Note: Descriptions are shown in the official language in which they were submitted.
CA 02572630 2006-12-28
METHOD TO MANUFACTURE PAPER
The present application claims the benefit of priority under 35 USC 119(e)
to United States
Provisional Patent Application 60/587,954, which is hereby incorporated, in
its entirety, herein by
reference.
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Field of the Invention
The present invention relates to a paper or paperboard substrate containing
fiber-filler
complexes as well as methods of making and using the same.
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Background of the Invention
Inorganic material such as precipitated calcium carbonate (PCC) ground calcium
carbonate (GCC), clay and talc are used extensively as fillers in the paper
making process. Filler
loading levels of 12-25wt% are typical in current paper making strategy to
improve optical
properties of the paper such as brightness and opacity. In some instances, the
economics of
substituting expensive fiber with inexpensive filler lends added incentive.
To insure that the fillers remain with the fiber web and ultimately with the
paper product,
retention aids are used. Normally retention aids are long chained polymeric
compounds that
flocculate the furnish and enhance filler-fiber "attachment." However, high
flocculation levels,
caused in part by retention aids, lead to non-uniformity in the web and poor
paper formation.
To circumvent this, a method to attach the filler directly on to the fiber
surfaces was
described in French Patent 92-04474 and U.S. Pat. Nos. 5,731,080 & 5,824,364
to Cousin et al
which are hereby incorporated in their entirety by reference. In these patents
a slip stream of pulp
furnish is refined to low freeness (<70 Canadian standard freeness [csf] vs.
450 csf, typically) and
then treated to generate a highly loaded filler-fiber complex. When these
complexes are
recombined with untreated pulp, any desirable filler level can be targeted.
An alternative approach is described in U.S. Pat. No. 5,679,220 to Matthew et
al. and U.S.
Pat. No. 5,665,205 to Srivatsa et al which are hereby incorporated in their
entirety by reference.
In both Srivatsa and Matthew the entire furnish is treated to nominal filler
loadings without
subjecting the pulp to high refining levels (low freeness). However, this
procedure results in
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increases in capital and operating costs due to the treatment of larger pulp
volumes. Accordingly,
there is a need in the art to generate filler-fiber complexes easily and
inexpensively.
It is known in the art to produce fiber-filler complexes by contacting a fiber
slurry with
slaked lime and carbon dioxide gas to precipitate calcium carbonate (PCC).
Such processes are
described in the Cousin et al., Srivatsa, and Matthew et al. patents. The
Cousin et al. patents
describe a process for obtaining a fiber-based composite produced by
precipitating calcium
carbonate in situ in an aqueous suspension of fibers of expanded surface area
having microfibrils
on their surface. The crystals of precipitated calcium carbonate (PCC) are
organized essentially in
clusters of granules directly grafted on to the microfibrils without any
binders or retention aids
such that the crystals trap the microfibrils by reliable and non-labile
bonding. Srivatsa et al.
describes in situ precipitation on secondary fiber furnish. Whereas the Cousin
et al. patents
describe a batch reaction process, Matthew et al. describes a continuous
process for forming
fiber-filler complexes.
Typically, as you refine pulp, more surface area is generated and additional
anchoring
sites are created on the fiber. However, US Patent No. 6,592,712, which is
hereby incorporated,
in its entirety, herein by reference, provides a source of fiber having a high
surface area without
the need for additional refining by obtaining them from process streams within
the paper making
process. However, the internally recirculated high surface area fiber stream
containing the
recirculated fibers, also known as "fines", used is quite variable because it
contains residuals of
unretained filler and other papermaking materials such as sizing agents,
optical brightening
agents in addition to dyes and pigments. These chemicals can lead to problems
in their
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subsequent use, such as quenching of residual sizing and OBAs when exposed to
the high pH
environments such as those required during the start of PCC formation. In
addition, the
utilization of the highly variable streams containing the "fines" can lead to
problems with
uniformity within a paper substrate made therefrom.
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SUMMARY OF THE INVENTION
One aspect of the present invention is a paper substrate, containing a
plurality of fibers
from hardwood species, softwood species or mixtures thereof that are greater
than or equal to 75
m in length on average and having a filler attached thereto a portion of said
plurality and also
containing less than 50wt % fibers that are less than 75 gm in length on
average based upon the
total weight of the substrate. The fibers that are hardwood species, softwood
species or mixtures
thereof may have a Canadian Standard Freeness of from 300 to 600 and may be
virgin fibers.
The fibers that are less than 75 m in length on average may be recycled
fibers, recirculated
fibers, waste fibers, or mixtures thereof. The fibers that are less than 75 gm
in length may be
present in an amount that is from 0.1 to 20wt% based upon the total weight of
the substrate.
Another aspect of the present invention is a paper substrate, containing a
plurality of
fibers from hardwood species, softwood species or mixtures thereof that are
greater than or equal
to 75 pm in length on average and having a filler attached thereto a portion
of said plurality and
also containing less than 50wt % fibers that are less than 75 m in length on
average based upon
the total weight of the substrate where the filler is present in an amount of
from 1 to 30wt% based
upon the total weight of the substrate. The filler may be attached at a filler
to fiber weight ratio
of from 0.3 to 8. The filler may be precipitated. Further, the filler may be
precipitated calcium
carbonate. The filler may be in at least one shape of selected from the group
consisting of cubic,
scalenohdral, rhombic, and aragonite. The filler has an average particle size
of from 0.01 to 20
~=
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Another aspect of the present invention is a method of making a paper
substrate by
contacting a plurality of fibers from hardwood species, softwood species or
mixtures thereof that
are greater than or equal to 75 gm in length on average and having a filler
attached thereto a
portion of said plurality with fibers that are less than 75 m in length on
average based upon the
total weight of the substrate.
Another aspect of the present invention is a method of making a paper
substrate by
contacting the plurality of fibers from hardwood species, softwood species or
mixtures thereof
that are greater than or equal to 75 m in length on average with Ca(OH)2
and/or CO2
simultaneously and/or sequentially.
Another aspect of the present invention is a method of making a paper
substrate by
contacting the plurality of fibers from hardwood species, softwood species or
mixtures thereof
that are greater than or equal to 75 m in length on average in-line with
Ca(OH)2 to form a slurry
having less than 5% solids.
Another aspect of the present invention is a method of making a paper
substrate by
contacting the plurality of fibers from hardwood species, softwood species or
mixtures thereof
that are greater than or equal to 75 g.m in length on average with COZ gas
prior to contacting the
plurality of fibers with Ca(OH)2.
Another aspect of the present invention is a method of making a paper
substrate by
contacting the plurality of fibers from hardwood species, softwood species or
mixtures thereof
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that are greater than or equal to 75 m in length on average with CO2 gas
prior to contacting the
plurality of fibers with Ca(OH)2.
Another aspect of the present invention is a method of making a paper
substrate by
contacting the plurality of fibers from hardwood species, softwood species or
mixtures thereof
that are greater than or equal to 75 gm in length on average with Ca(OH)2
and/or CO2
simultaneously and/or sequentially at a pH of from 7.5 to 11.
Another aspect of the present invention is a method of making a paper
substrate by
contacting the plurality of fibers from hardwood species, softwood species or
mixtures thereof
that are greater than or equal to 75 m in length on average with Ca(OH)2
and/or CO2
simultaneously and/or sequentially in a tubular reactor, wherein CO2 is added
to the reactor at
multiple addition points.
Another aspect of the present invention is a method of making a paper
substrate by
contacting the plurality of fibers from hardwood species, softwood species or
mixtures thereof
that are greater than or equal to 75 m in length on average with Ca(OH)2
and/or COZ
simultaneously and/or sequentially in a series of continuous stirring tank
reactor, wherein COZ is
added to each of the continuous stirring tank reactor in the series.
Another aspect of the present invention is a method of making a paper
substrate by
contacting both the plurality of fibers from hardwood species, softwood
species or mixtures
thereof that are greater than or equal to 75 gm in length on average and the
fibers that are less
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than 75 m in length on average with Ca(OH)2 and/or COZ simultaneously and/or
sequentially in
a series of continuous stirring tank reactor, wherein COZ is added to each of
the continuous
stirring tank reactor in the series.
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BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1: A plot of Sheffield smoothness, in Sheffield Units (SU), of the ID
side of a paper
substrate versus the wt% ash contained in that paper substrate.
FIG. 2: A plot of Sheffield smoothness, in Sheffield Units (SU), of the NS
side of a paper
substrate versus the wt% ash contained in that paper substrate.
FIG. 3: A table comparing the fluorescence of the residual OBA from a SaveAll
fiber fine stream
sample before and after the sample is reacted to form the fiber fine-filler
complex.
FIG. 4 is a schematic diagram of a process employing several of the features
of the present
invention.
FIG. 5 is a schematic representation of one embodiment of an apparatus for
carrying out the
process of the present invention.
FIG. 6 is a schematic representation of one embodiment of a process, combined
with apparatti for
carrying out the process of the present invention.
FIG. 7 is a schematic representation of one embodiment of a process to make a
fiber-filler
complex where a (plug flow) reactor is used and a series of CO2 addition occur
throughout the
reactor.
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FIG. 8 is a schematic representation of one embodiment of a process to make a
fiber-filler
process where multiple continuous stirring tank reactors are used in series.
FIG. 9 is paper substrate comparison as a function of precipitated filler
morphology.
FIG. 10 is SEM showing morphology results of tubular reactor.
FIG. 11 is first SEM showing morphology results of CSTR reactor.
FIG. 12 is second SEM showing morphology results of CSTR reactor.
FIG. 13 is first SEM showing cubic morphology.
FIG. 14 is second SEM showing cubic morphology.
FIG. 15 is third SEM showing cubic morphology.
FIG. 16 is fourth SEM showing cubic morphology.
FIG. 17 is a plot of HST sizing vs % PCC.
FIG. 18 is a plot of Modulus vs % PCC.
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FIG. 19 is a plot of internal bond vs % PCC.
FIG. 20 is a plot of GM breaking lenght vs % PCC.
FIG. 21 is a plot of GM Taber Stiffness vs % PCC.
FIG. 22 is a plot of Brightness with UV vs % PCC.
FIG. 23 is a plot of Brightness without UV vs % PCC.
FIG. 24 is a plot of Flourescence (delta Brightness) vs % PCC.
FIG. 25 is a very preferred embodiment of the process of making the fiber
filler complex.
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DETAILED DESCRIPTION OF THE INVENTION
The present inventors have discovered a method of making a paper or paperboard
substrate containing fiber-filler complexes, as well as a method of making the
same, that solves
all of the above-mentioned problems identified while utilizing conventional
paper substrates and
methodologies.
The paper substrate contains a web of cellulose fibers. The paper substrate of
the present
invention may contain recycled fibers and/or virgin fibers. Recycled fibers
differ from virgin
fibers in that the fibers have gone through the drying process several times.
The paper substrate of the present invention may contain from 1 to 99 wt%,
preferably
from 5 to 95 wt%, most preferably from 60 to 80 wt% of cellulose fibers based
upon the total
weight of the substrate, including 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50,
55, 60, 65, 70, 75, 80,
85, 90, 95 and 99 wt%, and including any and all ranges and subranges therein.
Preferably, the sources of the cellulose fibers are from softwood and/or
hardwood. The
paper substrate of the present invention may contain from 1 to 99 wt%,
preferably from 5 to 95
wt%, cellulose fibers originating from softwood species based upon the total
amount of cellulose
fibers in the paper substrate. 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 IOOwt%, including any and all ranges and
subranges therein, based
upon the total amount of cellulose fibers in the paper substrate.
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The paper substrate may alternatively or overlappingly contain from 0.01 to
100 wt%
fibers from sofl.wood species, preferably from 0.01 to 50wt%, most preferably
from 5 to 40wt%
based upon the total weight of the paper substrate. The paper substrate
contains not more than
0.01, 0.05, 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 25, 30,
35, 40, 45, 50, 55, 60, 65,
70, 75, 80, 85, 90, 95 and 100wt% fines based upon the total weight of the
paper substrate,
including any and all ranges and subranges therein.
The paper substrate may contain softwood fibers from softwood species that
have a
Canadian Standard Freeness (csf) of from 300 to 700, more preferably from 250
to 650, most
preferably from 400 to 550 esf. This range includes 300, 310, 320, 330, 340,
350, 360, 370, 380,
390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, 500, 510, 520, 530,
540, and 550 csf,
including any and all ranges and subranges therein.
The paper substrate of the present invention may contain from 1 to 99 wt%,
preferably
from 5 to 95 wt%, cellulose fibers originating from hardwood species based
upon the total
amount of cellulose fibers in the paper substrate_ 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 in the
paper substrate.
The paper substrate may alternatively or overlappingly contain from 0.01 to
100 wt%
fibers from hardwood species, preferably from 50 to 100wt%, most preferably
from 60 to 99wt%
based upon the total weight of the paper substrate. The paper substrate
contains not more than
0.01, 0.05, 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 25, 30,
35, 40, 45, 50, 55, 60, 65,
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70, 75, 80, 85, 90, 95, 99 and 100wt% fines based upon the total weight of the
paper substrate,
including any and all ranges and subranges therein.
The paper substrate may contain softwood fibers from hardwood species that
have a
Canadian Standard Freeness (csf) of from 300 to 700, more preferably from 250
to 650, most
preferably from 400 to 550 csf. This range includes 300, 310, 320, 330, 340,
350, 360, 370, 380,
390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, 500, 510, 520, 530,
540, and 550 csf,
including any and all ranges and subranges therein.
When the paper substrate contains 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.
The hardwood and soft wood fibers are preferably not less than 75 m in length
on
average, more preferably not less than 80 m in length, most preferably not
less than 100 gm in
length. The length of these fibers are greater than or equal to 75, 77, 80,
82, 85, 87, 90, 92, 95,
97, an 100 m in length, including any and all ranges and subranges therein
and well as any
ranges and subranges therein.
Further, the softwood and/or hardwood fibers contained by the paper substrate
of the
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present invention may be modified by physical and/or chemical means. Examples
of physical
means include, but is not limited to, electromagnetic and mechanical means.
Means for electrical
modification include, but are not limited to, means involving contacting the
fibers with an
electromagnetic energy source such as light and/or electrical current. Means
for mechanical
modification include, but are not limited to, means involving contacting an
inanimate object with
the fibers. Examples of such inanimate objects include those with sharp and/or
dull edges. Such
means also involve, for example, cutting, kneading, pounding, impaling, etc
means.
Examples of chemical means include, but is not limited to, conventional
chemical fiber
modification means including crosslinking and precipitation of complexes
thereon. Examples of
such modification of fibers may be, but is not limited to, those found in the
following patents
6,592,717, 6,592,712, 6,582;557, 6,579,415, 6,579,414, 6,506,282, 6,471,824,
6,361,651,
6,146,494, H1,704, 5,731,080, 5,698,688, 5,698,074, 5,667,637, 5,662,773,
5,531,728,
5,443,899, 5,360,420, 5,266,250, 5,209,953, 5,160,789, 5,049,235, 4,986,882,
4,496,427,
4,431,481, 4,174,417, 4,166,894, 4,075,136, and 4,022,965, which are hereby
incorporated, in
their entirety, herein by reference.
Sources of "Fines" may be found in SaveAll fibers, recirculated streams,
reject streams,
waste fiber streams. The amount of "fines" present in the paper substrate can
be modified by
tailoring the rate at which such streams are added to the paper making
process.
The paper substate preferably contains a combination of hardwood fibers,
softwood fibers
and "fines" fibers. "Fines" fibers are, as discussed above, recirculated and
are typically not more
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that 100 m in length on average, preferably not more than 90 gm, more
preferably not more than
80 m in length, and most preferably not more than 75 m in length. The length
of the fines are
preferably not more than 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65,
70, 75, 80, 85, 90, 95,
and 100 m in length, including any and all ranges and subranges therein.
The paper substrate contains from 0.01 to 100 wt% fines, preferably from 0.01
to 50wt%,
most preferably from 0.01 to 15wt lo based upon the total weight of the
substrate. The paper
substrate contains not mort than 0.01, 0.05, 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 6,
7, 8, 9, 10, 12, 15, 20, 25,
30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 and 100wt% fines based
upon the total
weight of the paper, including any and all ranges and subranges therein.
The paper substrate may alternatively or overlappingly contain from 0.01 to
100 wt%
fines, preferably from 0.01 to 50wt%, most preferably from 0.01 to 15wt% based
upon the total
weight of the fibers contained by the paper substrate. The paper substrate
contains not more than
0.01, 0.05, 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 25, 30,
35, 40, 45, 50, 55, 60, 65,
70, 75, 80, 85, 90, 95 and 100wt% fines based upon the total weight of the
fibers contained by the
paper substrate, including any and all ranges and subranges therein.
The paper substrate, in one embodiment of the present invention, may contain
less fiber
"fines" and more long fresh hardwood and/or softwood fibers, preferably
virgin. The net affect
of the paper substrate is to have a web of cellulose fibers that are more de-
bonded than if there
were a higher amount of "fines" in the substrate. Utilization of the longer
hard long fresh
hardwood and/or softwood fibers, preferably virgin, over the fiber fines may
result in a less dense
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sheet containing higher bulk that may be more compressible and uniform
resulting in improved
smoothness after pressing and/or calendaring. This ideal is demonstrated by
Example I below
combined with Figures 1 and 2 show a plot of the Sheffield smoothness, in
Sheffield Units (SU),
of the ID and NS sides, respectively, of a paper substrate versus the wt% ash
contained in that
paper substrate. One paper substrate contained highly refined SaveAll pulp
with high surface
area, while the other contained unrefined pulp. There is a smoother surface at
equal ash content
for the paper substrates containing the unrefined pulp than those paper
substrates containing
highly refined and/or recycled and/or SaveAll pulp at the same ash content.
The paper substrate of the present invention may contain a filler.
Fillers may be inorganic. Examples of fillers include, but are not limited to;
clay, talc,
calcium carbonate, calcium sulfate hemihydrate, and calcium sulfate dehydrate.
A preferable
filler is calcium carbonate with the preferred form being precipitated calcium
carbonate even
though it also may in the form of ground calcium carbonate.
The paper substrate of the present invention may contain from 0.001 to 50 wt%
of the
filler based on the total weight of the substrate, preferably from 0.01 to 40
wt%, most preferably
1 to 30wt%, of at least one of the filler. This range includes 0.00 1, 0.002,
0.005, 0.006, 0.008,
0.01, 0.02, 0.03, 0.04, 0.05, 0.1, 0.2, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 4,
5, 6, 8, 10, 12, 14, 15, 16,
18, 20, 22, 25, 30, 35, 40, 45 and 50wt% based on the total weight of the
substrate, including any
and all ranges and subranges therein.
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The paper substrate preferably contains a fiber-filler complex, more
preferably a fiber
CaCO3 complex. The fiber-filler is a complex in which the fiber and the filler
are engaged in
either a chemical and/or physical interaction. Methods of making the fiber-
filler complex may be
any conventional method, including those described in French Patent 92-04474
and U.S. Pat.
Nos. 5,731,080; 5,824,364; 5,679,220; 6,592,712, and 5,665,205, which are
hereby incorporated,
in their entirety, herein by reference. Further embodiments of making the
fiber-filler complex is
found in Figures 4-6.
The paper substrate preferably contains a fiber-filler complex that is
preferably made by
the methods described herein. The fiber-filler is a complex in which the fiber
and the filler are
engaged in either a chemical and/or physical interaction. The ratio of the
filler to fiber can be any
ratio. The filler/fiber ratio may be from 0.00 1 to 1000. The filler/fiber
ratio may be 0.00 1, 0.005,
0.01, 0.02, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.4,
1.6, 1.8, 2.0, 2.2, 2.5, 3.0, 4,
5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95,
100, 110, 120, 130, 140,
150, 160, 170, 180, 190, 200, 225, 250, 300, 350, 400, 450, 500, 550, 600,
650, 700, 750, 800,
850, 900, 950, and 1000, including any and all ranges and subranges therein.
The average particle size of the filler when in the fiber filler complex may
be any particle
size. Examples of the average particle sizes of the filler in the fiber filler
complex are those from
0.01 to 20 m. The average particle size of the filler may be 0.01, 0.02,
0.05, 0.1, 0.2, 0.3, 0.4,
0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.1, 2.2, 2.3, 2.4,
2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.12,
3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6,
4.7, 4.8, 4.9, 5.0, 5.2, 5.5, 5.7,
6.0, 6.2, 6.5, 6.7, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 11, 12, 13, 14, 15, 16,
17, 18, 19, and 20,
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including any and all ranges and subranges therein.
The average surface area of the filler particle in the fiber filler complex
may be any
particle size. Examples of the surface area of the filler particle in the
fiber filler complex are
those from 0.1 to 20 m 2/g. The surface area of the filler particle in the
fiber filler complex may
be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0,
2.1, 2.2, 2.3, 2.4, 2.5, 2.6,
2.7, 2.8, 2.9, 3.0, 3.12, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1,
4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.2, 5.5, 5.7, 6.0, 6.2, 6.5,
6.7, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 11, 12, 13, 14, 15, 16, 17,
18, 19, and 20, including any and all ranges and subranges therein.
The amount of filler attached the fiber in the fiber filler complex may be
from 1 to
100wt% attachment, preferably at least 9wt% attachment, more preferably at
least 15wt%
attachment, most preferably at least 20wt% attachment based upon the total
amount of the filler
that is added to the reactor. The amount of filler attached the fiber in the
fiber filler complex may
be at least 1, 2, 3, 5, 7, 10, 12, 15, 17, 20, 25, 30, 35, 40, 45, 50, 55, 60,
65, 70, 75, 80, 85, 80, 95,
and 99wt%, including any and all ranges and subranges therein.
The filler is preferably precipitated when in the fiber filler complex. When
precipitated,
the filler may be of any shape commonly known that precipitated crystals may
form. Examples
of shapes may be cubic, scalenohdral, rhombic, and/or aragonite. Preferably,
the shapes are cubic
and/or aragonite.
The paper substrate may contain from 0.1 to 100wt% fiber filler complex based
upon the
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total weight of the substrate, including 0.1, 0.2, 0.5, 1, 5, 10, 15, 20, 25,
30, 35, 40, 45, 50, 55, 60,
65, 70, 75, 80, 85, 90, 95 and 100 wt%, and including any and all ranges and
subranges therein.
The fiber filler complex may be made by contacting the fibers, Ca(OH)2 and/or
COZ
simultaneously and/or consecutively to form a fiber-CaCO3 complex.
The fibers to be added to create the fiber-filler complex may have from 3 to
200 m2/g,
including 3, 5, 10, 15, 20, 25, 30, 40, 50, 60, 70, 80, 90, 100, 125, 150,
175, 200, 225, 250, 275
and 300 m2/g, including any and all ranges and subranges therein.
The fiber-filler complex may be made by adding less than or equal to 5% solids
Ca(OH)2,
including less than or equal to 0.1, 0.2, 0.3, 0.5, 0.75, 1.0, 1.2, 1.4, 1.6,
1.8, 2.0, 2.5, 3.0, 3.5, 4.0,
4.5, and 5.0% solids Ca(OH)Z based upon the weight of the reactants, including
any and all
ranges and subranges therein. However, any % solids of Ca(OH)2 may be used.
The fiber-filler complex may be made by adding less than or equal to % solids
C02,
including less than or equal to 0.1, 0.2, 0.3, 0.5, 0.75, 1.0, 1.2, 1.4, 1.6,
1.8, 2.0, 2.5, 3.0, 3.5, 4.0,
4.5, and 5.0% solids CO2 based upon the weight of the reactants, including any
and all ranges and
subranges therein. However, any % solids of CO2 may be used.
In a preferred embodiment, the fibers are contacted with COz
The source of the fibers may be any source. Further, the fibers may be
premixed with a
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gas, liquid, and/or solid carrier such as water, but this is not necessary.
The source of Ca(OH)2 may be any source. Further, Ca(OH)2 and/or its source
may be in
the form of a gas, liquid and/or solid. Still further, the Ca(OH)2 and/or its
source may be
premixed with a gas, liquid, and/or solid carrier such as water, but this is
not necessary.
Preferably, the Ca(OH)2 source may be lime.
The source of CO2 may be from any source. Further, CO2 and/or its source may
be in the
form of a gas, liquid and/or solid. Still further, the COZ and/or its source
may be premixed with a
gas, liquid, and/or solid carrier such as water, but this is not necessary.
Preferably, the CO2 is in
the form of a gas and/or liquid.
The CO2 may be added to the fibers at any time in the process of making the
fiber-filler
complex. That is, CO2 may be added to the fibers before the fibers enter the
reactor, reaction
zone, and/or contact zone. Also, CO2 may be added to the fibers when the
fibers enter the
reactor, reaction zone, and/or contact zone.
In one embodiment of the present invention, the fiber-filler complex is made
by
contacting the fibers with CO2 prior to contacting the fibers with Ca(OH)2.
In another embodiment of the present invention, the fiber filler complex is
made by
mixing, in-line, Ca(OH)2 in the form of lime with the fibers.
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WO 2006/019808 PCT/US2005/024837
In another embodiment, the fibers are contacted with CO2, then mixed in-line
with
Ca(OH)2 in the form of lime. The fibers and the Ca(OH)2 in the form of lime
form a slurry less
than or equal to 5% solids, preferably from 1 to 4% solids, most preferably
from 1.5 to 2.5%
solids. The % solids of the slurry may include 0. l, 0.2, 0.3, 0.5, 0.75, 1.0,
1.2, 1.4, 1.6, 1.8, 2.0,
2.5, 3.0, 3.5, 4.0, 4.5, and 5.Owt%, including any and all ranges and
subranges therein.
The fibers, Ca(OH)2 and/or CO2 may be contacted together at any pH.
Preferably, the pH
is greater than or equal to 6, more preferably the pH may be from 6 to 12,
most preferably from 8
to 10.5. The pH may be 1, 2, 3, 4, 5, 6, 7, 7.5, 8, 8.5, 8, 9.5, 10, 10.5, 11,
11.5, 12, 12.5, 13, and
14, including any and all ranges and subranges therein.
The fibers, Ca(OH)2 and/or COZ may be contacted together in any manner.
Preferably, the
contacting occurs in at least one reactor. Examples of reactors include a
tubular reactor, a tank
reactor, a continuous stirring tank reactor (CSTR), a continuous tubular
reactor, and/or plug flow
reactor. Preferably, a tubular (plug flow) reactor and/or a series of
continuous stirring tank
reactors are utilized.
When CO2 may be further added to the process by adding it at least once to the
reactor, a
series of CO2 additions throughout the reactor is also preferable.
When a continuous a tubular (plug flow) reactor is used, it is preferable that
a series of
CO2 addition occur throughout the reactor. This embodiment can be seen in
Figure 7.
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WO 2006/019808 PCT/US2005/024837
When a continuous stirring tank reactor is utilized, it is preferable to use
multiple
continuous stirring tank reactors in series. This embodiment can be seen in
Figure 8.
The reaction conditions may be such so as to promote the fiber and the filler
engaged in
either a chemical and/or physical interaction.
The method of making the fiber filler complex may be added to any conventional
papermaking process. Methods and apparatuses for making paper substrates and
paper-related
materials are well known in the paper and paperboard art. See for example,
G.A. Smook
referenced above and references cited therein all of which is hereby
incorporated by reference.
All such known papermaking methods can be used in the practice of this
invention and will not
be described in detail. The fiber filler complex may be added to the process
in a manner that
replaced entirely and/or in part the conventional fibers utilized. The fiber
filler complex may be
added to the papermaking process in any concentration and/or amount that is
desired in order to
obtain the desired retention of the fiber filler complex in the paper
substrate made therefrom.
The fiber filler complex may be contacted with the paper substrate at any
point in the
papermaking process. The contacting may occur anytime in the papermaking
process including,
but not limited to the thick stock, thin stock, head box, size press, water
box, and coater. Further
addition points include machine chest, stuff box, and suction of the fan pump.
The paper substrate of the present invention may also include optional
substances
including pigments, dyes, optical brightening agents, fillers not in the form
of a fiber-filler
24
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WO 2006/019808 PCT/US2005/024837
complex, retention aids, sizing agents (e.g. AKD and ASA), binders,
thickeners, and
preservatives. Examples of binders include, but are not limited to, polyvinyl
alcohol, Amres (a
Kymene type), Bayer Parez, polychloride emulsion, modified starch such as
hydroxyethyl starch,
starch, polyacrylamide, modified polyacrylamide, polyol, polyol carbonyl
adduct,
ethanediaUpolyol condensate, polyamide, epichlorohydrin, glyoxal, glyoxal
urea, ethanedial,
aliphatic polyisocyanate, isocyanate, 1,6 hexamethylene diisocyanate,
diisocyanate,
polyisocyanate, polyester, polyester resin, polyacrylate, polyacrylate resin,
acrylate, and
methacrylate. Other optional substances include, but are not limited to
silicas such as colloids
and/or sols. Examples of silicas include, but are not limited to, sodium
silicate andlor
borosilicates. Another example of optional substances is solvents including
but not limited to
water.
The paper substrate of the present invention may contain retention aids
selected from the
group consisting of coagulation agents, flocculation agents, and entrapment
agents dispersed
within the bulk and porosity enhancing additives cellulosic fibers.
The paper substrate of the present invention may contain from 0.001 to 50 wt%
of the
optional substances based on the total weight of the substrate, preferably
from 0.01 to 10 wt %,
most preferably 0.1 to 5.0wt lo, of each of at least one of the optional
substances. This range
includes 0.001, 0.002, 0.005, 0.006, 0.008, 0.01, 0.02, 0.03, 0.04, 0.05, 0.1,
0.2, 0.4, 0.5, 0.6, 0.7,
0.8, 0.9, 1, 2, 4, 5, 6, 8, 10, 12, 14, 15, 16, 18, 20, 22, 25, 30, 35, 40, 45
and 50wt6/0 based on the
total weight of the substrate, including any and all ranges and subranges
therein.
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The optional substances may be dispersed throughout the cross section of the
paper
substrate or may be more concentrated within the interior of the cross section
of the paper
substrate. Further, other optional substances such as binders for example may
be concentrated
more highly towards the outer surfaces of the cross section of the paper
substrate.
The paper substrate of the present invention may also contain a surface sizing
agent such
as starch and/or modified and/or functional equivalents thereof at a wt% of
from 0.05wt% to
50wt%, preferably from 5 to 15 wt% based on the total weight of the substrate.
The wt% of
starch contained by the substrate may be 0.05, 0.1, 0.2, 0.4, 0.5, 0.6, 0.7,
0.8, 0.9, 1, 2, 4, 5, 6, 8,
10, 12, 14, 15, 16, 18, 20, 22, 25, 30, 35, 40, 45 and 20wt lo based on the
total weight of the
substrate, including any and all ranges and subranges therein. Examples of
modified starches
include, for example, oxidized, cationic, ethylated, hydroethoxylated, etc.
Examples of functional
equivalents are, but not limited to, polyvinyl alcohol, polyvinylamine,
alginate, carboxymethyl
cellulose, etc.
The paper substrate may be pressed in a press section containing one or more
nips. However, any
pressing means commonly known in the art of papermaking may be utilized. The
nips may be,
but is not limited to, single felted, double felted, roll, and extended nip in
the presses. However,
any nip commonly known in the art of papermaking may be utilized.
The paper substrate may be dried in a drying section. Any drying means
commonly
known in the art of papermaking may be utilized. The drying section may
include and contain a
drying can, cylinder drying, Condebelt drying, IR, or other drying means and
mechanisms known
in the art. The paper substrate may be dried so as to contain any selected
amount of water.
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WO 2006/019808 PCT/US2005/024837
Preferably, the substrate is dried to contain less than or equal to 10% water.
The paper substrate may be passed through a size press, where any sizing means
commonly known in the art of papermaking is acceptable. The size press, for
example, may be a
puddle mode size press (e.g. inclined, vertical, horizontal) or metered size
press ( e.g. blade
metered, rod metered). At the size press, sizing agents such as binders may be
contacted with the
substrate. Optionally these same sizing agents may be added at the wet end of
the papermaking
process as needed. After sizing, the paper substrate may or may not be dried
again according to
the above-mentioned exemplified means and other commonly known drying means in
the art of
papermaking. The paper substrate may be dried so as to contain any selected
amount of water.
Preferably, the substrate is dried to contain less than or equal to 10% water.
The paper substrate may be calendered by any commonly known calendaring means
in the
art of papermaking. More specifically, one could utilize, for example, wet
stack calendering, dry
stack calendering, steel nip calendaring, hot soft calendaring or extended nip
calendering, etc.
While not wishing to be bound by theory, it is thought that the presence of
the expandable
microspheres and/or composition and/or particle of the present invention may
reduce and
alleviate requirements for harsh calendaring means and environments for
certain paper substrates,
dependent on the intended use thereof.
The paper substrate may be microfinished according to any microfinishing means
commonly known in the art of papermaking. Microfinishing is a means involving
frictional
processes to finish surfaces of the paper substrate. The paper substrate may
be microfinished
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with or without a calendering means applied thereto consecutively and/or
simultaneously.
Examples of microfinishing means can be found in United States Published
Patent Application
20040123966 and references cited therein, which are all hereby, in their
entirety, herein
incorporated by reference.
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.
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EXAMPLES
Example 1
Two paper substrate handsheet sets were made containing varying amounts of
ash.
Handsheet Set 1 contained SaveAll fiber fines with high surface area, while
the other Handsheet
Set 2 contained unrefined fibers. Figures 1 and 2 show a plot of the Sheffield
smoothness, in
Sheffield Units (SU), of the ID and NS sides, respectively, of the paper
substrates versus the wt%
ash contained in that paper substrate. There is a smoother surface at equal
ash content for the
paper substrates containing the unrefined pulp than those paper substrates
containing highly
refined and/or recycled and/or SaveAll pulp at the same ash content.
Example 2
A SaveAll fiber fine sample was collected from a mill stream and contained a
fluorescence that contributed 46 CIE-Whiteness points. When this sample was
mixed with
Ca(OH)Z and then reacted with CO2 to form CaCO3 to form a fiber- CaCO3
complex, the sample
contributed 23 CIE-Whiteness points, a decrease of 23 CIE-Whiteness points.
This decrease in
residual OBA efficiency is attributable to quenching of the residual OBA in
SaveAll pulp because
of the pH increase to > 12 when the Ca(OH)2 is added. The table of Figure 3
further
demonstrates fluorescent data, as measured by CIE-Whiteness, SaveAll fiber
fines pulp to the
same pulp after forming a fiber- CaCO3 complex. The addition of Ca(OH)2 to the
fibers caused
the pH to increase above 12 and, as the data shows in Figure 3, caused the
residual OBA to
become less efficient.
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Example, 3, The JEP studies that were targeted for characterizing the fiber-
filler complex that is
needed to meet the JDA goal (see Figure-2) will be summarized in this section.
JEP-3: The goal of this study was to identify the best shape and size (i.e.,
morphology)
of the PCC to be attached in a fiber-filler complex in order to maximize bulk
and sheet
strength. SMI's 4G process was used to produce these samples, with the goal of
producing fiber-filler complexes with the-PCC component matching the new SMI
"3G"
products (e.g., Megafil-4000, UltraBulk-11, Albacar-SP, etc.). Figure-4
summaries the
physical test properties of the samples and corripares them relative to the
Saillat
Megafil-2000 (aka, Megafil-S) control sample. As shown in this figure, the
UltraBulk-II
composite had the best bulk and stiffness opportunity while also reducing the
demand
for AKD sizing and OBA, relative to Megafil-S. Unfortunately, due to the
nature of the
"4G" process, which involved pre-carbonating the PCC to > 90% conversion
before
adding fiber, very low attachments of the PCC to the fiber were observed with
these
samples (see Table-6). As shown, in Table-6, the attachment of the UltraBulk-
11
composite was less than half that of the Carthago tube reactor sample. JEP-4
study
began looking at ways to improve the attachment of the PCC to the fiber but
most of the
advances in this area were done in studies JEP 7-8, which were done in
parallel with
JEP-7 being done at SMRC's lab and JEP-8 being done in the Easton pilot plant.
JEP-7: The goal of JEP-7 was to explore process variables that impacted the
attachment of PCC to fiber, not being concerned with morphology for the
present. The
samples of JEP-7 were produced using the IP tube located at SMI's Easton pilot
plant
and the results are summarized in Table-7 and Figure-5. As shown in Table-7
and
Figure-5, various cubic-shaped products were obtained during this study. These
large
cubic PCC structures gave better sizing and OBA performance than the Megafil-S
control used but also gave slightly lower opacity. The project team believes
that this
optical deficiency can be overcome with the targeted filler increase. As a
result of this
study, two process changes were instituted to improve attachment and to try to
guide
morphology towards the large cubes. These changes are:
(1) Pregasing of the fiber with CO2 before lime addition. This process. change
appears
to have the effect of improving attachment of the PCC to the fiber.
(2) Performing inline mixing of lime and fiber rather than pre-mixing them
before
carbonation. This process change appears to direct PCC morphology to a greater
tendancy towards cubes.
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WO 2006/019808 PCT/US2005/024837
Summary of JEP-3 products, showing particle size (APS), surface area (SSA),
and %o attachment.
(MP"(TAPS SSA /aAttach.
MEGAFIL 4000 3.5-pm 2.7-m2/g 9%
MEGAFIL XL 6.4 1.6
ULTRABULK I( 4.0 4.3 19
ALBACAR SP 4.3 3.0= - 7 Q
Semi-Discrete Aragonite 2.8 7.7 17 ~
.
Tube Reactor (R=I) 1.1 7.6 ~..41
Xss0,
----------------------------------------------------------------------__---_---
--_-_----___~-__-_----~___
MEGAFiL 2000 PCC 2.3-pm 5.1-_m2/g 8%
(standard Saiilat filler, is NOT a composite)
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Table-7. Summary of JEP-7 products, showing % attachment, morphology
characterization, and carbonating conditions. Note, even though no specific
morphology
was targeted, large cubic PCC often resulted from the process conditions used.
=
Furthermore, these large cubes were attached well to the fiber. Also in this
study it was
noted that pre-gassing (i.e., pre-carbonating) the fiber resulted in a greater
tendency for
large cubic PCC.
SAMPLE PRODUCT ATTACHMENT REACTOR FIBER SCALE OF
NUMBER and SIZE (%} CONDITION REACTION
4799-61.4 Cubes 43 % CSTR and NOT Pre- Pilot Plant
2 - 5 pm Tube Carbonated
Pre-
4799-63.1 I C2 5e~m 54 CSTR Carb nated Pilot Plant
4799-79.2 1 CZ SeNm 61 Tube Carbonated Pilot Plant
4799-80.1 0 5 ub3e~m 66 CSTR CarboPre- nated Pilot Plant
4799-81 1 Cubes 28 ? CSTR NOT Pre- Pilot Plant
1.5 - 2.5 pm Carbonated
Cubes 54 CSTR and Pre-
4847-143 Lab
1 - 2 pm Tube Carbonated
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JEP-8: The goal of JEP-8, which was performed in parallel with JEP-7, was to
improve
upon the attachment of the UltraBulk-II morphology identified in study JEP-3.
This work
was performed in SMRC using a lab CSTR reactor system. In this study, over
fifty
experiments were performed testing a range of parameters in an effort to
obtain good
attachment of the PCC to the fiber while still maintaining the UltraBulk-II
morphology
identified in study JEP-3. Some of the parameters evaluated include: degree of
pre-
conversion of PCC before adding fiber, chemical additives, temperature,
pressure,
reactor type, fiber source, pre-gassing fiber, using various types of seed
crystals, etc. ln
the end, it was concluded that:
(1) Fiber is needed to be present from the start of the reaction in order to
achieve good
attachment of PCC to the fiber. If the lime was pre-carbonated before adding
fiber, it
either resulted in poor morphology if the degree of pre-conversion was too low
(e.g., <
50%) or resulted in poor attachment if the degree of pre-conversion was too
high.
(2) When fiber is present from the start of carbonation, morphology control
becomes
very difficult. In fact, the team was unable to obtain any structure similar
to an UltraBulk-
II PCC when fiber was present at the start of carbonation. As was in study JEP-
7, many
of the JEP-8 samples resulted in cubic PCC structures, so it was decided that
the team
should target and evaluate the cubic fiber-filler complex structures (JEP-9).
Table-8 and Figure-6 summarize the products and specifications of the JEP-7
products.
The handsheet performance of the JEP-7 cubicr samples was similar to the cubic
samples from JEP-7, in being better performers in terms of AKD and OBA demand,
poorer performers optically, and slightly better in bulk (1-3% better).
Table-B. Summary of JEP-7 products, showing attachment and morphology of the
fiber-
filler complex, in addition to some process conditions used for its
production.
SAMPLE PRODUCT IATTACHMENT REACTOR FIBER
NUMBER and SIZE (%) CONDITION
4847-23 Amorphous 59.7 CSTR NOT Pre-
+ Cubes Carbonated
4847-59 Cubes 46 7 Tube and Pre-Carbonated
0.5-1 Nm 2CSTRs
4847-27.2* Aragonite 43.3 CSTR NOT Pre-
1.5 - 2 pm 97% preconverted Carbonated
4847-94 C Scalenohedral 30.0 Tube NOT Pre-
Carbonated
4847-167.4B Aragonite 53.6 2 CSTRs NOT Pre-
4 m 97% preconverted Carbonated
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JEP-9: The objective of study JEP-9 was to confirm the performance of cubic
fiber-filler
composite structures in handsheet paper. The results of JEP-9 were presented
to the
IP-SMI Executive Committees and the Saillat mill in March 2004. Figure-7 shows
the
cubic structures from the JEP-9 study. The DSF handsheet results of the JEP-9
study
arP ci immarized in Fiqures 8-14.
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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.
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.
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
