Title of Invention

AN IMPROVED PROCESS FOR MAKING CELLULOSE FIBRES, FILAMENTS OR FILMS

Abstract

ABSTRACT "AN IMPROVED PROCESS FOR MAKING CELLULOSE FIBRES FILAMENTS OR FILMS" AN improved process for making celhilose fibres, filaments or films which comprises the in the steps of: i) activating celhilose in a mixture of containing 7-28% cellulose, 65-80% tertiary amine oxide and 5-15% water for a period sufficient to allow a swelling of the celhilose by water present in said mixture, the temperature of said activation step and concentration of solvent being such that the solvent ia not converted into its monohydrate state during step of activation; ii) the cellulose-am me oxide mixture being subjected to the step of heating for removal of water to convert the solvent into at least its monohydrate form to cause a dissolution of the cellulose in the solvent; iii) extruding the cellulose as fibres, filaments or films using dry jet-wet spinning method which is stretched in air gap of 5-1000 mm to develop molecular orientation, iv) regenerating the spun filaments in an aqueous spin bath containing 1-40% NMMO at a temperature of 5-60°C and the shaped articles are washed free of am me oxide, bleached, finished and dried.

Full Text

FORM-2 THE PATENTS ACT, 19 7 0 (39 of 1970) PROVISIONAL / COMPLETE SPECIFICATION SECTION10,rule 13) TITLE AN IMPROVED PROCESS FOR MAKING CELLULOSE FIBRES, FILAMENTS OR FILMS. APPLICANT BIRLA RESEARCH INSTITUTE FOR APPLIED SCIENCES, BIRLAGRAM 456 331, NAGDA, MADHYA PRADESH, AN INDIAN INSTITUTE. 12 Feb 2002 The following specification particularly describes the nature of the invention and the manner in which it is to be performed The present invention relates to an improved process for making cellulose fibres, filaments or films. The process to dissolve cellulose in tertiary amine OXide was disclosed in 139 by Graenacher et al in US Pat.No.279181. In accordance with the disclosure, the N-Oxide of trialkyl amine or alkyl cyeloaliphatic tertiary amine having 14 carbon atoms or less are suitable for- cellulose solvent, The drawback of the process is that the solution has low cellulose content and high viscosity„ Another process to dissolve cellulose and other similar compound in tertiary amine-oxide is disclosed in US Pat,, Nos,3447956 & 3447939 by Johnson et al in 1.969, where a cyclic mono amine-N-Oxide) compound such as N-Metbyi morpboline—N-0xide CNMMO), N-Methyl Pyrolidine N-Oxide etc. are used as solvent. This method is used to strengthen the paper or fabric strength,, In another disclosure by C C McCorsiey III et al, in US Pat. No.4142913, a process is provided to make a solid precursor of a solution of cellulose in tertiary amine oxide„ The product may be comminuted to form chips which are further fed into an extruder for shaping it into a cellulosic article. The main disadvantage of this process is that the solid precursor of Cellulose & Amine oxide is highly hygroscopic and if too much water is absorbed, the phases separates Another serious disadvantage associated with this process is that the remelting of chips for extrusion causes An object of this invention is to propose an improved process for preparation of a cellulose solution for spinning of fibres, filaments or films therefron. Another object of the present invention is to provide a suitable method to dissolve cellulose in the tertiary amine oxide solution, which can directly be fed into extruder without associated the aforesaid problem. Another object of the invention is to provide a process which can make a cellulose-amirae thermoplastic polymer having high percentage of cellulose from 7% to 28% and preferably 12%-22%. Therefore, still another object of the present invention is to provide a simple and effective dissolution system by activating cellulose before it is dissolved in amine oxide solution. A more specific object of the invention is to provide a process to prepare cellulose solution in amine oxide solvent which has higher cellulose content by adopting the online activation system. A further object of the invention is to provide an improved process for making spinnable solution of cellulose and amine oxide having higher cellulose concentration and better uniformity than those described in prior arts. A still further object of the invention is to provide a process to make a mesomorphous solution of cellulose having liquid crystal in the solution itself. Another object of the invention is to provide a process for making cellulosic articles from cellulose amine-oxide solution which does not pollute the environment with waste product/metal ions/sulphur compounds etc. as in case off viscose process. Yet another object of this invention is to provide a simple and online method to activate the cellulose ta increase its swelling and dissolution power in aqueous amine oxide solution. According to this invention, there is provided an improved process for the preparation of a cellulose solution for spinning of fibres, filaments or films therefrom which comprises the steps of : i) activating cellulose in a mixture containing said cellulose, tertiary amine oxide solvent and water for a period sufficient to allow a swelling of the cellulose by introduction therein of water present in said mixtures, the temperature of said activation step and concentration of solvent being such that the solvent is not converted into its monohydrate state during the step of activation and ii) the cellulose mixture being subjected to the steps of dissolution of cellulose in the solvent by heating for removal of water so as to convert the solvent into at least its monohydrate form so as to cause a dissolution. Further, in accordance with this invention, there is provided an improved process for making cellulose fibres, filaments or films comprising the steps of : i) activating cellulose in a mixture containing said cellulose, tertiary amine oxide solvent and water for a period sufficient to allow a swelling of the cellulose by introduction therein of water present in said mixture, the temperature of said activation step and concentration of solvent being such that the solvent is not converted into its monohydrate state during the step of activation; ii) the cellulose mixture being subjected to the steps of dissolution of cellulose in the solvent by heating for removal of water so as to convert the solvent into at least its monohydrate form so as to cause a dissolution; iii) the cellulose-Amine oxide solution containing 7-28% cell, 65-80% NMMO and 5-15% water; iv) extrudling the cellulose solution as fibres, filaments or films using dry jet-wet spinning method which is stretched in air gap of 5-1000 mm to develop molecular orientation; v) regenerating the spun filaments in an aqueous spin bath containing 1-40% NMMO at temperature of 5-60 deg.C. The shaped articles are washed free of amine oxide, bleached, finished and dried. The method used in the present invention is simple and activation takes place within the premixer or dissolving vessel. In accordance with a preferred embodiment and to facilitate dissolution of cellulose in amine oxide solution, we found that when cellulose is mixed with aqueous solution of 40-70% amine oxide containing little activator, it enhances the cellulose activation at temperature of 70-115 deg.C. It is known that the polar media like water is used for swelling the cellulose. The swelling of cellulose enhanced at temperature above 70 deg.C in presence of amine oxide-water mixture. The activation of cellulose completes if, at this temperature the mass is kept for 20-60 min. The cellulose dissolution is fast and good homogenous cellulose solution is made with the treated cellulose. The solution of the present invention can directly be fed to Spinning Section without converting them into solid chips or granules. The homogenity of any polymer melt or solution is the key base of smooth spinning performance and final product properties. Therefore, for this invention, cellulose is activated in premixer and then the cellulose solution is made in a special mixtruder system with a facility of mixing, needing and extruding. All these operations are carried out in an aparatus which has provision of heating and evacuation. The sheet form or powder form or grounded form of cellulosic pulp (wood pulp or cotton linter) is mixed with aqueous amine-oxide solution at temperature above 70 deg.C containing small amount of activator to activate the cellulose in the premixer and fed to the mixtruder continuously. ■A The spinnable solution has a mesomorphous phase which contains cellulose above 20% in cell/amine-oxide/H20 system. Such solution has excellent spinning properties and the fibres have very high tenacity and good elongation. The solution containing cellulose above 20% preferably 25% shows anistropic properties and this gives fibres with high degree of crystalline orientation. In accordance with this invention, cellulose is mixed with aqueous amine-oxide solution in required proportion under condition of temperature and pressure where no dissolution of cellulose takes place and only the cellulose absorbs the amine oxide uniformly. The resulting mixture is allowed to remain for sometime to activate the cellulose in presence or absence of some activator which allows the interaction of amine-oxide in cellulose fibre matrix. This results into greater swelling of cellulose. The cellulose amine-oxide mass is then sent to reactor (Mixtruder), where excess of water is removed under reduced pressure from the amine-oxide saturated cellulose at a temperature where no significant degradation of cellulose takes place and to form an extrudable/spinnable solution of cellulose. To further increase the homogenity of solution, it is passed through a counter rotary type homogenizer. The dope is filtered and sent to Spinning Section. The metered solution is passed through a Spinnerette and spun into fibre/filaments by dry jet-wet spinning method. In the present invention, the cellulosic raw Material is any rayon grade pulp or cotton linter and amine oxide is a cyclic tertiary amine oxide preferably N-methyl morpholine N-Oxide (NMMO). Other suitable amine oxides may also be used with some changes in process parameters. The premixing of cellulose with amine oxide and activation are carried out at temperature 70-115 deg.C. preferably 80-90 deg.G. for a period of 20-60 min.preferably 30-40 min. The concentration of amine-oxide solution is around 40 to 70% preferably 50-65%. The activation of cellulose in aqueous amine-oxide is based on the principle of intra crystalline swelling. The water present in amine-oxide solution serves as a Swelling agent. The swelling phenomenon is enhanced in presence of activatdr of non-ionic mature. During the development of this invention, we studied wetting* cum penetrating agents, such as the compounds of Glycols and Glymes families. These are found quite compatible with the present system. In presence of above compounds in a concentration of 0-3% by weight of cellulose the absorption capacity of. aqueous' 50% NMMO solution in pulp was studied. The results are shown in Table 1. TABLE - 1 ABSORPTION OF 50% NMMO SOLUTION IN PULP IN PRESENCE OF DIFFERENT NON-IONIC AGENTS the polyethylene glycol (M.Wt. 400-4000) and poiygiymes (specially the PAGE) increase the rate of cellulose swelling and rate of dissolution. In searching suitable additives for getting homogenous dope, we studied the effect of some inorganic additives and we found that small amount of ammonium chloride enhances the dissolution rate & also reduces the melt viscosity. Some of our findings are reported in Table-2. The reaction time & temperature were kept constant in all cases. When carrying out such process on a large scale, it. is utmost important to operate under adequate control and safety conditions since the polymer has property to degrade very fast at elevated temperature and there is always a risk of fire if temperature of the cellulose amine oxide solution exceeds 140 deg.C. In batch preparation, when large volume of cellulose amine oxide is to be handled, it is difficult to control the temperature and the rate of evaporation. In addition to this, due to very high viscosity of the cellulose - amine oxide solution, lot of dope retained in the dissolving vessel and thereby requires to clean the vessel before taking 2nd batch which further causes a great loss of spinnable material and thus reducing the economy of the process. Therefore, the further object of the invention is to provide a continuous method for producing cellulose solution and then continuously feeding the solution to spinning section to produce shaped articles like fibre, filaments or films. In accordance with the invention, this object is achieved by using a continuous processor of single or double arm mixing cum needing and extruding device in which a slurry of cellulose and amine-oxide and H20 is supplied from a premixer-cum-activator zone and the final melt of cellulose-amine oxide is discharged from the homogenizer continuously. Thus, feeding of cellulose slurry and drawing of homogenous mass of cellulose solution is carried out continuously. To avoid the degradation of cellulose during the dissolution at elevated temperature, antioxidants are used in small quantity. The preferred antioxidant is propyl gallate. A preferred process in accordance to the present invention is carried out as described below : A cellulosic pulp (wood pulp or cotton linter) vnth degree of polymerization above 800 & preferably 900-1400 is used. Referring to Fig. 1 & 2, the slurry is made with 40-70% aqueous NMMO solution in premixer (1) where pulp is also activated with the use of some activators like glycols or glymes at temperature betwen 70-115°C& preferably 80-90 deg.C Antioxidant & Melt viscosity reducing additives are also added in the premixer. The properly activated cellulose slurry is continuously fed to the processor/reactor (Z) under reduced pressure at elevated temperature. The temperature range, in the Processor is usually 70-120 deg.C. &. preferably 80-105 deg.C. The composition of feed slurry is adjusted as per requirement of final dope composition. In the reactor the water is removed continuously through Condenser (3) and when the water level reaches equivalent to that of monohydrade of NMMO, the cellulose gets dissolved. With the method of present invention, cellulose solution containing 7-28% cellulose can be made. The prefered concentration of cellulose is 12-22%. The amine oxide in the solution is in the range of 65-80% & preferably 70-78%. The water content is 5-15% and preferably 6-12%. The completeness of the dissolution is checked by moni¬toring the refractive index of the solution. When the refractive index reaches to a level of 1.490, it can be v said that the cellulose has completely been dissolved. The dissolution completes within 40-150 min. The dis¬solved mass is further made homogeneous by passing through a homogenizer system-(4). The discharge from the homogenizer, is fed into filter-(5) & passed through static mixer (6) and pumped by (7) to a metering pump (8) of spinning system. The metered amount of dope is passed through spin pack(9) and extruded through spin-nerettes-(lO) having 50-250 micron hole dia using dry jet-wet spinning technique. The air gap (11) betwen the jet surface and spin bath is usually from 5 mm to 1000 mm & preferably 50 mm to 250 mm. The spin bath (12) comprises of aqueous NMMO solution containing 1-40% NMMO preferably 5-25% and temperature 5-60 deg.C preferably 20-30- deg.C. The take up speed of the filaments (13) are 30-400 m/min & preferably 50-150 m/min. The filaments are further washed to remove NMMO solution from the tow by a countercurrent washing method & then bleached, finished & dried. To impart crimp, the tow is passed (not shown in fig.) through a stuffer box & then cut into staple./The used spin bath is collected in tank-(14) which is filtered through (15) & purified (16) spin bath is collected on top tank (17). The fibre properties of the invention have been tested & listed in va.r i ous examp1es . The stream-(18) of excess spent spin bath is sent to recovery section, where it is filtered at (19) & excess of water is removed in distillation column-(20). Further, it is purified by ion exchange resin (21) and pure NMMO solution of 40—60% is obtained at (22), which is circulated in the process. The invention will further explain in even more detail way by means of following examples which are given for illustration and are not to be taken as, in any way, limiting the invent lass. Example - 1. A cellulose solution is prepared by mixing 345 gm of ketchikan K-120 pulp containing 7% water in 5000g of 50% NMM/water solution. The pulp and NMMO/H20 mixture is fed in the premixer and mixing is carried out for 60 min at 80°C. 0.2% propyl gallate (antioxidant) and 0.5% PEG 400 on the basis of cellulose weight are also added. During this period, the pulp absorbs the water present in aqueous NMMO solution and gets activated which facilitates the penetration of NMMO in the interior of fibre matrics. The slurry is then fed into reactor under vacuum where temperature is maintained to 90°C. The water is removed through condensor, and 2140g of water is allowed to remove. At this stage, the complete dissolution of cellulose takes place and it shows the refractive index of 1.490. The melt (i.e. cell/NMM0/H20 solution) so obtained has 10% cellulose, 12% water and 78% NMMO. This solution is passed through homogenizes, filtered and sent to spinning machine through static mixer. The metered amount of solution is passed, through a spinnerettes having 13 holes and 200 micron hole diameter with L/D ratio 1:1. The filaments are allowed to travel in the air for a distance of 15 cm and then passed through a spin both containing 5% aqueous NMMO at 20°C. The filaments are taken on godet at 60 m/min speed and washed counter currently by water to remove the amine-oxide completely. It is further bleached, finished dried and passed through a stuffer box to impart crimps and then cut into staples. The fibre properties are shown in Table - 3. Table - 3. Example 2 to 5. The cellulose solution is prepared as described in example -1 except that the different activators are used in the premixer during mixing to enhance the activation of cellulose. The polymer (cellulose solution) characteristics are reported in Table - 4. Example 6 to 8. Cellulose solution is made by activating the K-120 pulp with PEG 4000 (0.5%) on cell for 30 rain in premixer and then fed into the reactor where excess of water is removed. The dissolution is completed in 85 min at 85 deg.C. The solution of different cellulose concentrations are made. The quantities of pulp and NMM0 taken and water to be removed, are shewn in Table 6. The solution so obtained is spun in a single screw extruder using spinnerette of 200 micron hole dia by dry. jet-wet spinning method. Air gap is kept 15 cm and spin bath composition is 5% Aqueous NMM0 at 20 deg.C with spinning speed of 75 m/min. The fibres arewashed, bleached finished and dried. The results are shown in Table 6. TABLE -6. POLYMER COMPOSITION AND FIBRE PROPERTIES. Example 9 & 10. Cellulose solution is prepared as described in Example 6. The cellulose is activated in premixer at 80 deg.C. for 30 min. using PEG AOOO (0.3 % on cell basis) in both the examples. In example 10, we have used 0.5% Ammonium-Chloride (on cell) in the premixer to facilitate dissolution and to reduce melt viscosity. The solution is spun as described in' example 1 and the results are reported in Table-7. TABLE - 7 Polymer Characteristics and Fibre Properties. WE CLAIM: 1. An improved process for making cellulose fibres, filaments or films which comprises the in the steps of; i) activating cellulose in a mixture of containing 7-28% celhilose,65-80% tertiary amine oxide and 5-15% water for a period sufficient to allow a swelling of the cellulose by water present in said mixture, the temperature of said activation step and concentration of solvent being such that the solvent is not converted into its monohydrate state during step of activation; ii) the cellulose-am ine oxide mixture being subjected io the step of heating for removal of water to convert the solvent into at least its monohydrate form to cause a dissolution of the cellulose in the solvent; Hi) extruding the cellulose as fibres, filaments or films using dry jet-wet spinning method which is stretched in air gap of 5-1000 mm to develop molecular orientation. iv) regenerating the spun filaments in an aqueous spin bath containing 1-40% NMMO at a temperature of 5-60sC and the shaped articles are washed free of amine oxide, bleached, finished and dried. 2. A process as claimed in claim 1 wherein the cellulose-amine oxide solution is passed through a homogenizer to improve homogenity of the dope; 3. A process as claimed in claim 1 in which the cellulose sohition is extruded through spinnerettes and passed through an air travel and then into an aqueous amine-oxide sohition to regenerate the fibres or filaments from which the solvent is recovered, purified and recycled. 4. A process as claimed in claim 1 wherein an activator is optiontly added to said mixture, said activator selected from inorganic additives, Glycols and Glymes. 5. A process as claimed in claim 1 wherem said amine oxide is a cyclic tertiary amine oxide, preferably N-methyl Morpholine N- Oxide (NMMO). 6. A process as claimed in claim 1 wherem said cellulose is selected from rayon pulp and cotton lister pulp. 7. A process as claimed in claim 1 wherem said solvent used to form the mixture contains 40-70% NMMO in water, preferably 50 to 65%. 8. A process as claimed in claim 1 wherein the step of activation is preferably carried out for a period of 20-60 minutes, preferably for 30-40 minutes. 9. A process as claimed in claim 1 wherein the temperature of said activation step is maintained in the range of 70-115 C and preferably at 80-90 C. 10. A process as claimed in claim 1 wherein the step of dissohition comprises on heating the activated mixture at a temperature of 70-120oC and preferably at 80-105 C. 11. A process as claimed in claim 1 wherein the step of dissohition of the activated mixture is carried out by heating under reduced pressure. 12. A process as claimed in claim 1 wherein the step of dissolution is carried out for 40-150 minutes. 13. A process as claimed in claim 4 wherein said activator is present in an amount of upto 3% by weight of the cellulose. 14. A process as claimed in claim 1 wherein an inorganic additive selected from ammonium chloride, calcium chloride, alkalies, glymes and glycols is added to the mixture for the step of activation. IS.An improved process for making cellulose fibres, filaments or films substantially as herein described. Dated this 12* day of FEBRUARY, 2002.

Documents:

127-mum-2002-abstract(04-04-2005).doc

127-mum-2002-abstract(04-04-2005).pdf

127-mum-2002-cancelled pages(04-04-2005).pdf

127-mum-2002-claims(granted)-(04-04-2005).doc

127-mum-2002-claims(granted)-(04-04-2005).pdf

127-mum-2002-correspondence(09-09-2007).pdf

127-mum-2002-correspondence(ipo)-(16-05-2007).pdf

127-mum-2002-form 1(09-04-2002).pdf

127-mum-2002-form 1(12-02-2002).pdf

127-mum-2002-form 19(25-03-2004).pdf

127-mum-2002-form 2(granted)-(04-04-2005).doc

127-mum-2002-form 2(granted)-(04-04-2005).pdf

127-mum-2002-form 3(12-02-2002).pdf

127-mum-2002-power of attorney(12-02-2002).pdf