Title of Invention

"METHOD OF DEGUMMING OF DECORTICATED RAMIE FIBRE BY RECYCLING OF DEGUMMING LIQUOR"

Abstract

This is a method for degumming decorticated plant bast fiber, such as ramie, flax, or hemp bast fiber, to remove pectin-containing material and coloring gums therefrom-. The decorticated plant bast fiber is desirably washed with a washing solution containing a surface active agent to penetrate the plant bast , fiber and remove water soluble material and other debris therefrom. The washed plant bast fiber is then rinsed. The washed and rinsed plant bast fiber is treated with an aqueous acidic treatment solution of fungal pectinase for a period of time of between 10 and 30 minutes to remove the 'pectiri from the plant fiber. The acidic treatment solution is maintained at an elevated temperature in the range of between 60.degree. C. and 7O.degree. C. and has a pH between about 2;0 and 3.5. Thereafter, the plant bast fiber with the pectin removed therefrom, is removed from the acidic treatment solution and a sufficient ; amount of NaOH is added thereto to increase the pH of the treatment solution to about 11.0. The plant bast fiber with the pectin removed therefrom is then further treated in the basic solution for a period of time between about 15 to 60 minutes to remove the coloring gum adhering to the plant bast fiber. The plant bast fiber with both the pectin and the coloring gum removed therefrom is then rinsed to remove the treating solution therefrom.

Full Text

This invention relates to the chemical method of degumming decorticated ramie (Boehmeria nivea Gaud), obtained by decortication of the stems of ramie plant followed by washing and drying into ramie fibre of 20 to 30% gum content, to fibre of different residual gum contents (generally 2% to 8%) suitable for making textile structures and speciality papers, comprising the treatment of decorticated ramie in aqueous alkaline medium containing 0.5% to 2.5% sodium hydroxide, depending on the gum content of the decorticated fibre, an anionic wetting agent in 0.1 to 1.0 per cent by weight on sodium hydroxide in the bath, and sodium sulphite in 0.25 to 1.25 per cent by weight based on sodium hydroxide, maintaining a liquor ratio between 1:5 to 1:8 in the range of temperature between 80°C and 125°C under pressure for a period between one hour and three hours to remove pectin and gum from the decorticated fibre, followed by recycling or reuse of the hot degumming liquor from the first degumming operation for further degumming of fresh decorticated ramie up to four to six cycles of operation, replenishing the necessary chemicals and water in the degumming liquor to maintain the concentration of alkali and liquor ratio before each cycle of operation. Background and Prior Art: Ramie fibre is obtained from the stem of the plant Boehmeria nivea by decortication and washing. Decorticated ramie fibre usually contains 20% to 30% of an encrusting material known as gum1. Removal of a substantial portion of this gum is necessary for industrial application of the fibre as presence of gum makes the fibre vulnerable to microbial attack. It has also been observed that with progressive removal of gum from decorticated ramie, its fineness, tensile strength and extensibility improves significantly. It has been reported3 that for textile application the decorticated ramie should be degummed to a gum content level below 6%. Therefore, proper degumming of decorticated ramie fibre is necessary for realizing its intrinsic fibre properties and industrial application. Various chemical, microbiological and chemi-microbial methods have been reported for the degumming or removal of gum and pectin containing substances from plant bast fibres. For example, U.S. Patent No. 2,725,289 discloses a process for the chemical retting of ramie, flax, hemp, jute etc. in which the fibrous material is treated with an aqueous solution of alkali base containing palmitate of an amine base as emulsifier, then repeated the treatment with the aqueous solution of the same substances containing additionally an oxidising agent. U.S. Patent No. 1,941,793 discloses a method in which the fibres are treated successively in an alkaline bath and an enzyme bath. Alkali acts to open the cortex of ligneous material to make accessible to the enzymes. Degradation of cellulose fibres in alkaline bath is checked by addition of a buffer. U.S. Patent No. 1,746,316 describes a process for retting of flax, jute and ramie by adding a nitrogen fixing bacteria to the retting process to degum the gum or pectin from the fibre. U S Patent No. 4,617,383 discloses a method for degumming and bleaching decorticated plant bast fibre. In this method, the decorticated plant bast fibre such as ramie, flax or hemp is desirably washed with a solution of a surface active agent, rinsed and then treated with aqueous acidic treatment solution of fungal pectinase for a period of time between 10 and 30 minutes to remove pectin therefrom. The acidic treatment solution is maintained in the range between 60°C and 70°C and has a pH between 2.0 and 3.5. The plant bast fibre with pectin removed therefrom is treated with an aquous basic solution of sodium hydroxide having pH about 11.0 for a period of time between about 15 to 60 minutes to remove the colouring gum. Luniak4 reported a degumming method in which ramie fibre was soaked in 0.2 per cent solution of potassium alum or aluminium sulphate for 12 to 15 hours followed by washing and then treated with 1 per cent sodium hydroxide solution in boiling condition for two hours. The fibre was left in the hot alkaline solution for about 6 hours, washed and then scoured in 0.2 per cent hydrochloric acid solution for two hours in boiling condition followed by washing and drying. Thomson and Lee5 developed a degumming method of decorticated ramie ribbons by boiling in a solution containing soda ash, sodium tetraphosphate and Santomerse (Monsonato Chemicals Ltd., London) followed by rinsing, washing and then cooking for one hour in a solution containing aluminium phosphate and Tergitol 08 (Union carbide Ltd, Manchester). In a degumming method described by Petruszka6, decorticated ramie ribbons were cooked for one hour at 6kg/cm2 pressure (160°C) with a liquor containing 6% sodium hydroxide, 3% sodium sulphite, 3% sodium tripolyphosphate and 3% organic phosphate penetrant. The process was repeated with the same solution and the fibre was washed with water. A simple and cheap method of combined degumming and bleaching of ramie was described by Kundu7 in which the decorticated fibres were boiled two time successively for two hour each in lime water, washed and rinsed, boiled in 1% sodium carbonate for half an hour, washed and rinsed and finally treated in cold aquous solution of chlorinated lime containing 1% chlorine, washed, rinsed and dried. An in-line method described by Allison and Boots8 reduced the time of open-vesel degumming to 7 to 10 minutes for degumming of ramie fibres in an in-line degumming apparatus though the contents of degumming solution were not disclosed. The degummed fibres were coarser than the fibres obtained by conventionally known presure degumming system by a factor of 1.5 to 2.0 units or more suggesting incomplete degumming by such inline apparatus. Lerche9 reported degumming of ramie in the form of ribbons to cotton-like or wool-like ramie by treatment with 3 per cent sodium hydroxide solution at 100°C for two hours followed by washing and drying. Nandi et al.10 described a process for degumming of ramie fibre by boiling with alkali in large open pans and also by microbiological retting. Das Gupta et al.3 reported degumming of decorticated ramie fibre with one per cent alkali solution at an elevated temperature in open digester or under pressure. Venkataswaran11 described a process for degumming of ramie fibres by ethanol extraction of the fibres for 2 to 4 hour followed by treatment with boiling sodium hydroxide solution for 2 hour. In another process, ramie fibres, after soaking overmght in ethanol, were washed in deionised water. Paul and Bhattacharyya12 reported a combined microbial and chemical deguming of decorticated ramie in which the decorticated fibre was partly degummed by a mixed bacterial culture isolated from the rhizosphere of sunn fibre (Crotaralia juncia Linn.) and then boiled with 0.5 per cent sodium hydroxide solution for further removal of gum. Essentially most of the known degumming processes of decorticated ramie consist of treatment of the decorticated ramie in sodium hydroxide solution for an interval of time at elevated temperature in an open or closed vessel. This is a batch process and after degumming treatment the liquor is drained off or wasted. The degumming process results in a weight loss of about 15 per cent to 25 per cent with respect to the weight of decorticated ramie due to loss of degraded gum. The degumming liquor consists of some unused alkali and degraded ramie gum from the degumming operation in low concentration in a dispersed state in the hot alkaline aqueous medium and is discharged as such without any use thereby causing environmental pollution. Economics of the degumming process is largely controlled by the factors such as amount of alkali consumed, energy input and time required to perform the degumming process. The main purpose of this inventive effort is to use the degumming liquor for further use in the degumming process so that the alkali, chemicals, water and thermal energy which are wasted by draining off the degumming liquor is recycled and utilized for the subsequent degumming operations. This also enriches the degumming liquor in gum content thereby making its recovery possible for industrial use although this is not an essential step in the degumming operation. Environmental pollution would also be avoided as the degumming liquor would not be drained off after each degumming operation. Above all, the degumming process would be more economic by lowering the requirements of chemicals, water and energy. No process of degumming ramie which addresses the aforesaid problems is known to have been disclosed. Detailed Description of the Invention: Example 1: Decorticated ramie fibre (500 gms) was placed in a stainless steel perforated cylindrical container, the container was then put in a laboratory digester having stainless steel interior and electric heating arrangement with a temperature recorder. The fibre bundles were immersed in 3000 ml. aqueous alkaline solution of one per cent sodium hydroxide (30 gms.) in the degumming bath in a fibre to liquor ratio of 1:6. About 0.1 per cent of an anionic wetting agent (~30 mg.) on the weight of sodium hydroxide and 0.25 per cent of sodium sulphite (7.5 gms) were added in the degumming bath. The alkaline treatment solution containing decorticated fibre was heated to about 120°C under pressure for 2 hours. The fibre was then taken out for washing and the hot alkaline degumming liquor, dark brown in colour due to presence of degraded gum, was preserved. The degummed ramie was washed with one litre of hot water and the washings were collected. The ramie fibre was then hydroextracted in a centrifuge type hydroextractor and the liquid was collected. All these preserved and collected liquors were combined together and water, if necessary, was added to it to generate the second degumming bath of required volume i.e. 3000 ml. The sodium hydroxide content of the second degumming bath was estimated and found to be 0.2 per cent. Additional sodium hydroxide (24 gms) was added to the aqueous medium in the second degumming bath measuring 3000 ml. to achieve one per cent sodium hydroxide concentration. Sodium sulphite and anionic wetting agent were also added in measured quantities in the second degumming bath to achieve the concentrations as mentioned above for the first degumming bath. Second lot of 500 gms decorticated fibre was then immersed in the degumming liquor in the second degumming bath and degumming was carried out at about 120°C for two hours under pressure as described above. The fibre was then taken out for washing and the same process of collecting the hot degumming liquor and washings of degummed fibre from the second degumming operation as described above was repeated for generating the third degumming bath, and similarly for generating the fourth degumming bath by recycling the hot degumming liquor and washings obtained from the third degumming operation by the same process as described above, for degumming third and fourth lots of decorticated ramie of 500 gms each. The degummed fibre, obtained in each batch after washing and hydroextraction as mentioned above, was washed with 2 per cent hydrochloric acid, water, and finally with water containing 0.1 percent catasoftener on the weight of fibre and dried in hot air oven or in air. The degumming liquor was concentrated further in hot water bath for possible use in industry. Example 2: Decorticated ramie fibre (500 gms) was taken in a perforated cylindrical container made of stainless steel and placed inside a digester having stainless steel interior and electric heating system with a temperature recorder. The fibre was immersed 3500 ml. of an aqueous solution of one per cent sodium hydroxide (35 gms.) containing ~ 70 mg. of a suitable anionic wetting agent ( 0.2% on the weight of sodium hydroxide) and 0.25% sodium sulfite (8.75gms.) maintaining the fibre to liquor ratio at 1:7. The solution was heated to about 95°C for 2 hours keeping the fibre immersed in the solution. The fibre was then taken out for washing and the hot alkaline degumming liquor, dark brown in colour due to presence of degraded gum, was preserved. The degummed ramie was washed with one litre of hot water and the washings were collected. The ramie fibre was then hydroextracted in a centrifuge type hydroextractor and the liquid was collected. All these preserved and collected liquors were combined together and water, if necessary, was added to it to generate the second degumming bath of required volume i.e. 3500 ml. The sodium hydroxide content of the second degumming bath was estimated and found to be 0.16 per cent. Additional sodium hydroxide (29.4 gms) was added to the aqueous medium in the second degumming bath measuring 3500 ml. to achieve one per cent sodium hydroxide concentration. Sodium sulphite and anionic wetting agent were also added in measured quantities in the second degumming bath to achieve the concentrations as mentioned above for the first degumming bath. Second lot of 500 gms decorticated fibre bundle was immersed in the hot degumming liquor in the second degumming bath and degumming was carried out at about 95°C for two hours as described above. The fibre was then taken out for washing, and the same process of collecting hot degumming liquor and washings of degummed fibre from the second degumming operation as described above was repeated for generating third degumming bath, and similarly for generating the fourth degumming bath by recycling the hot degumming liquor and washings obtained from the third degumming operation by the same process as described above, for degumming third and fourth lots of decorticated ramie of 500 gms each. The degummed fibre, obtained in each batch after washing and hydroextraction as mentioned above was washed with 2 per cent hydrochloric acid, water, and finally with water containing 0.1 percent catasoftener on the weight of fibre and dried in hot air oven or in air. The degumming liquor was concentrated further in hot water bath for possible use in industry. References: 1. Kirby, R.H., Vegetable Fibres, p. 163, (1963), London: Leonard Hill 2. Chakraborti, A.C., Sen, S.K. and DasGupta, P.C., The effect of gum content on the physical properties of ramie fibre, Journal of Textile Association, 33(2), 73-79 (1972). 3. DasGupta, P.C., Sen, K. and Sen, S.K., Degumming of decorticated ramie fibre for textile purposes, Cellulose Chemistry and Technology, 10,285-291(1976). 4. Luniak, B., Ramie - degumming and textile processing, Textile Quarterly, 4, 92-103 (1954). 5. Thomson, G. and Lee, H.N., American experiments in the degumming of ramie, Fibres (Eng. Chem.), 18(8), 272-281 (1957). 6. Petruszka, M., Ramie fibre production and manufacturing, Report of Food Agriculture and Industry Services, Agriculture Services Division,AGS: MISC/77/5, FAO,Rome, 14pp. (1977). 7. Kundu, B.C., Ramie fibre and its development in India, Science and Culture, 23(9), 461-470 (1958). 8. Allison, R.V. and Boots, V.A., Progress report on the chemical degumming of ramie by an in-line open-cook process, Soil and Crop Science Society of Florida Proceedings, 22,176-185 (1962). 9. Lerche, K., American Diary: 1961, Kenya Sisal Board Bulletin, No. 39, 31-37 (1962). 10. Nandi et al., Cultivation of ramie in West Bengal, India, Soil and Crop Science Society of Florida Proceedings, 24, 418-425 (1964). 11. Venkataswaran, A method for degumming and bleaching ramie fibres and their physical properties, Tappi, 48(3), 191-192 (1965). 12. Paul N.B. and Bhattacharyya S.K., The microbial degumming of raw ramie fibre, Journal of Textile Institute, 70(12), 512-517,1979 WE CLAIM. 1. A method for degumming of decorticated ramie fibres containing 20% to 30% gum to obtain ramie fibres of gum content in the range of 2% to 8%, to remove the gum and pectin containing materials therefrom, comprising the steps of, treatment of decorticated ramie in a degumming bath containing 0.5 per cent to 2.5 per cent sodium hydroxide, an anionic wetting agent in 0.1 to 1.0 per cent by weight, based on sodium hydroxide and sodium sulphite in 0.25 to 1.25 per cent based on the weight of sodium hydroxide, and maintaining a fibre to liquor ratio between 1:5 to 1:8. maintaining the said aqueous alkaline treatment solution containing decorticated ramie at an elevated temperature between 80°C and 125°C (under pressure) for one hour to three hours, followed by washing and hydroextraction of the degummed ramie to obtain the hot degumming liquor, combining the hot, dark brown, alkaline degumming liquor obtained from the first or previous degumming baths combined with the washings of degummed fibre. followed by generating a second degumming bath of aqueous alkaline medium therefrom, by addition of required amount of sodium hydroxide, sodium sulfite to achieve the concentration of the second degumming bath to be the same as the first degumming bath and adding water, if necessary to maintain the liquor ratio between 1:5 and 1:8 in the bath, degumming a second lot of the same fixed weight of decorticated ramie in the second degumming bath followed by recycling the second and further degumming baths by similar steps of fortification, for use in degumming two to four further batches of decorticated ramie. 2. The process as claimed in claim no. 1 wherein the same degumming liquor is recycled to be used as the degumming medium for four to six batches of fresh decorticated ramie after suitable fortification after each degumming operation.

Documents:

17-DEL-2002-Abstract.pdf

17-del-2002-claims.pdf

17-del-2002-correspondence-others.pdf

17-del-2002-correspondence-po.pdf

17-del-2002-description (complete).pdf

17-del-2002-form-1.pdf

17-del-2002-form-19.pdf

17-del-2002-form-2.pdf

17-del-2002-form-3.pdf