EP3728332A1

EP3728332A1 - Method for producing cellulose carbamate, cellulose carbamate and also mouldings produced therefrom

Info

Publication number: EP3728332A1
Application number: EP17829196.9A
Authority: EP
Inventors: Andrè LEHMANN; Stephan Lang
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 2017-12-21
Filing date: 2017-12-21
Publication date: 2020-10-28
Also published as: WO2019120529A1

Abstract

The invention relates to a method for producing cellulose carbamate by reacting cellulose and urea at elevated temperature in an organic reaction medium. The products resulting from this method are characterized by good solubility in sodium hydroxide solution and are particularly suitable for producing cellulose mouldings, for example regenerated cellulose fibres, films and beads.

Description

Process for the preparation of cellulose carbamate, cellulose carbamate and molded articles produced therefrom.

The invention relates to a process for the preparation of cellulose carbamate by reacting cellulose and urea at elevated temperature in an organic reaction medium. The products resulting from this process are distinguished by a good solubility in sodium hydroxide solution and are particularly suitable for the production of shaped cellulose articles, for example regenerated cellulose fibers, films and beads.

State of the art:

Cellulose carbamate is usually made by heating a homogeneous as possible NEN mixture of cellulose and urea at temperatures above 130 ° C ago. This reaction can be carried out either in the absence of a liquid reaction medium or in the presence of an inert organic liquid as a slurry process. The reaction without liquid reaction medium is to the effect of part, that the heat transfer are bad, which is local to Überhit tongues and thus inhomogeneous process temperature control. This results in an uneven substitution pattern of the carbamate moieties within the cellulose, severely adversely affecting product quality in terms of solubility behavior.

If an inert organic reaction medium is used, improvements in product quality can be achieved due to the improved heat transfer from the reactor to the reaction mixture (DE4417140). For example, US 5,906,926 describes the use of high boiling hydrocarbons, e.g. Toluene or xylene.

A disadvantage of the known slurry process is that due to the Verwen tion of a high excess of inert organic reaction medium based on the cellulose and considering a guaranteed mixing of the system, the material space yield is lower than Ver drive, which without inert, organic reaction medium be performed. At the same time, the use of an inert, organic reaction medium means increased work-up expenditure with regard to the separation of the cellulose carbamate as end product. The use of xylene as an inert organic reaction medium is most commonly used (e.g., US 5,906,926, WO 2004/046198). The published in the patent literature excess of xylene based on the weight of the cellulose is from 23 to 17 times, under the specification as a product in sodium hydroxide solution, completely soluble, to obtain cellulose acetate.

Starting from the disadvantages described above, it is an object of the present invention to provide a new and improved process for the preparation of cellulose carbamate, in which the proportion of organic reaction medium, which is compellingly described as very high in the prior art, is reduced, without this at the expense of the product qualities obtained or leads to losses in the conversion of the reaction. The procedural products produced should in particular have a good solubility in sodium hydroxide solution and have excellent mechanical properties. The object is achieved in terms of a method having the features of Pa tentanspruchs 1, with respect to a novel cellulose carbamate with the features of claim 15. Claim 19 discloses moldings comprising or consisting of the cellulose carbamate according to the invention. The respective dependent claims represent advantageous developments.

The present invention thus relates to a process for the preparation of cellulose carbamate, in which a) activation of cellulose, b) addition of an inert organic reaction medium in a mass ratio of 10: 1 to 0.1: 1 (reaction medium: cellulose) and urea in in any order, and c) reaction of the reaction mixture under mechanical agitation at reaction temperatures of more than 100 ° C.

Thus, the present invention makes it possible to produce cellulose carbamate with significantly reduced use of an inert organic reaction medium. Instead of an increased proportion of reaction medium in this case resorted to mechanical agitation. For example, the reaction is carried out in reactor systems which ensure intensive mixing at high substance density (eg kneader). It was surprisingly found that the amount of inert, organic reaction medium could be significantly reduced thereby, without reducing the product quality. This has a particularly positive effect on the downstream processing of the products obtained. Since considerably less reaction medium is present, the separation of the products from the reaction medium is much less energy-intensive and therefore more economical. In addition, the yield of material in the process according to the invention is higher than in the processes known from the prior art which use more reaction medium. Likewise, the reduced proportion of the reaction medium has a positive effect on the Stoffrau mausbeute. Surprisingly, the products obtained are also completely soluble in aqueous sodium hydroxide solution. The pro- Duct qualities are repro ducible at any time with the method according to the invention.

The invention described herein relates to an improved process for the preparation of cellulose carbamate with significantly reduced use of an inert, organic reaction medium. In comparison to the described United drive (US 5,906,926, WO 2004/046198) can be produced under simple reaction and Aufarbeitungsbedin conditions in sodium hydroxide-soluble cellulose carbamates. Along with the reduced use of an inert, organic reaction medium by more intensive mixing of the Reacti onsansatzes, solutions of the cellulose carbamates thus produced show significantly lower viscosity-corrected filter values, which suggests a verbes serten solution state, whereby a higher spin safety is ensured.

In addition, the improved procedure makes it possible to realize narrower polydispersities of the cellulose carbamates produced and to produce narrow molar mass distributions as are the state of the art in the industrial production of cellulosic staple fibers.

In a preferred embodiment, the mass ratio of the inert organic reaction medium to cellulose is 7.5: 1 to 0.5: 1, preferably 6: 1 to 1: 1, more preferably 5: 1 to 2: 1, particularly preferably 4.5 : 1 to 3: 1.

In particular, the mechanical agitation of the reaction mixture is carried out in a kneader.

The reaction mixture is preferably reacted over a period of from 10 minutes to 48 hours, preferably from 20 minutes to 24 hours, more preferably from 30 minutes to 8 hours, and / or at temperatures of from 75.degree. C. to 220.degree. C., preferably from 90.degree 200 ° C, more preferably from 100 ° C to 180 ° C.

The activation of the cellulose takes place in a preferred embodiment by conversion into alkali cellulose using a 5 to 50% by weight, preferably 7.5 to 30% by weight, particularly preferably 10 to 20% by weight aqueous alkali metal hydroxide solution, especially sodium hydroxide, at temperatures from 0 ° C to 90 ° C, preferably 10 to 60 ° C, and / or over a period of 5 minutes and 48 hours, preferably 10 minutes and 24 hours, more preferably 10 minutes and 10 hours.

The activation can also be carried out mechanically, hydrothermally and / or enzymatically.

In particular, it is preferred if, after step a) and before step b), the alkali cellulose obtained during activation is ripened, especially at temperatures of from 0 ° C. to 120 ° C., preferably from 10 ° C. to 100 ° C., more preferably from 20 ° C to 60 ° C, and / or over a period of 10 minutes to 48 hours, preferably from 12 hours to 24 hours. After step a) and before step b), in particular after ripening according to the preceding claim, the alkali metal cellulose can be washed out to an alkali content of <5% by weight with water.

A further advantage is that the urea after addition over a period of 5 minutes to 48 hours, preferably 10 minutes to 24 hours and / or at temperatures of 0 ° C to 90 ° C, preferably 10 ° C to 80 ° C, especially preferably from 15 ° C to 70 ° C is intercalated into the cellulose.

According to a further preferred embodiment, the urea is used in egg nem ratio of 0.05: 1 to 3: 1, preferably 0.5 to 2: 1, based on the anhydroglucose unit of the cellulose.

Likewise, it is possible that before the reaction in step c) a partial Ent train of water from the reaction mixture is carried out, in particular under ge ambient pressure compared to reduced pressure and / or at temperatures of 20 to 100 ° C.

After completion of the reaction, the cellulose carbamate can be separated from the liquid phase, optionally washed with water and then dried. In particular, the inert organic reaction medium is selected from the group consisting of toluene, o-xylene, p-xylene, tetralin, decalin, cumene and mixtures thereof.

According to a preferred embodiment, the DP _CUOx (measured according to SCAN-CM 15:99) of the cellulose used is 500 to 150, preferably 400 to 200, particularly preferably 350 to 250.

An exemplary, in particular preferred method sequence according to the invention provides for the following steps:

A process for the preparation of cellulose carbamate in an organic reac tion medium with the following reaction steps a) activation of the pulp by a. Treatment with 10-20% aqueous sodium hydroxide solution for 10 minutes to 10 hours at temperatures of 10.degree. C. to 60.degree

b.

c. Pre-ripening of the resulting alkali cellulose from 10 min to 48 h at temperatures of 20 ° C to 80 ° C d. washing the alkali cellulose to an alkali content of <5%. b) intercalating the urea in the activated cellulose at temperatures of 15 to 70 ° C for 10 min to 24 h, wherein the amount of urea 0.05: 1 to 3: 1 based on the anhydroglucose unit. c) optional, partial removal of the water from the reaction mixture by applying a vacuum at temperatures of 20-100 ° C. d) adding the inert, organic reaction medium in a mass ratio of 7.5: 1 to 1: 1 based on cellulose e) conversion of the cellulose to cellulose carbamate at reaction temperatures of 100 ° C to 180 ° C within 30 min to 8 h after reaching the reaction temperature f) separation of the cellulose carbamate as a reaction product from the liquid phase g) washing of the reaction product with water h) drying of the cellulose carbamate

The present invention also relates to a cellulose carbamate which can be prepared according to the method of the invention described above.

In particular, the cellulose carbamate according to the invention is characterized by a viscosity-corrected filter value (k _r ), determined according to leaflet 1116 B / 68, 1968, from the association of pulp and paper chemists and engineers, from 2000 to 15000.

The DP _cuo x (measured according to SCAN-CM 15:99) of the cellulose carbamate is in this case preferably from 200 to 500, preferably 230 to 400.

More preferably, the polydispersity index (PDI), determined by means of GPC-MALLS after saponification with subsequent tricarbanilination of the cellulose carbamates, of the cellulose carbamate according to the invention is from 1.5 to 5.0, preferably 2.0 to 4.0.

The present invention also relates to moldings comprising or consisting of the previously described inventive cellulose cellulose. In particular, the shaped bodies are in the form of fibers, films or beads. The present invention will be explained in more detail with reference to the following embodiments, but without limiting the invention thereto.

embodiments

Example 1 - Comparative Example Pulp _{plates of} a sulfite pulp (DP _Cu0 x: 760) was _immersed by means of a dip press for 50 min at 35 ° C in 17.9% aqueous sodium hydroxide solution and pressed at closing to a Abpressfaktor of 2.9. The obtained acellulose was fed to a pulper where it was pulped for 1 h. Subsequently, the maturity for 29 h at 35 ° C. The resulting alkali cellulose was mashed with distilled water and separated from the adhering alkali by means of a washing centrifuge, so that only a residual alkali content of 1.4% was present and the cellulose content was 32.0%. The DP of the washed alkali cellulose was DP _Cu0 x: 350.

429.4 g of the thus activated cellulose were added to 61.8 g of urea and this intercalated for 2 h. The reaction mixture was fed to a 21 stirred reactor and 2.5 I o-xylene was added (ratio CelhXyl 1: 18.2). Using vacuum (90 mbar) and adjusted flow temperature, the water contained in the reaction mixture was separated off within 4 h using a water separator. The reaction temperature was adjusted to 146 ° C and the reaction was carried out for 2h under reflux.

The reaction mixture was subsequently separated from xylene and washed several times with distilled water. The air-dried cellulose _{carbamate had} a nitrogen content of 2.89% and a DP _Cu0 x of 313 and was completely soluble in 9% sodium hydroxide solution. The viscosity-corrected filter value (kr) of this solution (determined according to leaflet II 1/6 B / 68 from the Association of Pulp and Paper Chemists and Engineers) was 12473. The molecular weight determination by GPC after saponification gives a polydispersity index (PDI) of 3 , 7th

Example 2

The activation of the pulp was carried out analogously to the geschilder in Example 1 th procedure and gave a washed out alkali cellulose with a residual alkali content of 1.3% and a cellulose content of 30.2%. The DP of the washed out alkali cellulose was DP _Cu0 x: 335.

To 1725 g of urea was added to 1325 g of the so-activated cellulose, and the water was intercalated in a 2-cell reaction kneader for 2 h. U.N- ter using vacuum (100 mbar) and adjusted flow temperature was within 3 h, the water contained in the reaction mixture abge separated. Thereafter, 2.01 o-xylene was added to the reaction mixture (ratio CelkXyl 1: 5). The reaction temperature was set to 133 ° C and the reaction was carried out for 2 hours.

The reaction mixture was subsequently separated from xylene and washed several times with distilled water. The air-dried cellulose _{carbamate had} a nitrogen content of 2.91% and a DP _Cu0x of 266 and was completely soluble in 9% sodium hydroxide solution. The viscosity-corrected filter value (kr) of this solution (determined according to leaflet II 1/6 B / 68 from the Society of Pulp and Paper Chemists and Engineers) was 2341. The molecular weight determination by GPC after saponification gives a polydispersity index (PDI) of 2 ; 2.

According to these reaction schemes, the amount of xylene was varied, other parameters kept constant. It was also carried out for comparison purposes, a game without reaction medium. The resulting cellulose caramates had the following characteristics:

Example 3

Pulp plates of a prehydrolysis kraft pulp (DP _Cu0x : 611) were pre- _ripened for 35 h at 35 ° C. and then washed almost free of alkali (as described in Ex. 1). The residual alkali content was 1.23% and the cellulose content 30.3%, wherein the cellulose has a DP _Cu0x : 323. To 1321 g of the thus activated cellulose, 100 g of urea were added and this was intercalated in a 51 kneader with 2 Sigmaschaufeln for 2 h. Using vacuum (100 mbar) and adjusted flow temperature was within 2 h, the water contained in the reaction mixture separated abge. Thereafter, 2.41 o-xylene were added to the reaction mixture (ratio CelkXyl 1: 5). The reaction temperature was set to 136 ° C and the reaction was carried out for 2 hours.

The reaction mixture was subsequently separated from xylene and washed several times with distilled water. The air-dried cellulose _{carbamate had} a nitrogen content of 2.43% and a DP _Cu0x of 248 and was completely soluble in 9% sodium hydroxide solution.

After these reaction schemes, the amount of urea was varied, other parameters kept constant. The resulting cellulose carbamates had the following characteristics:

Claims

claims

1. A process for the preparation of cellulose carbamate, wherein

a) activation of cellulose,

b) adding an inert organic reaction medium in a mass ratio of 10: 1 to 0.1: 1 (reaction medium: cellulose) and urea in any order, and

c) reaction of the reaction mixture under mechanical agitation at reaction temperatures of more than 100 ° C.

2. The method according to claim 1, characterized in that the mass ratio of the inert organic reaction medium to cellulose 7.5: 1 to 0.5: 1, preferably 6: 1 to 1: 1, more preferably 5: 1 to 2: 1 , Be particularly preferably 4.5: 1 to 3: 1.

3. The method according to any one of the preceding claims, characterized in that the mechanical agitation of the reaction mixture is carried out in a kneader.

4. The method according to any one of the preceding claims, characterized in that the reaction of the reaction mixture

over a period of 10 minutes to 48 hours, preferably 20 minutes to 24 hours, more preferably 30 minutes to 8 hours, and / or

at temperatures of 75 ° C to 220 ° C, preferably from 90 ° C to 200 ° C, more preferably from 100 ° C to 180 ° C.

he follows.

5. The method according to any one of the preceding claims, characterized in that the activation of the cellulose by conversion into alkali cellulose using a 5 to 50 wt .-%, preferably 7.5 to 30 wt .-%, more preferably 10 to 20 wt .-% aqueous alkali hydroxide, in particular sodium hydroxide, at temperatures of 0 ° C. to 90 ° C, preferably 10 to 60 ° C, and / or over a period of 5 min and 48 h, preferably 10 min and 24 h, more preferably 10 min and 10 h

he follows.

6. The method according to any one of the preceding claims, characterized in that the activation of the cellulose is mechanical, hydro-thermal and / or enzymatic.

7. The method according to any one of the preceding claims, characterized in that after step a) and before step b) the alkali cellulose obtained in the Akti is ripened, in particular

at temperatures from 0 ° C to 120 ° C, preferably from 10 ° C to 100 ° C, more preferably from 20 ° C to 60 ° C, and / or

over a period of 10 minutes to 48 hours, preferably 12 hours and 24 hours Ver drive according to one of the preceding claims, characterized in that after step a) and before step b), in particular after he maturation according to the preceding claim, the alkali cellulose is washed out to an alkali content of <5% by weight with water.

8. The method according to any one of the preceding claims, characterized in that the urea after addition

over a period of 5 minutes to 48 hours, preferably 10 minutes to 24 hours and / or

at temperatures of 0 ° C to 90 ° C, preferably 10 ° C to 80 ° C, more preferably from 15 ° C to 70 ° C.

is intercalated into the cellulose.

9. The method according to any one of the preceding claims, characterized in that the urea in a quantitative ratio of 0.05: 1 to 3: 1, preferably 0.5 to 2: 1 based on the

Anhydroglucose unit of cellulose is used.

10. The method according to any one of the preceding claims, characterized in that prior to the reaction in step c) a partial Ent train of water from the reaction mixture, in particular un ter to ambient pressure reduced pressure and / or at temperatures of 20 to 100 ° C. ,

11. The method according to any one of the preceding claims, characterized in that after completion of the implementation of the

Cellulose carbamate separated from the liquid phase, optionally washed with water and then dried.

12. The method according to any one of the preceding claims, characterized in that the inert organic reaction medium is selected out of the group consisting of toluene, o-xylene, p-xylene, tetralin, decalin, cumene and mixtures thereof.

13. The method according to any one of the preceding claims, characterized in that the DP _CUO x (measured according to SCAN-CM 15:99) of the cellulose used 500 to 150, preferably 400 to 200, particularly preferably 350 to 250.

14. Cellulose carbamate, preparable by a process according to any one of the preceding claims.

15. Cellulose carbamate according to the preceding claim, characterized by a viscosity-corrected filter value (k _r ), determined according to leaflet 1116 B / 68 from the Association of Pulp and Paper Chemists and Engineers, 1968, from 2000 to 15000.

16. Cellulose _carbamate according to one of the two preceding claims, characterized by a DP _CUO x (measured according to SCAN-CM 15:99) of 200 to 500, preferably 230 to 400.

17. Cellulose carbamate according to any one of claims 15 to 17, gekennzeich net by a polydispersity index (PDI), determined by GPC MALLS after saponification with subsequent tricarbanilination of the cellulose carbamates, from 1.5 to 5.0, preferably 2.0 to 4.0 ,

18. Shaped body, comprising or consisting of cellulose carbamate according to any one of claims 15 to 18, in particular in the form of fibers, foils or beads.