to lower
its pH to 4.9 during the reaction with OBA. The following results
were obtained:
TABLE-US-00005 TABLE 5 Softwood Hardwood Hardwood T-100 at 5.2 pH
at 6.7 pH at 4.9 pH Charge Brightness Brite Brightness Brite
Brightness Brite (lbs/ton) (GE) Gain (GE) Gain (GE) Gain 0 85.5 0
85.6 0 85.6 0 2.5 89.4 3.9 87.5 1.9 90.1 4.5 5.0 89.7 4.2 88.5 2.9
91.3 5.7 10.0 91.2 5.7 89.3 3.7 15.0 91.5 6.0 90.2 4.6 92.4 6.8
Example 2
[0058] From a commercial IP pulp mill in Europe, samples of fully
bleached softwood and hardwood pulps, leaving the bleach plant were
collected and used in OBA fixation experiments. The pH of the
filtrate of both pulp samples was 3.0. Leucophor ANO, a
disulphonate OBA product produced by Clariant, was used in this
example. Fixation experiments were carried out with variable OBA
charges, at 10% consistency, for two hours in 65.degree. C.
temperature bath. Observed changes in the pulp brightness as
results of OBA fixation is as follows:
TABLE-US-00006 TABLE 6 Leucophor Hardwood Softwood Charge
Brightness Brite Brightness Brite (lbs/ton) (GE) Gain (GE) Gain 0
89.3 0 88.4 0 5 93.6 4.3 92.8 4.3 10 94.3 4.9 92.1 3.7 15 92.7 3.4
90.4 2.0 20 91.9 2.6 89.6 1.1 30 89.3 0 86.0 -2.5
Example 3
[0059] Samples of pulps and OBA of example 3 were used in this
example. However, before mixing with OBA, dilute solution of NaOH
as used to raise the pH of the pulp samples, from 3.0 to 5.7 for
the case of hardwood and to 7.0 for the case of softwood. All other
conditions were identical to those used in example 4. Observed
changes in the pulp brightness as results of pH adjustment and OBA
fixation is as follows:
TABLE-US-00007 TABLE 7 Leucophor Hardwood Softwood Charge
Brightness Brite Brightness Brite (lbs/ton) (GE) Gain (GE) Gain 0
89.0 0 87.9 0 4 93.4 4.4 92.5 4.6 8 94.9 5.8 93.8 5.9 12 95.1 6.3
94.0 6.1 20 95.5 6.5 94.8 6.8 30 89.3 6.6 95.1 7.2
Example 4
[0060] Experiments were carried out to fix T-100 on to commercially
produced fully bleached softwood and hardwood Kraft pulp samples
from a Northern US mill. The softwood pulp has a freeness of 690
csf, brightness of 90 GE and pH of 4.0. The hardwood sample has a
freeness of 570 csf, brightness of 89.2 and pH of 4.0. Variable
dosages of T-100 were mixed with pulps at 10% consistency and were
kept in separate and sealed plastic bags. Bags were placed in
70.degree. C. water bath for 2 hours. Change in the brightness of
individual pulp samples as a result of OBA fixation is as
follows:
TABLE-US-00008 TABLE 8 T-100 Softwood Hardwood Charge Brightness
Brite Brightness Brite (lbs/ton) (GE) Gain (GE) Gain 0 90.0 0 89.2
0 2 94.4 4.4 92.0 2.8 4 95.2 5.2 92.7 3.5 6 95.8 5.8 93.3 4.1 8
96.3 6.3 93.8 4.6 10 96.6 6.6 94.2 5.0 12 97.1 7.1 94.3 5.1
Example 6
[0061] The original softwood and hardwood pulp samples of example
5, together with samples which were fixed with 12 lbs/bdt of T-100,
were subjected to high shear mechanical action inside a lab PFI
refiner. The extent of pulp refining was controlled so that the
freeness of the softwood pulp is reduced from 690 CSF before
refining to 450 CSF after refining. For the hardwood pulp, the
freeness drop was from 570 CSF to 330 CSF. Brightness changes, as a
result of PFI refining, on original pulp samples and samples
containing OBA are as follows:
TABLE-US-00009 TABLE 9 Softwood Hardwood Before After Before After
fixation fixation Gain fixation fixation Gain Before 90.0 96.6 6.6
89.2 94.2 5.0 refining After 88.4 94.7 6.3 88.4 94.0 5.6 refining
Loss 1.6 1.9 0.8 0.2
[0062] Brightness loss as a result of pulp refining operation is
well recognized in papermaking. Under refining condition used in
example 6, it was 1.6 points for the original softwood and 0.8
points for the original hardwood. Brightness losses were very
similar for the case where pulps were fixed with OBA, suggesting
that the created bonding between OBA and fiber was very strong and
was not affected by the mechanical shear action of the refiner. The
net brightness gain, obtained from OBA fixation, remained
essentially unchanged and were not affected by the pulp refining
process.
Example 6
Hand Sheet Study
SUMMARY
[0063] The handsheet study confirmed that adding Clariant Leucophor
ANO optical brightening agent (OBA) under high consistency
treatment method gave better brightness than when the OBA was added
at low consistency.
[0064] For a fixed dose, the new addition point resulted in a
brightness increase of about 1.9 units of ISO brightness.
[0065] Based on this study, to reach the same ISO brightness,
changing to the new addition method would allow the OBA dosage to
be decreased by 3.5 pounds/ton.
[0066] These estimates are based on data at OBA dose levels between
3.3 and 10 pounds/ton.
[0067] The designed experiment showed that two of the factors, OBA
dose (nominally 3.3 and 10 pounds/ton) and OBA addition method (new
method vs addition to low consistency pulp) were statistically
significant in determining brightness.
Experimental
[0068] Pulp
[0069] Pulp used for this study was unrefined hardwood and softwood
taken from the washer of the last bleaching stage.
[0070] 1. OBA Fixation
[0071] The hardwood and softwood pulps separately with two levels
of OBA, 3.3 and 10 pounds/ton of OBA. The OBA used was Leucophor
ANO (Clariant), which is a di-sulfonated OBA. The conditions were
10% consistency, mixed for 2 hours at 70.degree. C.
[0072] 2. Refining
[0073] Prior to refining, the pulps were combined into a 70:30
HWD:SWD ratio. Refining was performed in the LR1, a laboratory disk
refiner. Two energies were used, 35 kW/T and 45 kW/T. The freeness
of the resulting pulps were .about.580 and .about.320 csf,
respectively.
[0074] 3. Sheet Making
[0075] Sheets were made on the dynamic sheet former with the
following procedure: The pulp was diluted to 1% consistency and
mixed vigorously. SMI's Albacar LO PCC was added first and allowed
to mix for 1 minute. Then a predetermined and accurate amount of
OBA was added and mixed for 15 minutes. The sheet was then formed.
After forming, the sheets were pressed to .about.45% solids and
dried at 230.degree. F. on the drum drier. Special precautions were
made so that the sheets with `fixed` OBA had similar amounts of OBA
as the standard OBA addition sheets. In addition to the samples
pretreated with OBA and the samples prepared as describe here,
where the PCC was added before the OBA, several controls were also
made where the order of addition of the PCC and OBA was reversed
(OBA first).
[0076] 4. Testing
[0077] The handsheets were tested for various optical properties
using the DataColor Elrepho Spectrophotometer.
[0078] 5. Experimental Design
[0079] The design for this experiment included four main
factors:
[0080] I) Stock consistency at which the OBA was added (10% vs.
1%)
[0081] II) Refining (35 kW/T vs. 45 kW/T)
[0082] III) Filler Level (10% vs. 20%)
[0083] IV) OBA dose (3.3 lb/T vs. 10 lb/T)
Results & Conclusions:
[0084] Comparison of Handsheet Brightness for New and Traditional
Fixation methods:
[0085] Adding Clariant Leucophor ANO optical brightening agent
(OBA) under the new, high consistency treatment method gave better
brightness than when added at low consistency to handsheets. The
results are set forth in the following FIGS. 1 to FIGS. 1-4 shows
all the brightness data from the study graphed against OBA dose.
There are several different classes of samples listed, separated by
the fixation method (high and low consistency) and filler level (10
and 20 #/ton).
Raman Spectroscopy Study of Pulp with OBA:
[0086] Raman spectroscopy was used to study pulp with OBA added
using the conventional as well as new processes. FIG. 5 compares
the spectrum of OBA (Leucophur ANO) with spectra of pulp with and
without OBA added. The most intensive peak at the spectrum of the
OBA at approximately 1600 cm.sup.-1 is visible in the spectrum of
pulp with the OBA added. FIG. 6 shows spectra of pulp (expanded
region from 300 to 1700 cm.sup.-1) with different levels of OBA
added in the process. The intensity of the peak at 1600 cm.sup.-1
increased with increased level of the OBA. When spectra of the pulp
with OBA added in the conventional and the new process were
compared, there were no changes in the shape of the peaks and no
addition peaks were observed (see FIG. 7). In order to determine
the relative amount of OBA retained on the fibers, the ratio of the
intensity of the maximum at 1600 cm.sup.-1 to the intensity of the
peak at 900 cm.sup.-1 (cellulose peak) was calculated for pulps
with different OBA levels added in the process. The results are
presented in the table and the FIG. 8.
TABLE-US-00010 TABLE 10 Process OBA added, lb/ton Peak Ht ratio
Conv 0 0.026 10 0.469 15 0.637 20 0.711 New HW 0 0.034 3.3 0.238 10
0.648 New SW 0 0.071 3.3 0.371 10 0.685
[0087] The results of Raman measurements indicate that the amount
of OBA in the pulp produced in the new process at 10 lb/ton in
comparable to the amount of OBA in the pulp obtained in the
conventional process at 15-20 lb/ton loading
Inductively Coupled Plasma Spectroscopy (ICP) Study of OBA in
Pulp:
[0088] Samples of softwood and hardwood pulp with OBA added during
the conventional and new processes were hot plate digested with
hydrogen peroxide and nitric acid. A sample of OBA used in the
process was dried and digested under the same conditions. The
digested samples were analyzed for sulfur content by ICP. The
results are presented in the table below. Untreated pulp was also
analyzed under the same conditions and determined sulfur
concentrations were subtracted from the concentrations in the
treated pulp in order to establish the amount of OBA present in the
pulp, which is reported on the dry weight of the OBA.
TABLE-US-00011 OBA S from OBA on fiber, added, Sulfur from OBA on
ppm (based on Process lb/ton ICP, ppm fiber, ppm S results) Conv 0
150 10 190 40 697 20 250 100 1744 New HW 0 140 10 250 110 1918 New
SW 0 66 10 150 84 1465 OBA (oven dry) 57600; 57100
[0089] The sulfur concentrations in the pulp indicate that the
amount of OBA present in the pulp treated in the new process at 10
lb/ton OBA is comparable to the amount of the pulp from the
conventional process at 20 lb/ton loading.
Extraction Studies:
[0090] Approximately 1 gram of pulp was cut into small pieces and
soaked in approximately 150 ml. of water for 6 hours at 60 degrees
C.
[0091] The water extracts were filtered through a 0.45 .mu.m
filter, reduced to approximately 2 ml volume in a LABCONCO Rapidvap
Nitrogen Evaporation System using air as the purge gas. The
Evaporator was run at 24% vortex speed at a temperature of
30.degree. C. After evaporation to approximately 2 ml. the sample
was brought to 5 ml. in a volumetric flask.
[0092] A portion of this water 5 ml. extract was analyzed by high
performance liquid chromatography (HPLC).
[0093] A portion of the 5 ml. water extract was diluted 1:10 for
the UVNIS analysis.
The HPLC Instrumental Conditions are Below:
[0094] Instrument description: Waters Alliance 2695 separation
module with a Waters model 996 Photodiode Array Detector (PDA)
[0095] Mobile phase: 50% methanol 50% PIC-A buffer solution at 0.7
ml minute. PIC-A is sold by the Waters Corporation and is a reverse
phase ion pairing buffer solution composed of 0.005 m tetrabutyl
ammonium phosphate buffered to a pH of 7.5.
[0096] Column: Phenomenex Luna 5 .mu. C-8 (2) 250 mm.times.4.6 mm,
operated at 35.degree. C.
[0097] Detector: Waters 400 photo diode array detector (PDA) over
the range of 200-800 nm. The peak at 254 nm was selected for the
analysis.
[0098] Run Time: 60 minutes
[0099] Injection Volume: 10 .mu.l
The UV/VIS Instrumental Conditions are Below:
[0100] Instrument description: Shimadzu model UV-160 operated in
the photometric mode.
[0101] Wavelength used for analysis: 350 nm.
[0102] The results are set forth in FIGS. 9-11
[0103] Numerous modifications and variations on the present
invention are possible in light of the above teachings. It is,
therefore, to be understood that within the scope of the
accompanying claims, the invention may be practiced otherwise than
as specifically described herein.
[0104] As used throughout, ranges are used as a short hand for
describing each and every value that is within the range, including
all subranges therein.
[0105] All of the references, as well as their cited references,
cited herein are hereby incorporated by reference with respect to
relative portions related to the subject matter of the present
invention and all of its embodiments.
* * * * *