U.S. patent application number 13/476211 was filed with the patent office on 2013-04-18 for modified kraft fibers.
This patent application is currently assigned to INTERNATIONAL PAPER COMPANY. The applicant listed for this patent is GOPAL GOYAL, ALEXANDER A. KOUKOULAS, ZHENG TAN. Invention is credited to GOPAL GOYAL, ALEXANDER A. KOUKOULAS, ZHENG TAN.
Application Number | 20130092336 13/476211 |
Document ID | / |
Family ID | 36956421 |
Filed Date | 2013-04-18 |
United States Patent
Application |
20130092336 |
Kind Code |
A1 |
TAN; ZHENG ; et al. |
April 18, 2013 |
MODIFIED KRAFT FIBERS
Abstract
A method of producing a modified pulp comprising treating wood
chips in an extraction process to remove hemicellose to form
treated wood chips; and subjecting said treated wood chips to
chemical or semichemical pulping to form a modified Kraft pulp
wherein the amount of hemicellulose contained in the modified Kraft
pulp is from about 5 to about 10% by dry weight of the modified
pulp.
Inventors: |
TAN; ZHENG; (Atlanta,
GA) ; GOYAL; GOPAL; (Mason, OH) ; KOUKOULAS;
ALEXANDER A.; (Walpole, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TAN; ZHENG
GOYAL; GOPAL
KOUKOULAS; ALEXANDER A. |
Atlanta
Mason
Walpole |
GA
OH
MA |
US
US
US |
|
|
Assignee: |
INTERNATIONAL PAPER COMPANY
Memphis
TN
|
Family ID: |
36956421 |
Appl. No.: |
13/476211 |
Filed: |
May 21, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12398288 |
Mar 5, 2009 |
8182650 |
|
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13476211 |
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|
11582647 |
Oct 18, 2006 |
7520958 |
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12398288 |
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11439659 |
May 24, 2006 |
8328983 |
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11582647 |
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60684018 |
May 24, 2005 |
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Current U.S.
Class: |
162/60 ; 162/1;
162/68; 162/78 |
Current CPC
Class: |
D21C 11/0007 20130101;
D21H 21/32 20130101; D21H 17/64 20130101; D21C 3/00 20130101; D21C
9/10 20130101; D21C 3/02 20130101; D21H 11/20 20130101; A61F 13/531
20130101; D21C 1/00 20130101; D21C 1/06 20130101; D21H 11/04
20130101; D21H 21/22 20130101; A61L 15/28 20130101 |
Class at
Publication: |
162/60 ; 162/68;
162/1; 162/78 |
International
Class: |
D21C 3/00 20060101
D21C003/00 |
Claims
1. A method of producing a modified bleached Kraft pulp comprising:
treating wood chips with an acidic solution in an extraction
process with steam, a liquid comprising water or a combination
thereof to remove 5% to 20% hemicellulose to form treated wood
chips having a pH equal or less than 5.0; subjecting the treated
wood chips to chemical or semichemical pulping to form a modified
Kraft pulp wherein the amount of hemicellulose contained in the
modified Kraft pulp is from about 3 to about 15% by oven dried
weight of the modified pulp; directly after the subjecting the
treated wood chips step, bleaching the modified Kraft pulp to form
a modified bleached Kraft pulp.
2. The method of claim 1 further comprising a washing step.
3. The method of claim 1 further comprising a refining step.
4. The method of claim 1 wherein the wood chips are extracted at
temperatures ranging from 140 .degree. C. to 160 .degree. C.
5. The method of claim 1 wherein the wood chips are treated at
treatment time ranging from 30 minutes to 240 minutes.
6. The method of claim 1 wherein the removal of 5% to 20%
hemicelluloses at the extracted temperature of 140 .degree. C. will
take from about 60 minutes to 150 minutes.
7. The method of claim 1 wherein the modified Kraft pulp includes
enhanced properties define by higher bulk, higher brightness,
better drainage and dewatering or drying or a combination.
8. The method of claim 1 wherein the step of treating wood chips is
producing a modified Kraft pulp having at least about 1% by weight
less hemicelluloses the same pulp when un-modified.
9. The method of claim 1 wherein the step of treating wood chips is
producing a modified Kraft pulp having from about 2% to about 8%
less hemicelluloses than the same pulp when un-modified.
10. The method of claim 1 wherein the acidic pH is from about 2 to
about 4.
11. The method of claim 1 wherein the modified pulp exhibits water
retention of from about 0.2 g/g to about 0.5 g/g less than that of
the same or substantially the same unmodified pulp.
12. The method of claim 1 wherein the modified pulp exhibits
freeness of from about 25 to about 200 CSF units greater than that
of the same or substantially same un-modified pulp.
13. The method of claim 1 wherein prior to or during the treating
step, a peroxide is added in the treatment.
14. The method of claim 13 wherein additional peroxide is added to
an extracted hemicelluloses portion after the treating step.
15. The method of claim 13 wherein the peroxide is at least one
member selected from group consisting of hydrogen peroxide,
perborate, per carbonate, persulfate, peroxymonosulfuric (or Oxone)
or peracetic acid.
16. A method of producing a modified bleached Kraft pulp
comprising: treating wood chips with an acidic solution in an
extraction process with steam, a liquid comprising water or a
combination thereof to remove 5% to 20% hemicellulose to form
treated wood chips having a pH equal or less than 5.0; subjecting
the treated wood chips to chemical or semichemical pulping to form
a modified Kraft pulp wherein the amount of hemicellulose contained
in the modified Kraft pulp is from about 3 to about 15% by oven
dried weight of the modified pulp; directly after the subjecting
step, washing the modified pulp to remove the Kraft liquor
therefrom; and directly after the washing step, bleaching the
modified Kraft pulp to form a modified bleached Kraft pulp.
17. The method of claim 14 further comprising a refining step after
the bleaching step.
18. The method of claim 14 wherein the wood chips are extracted at
temperature ranging from 140 .degree. C. to 160 .degree. C.
19. The method of claim 1 wherein the removal of 5% to 20%
hemicelluloses at the extracted temperature of 140 .degree. C. will
take from about 60 minutes to 150 minutes.
Description
RELATED PATENT APPLICATIONS
[0001] This is a continuation application which claims priority
from a continuation-in-part of U.S. patent application Ser. No.
11/582,647 filed on Oct. 18, 2006 which in turn claims priority of
U.S. patent application Ser. No. 11/439,659 filed May 24, 2006
which in turn claims the benefit of U.S. Provisional Patent
Application Ser. No. 60/684,018 filed on May 24, 2005.
FIELD OF THE INVENTION
[0002] This invention relates to an improved method for
manufacturing pulp, pulp manufactured in accordance with this
process and paper and paperboard products manufactured from the
bleached pulp of this invention. More particularly, this invention
relates to improvement in processes for the manufacture of pulps
having reduced hemicellulose content which exhibit one or more
beneficial properties.
BACKGROUND OF THE INVENTION
[0003] Processes for digesting wood chips to form pulps and
processes of bleaching pulps and using bleached pulps in the
manufacture of paper, paperboard and absorbent products are known.
See for example U.S. Pat. Nos. 6,063,982; 5,766,159; 5,902,454 and
6,464,832
SUMMARY OF THE INVENTION
[0004] One aspect of this invention relates to a method of
producing a modified Kraft pulp for use in paper, paperboard and
pulp products comprising:
[0005] treating wood chips with steam, a liquid comprising water or
a combination thereof in an extraction process to remove
hemicellose to form treated wood chips; and
[0006] subjecting said treated wood chips to kraft pulping to form
a modified Kraft pulp wherein the amount of hemi cellulose
contained in the modified Kraft pulp is from about 5 to about 10%
by dry weight of the modified pulp.
[0007] Another aspect of this invention relates to a method of
producing a modified Kraft pulp comprising treating Kraft pulp,
preferably bleached Kraft hardwood pulp, with steam, a liquid
comprising water or a combination thereof to extract hemicellulose
from the pulp to form a modified Kraft pulp wherein the amount of
hemicellulose in the modified Kraft pulp is from about 5 to about
10% by dry weight of the modified pulp.
[0008] Another aspect of this invention relates to modified Kraft
pulp formed by the processes of this invention. The modified Kraft
pulp of this invention exhibits one or more advantages. These
advantages include improved drainage which enhances the speed of
paper making processes which use the pulp of this invention as
compared to unmodified pulps. Such advantages also include higher
freeness, enhanced bleachability, de-watering, drying or a
combination of tow or more of the foregoing as compared to the
un-modified Kraft pulp.
[0009] Yet another aspect of this invention relates to paper,
paperboard, pulp and absorbent products prepared from the modified
pulp of this invention.
[0010] Still another aspect of this invention relates to a personal
hygiene article for absorbing fluids, the article comprising:
[0011] at least one fluid permeable top sheet layer and at least
one substantially fluid impermeable back sheet layer; and
[0012] an absorbent sub layer material interposed between the top
sheet layer and the back sheet layer, the sub layer material
comprising modified pulp of this invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] In the drawings:
[0014] FIG. 1 as a plot of % hemicellulose removed at various
temperatures as a function of extraction time.
[0015] FIG. 2 is a plot of water retention versus freeness for the
modified pulp of this invention and the same unmodified pulp.
[0016] FIG. 3 is a plot of bulk versus Sheffield Smoothness for the
modified pulp of this invention and the same unmodified pulp.
DETAIL DESCRIPTION OF THE INVENTION
[0017] In the process of this invention wood chips or Kraft pulp
are extracted with steam, a liquid comprising water or a
combination thereof to reduce and to remove hemicellose to form
treated wood chips. The type of wood chips or pulp used in the
process of this invention is not critical and wood chips or pulp
derived from all types of woods can be used. For example, useful
wood chips or pulp include those derived from hardwood trees,
softwood trees, or a combination of hardwood and softwood trees.
The term "hardwood trees" as used herein refers to deciduous trees
(angiosperms) such as aspen and maple, and the term "softwood
trees" as used herein refers to coniferous trees (gymnosperms) such
as southern pine. In the preferred embodiments of the invention
wood chips or pulp derived from hardwoods are used.
[0018] The wood chips or pulp are extracted with steam, a liquid
comprising water or a combination thereof. In the preferred
embodiments of the invention the chips or pulp are extracted with a
liquid comprising water. The liquid can consist of water alone or
may include one or more additional materials. Such additional
materials may vary widely and include organic acids such as acetic
acid, propanoic acid, sulfamic acid, lactic acid, citric acid and
the like and inorganic acids such as sulfuric acid, sulfurous
acids, phosphoric acid, hydrochloric acid, nitric acid, boric acid
and the like. Useful additional materials also include inorganic
bases such as sodium hydroxide, potassium hydroxide and ammonium
hydroxide. Organic and inorganic acids are preferred for use in the
practice of this invention and inorganic acids are more
preferred.
[0019] In the preferred embodiments of this invention the wood
chips or pulp are extracted with an aqueous acidic composition to
an end pH of less than 7. Use of the aqueous acidic solution allows
the extraction to be carried out at lower temperatures as for
example at room or ambient temperatures with shorter extraction
times. The end pH is preferably equal to or less than about 6, more
preferably equal to or less than about 5 and most preferably from
about 2 to about 4.
[0020] Prior to or during the extraction, the wood chips or Kraft
pulp may be treated with hydrogen peroxide (such as hydrogen
peroxide, perborate, per carbonate, persulfate, peroxymonosulfuric
(or Oxone) or peracetic acid)at an acidic pH (preferably with
addition of transition metal catalysts, such as iron, copper,
manganese, or cobalt salts). The extracted hemicelluloses (or
hydrolyzate) will have a lower molecular weight, and thus a lower
solution viscosity at given solids content which enhances the
fluidity or ease of pumping extracted hemicelluloses (or
hydrolyzate). The catalyzed peroxide treatment may also be applied
to the extracted hemicelluloses (hydrolyzate) portion only,
achieving the same purpose as above in reducing solution viscosity
at given solids content. The outcome of the above processes not
only have the advantage of enabling handling higher solids of the
extracted hemicelluloses with practical and economical benefits, it
also oxidize the carbohydrate structure of hemicelluloses
(especially in the case of xylose moieties) which enhances their
susceptibility to biological fermentations such as in the
biorefinery of the extracted hemicelluloses for ethanol production
or the production of other chemicals.
[0021] Treatment temperatures may vary widely and any temperature
sufficient to form the desired extracted wood chips or Kraft pulp
can be used. The treatment temperature is usually at least about
20.degree. C. although lower temperatures may be used if effective
to provide the desired treated wood chips or Kraft pulp. The
treatment temperature is preferably from about 20.degree. C. to
about 200.degree. C., more preferably from about 50.degree. C. to
about 190.degree. C. and most preferably from about 100.degree. C.
to about 180.degree. C., with a temperature of from about
110.degree. C. to about 170.degree. C. being the temperature in the
embodiments of choice.
[0022] Treatment times may vary widely and any time sufficient to
form the desired treated wood chips or Kraft pulp can be used. The
treatment time is usually at least about 5 minutes although longer
treatment times may be used if effective to provide the desired
ligno cellulosic material. The treatment time is preferably from
about 5 minutes to about 20 hours, more preferably 15 minutes to
about 10 hours and most preferably from about 30 minutes to about 4
hours.
[0023] Hemicellulose removed from the extracted wood chips or Kraft
pulp can vary widely provided that the amount remaining in the
extracted Kraft pulp and modified pulp after Kraft pulping of the
extracted wood chips in the second step of the process of this
invention is from about 5% to about 10% by dry weight of the
modified pulp. For example, the amount of hemicellulose removed in
the first step may vary from about 5 by weight or lower to about
20% by weight or higher based on the total amount of hemicellulose
in the wood chips or Kraft pulp. In the preferred embodiments of
the invention, the amount of hemicellulose removed in the first
step may vary from about 10% by weight to about 15% by weight based
on the total amount of hemicellulose in the wood chips or Kraft
pulp.
[0024] The extracted hemicelluloses can be burned in the hog boiler
or other types of biomass boilers, such as by spraying onto the
biomass fuel feedstock (barks, pin chips, sawdust, coal, etc.), and
therefore maintaining the energy balance in the mill.
Alternatively, the extracted hemicelluloses can be used as
feedstock for fermentation to produce fuel chemicals. The extracted
hemicelluloses can be oxidized, or derivatized with ether
functional groups or cationic charges. The hemicelluloses thus
treated can then be used as papermaking additives, such as added in
the paper-machine wet end, or mixed with starch for the use in
size-press, or coating. In subsequent Kraft pulping of the
extracted wood chips, the extracted hemicelluloses can be diverted
away from the pulping process stream, thus reducing the Kraft black
liquor recovery boiler heat load (usually being the production
capacity bottle-neck).
[0025] When wood chips are extracted the treated or extracted wood
chips are subject to a chemical or semi chemical pulping process.
Such processes are well known to those of skill in the art and will
not be described in any great detail. See for example "Handbook for
Pulp & Paper Technologies", 2.sup.nd Edition, G. A. Smook,
Angus Wilde Publications (1992) and references cited therein, all
of which are herein incorporated by reference. Illustrative of
useful chemical and semi-chemical pulping processes are carbonate
pulping processes, green liquor pulping processes, Kraft pulping
processes or Sulfite pulping processes. Kraft pulping is preferred
for use in the practice of this invention.
[0026] The amount of hemicellulose contained in the modified Kraft
pulp is from about 3 to about 15% by dry weight of the modified
pulp. The amount of hemicellulose contained in the modified Kraft
pulp is preferably from about 4 to about 13% by dry weight of the
modified pulp. The amount of hemicellulose contained in the
modified Kraft pulp is more preferably from about 5 to about 10% by
dry weight of the modified pulp and is most preferably from about 6
to about 8% by dry weight of the modified pulp. This modified Kraft
pulp (either hardwood or softwood) displays significantly higher
brightness and paper bulk with improved drainage and drying
potential, as compared to the unmodified pulp.
[0027] In a preferred embodiment of this invention, the modified
Kraft pulp of this invention contains at least about 1% by weight
less hemicelluloses of the same pulp when un-modified. In these
preferred embodiments of the invention, the modified Kraft pulp
contains from about 1% to about 20% by weight less hemicelluloses
than the same pulp when un-modified. In these preferred embodiments
of the invention, the modified Kraft pulp contains from about 1% to
about 20% by weight less hemicelluloses than the same pulp when
un-modified. In these preferred embodiments of the invention, the
modified Kraft pulp preferably contains from about 1% to about 16%
by weight less hemicelluloses than the same pulp when un-modified.
In these preferred embodiments of the invention, the modified Kraft
pulp more preferably contains from about 2% to about 16% by weight
less hemicelluloses than the same pulp when un-modified. In these
preferred embodiments of the invention, the modified Kraft pulp
most preferably contains from about 2% to about 8% by weight less
hemicelluloses than the same pulp when un-modified
[0028] In the preferred embodiments of the invention, the modified
pulp of this invention exhibits higher freeness as measured by the
procedure of T227 om-99. The increase in freeness is preferably at
least about 20 CSF units greater than that of the un-modified pulp.
In the more preferred embodiments of the invention the increase in
freeness is at least about 50 CSF units greater than that of the
un-modified pulp and in the most preferred embodiments of the
invention the increase in from about 50 to about 200 CSF units
greater than that of the un-modified pulp.
[0029] In the preferred embodiments of the invention the modified
pulp of this invention exhibits reduced water retention values
(WRV) (as measured by the procedure described in the Examples
below) as compared to the unmodified pulp. In these preferred
embodiments of the invention, the reduction in water retention is
preferably equal to or greater than about 0.1 g/g. In the more
preferred embodiments of the invention, the reduction in water
retention is preferably equal to or greater than about 0.15 g/g.
and in the most preferred embodiments of the invention, the
reduction in water retention is equal to or greater than about 0.2
g/g. In the embodiments of choice, the reduction in water retention
is from about 0.2 g/g to about 0.5g/g.
[0030] The modified pulp of this invention can be subjected to one
or more post pulping treatments as for example beaching with
conventional bleaching agents such as chlorine dioxide, elemental
chlorine, ozone and peroxide using procedures and apparatuses
described in "Handbook For Pulp & Paper Technologies", 2.sup.nd
Edition, G. A. Smook, Angus Wilde Publications (1992) and
references cited therein. The pulp can also be subjected to
extraction as for example oxygen delignification or extraction with
base preferably in the presence of peroxide. In the preferred
embodiments of the invention, the modified pulp of this invention
exhibits improved bleachability. A benefit of improved
bleachability is that the amount of bleaching chemical dose (kappa
factor) used can be reduced while reaching the same brightness as
the un-modified bleached pulp, thus generating chemical cost
savings. Another benefit of improved bleachability is the same
amount of bleaching chemical as the un-modified pulp case can be
used, especially in early bleaching stages, thus reducing the
number of bleaching stages (savings in capital and energy) required
to reach the same brightness. Yet another benefit of improved
bleachability is that very high brightness pulp can be produced,
which cannot be practically achieved with un-modified pulp. For
instance, it is well-known fact that Kraft pulp cannot be bleached
practically beyond an 89 ISO brightness with a reasonable amount of
bleaching agent such as chlorine dioxide. With this modified Kraft
pulp, however, high brightness levels equal to or greater than
about 90 ISO brightness and preferably from about 90 to about 95
ISO brightness can be achieved in the preferred embodiments of the
invention with practical amounts of bleaching chemicals.
[0031] In other preferred embodiment of this invention the modified
pulp has less anionic charge or less hydrated fiber surface,
showing better affinity for paper chemicals such as sizing, dyes
and optical brighteners. In another preferred embodiment of this
invention the modified Kraft pulp, containing less hemicellulose,
has less moisture sensitivity and shows improved performance in
hydroexpansivity.
[0032] The modified pulp of this invention can be used in the
manufacture of pulp products as for example fluff pulp. The
modified pulp of this invention can be used in the manufacture of
paper and packaging products such as printing, writing, publication
and cover papers and paperboard products. Illustrative of these
products and processes for their manufacture are those described in
U.S. Pat. Nos. 5,902,454 and 6,464,832.
[0033] In paper or paperboard making process, the modified pulp of
this invention can be used with no or little refining, and the
modified pulp can be mixed with fully-refined unmodified pulps,
especially unmodified softwood pulps such as Southern Pine pulp,
prior to use in paper or paperboard manufacture in various amounts
depending on the type of paper. For example, mixtures of the
modified pulp of this invention and unmodified softwood pulp can,
for example, contain from about 10 to about 90% by weight of
modified hardwood pulp of this invention, preferably from about 15
to about 85% by weight of modified hardwood pulp of this invention
and more preferably from about 20 to about 80% by weight of
modified hardwood pulp of this invention, based on the total weight
of the pulp mixture.
[0034] The modified pulp of this invention or pulp mixtures
comprising the modified pulp of this invention is formulated into
an aqueous paper making stock furnish which also comprises one of
more additives which impart or enhance specific sheet properties or
which control other process parameters. Illustrative of such
additives is alum which is used to control pH, fix additives onto
pulp fibers and improve retention of the pulp fibers on the paper
making machine. Other aluminum based chemicals which may be added
to the furnish are sodium aluminate, poly aluminum silicate sulfate
and poly aluminum chloride. Other wet end chemicals which may be
included in the paper making stock furnish for conventional
purposes are acid and bases, sizing agents, dry-strength resins,
wet strength resins, fillers, coloring materials, retention aids,
fiber flocculants, defoamers, drainage aids, optical brighteners,
pitch control chemicals, slimicides, biocides, specialty chemicals
such as corrosion inhibitors, flame proofing and anti-tarnish
chemicals, and the like. Methods and procedures for formulating
mechanical bleached pulp, aluminum based wet end chemicals and
other optional wet end chemicals are well known in the art and will
not be described in any great detail. See for example, "Handbook
For Pulp & Paper Technologies", 2.sup.nd Edition, G. A. Smook,
Angus Wilde Publications (1992) and references cited therein, all
of which are herein incorporated by reference.
[0035] The aqueous paper making stock furnish comprising the
bleached mechanical pulp and the aluminum based compounds is
deposited onto the forming wire of a conventional paper making
machine to form a wet deposited web of paper or paperboard and the
wet deposited web of paper or paperboard is dried to form a dried
web of paper or paperboard. Paper making machines and the use of
same to make paper are well known in the art and will not be
described in any great detail. See for example, Handbook For Pulp
& Paper Technologies, supra. By way of example, the aqueous
paper making stock furnish containing pulp, aluminum based and
other optional additives and usually having a consistency of from
about 0.3% to about 1% is deposited from the head box of a suitable
paper making machine as for example a twin or single wire
Fourdrinier machine. The deposited paper making stock furnish is
dewatered by vacuum in the forming section. The dewatered furnish
is conveyed from the forming section to the press section on
specially-constructed felts through a series of roll press nips
which removes water and consolidates the wet web of paper and
thereafter to the dryer section where the wet web of paper is dried
to form the dried web of paper of this invention. After drying, the
dried web of paper may be optionally subjected to several dry end
operations such as and various surface treatments such as coating,
and sizing and calendering.
[0036] In the preferred embodiments of this invention, modified
pulp forms paper products which exhibit a bulk which is greater
than that exhibited by the same or substantially the same pulp when
unmodified. Bulk is equal to caliper divided by the basis weight.
Basis weight can be determined by the procedure of T410 om-02 and
caliper can be determined by the procedure of T411 om-05. In these
preferred embodiments of the invention modified pulp forms paper
products which exhibit a bulk which is at least about 2% greater
than that exhibited by the same or substantially the same pulp when
unmodified. In these preferred embodiments of the invention
modified pulp forms paper products which exhibit a bulk which is
preferably at least about 5% greater than that exhibited by the
same or substantially the same pulp when unmodified. In these
preferred embodiments of the invention modified pulp forms paper
products which exhibit a bulk which is more preferably from about
5% to about 40% greater than that exhibited by the same or
substantially the same pulp when unmodified. In these preferred
embodiments of the invention modified pulp forms paper products
which exhibit a bulk which is most preferably from about 5% to
about 30% greater than that exhibited by the same or substantially
the same pulp when unmodified.
[0037] The paper manufactured in accordance with this invention can
be used for conventional purposes. For example, the paper is useful
as printing paper, publication paper, newsprint and the like.
[0038] For example the modified pulp of this invention can be used
prepared absorbent articles as for example diapers, tissues,
towels, personal hygiene products using conventional processes.
Such products and their methods of manufacture are known to those
of skill in the art and will not be described in detail. See for
example, U.S. Pat. Nos. 6,063,982 and 5,766,159 and references
described therein. The modified pulp of this invention can be used
to make saturating kraft paper. Saturating kraft paper is a paper
sheet made from unbleached kraft pulp (mixture of mostly hardwood
and some softwood such as southern pine) that is used as substrate
for impregnation and curing with resin polymers. Saturating kraft
paper is used as home and office building materials, such as
kitchen counter tops.
[0039] The present invention will be described with references to
the following examples. The examples are intended to be
illustrative and the invention is not limited to the materials,
conditions or process parameters set forth in the examples.
EXAMPLE 1
[0040] Northern hardwood chips (predominantly maple), was extracted
with water at 160.degree. C. Process conditions and % mass removal
are set forth in the following Table I and FIG. 1.
TABLE-US-00001 TABLE I Extraction pH of Time Extraction Extracted
Exp. No. (min.) Temperature Hemicellulose % mass removal 1 30
140.degree. C. 5.16 1.7 2 60 140.degree. C. 4.95 2.1 3 90
140.degree. C. 5.15 3.2 4 120 140.degree. C. 4.98 4.4 5 150
140.degree. C. 3.87 5.8 6 30 150.degree. C. 4.46 2.0 7 60
150.degree. C. 4.07 4.1 8 90 150.degree. C. 4.15 9.4 9 120
150.degree. C. 3.95 9.2 10 150 150.degree. C. 3.55 12.5 11 30
160.degree. C. 3.90 6.6 12 60 160.degree. C. 3.60 11.3 13 90
160.degree. C. 3.55 15.8 14 120 160.degree. C. 3.49 15.2 15 150
160.degree. C. 3.38 19.5
The extracted chips were then cooked by Kraft pulping to Kappa
number 25. As control, the un-extracted chips were also Kraft
cooked to reach a target Kappa number of 25. Both the treated pulps
and the control pulps were bleached by the sequences as shown in
Table II below.
TABLE-US-00002 TABLE II Bleaching Sequences Brown stock
Extracted/Kraft-cooked-kappa 25; Control/Kraft-cooked- kappa 25 Do
stage Kappa factor 0.08 for treated pulp (0.76% ClO.sub.2 applied
on pulp) Kappa factor 0.08 for control pulp (0.76% ClO.sub.2
applied) Kappa factor 0.14 for control pulp (1.33% ClO.sub.2
applied) 40 minutes at 50.degree. C., consistency 4% Eop Stage 90
minutes at 75.degree. C., consistency 10%, 0.4% H.sub.2O.sub.2
applied, 1.36% NaOH applied, O.sub.2 pressure 60 psi. D1 Stage 3
hours at 62.degree. C., consistency 10%, 0.73% ClO.sub.2 applied,
0.3% NaOH applied on pulp. Ep Stage 60 minutes at 75.degree. C.,
consistency 10%, 0.16% H.sub.2O.sub.2 applied, 0.46% NaOH applied
on pulp. D2 Stage 3.5 hours at 78.degree. C., consistency 10%,
0.21% ClO.sub.2 applied on pulp.
The brightness results are set forth in Table III below.
TABLE-US-00003 TABLE III Brightness Control Pulp- Control Pulp-
Treated Pulp-Kappa Kappa factor Kappa factor factor 0.08 in Do 0.08
in Do 0.14 in Do Brown stock 28.2 21.4 21.4 After D.sub.o 35.1 26.3
36.5 After Eop 62.1 (P#*3.3) 40.3 (P#7.1) 59.2 (P#4.1) After
D.sub.1 84.1 68 80.5 After Ep 87.5 70.8 83.9 After D.sub.2 91.8
82.4 89.5 *Permanganate Number
[0041] It is obvious that the treated pulp can be bleached much
easily. In this example, the savings in ClO.sub.2 dose is more than
11 lb per ton of pulp production. This is very significant
economical benefit. Moreover, this also indicates that if a
"normal" dose of ClO.sub.2 is used in the D.sub.o stage (i.e.,
kappa factor of 0.14 to 0.2) for the modified Kraft pulp, a very
high brightness pulp (much above the traditional pulp brightness
ceiling of .about.90 ISO Brightness) can be made. In fact, a very
high brightness pulp can be used in the manufacture of high
brightness papers and saving optical brightener usage.
[0042] Example 2 The modified pulp and the control pulp, which had
been bleached with the same dose of ClO.sub.2 bleaching chemicals
as in Example 1, were refined to various level of freeness. The
bulk was determined by the procedures above and the smoothness was
determined by the procedure of T538 om-01 (TIP#202). The water
retention was determined using the following equipment and
procedure.
I. Equipment:
[0043] 1. Laboratory centrifuge with free swinging head [0044] 2.
Centrifuge cups [0045] 3. filter tubes with fine mesh screens (100
mesh) and screw caps--Custom made (WRV cells) [0046] 4. 2-Liter
Vacuum flask with rubber adapter to fit centrifuge cups [0047] 5.
Rubber tipped glass rod or equivalent [0048] 6. Beaker, 250 ml
[0049] 7. Weighing balance [0050] 8. Indelible pencil [0051] 9.
Drying oven (105.degree. C.) [0052] 10. Dissector jar
II. Procedure:
[0052] [0053] 1. Determine consistency of pulp sample(s) and weight
out enough to provide 1 gram of bone-dry fiber per sample. [0054]
2. Carefully place sample in beaker and dilute with distilled water
to about 0.5% consistency. [0055] 3. Mount WRV cell on filter
flask. While swirling the sample, pour enough into the cell to
nearly fill it. Apply vacuum until most water is drained, but do
not pull air through the pad. Repeat filling and draining until all
fiber is on the pad, and most of the water is drained. Use spatula;
if necessary get all fiber on the mat. [0056] 4. Do the same with
another WRV cell and some of the same pulp (duplicate). [0057] 5.
Place WRV cells in centrifuge, and spin at 2000 rpm for 30 minutes.
[0058] 6. Remove the plugs, and label the plugs with an indelible
pencil. [0059] 7. Weigh wet plugs and record weights. [0060] 8. Dry
plugs at 105.degree. C. for four hours. [0061] 9. Weigh dry plug in
a hot balance. Record dry weight. The results are set forth in
Table IV below and in FIGS. 2 and 3.
TABLE-US-00004 [0061] TABLE IV Water Freeness, Retention Bulk,
Sheffield csf Value, g/g cc/g Smoothness Modified 575 (unrefined)
1.59 2.04 296 Pulp 558 -- 1.88 256 493 1.7 1.76 238 476 1.74 1.76
225 463 1.77 1.70 221 432 1.72 1.67 212 Control 445 (unrefined)
1.95 1.60 216 Pulp 315 2.09 1.52 186 220 2.17 1.49 136 206 2.38
1.51 122
[0062] Freeness and water retention values are indications of paper
drainage and dewatering. As shown in FIG. 2, the data shows that
the modified pulp may be dewatered and dried faster on
paper-machine than the unmodified pulp. The data also demonstrates
that the paper bulk is significantly improved. As shown in FIG. 3,
this is even true when comparing the bulk increase at the same
smoothness of paper.
EXAMPLE 3
[0063] Modified Kraft pulp was also made from Southern Pine chips.
Like the hardwood case, significant bleaching savings was obtained.
Table V below indicates the reduced fiber coarseness of the
modified pulp vs. the control pulp at the same kappa number of 26.
The test was done by Kajaani FiberLab tester.
TABLE-US-00005 TABLE V Modified Pine Control pine Fiber Coarseness,
26.1 29.2 mg/100 m
EXAMPLE 4
[0064] Bleached southern hardwood Kraft pulp was treated with NaOH
solution (the concentration of NaOH being 5% based on the total
system of pulp and water) at ambient temperature for 15 minutes.
This is an alternative way of extracting hemicelluloses from the
fibers. The pulp was then thoroughly washed with water, and made
into Tappi hand-sheets. Paper bulk of paper formed from the
modified pulp was 2.03 cc/g, while the control paper bulk was 1.85
cc/g. The brightness was also increased from the control of ISO
86.4 to the modified pulp of ISO 89.2.
* * * * *