NZ330917A

NZ330917A - Process for producing cellulose derivatives where ammonia activated cellulose is impregnated with alkali solution and then subjected to either a substitution or addition reaction

Info

Publication number: NZ330917A
Application number: NZ330917A
Authority: NZ
Inventors: Ties Karstens; Armin Stein
Original assignee: Rhodia Acetow Ag
Priority date: 1996-11-08
Filing date: 1997-11-04
Publication date: 1999-10-28
Also published as: JPH11504071A; DE19646213C2; HUP9902022A3; DE59706307D1; AU699832B2; EP0873364A1; PL327691A1; AU5316998A; CZ213998A3; EA001008B1; BR9707116A; CA2241800A1; MX9805511A; KR19990077026A; EA199800629A1; ID20424A; CZ289562B6; ATE212999T1; TR199801312T1; EP0873364B1

Abstract

Disclosed is a method for producing cellulose derivatives wherein cellulose is impregnated with an alkali solution, the impregnated cellulose is selectably pressed out, and the cellulose undergoes a substitution or addition reaction, whereby the cellulose derivative is obtained with a degree of substitution DS. The applied cellulose is an ammonia activated cellulose. The molar ratio of the alkali to the AHG (anhydro glucose unit) in the cellulose at the beginning of the substitution or addition reaction does not exceed twice the valve of the desired DS. For the swelling of cellulose, no excess of alkali is required, which does not react to produce alkali cellulose but only adheres to the cellulose as a loose association product. Reagent consumption in the substitution or addition reaction is lower. Fewer secondary products are formed.

Description

<div class="application article clearfix" id="description"> New Zealand Paient Spedficaiion for Paient Number 330917 New Zealand No 330917 International No PCT/EP97/06089 TO BE ENTERED AFTER ACCEPTANCE AND PUBLICATION Priority dates 08 11 1996, Complete Specification Filed 04 11 1997 Classification (6) C08B1/00,02,06,08 Publication date 28 October 1999 Journal No 1445 r. i /INJCB'S NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION Title of Invention Method for producing cellulose derivatives Name, address and nationality of applicant(s) as in international application form RHODIA ACETOW AG, Engesserstrasse 8, D-79108 Freiberg, Federal Republic Of Germany Process for producing cellulose denvatives The invention relates to a process for producing cellulose derivatives, with which the cellulose is impregnated with an alkali solution, the impregnated cellulose is optionally pressed and the cellulose is subjected to a substitution or addition reaction, wherein a cellulose derivative with a substitution degree DS is obtained Most substitution reactions of cellulose take place via alkali cellulose as intermediate stage Here a distinction is made between reactions with alkali consumption, e g the production of methyl or ethyl cellulose by reaction with the corresponding alkyl halogemdes, the production of carboxy-methyl cellulose by reaction with chloracetic acid or its sodium salt, or the production of cellulose xanthogenate by reaction with carbon disulphide, and reactions without alkali consumption, e g the production of hydroxy-ethyl and hydroxy-propyl cellulose by reaction of the alkali cellulose with ethylene oxide or propylene oxide, or the production of cyano-ethyl cellulose by reaction with acrylomtrile Cleaned cellulose is converted to alkali cellulose by treating it with alkali, in the industry practically exclusively soda lye (alkalisation) It is assumed that in the alkali cellulose part of the cellulose is present m the form of a hydrated alcoholate Cell-0~Na+ H* OH' The soda lye furthermore serves to swell the cellulose and make it accessible to the reaction partners of the subsequent derivation reactions In the amorphous part of the cellulose the cellulose alcoholate is formed relatively easily So that this will also occur for the crystalline part of the cellulose, certain conditions must be maintained with regard to the temperature and concentration of the soda lye Only when the concentration of soda lye is sufficiently high, will the lattice of soda cellulose 1 be formed, which during the washing (regenerating) changes over to the lattice of cellulose II (regenerated cellulose) During the conversion of cellulose I to soda cellulose 1, the distances of the 101-lattice planes of about 7 are widened to approximately 12 A This change can also be noted by looking at the apparent density Cellulose material with a high crystalhnity has a FRE SPA nnr high resistance to alkalisation In piactice only a narrow NaOH-concentiation range produces alkali celluloses suitable for industrial use With the known industrial piocesses the pre-comminuted cellulose is immeised in 18-20% aqueous soda lye (lye ratio at least 10 1) A large part of the soda lye is subsequently removed again by pressing However, when doing so normally a composition of approximately 34% by mass cellulose and 66% by mass aqueous NaOH (steeping and pressing) is obtained or of only 25% by mass cellulose and 75% by mass NaOH (slurry and roller press) A large part of the soda lye remaining behind m this cellulose is, however, not used for the subsequent derivation reactions, but adheres as loose associate to the cellulose and is not removed during the pressing A washing out with water is not possible, as this dilutes the soda lye and the initial modification would again occur The amount of soda lye which is excess for the production of the cellulose derivatives causes during the derivation reactions a high reagent consumption, which generally is associated with a salt formation and the formation of byproducts During the xanthogenation the excess soda lye reacts with carbon disulphide to, for example, the undesirable tritlno-carbonate The salts as well as the by-products must be separated, to some extent at high expense and must be disposed of or processed For the cellulose ethers, the costs for this already amount to 20% of the production costs For the production of viscose via cellulose xanthogenate, because of the strict official environmental protection requirements, considerable costs are also required for cleaning the waste water Notwithstanding the high excess of soda lye used with the known process, it is found that in the derivatives produced via alkali cellulose as intermediate stage, inhomogeneous substituent distributions are present In cellulose ethers these can be noted, for example, by a too low solubility, a too great turbidity and a too low flocculation temperature SWORN 1RANSLAT0R GFP rpr en* « It has already been reported that with activated cellulose compared to untreated cellulose, the lattice conversion from cellulose I to soda cellulose I takes place aheady at a considerably lower NaOH concentration In this connection we refer to Schleicher, Daniels and Philipp, m "Faserfoischung imd Textiltechnik" 24 (1973) p 371 to 376 and WO 96/30411 Howevei, these publications do not suggest that with a view to the subsequent derivation reactions the absolute quantity of alkali, i e the molar NaOH/AHG ratio (AHG = anhydroglucose unit), could play a iole It is, therefore, the object of the invention to make available a process mentioned at the outset, which does not have the indicated disadvantages of the state of the art, or at least to piovide a useful alternative It is a particular object of the invention to make available a piocess of the type mentioned at the outset, with which at the beginning of the derivation reaction only a small excess or a stoichiometric or even a sub-stoichiometric quantity of alkali is present, or at least to provide a useful alternative According to the invention this object is achieved by a process for producing cellulose derivatives with which a) cellulose is impregnated with an alkali solution, b) the impregnated cellulose is optionally pressed and c) the cellulose is subjected to a substitution or addition reaction, wherein a cellulose derivative with a substitution degree DS is obtained, which is characterised in that the cellulose used is an ammonia-activated cellulose and the molar ratio of alkali to AHG m the cellulose at the beginning of step c) does not exceed 2 times the DS To be understood under "alkali solution" are aqueous or alcoholic solutions of alkali metal or alkaline earth metal hydroxides, oxides and/or carbonates Preferably, the alkali solution is aqueous oi alcoholic soda lye or potassium lye The alcoholic solutions preferably contain methanol, ethanol and/or isopropanol as cnl,7pnt M|TELLECTUAL PROPERTY OFHCE buivem 0FN2 2 7 AUG 1999 RECEIVED j With processes according to the invention, alkali solutions with a low concentration are already effective since for the successful further conversion a transformation by alkali to the cellulose Il-lattice is not necessary, seeing that as a result of the activation a new cellulose modification with widened lattice has already occuned Generally, concentrations of approximately 12% by mass or less are suitable Preferably, the alkali solution has a concentration of less than approximately 10, in particular less than approximately 8% by mass Concentrations of approximately 1 to 6% by mass are particularly suitable The molar alkali/AHG ratio at the beginning of step c) does not exceed 2 times, preferably 1 5 times, in particular 1 1 times the desired substitution degree In particular, in the case of alkali-consuming reactions a stoichiometric alkali/AHG ratio can be used To be understood under stoichiometric is a molar alkali/AHG ratio which lies close to the desired substitution degree of the end product With reactions which are only catalysed by alkali, it is even possible to use a sub-stoichiometnc ratio with respect to the desired substitution degree The substitution or addition reaction can preferably be brought about by reaction with carbon disulphide, acyl-group transferring reagents, such as carboxylic acid anhydrides, e g acetic anhydride, isopropenyl acetate, dicarboxyhc acid anhydrides, e g phthalic anhydride, succinic anhydride, glutanc anhydride, maleic anhydride, carboxylic acid chlorides, e g propionic chloride, steaiylic chloride, carboxylic acids, e g formic acid, alkyl-group transferring reagents such as methyl chloride, ethyl chloride, benzyl chloride, alkene oxides, such as ethylene oxide, propylene oxide, styrene oxide, a-halocarboxylic acids, such as chloracetic acid, or their salts, a,P-unsaturated carbonyl compounds or acrylonitnle In addition, sometimes a catalyst such as, for example, benzyl trimethyl ammonium chloride, tetrabutyl ammonium chloride, -hydroxide, hydrogen sulphate, Ti(OR)^, imidazole, N-methyl imidazole, Li-, Na- and Mg-acetate is advantageous The SWORN TRANSLATOR GER FRE SPA OUT reaction can take place in an aqueous medium or an organic solvent, such as NMP, DMAc, DMSO, DMF, dioxan, THF, iso-propanol, tert-butanol or mixtures thereof With the process according to the invention ammonia-activated cellulose must be used "Ammonia activation" means that the cellulose has been treated under high pressure with liquid ammonia and subsequently the pressure of the system has been released Native cellulose is a polysaccharide which, because of the formation of lntermolecular hydrogen bridge bonds, comprises crystalline parts The ammonia molecu'p. because of its nucleophilic properties, is able to push itself between the cellulosic OH-groups This ensures a swelling and widening of the lattice During the subsequent pressure release the ammonia evaporates for the greater part When doing so, the degree of swelling or the widening of the lattice decreases again and assumes a value between the complete swelling and the untreated cellulose The known processes for the ammonia activation of cellulose can be divided into the simple ammonia expansion and the so-called ammonia explosion With both the cellulose is treated with liquid ammonia in a pressure vessel With the ammonia expansion technology, by opening a valve with a small bore on the pressure reactor, it is ensured that under a reduction of the pressure part of the liquid ammonia escapes from the pressure vessel m the gaseous form The cellulose remaining behind in the pressure reactor does not release all the liquid ammonia, but approximately 50% of the ammonia used remains behind in the cellulose Such a process is described, for example, in the DE 43 29 937 CI With the ammonia explosion technology, the volume available to the system cellulose/liquid ammonia is increased m an explosion-like manner whilst reducing the pressure For the practical implementation thereof, on the pressure reactor a valve with a large bore can be opened, when the cellulose and ammonia are flung in sudden bursts out of the pressure tank into an explosion or collecting chamber With this the greater part of the ammonia evaporates from the cellulose, only a small residual ammonia content remains behind, the amount of which depends on the process parameters SWORN TRANSLATOR GFR FRF SPA flIIT Foi the purposes of the invention the activated cellulose preferably has a LODP-value ("Limiting Degree of Polymerisation" or "Levelling-off Degree of Polymerisation" (LODP-value), see Hans A Krassig "Polymer Monographs", Vol 11, Goidon and Breach Science Publishers, in particular p 191 et seq ) of between appioximately 100 and 160 and in particular between appioxunately 120 and 145 Preferably, the activated cellulose is in the form of fluff and is chaiacterised by a low density of less than approximately 0 2 g/cm3, in particular less than approximately 0 1 g/cm1 Activated cellulose had a widened space-reticular structuie as well as a high specific surface with high accessibility Preferably, the activated cellulose is obtained by a process with which the cellulose is brought into contact with liquid ammonia at an initial pressure higher than atmospheric pressure and at a temperature of at least approximately 25°C, wherein the quantity of the liquid ammonia suffices at least to wet the surface of the cellulose and the volume available to the system cellulose/liquid ammonia is increased m an explosion-like manner whilst reducing the pressure by at least 5 bar When the term "explosion-like" is used here, this must be seen m the narrow sense Preferably, the explosion-like increase in volume takes place within less than one second, in particular less than 0 5 seconds A continuous process is based on an incremental cellulose/liquid ammonia quantity The cellulose preferably is brought into contact with the liquid ammonia m a pressure device, and the pressure of the system cellulose/liquid ammonia is reduced by transferring it into an explosion chamber with a volume that is larger than that of the pressure device Preferably, the starting pressure lies between approximately 5 and 46 bar, in particular between approximately 25 and 30 bar The minimum drop in pressure of 5 bar is critical Below this no adequate activation of the cellulose will be obtained Exceeding the upper limit value of approximately 46 bar will not result in further advantages The obtaining of such a value requires a relatively great amount of apparatus, so that from a practical point of view a further increase does not make SWORN TRANSLATOR GER FRE SPA OUT, sense The temperature of approximately 25 to 85°C or 55 to 65°C correlates with the indicated pressure frame Preferably, the starting pressure m the system cellulose/liquid ammonia is reduced m an explosion-like mannei by at least approximately 10 bar and, in particular, approximately 30 bar Preferably, the explosion takes place in an explosion chamber which is kept under vacuum This explosion chamber must be chosen sufficiently large so as to obtain in the large volume the desired separation into fibies or defibrillation Preferably, the ammonia is drawn off from the explosion chamber, condensed again and fed back into the process A sufficient quantity of ammonia must be pressed into the pressure device, so that under the pressure and temperature conditions required according to the invention liquid ammonia will be present and at least the surface of the cellulose is wetted Preferably per 1 part by mass of cellulose at least approximately 1 part by mass, m particular approximately 5 to 10 parts by mass of liquid ammonia are used As a result of the ammonia an at least partial swelling of the cellulose takes place The preferred activation process can be earned out discontmuously or continuously With the discontinuous process the apparatus essentially comprises a pressure tank which can be filled with the material to be treated, and a collecting or expansion tank connected to same by way of a valve Here it must be ensured that the valve, when open, has a large opening so that during the explosion the cellulose material will not dam up and not only ammonia will escape The expansion tank has a much larger volume than the pressure tank, e g the volume of the pressure tank is 1 1 and the volume of the expansion tank 30 1 The pressure tank is provided with a feed pipe for ammonia, optionally with the interposition of a pressure-increasing device To ensure a further increase m pressure, in addition a feed pipe for inert gases, e g nitrogen, may be provided The process can be carried out in a continuous manner, using a tubular or cylinder shaped, pressure-resistant reactor, with which the bringing into contact of the SWORN TRANSLATOR GER FRE SPA OUT, cellulose and liquid ammonia takes place m the cylinder of the reactor and the impregnated material is transported through the reactor with the aid of a conveyor screw in the form of a wad and is discharged intermittently through a valve or a suitable system of pressure locks into a collecting chamber Suitable components, which the expert can easily adapt for carrying out the process accoiding to the invention, are described in the EP-A-329 173 and the US-4 211 163 lespectively The cellulose should have a low moisture content, preferably less than 9% by mass, in particular less than 7% by mass Preferably it is chemically pure, i e preferably it contains less than approximately 12, in particular less than approximately 8% by mass of foreign substances The contact time between the liquid ammonia and the cellulose is not critical As an expedient minimum contact time approximately 4 minutes can be indicated, as a rule it amounts to approximately 8 minutes An activated cellulose produced by ammonia e> plosion has a special X-ray diffraction spectrum with peaks at the following diffraction angles 2 0 and with the relative intensities Peak 11.25 + 1 of the relative intensity of approximately 15 to 25, Peak 17+1 of the relative intensity of approximately 25 to 40 and Peak 20,5 + 1 of the relative intensity 100 (reference value) This cellulose modification is also called cellulose III* It was found that during the treatment of this cellulose modification with 4 to 12% by mass soda lye, a mixture of cellulose II and amorphous cellulose is obtained, wherein the portion of the amorphous cellulose increases with the concentration of the used soda lye During the conventional mercerisation, i e the treatment of native cellulose with 18 to 20% by mass soda lye, from the cellulose I first alkali cellulose and from this cellulose II, but never amorphous cellulose, is obtained During the treatment SHORN TRANSLATOR GER FRE SPA DUT. of cellulose III* with soda lye of a concentration of less than 4% by mass, in particular less than 2% by mass, probably an addition compound of cellulose III* and NaOH is formed The following explanations are given with special reference to the ammonia explosion and aqueous soda lye, but apply correspondingly to other activation processes, alkalis and solvents For the treatment with aqueous soda lye, the residual ammonia content of the cellulose after the NH^-explosion is not critical After the NH^-explosion the ammonia-activated cellulose is brought into contact with diluted soda lye in a suitable manner To this end, the cellulose can be fed into a solution of the lye in water or can be sprayed with the solution, or the solution can be passed through the cellulose m counter-current All technological embodiments of the bringing into contact of a solid substance with a liquid component, which lead to a thorough mixing or penetration, are conceivable and possible heie The high accessibility of the NH^-exploded cellulose as well as its high specific surface (low density) permit the quick diffusion of the NaOH-solution into the inside of the cellulose, resulting in a homogeneous distribution of the NaOH through the entire cellulose The NH^exploded cellulose is included by the diluted NaOH-solution In doing so the NaOH-molecules displace the M-h-molecules that are still piesent, forming the known polar structure with the cellulosic OH-groups, since due to the higher basicity of the NaOH the ammonia is expelled from the cellulose Accordingly there exists the following "task distribution" the ammonia explosion produces a high accessibility of the cellulose, and the NaOH forms dipoles with the cellulosic OH-groups SWORN TRANSLATOR GER FRE SPA nIIT ]() The advantages of the splitting up of the activation or the increase in the accessibility on the one side and of the formation of alkali cellulose on the other side, are obvious The activation, preferably by ammonia explosion, constitutes an essential prerequisite for the production of stoichiometric alkali cellulose The advantages of the formation of stoichiometric alkali cellulose and of the cellulose derivatives produced from same can be summarised as follows In contrast to the conventional mercerisation or alkalisation, less or no adhenng, 1 e excess lye occurs Accordingly, the process step of pressing out the lye can optionally be dispensed with The consumption of NaOH can, therefore, be drastically reduced (up to 75%) Closely associated therewith aie a lower consumption of reagents, an increased yield and a lowei salt and by-product formation The reactions, although still carried out heterogeneously, approach a homogeneous pattern As a result, also a higher product quality and performance is obtained for the end products, which can be attributed to a more homogeneous substituent distribution This in turn is the result of a homogeneous distribution of the cellulose-oxonium-NaOH-complexes In the following the advantages will be explained with reference to the production of viscose For the ammonia explosion the cellulose need only be pre-comnunuted relatively coarsely (torn up) As a result of the NH-,-explosion the cellulose is then to a far reaching extent separated into fibres, so that a further mechanical comminuting (shredding) can be dispensed with, which means a considerable saving of energy When using cellulose with a polymerisation degree close to that which is to be obtained for the end product, also the so-called ripeness is not required With regard to the production of viscose this is a relatively tricky process step, since SHORN TRANSLATOR GER FRE SPA DUT, II during same the risk of a drying out of the cellulose crumbs exists, which inevitably results in mhomogeneous reactivities During the production of xanthogenate by the process according to the invention, the for example ammonia-exploded cellulose is fed into 5-6% NaOH, the lye ratio being chosen in such a way that after the complete dissolving an 8-9% viscose is obtained This corresponds to the cellulose xanthogenate concentration customary during spinning The formation of the xanthogenate takes plays whilst stirring or shearing and slowly adding CS2, when during the course of the reaction increasingly larger portions of cellulose are dissolved The monitoring of the dissolving process by suitable technical means (optical sensors, viscosity, torque etc) permits the use of only as much carbon disulphide as is required The reaction takes place more quickly than with the conventional process As a result, with existing plants an up to 30% higher production capacity can be obtained Alternatively, the for example ammonia-exploded cellulose can be brought into contact with only 1-2% NaOH, after which carbon disulphide is added and parallel to the adding of the carbon disulphide or after completing the adding of the carbon disulphide, the spinning concentration of the viscose can be adjusted with concentrated NaOH In the following examples all percentage data are % by mass, unless otherwise indicated Example 1: Production of ammonia-exploded cellulose 200 g commercial cellulose (Cuoxam - DP 480) with an a-cellulose content of approximately 96%, m sheet form (water content approximately 8%) was cut lip into approximately 1 3 x 1 3 cm pieces and put into an autoclave of 1 1 with a double wall for steam heating Subsequently 400 g liquid ammonia were pressed into the autoclave through a valve The mass ratio ammonia/cellulose was 2 1 By the steam heating of the autoclave the temperature was increased to 60°C This resulted in a pressure inside the autoclave of approximately 20 bar The reaction AW JjVstjito* OER FPF CPA nn T mixture was kept under these conditions for 60 s Subsequently, by opening the valve (inside diameter 4 cm), the mixture was suddenly and completely released into an explosion tank with a volume of 30 1 An optimum defibrillation took place The ammonia content of the product occurring m the explosion chamber amounted to approximately 1 % by mass, related to the defibnllated cellulose Example 2: Production of benzvl cellulose This NH.^-activated cellulose with a residual ammonia content of 3% is dispersed in soda lye (400 ml to 10 g cellulose) This suspension is kept for 1 hour at 20-25°C The modified cellulose is washed with ethanol after the aqueous soda lye has first been drawn off The content of remaining NaOH was 2 5% (related to the cellulose) The washed cellulose is fed into a N-methyl-pynohdone (NMP), which contains 3 9% benzyl-trimethyl ammonium chloride The suspension is placed under a slight vacuum (20 mbar) at 40°C so as to completely remove the ethanol Subsequently, under normal pressure, whilst stirring vigorously, a solution of benzyl chloride in NMP is added, the molar ratio benzyl chloride/AHG amounting to 2 1 After a reaction time of 1 hour at 40°C, the obtained benzyl cellulose is filtered off and washed with water until a pH \alue of close on 7 is obtained in the washing water Subsequently, the benzyl cellulose is dried at a temperature of 80°C under a vacuum of 1 mm Hg The substitution degree according to infrared spectroscopy was 0 15 Example 3: Production of benzoyl cellulose 10 g ammonia-exploded cellulose with a residual ammonia content of 7 7% is mixed into 120 ml of a 1% aqueous NaOH-solution for 1 hour at 20-25°C After drawing off the soda lye (residual soda lye 2 4%, related to cellulose), the cellulose is mixed with 200 ml N-methyl pyrrohdone and then left to stand foi 12 hours to permit an exchange of the NMP by water Subsequently, the cellulose is largely freed from the water containing NMP by pressing out and is then taken up in pure NMP After cooling to 15°C, 3 3% b\ mass benzyl trimethyl ammonium SWORN TRANSLATOR GER FRE SPA DUT, chloride, related to the cellulose, is added Subsequently so much benzoyl cliloiide, dissolved in NMP, is added that the molar ratio to the cellulose amounts to 1 1 The reaction mixture is heated for 3 houis to 50°C, then cooled again and left to stand for 12 hours The obtained benzoyl cellulose is filtered off and washed with water and then with alcohol Subsequently a drying takes place under vacuum at 80°C Example 4: Production of cvano-ethvl cellulose NTh-activated cellulose with a residual ammonia content of 3% is dispersed in an aqueous 0 5% soda lye This mixture is kept for 1 hour at 5°C, then stirred for 15-30 minutes Then acrylonitrile is added in a quantity so as to obtain a molar ratio acrylomtrile/AHG of 2 1 After stirring, the reaction mixture is kept for 1 5 to 3 hours at 45°C, then for approximately 2 hours at 0°C The mixture is neutralised with acetic acid The cyano-ethyl cellulose is filtered off and washed with water, then with alcohol Subsequently the cyano-ethyl cellulose is dried at 80°C under vacuum The obtained cyano-ethyl cellulose has a substitution degree of 0 28 Example 5: Production of hvdrow-ethvl cellulose 60 g cellulose (type Modo, DP (Cuoxan) ~ 570) after the ammonium explosion are taken up in 750 ml 2% NaOH and degassed in the rotation evaporator for 30 minutes at a temperature of 25°C under a vacuum of 40 mbar Then the swollen cellulose is pressed to approximately 150 g, mixed with 400 g tert-butanol in a 2 1 round flask on the rotation evaporator and evacuated to approximately 50 mbar Subsequently 9 g gaseous ethylene oxide are added at 25°C within 30 minutes, during which the pressure does not exceed 600 mbar After 1 h the pressure drops to approximately 220 mbar A pressure compensation with respect to atmospheric pressure is carried out with nitrogen, followed by heating to 60°C and stirring for 1 hour After cooling to 20°C, the reaction mixture is neutralised with acetic acid The reaction mixture is poured into 2 1 acetone, filtered off and washed with an acetone/water solution (90%/10%) After drying in the vacuum drying cabinet at SWORN TRANSLATOR HER cRE SPA du1. </div>

Claims

<div class="application article clearfix printTableText" id="claims"> 14 90°C/10 mbar up lo constant mass, 63 g ofhydroxy-ethyl cellulose (DS -0 4) are obtained The product is completely soluble in water Example 6: Production of hvdrow-ethvl cellulose 20 g cellulose (type Modo, DP (Cuoxan) ~ 570) after the ammonium explosion are taken up m 120 ml 2% NaOH and degassed in the rotation evaporator for 30 minutes at a temperature of 25(,C under a vacuum of 40 mbai Then the swollen cellulose is pressed to approximately 60 g, mixed thoroughly with 140 g tert-butanol in a 1 1 stirring autoclave and scavenged with nitrogen Subsequently 18 g ethylene oxide are added at 25°C, heated within 30 minutes to 60"C and stirred foi 1 hour After cooling the autoclave to 20°C the reaction mixtuie is neutialised with acetic acid The reaction mixture is poured into 500 ml of a tert-butanol/water solution (80%/20%), filtered off and washed with tert-butanol/water (80%/20%) After drying in the vacuum drying cabinet at 90°C/10 mbar up to constant mass, 28 g of hydroxy-ethyl cellulose (DS ~ 2 6) aie obtained The product is completely soluble in water Example 7: Viscosing 20 g cellulose (type Viscokraft LV 4, DP (Cuoxan) ~ 400) after the ammonium explosion are taken up in 120 ml 4% NaOH and degassed in the rotation evaporator in a 1 1 round flask for 30 minutes at a temperature of 25°C under vacuum (40 mbar) Subsequently 5 g carbon disulphide are metered into the rotating flask at 25-30°C within 5 minutes, during which the pressure increases to approximately 500 mbar After 2 h the pressure drops to approximately 180 mbar Then the flask is cooled by means of an ice bath After cooling to below 10°C, 80 ml of 8% NaOH are added and stirred for 12 h until a light yellow, clear viscose solution is obtained * * * SWORN TRANSLATOR GER FRE SPA OUT. ^ / i 5V 15 Patent claims A piocess for pioducmg a cellulose derivative, with which a) cellulose is impregnated with an alkali solution, b) the impregnated cellulose is optionally pressed and c) the cellulose is subjected to a substitution 01 addition reaction, wherein a cellulose derivative with a substitution degree DS is obtained, wherein the cellulose used is an ammonia-activated cellulose and the molar ratio of alkali to AHG (anhydroglucose unit) in the cellulose at the beginning of step c) does not exceed 2 times the DS A process according to claim 1, wherein the alkali solution has a concentiation ot approximately 12% by mass or less A process according to claim 1, wherein the alkali solution has a concentration of less than approximately 10% by mass A process according to any one of claims 1 to 3, wherein the molar ratio of alkali to AHG in the cellulose at the beginning of step c) does not exceed 1,5 times the DS A process according to any one of claims 1 to 4, wherein a sub-stoichiometnc ratio of alkali to AHG is maintained in the cellulose A process according to any one of the preceding claims, wherein the ammonia-activated cellulose is obtained by a process with which the cellulose is brought into contact with liquid ammonia at a starting pressure which is higher than V' I' _ 16 atmosphenc piessure and at a temperature of at least approximately 25°C, wherein the quantity of the liquid ammonia suffices at least to wet the surface of the cellulose, and that the volume available to the cellulose/liquid ammonia system is increased in an explosion-like mannei whilst reducing the pressure by at least 5 bai 7 A piocess according to any one of the pieceding claims, wherein the alkali solution is aqueous or alcoholn soda lye oi potassium lye 8 A piocess accoidmg to any one of the preceding claims, wherein the substitution oi addition is bi ought about by reaction with carbon disulphide, acyl-group tiansfemng reagents, alkyl-gioup tiansleiring leagents, alkene oxides, a-halocaibo\ylic acids oi then salts, a,(i-unsatuiated caibonyl compounds or aciylonitrile 9 A process accoidmg to any one of the pieceding claims, wheiein the cellulose, after impregnation with alkali solution and pnor to the substitution oi addition reaction, is not subjected to a pressing step 10 A piocess for producing a cellulose denvative as claimed in claim 1 substantially as heiein described with lefeience to any one of Examples 2 to 7 11 A cellulose derivative when obtained by the process of claim 1 END OF CLAIMS </div>