U.S. patent application number 10/927890 was filed with the patent office on 2005-06-09 for method for the fabrication of a fiber web.
Invention is credited to Doelle, Klaus, Sieberth, Ralf.
Application Number | 20050121157 10/927890 |
Document ID | / |
Family ID | 34635049 |
Filed Date | 2005-06-09 |
United States Patent
Application |
20050121157 |
Kind Code |
A1 |
Doelle, Klaus ; et
al. |
June 9, 2005 |
Method for the fabrication of a fiber web
Abstract
A method for the fabrication of a fibrous web including the
steps of loading fibers with a precipitant, thereby defining
treated fibers. Creating at least a portion of the precipitant as
crystalline precipitant particles. Supplying the treated fibers as
a pumpable fiber stock suspension to a sheet forming process that
forms the fibrous web. And, controlling filler distribution across
a web cross section of the fibrous web by way of a vacuum supply in
the sheet forming process.
Inventors: |
Doelle, Klaus; (Kisslegg,
DE) ; Sieberth, Ralf; (Appleton, WI) |
Correspondence
Address: |
Todd T. Taylor
Taylor & Aust, P.C.
142 S. Main Street
P.O. Box 560
Avilla
IN
46710
US
|
Family ID: |
34635049 |
Appl. No.: |
10/927890 |
Filed: |
August 27, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10927890 |
Aug 27, 2004 |
|
|
|
PCT/EP03/50032 |
Feb 25, 2003 |
|
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Current U.S.
Class: |
162/9 ;
162/181.2; 162/182; 162/183 |
Current CPC
Class: |
D21H 17/675 20130101;
D21H 21/52 20130101; D21H 11/12 20130101; D21H 17/70 20130101 |
Class at
Publication: |
162/009 ;
162/182; 162/181.2; 162/183 |
International
Class: |
D21H 011/16 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 28, 2002 |
DE |
102 08 983.3 |
Claims
What is claimed is:
1. A method for the fabrication of a fibrous web, comprising the
steps of: loading fibers with a precipitant, thereby defining
treated fibers; creating at least a portion of said precipitant as
crystalline precipitant particles; supplying said treated fibers as
a pumpable fiber stock suspension to a sheet forming process that
forms the fibrous web; and one of controlling and regulating filler
distribution across a web cross section of the fibrous web by way
of a vacuum supply in said sheet forming process.
2. The method of claim 1, wherein said crystalline precipitant
particles have a size in a range of approximately 0.05 .mu.m to 0.5
.mu.m.
3. The method of claim 1, wherein said crystalline precipitant
particles have a size in a range of approximately 0.1 .mu.m to 2.5
.mu.m.
4. The method of claim 1, wherein said crystalline precipitant
particles have a size in a range of approximately 0.3 .mu.m to 0.8
.mu.m.
5. The method of claim 1, wherein said crystalline precipitant
particles have a size in a range of approximately 0.05 .mu.m to 0.1
.mu.m.
6. The method of claim 1, wherein said crystalline precipitant
particles are calcium carbonate.
7. The method of claim 1, further comprising the steps of: adding
at least one of calcium oxide and calcium hydroxide for loading
said fibers with calcium carbonate; and treating said fiber stock
suspension with carbon dioxide, thereby triggering a precipitation
of said particles.
8. The method of claim 7, wherein said calcium hydroxide is in a
liquid form.
9. The method of claim 8, wherein said calcium hydroxide is in a
dry form.
10. The method of claim 1, wherein the fibrous web is
newsprint.
11. The method of claim 1, wherein the fibrous web is a SCA
paper.
12. The method of claim 1, wherein the fibrous web is a LWC coated
paper.
13. The method of claim 1, wherein the fibrous web is a ULWC
paper.
14. The method of claim 1, wherein the fibrous web is a wood-free
non-coated paper.
15. The method of claim 1, wherein the fibrous web is a wood-free
coated paper.
16. The method of claim 1, wherein the fibrous web is a white lined
Liner.
17. The method of claim 1, wherein the fibrous web is bleached
types of cardboard.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation of PCT application No.
PCT/EP03/50032, entitled "METHOD FOR PRODUCING A FIBROUS WEB",
filed Feb. 25, 2003.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates to a method for the fabrication of a
fibrous web, particularly a paper or cardboard web.
[0004] 2. Description of the Related Art
[0005] Conventionally, precipitated calcium carbonate (PCC) is used
as a filler during paper production. However, a uniform
distribution of the filler particles throughout the formed sheet
with the objective of achieving a constant ash content or level, as
well as optimum printability, is at present technically not
possible.
[0006] Loading fibers with an additive, for example a filler, may
occur through a chemical precipitation reaction, that is especially
by way of a so-called "Fiber Loading" process, such as the one
described, in U.S. Pat. No. 5,223,090. In such a fiber loading
process at least one additive, especially a filler, is deposited on
the wetted fiber surfaces of the fiber material. In this process
the fibers may, for example, be loaded with calcium carbonate.
Calcium oxide and/or calcium hydroxide is added to the moist
disintegrated fiber material in such a way that at least some of it
associates itself with the water that is contained in the fiber
material. The so treated fiber material is subsequently treated
with carbon dioxide.
[0007] What is needed in the art is an improved method of
distribution of filler particles.
SUMMARY OF THE INVENTION
[0008] It is the objective of the current invention to create an
improved method of the type mentioned above. The desired end result
is a more uniform distribution of the filler particles, as well as
improved printability should be achieved, over the methods.
[0009] This objective is met by the current invention with a method
for the fabrication of a fibrous web, especially a paper or
cardboard web whereby the fibers are loaded with a precipitant,
moreover creating crystalline precipitant particles. The so treated
fibers are supplied to a sheet forming process in the form of a
pumpable fiber suspension. During this sheet forming process, the
filler distribution occurring across the web cross section is
controlled and/or regulated by way of an appropriate vacuum
supply.
[0010] In accordance with one embodiment of the present invention,
crystalline precipitant particles, in a size range of approximately
0.05 .mu.m to approximately 0.5 .mu.m, especially in a range of 0.1
.mu.m to approximately 2.5 .mu.m and preferably in a range of
approximately 0.3 mm to approximately 0.8 .mu.m are created.
Crystalline precipitant particles can advantageously be produced in
a size range of approximately 0.05 .mu.m to approximately 0.1
.mu.m, and preferably in a range of approximately 0.3 .mu.m to
approximately 0.8 .mu.m. According to one embodiment of the
inventive method the precipitant is calcium carbonate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The above-mentioned and other features and advantages of
this invention, and the manner of attaining them, will become more
apparent and the invention will be better understood by reference
to the following description of an embodiment of the invention
taken in conjunction with the accompanying drawings, wherein:
[0012] FIGS. 1 to 9 schematically illustrate examples of various
filler or ash distributions for various former segments.
[0013] FIG. 10 schematically illustrates the influence of certain
factors upon the filler distribution in the z-direction.
[0014] FIG. 11 is a schematic comparison of a total ash
distribution in conventional paper, together with a possible total
ash distribution in a fiber loading (FL) paper product.
[0015] Corresponding reference characters indicate corresponding
parts throughout the several views. The exemplification set out
herein illustrates one preferred embodiment of the invention, in
one form, and such exemplification is not to be construed as
limiting the scope of the invention in any manner.
DETAILED DESCRIPTION OF THE INVENTION
[0016] Referring now to the drawings, it is especially advantageous
if calcium oxide and/or calcium hydroxide are added to the fiber
stock suspension for loading of the fibers with calcium carbonate,
and the precipitation is triggered by treating the fiber stock
suspension with carbon dioxide.
[0017] When, for example, loading the fibers with a filler, calcium
carbonate (CaCO.sub.3) can be deposited on the wetted fiber
surfaces by adding calcium oxide (CaO) and/or calcium hydroxide
(Ca(OH).sub.2) to the moist fiber material, whereby at least some
of it can associate itself with the water in the fiber volume. The
fiber material treated in this manner can then be treated with
carbon dioxide (CO.sub.2).
[0018] The term "wetted fiber surfaces" may include all wetted
surfaces of the individual fibers. This especially also includes
the instance where the fibers are loaded with calcium carbonate, or
any desired other precipitant, on their outside surface as well as
on their interior (lumen). According to this embodiment the fibers
may, for example, be loaded with the filler calcium carbonate,
whereby the deposit onto the wetted fiber surfaces occurs through a
so-called "Fiber Loading" process, as described in U.S. Pat. No.
5,223,090. In this fiber loading process, for example, the carbon
dioxide with the calcium hydroxide reacts to form water and calcium
carbonate.
[0019] The cited method can be utilized particularly advantageously
in the production of newsprint, especially with an ash content of
5% to 20%, of SCA paper, of LWC (light weight coated) paper, of
ULWC (ultra-light weight coated) paper, of wood-free non-coated
paper, of wood-free coated paper, of white lined liner and/or
bleached types of cardboard.
[0020] The cited method enables the fabrication of a totally new
grade of paper with uniform filler distribution across the entire
cross profile of the paper, as well as on the surface. The paper
manufacturer can therefore produce a sheet of paper whereby a more
uniform distribution of the filler content occurs, leading to
savings in raw material, most importantly wood or secondary fibers,
as well as to an improvement on the paper machine side where fewer
chemicals become necessary for the paper manufacturing process. It
is now possible to produce the same paper grade on a substantially
lighter basis, whereby the same gloss is achieved due to the more
uniform distribution of the fillers. Overall, this leads to savings
in fillers and fibers. On the side of the paper product,
improvements, relative to the physical and optical paper
characteristics, are achieved, thereby improving the paper quality.
Improvements with regard to printability result from the fact that
a more uniform distribution of printing ink particles, especially
on the printable surface is made possible since the paper surface
displays less roughness and a higher uniformity.
[0021] One embodiment of the inventive method provides for better
printability characteristics. The method relates to stock
production, as well as to paper fabrication. During stock
production, secondary fibers that were recovered from waste paper,
or primary fibers are disintegrated, deflaked and cleaned. In this
segment, relating to the stock production, the filler in the form
of precipitated calcium carbonate (PCC) is added to the fiber
preparation in such a manner that all fibers possess a more
uniformly distributed PCC layer. This is due to the fact that the
wood fibers or chemical pulp fibers are exposed to Ca(OH).sub.2 and
everything is being mixed. The mixture is then exposed to CO.sub.2
in a reactor where the CaCO.sub.3 (PCCC)-crystals are formed. The
size of the crystals may be in a range of approximately 0.05 .mu.m
to approximately 0.5 .mu.m, especially in a range of approximately
0.1 .mu.m to approximately 2.5 .mu.m and preferably in a range of
approximately 0.3 .mu.m to approximately 0.8 .mu.m. The crystals
may be deposited on the inside and on the outside of the fibers, or
they may be provided as free PCC particles, meaning they may be
present as solids in the water of the fiber pulp. The fiber pulp,
treated in this manner, can then be delivered as a pumpable fiber
stock suspension to the sheet forming or paper forming process.
Various additional steps are necessary for the formation of a fiber
web or a paper sheet, for example, dewatering (thickening),
compressing and calendering.
[0022] While the stock is produced in the above described manner, a
new paper product can be produced by modifying the manufacturing
process on the papermachine side.
[0023] Generally, the following machinery or devices are examples
of equipment used in the production of a paper web: Fourdrinier
machine, Hybrid-Former (Duo-Former.TM. D) and Gap-Former
(Duo-Former.TM. CFD). The filler distribution, occurring over the
cross profile, ensues from the drawing. Based on the utilization of
any type of forming device a higher or lower modest ash content
occurs on the paper surface side, which could negatively influence
the printability of the paper. Even when a light weight surface
coating is later applied to the paper, preferably no filler
distribution would be present on the cover surface. The coating
surface penetrates into the openings or gaps; however, it does not
cover the paper surface. This makes it difficult to print the
paper. The printing ink must cover the color of the fibers. Since
white light consists of the sum total of all complementary rainbow
colors, no white light radiation as such exists. This means that a
certain pigment size is only desirable for one color. Other colors
are reflected differently. Relative to the paper this means that a
high level filler content is necessary in order to produce a higher
level of whiteness, if the particles are not evenly distributed.
The coating surface adds more white pigments to the paper, thereby
making the white surface thicker so that the transit time of the
light beam is longer, resulting in a white color. If for example, a
room is painted brown or black a base of four or five layers of
white paint would be necessary in order to cover the base color.
The same applies to paper where more white pigments are necessary
to cover black, in order to produce paper having a high opacity.
The whiter the paper is, the less printing ink is required in order
to achieve the same result. In other words, when the filler
particles are uniformly spaced, less printing ink is required and
that the ink may penetrate into the basis paper sheet in the
Z-direction to a lesser extent. Adjustment of the vacuum at the
formers can facilitate a better filler distribution, see especially
the broken line curve in FIG. 1. When utilizing fiber stock, in
whose production the fibers were loaded with a precipitant, in
conjunction with any of the various forming devices, and combined
with a low level, (generally -1.5 m to -4 m) or a high level of -4
m to -7.5 m or preferably a medium level vacuum of -2 m to -6 m, as
well as together with a device for the application of a very light
weight coating a much better filler distribution, as well as a
better topographic paper surface that is a more uniform paper
surface, can be achieved. This means essentially also a lower
filler fluctuation, better running characteristics (runability) of
the paper machine and a lower requirement for retention aids and
opacity enhancing agents.
[0024] As far as SC (supercalendered) papers are concerned where
the fibers themselves are platicized during the calendering process
through pressure and heat, such that the paper surface is smoothed,
a substantially lower calendering expenditure is required to
achieve a certain quality of calendered paper.
[0025] With improved filler distribution in the paper sheet, less
coating and therefore less drying is required, since the fibers are
better covered with filler and the appropriate covering or ink
layer (coating). In addition, the printability of the paper is also
improved in that a multi-layer headbox is utilized with which the
filler distribution (PCC) in the paper can be influenced in cross
profile (X-section) direction. This, however, is only possible for
paper grades having basis weights that allow utilization of
multi-layer headboxes (>80 g/m.sup.2).
[0026] Multi-layer headboxes cannot be utilized for extremely
lightweight grades, such as newsprint (40-50 g/m.sup.2) and
telephone directory paper (28-40 g/m.sup.2). It is however feasible
to utilize multi-layer headboxes for basis weights higher than 50
g/m.sup.2.
[0027] With the "Fiber Loading" ("FL") technology, whether a
modified multi-layer or conventional single layer headbox is used,
the so-called "linting" is prevented. "Linting" refers to the
extraction of the fillers during dewatering, that is a so-called
"First Pass Retention" of the fillers. Improvements in a range of
5% to 50%, preferably in a range of 10% to 25% are possible. "FL"
stock, that is stock that was treated according to the "FL"
technology, possesses approximately 25-200 times greater freeness
than conventionally produced stock, based on the refining
process.
[0028] The raw paper produced in accordance with the present
invention has a higher level of thickening that can be influenced
with modified dewatering (DuoFormer, Fourdrinier, Gap-Former). Due
to the greater dewatering, a higher dry content is achieved after
the press section. This means, for example, that the paper enters
the press at a higher, or at the same dry content but exits the
press having a higher dry content (1% higher dry content saves
approximately four dryer cylinders). The improved dryness range is
within a range of approximately 0.1% to approximately 5%, and
preferably of about 0.5% to approximately 2%.
[0029] Utilization of the "FL" technology described above is
especially suitable for papers that require good printability and
at the same time as high, as possible, a degree of filler, combined
with a fiber content in the paper that is as low as possible. The
advantage is in that the filler particles establish themselves on
the fiber and not, as is the case with conventional fillers between
the hollow fiber cavities. A better printability is thereby
achieved since the printing ink is applied to the filler particles
and does not have to cover the fiber first. With this arrangement
the printing ink also penetrates the fibers to a lesser extent.
[0030] The uniform filler distribution in a given paper sheet is
therefore achieved by utilization of the so-called "Fiber Loading"
process by way of which the filler particles, that are known as
precipitated calcium carbonate (PCC), are deposited on, in and
in-between the fibers. The "Fiber Loading" process is applied in
the stock manufacturing device, known as stock preparation. The
treated stock may be pre-refined or may be refined subsequently, in
order to prepare it for the paper machine process.
[0031] When the stock, that was treated by a "Fiber Loading"
process, is brought onto a respective sheet forming wire, a paper
sheet having uniform filler distribution is produced. The filler
content is for example, approximately 50%, based on the solids mass
weight. Since approximately up to 25% of the total ash content is
deposited in and on the fibers, this has the effect that the sheet
already possesses an ash content, in a cross direction, of
approximately 25% of the desired total ash content. The filler
retention in the paper machines is in a range of approximately
30%-60% relative to the total filler content. This means that the
basis ash content, in the cross direction of an "FL" treated sheet,
is in a range of approximately 50% to approximately 85%. In
comparison, values achieved in a conventional process are 30% to
60%. In the subsequent press and dewatering process in the
papermachine, the filler content can be improved in the cross
direction. The objective, in the conventional sheet forming
process, is around 30% to 70% uniformly distributed filler content
in the cross direction, depending upon the paper manufacturing
process. When utilizing "FL" treated stock in the paper machine,
the filler content is distributed uniformly in the cross direction
in the paper sheet and may be approximately 55% or even 95%, based
on the paper manufacturing process.
[0032] A uniform filler distribution results in improved gloss
values. Improved gloss values mean greater whiteness in the sheet.
Since white light is formed by the sum total of all complementary
rainbow colors, no white light radiation as such exists. This means
that a pigment size is only useful for one color. Other colors are
reflected differently. Relative to paper this means that a high
filler content is necessary in order to produce a higher level of
whiteness, if the particles are not evenly distributed. Greater
whiteness can be achieved with a lower filler content through
uniform distribution of filler particles, since the filler
particles are spaced evenly across the cross section of the paper,
as well as distributed uniformly on the fibers. The optimum crystal
size is in a range of approximately 0.5 .mu.m to approximately 0.1
.mu.m and preferably in a range of approximately 0.3 .mu.m to
approximately 0.8 .mu.m.
[0033] Less filler is required when utilizing the optimum crystal
size, since the filler pigments are distributed evenly across the
fibers in order to achieve optimum optical characteristics. An
additional advantage is that more filler is retained through the
paper wire forming process, since smaller particles permit better
penetration within the sheet. This means that the sheet itself is
filled from the inside toward the outside with filler, thereby
achieving better filler retention throughout the sheet forming
process, leading to a uniform distribution in the paper and
achieving a higher paper production by treating the stock in the
following manner:
[0034] The fiber stock suspension, that was previously mixed with
Ca(OH).sub.2, is put into a crystallizing apparatus, for example a
Fluffer, Refiner, Disperger or similar device, at a consistency or
solids concentration in a range of approximately 5% to
approximately 60%, preferably in a range of approximately 15% to
approximately 35%. The Ca(OH).sub.2 may be added in liquid or dry
form. The fiber pulp is treated with CO.sub.2. The CO.sub.2 is
added at temperatures within a range of approximately -15.degree.
C. and approximately 120.degree. C., and preferably at temperatures
within a range of approximately 20.degree. C. and approximately
90.degree. C.
[0035] The fiber stock suspension comes into a gas zone where each
individual fiber is exposed to a gas atmosphere, followed by the
precipitation reaction, that immediately results in the CaCO.sub.3
formation. The CaCO.sub.3 crystals may be rhombohedral,
scalenohedral or globular in their form, whereby especially the
crystal mass depends upon the temperature range that is selected
for the fiber stock suspension, as well as the CO.sub.2 and
Ca(OH).sub.2 content in the fiber stock suspension. After the fiber
stock suspension, together with the formed crystals, has passed
through the gas zone, the formed PCC or the fiber stock suspension
with the crystals in the lumen, on the fibers and between the
fibers, is routed through a rotor and a stator where the
distribution of the crystals in the fiber stock suspension is
concluded by mixing at a low shear action.
[0036] When the fiber stock/crystal suspension passes through the
rotor a shear distribution occurs that results in a size
distribution of the crystals of approximately 0.05 .mu.m to
approximately 0.5 .mu.m and preferably of approximately 0.3 .mu.m
to approximately 1.0 .mu.m.
[0037] The form of the utilized filler particles is, for example,
rhombohedral with a respective cube size in a range of
approximately 0.05 .mu.m to approximately 1 .mu.m, or scalenohedral
with a respective length in a range of approximately 0.05 .mu.m to
approximately 1 .mu.m and a respective diameter in a range of
approximately 0.01 .mu.m to approximately 0.5 .mu.m, depending upon
the paper grade that is to be produced.
[0038] The longer the fiber stock suspension remains on the rotor
plate the less will be the shearing, depending on the H.sub.2O that
was added for thinning. The concentration of the fiber stock
suspension passing over the rotor plate is approximately 0.1% to
approximately 50% and preferably approximately 35% to approximately
50%.
[0039] The pressure supplied to the CO.sub.2 supply line is in a
range of approximately 0.1 bar to approximately 6 bar and
preferably in a range of approximately 0.5 bar to approximately 3
bar, in order to ensure a constant CO.sub.2 supply to the gas ring
to obtain the desired chemical reaction. The CO.sub.2 supply and
thereby the CaCO.sub.3 creating precipitation reaction can be
controlled and/or regulated through the pH value. pH values are in
a range of 6.0 pH to approximately 10.0 pH, preferably in a range
of approximately 7.0 pH to approximately 8.5 pH may be considered
for the concluding reaction of the CaCO.sub.3 crystals. The energy
utilized for this process is within a range of approximately 0.3
kWh/t and approximately 8 kWh/t and preferably within a range of
approximately 0.5 kWh/t and approximately 2.5 kWh/t. Dilution water
may be added and mixed with the fiber stock suspension, in order to
obtain a final dilution in which the produced fiber stock
suspension, with the filler, has a consistency or solids
concentration in a range, for example, of approximately 0.1% to
approximately 16%, preferably in a range of approximately 2% to
approximately 6%. The fiber stock suspension is then exposed to the
atmosphere in a machine, a container or in the process equipment
that follows in the process.
[0040] The rotational speed of the rotor plate may especially be in
a range of approximately 20 m/s to 100 m/s and preferably in a
range of approximately 40 m/s to approximately 60 m/s on its
outside diameter.
[0041] The speed through the rotor and the stator is in a range of,
for example, approximately 0.2 m/s to approximately 0.55 m/s and
preferably in a range of approximately 0.05 m/s and approximately
0.2 m/s, depending upon the filler content and the crystal
size.
[0042] According to current knowledge, the crystal filler content,
the crystal size and the speed are linearly linked. The gap between
rotor and stator is approximately 0.5 mm to approximately 100 mm,
and preferably approximately 25 mm to approximately 75 mm.
[0043] The diameter of the rotor and the stator can be especially
in a range of approximately 5 m to approximately 2 m.
[0044] The reaction time is for example in the range of
approximately 0.01 min. to 1 min, preferably in a range of
approximately 0.1 sec. to approximately 10 sec.
[0045] The method described above enables the production of
individual particles that are equally spaced from each other and
are deposited onto the fibers, whereby they cover the fibers in the
desired manner.
[0046] While this invention has been described as having a
preferred design, the present invention can be further modified
within the spirit and scope of this disclosure. This application is
therefore intended to cover any variations, uses, or adaptations of
the invention using its general principles. Further, this
application is intended to cover such departures from the present
disclosure as come within known or customary practice in the art to
which this invention pertains and which fall within the limits of
the appended claims.
* * * * *