Note: Descriptions are shown in the official language in which they were submitted.
CA 02467305 2004-05-14
M~~31UM F~R INCREASING THE A,SSORPT1~N
CAPACITY OF PAPER Pt3LP F~R STARCH
The present invention relates to a means for increasing the absorption
capacity of paper
pulp, such as is used in paper manufacture, for starch or starch-containing
products.
The present invention is suitable for use in conventional methods of producing
paper,
paperboard or cardboard and for devices usually used for this purpose, which
devices are
generally known.
The present invention is especially suitable for manufacture from waste paper.
As a starting material for paper manufacture, an aqueous suspension is
prepared from the
starting materials such as the fibrous constituents and optionally other paper
auxiliaries.
The aqueous suspension will hereinafter be referred to as the fibre slurry,
and the solid
materials contained therein as the paper pulp.
For the purpose of improving properties such as the resistance of paper to
tearing during
the manufacturing process, it is known to add starch as a sizing agent to
paper pulp from
which sheet paper is ultimately obtained.
For paper manufacture, the fibre slurry containing the paper pulp - as yet
without the
starch additive - in suspension, is introduced in the form of a web on to a
band-like sieve
which contains dewatering elements. After partial dewatering, the web passes
through a
so-called sizing press, in which the application of starch to the already
partially dried web
takes place. In this operation, the starch is applied as an aqueous
suspension, with the
result that the moisture content and thus the drying necessary to achieve the
finished,
dried paper web is increased.
It would therefore be desirable to already add the starch to the fibre slurry.
By this
means, the sizing press and the supplementary drying measurers could be
dispensed with,
as a result of which the equipment and the time required to produce the paper,
and thus
CA 02467305 2004-05-14
the cost, could be crucially reduced. Adding the starch to the fibre slurry
has already
been experimented with. However, the starch proved to be only inadequately
absorbed
by the paper pulp, with the result that the starch content of the paper web
obtained is too
low to achieve the desired effects, in particular increasing the resistance to
tearing.
The aim of the present invention was therefore to make it possible to already
add starch
to the fibre slurry so that the resulting paper web has a starch content
sufficiently high to
enable the sizing press and the associated process control which is also
necessary to be
dispensed with during paper manufacture.
According to the invention, this aim is achieved with a medium for increasing
the absorp-
tion capacity of paper pulp for starch, which medium contain:> cereal meal
and/or starch
and a polymer with vinylamine units, and is obtainable by mixing the cereal
meal andlor
the starch and the polymer with vinylamine units in an extruder.
The invention further relates to a method of paper manufacture in which a
medium con
taming cereal meal and/or starch and a polymer with vinylamme units is added
to the
fibre slurry.
The invention also relates to the use of a medium containing cereal meal
and/or starch
and a polymer with vinylamine units for increasing the starch content of the
paper pulp,
particularly in the fibre slurry.
Cereal meals contain a high proportion of starch, with possible variation in
the proportion
and composition of the starch depending on the cereal type.
The meal preferably used according to the invention is a rye meal or a meal of
a type of
cereal in which the proportion and composition of the starch corresponds to or
is similar
to that of rye.
The meal may be a commercially available meal.
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3
Preferably-used starches are rye-meal starch, or a starch which, in its
composition, in
particular its content of amylose and amylopectin, corresponds to or is
similar to that of
rye starch.
The cereal meal and/or the starch may be added to the medium according to the
invention
in each case either in the pure form or as a mixture.
The medium according to the invention additionally contains a polymer with
vinylamine
units.
This may be a homopolymer or a copolymer.
These may be obtained in a way which is known per se, by radical
polymerisation of N-
vinylcarboxylic acid amides and subsequent at least partial hydrolysis of the
amide func-
tional group to form the corresponding amine functional group.
Examples of suitable monomers arid comonomers, and methods of producing
polymers
with vinylamine units may be found in EP 0 553 135 BI, EP 0 758 344 B1,
WO 98/45536 and WO 00/60 i 67, which for this purpose are referred to in their
entirety.
Suitable polymers with vinylamine units are polymers obtained by
polymerisation of N
vinylcarboxylic acid amides of the formula
R
CH = CH ~ I
2
C-Ri
O
wherein R, Rl = H or C1 to C6-alkyl, alone or in the presence of other
therewith
copoIymerisable monomers, and hydrolysis of the resulting polymers with acids
or bases
with cleavage of the group
- C - RI (II),
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and with formation of the vinylarnine units of the formula
- CHa - CH -
H R
wherein R has the meaning assigned in formula (I).
Suitable formula (1) monomers are, for example, N-vinylformamide, N-vinyl-N-
methyl-
formamide, N-vinyl-N-ethylformamide, N-vinyl-N-propylformamide, N-vinyl-N-
isopropylformamide, N-vinyl-N-butylformamide, N-vinyl-N-sec.butylformamide, N-
vinyl-N-tert.butylformamide, N-vinyl-N-pentylformamide, N-vinylacetamide, N-
vinyl-
N-ethylacetamide and N-vinyl-N-methylpropionamide, N-vinylacetamide, N-vinyl-N-
methylacetamide, N-vinyl-N-ethylacetarnide, N-vinylpropionarnide, N-vinyl-N-
methyl-
propionamide and N-vinylbutyramide.
N-vinyl formamide
CHZ = CH-NC {O) H (I'),
H
is preferably used according to the invention.
Copolymers of monomers (I) and {I') contain, for example,
1) 99 to 1 mol-% of N-vinylcarboxylic acid amides of formu:Ia (I), and
2) 1 to 99 mol-% of other, therewith copolymerisable, monoethylenically
unsaturated
' monomers.
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Examples of copolymerisable, monoethylenically unsaturated monomers are vinyl
formiate, vinyl acetate, vinyl propionate, N-vinylpyrrolidone, acrylic acid,
methacrylic
acid, esters, amides and nitrites of acrylic acid or methacrylic acid, and the
C1- to C4-
alkyl vinyl ethers.
Preferred polymers with vinylamine units are hydrolysed copolymers of
1 ) N-vinyl formamide (I' ) and
2) Vinyl formiate, vinyl acetate, vinyl propionate, acrylonitrile and N-
vinylpyrrolidone,
as well as hydrolysed hornopolymers of N-vinylformami.de.
The degree of hydrolysis of the N-vinylformamide units in the homapolymers and
copolymers is 2 to 100%, preferably 30 to 100%, and especially 75 to 100 mot-
%. The
molar mass of the polymers with vinylamine units has a value of up to 1
million, and is
preferably within the range 10 000 to 600 000 and especially preferably within
a range of
400 000 to 500 000 (determined by light scatter).
Homopolyrners, especially of N-vinyl formamide, are preferably used according
to the
invention.
The preferred homopolymers are completely hydrolysed. As defined by the
invention,
the term "completely hydrolysed" also includes substantially completely
hydrolysed
polymers in the sense that, although the hydrolysis should theoretically run
to comple-
tion, there may be departures therefrom which process controls render
unavoidable.
Polyvinylamines which are especially preferred according to t:he invention are
com-
pletely, or substantially completely, hydrolysed homopolymers of N-vinyl
forrnamide as
monomers having a molar mass within a range from 400 000 to 500 000.
A suitable example thereof is marketed by the company BASF under the product
designation CATIOFAST VFH.
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The medium according to the invention preferably contains 5 to 30 wt%,
especially IO to
25 wt%, of polymers with vinylamine units (with reference to the native meal
with its
natural water content).
According to requirements, the medium may also contain a larger or smaller
quantity of
polymer with vinyiamine units, provided that the fibre slurry is guaranteed to
have the
desired starch content.
If the cereal meal is wholly or partially replaced by starch, the content data
must be
adjusted accordingly.
The medium according to the invention may also contain water, which either
originates
from the natural content of the meal or of the starch and/or was added in the
course of the
manufacturing process and was incompletely removed during subsequent drying.
According to requirements, the medium according to the invention may contain
additives
which may be desirable for paper manufacture.
The medium according to the invention may be obtained by intimate mixing of
the ingre-
dients, meal and/or starch, polymer with vinylamine units, wal,er if
applicable and option-
ally othex additives.
The mixing preferably takes place in an extruder.
One extruder which is suitable for the extrusion is a co-rotating twin-screw
extruder. An
example of a suitable twin-screw extruder is an extruder such as that marketed
by the
company Biihler under the product designation BCTA.
The extruder may be coupled to a preconditioner.
The extrusion usually takes place at a temperature of 100 to 170 °C,
especially of 130 to
1455 °C.
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7
The extrusion preferably takes place during addition of water. The water may
be added
in the liquid state or also at least partially as vapour, for example via a
preconditioner.
The water is usually added in a quantity of up to 30 wt%, preferably 5 to 20
wt%, with
reference to the meal and/or starch content.
The product obtained by extrusion may then be converted into a form suitable
far use.
For example, it may be milled to form a granulate. Beyond this, the particle
size of the
granulate is not critical. It is usually of the order of 0.5 to a few
millimetres, for example
of the order of 0.75 mm.
If required, the extrudate, like the granulate, may be subjected to drying.
The drying pre
ferably precedes cooling of the extrudate. The drying with cooling may be
carried out in
the usual way, which is known per se.
A medium which is preferred according to the invention is obtained by
extrusion of rye
meal with 10 to 25 wt% of polymer with vinylamine units, preferably with
addition of 5
to I 5 wt% of water, in each case with reference to the rye-meal content.
The granulate, which contains starch and/or a cereal meal modified with a
polymer with
vinylamine units, is added to the fibre slurry for paper manufacture in a
quantity
sufficient to adjust the starch content of the paper pulp to the desired
value.
It has been demonstrated that the paper pulp is capable of excellent retention
of the starch
and/or cereal meal modified with a polymer with vinylamine units, yielding a
paper web
which has the starch content required for adequate tear resistance. The
addition of starch
via a sizing press can therefore be dispensed with according to the invention.
In the case of a medium according to the invention which contains rye meal,
addition of a
quantity corresponding to 3 to 5 wt% of rye meal with reference to the fibre
slurry is
sufficient.
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The invention also comprises an improved method of paper manufacture, in which
an
adequate starch content of the paper pulp may be adjusted as early as in the
fibre slurry,
with the result that application of the starch to the paper weh with the use
of a sizing
press may be dispensed with. To this end, medium according; to the invention
is added to
the fibre slurry with the paper pulp for paper manufacture in a quantity
sufficient to
adjust the desired starch content in the paper web to be produced or the
finished paper
web. If, for example, a preferred medium according to the invention is used,
which is
obtained by extrusion of rye meal with 10 to 2S wt% of polymer with vinylamine
units, it
is sufficient to add a quantity corresponding to 3 to S wt% of rye meal (with
reference to
the fibre slurry).
In what follows, the preparation of the medium according to the invention will
be
explained in greater detail with the use of examples.
A conventional rye meal and, as the polymer With vinylamine; units, CATIOFAS.T
VFH
of the company BASF were used for carrying out the examples.
All runs of experimental series 1 to 4 were carried out with a Biihler BCTG
extruder with
a co-rotating twin screw.
In experimental series 2 to 4, a Buhler BCTC preconditioner was connected
upstream of
the extruder, via which preconditioner the individual ingredients were fed to
the extruder.
In selected runs, water in the form of water vapour was additionally fed in
via the precon-
ditioner (reported separately).
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9
Definitions:
N Screw speed (rpm)
WW Added water [wt%]
PC Preconditioner
Polymer Polymer with ~inylamine units [wt%], with
reference to the meal content
Rye meal with its natural water content was used for the series of
experiments.
E~erimental series l:
Parameter i Variation
Extruder design series: Housing diameter (extruder) constant
DNDL at
L/D 40
Meal throughput [kg/h] Constant at 50
Polymer [wt%] 10; 17.5; 25
N [rpm] 100; 85; 70
WW [wt%] 5; 10; 15
Conduct of the experiment:
Polymer10 17.5 25
~VW/N 100 100 85 70
85
100
85
70
15 1 6 8
3 4 5
5 2 7 9
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i0
Run 1 2 3 4 5 6 7 8 9
N [rpm] 100 100 85 85 85 100 100 70 70
Pulp pressure [bar]45 ~ 50 55 51 50 40 50 50 65
Extrusion temperature145 165 151 136 138 136 148 126 138
[C]
Cutter speed [%] 50
H20 ext. [kg/b] 7.5 2.5 5 5.2 5 7.5 2.5 7.5 2.5
Polymer ext. [kglh]5.1 5.1 5.1 8.7 12.5 12.512.5 12.512.5
The throughput of the mixture of meal, water and polymer through the extruder
was a
constant 50 kg/h far runs 1 to 9.
In runs 1 to 9, the water and polymer fraction was added in taro batches to
the mixture to
be extruded, part being added prior to introduction into the extruder and part
being added
to the mixture in the extruder, in the above table described as "H20 ext." and
" polymer
ext." In this series, the" polymer ext." was added via housing 2 and the "H20
ext." via
housing 1 of the extruder, which comprised 5 housings.
Experimental series 2:
In the runs shown here, the rye meal was introduced at a constant rate of 200
kglh. The
polymer was introduced at a constant 10 wt% of the introduced meal (20 kg/h).
In runs 4, 5, 6 and 7, water was added in the form of water vapour. In the
runs with the
switch in the "off' position, water (liquid) and polymer, but no water vapour,
were
introduced via the preconditioner.
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11
The runs were conducted as follows:
PC off > 95 C
N WW 10 15 0 5 10
150 8 6 7
200 2 3 5 4
250 1
Run 1 2 3 4 5 6 7 8
N [rpm] 250 200 200 200 200 150 150 150
Torque [%] 45 54 46 31 3fi 41 35 49
Pulp pressure 69 87 70 36 40 50 44 64
Extrusion temperature15S I 147 146 155 152 148 159
[C] i 1S5
PC temperature [C] - - - 98 9S~ 99 99 100
Rye meal [kg/h] 200
Water [%] 10 10 15 10 5 5 10 -
Polymer [%] ~ 10 10 10 10 10 10 10 10
~ ~ ~ ~ ~ ( ~
The granulated extntdate was dried and cooled, during which operation it was
collected
in a drier (Biihler OTW 50) for 5 minutes, kept in the drier for a further 5
minutes and
then transferred to a cooler. After cooling to room temperature, the granulate
was
decanted.
Experimental series 3:
PC off > 95
C
N WW 5 10 15 ID 5
10
150 17 16 15 19 20
21
200 13 14 18
250 10 11 12 9 23 24
Run 9 10 11 12 13 14 15 I6 17
N [rpm] 250 250 250 250 200 200 150 150 150
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Torque[%] 32 36 42 32 39 35 50 57 58
Pulp pressure 90 124 57 104 I04 91 87 116 I28
I
Extrusion temperature134 163 168 154 149 140 135 146 I58
[C]
PC temperature
[C] -
Rye meal [kg/h] 200
Water [%) 15 5 5 5 10 10 15 5 5
Polymer (%] 10 10 15 15 I~ 5 10 15 10
~ ~ ~
Run 18 19 20 23 22 23
N [rpm] 200 I50 150 I50 250 250
Torque[%] 29 43 38 33 33 28
Pulp pressure 46 61 60 47 47 47
Extrusion temperature146 156 150 144 173 165
[C]
PC temperature 95 98 98 98 9!3 99
[C]
Rye meal (kg/h] _ _ -
-. _
Water [%] 5 - - 10 - -
Polymer (%] 15 10 I5 10 10 15
The drying and cooling of the extruded granulate was performed as in
experimental
series 2.
Experimental series 4:
The addition of meal was varied for experimental series 4.
No. 24 Polymer: 10% 250 kglh 150 rpm
No. 25 Polymer: 10% 300 kg/h 200 rpm
I~To. 26 Polymer: 10% 400 kg/h 250 rpm
Run 24 25 26
N [rpm] 150 200 250
Torque[%] 48 46 55
Pulp pressure 61 63 78
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a
13
Extrusion temperature151 154 15'7
[C]
PC temperature 95 93 89
[C]
Rye meal [kg/h] 250 300 400
Water [%] 5 5 5
Polymex (%] 10 10 IO
The drying and cooling of the granulated extrudate was as in the previous
experimental
serves.
The results showed that, by addition of the granulates obtained in
experimental series 1 to
4, the starch content of the paper pulp in a fibre slurry for paper
manufacture could be
adjusted to the desired value without difficulty, with the result that a paper
with good
resistance to tearing could be obtained without the need to add further starch
via a sizing
press as a supplementary measure.
With the aid of the present invention, therefore, the sizing press and the
equipment
connected downstream thereof, such as drying elements, may be completely
dispensed
with, with the result that significantly more simple and cheaper machinery for
paper
manufacture is feasible.
