Title of Invention

A PROCESS FOR RETTING OF FIBRES

Abstract This invention relates to a process for the retting of fibres such as jute, kenaf, sisal or ramie comprising subjecting a plant to a step of decortication to obtain decorticated plant fibres followed bya step of chemical retting comprising of afirst step of swelling the fibres in an alkali solution of 5-25% concentration for 2 to 12 hours, followed by a second step of treatment with a solution selected from sulphates and sulphites for 6 to 18 hours to obtain the retted fibres, subjecting the retted fibres to bleaching and the bleached fibres are optionally treated with an acid to reduce the ash content to obtain the retted plant fibres.
Full Text FIELD OF THE INVENTION
This invention relates to a process for retting of fibres.
BACKGROUND OF THE INVENTION
Traditional retting involves the rotting of fibres? such as jute
or kenaf in pools of water formed during the monsoons after which it has to be 'walked over' by farmers or farm labour. The entire process of retting takes about two or three weeks. It commences only after the monsoons arrive. Therefore, if the monsoons arrive late, three types of fibre is produced from the same plant because of over—aging. Due to the rotting process in bacteria infested water, the fibres become weak and farmers cannot produce a consistent quality of fibre from any one plant since the same bacteria infested water is used repeatedly. The method involves direct human contact with dirty, muddy and bacteria infested water in which rotting jute or kenaf remain immersed for a long time and this results in various diseases.
No high—value derivatives can be obtained from such jute or kenaf, and the major portion of the lignin content of the jute or kenaf is lost in the pools of water and the balance remains in the fibre or stick, making them less resilient, incapable of being converted to other high value derivatives, and incapable of taking on permanent dye.
OBJECTS OF THE INVENTION
It is therefore an object of this invention to propose a process
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For the retting of fibres which is inexpensive and less time consuming and is not dependent on the arrival of the monsoons.
It is a further object of this invention to propose a process for the retting of fibres which can be done under controlled conditions and does not cause any pollution.
Another object of this invention is to propose a process for the retting of fibres which produces superior quality of fibres or cellulose with possibilities of being used for multifarious purposes.
Yet another object of this invention is to propose a process for the retting of fibres which makes it possible to recover by-products.
These and other objects of the invention will be more apparent from the ensuing description.
BRIEF DESCRIPTION OF THE INVENTION
Thus according to this invention is provided a process for the retting of fibres such as jute, kenaf, sisal or ramie comprising subjecting a plant to a step of decortication to obtain decorticated plant fibres followed bya step of chemical retting comprising of afirst step of swelling the fibres in an alkali solution of 5-25% concentration for 2 to 12 hours, followed by a second step of treatment with a solution selected from sulphates and sulphites for 6 to 18 hours to obtain the retted fibres, subjecting the retted fibres to bleaching and the bleached fibres are optionally treated with an acid to reduce the ash content to obtain the retted plant fibres.
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are optionally treated with an acid to reduce the ash content to obtain the retted plant fibres.
In accordance with this invention! plants such as jute, kenaf, hemp, sisal or ramie are decorticated by treating with a 3—30% solution of a sulphate, such as for eg. ammonium sulphate for about 3 to 24 hrs., depending on the age of the plant.
The treatment may preferably be with a 10-30% solution for about
10-24 hrs. Alternatively, a 3 to 5% solution of the sulphate is
used for about 6 to 18 hrs. depending on the age of the plant and
optionally heating at approximately 50 to 95 oC, to obtain the
decorticated plant fibres. This is followed by the step of chemical retting whereby the decorticated plant fibres are just swelled by treating with a cold solution of alkali of 5-25% concentration for about 30 mins. to 4 hrs. , and then they are treated with a 1.0 to 10*/. solution of a sulphate or sulphite for approximately 2 to 18 hrs, depending on the age of the plant. Preferably, the fibres are treated with a 2.5—10% solution for approxminately 6—18 hrs. depending on the age of the plant or optionally heated for approximately 2 to 5 hrs. with a 1.0 to 5% solution of the sulphate or sulphite. The sulphates and sulphites are such as ammonium, calcium, sodium, magnesium, potassium or similar sulphates and sulphites. It is preferred not to boil except in the case of sisal and ramie, to avoid evaporation which would lead to the chemical solution becoming more concentrated. This could have a detrimental effect on the fibre and also lead to unnecessary wastage of the chemical. During the above two

steps of decorticating and chemical retting, lignin from the plant/fibre/stick is released into the sulphate solution and is recovered by removal of cellulose, by means of filtration) in liquid form or in powder form by evaporation of one kind or other. Thereafter) chemical eellulose of high purity alpha cellulose is obtained by application of an alkali solution of 15 to 25% concentration for a predetermined period depending on the age of the plant. This is followed by bailing in 8.5 to 12.5% concentrated solution for a predetermined period depending on the age of the plant. This drastically reduces the remnant lignin as also pectin, hemicelluloses, beta and gamma cellulose, etc.. The processed jute/kenaf/hemp is thereafter bleached to free the surface of the plant/fibre/stick from the bonding material covering it, and thus allow the sulphate and/or the alkali to react. Bleaching with a weak hypochlorite solution) such as sodium hypochlorite is also done to obtain the desired shade in the jute, kenaf) hemp, sisal or ramie fibres.
In an alternative embodiment of this invention, an organic acid such as for eg. actic acid is used for treating the fibres, for softening and reducing ash content. These are beneficial for yarns for fabrics and for pulp for paper respectively. During this treatment, heating is not required.
In yet another embodiment according to this invention, oxalic acid is used far treating the fibres. In this treatment too, no heating is required. The oxalic acid treatment softens the fibres
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and increases the lustre. However, it is preferred to use sulphate solution for decorticating and chemical retting for reasons of economy, strength of fibre and for avoiding pollution hazards.
In the process according to this invention , the chemical retting process of jute, kenaf and hemp is done under controlled conditions as these plants can be harvested and retted at the desired or predetermined time without waiting for the arrival of the monsoons and formation of pools of water which is usually essential to the conventional or traditional method of retting. It therefore also avoids health hazards for the farmers and farm labour. The chemicals chosen for retting are also cheap and the quantities required are low. The time involved for the chemical retting process is only a few hours as compared to about 3 weeks in case of the conventional method of retting. The main chemical, being used for retting and converting to celluloses is pollution-free .
The quality of fibre obtained is superior in terms of fineness, uniformity, strength, flexibility and lustre. Such fibres can be used for multifarious purposes such as pulp for paper, superior yarn for fabrics and also for a host of chemical derivatives. The extracted lignin and ethanol obtained have innumerable end uses of high value.
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WE CLAIM;
1. A process for the retting of fibres such as jute, kenaf, sisal or ramie
comprising subjecting a plant to a step of decortication to obtain decorticated
plant fibres followed bya step of chemical retting comprising of afirst step of
swelling the fibres in an alkali solution of 5-25% concentration for 2 to 12 hours,
followed by a second step of treatment with a solution selected from sulphates
and sulphites for 6 to 18 hours to obtain the retted fibres, subjecting the retted
fibres to bleaching and the bleached fibres are optionally treated with an acid to
reduce the ash content to obtain the retted plant fibres.
2. The process as claimed in claim 1 wherein said plant is, such as jute, kenaf,
hemp, sisal, ramie.
3. The process as claimed in claim 1 wherein said step of decortication comprises
treating the plants with a 3-30% sulphate solution such as ammonium sulphate
for 3-24 hrs..
4. The process as claimed in claim 1 wherein said step of decortication is carried
out preferably with a 10-30% for 10-24 hrs. depending on the age of the plant.
5. The process as claimed in claim 1 wherein said step of decortication is carried
out with a 3-5% solution of the sulphate for 6-18 hrs. and optionally heating the
solution at a temperature in the range of 50-95° C.
6. The process as claimed in claim 1 wherein said step of swelling comprises
treating the decorticated plant fibres with a 5-25% cold solution of alkali for 30
mins. to 4 hrs.
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7. The process as claimed in claim 1 wherein said second step of
treatment with a sulphate or a sulphite solution comprises
treatment with a 1.0—10% solution of a sulphate or sulphite,
such as ammonium calcium, sodium, magnesium, potassium or similar sulphates and sulphites for about 2-18 hrs..
8. The process as claimed in claim 7 wherein said second step of
treatment with a sulphate solution comprises treatment with 2.5-
10% solution of a sulphate for 6-18 hrs..
9. The process as claimed in claim 7 wherein said second step of
treatment comprises optionally heating the swelled solution with
a 1.0—5% solution for 2-5 hrs-.
10. The process as claimed in claim 1 wherein the fibres are filtered free from lignin before bleaching.
11. The process as claimed in claim 1 wherein the step of
bleaching is carried out using a weak hypochlorite solution.
12. The process as claimed in claim 1 wherein the acid used for
reducing the ash content is, such as acetic acid, oxalic acid.
13. The process for retting of fibres substantially as herein
described and illustrated.
This invention relates to a process for the retting of fibres such as jute, kenaf, sisal or ramie comprising subjecting a plant to a step of decortication to obtain decorticated plant fibres followed bya step of chemical retting comprising of afirst step of swelling the fibres in an alkali solution of 5-25% concentration for 2 to 12 hours, followed by a second step of treatment with a solution selected from sulphates and sulphites for 6 to 18 hours to obtain the retted fibres, subjecting the retted fibres to bleaching and the bleached fibres are optionally treated with an acid to reduce the ash content to obtain the retted plant fibres.

Documents:

00259-cal-2002 abstract.pdf

00259-cal-2002 claims.pdf

00259-cal-2002 correspondence.pdf

00259-cal-2002 description (complete).pdf

00259-cal-2002 description (provisonal).pdf

00259-cal-2002 form-1.pdf

00259-cal-2002 form-18.pdf

00259-cal-2002 form-2.pdf

00259-cal-2002 form-26.pdf

00259-cal-2002 form-3.pdf

00259-cal-2002 form-5.pdf

00259-cal-2002 letters patent.pdf

259-CAL-2002-(22-05-2012)-CORRESPONDENCE.pdf

259-CAL-2002-(22-05-2012)-PA.pdf

259-CAL-2002-FORM 15.pdf


Patent Number 201766
Indian Patent Application Number 259/CAL/2002
PG Journal Number 08/2007
Publication Date 23-Feb-2007
Grant Date 23-Feb-2007
Date of Filing 03-May-2002
Name of Patentee GOUTAM G BANERJEE
Applicant Address 91 SHAKESPEARE SARANI, KOLKATA-700 017.
Inventors:
# Inventor's Name Inventor's Address
1 BANERJEE GOUTAM G 91 SHAKESPEARE SARANI KOLKATA-700017
PCT International Classification Number D 02 G 1/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA