CA2230050A1 - Process for preparation of an aqueous solution of n-methylmorpholin-n-oxide - Google Patents
Process for preparation of an aqueous solution of n-methylmorpholin-n-oxide Download PDFInfo
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- CA2230050A1 CA2230050A1 CA002230050A CA2230050A CA2230050A1 CA 2230050 A1 CA2230050 A1 CA 2230050A1 CA 002230050 A CA002230050 A CA 002230050A CA 2230050 A CA2230050 A CA 2230050A CA 2230050 A1 CA2230050 A1 CA 2230050A1
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- methylmorpholine
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F13/00—Recovery of starting material, waste material or solvents during the manufacture of artificial filaments or the like
- D01F13/02—Recovery of starting material, waste material or solvents during the manufacture of artificial filaments or the like of cellulose, cellulose derivatives or proteins
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B1/00—Preparatory treatment of cellulose for making derivatives thereof, e.g. pre-treatment, pre-soaking, activation
- C08B1/003—Preparation of cellulose solutions, i.e. dopes, with different possible solvents, e.g. ionic liquids
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F2/00—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
- Y02P70/62—Manufacturing or production processes characterised by the final manufactured product related technologies for production or treatment of textile or flexible materials or products thereof, including footwear
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- Engineering & Computer Science (AREA)
- Textile Engineering (AREA)
- General Chemical & Material Sciences (AREA)
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- Health & Medical Sciences (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
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- Life Sciences & Earth Sciences (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention relates to a process for the preparation of a solution of Nmethylmorpholin-N-oxide in water, which solution is used in the amine oxide process. The preparation process is characterised by the following steps: (a) an aqueous solution (A) is provided which contains N-methylmorpholine and is derived from the amine oxide process; (b) subsequently another aqueous solution (B) is added to said solution (A), and contains N-methylmorpholine, and a solution (C) is produced which (c) is treated with an oxidant to oxidise N-methylmorpholine to form N-methylmorpholin-N-oxide, a solution (D) of Nmethylmorpholin-N-oxide being formed in water.
Description
~ CA 022300~0 1998-02-19 ~ ~ ~
~.
PROCESS FOR THE PRODUCTION OF AN AQUEOUS SOLUTION OF N-M~'l'~YLMORPHOLINE-N-OXIDE
The present invention is concerned with a process for the production of a solution of N-methylmorpholine-N-oxide in water used in the amine-oxide process. The invention is further concerned with a process for the production of cellulose moulded bodies, particularly fibres and films.
For some decades there has been searched for processes for the production of cellulose moulded bodies 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 such as 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.
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 - o 356 419. For the purposes of the present specification and the present claims, the production of mouldable solutions of cellulose in tertiary amine-oxides and their further processing into moulded bodies is generally referred to as amine-oxide process.
In EP-A - 0 356 419, an amine-oxide process for the production of spinnable cellulose solutions is described, wherein as a starting material among others 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 _ CA 022300~0 1998-02-19 .
, ~ --2--step and continuously into a mouldable solution. Finally, the mouldable solution is spun into filaments by a forming tool such as a spinneret and the filaments are passed through a precipitation bath.
In the precipitation bath the cellulose is precipitated. The tertiary amine-oxide is accumulated in the precipitation bath. The precipitation bath may contain up to 30% by weight of amine-oxidè. For the economy of the amine-oxide process it is of vital importance to recover the amine-oxide as completely as possible and reuse it for the production of a mouldable cellulose solution. Thus it is necessary to recover NMMO from the precipitation bath.
In addition to the amine-oxide however, degradation products of the amine-oxide process are also accumulated in the precipitation bath. These degradation products may be intensively coloured, thus deteriorating the quality of the cellulose moulded bodies produced. On the other hand, other substances may represent an additional safety risk, since under certain conditions the amine-oxide tends to show highly exothermic decomposition reactions and these decomposition reactions may be induced or accelerated by certain substances. These substances have to be removed from the precipitation bath which is to be regenerated before the NMMO
is concentrated and separated.
After removing these unwanted substances, water is withdrawn from the purified precipitation bath which is optionally combined with other process liquids of the amine-oxide process such as vapour condensates formed during the production of the cellulose solution. This may be carried out for instance by means of evaporation. In the residue of this evaporation, highly concentrated aqueous amine-oxide is obtained which is recycled again into the amine-oxide process. The evaporation vapours consist primarily of water, wherein however significant amounts of N-methylmorpholine, the main decomposition product of NMMO, are also dissolved.
CA 022300~0 1998-02-19 Typically, the vapours contain e.g. up to 1000 mg of NMMO and 240 mg of N-methylmorpholine per litre. These vapours are conveniently concentrated, for instance by means of reverse osmosis.
To close the cycles as far as possible and also to keep the NMMO losses as low as possible, efforts are made to oxidize the N-methylmorpholine again to NMMO. This can be achieved for instance using a peroxide oxidant.
A process for the preparative production of tertiary amine-oxides by means of oxidation of tertiary amines is known ~or instance from EP-A - 0 092 862. According to this process, the amine-oxide is oxidized under pressure with molecular oxygen in an aqueous solvent, which solvent has a pH value approximately equal to or higher than the pKa value of the tertiary amine.
DD-A - 259 863 is concerned with the production of aqueous NMMO solutions by means of oxidation of N-methylmorpholine with H2O2 and passing the reaction solution through one or more exchanger columns filled with a styrene/divinylbenzene-copolymer cont~ining sulphonate groups, and by means of adjusting the pH value of the solution to values ranging from 8 to 5 by addition of phosphoric acid.
Oxidation of N-methylmorpholine with H2~2 to NMMO is known e.g. from EP-A - 0 254 803. From DE-A - 4 140 259 the production of NMMO is known, in which process the formation o~ nitrosamines is inhibited by scavenging primary and secondary amines e.g. with acid halides. EP-A - o 320 690 describes the production of amine-oxides substantially free of nitrosamines through oxidation with peroxides in the presence of a combination of CO2/ascorbic acid acting as a nitrosamine inhibitor. From EP-A - o 401 503, oxidation with H2~2 in water and a co-solvent, preferably a carboxylic acid ester, is known. According to FR-A - 8 808 039, oxidation is carried out while CO2 is added, and according to US-A -CA 022300~0 1998-02-19 ~, 5,216,154 oxidation to NMMO is carried out in a pure CO2 atmosphere.
Inspite of operating in largely closed cycles, the amine-oxide process involves solvent losses which are due to dilution steps during fibre purification, the deliverance of the fibre itself, and particularly to the chemical decomposition of NMMO under thermal stress during the process described in the literature (Lang H. et al., Cell. Chem.
Technol. 20, 1986, No. 3, page 289; and Taeger E. et al., Formeln, Faserstoffe, Fertigware 4, 1985, pages 14-22).
Inspite of numerous optimization efforts to mi nimi ze the decomposition behaviour (e.g. using chemical stabilizers), a complete prevention of such reactions has not been achieved so far. For these reasons, in the state of the art a regular feeding of NMM0 is necessary. According to EP-A - O 448 924 of the applicant, part of the NMMO decomposition products, particularly N-methylmorpholine (NMM), present in highly diluted solutions may be concentrated and afterwards reoxidized to NMMO in a known manner, which NMMO is introduced again into the amine-oxide process.
Although reoxidation of the decomposition product NMM
contained in the vapours to NMMO reduces the losses of expensive NMMO, it does not obviate the necessity of feeding to the amine-oxide process additionally up to several percent of NMMO per kilogramm of processed pulp. A drawback of this procedure consists in the high cost of technical ~MMO which has to be fed continuously to the amine-oxide process.
Thus it is the object of the present invention to overcome this drawback providing a process wherein the addition of fresh NMMO may be largely reduced or even avoided.
This objective is attained by a process for the production of a solution of N-methylmorpholine-N-oxide in water used in the amine-oxide process, characterized by the following steps that CA 022300~0 1998-02-19 (a) an aqueous solution (A) deriving from the amine-oxide process and cont~i n i ng N-methylmorpholine is provided;
whereafter (b) said solution (A) is mixed with a further aqueous solution tB) cont~i n i ng N-methylmorpholine, thus yielding a solution (C) which (c) is treated with an oxidant to oxidize N-methylmorpholine to N-methylmorpholine-N-oxide, whereby a solution (D) of N-methylmorpholine-N-oxide in water is produced which is used in the amine-oxide process.
It has proven convenient to add to solution (A) at least the same amount of N-methylmorpholine by means of solution (B) as contained in solution (A).
As an oxidant, a peroxide is best used.
It is known that the aqueous solution (A) derived from the amine-oxide process contains morpholine additionally to N-methylmorpholine. In the context of oxidation, this morpholine represents a preliminary stage of the toxic N-nitrosomorpholine. The inventors of the present invention have found that the formation of toxic N-nitrosomorpholine may be restrained when the solution (C) to be treated with the oxidant has a pH value of from 6.0 to 9Ø It has been shown that by simply adjusting the pH of the oxidation mixture within the indicated range it is possible to restrain the formation of toxic N-nitrosomorpholine while simultaneously achieving a m~; mllm oxidation of N-methylmorpholine to NMMO. The dependance of these two reaction ways on the pH can be observed in the attached drawings and is described in the Austrian patent application A 1398/95 of the applicant.
It has proven highly advantageous to adjust the pH value of the aqueous solution within the desired range by passing the solution to be processed through a cation exchanger capable of absorbing morpholine. This step has two important effects CA 022300~0 1998-02-19 .
on the reduction of nitrosamines. By means of the cation exchanger, morpholine is selectively removed from the solution, so that virtually no morpholine is available for the new formation of nitrosamines. Additionally, by separating the morpholine, which compared to other components has the highest basicity, the pH value of the solution is lowered precisely into the range wherein the production of NMMO reaches high values but the formation of nitrosamines is further impeded.
To separate morpholine, the cation exchanger best comprises carboxyl groups or sulphonic acid groups.
The small amounts of N-nitrosomorpholine formed inspite of the above-mentioned adjustment of the pH value may be largely destroyed by exposing the aqueous solution (C) during or after treatment with the peroxide oxidant to ultraviolet light substantially having a wavelength of 254 nm. The presence of the peroxide oxidant does not impede this destruction. The destruction of N-nitrosomorpholine using ultraviolet light is described in the Austrian patent application A 1401/95.
Working procedures for the quantitative analysis of nitrosamines using an exposure to ultraviolet light and a subsequent determination of the nitrites formed are known (D.E.G. Shuker, S.R. Tannenbaum, Anal. Chem., 1983, 55, 2152-2155; M. Rhighezza, M.H. Murello, A.M. Siouffi, J. Chromat., 1987, 410, 145-155; J.J. Conboy, J.H. Hotchkiss, Analyst, 1989, 114, 155-159; B. B~chele, L. Hoffmann, J. Lang, Fresen.J.Anal.Chem., 1990, 336, 328-333). However, these analytical working procedures do not deal with the destruction of N-nitrosomorpholine.
In the process according to the invention, H2~2 is preferably used as the peroxide oxidant. The H2~2 is preferably used in the form of an aqueous solution having 20-50~ by weight of CA 022300~0 1998-02-19 H2O2. The H2O2 is best used in an amount of from 0.8 to 2 mol per mol of N-methylmorpholine.
The ultraviolet light whereto the a~ueous solution is exposed is best emitted from a mercury low-pressure lamp. These low-pressure lamps have an intensity m~; mllm at 254 nm.
For an exposure to the light of a low-pressure lamp according to the invention, the lamp may be introduced into the vessel cont~i n i ng the process liquid to be treated. However, the lamp may also be arranged in a different manner. Moreover, exposure to the light may be carried out ~or instance also during a continuous circulation of the solution to be irradiated, i.e. exposed to ultraviolet light, within a thin-film ultraviolet light reactor.
The radiation intensity may range e.g. from 200 to 500 mJ/cm2, depending on the design of the lamp and the process conditions, particularly the temperature. AlSo this embodiment of the process according to the invention does not involve any additional chemicals.
To remove non-reacted N-methylmorpholine still present in solution (D), it has proven convenient to subject solution (D) to a distillation. During distillation, vapours are formed which after condensation yield solution (E), which may be used at least partly as solution (B).
The invention is further concerned with a process for the production of cellulose moulded bodies according to the amine-oxide process, wherein cellulose is dissolved in an aqueous NMMO solution to produce a mouldable solution, the solution obtained is moulded and after moulding passed into a precipitation bath, thus cellulose moulded bodies and a spent precipitation bath being produced, which precipitation bath is regenerated to recover NMMO, whereby an aqueous solution conta; ni ng N-methylmorpholine is obtained which, optionally together with the vapour condensates formed in the amine-CA 022300~0 1998-02-19 .
oxide process, is subjected to oxidation to produce a fresh aqueous NMMO solution which is used again for the production of a mouldable cellulose solution. This process is characterized in that fresh N-methylmorpholine is added to the solution cont~;n;ng N-methylmorpholine obtained when regenerating the spent precipitation bath, whereafter the solution is subjected to oxidation.
Thus, in the process according to the invention it is not NMMO but N-methylmorpholine which is fed to the amine-oxide process and oxidized to NMMo together with the N-methylmorpholine which is formed in the amine-oxide process due to the decomposition of NMMO and is contained in the different process liquids such as the vapour condensates which are formed when preparing the mouldable cellulose solution or evaporating the precipitation bath. Those skilled in the art are free to choose the moment when N-methylmorpholine is added to the process liquids deriving from the amine-oxide process without impairing the result of the process according to the invention.
By means of the following Examples, the invention will be explained in more detail. The abbreviations NMOR, NMMO, NMM
and M used in the following refer to N-nitrosomorpholine, N-methylmorpholine-N-oxide, N-methylmorpholine and morpholine respectively.
Example 1 A mixture of vapour condensates containing NMMO and NMM
formed when preparing the mouldable cellulose solution from the cellulose suspension and evaporating the precipitation bath to be regenerated is filtered and concentrated in a reverse osmosis arrangement. The retained residue thus obtained contains for instance about 7 kg of NMM and about 15 kg of NMMO per 1000 kg.
CA 022300~0 1998-02-19 , _g_ This solution is mixed with 44.3 kg of NMM per looo kg and introduced into a-reactor for oxidation. At 65 C, 79.5 kg of 22% H2~2 are added over a period of 10 minutes while the solution is stirred. After a reaction time of 7 hours at 70~C, not reacted NMM is evaporated from the solution at a reduced pressure of 100 mbar.
In the distillation residue rem~in~ an aqueous solution containing 51.8 kg of dissolved NMMO which is fed again into the amine-oxide process, i.e. may be used to produce the cellulose suspension.
The condensate produced by evaporation contains not reacted NMM (19.5 kg) and is mixed with 24.8 kg of NMM and fed to the following batch of residue.
Example 2 A mixture of vapour condensates cont~;ning NMMO and NMM
formed when preparing the mouldable cellulose solution from the cellulose suspension and evaporating the precipitation bath to be regenerated is ~iltered and concentrated in a reverse osmosis arrangement. The retained residue thus obtained contains for instance about 7 kg of NMM and about 15 kg of NMMO per loOo kg.
This solution is mixed with 44.3 kg of NMM per looo kg and thereafter purified by means of a cation exchanger. The purified solution is introduced into a reactor for oxidation.
At 65~C, 79.5 kg of 22% H2~2 is added over a period of 10 minutes while the solution is stirred. After a reaction time of 7 hours at 70~C, the solution is passed onto a further vessel and exposed to ultraviolet light having a wave length of 254 nm for 10 hours. Afterwards, not reacted NMM is evaporated from the solution at a reduced pressure of about 100 mbar and a temperature of 70~C.
" CA 022300~0 1998-02-19 .
In the distillation residue r~m~ins an aqueous solution cont~; n i ng 51.8 kg of NMMO. This solution is fed to the amine-oxide process, i.e. is used to produce the cellulose suspension.
The condensate produced by evaporation contains not reacted NMM (19.5 kg) and is mixed with 24.8 kg of NMM and fed to the following batch of retained residue.
Example 3 An aqueous solution containing 42 ~g of NMOR, 459 mg of NMMO, 4300 mg of NMM and 200 mg of M per litre was irradiated in an ultraviolet light reactor by means of a mercury low-pressure lamp (ultraviolet light lamp of the Katadyn EK-36 type, no.
79000; made by Ratadyn) (wavelength: 254 nm). The temperature of the aqueous solution was 60 C. The concentration of NMOR
was determined by means of HPLC (column: Hypersil ODS 250 x 4 mm; 50 C; eluant: A = 0.6% of acetonitrile; B = 49.7% of H2O;
gradient 1 ml/min; 10 min. - 100% of A; 7 min. - 100% of B;
detector: W 238 nm).
After an irradiation time of 150 minutes, the NMOR content in the process liquid declined to 40 ~g/l. After 150 minutes more, there was no more evidence of NMOR.
After there was no more evidence of NMOR, the irradiation was stopped, and it was re-~;ned for NMOR in time intervals of several hours. No more NMOR could be detected, thus being proven that NMOR will not be formed again.
Example 4 An aqueous solution cont~; n; ng 25 ~g of NMOR, 2530 mg of NMMO, 3923 mg of NMM and 30 mg of M per litre was mixed with 30% H2~2 for oxidation of NMM to NMMO (mol of NMM/mol ~f H2O2 = 1/1.2) and exposed to ultraviolet light as described in Example 3. Within the first 90 minutes, the NMOR
CA 022300~0 1998-02-19 concentration increased to 45 ~g/l, which is due to a fast reaction of the M present in the solution. Thereafter, the NMOR concentration decreased again significantly. After 6 hours, there was no more evidence of NMOR.
After a total oxidation time of 20 hours, the solution contained 5386 mg of NMMO/litre. This is equivalent to à
yield of 62% of theory.
Example 5 7 aqueous solutions (50 ml) cont~;ning 284 ppb of NMO~, which contained 6097 mg of NMM, 272 mg of M and 1085 mg of NMMO, were adjusted with ECl/NaOH to pH values of 4, 6, 7, 8, 10, 12 and 14. Afterwards, aqueous hydrogen peroxide having 30~
by weight of H2~2 was added in an amount to achieve a surplus of 1.3 mol, based on NMM, and it was heated to so~C for 4 hours. Afterwards, the yield of newly formed NMMO and the NMOR concentration were determined by means of HPLC (see Example 3). The results are graphically shown by means of Figs. 1 and 2.
In Fig. 1, the pH value is shown as the abscissa and the yield of NMMO produced (% of theory) as the ordinate. It can be clearly observed that there is a m~; mllm of about 50%
within the range of from 6.0 to 9Ø In Illustration 2, the pH value is also shown as the abscissa and the concentration (in ppb) of NMOR in the solution after oxidation as the ordinate. It can be seen that only starting from a pH value of 8-9 the formation of N-nitrosomorpholine increases significantly. Thus, in the range of from 6.0 to 9.0 the production of NMMO is m~; m; ~ed while the formation of the toxic N-nitrosomorpholine is simultaneously m; n; m; zed. This applies particularly to the pH range of from 7.0 to 9Ø
~.
PROCESS FOR THE PRODUCTION OF AN AQUEOUS SOLUTION OF N-M~'l'~YLMORPHOLINE-N-OXIDE
The present invention is concerned with a process for the production of a solution of N-methylmorpholine-N-oxide in water used in the amine-oxide process. The invention is further concerned with a process for the production of cellulose moulded bodies, particularly fibres and films.
For some decades there has been searched for processes for the production of cellulose moulded bodies 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 such as 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.
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 - o 356 419. For the purposes of the present specification and the present claims, the production of mouldable solutions of cellulose in tertiary amine-oxides and their further processing into moulded bodies is generally referred to as amine-oxide process.
In EP-A - 0 356 419, an amine-oxide process for the production of spinnable cellulose solutions is described, wherein as a starting material among others 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 _ CA 022300~0 1998-02-19 .
, ~ --2--step and continuously into a mouldable solution. Finally, the mouldable solution is spun into filaments by a forming tool such as a spinneret and the filaments are passed through a precipitation bath.
In the precipitation bath the cellulose is precipitated. The tertiary amine-oxide is accumulated in the precipitation bath. The precipitation bath may contain up to 30% by weight of amine-oxidè. For the economy of the amine-oxide process it is of vital importance to recover the amine-oxide as completely as possible and reuse it for the production of a mouldable cellulose solution. Thus it is necessary to recover NMMO from the precipitation bath.
In addition to the amine-oxide however, degradation products of the amine-oxide process are also accumulated in the precipitation bath. These degradation products may be intensively coloured, thus deteriorating the quality of the cellulose moulded bodies produced. On the other hand, other substances may represent an additional safety risk, since under certain conditions the amine-oxide tends to show highly exothermic decomposition reactions and these decomposition reactions may be induced or accelerated by certain substances. These substances have to be removed from the precipitation bath which is to be regenerated before the NMMO
is concentrated and separated.
After removing these unwanted substances, water is withdrawn from the purified precipitation bath which is optionally combined with other process liquids of the amine-oxide process such as vapour condensates formed during the production of the cellulose solution. This may be carried out for instance by means of evaporation. In the residue of this evaporation, highly concentrated aqueous amine-oxide is obtained which is recycled again into the amine-oxide process. The evaporation vapours consist primarily of water, wherein however significant amounts of N-methylmorpholine, the main decomposition product of NMMO, are also dissolved.
CA 022300~0 1998-02-19 Typically, the vapours contain e.g. up to 1000 mg of NMMO and 240 mg of N-methylmorpholine per litre. These vapours are conveniently concentrated, for instance by means of reverse osmosis.
To close the cycles as far as possible and also to keep the NMMO losses as low as possible, efforts are made to oxidize the N-methylmorpholine again to NMMO. This can be achieved for instance using a peroxide oxidant.
A process for the preparative production of tertiary amine-oxides by means of oxidation of tertiary amines is known ~or instance from EP-A - 0 092 862. According to this process, the amine-oxide is oxidized under pressure with molecular oxygen in an aqueous solvent, which solvent has a pH value approximately equal to or higher than the pKa value of the tertiary amine.
DD-A - 259 863 is concerned with the production of aqueous NMMO solutions by means of oxidation of N-methylmorpholine with H2O2 and passing the reaction solution through one or more exchanger columns filled with a styrene/divinylbenzene-copolymer cont~ining sulphonate groups, and by means of adjusting the pH value of the solution to values ranging from 8 to 5 by addition of phosphoric acid.
Oxidation of N-methylmorpholine with H2~2 to NMMO is known e.g. from EP-A - 0 254 803. From DE-A - 4 140 259 the production of NMMO is known, in which process the formation o~ nitrosamines is inhibited by scavenging primary and secondary amines e.g. with acid halides. EP-A - o 320 690 describes the production of amine-oxides substantially free of nitrosamines through oxidation with peroxides in the presence of a combination of CO2/ascorbic acid acting as a nitrosamine inhibitor. From EP-A - o 401 503, oxidation with H2~2 in water and a co-solvent, preferably a carboxylic acid ester, is known. According to FR-A - 8 808 039, oxidation is carried out while CO2 is added, and according to US-A -CA 022300~0 1998-02-19 ~, 5,216,154 oxidation to NMMO is carried out in a pure CO2 atmosphere.
Inspite of operating in largely closed cycles, the amine-oxide process involves solvent losses which are due to dilution steps during fibre purification, the deliverance of the fibre itself, and particularly to the chemical decomposition of NMMO under thermal stress during the process described in the literature (Lang H. et al., Cell. Chem.
Technol. 20, 1986, No. 3, page 289; and Taeger E. et al., Formeln, Faserstoffe, Fertigware 4, 1985, pages 14-22).
Inspite of numerous optimization efforts to mi nimi ze the decomposition behaviour (e.g. using chemical stabilizers), a complete prevention of such reactions has not been achieved so far. For these reasons, in the state of the art a regular feeding of NMM0 is necessary. According to EP-A - O 448 924 of the applicant, part of the NMMO decomposition products, particularly N-methylmorpholine (NMM), present in highly diluted solutions may be concentrated and afterwards reoxidized to NMMO in a known manner, which NMMO is introduced again into the amine-oxide process.
Although reoxidation of the decomposition product NMM
contained in the vapours to NMMO reduces the losses of expensive NMMO, it does not obviate the necessity of feeding to the amine-oxide process additionally up to several percent of NMMO per kilogramm of processed pulp. A drawback of this procedure consists in the high cost of technical ~MMO which has to be fed continuously to the amine-oxide process.
Thus it is the object of the present invention to overcome this drawback providing a process wherein the addition of fresh NMMO may be largely reduced or even avoided.
This objective is attained by a process for the production of a solution of N-methylmorpholine-N-oxide in water used in the amine-oxide process, characterized by the following steps that CA 022300~0 1998-02-19 (a) an aqueous solution (A) deriving from the amine-oxide process and cont~i n i ng N-methylmorpholine is provided;
whereafter (b) said solution (A) is mixed with a further aqueous solution tB) cont~i n i ng N-methylmorpholine, thus yielding a solution (C) which (c) is treated with an oxidant to oxidize N-methylmorpholine to N-methylmorpholine-N-oxide, whereby a solution (D) of N-methylmorpholine-N-oxide in water is produced which is used in the amine-oxide process.
It has proven convenient to add to solution (A) at least the same amount of N-methylmorpholine by means of solution (B) as contained in solution (A).
As an oxidant, a peroxide is best used.
It is known that the aqueous solution (A) derived from the amine-oxide process contains morpholine additionally to N-methylmorpholine. In the context of oxidation, this morpholine represents a preliminary stage of the toxic N-nitrosomorpholine. The inventors of the present invention have found that the formation of toxic N-nitrosomorpholine may be restrained when the solution (C) to be treated with the oxidant has a pH value of from 6.0 to 9Ø It has been shown that by simply adjusting the pH of the oxidation mixture within the indicated range it is possible to restrain the formation of toxic N-nitrosomorpholine while simultaneously achieving a m~; mllm oxidation of N-methylmorpholine to NMMO. The dependance of these two reaction ways on the pH can be observed in the attached drawings and is described in the Austrian patent application A 1398/95 of the applicant.
It has proven highly advantageous to adjust the pH value of the aqueous solution within the desired range by passing the solution to be processed through a cation exchanger capable of absorbing morpholine. This step has two important effects CA 022300~0 1998-02-19 .
on the reduction of nitrosamines. By means of the cation exchanger, morpholine is selectively removed from the solution, so that virtually no morpholine is available for the new formation of nitrosamines. Additionally, by separating the morpholine, which compared to other components has the highest basicity, the pH value of the solution is lowered precisely into the range wherein the production of NMMO reaches high values but the formation of nitrosamines is further impeded.
To separate morpholine, the cation exchanger best comprises carboxyl groups or sulphonic acid groups.
The small amounts of N-nitrosomorpholine formed inspite of the above-mentioned adjustment of the pH value may be largely destroyed by exposing the aqueous solution (C) during or after treatment with the peroxide oxidant to ultraviolet light substantially having a wavelength of 254 nm. The presence of the peroxide oxidant does not impede this destruction. The destruction of N-nitrosomorpholine using ultraviolet light is described in the Austrian patent application A 1401/95.
Working procedures for the quantitative analysis of nitrosamines using an exposure to ultraviolet light and a subsequent determination of the nitrites formed are known (D.E.G. Shuker, S.R. Tannenbaum, Anal. Chem., 1983, 55, 2152-2155; M. Rhighezza, M.H. Murello, A.M. Siouffi, J. Chromat., 1987, 410, 145-155; J.J. Conboy, J.H. Hotchkiss, Analyst, 1989, 114, 155-159; B. B~chele, L. Hoffmann, J. Lang, Fresen.J.Anal.Chem., 1990, 336, 328-333). However, these analytical working procedures do not deal with the destruction of N-nitrosomorpholine.
In the process according to the invention, H2~2 is preferably used as the peroxide oxidant. The H2~2 is preferably used in the form of an aqueous solution having 20-50~ by weight of CA 022300~0 1998-02-19 H2O2. The H2O2 is best used in an amount of from 0.8 to 2 mol per mol of N-methylmorpholine.
The ultraviolet light whereto the a~ueous solution is exposed is best emitted from a mercury low-pressure lamp. These low-pressure lamps have an intensity m~; mllm at 254 nm.
For an exposure to the light of a low-pressure lamp according to the invention, the lamp may be introduced into the vessel cont~i n i ng the process liquid to be treated. However, the lamp may also be arranged in a different manner. Moreover, exposure to the light may be carried out ~or instance also during a continuous circulation of the solution to be irradiated, i.e. exposed to ultraviolet light, within a thin-film ultraviolet light reactor.
The radiation intensity may range e.g. from 200 to 500 mJ/cm2, depending on the design of the lamp and the process conditions, particularly the temperature. AlSo this embodiment of the process according to the invention does not involve any additional chemicals.
To remove non-reacted N-methylmorpholine still present in solution (D), it has proven convenient to subject solution (D) to a distillation. During distillation, vapours are formed which after condensation yield solution (E), which may be used at least partly as solution (B).
The invention is further concerned with a process for the production of cellulose moulded bodies according to the amine-oxide process, wherein cellulose is dissolved in an aqueous NMMO solution to produce a mouldable solution, the solution obtained is moulded and after moulding passed into a precipitation bath, thus cellulose moulded bodies and a spent precipitation bath being produced, which precipitation bath is regenerated to recover NMMO, whereby an aqueous solution conta; ni ng N-methylmorpholine is obtained which, optionally together with the vapour condensates formed in the amine-CA 022300~0 1998-02-19 .
oxide process, is subjected to oxidation to produce a fresh aqueous NMMO solution which is used again for the production of a mouldable cellulose solution. This process is characterized in that fresh N-methylmorpholine is added to the solution cont~;n;ng N-methylmorpholine obtained when regenerating the spent precipitation bath, whereafter the solution is subjected to oxidation.
Thus, in the process according to the invention it is not NMMO but N-methylmorpholine which is fed to the amine-oxide process and oxidized to NMMo together with the N-methylmorpholine which is formed in the amine-oxide process due to the decomposition of NMMO and is contained in the different process liquids such as the vapour condensates which are formed when preparing the mouldable cellulose solution or evaporating the precipitation bath. Those skilled in the art are free to choose the moment when N-methylmorpholine is added to the process liquids deriving from the amine-oxide process without impairing the result of the process according to the invention.
By means of the following Examples, the invention will be explained in more detail. The abbreviations NMOR, NMMO, NMM
and M used in the following refer to N-nitrosomorpholine, N-methylmorpholine-N-oxide, N-methylmorpholine and morpholine respectively.
Example 1 A mixture of vapour condensates containing NMMO and NMM
formed when preparing the mouldable cellulose solution from the cellulose suspension and evaporating the precipitation bath to be regenerated is filtered and concentrated in a reverse osmosis arrangement. The retained residue thus obtained contains for instance about 7 kg of NMM and about 15 kg of NMMO per 1000 kg.
CA 022300~0 1998-02-19 , _g_ This solution is mixed with 44.3 kg of NMM per looo kg and introduced into a-reactor for oxidation. At 65 C, 79.5 kg of 22% H2~2 are added over a period of 10 minutes while the solution is stirred. After a reaction time of 7 hours at 70~C, not reacted NMM is evaporated from the solution at a reduced pressure of 100 mbar.
In the distillation residue rem~in~ an aqueous solution containing 51.8 kg of dissolved NMMO which is fed again into the amine-oxide process, i.e. may be used to produce the cellulose suspension.
The condensate produced by evaporation contains not reacted NMM (19.5 kg) and is mixed with 24.8 kg of NMM and fed to the following batch of residue.
Example 2 A mixture of vapour condensates cont~;ning NMMO and NMM
formed when preparing the mouldable cellulose solution from the cellulose suspension and evaporating the precipitation bath to be regenerated is ~iltered and concentrated in a reverse osmosis arrangement. The retained residue thus obtained contains for instance about 7 kg of NMM and about 15 kg of NMMO per loOo kg.
This solution is mixed with 44.3 kg of NMM per looo kg and thereafter purified by means of a cation exchanger. The purified solution is introduced into a reactor for oxidation.
At 65~C, 79.5 kg of 22% H2~2 is added over a period of 10 minutes while the solution is stirred. After a reaction time of 7 hours at 70~C, the solution is passed onto a further vessel and exposed to ultraviolet light having a wave length of 254 nm for 10 hours. Afterwards, not reacted NMM is evaporated from the solution at a reduced pressure of about 100 mbar and a temperature of 70~C.
" CA 022300~0 1998-02-19 .
In the distillation residue r~m~ins an aqueous solution cont~; n i ng 51.8 kg of NMMO. This solution is fed to the amine-oxide process, i.e. is used to produce the cellulose suspension.
The condensate produced by evaporation contains not reacted NMM (19.5 kg) and is mixed with 24.8 kg of NMM and fed to the following batch of retained residue.
Example 3 An aqueous solution containing 42 ~g of NMOR, 459 mg of NMMO, 4300 mg of NMM and 200 mg of M per litre was irradiated in an ultraviolet light reactor by means of a mercury low-pressure lamp (ultraviolet light lamp of the Katadyn EK-36 type, no.
79000; made by Ratadyn) (wavelength: 254 nm). The temperature of the aqueous solution was 60 C. The concentration of NMOR
was determined by means of HPLC (column: Hypersil ODS 250 x 4 mm; 50 C; eluant: A = 0.6% of acetonitrile; B = 49.7% of H2O;
gradient 1 ml/min; 10 min. - 100% of A; 7 min. - 100% of B;
detector: W 238 nm).
After an irradiation time of 150 minutes, the NMOR content in the process liquid declined to 40 ~g/l. After 150 minutes more, there was no more evidence of NMOR.
After there was no more evidence of NMOR, the irradiation was stopped, and it was re-~;ned for NMOR in time intervals of several hours. No more NMOR could be detected, thus being proven that NMOR will not be formed again.
Example 4 An aqueous solution cont~; n; ng 25 ~g of NMOR, 2530 mg of NMMO, 3923 mg of NMM and 30 mg of M per litre was mixed with 30% H2~2 for oxidation of NMM to NMMO (mol of NMM/mol ~f H2O2 = 1/1.2) and exposed to ultraviolet light as described in Example 3. Within the first 90 minutes, the NMOR
CA 022300~0 1998-02-19 concentration increased to 45 ~g/l, which is due to a fast reaction of the M present in the solution. Thereafter, the NMOR concentration decreased again significantly. After 6 hours, there was no more evidence of NMOR.
After a total oxidation time of 20 hours, the solution contained 5386 mg of NMMO/litre. This is equivalent to à
yield of 62% of theory.
Example 5 7 aqueous solutions (50 ml) cont~;ning 284 ppb of NMO~, which contained 6097 mg of NMM, 272 mg of M and 1085 mg of NMMO, were adjusted with ECl/NaOH to pH values of 4, 6, 7, 8, 10, 12 and 14. Afterwards, aqueous hydrogen peroxide having 30~
by weight of H2~2 was added in an amount to achieve a surplus of 1.3 mol, based on NMM, and it was heated to so~C for 4 hours. Afterwards, the yield of newly formed NMMO and the NMOR concentration were determined by means of HPLC (see Example 3). The results are graphically shown by means of Figs. 1 and 2.
In Fig. 1, the pH value is shown as the abscissa and the yield of NMMO produced (% of theory) as the ordinate. It can be clearly observed that there is a m~; mllm of about 50%
within the range of from 6.0 to 9Ø In Illustration 2, the pH value is also shown as the abscissa and the concentration (in ppb) of NMOR in the solution after oxidation as the ordinate. It can be seen that only starting from a pH value of 8-9 the formation of N-nitrosomorpholine increases significantly. Thus, in the range of from 6.0 to 9.0 the production of NMMO is m~; m; ~ed while the formation of the toxic N-nitrosomorpholine is simultaneously m; n; m; zed. This applies particularly to the pH range of from 7.0 to 9Ø
Claims (8)
1. A process for the production of a solution of N-methylmorpholine-N-oxide in water used in the amine-oxide process, characterized by the following steps that (a) an aqueous solution (A) deriving from the amine-oxyde process and containing N-methylmorpholine is provided; whereafter (b) said solution (A) is mixed with a further aqueous solution (B) containing N-methylmorpholine, thus yielding a solution (c) which (c) is treated with an oxidant to oxidize said N-methylmorpholine to N-methylmorpholine-N-oxide, whereby a solution (D) of said N-methylmorpholine-N-oxyde in water is produced which is used in said amine-oxide process.
2. A process according to Claim 1, characterized in that before treatment with said oxidant the pH value of said solution (C) is adjusted to a value ranging from 6.0 to 9Ø
3. A process according to Claim 1 or 2, characterized in that before treatment with said oxidant said solution (C) is passed through a cation exchanger capable of absorbing morpholine.
4. A process according to Claim 3, characterized in that said cation exchanger comprises carboxyl groups or sulphonic acid groups.
5. A process according to one of the Claims 1 to 4, characterized in that a peroxide is used as said oxidant.
6. A process according to one of the Claims 1 to 5, characterized in that during or after said treatment with said oxidant said aqueous solution is exposed to ultraviolet light substantially having a wavelength of 254 nm.
7. A process according to one of the Claims 1 to 6, characterized in that said solution (D) is subjected to distillation, whereby vapours are produced which after being condensed yield a solution (E), which is used at least partly as said solution (B).
8. A process for the production of cellulose moulded bodies according to the amine-oxide process, wherein cellulose is dissolved in an aqueous NMMO solution to produce a mouldable solution, said solution obtained is moulded and after moulding passed into a precipitation bath, thus cellulose moulded bodies and a spent precipitation bath being produced, which precipitation bath is regenerated to recover NMMO, whereby an aqueous solution containing N-methylmorpholine is obtained which, optionally together with the vapour condensates formed in said amine-oxide process, is subjected to oxidation to produce a fresh aqueous NMMO solution which is used again for the production of a mouldable cellulose solution, characterized in that fresh N-methylmorpholine is added to said solution containing N-methylmorpholine obtained when regenerating said spent precipitation bath, whereafter said solution is subjected to oxidation.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT0116596A AT404033B (en) | 1996-07-02 | 1996-07-02 | METHOD FOR PRODUCING AN AQUEOUS SOLUTION OF N-METHYLMORPHOLIN-N-OXIDE |
| ATA1165/96 | 1996-07-02 | ||
| PCT/AT1997/000147 WO1998000589A1 (en) | 1996-07-02 | 1997-07-01 | Process for preparation of an aqueous solution of n-methylmorpholin-n-oxide |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2230050A1 true CA2230050A1 (en) | 1998-01-08 |
Family
ID=3508020
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002230050A Abandoned CA2230050A1 (en) | 1996-07-02 | 1997-07-01 | Process for preparation of an aqueous solution of n-methylmorpholin-n-oxide |
Country Status (10)
| Country | Link |
|---|---|
| EP (1) | EP0874927A1 (en) |
| JP (1) | JPH11511764A (en) |
| CN (1) | CN1196762A (en) |
| AT (1) | AT404033B (en) |
| AU (1) | AU3327897A (en) |
| BR (1) | BR9706559A (en) |
| CA (1) | CA2230050A1 (en) |
| ID (1) | ID17544A (en) |
| NO (1) | NO980371L (en) |
| WO (1) | WO1998000589A1 (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19842556C2 (en) * | 1998-09-17 | 2003-02-06 | Alceru Schwarza Gmbh | Process for the production of cellulosic moldings |
| DE10323785B4 (en) | 2003-05-23 | 2009-09-10 | Wobben, Aloys, Dipl.-Ing. | Method for detecting an ice accumulation on rotor blades |
| CN104711706B (en) * | 2015-03-17 | 2016-10-05 | 中国纺织科学研究院 | The retracting device of Lyocell fiber spinning solution waste material and recovery method |
| CN109046475A (en) * | 2018-08-31 | 2018-12-21 | 山东英利实业有限公司 | The resource recycle method of N-methyl morpholine oxide in a kind of Lyocell fibers production process |
| CN110283145B (en) * | 2019-07-22 | 2021-04-06 | 山东英利实业有限公司 | Preparation method of N-methylmorpholine-N-oxide |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DD278365A1 (en) * | 1988-12-22 | 1990-05-02 | Thaelmann Schwermaschbau Veb | METHOD FOR GAS OXYNITRATION OF COMPONENTS OF IRON MATERIALS |
| WO1991004351A1 (en) * | 1989-09-22 | 1991-04-04 | Ashland Oil, Inc. | Process for protective finishing of ferrous workpieces |
| KR0125960B1 (en) * | 1994-04-27 | 1997-12-24 | 김은영 | Method for the purification of reclaimed aqueous n-methyl morpholine n-oxide solution |
| JPH10511144A (en) * | 1994-12-15 | 1998-10-27 | アクゾ ノーベル ナムローゼ フェンノートシャップ | Method for producing cellulosic molded article |
| AT402512B (en) * | 1995-08-18 | 1997-06-25 | Chemiefaser Lenzing Ag | METHOD FOR PROCESSING AN AQUEOUS PROCESS LIQUID OF THE AMINOXIDE METHOD |
| AT402510B (en) * | 1995-08-18 | 1997-06-25 | Chemiefaser Lenzing Ag | METHOD FOR PROCESSING AN AQUEOUS PROCESS LIQUID OF THE AMINOXIDE METHOD |
-
1996
- 1996-07-02 AT AT0116596A patent/AT404033B/en not_active IP Right Cessation
-
1997
- 1997-07-01 AU AU33278/97A patent/AU3327897A/en not_active Abandoned
- 1997-07-01 BR BR9706559A patent/BR9706559A/en not_active Application Discontinuation
- 1997-07-01 CA CA002230050A patent/CA2230050A1/en not_active Abandoned
- 1997-07-01 JP JP10503662A patent/JPH11511764A/en active Pending
- 1997-07-01 EP EP97929010A patent/EP0874927A1/en not_active Withdrawn
- 1997-07-01 ID IDP972286A patent/ID17544A/en unknown
- 1997-07-01 CN CN97190801A patent/CN1196762A/en active Pending
- 1997-07-01 WO PCT/AT1997/000147 patent/WO1998000589A1/en not_active Application Discontinuation
-
1998
- 1998-01-28 NO NO980371A patent/NO980371L/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| JPH11511764A (en) | 1999-10-12 |
| ATA116596A (en) | 1997-12-15 |
| BR9706559A (en) | 1999-07-20 |
| NO980371D0 (en) | 1998-01-28 |
| ID17544A (en) | 1998-01-08 |
| EP0874927A1 (en) | 1998-11-04 |
| AT404033B (en) | 1998-07-27 |
| AU3327897A (en) | 1998-01-21 |
| CN1196762A (en) | 1998-10-21 |
| NO980371L (en) | 1998-01-28 |
| WO1998000589A1 (en) | 1998-01-08 |
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