U.S. patent application number 15/171679 was filed with the patent office on 2016-09-22 for method for improving strength and retention, and paper product.
The applicant listed for this patent is UPM-Kymmene Corporation. Invention is credited to Markus KORHONEN, Janne LAINE, Juha MERTA.
Application Number | 20160273165 15/171679 |
Document ID | / |
Family ID | 56923880 |
Filed Date | 2016-09-22 |
United States Patent
Application |
20160273165 |
Kind Code |
A1 |
LAINE; Janne ; et
al. |
September 22, 2016 |
METHOD FOR IMPROVING STRENGTH AND RETENTION, AND PAPER PRODUCT
Abstract
A method for improving strength and retention in the manufacture
of paper includes providing a composition containing
microfibrillated cellulose in a fiber suspension, and from 0.1 to
10 w-% of microfibrillated cellulose by mass of the fiber
suspension is added to improve the strength and retention of the
product to be formed. A corresponding paper product is also
provided.
Inventors: |
LAINE; Janne; (Espoo,
FI) ; KORHONEN; Markus; (Espoo, FI) ; MERTA;
Juha; (Vantaa, FI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UPM-Kymmene Corporation |
Helsinki |
|
FI |
|
|
Family ID: |
56923880 |
Appl. No.: |
15/171679 |
Filed: |
June 2, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13980088 |
Jul 17, 2013 |
9399838 |
|
|
PCT/FI2012/050045 |
Jan 19, 2012 |
|
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15171679 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D21H 21/18 20130101;
D21H 11/18 20130101; D21H 17/25 20130101; D21H 21/52 20130101; D21H
11/20 20130101 |
International
Class: |
D21H 11/20 20060101
D21H011/20; D21H 11/18 20060101 D21H011/18 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 20, 2011 |
FI |
20115054 |
Claims
1. A method for producing a product in papermaking comprising:
adding a composition comprising anionically modified
microfibrillated cellulose to a fiber suspension at a concentration
of 0.1 to 10 wt-% anionically modified microfibrillated cellulose
by weight of the fiber suspension to produce a modified fiber
suspension; and forming the product from the modified fiber
suspension, wherein adding the anionically modified
microfibrillated cellulose to the fiber suspension improves the
strength of the product.
2. The method of claim 1, wherein anionically modified
microfibrillated cellulose is prepared by modifying and
fibrillating cellulose or microfibril bundles comprising
microfibrils.
3. The method of claim 1, wherein anionically modified
microfibrillated cellulose is anionically modified nanofibrillated
cellulose.
4. The method of claim 1 comprising adding 0.1 to 2 wt-% of the
anionically modified microfibrillated cellulose to the fiber
suspension.
5. The method of claim 1 comprising adding about 1 wt-% of the
anionically modified microfibrillated cellulose to the fiber
suspension.
6. The method of claim 1, wherein adding the anionically modified
microfibrillated cellulose to the fiber suspension improves
retention of the product.
7. The method of claim 1, wherein the fiber suspension comprises
fiber based pulp formed by a chemical method, a fiber based pulp
formed by a mechanical method, or a combination thereof.
9. The method of claim 1 further comprising adding one or more
fillers to the fiber suspension.
10. The method of claim 9, wherein the one or more fillers
comprises a cationic filler added to the fiber suspension before
adding the anionically modified microfibrillated cellulose.
11. The method of claim 1, wherein the composition further
comprises a fiber-based solid material.
12. The method of claim 1, wherein the fiber suspension comprises
fines.
13. The method of claim 1 comprising adding a cationic
polyelectrolyte to the composition.
14. The method of claim 1 comprising adding about 0.1 to about 2
wt-% of a cationic starch to the fiber suspension.
15. The method of claim 1 comprising adding an anionic
polyelectrolyte to the composition.
16. The method of claim 1 comprising adding inorganic nano- and/or
microparticles to the composition.
17. The method of claim 1, wherein adding the composition to the
fiber suspension improves bonding strength SB of the product.
18. The method of claim 1, wherein adding the composition to the
fiber suspension improves tensile strength of the product.
19. The method of claim 1, wherein the product is paper.
20. The method of claim 1, wherein the product is a product
containing anionically modified microfibrillated cellulose.
21. A method for manufacturing a modified fiber suspension, the
method comprising adding a composition containing anionically
modified microfibrillated cellulose to a fiber suspension at a
concentration of 0.1 to 10 wt-% anionically modified
microfibrillated cellulose by weight of the fiber suspension to
produce a modified fiber suspension, wherein adding the anionically
modified microfibrillated cellulose to the fiber suspension
improves the strength of the product.
Description
[0001] This application is a Continuation-in-Part of U.S. Ser. No.
13/980,088, filed 17 Jul. 2013, which is a National Stage
Application of PCT/FI2012/050045, filed 19 Jan. 2012, which claims
benefit of Ser. No. 20/115,054, filed 20 Jan. 2011 in Finland and
which applications are incorporated herein by reference. To the
extent appropriate, a claim of priority is made to each of the
above disclosed applications.
FIELD
[0002] The invention relates to a method of making paper products,
and to paper products with improved strength and/or retention.
BACKGROUND
[0003] Known from the prior art are different methods for
manufacturing paper pulp and paper products. In addition, it is
known from the prior art to improve the properties of paper
products by different filler and coating materials, e.g. pigments,
in connection with papermaking. It is known that the aim in
papermaking is to provide the best properties possible for the
paper product.
[0004] Retention and strength problems are known form papermaking.
The strength, particularly dry strength, of the product to be
formed is an important property of the product which is typically
tried to be improved. In addition, the retention of small
particles, such as fillers and fines, is important in papermaking.
Retention means the ratio of the fiber and filler material
remaining on the wire to the material that has been fed, i.e. it
means the ability of the wire to retain fiber pulp. Know are
different retention agents for improving retention. The retention
agents provide suitable fixation of the fibers, fillers and other
chemicals of the fiber pulp to the web. Known retention agents
include e.g. polyacrylamides and combined retention agents, such as
combinations of anionic and cationic retention agents. In addition,
it is known to use a combination of polyacrylamide and
microparticles as a retention agent.
[0005] On the other hand, it is known from the prior art to
manufacture microfibrillated cellulose and use it in the
manufacture of paper pulp and paper products. In studies on
microfibrillated cellulose, it has been found that microfibrillated
cellulose improves the strength of paper, i.a. Microfibrillated
cellulose has a large specific surface area and has thus more
bonding area relative to material weight.
OBJECTIVE
[0006] The objective of the invention is to disclose a new type of
a method for improving strength as well as retention in
papermaking, and a corresponding paper product.
SUMMARY
[0007] The method and the corresponding paper product according to
the invention are characterized by what has been presented in the
claims.
[0008] The invention is based on a method for improving strength
and retention in papermaking. According to the invention, a
composition containing microfibrillated cellulose is provided in a
fiber suspension, preferably paper pulp, and from 0.1 to 10 w-% of
microfibrillated cellulose by mass of the fiber suspension is added
to improve the strength, e.g. dry strength, tensile strength of dry
paper, internal bond strength and/or initial wet strength, and
retention of the product to be formed.
[0009] Fiber suspension in this context means any suspension of
fiber-based pulp containing a fiber-based composition that may be
formed from any plant-based raw material, e.g. wood-based raw
material, such as hardwood raw material or softwood raw material,
or other plant raw material containing fibers, such as cellulose
fibers. The fiber suspension may be fiber-based pulp formed by a
chemical method wherein the fibers have been separated from each
other and most of the lignin has been removed by chemicals using a
chemical method that may be e.g. a sulfate process, sulfite
process, soda process, a process based on organic solvents or other
chemical treatment method known per se in the art. Alternatively,
the fiber suspension may be fiber-based pulp formed by a mechanical
method, for example TMP, PGW, CTMP or the like.
[0010] In one embodiment, the composition containing
microfibrillated cellulose may be in the form of a dispersion, e.g.
in a gel-type or gelatinous form or in the form of a diluted
dispersion, or in the form of a suspension, e.g. aqueous
suspension. Preferably, the composition containing microfibrillated
cellulose is in the form of an aqueous suspension. The composition
may contain from more than 0% to less than 100 w-% of
microfibrillated cellulose. In one embodiment, the composition may
consist mainly of microfibrillated cellulose. In addition to
microfibrillated cellulose, the composition may contain other
suitable components, e.g. fibers that may be formed from any
plant-based raw material, and/or different additives and/or
fillers.
[0011] Microfibrillated cellulose in this context means cellulose
consisting of microfibrils, i.e. a set of isolated cellulose
microfibrils and/or microfibril bundles derived from a cellulose
raw material. Cellulose fibers contain microfibrils that are
strand-like structural components of the cellulose fibers. The
cellulose fiber is provided fibrous by fibrillating. The aspect
ratio of microfibrils is typically high; the length of individual
microfibrils may be more than one micrometer and the number-average
diameter is typically less than 20 nm. The diameter of microfibril
bundles may be larger but generally less than 1 .mu.m. The smallest
microfibrils are similar to the so-called elementary fibrils, the
diameter of which is typically from 2 to 4 nm. The dimensions and
structures of microfibrils and microfibril bundles depend on the
raw material and production method.
[0012] Microfibrillated cellulose may have been formed from any
plant-based raw material, e.g. wood-based raw material, such as
hardwood raw material or softwood raw material, or other
plant-based raw material containing cellulose. Plant-based raw
materials may include e.g. agricultural waste, grasses, straw,
bark, caryopses, peels, flowers, vegetables, cotton, maize, wheat,
oat, rye, barley, rice, flax, hemp, abaca, sisal, kenaf, jute,
ramie, bagasse, bamboo or reed or their different combinations.
[0013] Microfibrillated cellulose may also contain hemicellulose,
lignin and/or extractives, the amount of which depends on the raw
material used. Microfibrillated cellulose is isolated from the
above-described raw material containing cellulose by an apparatus
suitable for the purpose, e.g. a grinder, pulverizer, homogenizer,
fluidizer, micro- or macrofluidizer, cryo-crushing and/or
ultrasonic disintegrator. Microfibrillated cellulose may also be
obtained directly by a fermentation process using microorganisms
e.g. from the genera Acetobacter, Agrobacterium, Rhizobium,
Pseudomonas or Alcailgenes, most preferably from the genera
Acetobacter and most preferably of all from the species Acetobacter
xylinum or Acetobacter pasteurianus. Raw materials of
microfibrillated cellulose may also include for example the
tunicates (Latin: tunicata) and organisms belonging to the
chromalveolate groups (Latin: chromalveolata), e.g. the water molds
(Latin: oomycete), that produce cellulose.
[0014] In one embodiment, microfibrillated cellulose may be any
chemically or physically modified derivative of cellulose or
microfibril bundles consisting of microfibrils. The chemical
modification may be based on e.g. a carboxymethylation, oxidation,
esterification and etherification reaction of the cellulose
molecules. The modification may also be carried out by physical
adsorption of anionic, cationic or non-ionic agents or their
combinations to the surface of cellulose. The modification may be
performed before, during or after the manufacture of
microfibrillated cellulose.
[0015] Microfibrillated cellulose may be formed from a
cellulose-based raw material by any manner known per se in the art.
In one embodiment, microfibrillated cellulose is formed from a
dried and/or concentrated cellulose raw material by fibrillating.
In one embodiment, the cellulose raw material has been
concentrated. In one embodiment, the cellulose raw material has
been dried. In one embodiment, the cellulose raw material has been
dried and concentrated. In one embodiment, the cellulose raw
material has been chemically pretreated to disintegrate more
easily, i.e. labilized, in which case microfibrillated cellulose is
formed from the chemically labilized cellulose raw material. For
example, a N-oxyl (e.g. 2,2,6,6-tetramethyl-1-piperidine
N-oxide)-mediated oxidation reaction provides a very labile
cellulose raw material that is exceptionally easily disintegrated
into microfibrillated cellulose. Such a chemical pretreatment is
described for example in patent applications WO 09/084566 and JP
20070340371.
[0016] The fibrils of microfibrillated cellulose are fibers that
are very long relative to the diameter. Microfibrillated cellulose
has a large specific surface area. Therefore, microfibrillated
cellulose is able to form multiple bonds and bind many particles.
In addition, microfibrillated cellulose has good strength
properties.
[0017] In one embodiment, microfibrillated cellulose is at least
partially or mainly nanocellulose. Nanocellulose consists at least
mainly of nano-size class fibrils, the diameter of which is less
than 100 nm but the length of which may also be in the .mu.m-size
class or below. Alternatively, microfibrillated cellulose may also
be referred to as nanofibrillated cellulose, nanofibril cellulose,
nanofibers of cellulose, nanoscale fibrillated cellulose,
microfibril cellulose or microfibrils of cellulose. Preferably,
microfibrillated cellulose in this context does not mean so-called
cellulose nanowhiskers or microcrystalline cellulose (MCC).
[0018] In one embodiment of the invention, a composition containing
cationic microfibrillated cellulose is added to the fiber
suspension.
[0019] In one embodiment of the invention, a composition containing
anionic microfibrillated cellulose is added to the fiber
suspension.
[0020] In one embodiment of the invention, the composition contains
a component containing microfibrillated cellulose, and a filler,
e.g. PCC.
[0021] In one embodiment of the invention, the composition contains
a component containing microfibrillated cellulose, and a
fiber-based solid material, e.g. fines.
[0022] In one embodiment, the composition contains an additive,
e.g. an AKD sizing agent, ASA sizing agent or corresponding
additives.
[0023] In one embodiment of the invention, the component containing
microfibrillated cellulose in the composition is anionic. In one
embodiment, the component containing microfibrillated cellulose is
anionic and the filler is cationic.
[0024] In one embodiment of the invention, the component containing
microfibrillated cellulose in the composition is cationic. In one
embodiment, the component containing microfibrillated cellulose is
cationic and the filler is anionic.
[0025] In one embodiment of the invention, a composition containing
anionic and/or cationic microfibrillated cellulose is added to the
fiber suspension including a filler. In one embodiment, a
composition containing anionic microfibrillated cellulose is added
to the fiber suspension including as a filler a cationic filler,
e.g. PCC.
[0026] In one embodiment of the invention, a composition containing
anionic and/or cationic microfibrillated cellulose is added to the
fiber suspension including fines, in one embodiment fiber-based
fines.
[0027] In one embodiment, a composition containing anionic and/or
cationic microfibrillated cellulose is added to the fiber
suspension including an additive.
[0028] In one embodiment, a composition containing anionic and/or
cationic microfibrillated cellulose is added to the fiber
suspension including a filler, fines and/or an additive.
[0029] In one embodiment of the invention, a cationic
polyelectrolyte is added to the composition containing
microfibrillated cellulose.
[0030] In one embodiment of the invention, an anionic
polyelectrolyte is added to the composition containing
microfibrillated cellulose.
[0031] In one embodiment of the invention, inorganic nano- and/or
microparticles, e.g. SiO.sub.2 particles, are added to the
composition containing microfibrillated cellulose. In one
embodiment, inorganic nano- and/or microparticles are added to the
composition containing cationic microfibrillated cellulose. In one
embodiment, a polyelectrolyte and inorganic nano- and/or
microparticles are added to the composition containing
microfibrillated cellulose.
[0032] In one embodiment of the invention, from 1 to 5 w-%, in one
preferred embodiment from 1 to 3 w-%, of microfibrillated cellulose
by mass of the fiber suspension is added to the fiber
suspension.
[0033] In one embodiment of the invention, at least part of the
retention chemicals and/or strength chemicals is replaced by the
composition containing microfibrillated cellulose. In one
embodiment, part of the conventional retention chemicals and/or
strength chemicals is replaced by the composition containing
microfibrillated cellulose. In one embodiment, the conventional
retention chemicals and/or strength chemicals are entirely replaced
by the composition containing microfibrillated cellulose. In one
embodiment wherein the conventional retention chemicals are
entirely replaced, a composition containing both cationic
microfibrillated cellulose and anionic microfibrillated cellulose
is used. In one embodiment, one of the components, e.g. a polymer
component or microparticle component, is replaced in a 2-component
retention arrangement. In one embodiment wherein a polymer
component is replaced, a composition containing cationic
microfibrillated cellulose is used. In one embodiment wherein a
microparticle component is replaced, a composition containing
anionic microfibrillated cellulose is used. In one embodiment, at
least one component in a multicomponent retention arrangement is
replaced.
[0034] In one embodiment of the invention, the method is used in
the manufacture of a fiber suspension containing microfibrillated
cellulose. In one embodiment of the invention, the method is used
in the manufacture of paper pulp.
[0035] In one embodiment of the invention, the method is used in
papermaking. The method according to the invention can be applied
for use in the manufacture of different paper products wherein the
paper product is formed from the fiber-based composition. A paper
product in this context means any fiber-based paper, board or fiber
product or an equivalent product. The paper product may have been
formed from chemical pulp, mechanical pulp, chemimechanical pulp,
recycled pulp, fiber pulp and/or plant-based pulp. The paper
product may contain suitable fillers and additives as well as
different surface treatment and coating agents.
[0036] In one embodiment of the invention, the method is used in
the manufacture of a product containing microfibrillated cellulose,
e.g. in the manufacture of different compositions and mixtures,
preferably in the manufacture of precipitated compositions and
mixtures, in the manufacture of different films, in the manufacture
of different composite products or in equivalent cases. In one
embodiment, the method is mainly used in the manufacture of a
product containing microfibrillated cellulose, such as in the
manufacture of a precipitated microfibril cellulose suspension or
in the manufacture of films formed from microfibrillated
cellulose.
[0037] In addition, the invention is based on a corresponding paper
product formed from the fiber-based composition. According to the
invention, the paper product contains microfibrillated cellulose
such that a composition containing microfibrillated cellulose has
been added to a fiber suspension, containing the fiber-based
composition, in an amount of from 0.1 to 10 w-% by mass of the
fiber suspension, and the paper product has an improved retention
and strength.
[0038] The invention provides considerable advantages relative to
the prior art.
[0039] Thanks to the invention, the retention and strength in a
paper product containing microfibrillated cellulose can be
improved. The retention of the filler or retention of the additive
or retention of the entire fiber suspension can be influenced by
the solution according to the invention.
[0040] Thanks to the invention, the quality of the paper product to
be formed can be improved and additionally the raw material and
energy expenditures can be reduced.
[0041] The method according to the invention is easily industrially
applicable.
[0042] In addition, the invention provides for a new method of use
for microfibrillated cellulose.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] FIG. 1A is a graphical representation of drainage time as a
function of NFC dosage according to Example 3.
[0044] FIG. 1B is a graphical representation of retention as a
function of NFC dosage according to Example 3.
[0045] FIG. 1C is a graphical representation of grammage as a
function of NFC dosage according to Example 3.
[0046] FIG. 1D is a graphical representation of apparent bulk
density as a function of NFC dosage according to Example 3.
[0047] FIG. 1E is a graphical representation of tensile index as a
function of NFC dosage according to Example 3.
[0048] FIG. 1F is a graphical representation of bonding strength as
a function of NFC dosage according to Example 3.
[0049] FIG. 1G is a graphical representation of air permeance as a
function of NFC dosage according to Example 3.
[0050] FIG. 2A is a graphical representation of drainage time as a
function of NFC dosage according to Example 4.
[0051] FIG. 2B is a graphical representation of retention as a
function of NFC dosage according to Example 4.
[0052] FIG. 2C is a graphical representation of grammage as a
function of NFC dosage according to Example 4.
[0053] FIG. 2D is a graphical representation of apparent bulk
density as a function of NFC dosage according to Example 4.
[0054] FIG. 2E is a graphical representation of tensile index as a
function of NFC dosage according to Example 4.
[0055] FIG. 2F is a graphical representation of bonding strength as
a function of NFC dosage according to Example 4.
[0056] FIG. 2G is a graphical representation of air permeance as a
function of NFC dosage according to Example 4.
DETAILED DESCRIPTION
[0057] According to at least some embodiments, the method comprises
adding a composition comprising anionically modified
nanofibrillated cellulose ("anionic NFC") to a fiber suspension to
produce a modified fiber suspension, and preparing a paper product
from the modified fiber suspension. The anionic NFC can be added to
the fiber suspension at a concentration of about 0.1 to about 10
wt-% (on a dry weight basis), about 0.1 to about 5 wt-%, about 0.2
to about 2 wt-%, or about 0.4 to about 1 wt-%. In some embodiments
the anionic NFC is added at a concentration of about 1 wt-%.
[0058] The method may further include adding native (chemically
unmodified) nanofibrillated cellulose ("native NFC"), a starch
addition (e.g., cationic starch), retention aids (e.g., cationic
polyacrylamide), and fillers to the fiber suspension or modified
fiber suspension. Cationic starch may be added at any suitable
concentration, such as 0 to about 10 wt-% (on a dry weight basis),
about 0.1 to about 5 wt-%, or about 0.5 to about 2 wt-%. In some
embodiments the cationic starch is added at a concentration of
about 1 wt-%.
[0059] The fiber suspension may include a suspension of any
fiber-based pulp formed from a plant-based raw material, e.g.
wood-based raw material, such as hardwood raw material or softwood
raw material, or other plant raw material containing fibers, such
as cellulose fibers. The fiber suspension may comprise a chemical
pulp or a mechanical pulp.
[0060] The additives and their amounts added to the fiber
suspension to produce a modified fiber suspension can be selected
based on a desired end result. For example, the additives and their
amounts can be selected to increase or reduce drainage time; to
increase retention; to increase the tensile index; to increase
boding strength; and/or to increase or reduce permeability of the
resulting paper product.
[0061] The invention will be described in more detail by the
accompanying examples.
EXAMPLE 1
[0062] The retention of a fiber suspension containing PCC was
studied. Nanocellulose was added to the fiber suspension. The fiber
suspension was the pulp to be used for the manufacture of a paper
product.
[0063] Anionic nanocellulose was used to bind cationic particles,
such as precipitated calcium carbonate (PCC), in order to increase
the retention of fines in the fiber suspension. 3 w-% of anionic
nanocellulose was added to the fiber suspension containing 20 w-%
of precipitated calcium carbonate (PCC). Sheets were formed from
the fiber suspension. The retention was determined for the obtained
sheet to which nanocellulose had been added. As a reference, the
retention was also determined for a sheet formed from a fiber
suspension containing 20 w-% of precipitated calcium carbonate
(PCC) but no nanocellulose. In addition, the wet strengths were
determined for the sheets.
[0064] It was found that the retention of the filler, i.e. PCC,
could be significantly improved by the solution according to the
invention. The retention was improved from 62% to 84%. In addition,
it was found that the dry strength of the product was improved. It
was discovered that the effect was provided by virtue of the
physical and chemical properties of nanocellulose. Due to the wide
specific surface area of nanocellulose and high aspect ratio of the
microfibrils, nanocellulose formed a network structure within the
product composition already at very diluted aqueous suspensions,
which improved both strength and retention. It was found that
anionic nanocellulose flocked cationic PCC, whereby it is more
effectively retained by the fibers.
[0065] In addition, the effect of the amount of addition of
nanocellulose on the retention was studied. It was found that as
the amount of nanocellulose increased from 1 w-% to 3 w-% in the
fiber suspension including 20 w-% of precipitated calcium
carbonate, the retention of precipitated calcium carbonate
increased from 75% to 82%. In addition, it was found that as the
amount of nanocellulose increased from 3 w-% to 6 w-%, the
retention of precipitated calcium carbonate slightly increased
further, yet not significantly.
EXAMPLE 2
[0066] The effect of addition of cationic nanocellulose on the dry
strength of a product was studied using the tensile index. 20, 30
and 45 mg/g of cationic nanocellulose were added to fiber pulp 1
including a small amount of fines (10 min. grinding) and to fiber
pulp 2 including more fines (30 min. grinding). Sheets were formed
from the fiber pulps and the strengths were determined. Pine
chemical pulp was used as the fiber pulp.
[0067] It was found that the strength of the sheet formed from
fiber pulp 1 was lower than the strength of the product formed from
a reference composition including 10 mg/g of cationic starch and
20, 30 and 45 mg/g of anionic nanocellulose. In addition, it was
found that the strength of the sheet formed from fiber pulp 2 was
clearly better that the strength of the sheet formed from fiber
pulp 1. Thus, the effect of cationic nanocellulose on the strength
was clearly higher, which was due to the fact that cationic
nanocellulose retained the fines, whereby the strength of the sheet
was improved. On this basis, starch can be replaced by
nanocellulose for a strengthening purpose.
EXAMPLE 3
[0068] The effect of microfibrillated cellulose, i.e.,
nanofibrillated cellulose (NFC), on the properties of the resulting
paper product was tested. Nanofibrillated cellulose was added at
0.2 to 1.0% by weight (2 to 10 kg/t). All amounts are given on a
dry-weight basis. The effect of anionically treated nanofibrillated
cellulose was compared with native chemically unmodified
nanofibrillated cellulose.
[0069] Canadian Standard Freeness (CSF) level of pulp describes the
degree of beating/refining of the pulp and is a measure of drainage
resistance. The unit of CSF is mL, and higher values indicate
slower filtration and thus higher degree of beating/refining. The
term "beating" is used with regard to chemical pulp, and the term
"refining" is used with regard to mechanical pulp.
[0070] Raw Materials: [0071] Chemical pulp: Kaukas Pinus produced
by Kaukas pulp mill, beaten to Canadian Standard Freeness (CSF)
level of 605 mL. [0072] Mechanical pulp: Pressure ground wood (PGW)
from Kaukas paper mill, CSF level 67 mL. [0073] Modified
nanofibrillated cellulose ("Anionic NFC"): UPM Biofibrils AS83, lot
11851, supplied as a gel with solids content 2.52% by weight,
available from UPM Kymmene Corp. in Helsinki, Finland. The Anionic
NFC was modified to result in a surface charge that was more
anionic than unmodified NFC. [0074] Native chemically unmodified
nanofibrillated cellulose ("Native NFC"): UPM Biofibrils NS 11246,
supplied as a gel with solids content 1.5% by weight, available
from UPM Kymmene Corp. in Helsinki, Finland [0075] Reference
("REF"): without nanofibrillated cellulose [0076] Retention aid:
cationic polyacrylamide (FENNOPOL 3400R, available from Kemira Oyj
in Helsinki, Finland) [0077] Water (osmotically purified) [0078] No
filler was used
[0079] Method:
[0080] 1. Dilution and activation of nanofibrillated cellulose:
[0081] A. Anionic NFC and Native NFC were each diluted to 0.3%
solids with water. [0082] B. The diluted NFC compositions were
mixed with an immersion mixer (BAMIX), carried out in three 10 s
mixing periods.
[0083] 2. Preparation of samples: [0084] A. Mechanical pulp and
chemical pulp were mixed at a ratio of 3:1 (mechanical pulp to
chemical pulp). [0085] B. To each sample, either Anionic NFC or
Native NFC was added according to TABLE 1. [0086] C. The samples
were mixed for 5 minutes. [0087] D. Retention aid was added to the
samples at 50 g/t immediately prior to sheet making.
[0088] 3. Sheets were prepared from each sample using a circulation
sheet mold.
[0089] 4. Sheets were dried using gloss plates and air conditioned
before measurements.
TABLE-US-00001 TABLE 1 NFC Dosage. Sample NFC Type NFC Dose (kg/t)
1 (REF) None 0 2 Anionic NFC 2 3 Anionic NFC 6 4 Anionic NFC 10 5
Native NFC 2 6 Native NFC 6 7 Native NFC 10
[0090] The sheets were evaluated for various properties, including
drainage time, grammage (weight per area), bulking thickness, bulk
density, tensile strength, stretch at break, tensile energy
absorption (TEA), TEA index, tensile stiffness, tensile stiffness
index, breaking length, bonding strength (Scott Bond), air
permeability (measured by the Bendtsen method), and retention.
Retention was determined by measuring weight of material going in
to each sheet mold vs. the weight of sheet. Results are shown in
TABLE 2 and FIGS. 1A-1G.
TABLE-US-00002 TABLE 2 Results. SAMPLE 1 (REF) 2 3 4 5 6 7 NFC dose
(%) 0 0.2 0.6 1 0.2 0.6 1 NFC type None Anionic Anionic Anionic
Native Native Native Drainage time (s) 17.8 19.5 19.1 20.1 18.8
20.1 20.9 Grammage (g/m.sup.2) 60.9 61.0 61.1 60.8 60.7 60.8 60.4
Bulking thickness (.mu.m) 115 116 114 113 116 115 114 Apparent bulk
density 532 527 537 539 523 527 528 (kg/m.sup.3) Tensile strength
(kN/m) 2.62 2.72 2.77 2.79 2.69 2.75 2.77 Tensile index (Nm/g) 43.1
44.6 45.3 45.9 44.3 45.2 45.9 Stretch at break (%) 2.3 2.4 2.2 2.3
2.4 2.3 2.4 TEA (J/m.sup.2) 41 45 43 45 44 44 46 TEA index (J/kg)
670 740 700 744 730 720 762 Tensile stiffness (kN/m) 302 308 315
308 307 308 311 Tensile stiffness index 5.0 5.1 5.2 5.1 5.1 5.1 5.2
(MNm/kg) Breaking length (m) 4395 4549 4619 4680 4517 4609 4682
Bonding strength, SB 298 301 311 322 298 308 308 Low (J/m.sup.2)
Air permeability, 131 134 125 124 150 128 119 Bendtsen (ml/min)
Retention (%) 96.1 95.4 95.6 96.8 95.0 96.3 96.5
[0091] It was observed that addition of NFC (either anionic or
native) increased the drainage time. In case of higher dosage
amounts, anionic NFC has had slightly lower drainage time than
native NFC. Drainage time as a function of NFC dosage is shown in
FIG. 1A.
[0092] Only marginal differences in absolute retention values were
seen. Retention with low NFC dosage was slightly below reference,
and slightly above with high NFC dosage. Retention as a function of
NFC dosage is shown in FIG. 1B.
[0093] The sheets containing native NFC had generally slightly
lower grammage than sheets containing anionic NFC. However, the
differences in grammage were not great. Grammage as a function of
NFC dosage is shown in FIG. 1C.
[0094] It was observed that density did not vary greatly from one
sample to the next. Sheets containing anionic NFC had slightly
higher density than native NFC containing sheets. The reference had
higher density than sheets having the lowest NFC content and the
samples containing native NFC. Bulk density as a function of NFC
dosage is shown in FIG. 1D.
[0095] It was observed that NFC increased tensile above reference
at all dosage levels. Tensile increased as a function of NFC dosage
amount. Tensile index as a function of NFC dosage is shown in FIG.
1E.
[0096] NFC addition increased Scott Bond level of the samples.
Anionic NFC had a higher effect on Scott Bond than native NFC.
Bonding strength as a function of NFC dosage is shown in FIG.
1F.
[0097] NFC addition was found to decreased porosity (air
permeability) of the samples except at 0.2% NFC dosage. Air
permeability as a function of NFC dosage is shown in FIG. 1G.
[0098] The primary effect of NFC was seen as increased strength
properties and to some extent as lower porosity. Drainage time
increased as NFC was added to furnish. Results were favorable for
anionic NFC when compared to native NFC.
EXAMPLE 4
[0099] The effect of nanofibrillated cellulose (NFC) with and
without cationic starch on selected paper properties and retention
was tested at NFC dosage levels ranging from 0.1 to 1% (1 to 10
kg/t). All amounts are given on a dry-weight basis.
[0100] Raw Materials: [0101] Chemical pulp: Kaukas Pinus produced
by Kaukas pulp mill, beaten to Canadian Standard Freeness (CSF)
level of 605 mL. [0102] Mechanical pulp: Pressure ground wood (PGW)
from Kaukas paper mill, refined to CSF level 71 mL. [0103] Modified
nanofibrillated cellulose ("Anionic NFC"): UPM Biofibrils AS83, lot
11851, supplied as a gel with solids content 2.52% by weight,
available from UPM Kymmene Corp. in Helsinki, Finland. The Anionic
NFC was modified to result in a surface charge that was more
anionic than unmodified NFC. [0104] Reference ("REF"): without
nanofibrillated cellulose. [0105] Cationic starch: RAISAMYL 70021,
dry solids content 0.040%, available from Chemigate, Finland.
[0106] Retention aid: cationic polyacrylamide (FENNOPOL 3400R).
[0107] Water (osmotically purified) [0108] No filler was used
[0109] Method:
[0110] 1. Dilution and activation of nanofibrillated cellulose:
[0111] A. Anionic NFC was diluted to 0.3% solids with water. [0112]
B. The diluted NFC composition was mixed with an immersion mixer
(BAMIX), carried out in three 10 s mixing periods.
[0113] 2. Preparation of samples: [0114] A. Mechanical pulp and
chemical pulp were mixed at a ratio of 3:1 (mechanical pulp to
chemical pulp). [0115] B. Cationic starch was added to the samples
according to TABLE 3. [0116] C. Samples were mixed for 15 minutes
after addition of starch. [0117] D. Anionic NFC was added to the
samples according to TABLE 3. [0118] E. The samples were mixed for
5 minutes. [0119] F. Retention aid was added to the samples at 50
g/t immediately prior to sheet making.
[0120] 3. Sheets were prepared from each sample using a circulation
sheet mold.
[0121] 4. Sheets were dried using gloss plates and air conditioned
before measurements.
TABLE-US-00003 TABLE 3 NFC Dosage. Sample NFC Dose (kg/t) Cationic
Starch (kg/t) 1 0 0 2 1 0 3 4 0 4 7 0 5 10 0 6 0 10 7 1 10 8 4 10 9
7 10 10 10 10
[0122] The sheets were evaluated for various properties, including
drainage time, grammage (weight per area), bulking thickness, bulk
density, tensile strength, stretch at break, tensile energy
absorption (TEA), TEA index, tensile stiffness, tensile stiffness
index, breaking length, bonding strength (Scott Bond), air
permeability (measured by the Bendtsen method), and retention.
Retention was determined by measuring weight of material going in
to each sheet mold vs. the weight of sheet. Results are shown in
TABLE 4 and FIGS. 2A-2G.
TABLE-US-00004 TABLE 4 Results. SAMPLE 1 2 3 4 5 6 7 8 9 10 Starch
dose (kg/t) 0 0 0 0 0 10 10 10 10 10 NFC does (%) 0 0.1 0.4 0.7 1 0
0.1 0.4 0.7 1 Drainage time (s) 14.5 13.8 14.4 14.6 14.5 12.1 11.8
12.8 12.7 12.9 Grammage (g/m.sup.2) 60.6 61.0 60.7 60.9 60.6 61.0
61.1 59.8 60.2 60.1 Bulking thickness 116 117 117 115 114 112 114
114 114 114 (.mu.m) Apparent bulk 523 523 521 531 532 543 538 526
530 528 density (kg/m.sup.3) Tensile strength 2.51 2.63 2.67 2.72
2.78 2.95 2.93 2.69 2.89 3.05 (kN/m) Tensile index 41.5 43.1 44.0
44.6 45.9 48.3 47.9 45.0 48.0 50.7 (Nm/g) Stretch at break (%) 2.39
2.36 2.36 2.38 2.51 2.62 2.57 2.50 2.51 2.60 TEA (J/m.sup.2) 42 43
44 45 49 53 51 46 50 54 TEA index (J/kg) 690 705 720 737 806 865
835 771 827 905 Tensile stiffness 284 298 302 306 308 298 292 281
301 313 (kN/m) Tensile stiffness 4.68 4.89 4.97 5.02 5.08 4.89 4.78
4.70 5.00 5.21 index (MNm/kg) Breaking length (m) 4229 4395 4487
4551 4685 4927 4883 4586 4899 5175 Bonding strength 308 310 311 327
344 449 443 432 423 429 SB Low (J/m.sup.2) Air permeability 138 140
137 129 128 137 135 150 145 144 Bendtsen (mL/min) Retention (%)
96.3 98.0 97.1 97.7 97.9 98.2 96.5 97.2 97.1 98.8
[0123] It was observed that adding cationic starch to the samples
reduced drainage time. The effect of NFC was visible with lowest
dosage amount. Higher NFC amount either had not effect or increased
drainage time slightly. Drainage time as a function of NFC dosage
is shown in FIG. 2A.
[0124] NFC addition increased retention above the reference at all
dosage levels when no starch was added. The reference (sample 1)
had retention 96.3%, and retention with NFC addition was 98.0% at
dosage level 0.1% NFC (sample 2), 97.1% at dosage level 0.4% NFC
(sample 3), 97.7% at dosage level 0.7% NFC (sample 4) and 97.9% at
dosage level 1.0% NFC (sample 5). The retention increased about
0.8-1.7%-units compared with the reference. In case of sheets
containing starch, the reference with starch (but no NFC) had high
retention. The retention dropped at the lowest NFC addition, and
then increased as a function of NFC, rising to above the reference
at 1% NFC addition. Retention as a function of NFC dosage is shown
in FIG. 2B.
[0125] Sheets with cationic starch had slightly lower grammage than
sheets without starch. However, no major differences were observed
in grammage. Grammage as a function of NFC dosage is shown in FIG.
2C.
[0126] The differences in bulk density were very small in samples
with and without starch. Bulk density as a function of NFC dosage
is shown in FIG. 2D.
[0127] It was observed that NFC addition increased tensile above
the reference at all dosage levels for samples without starch.
Addition of starch generally increased general the tensile level,
but the changes in tensile were not very systematic. Tensile index
as a function of NFC dosage is shown in FIG. 2E.
[0128] NFC addition increased bonding (Scott Bond) above the
reference at all dosage levels for samples without starch. Starch
generally increased the Scott Bond level. Bonding strength as a
function of NFC dosage is shown in FIG. 2F.
[0129] NFC was found to reduce porosity for samples without starch.
In case of sheets containing starch, the effect of NFC was not very
systematic. Air permeability as a function of NFC dosage is shown
in FIG. 2G.
[0130] It was concluded that the effect of Anionic NFC on the
sheets without starch were consistent. Improved retention, tensile
strength, Scott bond and lowered porosity were obtained with
Anionic NFC addition. Based on the results obtained, Anionic NFC
was found to have an effect on paper strength properties and
retention within the dosage range 0.1-1% in sheets without cationic
starch. The results for sheets with starch were not as systematic
and consistent as results without starch. At some dosage levels and
for some parameters, the benefits were clear, whereas at some other
dosage levels and for some other parameters, the benefits could not
be shown as clearly.
[0131] The method according to the invention is suitable in
different applications to be used for manufacturing most different
products.
[0132] The invention is not limited merely to the examples referred
to above; instead, many variations are possible within the scope of
the inventive idea defined by the claims.
* * * * *