U.S. patent application number 10/228578 was filed with the patent office on 2003-01-02 for cellulose moulded body and process for its production.
Invention is credited to Eichinger, Dieter, Feilmair, Wilhelm, Ruf, Hartmut, Schild, Gabriele.
Application Number | 20030000662 10/228578 |
Document ID | / |
Family ID | 25597664 |
Filed Date | 2003-01-02 |
United States Patent
Application |
20030000662 |
Kind Code |
A1 |
Ruf, Hartmut ; et
al. |
January 2, 2003 |
Cellulose moulded body and process for its production
Abstract
The invention is concerned with a process for the production of
cellulose molded bodies exhibiting high brightness, which is
characterized by a combination of the steps of bleaching pulp using
a bleaching agent, provided that the bleaching agent does not
contain chlorine or any chlorine compound, dissolving the pulp
bleached using the bleaching agent in an aqueous tertiary
amine-oxide, a moldable cellulose solution being obtained, and
processing the moldable cellulose solution into molded bodies.
Inventors: |
Ruf, Hartmut; (Vocklabruck,
AT) ; Eichinger, Dieter; (Vocklabruck, AT) ;
Schild, Gabriele; (Vocklabruck, AT) ; Feilmair,
Wilhelm; (Lenzing, AT) |
Correspondence
Address: |
BAKER & BOTTS
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
|
Family ID: |
25597664 |
Appl. No.: |
10/228578 |
Filed: |
August 27, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10228578 |
Aug 27, 2002 |
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08918889 |
Aug 8, 1997 |
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08918889 |
Aug 8, 1997 |
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PCT/AT96/00257 |
Dec 19, 1996 |
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Current U.S.
Class: |
162/72 |
Current CPC
Class: |
D06L 4/10 20170101; D06L
4/50 20170101; D01F 2/00 20130101 |
Class at
Publication: |
162/72 |
International
Class: |
D21C 003/20 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 1995 |
AT |
A 2099/95 |
Claims
1. A process for the production of cellulose fibres exhibiting high
brightness, characterized by the combination of steps of bleaching
pulp using a bleaching agent, provided that said bleaching agent
does not contain chlorine or any chlorine compound, dissolving said
pulp bleached using said bleaching agent in an aqueous tertiary
amine-oxide, a mouldable cellulose solution being obtained, and
processing said mouldable cellulose solution into fibres.
2. A process according to claim 1, characterized in that said
mouldable cellulose solution is processed into fibres according to
the dry/wet-spinning process.
3. A process according to claim 2, characterized in that said
fibres are bleached using a bleaching agent, provided that said
bleaching agent does not contain chlorine or any chlorine
compound.
4. A process according to one of the claims 1 or 2, characterized
in that as said tertiary amine-oxide N-methylmorpholine-N-oxide is
used.
5. Use of a pulp bleached using a bleaching agent for the
production of cellulose moulded bodies according to the amine-oxide
process, provided that said bleaching agent does not contain
chlorine or any chlorine compound.
Description
[0001] The invention is concerned with a cellulose moulded body,
particularly a cellulose fibre, and a process for its
production.
[0002] For some decades there has been searched for processes for
the production of cellulose fibres able to substitute the viscose
process, today widely employed. As an alternative which is
interesting for its reduced environmental impact among other
reasons, it has been found to dissolve cellulose without
derivatisation in an organic solvent and extrude from this solution
moulded bodies, e.g. fibres, films and other moulded bodies. Fibres
thus extruded have received by BISFA (The International Bureau for
the Standardization of man made fibers) the generic name Lyocell.
By an organic solvent, BISFA understands a mixture of an organic
chemical and water.
[0003] It has turned out that as an organic solvent, a mixture of a
tertiary amine-oxide and water is particularly appropriate for the
production of cellulose moulded bodies. As the amine-oxide,
primarily N-methylmorpholine-N-oxide (NMMO) is used. Other
amine-oxides are described e.g. in EP-A-0 553 070. A process for
the production of mouldable cellulose solutions is known e.g. from
EP-A-0 356 419. The production of cellulose moulded bodies using
tertiary amine-oxides generally is referred to as amine-oxide
process.
[0004] In EP-A-0 356 419, a process for the production of spinnable
cellulose solutions is described, wherein as a starting material,
among other substances, a suspension of cellulose in liquid,
aqueous N-methylmorpholine-N-oxide (NMMO) is used. This process
consists in transforming the suspension in a thin-film treatment
apparatus in one single step and continuously into a mouldable
solution. Finally, the mouldable solution is spun into filaments by
means of a forming tool such as a spinneret, which filaments are
conducted across an air gap, wherein they are stretched, into a
precipitation bath, wherein the cellulose is precipitated.
Afterwards, the cellulose fibres obtained are washed.
[0005] To avoid an undesired discolouration of the fibres,
primarily due to lignin and coloured organic compounds, it is known
to bleach the pulp before processing it. For this purpose, raw pulp
is reacted with a number of bleaching agents such as elemental
chlorine, chlorine compounds such as hypochlorite and chlorine
dioxide, oxygen, peroxide and ozone, under exactly defined
conditions, said reaction being carried out using a combination of
these chemicals in a certain order, which is referred to as
bleaching sequence.
[0006] Classical bleaching processes start using elemental
chlorine, which chlorinates or oxidizes to different extents
depending on the pH value. Hypochlorite and chlorine dioxide
oxidize the lignin and coloured compounds. Between each of the
reaction steps of these bleaching agents, usually an alkaline
extraction is provided to remove the lignin brought into solution
and the other compounds from the reaction medium. For an overview
of the technique of pulp bleaching R. P. Singh; The Bleaching of
Pulp, TAPPI Press, Atlanta, USA, is cited.
[0007] During pulp bleaching, chlorine-containing bleaching agents
produce to different extents chlorinated products which are hardly
degradable and for the most part contaminate waste water.
Therefore, these processes give rise to environmental concerns, and
the use of chlorine-containing bleaching agents, particularly
elemental chlorine, is increasingly restrained. This however
implies also a loss of bleaching quality, since elemental chlorine
has a high bleaching capacity.
[0008] Among the chlorine compounds, chlorine dioxide has a better
bleaching capacity than hypochlorite, but it is more expensive than
hypochlorite, which is more frequently used.
[0009] In the state of the art, bleaching processes which do not
involve any chlorine compounds are also employed. For these
processes, combinations of oxygen/peroxide and ozone respectively
are used. The pulp thus bleached is referred to as TCF (total
chlorine free) pulp, since it is bleached using neither elemental
chlorine nor chlorine compounds. On the other hand, in the
literature a pulp which is not bleached using elemental chlorine
but chlorine compounds is referred to as ECF (elemental chlorine
free) pulp.
[0010] For the purposes of this specification, an ECF pulp bleached
using hypochlorite is referred to as ECF hypochlorite pulp.
[0011] In the state of the art, the so-called brightness is a
measure of the intensity of bleaching. It is known from the viscose
process that there is a relation between the brightness of a
bleached pulp and the brightness of the cellulose products produced
from this pulp in such a way that pulps having a higher brightness
usually may be processed into fibres having also a higher
brightness.
[0012] It is the object of the invention to provide a process
whereby cellulose moulded bodies may be produced which have a
higher brightness than cellulose moulded bodies produced from an
ECF hypochlorite pulp, while the pulps used have the same starting
brightness and which otherwise the same procedure is employed.
[0013] This object is attained by means of a process for the
production of cellulose moulded bodies which is characterized by a
combination of the steps of
[0014] bleaching pulp using a bleaching agent, provided that the
bleaching agent does not contain chlorine or any chlorine
compound,
[0015] dissolving the pulp bleached using the bleaching agent in an
aqueous tertiary amine-oxide, a mouldable cellulose solution being
obtained, and
[0016] processing the mouldable cellulose solution into moulded
bodies.
[0017] By means of the process according to the invention, it is
possible to particularly produce cellulose fibres having a high
brightness, as well as cellulose films according to the
dry/wet-spinning process.
[0018] It is surprising to those skilled in the art that TCF pulps
achieve higher fibre brightnesses than ECF hypochlorite pulps when
the starting pulps have the same brightness, with the positive
side-effect of being able to produce fibres in a particularly
environmentally friendly way.
[0019] The invention is also concerned with the bleaching of fibres
produced according to the amine-oxide process using chlorine-free
bleaching agents such as oxygen, ozone and particularly hydrogen
peroxide.
[0020] A preferred embodiment of the process according to the
invention is characterized in that the fibres or films produced
according to the invention are bleached using a bleaching agent,
provided that the bleaching agent does not contain chlorine or any
chlorine compound.
[0021] As the tertiary amine-oxide, N-methylmorpholine-N-oxide has
shown particularly good results.
[0022] The invention is also concerned with cellulose moulded
bodies, particularly cellulose fibres and films, having a high
brightness, produceable according to the process according to the
invention.
[0023] Moreover, the invention is concerned with the use of a pulp
bleached with a bleaching agent for the production of cellulose
moulded bodies according to the amine-oxide process, provided that
the bleaching agent does not contain chlorine or any chlorine
compound.
[0024] By means of the following Example and Comparative Example,
the invention will be explained in more detail.
EXAMPLE
[0025] To produce a TCF pulp, pulp (of the beech sulphite pulp
type) first was bleached by means of an alkaline oxygen extraction
reinforced by peroxide, afterwards by means of ozone and finally by
means of peroxide, according to known processes. These processes
are described for instance in R. P. Singh; The Bleaching of Pulp,
TAPPI Press, Atlanta, USA, as well as in EP-A-0 426 652.
[0026] The brightness of the TCF pulp obtained, determined
according to ISO 3688, was 90.6. The pulp had a rapid cuprammonium
viscosity according to Zellcheming ZM IV/30/62 of 19.8 Pa.s, as
well as an .alpha. content of 90,9.
[0027] Thereafter, this TCF pulp was processed in a known way in a
stirring vessel into a dope having a composition of 12% of
cellulose, 77% of NMMO and 11% of water. The viscosity of the dope
was 1630 Pa.s (temp.: 90.degree. C., shearing rate: 0.1
s.sup.-1).
[0028] The dope was spun into fibres at 120.degree. C. through a
spinneret having spinning holes exhibiting diameters of 100 .mu.m,
according to the known wet/dry-spinning process (see e.g. EP-A-0
584 318). The brightness of the fibres produced according to the
invention was approximately 50.
[0029] The CIELAB fibre brightness was determined according to the
following method: On the fibres, the colour coordinates R.sub.x,
R.sub.y, R.sub.z were determined according to DIN 6174 and DIN 5033
using the light type D65 and at a 10.degree. observation angle.
From these colour coordinates, according to DIN 55981
(=chromaticity deviation according to Grtner/Griesser), the CIE
brightness and the tint in the red/green-axis may be calculated as
follows:
[0030] CIE brightness: W=Y+800*(x0-x)+1700(y0-y)
[0031] Tint: T=900*(x0-x)-650*(y0-y) (Note: T negative=red cast, T
positive=green cast)
[0032] Y . . . standard chromaticity for green sensitivity (=
[0033] Ry . . . reflectance value green)
[0034] x0, y0 . . . standard chromaticity coordinates of the
achromatic point (at D65/10.degree. is: x0=0.3138; y0=0.3310)
[0035] x, y . . . standard chromaticity coordinates of the samples;
to be calculated according to:
x=X/(X+Y+Z)
y=Y/(X+Y+Z)
z=1-x-y
[0036] The standard chromaticity numbers X, Y, Z appearing in these
formulae may be calculated from the reflectance values (=filter
values) Rx, Ry, Rz at the light type D65 and a 10.degree.
observation angle according to the formulae:
X=0.94811*Rx
Y=Ry
Z=1.07304*Rz
[0037] Subsequently, these fibres were bleached using hydrogen
peroxide (1,5 g of H.sub.2O.sub.2; stabilizing agent: 0,2 g/l of
MgSO.sub.4; pH 10,5; fleet ratio 1:20; 70.degree. C.; bleaching
duration: 3 minutes). The CIELAB brightness of the bleached fibres
was 57.
Comparative Example
[0038] To produce an ECF hypochlorite pulp, first the same starting
pulp as in the above Example was bleached by means of an alkaline
oxygen extraction reinforced by peroxide, afterwards by means of
hypochlorite and finally by means of peroxide.
[0039] The brightness of the ECF hypochlorite pulp obtained was
91.6 and thus virtually the same as the one of the TCF pulp
produced in the Example.
[0040] Afterwards, a dope and fibres were produced analogously to
the above Example. The fibres produced had a CIELAB brightness of
about 39. Thus it becomes clear that the TCF pulp bleached
according to the invention without any chlorine compound may be
processed into fibres having a higher brightness than the ECF pulp
bleached by means of, among other substances, hypochlorite.
[0041] Subsequently, the fibres produced were bleached as described
in the above Example. The bleached fibres had a CIELAB brightness
of about 54.
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