U.S. patent application number 14/104068 was filed with the patent office on 2014-08-07 for modified filler composition and papermaking process using the same.
This patent application is currently assigned to Goldeast Paper (Jiangsu) Co., Ltd. The applicant listed for this patent is Goldeast Paper (Jiangsu) Co., Ltd. Invention is credited to YAN FENG, XIANG-FEI LIU, PENG ZHAO.
Application Number | 20140216672 14/104068 |
Document ID | / |
Family ID | 51236860 |
Filed Date | 2014-08-07 |
United States Patent
Application |
20140216672 |
Kind Code |
A1 |
FENG; YAN ; et al. |
August 7, 2014 |
MODIFIED FILLER COMPOSITION AND PAPERMAKING PROCESS USING THE
SAME
Abstract
A modified filler composition used in papermaking is provided.
The modified filler composition contains microfibrillated
cellulose, filler, and latex having a glass transition temperature
of less than 20.degree. C. The dry weight of the microfibrillated
cellulose is about 0.1% to about 10% that of the filler; the dry
weight of the latex is about 0.1% to about 15% that of the
filler.
Inventors: |
FENG; YAN; (Zhenjiang,
AU) ; ZHAO; PENG; (Zhenjiang, CN) ; LIU;
XIANG-FEI; (Zhenjiang, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Goldeast Paper (Jiangsu) Co., Ltd |
Zhenjiang |
|
CN |
|
|
Assignee: |
Goldeast Paper (Jiangsu) Co.,
Ltd
Zhenjiang
CN
|
Family ID: |
51236860 |
Appl. No.: |
14/104068 |
Filed: |
December 12, 2013 |
Current U.S.
Class: |
162/169 ;
524/35 |
Current CPC
Class: |
D21H 11/18 20130101;
D21H 17/69 20130101 |
Class at
Publication: |
162/169 ;
524/35 |
International
Class: |
D21H 17/00 20060101
D21H017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 5, 2013 |
CN |
201310045150X |
Claims
1. A modified filler composition, comprising: microfibrillated
cellulose, filler, and latex having a glass transition temperature
of less than 20.degree. C., wherein the dry weight of the
microfibrillated cellulose is about 0.1% to about 10% of that of
the filler, the dry weight of the latex is about 0.1% to about 15%
of that of the filler.
2. The modified filler composition as claimed in claim 1, wherein
the microfibrillated cellulose has negative charge and comprises
carboxyl groups, the content of carboxyl groups of the
microfibrillated cellulose is in the range from about 0.06 to about
1.7 mmol/g.
3. The modified filler composition as claimed in claim 2, wherein
the microfibrillated cellulose comprises water-soluble cellulose
having a mass percentage of about 0.1% to about 50% and
water-insoluble cellulose having a mass percentage of about 10% to
about 99.9%.
4. The modified filler composition as claimed in claim 3, wherein
the water-soluble celluloses comprises nanocrystalline cellulose,
nanofibrillated cellulose, and oligosaccharide.
5. The modified filler composition as claimed in claim 1, wherein
the latex has a glass transition temperature of less than
10.degree. C.
6. The modified filler composition as claimed in claim 1, wherein
the latex is selected from the group consisting of polybutadiene
latex, styrene-butadiene latex, carboxylic butadiene-styrene latex,
cationic butadiene-styrene latex, polyvinyl acetate latex, and any
combination thereof.
7. The modified filler composition as claimed in claim 1, wherein
the filler adsorbing on the surface of the microfibrillated
cellulose has a size uniformity of less than 10.
8. The modified filler composition as claimed in claim 1, wherein
more than 50% of the filler has a particle diameter of less than or
equal to 2 .mu.m.
9. The modified filler composition as claimed in claim 1, wherein
the modified filler composition further comprises a cross-linking
agent.
10. The modified filler composition as claimed in claim 9, wherein
the cross-linking agent is borate, borax, glutaric dialdehyde, or
oxaldehyde; the dry weight of the cross-linking agent is about 0.1%
to about 15% of that of the latex.
11. A papermaking process, comprising: providing a modified filler
composition, the modified filler composition comprising
microfibrillated cellulose, filler, and latex having a glass
transition temperature of less than 20.degree. C., the dry weight
of the microfibrillated cellulose being about 0.1% to about 10% of
that of the filler, the dry weight of the latex being about 0.1% to
about 15% of that of the filler. providing a paper pulp; adding the
modified filler composition into the paper pulp; employing the
paper pulp to make paper.
12. The papermaking process as claimed in claim 11, wherein the
modified filler composition is prepared by mixing the
microfibrillated cellulose, filler, and latex together.
13. The papermaking process as claimed in claim 11, wherein the
process further comprises a step of adding unmodified filler to the
paper pulp prior to employing the paper pulp to make paper.
14. The papermaking process as claimed in claim 13, wherein the
total weight of the filler in the modified filler composition and
the unmodified filler in paper pulp is about 10% to about 300% of
the dry weight of the pulp fiber, the weight of filler in the
modified filler composition is about 80% to about 100% of the total
weight of the filler in the modified filler composition and the
unmodified filler.
15. The papermaking process as claimed in claim 11, wherein the
microfibrillated cellulose has negative charge and comprises
carboxyl groups, the content of carboxyl groups of the
microfibrillated cellulose is in the range from about 0.06 to about
1.7 mmol/g.
16. The papermaking process as claimed in claim 11, wherein the
microfibrillated cellulose comprises water-soluble cellulose having
a mass percentage of about 0.1% to about 50% and water-insoluble
cellulose having a mass percentage of about 10% to about 99.9%, the
water-soluble celluloses comprises nanocrystalline cellulose,
nanofibrillated cellulose, and oligosaccharide.
17. The papermaking process as claimed in claim 11, wherein the
latex has a glass transition temperature of less than 10.degree.
C.
18. The papermaking process as claimed in claim 11, wherein the
latex is selected from the group consisting of polybutadiene latex,
styrene-butadiene latex, carboxylic butadiene-styrene latex,
cationic butadiene-styrene latex, polyvinyl acetate latex, and any
combination thereof.
19. The papermaking process as claimed in claim 11, wherein the
filler adsorbed on the surface of the microfibrillated cellulose
has a size uniformity of less than 10.
20. The papermaking process as claimed in claim 11, wherein more
than 50% of the filler has a particle diameter of less than or
equal to 2 .mu.m.
21. The papermaking process as claimed in claim 11, wherein the
modified filler composition further comprises a cross-linking
agent, the cross-linking agent is borate, borax, glutaric
dialdehyde, or oxaldehyde; the weight of the cross-linking agent is
0.1% to 15% of that of the latex.
22. The papermaking process as claimed in claim 11, wherein the
process further comprises a step of adding auxiliary additive to
the paper pulp prior to employing the paper pulp to make paper.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of priority to People's
Republic of China Patent Application No. 201310045150.X, filed Feb.
5, 2013, which is hereby incorporated by reference herein in its
entirety.
BACKGROUND
[0002] 1. Technical Field
[0003] The present disclosure relates to a modified filler
composition used in the field of papermaking, and a papermaking
process using the modified filler composition.
[0004] 2. Description of Related Art
[0005] Microfibrillated cellulose is cellulose microfibrils
defibrillated from cellulosic materials by mechanical methods
and/or the TEMPO catalytic oxidation method. The microfibrillated
cellulose contains water-soluble cellulose and water-insoluble
cellulose. The microfibrillated cellulose has dimensions of about
100 nm to about several millimeters in length, and about 3 nm to
tens of micrometers in diameter. Due to a large number of carboxyl
groups of the microfibrillated cellulose, high aspect ratio, and
good flexibility, the microfibrillated cellulose made by the TEMPO
catalytic oxidation method is generally added into paper pulp to
improve the strength properties of the paper made using the
same.
[0006] In the field of papermaking, adding filler to the paper pulp
can effectively lower down the cost. However, if both filler and
microfibrillated cellulose were added into the paper pulp, the
filler would inhibit the hydrogen bonding of the microfibrillated
cellulose. In addition, the negatively charged microfibrillated
cellulose would repel the negatively charged or neutral filler,
causing the finer filler particles to easily aggregate. Therefore,
adding both filler and microfibrillated cellulose to the paper pulp
leads to a non-uniform distribution of filler particles on the
microfibrillated cellulose, thus decreasing the filler
retention.
[0007] Therefore, there is room for improvement within the art.
BRIEF DESCRIPTION OF THE FIGURE
[0008] Many aspects of the disclosure can be better understood with
reference to the following drawing. The components in the drawing
are not necessarily drawn to scale, the emphasis instead being
placed upon clearly illustrating the disclosure.
[0009] FIG. 1 is a scanning electron micrograph of a modified
filler composition of Example 1.
[0010] FIG. 2 is a scanning electron micrograph of a filler
composition of Comparative Example 1.
DETAILED DESCRIPTION
[0011] The microfibrillated cellulose used in this disclosure is
made by the TEMPO catalytic oxidation method.
[0012] One example for preparing the microfibrillated cellulose by
the TEMPO catalytic oxidation method may include the following
steps: (1) providing bleached kraft pulp (BKP) and beating the
pulp; (2) providing the beaten pulp having an amount by dry weight
of 100 parts, and adjusting the concentration of the beaten pulp to
about 2%; (3) adding a catalyst having an amount by dry weight of
about 0.001 part to about 1 part to the above pulp, the catalyst
being TEMPO ((2,2,6,6-Tetramethylpiperidin-1-yl)oxyl) or a
derivative of TEMPO; (4) adding an assistant catalyst having an
amount by dry weight of about 0.01 part to about 10 parts into the
pulp, the assistant catalyst consisting of iodides, bromides,
borates, or a mixture thereof; (4) adding an oxidant (sodium
hypochlorite) having an amount by dry weight of about 0.1 part to
about 20 parts into the pulp and stirring, keeping the pH value of
the pulp to be in a range from about 9.5 to about 11; (5) the pulp
and the oxidant reacting for about 0.5 hours to 4 hours to obtain a
mixture containing oxidized celluloses, TEMPO, catalyst, and water;
(6) removing the residual catalyst and TEMPO from the mixture; (7)
mechanically treating the oxidized celluloses by ultrasonication or
high-pressure homogenization.
[0013] During the reaction process of the cellulose and the
oxidant, some hydroxyl groups (--OH) on the chains of glucose of
the cellulose are selectively oxidized to carboxyl groups (--COOH),
which have stronger negative charges than the hydroxyl groups.
Thus, the oxidized cellulose molecules easily delaminate and
defibrillate cellulose microfibrils due to the strong electrostatic
repulsion in the cellulose molecules.
[0014] The microfibrillated cellulose made by the TEMPO catalytic
oxidation method has strong negative charge due to the carboxyl
groups. The content of the carboxyl groups of the microfibrillated
cellulose is in the range from about 0.06 to about 1.7 mmol/g. The
microfibrillated cellulose has a complex composition, which
substantially contains both water-soluble cellulose and
water-insoluble cellulose. The water-soluble cellulose further
contains nanocrystalline cellulose (NCC), nanofibrillated cellulose
(NFC), and oligosaccharides, for example. The water-soluble
cellulose (such as NFC) may position on the cell wall of the
water-insoluble cellulose.
[0015] The modified filler composition in this disclosure contains
microfibrillated cellulose and latex, wherein the dry weight of the
microfibrillated cellulose in the modified filler composition is
about 0.1% to about 10% that of the filler, and the dry weight of
the latex in the modified filler composition is about 0.1% to about
15% that of the filler. The modified filler composition may further
contain water.
[0016] The microfibrillated cellulose in the modified filler
composition is made by the TEMPO catalytic oxidation method. The
content of carboxyl groups of the microfibrillated cellulose is in
the range from about 0.06 to about 1.7 mmol/g. The microfibrillated
cellulose contains water-soluble cellulose having a mass percentage
of 0.1% to 50% and water-insoluble cellulose having a mass
percentage of 10% to 99.9%.
[0017] The filler is composed of ground calcium carbonate (GCC),
precipitated calcium carbonate (PCC), kaolin, talc, or any
combination thereof. In this embodiment, more than 50% of the
filler has a particle diameter less than or equal to 2 .mu.m.
[0018] The latex has a glass transition temperature (T.sub.g) of
less than 20.degree. C. In one embodiment, the T.sub.g of the latex
is less than 10.degree. C. The latex is an emulsion, and the latex
is consisted of polybutadiene latex, styrene-butadiene latex,
carboxylic butadiene-styrene latex, cationic butadiene-styrene
latex, polyvinyl acetate latex, or any combination thereof.
[0019] The latex in the modified filler composition makes the
filler particles distribute uniformly on the surface of the
microfibrillated cellulose. A possible mechanism for this is
illustrated as following: (1) the ambient temperature of the
modified filler composition is higher than the T.sub.g of the
latex, so the latex becomes unstable and demulsifies; (2) the
filler particles have a large specific surface area, so easily
adsorb the demulsified latex; (3) thus, carbon-carbon double bonds
(--[C.dbd.C]--) of latex distribute on surfaces of the filler
particles. Carbon-carbon double bonds easily react with
microfibrillated cellulose. Therefore, the latex is equivalent to a
binder or a media for coupling the microfibrillated cellulose and
the filler together.
[0020] The modified filler composition may further contain a
cross-linking agent. The cross-linking agent is a borate
cross-linking agent, a borax cross-linking agent, or dialdehyde
cross-linking agent (such as oxaldehyde or glutaric dialdehyde).
The dry weight of the cross-linking agent is about 0.1% to about
15% that of the latex. The cross-linking agent promotes the
cross-linking between the latex and the microfibrillated cellulose
to form a network structure, which is beneficial for increasing the
filler retention on the microfibrillated cellulose.
[0021] The modified filler composition can be made by directly
mixing the filler, the microfibrillated cellulose, and the latex
together. During the mixing process, the temperature of the
composition is maintained in a range from 20.degree. C. to
110.degree. C. In this embodiment, the temperature of the
composition is kept in a range from 20.degree. C. to 70.degree. C.
In other embodiments, the temperature of the composition is kept in
a range from 30.degree. C. to 50.degree. C.
[0022] One example for preparing the modified filler composition
may include the following steps: (1) providing a filler suspension;
(2) adding the microfibrillated cellulose into the filler
suspension to obtain a mixture, the dry weight of the
microfibrillated cellulose being about 0.1% to about 10% that of
the filler; (3) adding the latex into the above mixture, the dry
weight of the latex being about 0.1% to about 15% that of the
filler; (4) stirring the mixture with a speed of about 800
revolutions per minute (RPM) for about 5 min between about
20.degree. C. to about 110.degree. C.
[0023] The filler adsorbing on the surface of the microfibrillated
cellulose has a particle size uniformity of less than 10. The
particle size uniformity is calculated by dividing the standard
deviation of the particle diameter by the mean particle size.
[0024] A papermaking process using the above modified filler
composition includes the following steps.
[0025] Step 1: providing a paper pulp.
[0026] Step 2: adding the above modified filler composition into
the paper pulp, and selectively adding or not adding unmodified
filler to the paper pulp.
[0027] Thus, the filler in the paper pulp is either all from the
modified filler composition, or is a combination of the modified
filler composition and the unmodified filler. The total weight of
the filler added into the paper pulp is 10% to 300% of the dry
weight of the pulp fiber. The weight of filler from the modified
filler composition is 80% to 100% of the total weight of the filler
in the paper pulp. The microfibrillated cellulose from the modified
filler composition is a portion of the pulp fiber.
[0028] Step 3: adding at least one auxiliary additive into the
paper pulp.
[0029] The auxiliary additive may contain starch, retention aids,
or the like. The starch is consisted of anionic starch, oxidized
starch, grafted starch, amphoteric starch, or any combination
thereof. The retention aids are either one-component retention aids
or three-component retention aids. For example, the nanocrystalline
cellulose (NCC) and/or the microfibrillated cellulose can be used
as an anionic retention aid.
[0030] Step 4: employing the paper pulp to make paper.
[0031] Paper made by the above papermaking process has an ash
retention of about 60% to about 95%, and a first-pass ash retention
of about 55% to about 90%. Note: conventional paper has an ash
retention of about 45% to about 90%, and a first-pass ash retention
of about 40% to about 85%.
[0032] The paper made by the above papermaking process has a high
ash retention. The reason may include one or more of the
following:
[0033] (1) The microfibrillated cellulose made by the TEMPO
catalytic oxidation method has a complex composition and contains
both water-soluble cellulose and water-insoluble cellulose. The
water-insoluble cellulose has many carboxyl groups, causing it to
delaminate due to the electrostatic repulsion. Thus, the fine
filler particles and latex particles easily incorporate into the
inside of the water-insoluble celluloses.
[0034] (2) The temperature of the modified filler composition is
higher than T.sub.g of the latex, so the latex demulsify; the
demulsified latex acts as a binder or a media for coupling the
microfibrillated cellulose and the filler together.
[0035] (3) Some of the water-soluble cellulose adsorbs the filler
particles, which improves the dispersion ability of the filler, so
the filler disperses uniformly in the modified filler composition.
In case that the modified filler composition is kept static in a
container for about 4 hours, there will be no or few filler
particles at the bottom of the container.
[0036] (4) The surface of the filler particles adsorbs some of the
water-soluble cellulose, improving the chemical reactivity of the
filler. Thus, the filler with reactive functional groups chemically
bonds with the pulp fiber.
[0037] The disclosure provides a modified filler composition
containing latex, the latex having a low glass transition
temperature. The latex acts as a binder for coupling the
microfibrillated cellulose and filler together, which makes the
filler particles uniformly distribute on the surface of the
microfibrillated cellulose. The paper pulp added with the modified
filler composition has a high filler retention. Thus, paper made by
the paper pulp has a high ash retention.
EXAMPLE 1
[0038] In this embodiment, the modified filler composition was
prepared by the following steps: (a) providing a microfibrillated
cellulose aqueous dispersion containing 2 g of microfibrillated
cellulose by dry weight; (b) adding 20 g of filler (GCC) to the
microfibrillated cellulose aqueous dispersion, more than 95% of the
filler by weight having a particle size of less than 2 .mu.m; (c)
adding 0.2 g of styrene-butadiene latex having a T.sub.g of about
10.degree. C. to the microfibrillated cellulose aqueous dispersion
to obtain a mixture; (d) stirring the mixture at a temperature of
about 50.degree. C. for about 5 minutes, thereby making the
modified filler composition. A scanning electron micrograph of the
modified filler composition is shown in FIG. 1.
COMPARATIVE EXAMPLE 1
[0039] A comparative filler composition was made by mixing
microfibrillated cellulose and filler together by stirring at about
600 RPM for about 5 minutes, wherein the weight of the filler is 10
times the dry weight of the microfibrillated cellulose. The filler
is uniformly dispersed GCC, and more than 95% of the filler by
weight has a particle size of less than 2 .mu.m. A scanning
electron micrograph of the comparative filler composition is shown
in FIG. 2.
[0040] FIG. 2 shows obvious aggregation of the filler particles on
the surface of the microfibrillated cellulose, while FIG. 1 shows
that the filler particles distribute much more uniformly on the
microfibrillated cellulose, with little aggregation.
[0041] The fillers in Example 1 and Comparative Example 1 were
tested, and the test results are listed in Table 1 below. The test
results demonstrate that the filler in Example 1 has a much more
uniform particle size. Note: the particle size uniformity is a
value calculated by dividing the standard deviation of the particle
diameter by the mean particle size.
TABLE-US-00001 TABLE 1 Test type Comparative Example 1 Example 1
particle size uniformity of 11.9 7.42 filler Average particle size
of 4.5 .mu.m 3.9 .mu.m filler
EXAMPLE 2
[0042] The above modified filler composition in Example 1
containing 2 g of microfibrillated cellulose and 20 g of filler was
added into a Leaf Bleached Kraft Pulp (LBKP) having a dry weight of
about 10 g; 2 g of starch was added into the above pulp; the pulp
was diluted and employed to make paper.
COMPARATIVE EXAMPLE 2
[0043] 20 g of filler were added into a LBKP having a dry weight of
about 10 g; 2 g of starch were added into the above pulp; the pulp
was diluted and employed to make comparative paper.
[0044] The papers made in Example 2 and Comparative Example 2 were
tested, and the test results are listed in Table 2 below. The test
results show that the ash retention and the first-pass ash
retention of the paper in Example 2 are much higher than those of
the paper in Comparative Example 2.
TABLE-US-00002 TABLE 2 Test type Comparative Example 2 Example 2
Basis weight g/m.sup.2 72.3 73.1 Thickness .mu.m 94.7 85.7 Paper
bulk cc/g 1.31 1.17 Air permeability s 10.5 33.5 Fold endurance
test, number 3 4 of folds (1.0 kg) Bursting index kPa m.sup.2/g
0.84 0.99 Tensile index N m/g 17.4 21.8 Cohesion kg cm 0.53 0.99
Ash content % 45.74 51.4 First-pass ash retention % 42.1 63.3 ash
retention 68.7 82.2
EXAMPLE 3
[0045] In this embodiment, the modified filler composition was
prepared by the following steps: (a) providing a filler suspension
containing 2 g of filler (calcium carbonate) by weight; (b) adding
microfibrillated cellulose having a dry weight of 0.002 g into the
filler suspension; (c) adding 0.002 g of styrene-butadiene latex
having a T.sub.g of less than 10.degree. C. into the filler
suspension to obtain a mixture; (d) stirring the mixture at a
temperature of about 50.degree. C. for about 5 minutes, thereby
making the modified filler composition.
[0046] A mixed pulp containing 10 g of Needle Bleached Kraft Pulp
(NBKP) by dry weight and 10 g of alkaline peroxide mechanical pulp
(APMP) by dry weight was provided. The above modified filler
composition in Example 3 was added into the mixed pulp; 0.08 g of
starch was added into the above mixed pulp; the mixed pulp was
diluted to a concentration of about 0.3% and employed to make
paper.
COMPARATIVE EXAMPLE 3
[0047] A mixed pulp containing 10 g of NBKP by dry weight and 10 g
of APMP by dry weight was provided and adjusted to a concentration
of about 4%. Then, 2 g of filler (calcium carbonate) and 0.08 g of
cationic starch was added into the mixed pulp; the mixed pulp was
diluted to a concentration of about 0.3% and employed to make
comparative paper.
EXAMPLE 4
[0048] In this embodiment, the modified filler composition was
prepared by the following steps: (a) providing a filler suspension
containing 5 g of filler (calcium carbonate) by weight; (b) adding
microfibrillated cellulose having a dry weight of 0.005 g into the
filler suspension; (c) adding 0.005 g of styrene-butadiene latex
having a T.sub.g less than 10.degree. C., and 0.005 g of a
cross-linking agent (borax) into the filler suspension to obtain a
mixture; (d) stirring the mixture at a temperature of about
50.degree. C. for about 5 minutes, thereby making the modified
filler composition.
[0049] A mixed pulp containing 10 g of NBKP by dry weight and 10 g
of APMP by dry weight was provided and adjusted to a concentration
of about 4%. The above modified filler composition in Example 4 was
added into the mixed pulp; 0.08 g of starch was added into the
above mixed pulp; the mixed pulp was diluted to a concentration of
about 0.3% and employed to make comparative paper.
COMPARATIVE EXAMPLE 4
[0050] A mixed pulp containing 10 g of NBKP by dry weight and 10 g
of APMP by dry weight was provided and adjusted to a concentration
of about 4%. Then, 5 g of filler (calcium carbonate) and 0.08 g of
cationic starch were added into the mixed pulp; the mixed pulp was
diluted to a concentration of about 0.3% and employed to make
paper.
[0051] The papers made in examples 3, Example 4, comparative
example 3, and Comparative Example 4 were tested, and the test
results are listed in Table 3 below. Compared with the paper in
comparative example 3, the ash retention and the first-pass ash
retention of the paper in example 3 are significantly improved.
Compared with the paper in comparative example 4, the ash retention
and the first-pass ash retention of the paper in Example 4 are also
significantly improved.
TABLE-US-00003 TABLE 3 Comparative Comparative Test type Example 3
Example 3 Example 4 Example 4 Basis weight g/m.sup.2 76.1 74.7 81.5
77.6 Thickness .mu.m 184.5 179.4 184.2 190.8 Paper bulk cc/g 2.42
2.40 2.26 2.46 Air permeability s 4.1 3.5 4.1 4.0 Fold endurance
test, 59 92 40 62 number of folds (1.0 kg) Bursting index 2.38 2.53
2.22 2.28 kPa m.sup.2/g Tensile index 43.8 46.1 40.0 42.1 N m/g
Cohesion kg cm 0.97 1.02 0.85 0.92 Ash content % 3.86% 5.49% 9.94%
12.54% First-pass ash 40.1% 58.1% 55.2% 71.7% retention % ash
retention % 42.5% 60.4% 59.6% 75.2%
EXAMPLE 5
[0052] In this embodiment, the modified filler composition was
prepared by the following steps: (a) providing a filler suspension
containing 60 g of filler (calcium carbonate) by weight; (b) adding
microfibrillated cellulose having a dry weight of 4 g into the
filler suspension; (c) adding 9 g of styrene-butadiene latex having
a T.sub.g less than 10.degree. C. into the filler suspension to
obtain a mixture; (d) stirring the mixture at a temperature of
about 50.degree. C. for about 5 minutes, thereby making the
modified filler composition.
[0053] A mixed pulp containing 10 g of NBKP by dry weight and 6 g
of APMP by dry weight was provided and adjusted to a concentration
of about 4%. The above modified filler composition in Example 5
containing 60 g of filler and 4 g of microfibrillated cellulose
were added into the mixed pulp; 0.4 g of cationic starch was added
into the above mixed pulp; the mixed pulp was diluted to a
concentration of about 1%; a three-component retention aid
containing 300 PPM cationic polyacrylamide, 3600 PPM bentonite, and
800 PPM anionic polyacrylamide was added into the mixed pulp, the
pulp being employed to make paper.
COMPARATIVE EXAMPLE 5
[0054] A mixed pulp containing 10 g of NBKP by dry weight, 6 g of
APMP by dry weight, and 4 g of microfibrillated cellulose by dry
weight was provided and adjusted to a concentration of about 4%.
Then, 60 g of filler (calcium carbonate) and 0.4 g of cationic
starch were added into the mixed pulp; the mixed pulp was diluted
to a concentration of about 1%; a three-component retention aid
containing 300 PPM cationic polyacrylamide, 3600 PPM bentonite, and
800 PPM anionic polyacrylamide was added into the mixed pulp, the
pulp being employed to make comparative paper.
[0055] The papers made in Example 5 and Comparative Examples 5 were
tested, and the test results are listed in Table 4 below. Compared
with the paper made in Comparative Example 5, the ash retention and
the first-pass ash retention of the paper in Example 5 are
significantly improved, and the number of folds, tensile index, and
cohesion of the paper made in Example 5 also improved.
TABLE-US-00004 TABLE 4 Test type Comparative Example 5 Example 5
Basis weight g/m.sup.2 107.9 112.0 Thickness .mu.m 134.9 72.0 Paper
bulk cc/g 1.25 0.64 Fold endurance test, number 2 11 of folds (1.0
kg) Air permeability s 18.9 51.4 Tensile index N m/g 7.2 16.6
Cohesion kg cm 0.64 2.25 Ash content % 59.6 62.4 First-pass ash
retention % 49.2 84.0 ash retention % 79.5 95.5
[0056] It is believed that the exemplary embodiments and their
advantages will be understood from the foregoing description, and
it will be apparent that various changes may be made thereto
without departing from the spirit and scope of the disclosure or
sacrificing all of its advantages, the examples hereinbefore
described merely being preferred or exemplary embodiments of the
disclosure.
* * * * *