Canadian Patents Database / Patent 2230315 Summary

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(12) Patent Application: (11) CA 2230315
(54) English Title: PROCESS FOR INCREASING MECHANICAL WOOD PULP BRIGHTNESS IN A REFINER
(54) French Title: METHODE POUR AUGMENTER LE DEGRE DE BLANCHEUR DE LA PATE MECANIQUE DANS UN RAFFINEUR
(51) International Patent Classification (IPC):
  • D21C 9/10 (2006.01)
  • D21B 1/16 (2006.01)
  • D21C 9/16 (2006.01)
(72) Inventors (Country):
  • LEDUC, CELINE (Canada)
  • DANEAULT, CLAUDE (Canada)
  • SAIN, MOHINI M. (Canada)
(73) Owners (Country):
  • LEDUC, CELINE (Canada)
  • DANEAULT, CLAUDE (Canada)
  • SAIN, MOHINI M. (Canada)
(71) Applicants (Country):
  • LEDUC, CELINE (Canada)
  • DANEAULT, CLAUDE (Canada)
  • SAIN, MOHINI M. (Canada)
(74) Agent:
(45) Issued:
(22) Filed Date: 1998-02-17
(41) Open to Public Inspection: 1999-08-17
Examination requested: 1998-02-17
(30) Availability of licence: N/A
(30) Language of filing: English

English Abstract




A pulp refining and bleaching process for increasing the pulp brightness of a
mechanical
wood pulp prepared from softwood chips wherein the pulp is treated in one or
more stages in
refiner by adding sodium perborate or peracetic acid generated in a bleach
generating unit by
reacting sodium perborate or hydrogen peroxide with an activating agent such
as
tetraacetylethylenediamine in the presence or absence of caustic solution and
the pulp
discharged from the refiner is subjected to another bleaching stage in a
bleach tower by
separate addition of sodium perborate or hydrogen peroxide with or without a
bleach
activator. The process is preferably carried out by passing the pulp through a
primary refiner
at elevated pressure and optionally to a bleaching tower, a solution of sodium
perborate or
in-situ generated peracetic acid from a mixture of sodium perborate or
hydrogen peroxide and an
activator, tetraacetylethylenediamine being fed in the refiner and sodium
perborate or
hydrogen peroxide with an activator, tetraacetylethylenediamine, being fed in
the bleaching
tower. The pulp after refining has improved brightness and pulp brightness
after an optional
tower bleaching has exceeded 75 ISO% points.


Note: Claims are shown in the official language in which they were submitted.




We claim:
1. A process for simultaneously refining wood pulp in a refiner to produce
pulp with
improved brightness and mechanical properties comprising concurently
introducing
chelating agent. bleach liquor and wood chips or pulp in one or more stages
including a
primary refiner at high temperatures achieved by increasing steam pressures
and where
the bleach liquor comprises a solution of sodium perborate without any alkali
or ex-situ
generated peracetic acid from peroxide or perborate and TAED with NaOH
including
other chemicals such as sodium silicate and magnesium suphate. said solution
having an
alkaline pH of from pH about 10 to about 12 and wherein not more than about
15% by

27




weight of sodium perborate or weight equivalent amount of hydrogen peroxide
and 0.3:1
molar ratio of TAED generated peracetic acid. based on the total weight of the
dry pulp or
wood chips. is added. and the pulp is discharged from the refiner at a pH less
than 7.0 and
whereby the primary refiner bleaching process produces a brightness gain of at
least 16
ISO points in the refiner and improved the mechanical properties of pulp.
wherein the
pulp obtained after refining is optionally subjected to another tower
bleaching
2. A process as claimed in claim 1 where pulp leaving said pressurized refiner
is subjected
to further bleaching in a bleaching tower to produce pulp with ISO brightness
75 points
and above in a single post bleaching stage comprising concurrent treatment of
unbleached
refined pulp or in-refiner bleached pulp with a chealting agent and then with
a bleach
liquor at a temperature not above 50°C and for a time period not
exceeding 90 min. and
where the bleach liquor comprises either a solution of sodium perborate and
TAED with
sodium silicate or a solution of hydrogen peroxide and TAED with NaOH and
sodium
silicate. said solution having an alkaline pH of from 9.6 to 11.2 and wherein
not more
than 12% by weight of sodium perborate and 8% of TAED or 5% of perxide and 10%
of
TAED. based on the total weight of the pulp. is added and the pulp is
discharged from
the tower with a pH not below 7.0 and where tower bleaching of refiner pulp
produced a
pulp with ISO brightness above 75%.
3. A process in claim 1 where no alkali is added with sodium perborate or
peracetic acid
generated from sodium perborate and TAED.
4. A process in claim 2 where no alkali is added with sodium perborate or
sodium perborate
and TAED mixture.
5. A process in claim 1 wherein a perborate concentration more than 5% by
weight of dry
wood chips have been added to the refiner.
6. A process is claim 1 where peracetic acid has been generated ex-situ of the
refiner by
treating separately hydrogen peroxide with TAED or sodium perborate and TAED.
28




7. A process in claim 1 wherein a refiner temperature between 115 to
145°C. has been used
by adjusting the steam pressure.
8. A process in claim 1 wherein the chelating agent is selected from the group
comprising of
ethylenediamine tetraacetic acid (EDTA). dipentamethylenetetramine
pentaacetate
(DTPA) and dipentamethylenetriaminephosphonates (DTPMPA).
9. A process in claim 1, wherein the liquor solution has a pH of about pH 9.8
to 12.
10. A simultaneous wood pulp refining and bleaching process which comprises
the following
steps of: feeding wood chips to a primary presurrized refiner and milling said
wood chips
at elevated temperature using steam pressure to produce a high concentration
pulp;
feeding to said presurrized refiner, during milling, a bleach liquor of sodium
perborate.
Sodium silicate and magnesium sulphate solution having a pH of from about 9.8
to about
12 and discharging the said high concentration pulp from the refiner at a pH
not above
about 7.0 and optionally bleaching the said refined pulp in a bleaching tower
at
atmospheric pressure;
11. A process in claim 2 wherein the bleach liquor is a mixture of hydrogen
peroxide and
tetraacetylethylenediamine (TAED).
12. A process in claim 2 wherein the molar proportion of peroxide to TAED is
from about
0.05 to about 0.5.
13. A process in claim 2. wherein the concentration of hydrogen peroxide is
from about 2.0%
to about 5% by weight of dry pulp.
14. A process in claim 2 wherein the bleach liquor is a mixture of sodium
perborate and
tetraacetylethylenediamine (TAED).
15. A process in claim 2 wherein the molar proportion of peroxide to TAED is
from about
0.05 to about 0.5.

29




16. A process in claim 2. wherein the concentration of sodium perborate is
from about 6.0%
to about 15% by weight of dry pulp.
17. A process in claim 2. wherein no alkali has been added with perborate and
TAED.
18. A process in claim 2. where the pH of the bleach solution is from about
9.8 to about 11.
19. A process in claim 2. wherein the bleaching temperature does not exceed
above 50°C.
20. A process in claim 2. wherein the bleaching time does not exceed above 90
min.
21. A process in claim 2. wherein a chelating stage has been introduced before
bleaching.
22. A process in claim 2. wherein the chelating agent is selected from the
group comprising
of ethylenediamine tetraacetic acid (EDTA). dipentamethylenetetramine
pentaacetate
(DTPA) and dipentamethylenetriaminephosphonates (DTPMPA).
30


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Admin Status

Title Date
(22) Filed 1998-02-17
Examination Requested 1998-02-17
(41) Open to Public Inspection 1999-08-17
Dead Application 2002-12-02

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Request for Examination $200.00 1998-02-17
Filing $150.00 1998-02-17
Maintenance Fee - Application - New Act 2 2000-02-17 $50.00 1999-12-21
Maintenance Fee - Application - New Act 3 2001-02-19 $50.00 2000-12-12
Maintenance Fee - Application - New Act 4 2002-02-18 $50.00 2001-12-12

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Document
Description
Date
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Number of pages Size of Image (KB)
Abstract 1998-02-17 1 43
Claims 1998-02-17 4 111
Description 1998-02-17 27 1,106
Cover Page 1999-08-19 1 39
Fees 2001-12-12 3 121
Correspondence 1998-05-14 1 17
Prosecution-Amendment 2001-08-02 3 97
Correspondence 2003-02-20 1 21
Fees 2003-02-10 3 106
Fees 2000-12-12 1 69
Fees 1999-12-21 1 68