CTMP-PROCESS - European Patent Office

Europaisches Patentamt
European Patent Office
19
Office europeen des brevets
EUROPEAN
12
(TT) Publication number: 0 5 7 2
388
B1
PATENT S P E C I F I C A T I O N
(45) Date of publication of patent specification
10.05.95 Bulletin 95/19
© int. ci.6 : D21B 1/02, D21H 1 1 / 0 2
(2j) Application number : 91904023.8
(22) Date of filing : 11.02.91
(86) International application number :
PCT/SE91/00091
(87) International publication number :
WO 91/12367 22.08.91 Gazette 91/19
(54) CTMP-PROCESS.
(73) Proprietor : Molnlycke AB
S-405 03 Goteborg (SE)
(30) Priority: 13.02.90 SE 9000515
(43) Date of publication of application
08.12.93 Bulletin 93/49
(45) Publication of the grant of the patent :
10.05.95 Bulletin 95/19
@ Designated Contracting States :
AT BE CH DE DK ES FR GB GR IT LI NL SE
(56) References
SE-B- 385
SE-B- 397
SE-B- 404
SE-C- 215
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cited :
719
851
044
417
Inventor : HOGLUND, Hans
Runsvik 1060
S-864 00 Matfors (SE)
Inventor : BACK, Roland
Volframvagen 12
S-860 20 Njurunda (SE)
Inventor : DANIELSSON, Ove
Nybergsgatan 8
S-114 45 Stockholm (SE)
Inventor: FALK, Bo
Avstyckningsvagen 46
S-175 43 Jarfalla (SE)
(74) Representative : Larsson, Karin et al
Albihn Holmqvist AB,
P.O. Box 3137
S-103 62 Stockholm (SE)
Note : Within nine months from the publication of the mention of the grant of the European patent, any
person may give notice to the European Patent Office of opposition to the European patent granted.
Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been
filed until the opposition fee has been paid (Art. 99(1) European patent convention).
Jouve, 18, rue Saint-Denis, 75001 PARIS
EP 0 572 388 B1
Description
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The present invention relates to an absorbent chemithermomechanical pulp and to a method of manufacturing the same.
Hitherto, it has only been possible to apply the process of defibering chips with a low energy input subsequent to preheating the chips under high pressure and high temperature (150-170°C), the so-called Asplund
process, within the board manufacturing industry, since the pulp resulting from this process is dark in colour
and cannot be bleached at reasonable chemical consumptions. Furthermore, the fibres become coated with
a lignin skin and are therefore stiff and rigid, which results in poorer strength and absorption properties. Consequently, it has only been possible to produce chemithermomechanical pulp (CTMP) of high brightness and
good absorbency by preheating and refining at a temperature of at most 140°C. High brightness is especially
important when producing tissue pulp.
DE-A-27 14 730 describes a process for producing a chemically modified thermomechanical pulp where
the wood material is preheated at a temperature of 135-200°C during 1-30 minutes. The time used according
to the examples is of the order of 10 minutes. To obtain the desired flexibility an energy input of twice the normal
is required.
The object of the present invention is to provide a chemithermomechanical pulp which exhibits a low resin
content, an extremely high long-fibre content, an extremely low short-fibre content, and an extremely low shive
content. Such pulps are particularly suited for the manufacture of fluff and tissue. The extremely low shives
content is of special importance when producing tissue pulp. The extremely high long-fiber content with the
corresponding high freenes is of special importance when producing fluff pulp.
A further object of the invention is to provide a novel method for the manufacture of absorbent chemithermomechanical pulps at low energy inputs.
The invention thus relates to an absorbent chemithermomechanical pulp produced from lignocellulosic material at a wood yield above 88%, a resin content beneath 0.15%, calculated on the amount of resin which can
be extracted in dichloromethane, a high long-fibre content, a low short-fibre content and a low shives content,
the pulp being characterized in that when fractionating the pulp according to Bauer McNett, the long-fibre content is above 70%, preferably above 75% of fibres retained on a wire gauze of size 28 mesh and the shortfibre content is beneath 10%, preferably beneath 8%, of fibres which pass through a wire gauze of size 200
mesh according to Bauer McNett; and in that the shive content is lower than 3%, preferably lower than 2%,
measured according to Sommerville.
The pulp should have such brightness that it can be bleached at a reasonable consumption of bleaching
chemicals to a brightness of at least 65 % ISO, preferably 70%. Alternatively the pulp may have been bleached
to such brightness.
This pulp is particularly well suited for the manufacture of fluff and tissue.
When the pulp is a fluff pulp it is preferably refined to a freeness of 740 ml at the lowest especially 750
ml at the lowest and suitably 760 ml CSF at the lowest. Such a pulp does not need to be bleached and may
have a brightness of at least 45 % ISO.
When the pulp is a tissue pulp it has suitably a brightness of at least 65 % ISO, preferably above 70 %.
The tissue pulp does not need to have as high a freenes as the fluff pulp. Suitably it is refined to a freeness
of 650 ml CSF at the lowest.
The problem with manufacturing pulp suitable for fluff and tissue by means of a chemithermomechanical
method lies in the desired combination of high freeness, high long-fibre content, low shive content and high
brightness. An increase in temperature when preheating will favour the reduction in shive content but, at the
same time, impair brightness.
It has now surprisingly been found that a chemithermomechanical pulp having the desired properties can
be produced by
a) impregnating the chips with sodium sulphite, sodium dithionate, alkaline peroxide or the like, with an
addition of a complex builder;
b) preheating the chips;
c) defibering the chips to pulp in a refiner at substantially the same pressure and temperature as those
employed in the preheating process; and
d) washing and dewatering the pulp to, e.g., a consistency of 25-50%,
wherein, in accordance with the invention, impregnation and preheating of the chips is effected in one and the
same vessel over a combined treatment time of at most 2 minutes, and
a) using a warm impregnating liquid having a temperature of at least 130°C,
b) preheating the chips at a temperature of 150-1 75°C, and
c) carrying out the defibering process with an energy input which is at most half of the energy input required
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EP 0 572 388 B1
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for defibering to the same shive content in a similar refiner when preheating and defibering are performed
at 135°C.
The complex builder used in the impregnating process may, for instance, be DTPA, which contributes to
an improvement in pulp brightness.
The pulp may e) be refined to a brightness above 65 % ISO, preferably above 70 %. To accomplish this
at a reasonable consumption of bleaching chemicals the brightness after refining has to be at least 45 % ISO,
preferably at least 50 %. Such bleaching should preferably be performed when the pulp is a tissue pulp.
In order to obtain a pulp of sufficient brightness, it is essential that preheating at the aforesaid high temperature is not permitted to proceed over a period of time of as long a duration as the standard preheating
time of about 3 minutes used when producing chemimechanical pulp of CTMP type. In order to enable the preheating time to be lowered to at most 2 minutes, preferably at most 1 minute, it is necessary to use an impregnating solution which is heated to a temperature of at least 100°C, particularly at least 130°C and preferably
substantially to the same temperature as that used in the preheater. Furthermore, no impregnating liquid shall
be removed between the impregnating and preheating steps. Consequently, impregnation is effected in the
same vessel as that in which the chips are preheated, and at the same pressure and suitably at the same temperature or only a slightly lower temperature. The brightness of the pulp is sustained because of the very short
stay time at the high temperature, so that an excessively large quantity of bleaching chemicals, such as peroxide, will not be required in the following bleaching step. Furthermore, the wood yield obtained in this way is
almost equal to the wood yield obtained when preheating the chips conventionally at 130-140°C. In addition,
when refining to a freeness slightly above 750 ml CSF, the energy input required for the defibering process is
reduced from about 600 kWh/tonne at 130°C to less than 300 kWh/tonne at 170°C. These values have been
obtained in a pilot plant. Commercial values may differ from those obtained at pilot level. The relative differences between the levels for shives content, brightness and energy input obtained in the pilot plant at conventional temperature and at the temperature according to the invention, respectively, should, however, remain
in a commercial plant.
The inventive method suitably includes the conventional steaming, impregnating, preheating, defibering,
washing, screening, washing, possibly bleaching, washing and drying stages. Whereas a conventional impregnating process is carried out with cold liquid in a vessel other than the preheating process, which is carried
out over a period of about 3 minutes and at a temperature of about 130°C, and in which process impregnating
liquid is removed between the impregnating stage and the preheating stage, the impregnating and preheating
processes of the inventive method are combined in one and the same vessel and are carried out at the same
pressure and substantially the same temperature 130-175°C, 150-175°C respectively, over a combined time
period of at most 2 minutes, suitably at most 1 minute and preferably at most 0.5 minute.
Preferably the chips are preheated at a temperature of 160-170°C.
Because preheating is effected at high temperature, the refining process requires less energy. A low energy input will normally result in high freeness and high shive content. Asurprising characteristic of the present
invention is that at low energy inputs, success is achieved in combining high freeness with low shive content.
Low energy input would otherwise result in a high shive content.
When applying the inventive method in tests on a laboratory seal, a freeness of above 780 ml CSF was
achieved with an acceptable shive content. In some instances, a freeness of above 800 ml was achieved. This
can be compared with a freeness of about 650-750 ml CSF in the normal production of CTMP-fluff.
The pulp is washed subsequent to the refining process, suitably under pressure and at high temperature,
preferably while excluding air from the system and in immediate connection with the refining stage. The pulp
is dewatered to a consistency of e.g. 25-50%. Possible bleaching is then carried out with peroxide or other
bleaching chemical. If desired, the pulp can again be washed, after the bleaching process.
When producing fluff, defibering is carried out to a freeness of 740 ml at the lowest, suitably of 750 at the
lowest, preferably of 780 ml CSF at the lowest. When producing tissue pulp the refining may be carried out to
a freenes of 650 ml CSF at the lowest.
When applying the inventive method, it is possible to produce pulp with a wood yield above 88%, preferably
above 90%, a resin content of less than 0.15%, calculated on the amount of resin that can be extracted in dichloromethane, and a brightness above 65% ISO after bleaching.
The invention will now be described in more detail with reference to the following exemplifying embodiments thereof and with reference to the accompanying drawings, in which
Figure 1 illustrates schematically a test plant used in the exemplifying embodiments;
Figure 2 is a diagram showing shive content against energy input at defibering;
Figure 3 is a diagram showing energy at defibering against preheating temperature;
Figure 4 is a diagram showing long-fibre content against energy input at defibering;
Figure 5 is a diagram showing short-fibre content against energy input at defibering;
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Figure 6 is a diagram showing network strength against energy input;
Figure 7 is a diagram showing peroxide consumption against original brightness after defibering;
Figure 8 is a diagram showing brightness after defibering against peroxide consumption; and
Figure 9 is a diagram showing fibre length against energy input after defibering.
Figure 10 is a diagram showing the brightness obtained after defibering against preheating temperature;
and
Figure 11 is a diagram showing brightness after defibering against preheating temperature.
In order to study the possiblity of manufacturing fluff and tissue pulp in a high-temperature variant of a
CTMP-process, there was used a test plant schematically illustrated in Figure 1. The plant was constructed
so that the pulps could be washed in immediate connection with refining at high temperature.
The chips are introduced into the preheater 2 with the aid of the feed screw 1 and are impregnated at the
preheater inlet. The preheated chips are then passed immediately to the refiner 3, where the chips are defibered while supplying water. When starting-up the plant, and when samples shall be taken immediately after
the refining stage, the resultant pulp is passed to the cyclone 4 where samples can be taken in the direction
of arrow 5. The connecting line to the cyclone 4 is then disconnected and the blower line 6 connected instead,
such as to thin the pulp to a consistency of about 3% during transportation to a vessel 7 equipped with a pump
which functions as a mixer. The pulp is then pumped to a level vessel 8 which is connected directly to a screw
press 9. The entire system, from impregnation to dewatering in the screw press, can be pressurized to 1 MPa.
Spruce sawmill chips were used in the tests. The chips were screened on two different screens, to remove
excessively coarse chips and sawdust. The screens had a hole diameter of 35 mm and 8 mm respectively.
The chips were impregnated with 50 kg sodium sulphite and 3 kg DTPA per tonne of chips in all tests, prior to
the preheating, refining and washing stages.
Example
Chips were treated in the plant shown in Figure 1 at different temperatures during the preheating-ref ining
process. The temperature was allowed to vary between 135 and 170°C. The impregnating liquid was subjected
to a heat exchange and brought to the temperature level of the preheater. At each temperature level in the
refiner, the pulp was washed at a temperature of about 10°C beneath the preheated temperature and at a temperature of about 90°C under atmospheric pressure. The stay time in the preheater was maintained as constant
as possible over a period of about 1 minute.
Subsequent to impregnation with the same chemical input as that used for remaining pulps, a CTMP-pulp
was produced in an OVP-20 (Open Vertical Preheater) at a preheating and refining temperature of 135°C, this
pulp being used as a reference pulp.
The results of the tests carried out on the pulps are shown partly in Figures 2-9 and in the following Table.
These show typical results obtained in this pilot plant for some of the parameters of interest for the invention.
The following Table I shows some of the results obtained.
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5
EP 0 572 388 B1
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Tests were also carried out at laboratory level in a 10 litre digester. The chips were steamed at atmospheric
pressure and then impregnated with a weak alkaline sulphite solution before the pressurized steam treatment
at high temperature.
500 g of spruce chips with a dry solids content of 48.1% were steamed at a temperature of 100°C over a
period of 2 minutes. The impregnating solution contained 20 g/l sodium sulphite and 3.2 g/l DTPA and had a
temperature of 100°C. The impregnation was carried out for 1 minute under a nitrogen pressure of 7 bar. After
removal of excess impregnating solution the chips were heated to their respective heating temperatures as
fast as possible. Condensate was drained while heating. The time at each temperature was varied. Thereafter
the chips were cooled in cold water. These chips were then refined and tested for brightness.
The results obtained are shown in the following Table II and on the Figures 10 and 11.
Table
15
II
Analysis
Preheating
Data
Preheating
°C
temperature
min.
time,
20
Sample
K 21/90
0
Brightness
% ISO
58.3
58.3
01
58.3
2
A2
62.6
10
A5
58.2
1/2
B1
60.7
2
B2
60.0
10
B5
54.1
2
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54.5
10
Cc5
49.5
1/2
Dx
54.1
2
D2
51.3
10
Dc
46.6
—
25
135
30
150
35
160
40
170
45
50
Claims
1.
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An absorbent chemithermomechanical pulp produced from lignocellulosic material at a wood yield above
88%, a resin content beneath 0.15%, calculated as the amount of resin that can be extracted in dichloromethane, a high long-fibre content, a low short-fibre content and a low shives content, the mass having
such a brightness that it can be bleached with peroxide to a brightness of at least 65 % ISO, preferably
at least 70 %, characterized in that when f ractioning according to Bauer McNett, the long-fibre content
is above 70% of fibres retained on a wire gauze of size 28 mesh and the short-fibre content is beneath
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10% of fibres which pass through a wire gauze of size 200 mesh; and in that the shive content is lower
than 3% measured according to Sommerville.
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2.
A pulp according to Claim 1, characterized in that the long fibre content is above 75%.
3.
A pulp according to Claim 1 or 2, characterized in that the short fibre content is beneath 8%.
4.
A pulp according to Claims 2-3, characterized in that the long fibre content is above 78% and the short
fibre content is below 6%.
5.
A pulp according to any one of Claims 1-4, characterized in that the shive content is lower than 2 %.
6.
A pulp according to any one of Claims 1-5, characterized in that it is a fluff pulp and is refined to a freeness
of 740 ml CSF at the lowest.
7.
A pulp according to Claim 6, characterized in that it is refined to a freeness of 750 ml CSF at the lowest.
8.
A pulp according to Claim 7, characterized in that it is refined to a freeness of 760 ml CSF at the lowest.
9.
A pulp according to any one of Claims 1-5, characterized in that it is a tissue pulp and is refined to a
freeness of 650 ml CSF at the lowest.
10. A pulp according to any one of Claims 1-5 and 9, characterized in that it is a tissue pulp and that the
brightness is above 65 % ISO, preferably above 70 %.
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11. A method for producing an absorbent chemithermomechanical pulp from lignocellulosic material consisting of wood chips at a wood yield above 88%, by
a) impregnating the chips with sodium sulphite, sodium dithionate, alkaline peroxide or the like, with
an addition of a complex builder;
b) preheating the chips;
c) defibering the chips to pulp at substantially the same pressure and temperature as those employed
in the preheating process; and
d) washing and dewatering the pulp to, e.g, a consistency of 25-50%;
wherein, in accordance with the invention, impregnation and preheating of the chips are effected in one
and the same vessel over a combined time period of at most 2 minutes;
a) using a warm impregnating liquid having a temperature of at least 130°C;
b) preheating the chips at a temperature of 150-175°C; and
c) carrying out the defibering process with an energy input which is at most half of the energy input
required for defibering to the same shive content when the preheating and defibering are carried out
at 135°C.
12. A method according to Claim 11, characterized in the impregnating liquid having essentially the same
temperature as is employed in the preheating process.
13. A method according to Claim 11 or 12, characterized in that steps a) and b) are effected over a combined
time period of at most 1 minute.
14. A method according to Claim 13, characterized in that steps a) and b) are effected over a combined time
period of at most 0.5 minute.
15. Amethod according to any one of Claims 11-14, characterized in b) preheating the chips at a temperature
of 160-1 70°C.
16. A method according to any one of Claims 11-15, characterized in that the pulp is bleached.
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17. A method according to any one of Claims 11-15, characterized by defibering a fluff pulp to a freeness
of 740 ml CSF at the lowest.
18. Amethod according to Claim 17, characterized by defibering a fluff pulp to a freeness of 750 ml CSF at
the lowest.
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19. A method according to Claim 18, characterized by defibering a fluff pulp to a freeness of 760 ml CSF at
the lowest.
20. Amethod according to any one of Claims 11-16, characterized in that a tissue pulp is defibered to a freeness of 650 CSF at the lowest.
21. Amethod according to Claim 11,16 and 20, characterized in that a tissue pulp is bleached with peroxide
or similar bleaching chemicals to a brightness of at least 65 % ISO.
22. A method according to Claim 21 , characterized in that the tissue pulp is bleached to a brightness of at
least 70 % ISO.
23. A method according to any one of Claims 11-22 characterized by washing the pulp according to step d)
under pressure at high temperature, preferably at 150-170°C.
24. Amethod according to any one of Claims 11-23, characterized by washing the pulp according to step d)
while excluding air from the system.
Patentanspruche
1.
Absorbierende chemithermomechanische Pulpe hergestellt aus Lignozellulosematerial mit einer Holzausbeute oberhalb 88 %, einem Harzgehalt unterhalb 0,15 %, berechnet als Menge des Harzes, die in Dichlormethan extrahiert werden kann, einem hohen Gehaltan langen Fasern, einem niedrigen Gehaltan
kurzen Fasern und einem niedrigen Gehalt an Splittern, wobei die Pulpe eine solche Helligkeit hat, dali
man sie mit Peroxid zu einer Helligkeit von wenigstens 65 % ISO, vorzugsweise wenigstens 70 %, bleichen
kann,
gekennzeichnet dadurch, daft beim Fraktionieren gemali Bauer McNett der Gehalt an langen Fasern,
die auf einem Drahtnetz der Grolie 28 Mesh zuruckgehalten werden, oberhalb 70 % der Fasern, betragt
und der Gehalt an kurzen Fasern, die durch ein Drahtnetz der Grolie 200 Mesh gehen, unterhalb 70 %
der Fasern, betragt und dali der Gehalt an Splittern niedriger als 3 %, gemessen gemali Sommerville,
ist.
2.
Pulpe gemali Anspruch 1, dadurch gekennzeichnet, dali der Gehalt an langen Fasern oberhalb 75 % ist.
3.
Pulpe gemali Anspruch 1 oder 2, dadurch gekennzeichnet, dali der Gehalt an kurzen Fasern unterhalb
8 % ist.
4.
Pulpe gemali einem der Anspruche 2 bis 3, dadurch gekennzeichnet, dali der Gehalt an langen Fasern
oberhalb 78 % und der Gehalt an kurzen Fasern unterhalb 6 % ist.
5.
Pulpe gemali einem der Anspruche 1 bis 4, dadurch gekennzeichnet, dali der Splittergehalt niedriger als
2 % ist.
6.
Pulpe gemali einem der Anspruche 1 bis 5, dadurch gekennzeichnet, dali es eine Flockenpulpe ist, die
bis zu einem Mahlgrad von 740 ml CSF im niedrigsten Fall raffiniert ist.
7.
Pulpe gemali Anspruch 6, dadurch gekennzeichnet, dali sie bis zu einem Mahlgrad von 750 ml CSF im
niedrigsten Fall raffiniert ist.
8.
Pulpe gemali Anspruch 7, dadurch gekennzeichnet, dali sie bis zu einem Mahlgrad von 760 ml CSF im
niedrigsten Fall raffiniert ist.
9.
Pulpe gemali einem der Anspruche 1 bis 5, dadurch gekennzeichnet, dali es eine Seidenpapierpulpe
(tissue pulp) ist, die bis zu einem Mahlgrad von 650 ml CSF im niedrigsten Fall raffiniert ist.
10. Pulpe gemali einem der Anspruche 1 bis 5 und 9, dadurch gekennzeichnet, dali sie eine Seidenpapierpulpe ist und dali die Helligkeit oberhalb 65 % ISO, vorzugsweise oberhalb 70 % ist.
11. Verfahren zur Herstellung einer absorbierenden chemithermomechanische Pulpe aus Lignozellulosema8
EP 0 572 388 B1
terial bestehend aus Hackspane mit einem Holzausbeute oberhalb 88 % durch:
a) Impragnieren derSpane mit Natriumsulfit, Natriumdithionat, alkalischem Peroxid oder dergleichen
unter Zugabe eines Komplexbildners;
b) Vorerhitzen der Spane;
c) Zerfasern der Spane zu Pulpe bei im wesentlichen dem gleichen Druck und der Temperatur, wie sie
im Vorerhitzungsverfahren angewendet wurden; und
d) Waschen und Entwassern der Pulpe auf beispielsweise eine Konsistenz von 25 bis 50 %,
wobei erf indungsgemali das Impragnieren und Vorerhitzen der Spane in ein und demselben Gefali uber
einen Gesamtzeitraum von hochstens 2 Minuten bewirkt wird;
a) unter Verwenden einer warmen Impragnierflussigkeit mit einer Temperatur von wenigstens 130°C;
b) unter Vorerhitzen derSpane auf eine Temperatur von 150 bis 175°C; und
c) unter Durchf uhren des Zerfaserungsverfarhrens mit einem Energiaufwand, der hochstens der Half te
des Energieaufwands entspricht, dererforderlich ist, urn auf den gleichen Splittergehaltzu zerfasern,
wenn das Vorerhitzen und Zerfasern bei 135°C durchgefuhrt wird.
5
10
15
20
12. Verfahren gemali Anspruch 11, dadurch gekennzeichnet, dali die Impragnierflussigkeit im wesentlichen
die gleiche Temperatur hat wie die bei der Vorerhitzung verwendete.
13. Verfahren gemali Anspruch 11 oder 12, dadurch gekennzeichnet, dali die Stufen a) und b) uber einen
Gesamtzeitraum von hochstens 1 Minute durchgefuhrt werden.
14. Verfahren gemali Anspruch 13, dadurch gekennzeichnet, dali die Stufen a) und b) uber einen Gesamtzeitraum von hochstens 0,5 Minuten durchgefuhrt werden.
25
15. Verfahren gemali einem der Anspruche 11 bis 14, gekennzeichnet durch b) Vorerhitzen der Spane auf
eine Temperatur von 160 bis 170°C.
16. Verfahren gemali einem der Anspruche 11 bis 15, dadurch gekennzeichnet, dali die Pulpe gebleicht ist.
30
17. Verfahren gemali einem der Anspruche 11 bis 15, gekennzeichnet durch Zerfasern einer Flockenpulpe
auf einen Mahlgrad von 740 ml CSF in niedrigsten Fall.
18. Verfahren gemali Anspruch 17, gekennzeichnet durch Zerfasern einer Flockenpulpe auf einen Mahlgrad
von 750 ml CSF in niedrigsten Fall.
35
19. Verfahren gemali Anspruch 18, gekennzeichnet durch Zerfasern einer Flockenpulpe auf einen Mahlgrad
von 760 ml CSF in niedrigsten Fall.
20. Verfahren gemali einem der Anspruche 11 bis 16, dadurch gekennzeichnet, dali eine Seidenpapierpulpe
auf einen Mahlgrad von 650 CSF im niedrigsten Fall zerfasert wird.
40
45
50
21. Verfahren gemali den Anspruchen 11, 16 und 20, dadurch gekennzeichnet, dali eine Seidenpapierpulpe
mit Peroxid oder einem ahnlichen Bleichmittel auf eine Helligkeit von wenigsten 65 % ISO gebleicht wird.
22. Verfahren gemali Anspruch 21 , dadurch gekennzeichnet, dali die Seidenpapierpulpe auf eine Helligkeit
von wenigstens 70 % ISO gebleicht wird.
23. Verfahren gemali einem der Anspruche 11 bis 22, gekennzeichnet durch Waschen der Pulpe gemali Stufe
d) unter Druck bei einer hohen Temperatur, vorzugsweise bei 150 bis 170°C.
24. Verfahren gemali einem der Anspruche 11 bis 23, gekennzeichnet durch Waschen der Pulpe gemali Stufe
d) unter Ausschluli von Luft aus dem System.
Revendications
55
1.
Pate chimiothermomecanique absorbante, produite a partir d'une matiere lignocellulosique avec un rendement, par rapport au bois, superieura 88% et presentant une teneur en resine inferieure a 0.15%, cette
teneur etant indiquee par la quantite de resine qui peut etre extraite dans du dichloromethane, une teneur
elevee en fibres longues, une faible teneur en fibres courtes et une faible teneur en buchettes, la pate
EP 0 572 388 B1
ayant une blancheur telle qu'on peut la blanchiravec du peroxyde de facon a ce qu'elle atteigne une blancheur d'au moins 65% ISO de preference d'au moins 70% ISO, caracterisee en ce que, lorsqu'on fractionne la pate selon Bauer McNett, on trouve une teneur en fibres longues superieure a 70% de fibres
retenues sur une toile metallique de calibre 28 mesh et une teneur en fibres courtes inferieure a 10% de
fibres passant a travers une toile metallique de calibre 200 mesh, et en ce que la teneur en buchettes,
mesuree selon Sommerville, est inferieure a 3%.
5
10
15
20
25
3o
30
35
40
45
50
55
2.
Pate selon la revendication 1, caracterisee en ce que la teneur en fibres longues est superieure a 75%.
3.
Pate selon la revendication 1 ou 2, caracterisee en ce que la teneur en fibres courtes est inferieure a 8%.
4.
Pate selon la revendication 2 ou 3, caracterisee en ce que la teneur en fibres longues est superieure a
78% et la teneur en fibres courtes est inferieure a 6%.
5.
Pate selon I'une quelconque des revendications 1 a 4, caracterisee en ce que la teneur en buchettes est
inferieure a 2%.
6.
Pate selon I'une quelconque des revendications 1 a 5, caracterisee en ce qu'elle est une pate fluff et est
raff inee jusqu'a I'obtention d'un degre de raff inage de 740 ml CSF au moins.
7.
Pate selon la revendication 6, caracterisee en ce qu'elle est raff inee jusqu'a I'obtention d'un degre de raff inage de 750 ml CSF au moins.
8.
Pate selon la revendication 7, caracterisee en ce qu'elle est raff inee jusqu'a I'obtention d'un degre de raff inage de 760 ml CSF au moins.
9.
Pate selon I'une quelconque des revendications 1 a 5, caracterisee en ce qu'elle est une pate pour papier
de soie et est raff inee jusqu'a I'obtention d'un degre de raff inage de 650 ml CSF au moins.
10. Pate selon I'une quelconque des revendications 1 a 5 et 9, caracterisee en ce qu'elle est une pate pour
papier de soie et en ce que la blancheur est superieure a 65% ISO, de preference superieure a 70% ISO.
11. Precede de production d'une pate chimiothermomecanique absorbante, a partir d'une matiere lignocellulosique constitute de copeaux de bois, avec un rendement, par rapport au bois, superieur a 88%, par:
a) impregnation des copeaux avec du sulfite de sodium, du dithionate de sodium, un peroxyde alcalin
ou un produit similaire, un agent de renforcement complexe etant ajoute lors de I'impregnation,
b) prechauffage des copeaux.
c) defibrage des copeaux pour I'obtention d'une pate, a pratiquement la meme pression et la meme
temperature que celles utilisees dans le precede de prechauffage, et
d) lavage de la pate et elimination d'eau de la pate jusqu'a obtention, par exemple, d'une consistance
de 25 a 50%,
dans lequel, conformement a I'invention, on realise I'impregnation et le prechauffage des copeaux
dans un seul et meme recipient, en un laps de temps combine de 2 minutes au plus, et :
a) on utilise un liquide d'impregnation chaud, ayant une temperature d'au moins 130°C,
b) on prechauffe les copeaux a une temperature de 150 a 175°C, et
c) on realise le defibrage avec un apport d'energie qui represents au plus la moitie de I'apport d'energie
necessaire pour le defibrage avec I'obtention de la meme teneur en buchettes lorsqu'on effectue le
prechauffage et le defibrage a 135°C.
12. Precede selon la revendication 11, caracterise en ce que le liquide d'impregnation a pratiquement la meme
temperature que celle employee pendant I'operation de prechauffage.
13. Precede selon la revendication 11 ou 12, caracterise en ce que Ton realise les etapes a) et b) en un laps
de temps combine de 1 minute au plus.
14. Precede selon la revendication 13, caracterise en ce que Ton realise les etapes a) et b) en un laps de
temps combine de 0,5 minute au plus.
15. Precede selon I'une quelconque des revendications 11 a 14, caracterise en ce que, dans I'etape b), on
prechauffe les copeaux a une temperature de 160 a 170°C.
10
EP 0 572 388 B1
16. Pro-cede selon I'une quelconque des revendications 11 a 15, caracterise en ce que la pate est blanchie.
17. Precede selon I'une quelconque des revendications 11 a 15, caracterise en ce que Ton realise le defibrage
d'une pate fluff, de facon a obtenir un degre de raffinage de 740 ml CSF au moins.
18. Precede selon la revendication 17, caracterise en ce que Ton realise le defibrage d'une pate fluff de facon
a obtenir un degre de raffinage de 750 ml CSF au moins.
19. Precede selon la revendication 18, caracterise en ce que Ton realise le defibrage d'une pate fluff, de facon
a obtenir un degre de raffinage de 760 ml CSF au moins.
20. Precede selon I'une quelconque des revendications 11 a 16, caracterise en ce que Ton realise le defibrage
d'une pate pour papier de soie, de facon a obtenir un degre de raffinage de 650 ml CSF au moins.
21. Precede selon I'une quelconque des revendications 11, 16 et 20, caracterise en ce que Ton blanchit une
pate pour papier de soie avec du peroxyde ou des agents de blanchiment semblables, de facon a obtenir
une blancheur d'au moins 65% ISO.
22. Precede selon la revendication 21 , caracterise en ce que Ton blanchit la pate pour papier de soie de facon
a obtenir une blancheur d'au moins 70% ISO.
23. Precede selon I'une quelconque des revendications 11 a 22, caracterise en ce que, conformement a I'etape d), on lave la pate sous pression, a une temperature elevee, de preference a une temperature de 150
a 170°C.
24. Precede selon I'une quelconque des revendications 11 a 23, caracterise en ce que, conformement a I'etape d), on lave la pate en eliminant I'air du systeme.
11
EP 0 572 388 B1
12
EP 0 572 388 B1
SHIVES
CONTENT
AFTER
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TEMPERATURE
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TEMF'ERATURE
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140
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PREHEATING TEMP
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EP 0 572 388 B1
LONGFIBER CONTENT
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EP 0 572 388 B1
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FIG. 7
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EP 0 572 388 B1
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EP 0 572 388 B1
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