Note: Descriptions are shown in the official language in which they were submitted.
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CELLULOSIC FIBRE COMPOSITION
Field of the Invention
The present invention relates to a cellulosic fibre composition, a method of
making a
cellulosic fibre composition, the use of a cellulosic fibre composition in the
production of
paper and board, a process for making a cellulosic pulp mixture in which a
cellulosic fibre
composition is used, the use of a pulp mixture for making paper and board, a
process for
producing paper and board in which a cellulosic fibre composition or pulp
mixture is used,
paper and board comprising a cellulosic fibre composition or pulp mixture and
various
uses of paper and board comprising a cellulosic fibre composition or pulp
mixture.
Background of the Invention
Strength is important to cellulosic products like paper and board, and
increasing the strength of
such products provides several benefits. For instance, increasing the strength
of paper makes
it possible to increase filler loadings and reduce virgin fibre usage, thereby
reducing raw
material costs in paper making processes. Similarly, increasing the strength
of board makes it
possible to reduce the grammage while maintaining the strength properties of
cellulosic
products made from the board, which also leads to savings in virgin fibre
usage and reduced
transportation costs, thus environmental and economic benefits.
A wide variety of additives for improving the strength of paper and board are
known in the art,
including natural and synthetic polymers, modified fillers, modified
cellulosic fibres, etc. One
example of modified cellulosic fibres is microfibrillar cellulose, which is
obtained from
cellulosic fibres that have been delaminated to small fragments with a large
proportion of
the microfibrils of the fibre walls uncovered. WO 00/47628, WO 2004/055268, WO
2007/001229 and WO 2008/076056 disclose microfibrillar cellulose, methods for
preparing
same and use of same as an additive in the production of a paper product. WO
00/47628
discloses microfibrillar cellulose comprising anionic charge which may be used
in a
papermaking machine to increase the rate of drainage and/or dewatering during
paper
manufacture and to improve strength of a sheet of paper.
However, there are still some problems associated with modified cellulosic
fibres like
microfibrillar cellulose and the use thereof in paper and board making
processes. While it
has been experienced that the use of such products as strength additives in
papermaking
processes may provide good or even improved initial drainage and/or dewatering
in the
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wet end of the paper machine, it has also been experienced that modified
cellulosic fibres
like microfibrillar cellulose may absorb and retain a substantial amount of
water. These
characteristics may lead to higher water content of the cellulosic web
entering the press
and drying sections of the machine, thereby requiring more energy to remove
the
remaining water and dry the cellulosic web and/or reducing the paper machine
speed and
productivity.
Modified cellulosic fibres like microfibrillar cellulose may also contain a
substantial amount
of fines, i.e. very small cellulosic fibres and fibre fragments. Cellulosic
fines are generally
difficult to retain in paper and board making processes, which may lead to
accumulation of
the fines in the white water that is re-circulated in the processes. These
problems may be
alleviated or solved by reducing the drainage rate, increasing the dosage of
retention aids
and/or co-using or increasing the dosage of cationic coagulants, e.g. low
molecular
weight, highly cationic, organic polymers and aluminium compounds.
Modified cellulosic fibres like microfibrillar cellulose may also be difficult
to produce, and the
methods for producing them may be complicated and provide modified cellulosic
fibres in
low yields or at low dry solids contents.
Accordingly, there is still a need of cellulosic fibre compositions which
impart high strength to
paper and board and provide improvements in the manufacture of paper and
board, in
particular in terms drainage and retention performance, drying of paper and
board, and
productivity. There is also a need of improved methods for producing
cellulosic fibre
compositions which impart high strength to paper and board.
Summary of the Invention
It is an object of the present invention to provide a cellulosic fibre
composition, preferably
a high concentration cellulosic fibre composition, which imparts high or
increased strength
to paper and board. It is another object to provide a cellulosic pulp mixture
which provides
paper and board with high or increased strength. It is another object to
provide a process
for producing paper and board which makes use of such a cellulosic fibre
composition or
cellulosic pulp mixture. By using the composition or mixture in the production
of paper and
board, e.g. in making multi ply board grades, it is possible to reduce virgin
fibre usage and
lower the grammage while maintaining the strength properties, which leads to
reduced
raw material and transportation costs and environmental and economic benefits.
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It is another object of the invention to provide a cellulosic fibre
composition and a
cellulosic pulp mixture, preferably high concentration products, which do not
absorb or
retain a substantial amount of water. By using the composition or mixture in
the production
of paper and board it is possible to maintain or increase the speed of drying
the cellulosic
web obtained when it is fed through the press section of the paper or board
making
machine. Hereby the present invention leads to improvements in paper and board
making
processes and increased productivity.
It is a further object of the invention to provide a cellulosic fibre
composition and a
cellulosic pulp mixture, preferably high concentration products, which have a
low or
reduced content of fines. By using the composition or mixture in the
production of paper
and board it is possible to reduce the amount of fines that are re-circulated
in the process.
It is also possible to reduce the amount of cationic coagulants and/or
drainage and
retention aids used in the process, and to run paper and board making machines
at higher
drainage rates without substantial impairment of the white water quality.
Hereby the
present invention leads to improvements in paper and board making processes
and
increased productivity.
It is yet another object of the invention to provide a method for the
production of a
cellulosic fibre composition, preferably a process that renders possible
production of a
cellulosic fibre composition at high productivity and/or as a high-
concentration product,
whereby concentration steps and/or transportation of dilute low-concentration
products
can be avoided and the above advantages can be achieved.
Accordingly, in one aspect, the present invention relates to a composition
comprising
cellulosic fibres having an average degree of substitution of anionic groups
of from 0.001
to 0.25, a length weighted mean fibre length up to 1,100 pm and a length
weighted mean
fibre width over 10 pm.
In another aspect, the present invention relates to a composition comprising
cellulosic
fibres having an average degree of substitution of anionic groups of from
0.001 to 0.25, a
length weighted mean fibre length up to 1,100 pm, and wherein at least 50 % by
weight of
the cellulosic material is insoluble in water.
In another aspect, the present invention relates to a composition comprising
cellulosic
fibres having an average degree of substitution of anionic groups of from
0.001 to 0.25
and a length weighted mean fibre length / width ratio up to 30.
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In another aspect, the present invention relates to a composition comprising
cellulosic
fibres having an average degree of substitution of anionic groups of from
0.001 to 0.25
and a length weighted mean fibre width over 35 pm.
In another aspect, the present invention relates to a composition comprising
cellulosic
fibres having a specific surface area of at least 1.5 m2/g, a length weighted
mean fibre
length / width ratio up to 30 and a dry solids content of at least 5 % by
weight, based on
the weight of the composition.
In another aspect, the present invention relates to a composition comprising
cellulosic
fibres having a specific surface area of at least 1.5 m2/g, a length weighted
mean fibre
length / width ratio up to 30, and up to 30 % by weight, based on the total
weight of the
cellulosic fibres, of cellulosic fibres with a length weighted mean fibre
length up to 100 pm.
In another aspect, the present invention relates to a method of producing a
composition
comprising cellulosic fibres which comprises subjecting cellulosic fibres to
chemical
treatment and mechanical treatment, wherein the chemical treatment comprises
treating
cellulosic fibres with (i) at least one agent containing a carboxyl group,
optionally
substituted, (ii) at least one oxidant and at least one transition metal, or
(iii) at least one
nitroxyl radical, and the mechanical treatment comprises subjecting cellulosic
fibres to
extrusion with a twin-screw extruder or a planetary extruder.
In another aspect, the present invention relates to a method of producing a
composition
comprising cellulosic fibres which comprises subjecting cellulosic fibres
having an average
degree of substitution of anionic groups of from 0.001 to 0.25 to extrusion.
In another aspect, the invention relates to the composition comprising
cellulosic fibres
obtainable by the methods of the invention. In another aspect, the present
invention
relates to the use of the composition comprising cellulosic fibres in the
production of paper
and board, usually as an additive and, in particular, as a strength additive.
In another aspect, the present invention relates to a process for producing a
cellulosic
pulp mixture which comprises mixing the composition comprising cellulosic
fibres with
cellulosic pulp. In another aspect, the present invention relates to the
cellulosic pulp
mixture obtainable by the process, and to the use of the cellulosic pulp
mixture in the
production of paper and board. In another aspect, the present invention
relates to a
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process for producing paper and board which comprises forming an aqueous
suspension
comprising the cellulosic pulp mixture and dewatering the obtained suspension.
In another aspect, the present invention relates to a process for producing
paper and
5 board which comprises adding the composition comprising cellulosic fibres to
an aqueous
cellulosic pulp suspension and dewatering the obtained suspension. In another
aspect,
the present invention relates to a process for producing paper and board which
comprises
mixing a composition comprising cellulosic fibres subjected to extrusion with
cellulosic
pulp.
In another aspect, the present invention relates to paper and board containing
the
composition comprising cellulosic fibres or cellulosic pulp mixture, and to
paper and board
obtainable by the processes of the invention.
In another aspect, the present invention relates to various board grades, and
to the
production thereof. In another aspect, the present invention relates to
various uses of the
paper and board, e.g. for packaging of beverages and liquid food.
These and other objects and aspects of the invention will be described in
further detail
hereinafter.
Brief Description of the Drawing
Fig. 1 is a side view of the configuration of an extruder screw.
Detailed Description of the Invention
The composition comprising cellulosic fibres of the invention, herein also
referred to as
"the cellulosic fibre composition" or "the composition", contains cellulosic
fibres which can
be derived from a wide variety of sources including wood fibres, non-wood
fibres and
mixtures thereof.
Wood fibres may be derived from hardwood and softwood, e.g. from chemical
pulps,
mechanical pulps, thermo-mechanical pulps, chemical thermo-mechanical pulps,
recycled
fibres and newsprint. Examples of suitable wood fibres include birch, beech,
aspen, e.g.
European aspen, alder, eucalyptus, maple, acacia, mixed tropical hardwood,
pine, e.g.
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loblolly pine, fir, hemlock, larch, spruce, e.g. Black spruce or Norway
spruce, and mixtures
thereof.
Non-wood fibres may be derived from seed fibres, e.g. cotton linters, seed
hull fibres, e.g.
soybean hulls, pea hulls and corn hulls, bast fibres, e.g. flax, hemp, jute,
ramie and kenaf,
leaf fibres, e.g. manila hemp and sisal hemp, stalk and straw fibres, e.g.
bagasse, corn
and wheat, grass fibres, e.g. bamboo and reed canary grass, cellulosic fibres
from algae,
e.g. velonia, bacteria and fungi, and parenchymal cells, e.g. vegetables such
as sugar
beets, and fruits, e.g. citrus fruits such as lemons, limes, oranges and
grapefruits.
The cellulosic fibres of the composition may or may not contain ionic groups.
According to
one preferred embodiment, the cellulosic fibres of the composition are free or
essentially
free from anionic groups, e.g. the cellulosic fibres of the composition have
an average
degree of substitution of anionic groups of below 0.001. According to another
preferred
embodiment, the cellulosic fibres of the composition have an average degree of
substitution of anionic groups of from 0.001, usually from about 0.01, or from
about 0.02,
up to 0.25, or up to about 0.20, usually up to about 0.15, or up to 0.10, or
up to about
0.05. At these low degrees of substation, the cellulosic fibres are preferably
dispersible in
water, but not water-soluble. The term "average degree of substitution", or
"DS" as used
herein, means the average number of anionic groups, or substituent groups, per
anhydroglucose unit of cellulose. The degree of substitution of anionic groups
can be
determined by the methods of ASTM D1439-03 and conductometric titration as
described
by S. Katz, R.P. Beatson and A.M. Scallan in Svensk Papperstidning No. 6/1984,
pp. 48-
53.
Examples of suitable anionic groups include carboxyl groups and substituted
carboxyl
groups, e.g. carboxyalkyl groups such as carboxymethyl groups. The counter-ion
of the
anionic group is usually an alkali metal or alkaline earth metal, e.g. sodium
or potassium,
suitably sodium. The carboxyl group can be illustrated by the formula -COO-
Na+, and the
carboxymethyl group by the formula -CH2OO0- Na+. Examples of suitable
cellulosic fibres
of the composition of the invention include carboxylated cellulosic fibres and
carboxyalkylated cellulosic fibres, e.g. carboxymethylated cellulosic fibres,
having a
degree of substitution as defined above.
The cellulosic fibre composition of the invention may contain both water-
soluble cellulosic
material and water-insoluble cellulosic material. In one embodiment, at least
50, or at least
70, preferably at least 80 or at least 85 % by weight of the cellulosic
material present in
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the composition is insoluble in water, measured on an aqueous cellulosic
composition
containing 1 % by weight of cellulosic material at 20 C. The water-insoluble
material is
usually swellable and dispersible in water.
The cellulosic fibres of the composition of the invention may have a specific
surface area of
at least 1.5, or at least about 2, usually at least about 3 m2/g, and the
specific surface area
may be up to about 150, usually up to about 50, up to about 15, or up to about
10 m2/g. The
specific surface area is determined by adsorption of N2 at 177 K according to
the BET method
using a Micromeritics TriStar 3000 instrument, which operates according to ISO
9277:1995.
The cellulosic fibres of the composition of the invention may have a length
weighted mean
fibre length of from about 150, or from about 200, usually from about 300 pm,
and the
length weighted mean fibre length may be up to about 2,000, usually up to
about 1,500, or
up to about 1,100, usually up to about 1,000, or up to about 800 pm; and they
may have a
length weighted mean fibre width of from about 10, usually from about 15 pm,
and the
length weighted mean fibre width may be up to about 60, usually up to about
50, or up to
about 45, usually up to about 30 pm. In one embodiment, the cellulosic fibres
of the
composition of the invention have length weighted mean fibre width over 35 pm,
or from
about 40, up to about 60, or up to about 50. The cellulosic fibres of the
composition of the
invention may have a length weighted mean fibre length / width ratio up to
about 40, or up to
about 35, usually up to about 30, or up to about 25, and the length weighted
mean fibre
length / width ratio may be at least about 5, or at least about 10, usually at
least about 12. The
length weighted mean fibre length and length weighted mean fibre width, as
referred to
herein, are measured by means a Fiber Tester of Lorenzen & Wettre, Sweden,
which operates
according to ISO 16065-2:2007, and the length weighted mean length / width
ratio is
calculated from such data.
The cellulosic fibre composition of the invention may contain fines in an
amount of from
about 1, or from about 2, usually from about 5 % by weight, based on the total
weight of
the cellulosic fibres, and the composition may contain fines in an amount of
up to about
40, or up to about 35, usually up to about 30 % by weight, based on the total
weight of the
cellulosic fibres. The term "fines", as used herein, means cellulosic fibres
having a length
weighted mean fibre length up to 100 pm.
The cellulosic fibre composition of the invention may have a dry solids
content of at least
about 0.1, or at least about 0.5, usually at least about 5, or at least about
10, or at least about
15 % by weight, and the dry solids content may be up to about 90, or up to
about 70, usually
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up to about 50, or up to about 45 % by weight, based on the total weight of
the
composition. As the dry solids of the composition usually consist or
essentially consist of
cellulosic fibres, the composition may have a cellulosic fibre content which
is the same as the
dry solids content stated above. The remainder of the cellulosic fibre
composition may be
water.
According to a preferred embodiment, the method of producing the cellulosic
fibre
composition of the invention comprises subjecting cellulosic fibres to
chemical treatment
and mechanical treatment. The chemical treatment may be carried out prior to
or
simultaneously with the mechanical treatment, usually prior to the mechanical
treatment.
Cellulosic fibres for use in the method can be derived from a wide variety of
sources
including wood fibres, non-wood-fibres and mixtures thereof, as further
defined above in
respect of the cellulosic fibre composition of the invention.
According to another preferred embodiment, the method of producing the
cellulosic fibre
composition of the invention comprises subjecting cellulosic fibres having
anionic groups
to mechanical treatment, wherein the cellulosic fibres may have anionic groups
and an
average degree of substitution of anionic groups as defined above in respect
of the
cellulosic fibre composition of the invention. The cellulosic fibres for use
in the process
can be derived from a wide variety of sources including wood fibres, non-wood-
fibres and
mixtures thereof, as further defined above in respect of the cellulosic fibre
composition of
the invention, and cellulosic fibres suitable for use in the process can be
provided by any
method for introducing anionic groups in cellulose that is known in the art.
In one embodiment, the chemical treatment of the invention comprises treating
cellulosic
fibres with at least one agent containing a carboxyl group, optionally
substituted, which
chemical treatment is suitably carried out with an amount of the agent
containing a
carboxyl group, optionally substituted, and any compounds that are co-used as
defined
below so as to achieve the desired degree of substitution, which can be
determined by the
method defined above in respect of the cellulosic fibre composition of the
invention. In
another embodiment, the chemical treatment of the invention comprises treating
the
cellulosic fibres with at least one oxidant and at least one transition metal.
In yet another
embodiment, the chemical treatment of the invention comprises treating the
cellulosic
fibres with at least one nitroxyl radical.
Examples of suitable agent containing a carboxyl group, optionally
substituted, include
carboxylating agents and carboxyalkylating agents. Examples of suitable
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carboxyalkylating agents include chloroacetic acid, e.g. monochloroacetic
acid, and salts
thereof, suitably the sodium salt. The treatment may be conducted under
alkaline
conditions by contacting the cellulosic fibres with strong alkali, e.g. sodium
hydroxide, and
the agent containing a carboxyl group. These reagents may be applied to the
cellulosic
fibres separately or together. The reaction is conveniently performed in an
aqueous
system which comprises a water-miscible organic solvent, e.g. ethanol or
isopropanol, to
suppress swelling and dissolution of carboxyalkylated cellulose. Reference may
be made
to WO 94/16746, WO 00/47628 and US 6,548,730 for a general discussion of the
reaction between cellulosic fibres and agents containing a carboxyl group,
optionally
substituted, e.g. carboxyalkylating agents like monochloroacetic acid, and
further methods
for carboxyalkylation include those disclosed in US 4,634,438, US 4,634,439
and WO
95/19795, which are all hereby incorporated herein by reference.
Examples of suitable oxidants include radical generating oxidants, e.g.
inorganic or
organic peroxy compounds, ozone, ozonides, e.g. dimethyloxiran, halogen (e.g.
chlorine
or bromine) containing oxidants, and oxygen, preferably inorganic peroxy
compounds
such as those selected from hydrogen peroxide and hydrogen peroxide generating
compounds like alkali metal salts of percarbonate, perborate, peroxysulfate,
peroxyphosphate or peroxysilicate, or corresponding weak acids, preferably
hydrogen
peroxide. Examples of suitable organic peroxy compounds include peroxy
carboxylic
acids, e.g. peracetic acid and perbenzoic acid, and hydroperoxides, e.g.
isopropyl cumyl
hydroperoxide, 1,1,3,3-tetramethyl butyl hydroperoxide, cumyl hydroperoxide, t-
butyl
hydroperoxide and t-amyl hydroperoxide. Examples of suitable halogen
containing
oxidants include alkali metal chlorite, alkali metal hypochlorite, chlorine
dioxide and chloro
sodium salt of cyanuric acid. It is also possible to use ultrasonic sound or
photo or electro
Fenton reactions, i.e. in situ generation of hydroxyl radicals by radiation or
electric
currents. The oxidant may be used in the treatment an amount of from about
0.05 to
about 5, usually from about 0.1 to about 3 % by weight, based on the weight of
the
cellulosic fibres.
Examples of suitable transition metals include iron, copper, manganese,
tungsten,
molybdenum, tin, chromium and combinations thereof, preferably iron. The
transition
metal is suitably used in ionic form, e.g. Fee+, and it may be used in the
form of a salt, e.g.
FeS04, or complex with common complexing agents, e.g. EDTA, DTPA, phosphates
or
complexing agents based on phosphoric acid, oxalic acid, ascorbic acid,
nitrite acetate,
garlic acid, fulvic acid or polyoxomethalates. The amount of transition metal
used depends
on the amount of oxidant used and in most cases it is from about 0.000001 to
about 20, or
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from about 0.00001 to about 10, usually from about 0.0001 to about 1 % by
weight, based
on the weight of the oxidant. The transition metal, suitable in ionic form,
can be added to
the cellulosic fibres before, after or simultaneously with adding the oxidant,
for example in
the form of an aqueous solution.
5
Examples of suitable nitroxyl radicals include the 2,2,6,6-tetramethyl
piperidine-1-oxyl
(TEMPO) radical and derivatives thereof, e.g. 4-hydroxy-TEMPO. In the
treatment with the
nitroxyl radical, one or more compounds are preferably co-used. Examples of
such one or
more compounds include sodium hypochlorite (NaCIO), e.g. as disclosed by
Saito,
10 Kimura, Nishiyama and Isogai; Biomacromolecules 2007, 8, 2485-2491, the
disclosure of
which is hereby incorporated herein by reference, and sodium bromide. The
nitroxyl
radical may be used in the treatment in an amount of from about 0.05 to about
5, usually
from about 0.1 to about 3 % by weight, based on the weight of the cellulosic
fibres. Each
of the compounds that are preferably co-used with the nitroxyl radical in the
treatment can
be used in an amount of from about 1 to about 20 % by weight, based on the
weight of
the cellulosic fibres, suitably sodium hypochlorite is used in an amount of
from about 3 to
about 20 % by weight and sodium bromide is used in an amount of from about 2
to about
10 % by weight.
In the chemical treatment, the cellulosic fibres may be dispersed in water,
alcohol or any
other suitable liquid, usually in an aqueous suspension. The dry solids
content of the
aqueous suspension of cellulosic fibres in the chemical treatment may be from
about 1, or
from about 5, usually from about 10, up to about 60, or up to about 50,
usually up to about
40 % by weight, based on the total weight of the suspension.
Further additives that may be used in the chemical treatment include mineral
acids, e.g.
hydrochloric acid and sulphuric acid, or sodium hydroxide, and the chemical
treatment
may be carried out at a pH from about 1 to about 10. In one embodiment, e.g.
when using
at least one oxidant and at least one transition metal, the chemical treatment
may be
carried out at acidic or neutral pH from about 1 to about 8, or from about 2
to about 6,
usually from about 3 to about 5. In another embodiment, e.g. when using a
nitroxyl radical
or an agent containing a carboxyl group, optionally substituted, e.g. a
carboxyalkylating
agent, the chemical treatment may be carried out at alkaline pH from about 8
to about 10.
The chemical treatment may be carried out for about 10 to about 120, or from
about 20 to
about 80, usually from about 40 to about 60 minutes, and the temperature may
be from
about 5, usually from about 20, or from about 60, up to about 100, usually to
about 80, or
up to about 30 C. In one embodiment, e.g. when using at least one oxidant and
at least
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one transition metal, the temperature may be from about 20 to about 100,
usually from
about 60 to about 80 C. In another embodiment, e.g. when using the nitroxyl
radical, the
temperature may be from about 5, usually around about 20, up to about 30 C.
In one embodiment, the cellulosic fibres are subjected to a chemical treatment
at a dry
solids content of from about 1 to about 50 % by weight with from about 0.1 to
about 3 %
by weight of H202 as the oxidant, based on the weight of dry cellulosic
fibres, and an
aqueous solution of about 0.00001 to about 10 % by weight of FeSO4 as the
transition
metal, based on the weight of the oxidant, during from about 20 to about 80
minutes at
from about 70 to about 95 C at a pH from about 3 to about 5.
In another embodiment, the cellulosic fibres are subjected to a chemical
treatment at a dry
solids content of from about 1 to about 50 % by weight with from about 0.1 to
about 3 %
by weight of TEMPO, from about 3 to about 20 % by weight of NaCIO, and from
about 2
to 10 % by weight of sodium bromide, during from about 20 to about 80 minutes
at from
about 5 to about 30 C at a pH from about 9 to about 10, where the amounts of
chemicals
are based on the weight of dry cellulosic fibres.
When the chemical treatment is carried out prior to the mechanical treatment,
the
cellulosic fibre composition obtained by the chemical treatment may be washed
one or
more times with water and/or solvents to remove any chemicals, diluted with
water and/or
dried or concentrated to a dry solids content suitable for the subsequent
mechanical
treatment.
The mechanical treatment of the invention comprises subjecting cellulosic
fibres to
extrusion by using one or more extruders, and the extrusion may be continuous
or batch-
wise. In the mechanical treatment, when subjected to extrusion, the cellulosic
fibres may
have a dry solids content of from about 5, or from about 8, usually from about
10, or from
about 15, up to about 70, usually up to about 55, or up to about 50, often up
to about 45,
or up to about 40 % by weight. The remainder of the cellulosic fibre
composition may be
water.
Examples of suitable extruders for use in the process include twin-screw
extruders, or
double shaft extruders. The screws may be co-rotating or counter rotating,
preferably co-
rotating. The screws may have one or more screw elements, including conveying,
mixing
and kneading elements, along the length of the extruder. Other examples of
suitable
extruders include planetary roller extruders, also referred to as planetary
mixers. The
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planetary roller extruder usually has a central main spindle and from 4 to 20
rolling
planetary spindles. The length of the screw of twin-screw extruders, or the
main spindle /
barrel of planetary roller extruders, may be at least about 3, or at least
about 5, usually at
least about 10, or at least about 15 times the diameter of the screw or main
spindle /
barrel, and the length may be up to about 70, or up to about 60, usually up to
about 50
times the diameter of the screw or main spindle / barrel. The diameter of the
screw or
main spindle is usually at least about 15 mm and may be up to about 150 mm or
even
higher. Preferably, the extruder comprises one or more kneading elements. The
extruder
may have a flexible screw configuration with intermeshing screw elements that
can be
assembled into several conveying, mixing and kneading sections. Hereby the
cellulosic
fibres may be fed into the extruder, passed through alternating sets of
transport, mixing
and kneading sections until the kneaded cellulosic fibres are ejected. The
cellulosic fibres
may be passed through the extruder one or more times. In the process, the
cellulosic
fibres are preferably subjected to shearing and kneading forces. The extrusion
may be
carried out at a temperature of from about 20 to about 100, usually from about
40 to about
80 C. The extruder or parts thereof, e.g. one or more barrels, may be
subjected to
cooling during the extrusion process. Twin-screw extruders and planetary
roller extruders
are commercially available from several manufacturers such as Buhler,
Berstorff, e.g.
Berstorff ZE 25 and Berstorff ZE 40, Bottenfeld Extrusionstechnik, and Entex,
e.g. Extex
PLWE100.
The cellulosic fibres and the composition thereof obtained by these chemical
and/or
mechanical treatment steps of the invention may have a specific surface area,
length
weighted mean fibre length, length weighted mean fibre width, length weighted
mean fibre
length / width ratio, fines content, dry solids content, degree of
substitution of anionic
groups and cellulosic fibre content as defined above in respect of the
cellulosic fibre
composition of the invention.
It is also possible to further dry or concentrate the cellulosic fibre
composition by suitable
drying techniques, e.g. freeze drying, etc., to higher dry solids contents,
e.g. up to about
90 % by weight. Hereby transportation of the obtained cellulosic fibre
composition may be
simplified. It is also possible to add water to or dilute the cellulosic fibre
composition to a
dry solids content lower than about 10 % by weight, e.g. from about 0.1 to
about 10, usually
from about 0.5 to about 5 % by weight. Hereby the use of the obtained
cellulosic fibre
composition may be simplified, e.g. for mixing with an aqueous cellulosic pulp
suspension
for use in paper and board making.
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The invention also relates to the use of the cellulosic fibre composition of
the invention or
obtained by the method of the invention in the production of paper and board.
The
invention also relates to the use of a composition comprising cellulosic
fibres subjected to
extrusion, as described above, as an additive in the production of paper and
board,
wherein the composition subjected to extrusion may have or may not have been
subjected
to chemical treatment, as described above. Paper and board can be produced
from an
aqueous suspension comprising the cellulosic fibre composition. Preferably,
the cellulosic
fibre composition is used as an additive to an aqueous cellulosic pulp
suspension to
impart strength to paper and board produced from the resulting aqueous
cellulosic pulp
suspension. The cellulosic fibre composition may be mixed with or added to the
cellulosic
pulp suspension in an amount of from about 0.1 to about 25, suitably from
about 0.5 to
about 15, or from about 1 to 10, usually from about 2 to about 8 % by weight,
calculated
as dry cellulosic fibres of the composition on dry cellulosic pulp.
The invention further relates to a process for producing a cellulosic pulp
mixture which
comprises mixing the cellulosic fibre composition of the invention or obtained
by the
method of the invention with cellulosic pulp.
The cellulosic pulp can be derived from a wide variety of sources including
wood fibres,
non-wood fibres and mixtures thereof. Examples of suitable wood and non-wood
fibres
include those defined above in respect of the cellulosic fibre composition of
the invention.
Preferably, the cellulosic pulp is derived from wood fibres such as hardwood,
softwood
and mixtures thereof, and preferably comprising softwood fibres.
The cellulosic pulp may be derived from chemical pulp, e.g. sulfate and
sulfite pulp,
organosolv pulp, recycled fibers, and/or mechanical pulp including e.g.
refiner mechanical
pulp (RMP), pressurized refiner mechanical pulp (PRMP), pretreatment refiner
chemical
alkaline peroxide mechanical pulp (P-RC APMP), thermo-mechanical pulp (TMP),
thermo-
mechanical chemical pulp (TMCP), high-temperature TMP (HT-TMP) RTS-TMP,
alkaline
peroxide pulp (APP), alkaline peroxide mechanical pulp (APMP), alkaline
peroxide
thermomechanical pulp (APTMP), thermopulp, groundwood pulp (GW), stone
groundwood
pulp (SGW), pressure groundwood pulp (PGW), super pressure groundwood pulp
(PGW-
S), thermo groundwood pulp (TGW), thermo stone groundwood pulp (TSGW), chemi-
mechanical pulp (CMP), chemirefinermechanical pulp (CRMP), chemithermo-
mechanical
pulp (CTMP), high-temperature CTMP (HT-CTMP), sulfite-modified thermo-
mechanical
pulp (SMTMP), reject CTMP (CTMPR), groundwood CTMP (G-CTMP), semichemical pulp
(SC), neutral sulfite semi chemical pulp (NSSC), high-yield sulfite pulp
(HYS),
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biomechanical pulp (BRMP), pulps produced according to the OPCO process,
explosion
pulping process, Bi-Vis process, dilution water sulfonation process (DWS),
sulfonated long
fibers process (SLF), chemically treated long fibers process (CTLF), long
fiber CMP
process (LFCMP), and modifications and combinations thereof. The pulp may be a
bleached or non-bleached pulp.
The cellulosic fibre composition may be mixed with or added to the cellulosic
pulp in an
amount of from about 0.1 to about 25, suitably from about 0.5 to about 15, or
from about 1
to 10, usually from about 2 to about 8 % by weight, calculated as dry
cellulosic fibres of
the composition on dry cellulosic pulp.
In one embodiment, the mixing is made in a substantially dry state. The mixing
of the
cellulosic fibre composition with the cellulosic pulp may be made to form a
cellulosic pulp
mixture, which may have a dry solids content of at least about 10, usually at
least about
15, usually from about 20, up to about 90, or up to about 50 % by weight,
based on the
total weight of the cellulosic pulp mixture. The remainder of the cellulosic
pulp mixture may
be water. The cellulosic pulp mixture may be added to or mixed with water to
form an
aqueous suspension comprising the cellulosic pulp mixture and then dewatering
the
obtained suspension. The aqueous suspension may have a dry solids content of
up to
about 10 % by weight, e.g. from about 0.1, or from about 0.2, usually from
about 0.3, up
to about 10, or up to about 8, up to about 6, usually up to about 5 % by
weight, based on
the total weight of the cellulosic pulp mixture.
In another embodiment, the mixing is made in a substantially wet state. The
mixing of the
cellulosic fibre composition with the cellulosic pulp may be made to form a
cellulosic pulp
mixture in the form of an aqueous suspension and then dewatering the obtained
suspension. The process may comprise adding the cellulosic fibre composition
to an
aqueous cellulosic pulp suspension and dewatering the obtained suspension. The
aqueous suspension may have a dry solids content of up to about 10 % by
weight, e.g.
from about 0.1, or from about 0.2, usually from about 0.3, up to about 10, or
up to about
8, up to about 6, usually up to about 5 % by weight, based on the total weight
of the
cellulosic pulp mixture.
Preferably, the cellulosic pulp mixture is used in the production of paper and
board
wherein the cellulosic pulp mixture may constitute at least part of the
cellulosic pulp used
in the process, usually the total amount of cellulosic pulp used in the
process. Preferably,
when producing paper and board, an aqueous suspension comprising the
cellulosic pulp
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mixture is formed and then dewatered. Various additives may be introduced in
the
aqueous suspension comprising the cellulosic pulp mixture prior to dewatering,
including
the additives and their addition levels as defined below in respect of the
process for
producing paper and board of the invention, in particular one or more drainage
and
5 retention aids.
The invention further relates to a process for producing paper and board which
comprises
providing an aqueous suspension comprising the cellulosic fibre composition
according to
the invention or produced according to the process of the invention and
dewatering the
10 obtained suspension. The invention further relates to a process for
producing paper and
board which comprises adding the cellulosic fibre composition according to the
invention
or produced according to the process of the invention to an aqueous suspension
comprising cellulosic pulp and dewatering the obtained suspension. The
invention further
relates to a process for producing paper and board which comprises mixing a
composition
15 comprising cellulosic fibres subjected to extrusion, as described above,
with cellulosic
pulp, wherein the composition subjected to extrusion may have or may not have
been
subjected to chemical treatment, as described above. Preferably, in the
process, use is
made of an aqueous suspension of the cellulosic fibre composition. The
cellulosic pulp
used in the process may be derived from the cellulosic pulp defined above.
Examples of
suitable wood and non-wood fibres include those defined above in respect of
the
cellulosic fibre composition of the invention. Preferably, the cellulosic pulp
is derived from
wood fibres such as hardwood, softwood and mixtures thereof, and preferably
comprising
softwood fibres.
In the process, the cellulosic fibre composition can be added to the
cellulosic pulp
suspension in an amount of from about 0.1 to about 25, suitably from about 0.5
to about
15, or from about 1 to 10, usually from about 2 to about 8 % by weight,
calculated as dry
cellulosic fibres of the composition on dry cellulosic pulp.
Further additives may also be used in the process of the invention, and they
may be
added to the cellulosic fibre composition, to the aqueous suspension
comprising the
cellulosic fibre composition, to the aqueous suspension comprising cellulosic
pulp and/or
to the aqueous suspension comprising the cellulosic pulp mixture, usually to
the aqueous
suspension comprising cellulosic fibre composition and/or cellulosic pulp
and/or cellulosic
pulp mixture. Examples of suitable further additives include one or more
drainage and
retention aids, cationic coagulants, dry strength agents, wet strength agents,
e.g.
polyamine-epichlorohydrin and polyamidoamine-epichlorohydrin based resins,
optical
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brightening agents, dyes, sizing agents, e.g. rosin-based sizing agents,
styrene acrylates
and cellulose-reactive sizing agents, e.g. alkyl and alkenyl ketene dimers and
multimers,
and alkenyl succinic anhydrides, etc.
The further additives preferably comprise one or more drainage and retention
aids. The
expression "drainage and retention aid", as used herein, refers to one or more
additives
which, when added to an aqueous cellulosic suspension, give better drainage
and/or
retention than is obtained when not using said one or more additives. The one
or more
drainage and retention aids may comprise anionic polymers, cationic polymers,
siliceous
materials and combinations thereof, preferably at least one cationic polymer.
Examples of
suitable anionic polymers include anionic polyacrylamide and anionic
naphthalene-
formaldehyde condensation polymers, e.g. anionic naphthalene sulfonates.
Examples of
suitable cationic polymers include cationic polysaccharides, e.g. cationic
starches, and
cationic synthetic polymers, e.g. cationic polyacrylamides, cationic
poly(diallyldimethyl-
ammonium chlorides), cationic polyethylene imines, cationic polyamines and
cationic
polyamidoamines. The weight average molecular weight of the anionic and
cationic polymers
may be above about 5,000, or above about 10,000, usually above about 1,000,000
g/mole.
The upper limit is not critical; it can be about 50,000,000 g/mole, usually
30,000,000 g/mole.
Examples of suitable siliceous materials include anionic silica-based
particles and anionic
clays of the smectite type, e.g. bentonite. Preferably, the siliceous material
has particles in
the colloidal range of particle size. Anionic silica-based particles, i.e.
particles based on Si02 or
silicic acid, are preferably used and such particles are usually supplied in
the form of aqueous
colloidal dispersions, so-called sols. Examples of suitable silica-based
particles include colloid-
al silica and different types of polysilicic acid, either homopolymerised or
co-polymerised, for
example polymeric silicic acid, polysilicic acid microgel, polysilicate and
polysilicate microgel.
The silica-based sols can be modified and contain other elements, e.g.
aluminum, boron,
magnesium, nitrogen, zirconium, gallium, titanium and the like, which can be
present in the
aqueous phase and/or in the silica-based particles.
Examples of preferred drainage and retention aids for use in the process
include cationic
starches, cationic polyacrylamides, anionic polyacrylamides, anionic siliceous
materials
and combinations thereof. Examples of suitable combinations of drainage and
retention
aids comprise (i) cationic starch and anionic siliceous material, preferably
silica-based
particles, (ii) cationic polyacrylamide and anionic siliceous material,
preferably silica-based
particles, (iii) cationic starch, cationic polyacrylamide and anionic
siliceous material,
preferably silica-based particles, (iv) cationic polyacrylamide, anionic
polyacrylamide and
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anionic siliceous material, preferably silica-based particles, and (v)
cationic starch, anionic
polyacrylamide and anionic siliceous material, preferably silica-based
particles.
The one or more drainage and retention aids can be added to the suspension in
amounts
which can vary within wide limits depending on, inter alia, type and number of
additives, type of
suspension, point of addition, etc. When used, the anionic polymers are
usually added in an
amount of at least 0.001, often at least 0.005 % by weight, based on dry
weight of the
suspension, and the upper limit is usually 3 and suitably 1.5 % by weight.
When used, the
cationic polymers are usually added in an amount of at least about 0.001,
often at least about
0.005 % by weight, based on dry weight of the suspension, and the upper limit
is usually about
3 and suitably about 1.5 % by weight. When used, the siliceous materials are
usually added
in an amount of at least about 0.001, often at least about 0.005 % by weight,
based on dry
weight of the suspension, and the upper limit is usually about 1.0 and
suitably about 0.6 % by
weight.
The drainage and retention aids can be added in conventional manner and in any
order.
When using a siliceous material, it is common to add a cationic polymer before
adding the
siliceous material, even if the opposite order of addition may also be used.
It is further
common to add a cationic polymer before a shear stage, which can be selected
from
pumping, mixing, cleaning, etc., and to add the siliceous material after that
shear stage.
Examples of suitable coagulants include organic and inorganic coagulants.
Examples of
suitable organic coagulants include low molecular weight cationic polymers,
e.g. homo
and copolymers of diallyl dimethyl ammonium chloride (DADMAC), polyamines,
polyamideamines, polyethylene imines, and dicyandiamide condensation polymers
having
a molecular weight in the range of from 1,000 to 700,000, suitably from 10,000
to
500,000. Examples of suitable inorganic coagulants include aluminium
compounds, e.g.
alum and polyaluminium compounds, e.g. polyaluminium chlorides, polyaluminium
sulpha-
tes, polyaluminium silicate sulphates and mixtures thereof.
When used, the coagulant is preferably added prior to adding the one or more
drainage and
retention aids. The cationic coagulant can be added in an amount of at least
about 0.001, or
from about 0.05, usually from about 0.1, up to about 3.0, usually up to about
2.0 % by weight,
calculated as dry coagulant on dry suspension,
When used, each of the dry strength agent, wet strength agent and sizing agent
as
defined above can be added to the suspension in an amount of from about 0.01
to about
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1, usually from about 0.1 to about 0.5 % by weight, calculated as dry agent on
dry
suspension.
The process of the invention may comprise the use of mineral fillers of
conventional types,
e.g. kaolin, china clay, titanium dioxide, gypsum, talc and natural and
synthetic calcium
carbonates, e.g. chalk, ground marble and precipitated calcium carbonate.
The process may produce single ply paper or board in which the cellulosic
fibre
composition, as defined herein, is distributed throughout the paper or board,
preferably
substantially uniformly distributed throughout the paper and board. Single ply
paper and
board contain just one ply or layer containing cellulosic fibres.
The process may also produce multi ply paper and board comprising two or more
plies or
layers containing cellulosic fibres wherein at least one of said two or more
plies or layers
comprises the cellulosic fibre composition, as defined herein. Preferably, the
cellulosic
fibre composition is distributed throughout at least one of said two or more
plies, more
preferably substantially uniformly distributed throughout at least one of said
two or more
plies. Multi ply board according to the invention can be produced by forming
at least one
ply comprising the cellulosic fibres composition, as defined herein, and
attaching said at
least one ply to one or more plies containing cellulosic fibres to form the
multi ply board.
For example, multi ply board can be produced by forming the individual plies
or layers
separately in one or several web-forming units and then couching them together
in the wet
state. Examples of suitable grades of multi ply board of the invention include
those
comprising from two to seven plies or layers comprising cellulosic fibres and
wherein at
least one of said plies or layers comprises the cellulosic fibre composition,
as defined
herein, preferably one or more of the middle (internal) plies or layers.
In the process of the invention, the board, e.g. single or multi ply board,
can be subjected
to further process steps. Examples of suitable process steps include coating,
e.g. starch
coating and pigment coating, creasing, printing and cutting. Accordingly,
examples of
suitable boards of the invention include coated board, e.g. starch and/or
pigment coated,
and printed board.
The term "board, as used herein, refers to board comprising cellulosic fibres
including
solid board, e.g. solid bleached sulphate board (SBS) and solid unbleached
sulphate
board (SUS), paper board, carton board, e.g. folding boxboard (FBB), folding
carton
board, liquid packaging board (LPB), including all types of aseptic, non-
aseptic
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autoclavable packaging boards, white lined chipboard (WLC), unbleached
kraftboard,
grey chipboard and recycled board, liner board and container board, including
white
sulphate kraftliner, fully bleached kraftliner, testliner, white sulphate
testliner, unbleached
kraftliner, unbleached testliner and recycled liner, fluting and corrugated
fluting. The board
may have a grammage of at least about 130, usually at least about 140 or at
least about
150 g/m2, and it may be up to about 1,400, or up to about 1,300 g/m2. The
board may
have a bulk density of at least about 120, usually at least about 150, or at
least about 200
kg/m3, and it may be up to about 1,400, usually up to about 800, or up to
about 600 kg/m3.
The invention further relates to a method for producing a packaging material
which
comprises providing board comprising one or more plies comprising the
cellulosic fibres
composition, as defined herein, and subjecting the board to one or more
converting
operations selected from printing, varnishing, coating, e.g. plastics coating,
extrusion
coating and barrier coating, laminating, e.g. plastic film laminating and
metal foil
laminating, e.g aluminium foil laminating, metallizing, die cutting, i.e.
stamping out blanks,
creasing, scoring, stripping, i.e. removal or debris, blanking, i.e.
separation of blanks, foil
blocking, embossing and folding. The term "creasing", as used herein, is also
referred to
as scoring and grooving. Usually, the method includes one or more converting
operations
comprising scoring or creasing, more preferably two or more operations
comprising
scoring or creasing, for example cutting and scoring or creasing.
The invention also relates to a packaging material comprising board which
comprises one
or more plies comprising the cellulosic fibre composition, as defined herein,
wherein it
further comprises one or more creases. The creases, also referred to as
scores, grooves
or folding lines, make it easier to fold and erect the packaging material
prior to filling. The
packaging materials of the invention can have one or more layers of plastic
film, metal foil,
e.g. aluminium, and/or barrier coating.
The invention further relates to a procedure of making a package which
comprises
providing a blank of packaging material comprising board comprising one or
more plies
comprising the cellulosic fibre composition, as defined herein, filling the
blank with a solid
or liquid content to obtain an unsealed package, and then sealing the obtained
package.
Preferably the packaging material comprises one or more grooves, creases or
scores. The
term "blank", as used herein, means an unfilled package or packaging material.
Preferably
the blank is folded and erected prior to filling. Examples of suitable methods
for sealing
include gluing and heat sealing. The invention further relates to a procedure
of making a
package which comprises providing a reel of packaging material comprising
board
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comprising one or more plies comprising the cellulosic fibre composition, as
defined
herein, whereupon the reel of packaging material is introduced into a filling
machine, filled
with a solid or liquid content, sealed and cut into separate packages which
may be folded
to the desired shape.
5
Examples of suitable solid and liquid contents include solid and liquid
foodstuffs, e.g.
tomato products, soup, cream, chocolate and cereals, beverages, e.g. milk,
fruit juice,
wine and water, pharmaceuticals, cosmetics, cigarettes, tobacco and
detergents. In one
embodiment, the invention further comprises sterilizing the package and/or the
solid or
10 liquid content. The term "sterilizing", as used herein, means reducing the
number of
microorganisms. Examples of suitable methods and means for sterilization
include heat,
e.g. rapid heating and cooling, chemicals, e.g. ozone and hydrogen peroxide,
irradiation,
e.g. IR and UV irradiation. The filling can be made under high hygiene or
sterile
conditions.
The invention also relates to a packaging comprising board comprising one or
more plies
containing the cellulosic fibre composition, as defined herein, wherein it
further comprises
a solid or liquid content. The invention further relates to uses of the
packaging material
comprising board, which comprises one or more plies containing the cellulosic
fibre
composition, as defined herein, for packaging of solid or liquid foodstuffs,
beverages,
pharmaceuticals, cosmetics, cigarettes, tobacco or detergents.
Examples of suitable packaging of the invention include foodstuff packaging,
beverage
packaging, sterile packaging and aseptic packaging.
Examples
The invention is further illustrated in the following examples which, however,
are not
intended to limit the same. Parts and % relate to parts by weight and % by
weight,
respectively, and all suspensions are aqueous, unless otherwise stated.
Chemical and mechanical treatments were conducted as described below. When
both
treatments were conducted, the chemical treatment was conducted before the
mechanical
treatment:
Chemical Treatment 1
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Chemical treatment 1 (referred to as "CT1") was carried out using cellulosic
fibres at a dry
solids content of 10 % by weight with 40 ppm Fe +2 (added as FeSO4) and 1 %
H202,
based on the weight of dry cellulosic fibres, at pH 4 (adjusted with H2SO4)
and a
temperature of 70 C for 30 min.
Chemical Treatment 2
Chemical treatment 2 (referred to as "CT2") was carried out as in Chemical
Treatment 1 except
that the amount of H202 used was 0.1 % by weight, based on the weight of dry
cellulosic
fibres, and the temperature was 90 C
Chemical Treatment 3
Chemical treatment 3 (referred to as "CT3") was carried out using cellulosic
fibers at a dry
solid content of 2 % by weight with 1 ,6 % by weight TEMPO (2,2,6,6-
tetramethylpiperidine-1-oxyl radical), based on the weight of dry cellulosic
fibers, and 10 %
by weight of NaBr and 3.7 % by weight of NaCIO, based on the weight of dry
cellulosic
fibers, at pH 10 (adjusted with NaOH) and temperature of 20 C for 60 min.
Chemical Treatment 4
Chemical treatment 4 (referred to as "CT4") was carried out by treating
cellulosic fibers with
monochloroacetic acid under alkaline conditions according to the general
procedure for
preparation of carboxymethyl cellulose disclosed by WO 00/47628. By using
varying
amounts of reactants, cellulosic compositions having different degrees of
substitution of
anionic / carboxymethyl groups were obtained.
Mechanical Treatment 1
Mechanical treatment 1 (referred to as "MT1" in the tables below) was carried
out using
untreated or chemically treated cellulosic fibres. The cellulosic fibres were
washed with
water and concentrated to a desired dry solids content and then passed through
a co-
rotating twin-screw extruder (Berstorff ZE 25A-UTS-UG) which had a screw
diameter of 25
mm, core diameter of 17 mm, centre distance of 21.5 mm and extrusion unit
length of 48D
(1200 mm) having 10 barrels with individual heating/cooling possibilities
which were
cooled with tap water. The extruder screws were built up with conveying and
kneading
elements and had the screw configuration as shown in Figure 1, where left and
right
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screws were equal. The drive power at maximum admissible screw speed (1200
rpm) was
22.6 kW (Siemens DC motor, type 1 GG5134-OGH46-6WV1).
The pulp was fed gravimetrically with a feeding device (K-Tron-Soder T20). The
extruder
was run at a screw speed of 1000 rpm. The cellulosic fibres were fed at a feed
rate of 0.8
kg dry solids/h, unless otherwise stated.
Mechanical Treatment 2
Mechanical treatment 2 (referred to as "MT2" in the tables below) was carried
out using
untreated or chemically treated cellulosic fibres. The cellulosic fibres were
washed with
water and concentrated to a desired dry solids content and then passed through
a
planetary roller extruder (Entex PLWE100 with a 5.25 I/d barrel). The cooled
central
spindle had a diameter of 100 mm and the planetary roller extruder had 6
rolling planetary
spindles.
Mechanical Treatment 3
Mechanical treatment 3 (referred to as "MT3" in the tables below) was used for
comparison
and carried out according to the procedure of Example 1 b of WO 2007/001229 in
which a
cellulosic fibre suspension at a desired dry solids content was passed through
a pearl mill
(Drais PMC 25TEX) once or twice, unless otherwise stated, using zirconium
oxide pearls (2.0
mm in diameter, 65% filling grade), rotor speed of 1200 rpm and a flow rate of
100 I/h.
Mechanical Treatment 4
Mechanical treatment 4 (referred to as "MT4" in the tables below) was used for
comparison
and carried out according to the general procedure for microfibrillation of
carboxymethyl
cellulose disclosed by WO 00/47628 in which a cellulosic fibre suspension at a
fibre
content of about 1 % by weight was subjected to homogenization.
Analysis of Cellulosic Fibres
Length weighted mean fibre length (referred to as "Fibre Lengh" in the tables
below) and
length weighted mean fibre width (referred to as "Fibre Width" in the tables
below) of the
cellulosic fibres were measured by means a Fiber Tester of Lorenzen & Wettre,
Sweden,
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which operates according to ISO 16065-2:2007. The length weighted mean fibre
length / width
ratio (referred to as "Length / Width Ratio" in the tables below) was
calculated from such data.
The content of cellulosic fibres having a length weighted mean fibre length up
to 100 pm
(referred to as "Fines Content" in the tables below) was determined using the
same Lorenzen
& Wettre Fiber Tester.
Specific surface areas were determined by adsorption of N2 at 177 K according
to the BET
method using a Micromeritics TriStar 3000 instrument, which operates according
to ISO
9277:1995. The cellulosic fibres to be analysed were frozen in a freezing
equipment at the
consistency received after any chemical and/or mechanical treatments, freeze
dried in a
Heto FD3 freeze drier, degassed at 90 C for 3 hours and thereafter analysed
for specific
surface area.
Water retention values (referred to as "WRV" in the tables below) were
determined
according to SCAN-C 62:00. The samples to be analysed were aqueous pulp
suspensions at a consistency of 0.5 % in which the dry pulp consisted of 95 %
by weight
of CTMP and 5 % by weight of cellulosic fibre composition according to the
invention or
cellulosic composition used for comparison, unless otherwise stated. The water
retention
value is a measure of the capacity of the pulp to hold or retain water, and an
indication of
the energy needed to remove the water and dry the cellulosic sheet; a lower
water
retention value indicates less energy to remove water and dry the cellulosic
sheet.
Average degree of substitution of anionic / carboxymethyl groups (referred to
as "DS" in
the tables below) was determined by the method of conductometric titration as
described
by S. Katz, R.P. Beatson and A.M. Scallan in Svensk Papperstidning No. 6/1984,
pp. 48-
53.
Production and Analysis of Paper and Board
Cellulosic compositions were used as additives in a paper and board making
process in
which paper or board sheets with a grammage of approximately 150 g/m2 were
made
according to ISO 5269-1:1998 using a dynamic sheet former (Formette Dynamic,
supplied
by Fibertech AB, Sweden). The pulp used consisted of 90 % high bulk CTMP (CSF
700
ml) and 10 % softwood (SR 28). Pulp suspensions at a consistency of 0.5 % and
conductivity 1.0 mS/cm at pH 7 were formed in a mixing chest and the following
additions
were made:
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(i) chemically treated and/or mechanically treated cellulosic composition, if
any, was
added to the suspension in an amount of 5 % by weight, calculated as dry
cellulosic composition on dry suspension, whereupon the obtained suspension
was mixed for 15 seconds,
(ii) cationic potato starch (Pearlbond 970) was added to the suspension in an
amount of 10 kg/t, based on dry suspension, whereupon the suspension was
mixed for 30 seconds, and
(iii) a siliceous material in the form of silica-bases particles (Eka NP 442,
Eka
Chemicals) was added to the suspension in an amount of 0.3 kg/t, calculated as
Si02 and based on dry suspension, whereupon the suspension was mixed for 15
seconds,
and then the obtained suspension was pumped from the mixing chest through a
traversing nozzle on a wire positioned on a rotating drum of the dynamic sheet
former
where it was dewatered for 90 seconds for sheet formation.
The obtained paper or board sheets were pressed in a plane press at 5 bar for
5 minutes
and thereafter dried restrained in a plane drier at 115 C for 12 minutes. The
paper or
board sheets were conditioned in a climate room according to ISO 187:1990 and
thereafter analysed in terms of tensile strength index (Nm/g) according to ISO
1924-
3:2005 using an Alwetron TH1 of Lorenzen & Wettre, Sweden.
The obtained results were compared to the tensile strength index of a
reference where no
or a differently treated cellulosic fibre composition was used as an additive
according to (i)
in the production process described above, and expressed as change in tensile
strength
index, if any, in percent, over the reference (referred to as "Strength
Contribution" in the
tables below), where + and - indicate an increase and decrease, respectively,
in tensile
strength index.
Example 1
Cellulosic fibres of bleached kraft birch pulp were subjected to chemical
treatment and/or
mechanical treatment and the obtained compositions were analysed. The results
are
shown in Table 1, in which the dry solids content (% by weight) of the
cellulosic fibres in
the mechanical treatment is given in parenthesis.
Test Nos. 1 and 2 refer to cellulosic fibre compositions subjected to
extrusion (MT1).
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Table 1
Test Chem. Mech. Fibre Fibre Length/ Specific
No. Treat- Treat- Length Width Width Surface
ment ment [ m] [ m] Ratio Area
[m2/g]
1 - MT1 (40) 790 22 36 4.0
2 CT1 MT1 (40) 710 25 28 5.0
Example 2
5
Cellulosic fibres of bleached kraft birch pulp were subjected to chemical
treatment and/or
mechanical treatment and the obtained compositions were analysed. The results
are
shown in Table 2, in which the dry solids content (% by weight) of the
cellulosic fibres in
the mechanical treatment is given in parenthesis.
Test No. 1 refers to the cellulosic fibres derived from the bleached birch
kraft pulp used as
a reference. Test Nos. 2 and 3 refer to cellulosic fibre compositions which
had been
passed through the pearl mill (MT3) used for comparison once and twice,
respectively.
Table 2
Test Chem. Mech. Fibre Fines
No. Treat- Treat- Length Content
ment ment [ m] [%]
1 - - 800 5
2 CT1 MT3 (2.0) 500 31
3 CT1 MT3 (2.0) 400 42
Example 3
Cellulosic fibres of bleached kraft birch pulp were subjected to chemical
treatment and/or
mechanical treatment and the obtained compositions were used as additives in
the
production of paper / board and analysed. The results are shown in Table 3, in
which the
dry solids content (% by weight) of the cellulosic fibres in the mechanical
treatment is
given in parenthesis.
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Test No. 1 refers to the cellulosic fibres derived from bleached birch kraft
pulp used as a
reference. Test Nos. 2 and 3 refer to cellulosic fibre compositions subjected
to extrusion
(MT1) at a feed rate of 0.8 and 1.2 kg dry solids/h, respectively.
Table 3
Test Chem. Mech. Fibre Fibre Length/ Fines Specific Strength
No. Treat- Treat- Length Width Width Content Surface Contri-
ment ment [ m] [ m] Ratio [%] Area bution
[m2/g] [%]
1 - - 840 21 40 5 1.0 0
2 CT3 MT1 (30) 680 25 27 11 >1.5 +12
3 CT3 MT1 (30) 760 25 30 7 >1.5 +5
Example 4
Cellulosic fibres of birch were subjected to chemical treatment and/or
mechanical
treatment and the obtained compositions were used as additives in the
production of
paper / board and analysed. The results are shown in Table 4, in which the dry
solids
content (% by weight) of the cellulosic fibres in the mechanical treatment is
given in
parenthesis.
Test No. 1 refers to the reference pulp suspension when no cellulosic fibre
composition
was used as an additive. Test No. 2 refers to the composition of cellulosic
fibres derived
from birch used for comparison, and Test Nos. 3 to 8 refer to different
cellulosic fibre
compositions used as additives.
Table 4
Test Chem. Mech. Fibre Fibre Length/ Fines Specific Strength
No. Treat- Treat- Length Width Width Content Surface Contri-
ment ment [ m] [ m] Ratio [%] Area bution
[m2/g] [%]
1 - - - - - - - 0
2 - - 840 21 40 5 1.0 -2
3 CT2 - 840 21 40 5 1.3 -5
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Test Chem. Mech. Fibre Fibre Length/ Fines Specific Strength
No. Treat- Treat- Length Width Width Content Surface Contri-
ment ment [ m] [ m] Ratio [%] Area bution
[m2/g] [%]
4 CT2 MT1 (20) 675 25 27 11 3.7 +11
CT2 MT1 (30) 560 26 22 15 2.6 +9
6 CT2 MT1 (35) 500 26 19 20 4.3 +7
7 CT2 MT1 (40) 415 27 15 26 5.4 +4
8 CT2 MT1 (45) 360 27 13 30 5.6 +6
Table 4 shows that the use of the compositions comprising cellulosic fibres
according to
the invention in Test Nos. 4-8 resulted in paper / board with improved tensile
strength
index over the compositions comprising cellulosic fibres used for comparison.
5
Example 5
Cellulosic fibres of birch were subjected to chemical treatment and/or
mechanical
treatment and the obtained compositions were analysed. The results are shown
in Table
5, in which the dry solids content (% by weight) of the cellulosic fibres in
the mechanical
treatment is given in parenthesis.
Test No. 1 refers to the composition of cellulosic fibres derived from birch.
Test Nos. 2 to 4
refer to cellulosic fibre compositions derived from birch which had been
passed through
the pearl mill (MT3) used for comparison.
Table 5
Test Chem. Mech. Fibre Fines
No. Treat- Treat- Length Content
ment ment [ m] [%]
1 - - 840 5
2 - MT3 (0.5) 315 34
3 CT2 MT3 (0.5) 270 42
4 CT2 MT3 (1.0) 300 42
Example 6
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Cellulosic fibres of pine were subjected to chemical treatment and/or
mechanical
treatment and the obtained compositions were used as additives in the
production of
paper / board an analysed. The results are shown in Table 6, in which the dry
solids
content (% by weight) of the cellulosic fibres in the mechanical treatment is
given in
parenthesis.
Test No. 1 refers to the pulp suspension when no cellulosic fibre composition
was used as
an additive. Test No. 2 refers to the cellulosic fibres derived from pine used
for
comparison. Test Nos. 3 to 8 refer to different cellulosic fibre compositions
used as
additives.
Table 6
Test Chem. Mech. Fibre Fibre Length/ Fines Specific Strength
No. Treat- Treat- Length Width Width Content Surface Contri-
ment ment [ m] [ m] Ratio [%] Area bution
[m2/g] [%]
1 - - - - - - - 0
2 - - 2010 29 69 5 1.2 0
3 CT2 - 1995 29 69 5 0.9 -1
4 CT2 MT1 (10) 845 32 26 16 5.3 +22
5 CT2 MT1 (15) 765 31 25 17 5.8 +13
6 CT2 MT1 (20) 715 31 23 20 5.5 +7
7 CT2 MT1 (30) 545 30 18 27 6.2 +18
8 CT2 MT1 (35) 485 30 16 30 6.7 +17
Table 6 shows that the use of the compositions comprising cellulosic fibres
according to
the invention in Test Nos. 4-8 resulted in paper / board with significantly
improved tensile
strength index over the compositions comprising cellulosic fibres used for
comparison.
Example 7
Cellulosic fibres of pine were subjected to chemical treatment and/or
mechanical
treatment and the obtained compositions were used as additives in the
production of
paper / board and analysed. The results are shown in Table 7, in which the dry
solids
content (% by weight) of the cellulosic fibres in the mechanical treatment is
given in
parenthesis.
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Test No. 1 refers to the composition of cellulosic fibres derived from pine
used for
comparison. Test Nos. 2 to 5 refer to cellulosic fibre compositions which had
been
subjected to extrusion (MT1) according to the invention.
Table 7
Test Chem. Mech. Strength
No. Treat- Treat- Contri-
ment ment bution
[%]
1 - - 0
2 - MT1 (30) +11
3 - MT1 (35) +12
4 CT2 MT1 (30) +18
5 CT2 MT1 (35) +17
Example 8
Cellulosic fibres of pine were subjected to chemical treatment and/or
mechanical
treatment and the obtained compositions were analysed. The results are shown
in Table
8, in which the dry solids content (% by weight) of the cellulosic fibres in
the mechanical
treatment is given in parenthesis.
Test No. 1 refers to the composition of cellulosic fibres derived from pine.
Test Nos. 2 to 4
refer to cellulosic fibre compositions which had been passed through the pearl
mill (MT3)
once and twice, respectively, used for comparison.
Table 8
Test Chem. Mech. Fibre Fines
No. Treat- Treat- Length Content
ment ment [ m] [%]
1 - - 2010 5
2 - MT3 (0.5) 265 53
3 CT2 MT3 (0.5) 600 31
4 CT2 MT3 (1.0) 240 52
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Example 9
Cellulosic fibres of bamboo were subjected to chemical treatment and/or
mechanical
5 treatment and used as additives in the production of paper / board and
analysed. The
results are shown in Table 9, in which the dry solids content (% by weight) of
the cellulosic
fibres in the mechanical treatment is given in parenthesis.
Test No. 1 refers to the pulp suspension when no cellulosic fibre composition
was used as
10 an additive. Test No. 2 refers to the cellulosic fibres derived from pine
used for
comparison. Test Nos. 3 to 5 refer to different cellulosic fibre compositions
used as
additives.
Table 9
Test Chem. Mech. Fibre Fibre Length/ Fines Specific Strength
No. Treat- Treat- Length Width Width Content Surface Contri-
ment ment [ m] [ m] Ratio [%] Area bution
[m2/g] [%]
1 - - - - - - - 0
2 - - 1270 20 64 - 0.3 -1
3 CT2 - 1270 20 64 5 0.6 +3
4 CT2 MT1 (10) 600 23 26 27 3.8 +19
5 CT2 MT1 (15) 585 22 26 27 4.5 +10
Table 9 shows that the use of the compositions comprising cellulosic fibres
according to
the invention in Test Nos. 4-5 resulted in paper / board with significantly
improved tensile
strength index over the compositions comprising cellulosic fibres used for
comparison.
Example 10
Cellulosic fibres of pine were subjected to chemical treatment and/or
mechanical
treatment and used as additives in the production of paper / board and
analysed. The
results are shown in Table 10, in which the dry solids content (% by weight)
of the
cellulosic fibres in the mechanical treatment is given in parenthesis.
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Test No. 1 refers to the pulp suspension when no cellulosic fibre composition
was used as
an additive. Test Nos. 2 to 3 refer to different cellulosic fibre compositions
used as
additives according to the invention.
Table 10
Test Chem. DS Mech. Fibre Fibre Length/ Strength
No. Treat- Treat- Length Width Width Contri-
ment ment [ m] [ m] Ratio bution
[%]
1 - - - - - - 0
2 CT4 0.05 MT1 (40) 750 36 21 +19
3 CT4 0.05 MT1 (45) 490 33 15 +17
Example 11
Cellulosic fibres were subjected to chemical treatment and/or mechanical
treatment and
the obtained compositions were used as additives in the production of paper /
board and
analysed. The results are shown in Table 11, in which the dry solids content
(% by weight)
of the cellulosic fibres in the mechanical treatment is given in parenthesis.
Test No. 1 refers to the pulp suspension when no cellulosic fibre composition
was used as
an additive. Test Nos. 2 to 6 refer to different cellulosic compositions used
as additives.
Table 11
Test Chem. DS Mech. Fibre Fibre Length/ Strength WRV
No. Treat- Treat- Length Width Width Contri- [g/g]
ment ment [ m] [ m] Ratio bution
[%]
1 - - - - - - 0 1.25
2 CT4 0.10 MT4 (1) - - - +46 2.36
3 CT4 0.07 MT1 (50) 780 38 21 +25 1.32
4 CT4 0.08 MT1 (50) 760 38 20 +29 1.34
5 CT4 0.11 MT1 (55) 845 41 21 +18 -
6 CT4 0.23 MT1 (35) 500 51 10 +35 1.88
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Table 11 shows that the use of the compositions comprising cellulosic fibres
of pine in
Test Nos. 3-5 and cotton linter in Test No. 6 according to the invention
resulted in paper /
board with a good balance between improved tensile strength index and low
water
retention values which indicate less energy to remove water and dry the
cellulosic sheet
over the composition according to Test No. 2 used for comparison.
Example 12
Cellulosic fibres were subjected to chemical treatment and/or mechanical
treatment and
the obtained compositions were used as additives in the production of paper /
board and
analysed. The results are shown in Table 12, in which the dry solids content
(% by weight)
of the cellulosic fibres in the mechanical treatment is given in parenthesis.
Water retention values were determined as described above except that the
samples
were made from aqueous pulp suspensions in which the dry pulp consisted of 99,
97 and
95 % by weight of CTMP and 1, 3 and 5 % by weight, respectively, of
composition
comprising cellulosic fibres of pine according to the invention or cellulosic
composition
used for comparison, which is indicated as "Content at WRV Tests" in the table
below.
Test No. 1 refers to the pulp suspension when no cellulosic fibre composition
was used as
an additive. Test Nos. 2 to 4 refer to the cellulosic composition used for
comparison and
Test Nos. 5-7 refer to the cellulosic fibre composition according to the
invention.
Table 12
Test Chem. DS Mech. Fibre Fibre Strength Content WRV
No. Treat- Treat- Length Width Contri- at WRV [g/g]
ment ment [ m] [gm] bution Tests
[%] [%]
1 - - - - - - - 1.25
2 CT4 0.10 MT4 (1) - - +14 1 1.42
3 CT4 0.10 MT4 (1) - - +30 3 1.84
4 CT4 0.10 MT4 (1) - - +46 5 2.36
5 CT4 0.08 MT1 (50) 760 38 +9 1 1.20
6 CT4 0.08 MT1 (50) 760 38 +23 3 1.24
7 CT4 0.08 MT1 (50) 760 38 +29 5 1.34
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Table 12 shows that, at a tensile strength index improvement of paper / board
of about 30
%, the composition of the invention according to Test No.7 resulted in a lower
water
retention value which indicate less energy to remove water and dry the
cellulosic sheet
over the composition used for comparison according to Test No. 3. Table 12
also shows
that, at about the same water retention value, the composition of the
invention resulted in
increased tensile strength index over the composition used for comparison.
Example 13
Cellulosic fibres of various sources were subjected to chemical treatment
and/or
mechanical treatment and the obtained compositions were used as additives in
the
production of paper / board and analysed. The results are shown in Table 13,
in which the
dry solids content (% by weight) of the cellulosic fibres in the mechanical
treatment is
given in parenthesis.
Test No. 1 refers to the pulp suspension when no cellulosic fibre composition
was used as
an additive. Test Nos. 2 to 6 refer to different cellulosic compositions used
as additives.
Table 13
Test Fibre Chem. DS Mech. Fibre Fibre Length/ Strength WRV
No. Type Treat- Treat- Length Width Width Contri- [g/g]
ment ment [ m] [ m] Ratio bution
[%]
1 - - - - - - - 0 1.31
2 Bamboo CT4 0.04 MT1 (45) 900 21 42 +10 1.40
3 Birch CT4 0.04 MT1 (55) 520 26 20 +12 1.42
4 Pine CT4 0.04 MT1 (45) 1035 34 30 +21 1.47
5 Pine CT4 0.07 MT1 (55) 765 37 21 +27 1.57
6 Pine CT4 0.11 MT1 (55) 845 41 21 +18 1.85
Table 13 shows that the use of the compositions comprising cellulosic fibres
according to
the invention in Test Nos. 2-6 resulted in paper / board with significantly
improved tensile
strength index and low retention values.
Example 14
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Cellulosic fibres of various sources were subjected to chemical treatment
and/or
mechanical treatment and the obtained compositions were used as additives in
the
production of paper / board and analysed. The results are shown in Table 14,
in which the
dry solids content (% by weight) of the cellulosic fibres in the mechanical
treatment is
given in parenthesis. Cotton means cotton linter.
Test No. 1 refers to the pulp suspension when no cellulosic fibre composition
was used as
an additive. Test Nos. 2 to 7 refer to different cellulosic fibre compositions
used as
additives. The mechanical treatment MT2* was carried out by feeding the
cellulosic fibre
composition through the planetary roller extruder twice.
Table 14
Test Fibre Chem. DS Mech. Fibre Fibre Length/ Fines Strength
No. Type Treat- Treat- Length Width Width Content Contri-
ment ment [ m] [ m] Ratio [%] bution
[%]
1 - - - - - - - - 0
2 Birch - - MT2 (25) 470 26 18 32 +6
3 Birch - - MT2 (55) 530 28 19 30 +3
4 Birch CT4 0.23 MT2 (40) 905 24 38 8 +14
5 Birch CT4 0.23 MT2 (55) 845 23 37 11 +22
6 Birch CT4 0.23 MT2*(55) 770 22 35 12 +21
7 Cotton CT4 0.23 MT2 (25) 905 43 21 13 +21
8 Cotton CT4 0.23 MT2 (40) 810 44 18 20 +31
9 Cotton CT4 0.23 MT2 (55) 555 44 13 30 +39
10 Cotton CT4 0.23 MT2*(55) 495 43 12 38 +50
11 Pine CT4 0.07 MT2 (55) 805 38 21 24 +22
12 Pine CT4 0.07 MT2*(55) 735 38 19 33 +32
Table 14 shows that the use of the compositions comprising cellulosic fibres
according to
the invention resulted in paper / board with significantly improved tensile
strength index.
