METHODE DE PREPARATION DE FIBRES DE CELLULOSE A PARTIR DU BOIS DE PIN

PROCESS FOR THE PREPARATION OF CELLULOSE FIBRES FROM PINE

Abrégé anglais

ABSTRACT OF THE DISCLOSURE
The present invention provides a process for the prep-
aration of cellulose fibres from pine, which are of the medium-
viscosity to high-viscosity type, wherein the cellulose fibres
obtained from pulping pine in sulphite cookers are treated, when
required with a quantity of chlorine, which corresponds to between
0.01 and 20% by weight of the quantity of chlorine used in clas-
sical bleaching procedures applied to sulphite process cellulose
fibres from pine, and/or wherein said cellulose fibres from pine,
which have not been delignified further or only to a very limited
extent in this treatment with chlorine, are pretreated, when
required in an acidic medium, whereupon said cellulose fibres
from pine are refined with alkali at an elevated temperature, and
thereafter delignified in an alkaline, aqueous medium with per-
oxide compounds, and then bleached by applying conventional
single-stage or multi-stage bleaching procedures.

Revendications

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for the preparation of cellulose fibres
from pine, which are of the medium-viscosity to high-viscosity
type, wherein the cellulose fibres obtained from pulping pine in
sulphite cookers are refined with alkali at an elevated temper-
ature, and, thereafter delignified in an alkaline, aqueous
medium with peroxide compounds, and then bleached by applying
conventional single-stage or multi-stage bleaching procedures.
2. A process as claimed in claim 1, in which the cellu-
lose fibres before alkali refining are treated with a quantity of
chlorine, which corresponds to between 0.01 and 20% by weight of
the quantity of chlorine used in classical bleaching procedures
applied to sulphite process cellulose fibres from pine.
3. A process as claimed in claim 1, in which the
cellulose fibres are pretreated in an acid medium prior to refining
with alkali.
4. A process in accordance with claim 1, in which at
least one magnesium salt is present as an additive in the alkaline,
aqueous medium in which said cellulose fibres from pine are de-
lignified with peroxide compounds.
5. A process as claimed in claim 4, in which the mag-
nesium salt is selected from magnesium chloride, bromide, iodide,
silicate, sulphate, acetate or oxide.
6. A process as claimed in claim 2, in which the cellu-
lose fibres are treated with chlorine in an amount of 0.4 to 1.2%
by weight calculated on fibre weight, the treatment being for a
period up to 0.8 hours.

7. A process as claimed in claim 6, in which the treat-
ment period is 0.01 to 0.75 hours and the pH of the treatment is
maintained between 1 and 2.
8. A process as claimed in claim 1 in which the fibres
are treated before alkali refining with an acidic medium at a pH
between 2 and 5, at a temperature from 0 to 50°C at a fibre con-
centration of between 2 and 5% by weight and for a time of at
least 1 minute.
9. A process as claimed in claim 8, in which the time
is 6 to 60 minutes.
10. A process as claimed in claim 8 or 9, in which the
refining with alkali is effected at a temperature for 60°C to
the boiling point of the fibre suspension for at least 0.1 hours,
at a fibre concentration between 10 and 20% by weight and an
alkali concentration of from 2 to 12% by weight based on the
weight of dry fibre material.
11. A process as claimed in claim 1, 2 or 3, in which
the peroxide is selected from hydrogen peroxide, sodium peroxide,
and tert.-butyl peroxide.
12. A process as claimed in claim 1, 2 or 3, in which
the peroxide delignification is effected at a peroxide concentra-
tion of 0.2 to 10% by weight based on the weight of dry fibre and
a fibre concentration of at least 4% by weight and at a temper-
ature between 35°C and the boiling point of the aqueous medium.
13. A process as claimed in claim 1, 2 or 3 in which
the peroxide delignification is effected at a peroxide concentra-
tion of 0.6 to 6% by weight based on the weight of dry fibre and
a fibre concentration of at least 6 and 16% by weight and at a
temperature between 35°C and the boiling point of the aqueous
medium.
14. A process as claimed in claim 1, 2 or 3, in which
the peroxide delignification is effected in the presence of an
11

alkali selected from alkali metal and alkaline earth metal hydrox-
ide, and ammonium hydroxide in an amount from 0.5 to 4% by weight
calculated on the weight of dry fibre material.
15. A process as claimed in claim 1, 2 or 3, in which
the peroxide delignification is effected in the presence of an
alkali selected from alkali metal and alkaline earth metal hydrox-
ide, and ammonium hydroxide in and amount from 1 and 3% by weight
calculated on the weight of the fibre material.
12

Description

:~3;~66~
The present invention relates to a process for the prep-
aration of cellulose fibres from pine which fibres are of the
medlum-viscosity to high-viscosity type.
Cellulose fibres from pine of the medium-viscosity to
hicJh-viscosity type, which have been refined by treating them
with alkali, are used as starting material in the manufacture of
specialty papers, for instance photographic papers. Another field
of application for refined sulphite process cellulose fibres from
pine istheir useas a starting material in the preparation of
cellulose esters and cellulose ethers, their use in the manufac-
ture of plastics, and their use in the manufacture of hygienic
products, for instance diapers for babies.
It has been found that the sulphite process cellulose
fibres from pine which are best suited for these fields of appli-
cation are characterized by a high content of ~-cellulose, of at
least 91% ~-cellulose (of the dry fibre material), a DP-value of
at least 1000, a good reactivity, a maximum of extractable matter
content of 0.2~ by weight (dichloromethane method), and a maximum
of ash content of 0.15~ by weight (of the dry fibre material).
It is known that this type of sulphite process cellu-
lose fibres from pine can be prepared by cooking said fibres
first and delignifying them completely, thereafter, with elemental
chlorine (see page 1066 in the book: "Pulping Processes", by
S.A. Rydholm, New York, Interscience Publishers', 1965). This
process, however, brings with it the disadvantage that in the
delignification step, which consumes chlorine, waste waters are
obtained which carry a high concentration of chlorinated lignin
compounds, which are difficult to remove from the water, if ever,
and only by applying expensive waste water treatment procedures,
The presentinvention providesa delignificationprocess
applicable to sulphite process cellulose fibres ofthe typespecified
above from which waste waters would result which would be much

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easler to purify.
~ ccording to the present invention there is provided a
process for the preparation of cellulose fibres from pine, which
are of the medium-viscosity to high viscosity type, wherein the
cellulose fibres obtained from pulping pine in sulphite cookers
are treated, when required with a quantity of chlorine, which
corresponds to between 0.01 and 20% by weight of the quantity of
chlorine used in classical bleaching procedures applied to sul-
phite process cellulose fibres from pine, and/or wherein said
cellulose fibres from pine, which have not been delignified
further or only to a very limited extent in this treatment with
chlorine, are pretreated, when required, in an acidic medium,
whereupon said cellulose fibres from pine are refined with alkali
at an elevated temperature, and thereafter delignified in an
alkaline, aqueous medium with peroxide compounds, and then
bleached by applying conventional single-stage or multi-stage
bleaching procedures.
Thus, in accordance with the present invention in the
process for the preparation of sulphite process cellulose fibres
from pine, which are of the medium-viscosity to high-viscosity
type, the cellulose fibres, obtained from sulphite pulping pro-
cesses applied to pine, are treated, when required, with a quan-
tity of chlorine which corresponds to between 0.01 and 20% by
weight of the quantity of chlorine required in the classical
bleaching processes applied to cellulose fibres from pine, said
cellulose fibres from pine bei.ng subject, when required to pre-
treatment in an acidic medium, whereupon said cellulose fibres
from pine which have not been delignified or only insignificantly
delignified, undergo conventional alkaline finishing processes
which are effected at elevated temperatures, whereafter said
cellulose fibres from pine are delignified by reacting them with
peroxide in an alkaline aqueous medium, said delignified cellulose

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fibres ~rom pine being subject, thereafter to conventional single-
stage or multi-stage afterbleaching processes.
In a preferred embodiment of the present invention
magnesium salts are added to the alkaline aqueous medium, in which
said fiulphite process cellulose fibres from pine are delignified
by treating them with peroxide. Quantities of between 0.01 and
1~ by weight of magnesium salts (calculated on the weight of the
fibre material) may be used. Magnesium salts which can be used
in this manner are, for instance, magnesium chloride, magnesium
bromide, magnesium iodide, magnesium carbonate, magnesium silicate
magnesium sulphate, magnesium acetate or magnesium oxide.
In accordance with the present invention the quantity
of chlorine used in the step of the series of treatment processes
corresponds to between 0.01 and 20% by weight of the ~uantity of
chlorine which was hitherto applied in the conventional chlorine
treatment stages for sulphite process cellulosic fibres from pine.
In the conventional processes use is made of between 4 and 6% by
weight of chlorine (calculated on fibre weight) (see page 1066
in the book: "Pulping Processes", by S.A. Rydholm, New York,
Interscience Publishers, 1965). Whereas the conventional proc-
esses require that the reaction time for the chlorine with said~
cellulose fibres is up to one hour. In the process of this inven-
tion, however, the time for reacting chlorine with said celluose
fibres can be shortened to a maximum of 0.8 hours, preferentially
to between 0.01 and 0.75 hours.
In a preferred embodiment of the process of the present
invention the reaction of chlorine with said cellulose fibres can
be performed at a pH between 1 and 2. This pH value can be
achieved by adding inorganic acids, such as hydrochloric acid or
sulphuric acid.
The acidic pretreatment procedure can be performed by
using inorganic acids such as sulphuric acid, hydrochloric acid,

~336~
sulpllurous acid and/or organic aclds such as formic acid, acetic
acid, at a pll between 2 and 5, at a temperature of between 0 and
50C, at a fibre concentration of between 2 and 5% by weight and
in a time period of at least 1 minute, preferentially a time
period of between 6 and 60 minutes.
The refining with alkali of said cellulose fibres from
pine, which have not been delignified at all further, or only to
an insignificantly small degree beyond the delignification
achieved in the sulphite cooking process, can be performed at
temperatures of between 60C and the boiling temperature of the
fibre suspension. The time required for said refining procedure
with the alkali is at least 0.1 hour, preferentially between 0.5
and 4 hours. A fibre concentration at least of 6% by weight,
preferentially of between 10 and 20% by weight and an alkali
concentration of between 2 and 12~ by weight (calculated on
weight of dry fibre material) may be maintained.
Inorganic peroxides, for instance hydrogen peroxide,
sodium peroxide or an organic peroxide, for instance tertiary-
butylhydroperoxide can be used in the peroxide delignification
procedure. Any one of said peroxide compounds may be used.
Combinations of said peroxide compounds will also serve the
purpose. Said peroxide compounds can be used in quantities of
between 0.2 and 10% by weight, preferentially of between 0!6 and
6% by weight (calculated on weight of dry fibre material).
Furthermore, a fibre concentration of at least 4% by
weight, preferentially of between 6 and 16% by weight can be
maintained in the peroxide delignification procedure.
Alkali metal hydroxides, for instance, sodium hydroxide
or potassium hydroxide, aqueous ammonia solution, and/or
alkaline earth metal hydroxides such as magnesium hydroxide,
calcium hydroxide may be used for preparing the alkaline, aqueous
medium for the peroxide delignification procedure, saidhydroxides
-- 4 --

1~3~6~
being used in quantities of between 0.5 and 4~ by weight, prefer-
entially of between 1 and 3% by weight (calculated on weight of
dry fibre material) during the peroxide delignification period
tlle temperature of the fibre suspension may be kept between 35C
and the boiling temperature of the medium.
In addition one may apply stabilizing agents such as
ethylenediaminotetraacetic acid, diethylenetriaminopentaacetic
acid, nitrilotriacetic acid and/or polycarbonic acids ln accor-
dance with the teachings of DT-OS 19 04 940, DT-OS 19 04 941,
and/or DT-OS 19 42 556.
The essential advantages of the process of the present
invention are, that waste waters are obtained which are rather
low in content of inorganic chloride ions as well as rather low
in contaminating organic chlorine compounds. These waste waters
are amendable to waste water regeneration procedures, whereafter
they may be fed back and reused in the delignification of said
sulphite process cellulose fibres.
Another advantage of the process of the present inven-
tion is that there is no necessity to add waterglass as a stab-
ilizing agent to said cellulose fibres prior or during the pero-
xide delignification step to avold thereby the formation of
inorganic deposits on said fibre mat~-rial.
The present invention will be further illustrated by
wa~ of the following examples:
Example 1:
Preparation of cellulose fibres of the high viscosity type
Cellulose fibres from pine prepared in a calcium bisulphite pro-
cess cooked (kappa value = 17) are treated in a five-step proce-
dure in the sequence given hereafter.
1.1 Light treatment with chlorine:
(Partial treatment with chlorine)
Chlorine 1% (of fibre weight)

~3~i63
Temperature 35C
Fibre concentration 4%
Duration 45 minutes
pll reading approx. 2
1.2 Refining with al]tali:
Sodium hydroxide 8% (of fibre weight)
Temperature 85C
Fibre concentration 16~
Duration 2 hours
1.3 Delignifying with peroxide:
~ydrogen peroxide 1.5% (of fibre weight)
(applied as aqueous
solution)
Sodium hydroxide 2% (of fibre weight)
~agnesium chloride 0.3~ (of fibre weight)
Temperature 40C
Fibre concentration 12~
Duration 4 hours
The cellulose fibres from pine treated in this manner show the
following characteristics:
~-cellulose 93%
Cuoxam viscosity 2600 mp
Whiteness 70% MgO (Elrepho)
Extractables 0.06~ (Dichlormethane~
Thereafter, the cellulose fibres which passed the delignifying
and prebleaching procedures are subject to further treatments,
in which conventional bleaching procedures are used.
1.4 Chlorine dioxide bleach:
Applied in accordance with the procedure described on page 780,
in volume 18, 1967, of "Ullmanns Enzyklopaedie der technischen
Chemie", third edition.
1.5 Hypochlorite bleach:
Applied in accordance with the procedure described on page 779,
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~33~
in volume 18, 1967, of "Ullmanns Enzyklopaedie der echnischen
Chemie", third e~ition.
The cellulose ~ibres which passed the fi~th processing step have
the following characteristics:
~-cellulose 92%
Wood rubber 2.9P~
DP value 1500
R 18 93.6%
Ash content 0.11%
Extractable matter 0.04% (dichloro-methane)
Copper value 0.8
Whiteness 91~ MgO
Cuoxam viscosity 2300 mp
The data were obtained by applying the following well known
methods for testing.
~-cellulose Merkblatt Zellcheming IV/39/67
Or page 598 in the book: "Chemisch-
technische untersuchungsmethoden
der Zellstoff- und Papierindustrie"
by Siber,
Berlin, Springer Verlag, 1957.
Wood rubber Merkblatt Zellcheming IV/9/67
DP value Merkblatt Zellcheming DIII/1/72
R 18 Merkblatt Zellcheming IV/39/67
Ash content: Merkblatt Zellcheming IV/40/67
Extractable matter: llerkblatt Zellcheming IV/43/67
Copper value: Merkblatt Zellcheming IV/8/70
Whiteness Merkblatt Zellcheming V/10/63
Cuoxam viscosity Merkblatt Zellcheming IV/30/62
The percentage values given in this example are by weight (based
on the weight of the dry fiber material) if not stated otherwise.
Example 2:
Preparation of cellulose fibres of the medium viscosity type
Cellulose fibres from pine prepared in a calcium bisulphite pro-

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cess cooker (kappa value = 15) are treated in a five-step proce-
dure in the sequence given hereafter:
2.1 Light treatment with chlorine:
(Partial treatment with chlorine)
Chlorine gas 0.8%
(used as aqueous
solution)
Temperature 45C
Fibre concentration 4%
Duration 45 minutes
pH-reading approx. 2
2.2 Refining with alkali:
Sodium hydroxide 6%
(used as aqueous
solution)
Temperature 85C
Fibre concentration 16%
Duration 2 hours
2.3 Delignifying with peroxide:
Hydrogen peroxide 1.5%
(used as aqueous
solution)
Sodium hydroxide 1.5%
Magnesium chloride 0.3%
Temperature 40C
Fibre concentration 12%
Duration 4 hours
The cellulose fibres from pine treated in this manner have the
following characteristics:
~-cellulose 92.5%
Cuoxam viscosity 1900 mp
Whiteness 70% MgO (Elrepho)
Extractables 0.05% (dichloromethane)
Thereafter, the cellulose fibres which passed the delignifying
and prebleaching procedure are subject to further treatments, in

~L3~fi~1
which conven-tion bleaching procedures are used.
2 4 Chlorine dioxide bleach:
Applied in accordance with the procedure described on page 780,
in volume 18, 1967 of "Ullmanns Enzyklopaedie der technischen
Chemie", third edition.
_.5 ~ypochlorite bleach:
Applied in accordance with the procedure described on page 779,
in volume 18, 1967, of "Ullmanns Enzyklopaedie der technischen
Chemie", third edition.
The cellulose fibres which passed the fifth processing step have
the following characteristics.
~-cellulose 93%
DP value 1200
Ash content 0.08%
Extractables 0.1 to 0.2% (dichloromethane)
Whiteness 94% MgO
Cuoxam viscosity 600 mp
The data are determined by applying the methods of testing
mentioned in Example 1.
The percentage values in this example are by weight (based on the
weight of the dry fiber material), if not stated otherwise.
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