GB2375548A

GB2375548A - A process for cellulose extraction

Info

Publication number: GB2375548A
Application number: GB0112212A
Authority: GB
Inventors: Iqbal Wahla; Azmat Anwar
Original assignee: RIST INTERNAT Ltd
Current assignee: RIST INTERNAT Ltd
Priority date: 2001-05-18
Filing date: 2001-05-18
Publication date: 2002-11-20
Anticipated expiration: 2021-05-18
Also published as: GB0112212D0; GB2375548B

Abstract

A process for the extraction of cellulose from a cellulose-containing material, the process comprising: ```providing a raw material comprising or ```consisting of cellulose; ```forming a mixture comprising the raw material ```and water; ```adding a digestion liquor, said digestion ```liquor comprising an algae excretion, a ```polysaccharide and an oxidising agent; whereby cellulose is extracted from the raw material to form a material comprising or consisting of pulp.

Description

A PROCESS FOR CELLULOSE EXTRACTION The present invention relates to the field of cellulose extraction and, in particular, to a process for producing various grades of cellulose from cellulose-containing materials such as jute and cotton.

Cellulose is a natural carbohydrate high polymer, and is the fundamental constituent of all vegetable materials (for example, wood, grass and flowers). It is a colourless solid which exists in three forms, alpha-, beta-and gamma-cellulose. Of these, alpha-cellulose has the highest degree of polymerization, the beta and gamma forms often being known as hemicellulose.

Numerous processes and systems for cellulose extraction have been documented. A primary aim of each process is to separate cellulose from the major noncarbohydrate constituents such as, for example, lignin and silicon dioxide of the raw material being processed.

Extraction processes initially yield cellulose in the form of"pulp". The form of cellulose constituting the pulp helps to determine the commercial use of the pulp-derived product.

For example, pulps with an alpha-cellulose content of 50 - 80% can be used for filter media and are classified as"Filter Pulp or"High Premier Quality Pulp".

Pulp with an alpha cellulose content of 85% or greater is termed"dissolving pulp"and may be used in, for example, laquers in the paint industry, converted to

carboxymethylcellulose for use in food products, in tera ? materials such as melamine and cellophanes, in viscose and in products derived from microcrystalline cellulose powder.

The various types of pulp containing processed cellulosic fibers referred to above may be obtained from hardwoods, softwoods or plants.

Currently, approximately 85% of world pulp demand is met from wood as a raw material and the remaining 15% from raw materials such as straw and bamboo.

The sources of wood can be further divided into softwood and hardwood. The length of the fibers contained in the softwood or hardwood helps determine the strength of the cellulose-containing material extracted from it.

For example, Kraft pulp, which is used to produce Kraft paper, is known for its high strength, derived from a raw material containing long fibers. These long fibers are only provided by a small group of softwood trees.

Softwood and hardwood raw materials can be combined; for example, a large proportion of the world's pulp for the paper and paperboard industries uses 25% softwoods and 75% hardwoods.

The high alpha-cellulose content of dissolving pulp requires that, preferably, the raw materials used for its production have a high residual alpha-cellulose content.

In its simplest form, conventional cellulose extraction can be divided into the three main steps of

pulping, bleaching and washing.

The first step, pulping, may be carried out either mechanically or chemically.

An example of a mechanical pulping process is The Chemi Thermo High Yield Mechanical Pulping Process.

This process is representative of mechanical pulping processes, in that although the pulp yield is high, the resulting cellulose fiber is damaged, restricting the type of materials for which it is suitable.

Similarly, in The Refiner Mechanical Pulping Process, the pulp yield is also high, but again the cellulose fiber is damaged, resulting in the cellulosecontaining products obtained (such as paper) having poor bleachability. It is generally the alphacellulose fiber which is damaged in the course of mechanical pulping.

In contrast to mechanical pulping, chemical pulping involves the"digestion"of the raw material with an appropriate solution (a"digestion liquor") inside a pressure vessel known as a"digester". The raw material from wood is typically fed into the digester in the form of chips, and then the digestion liquor added. During digestion, lignin (the major noncarbohydrate constituent of wood) is separated from the cellulose, since it is dissolved by the digestion liquor.

Three products of chemical pulping are particularly well known in the field, depending upon the particular digestion liquor used.

The first, soda process pulp, is obtained from the digestion of wood chips (mostly poplar) by caustic

soda.

The second, sulfite process pulp (mostly from spruce and other coniferous woods) is obtained by digestion with a solution of magnesium, ammonium or calcium disulfite containing free sulphur dioxide.

Thirdly, sulphate process pulp is produced when sodium sulphate is added to the caustic liquors. The sulphate is reduced by carbon present to the sulphide, which then becomes the digesting agent.

The digestion liquors used in chemical pulping are either produced in the pulp plants themselves or produced and supplied commercially. Their production often leads to the release of harmful gases into the atmosphere.

In addition, due to the corrosive nature of the digestion liquors, extensive damage to the machinery used in the chemical pulping process often occurs.

Subsequently, there is damage to the cellulose fiber of the pulp.

Finally, the digestion process itself also leads to the release of noxious, sulphur-containing compounds (such as sulphides and thiols) into the atmosphere.

The use of a High Pressure Steam Process for the production of pulp from raw materials is an alternative to mechanical and chemical pulping.

However, there are also environmental considerations when using this process, since the use of fuels such as coal, natural gas, furnace oil or wood to produce the steam in a boiler also results in the release of environmentally hazardous gases.

The second main step involved in conventional cellulose extraction processes, bleaching, involves the use of agents such as chlorine (cil2) and hydrogen peroxide (H202) to bleach the products resulting from the pulping of raw materials.

The bleaching process generally requires the use of bleaching towers and specialized equipment, including strict handling procedures for the transfer of hazardous chemicals.

The third step, washing, typically utilizes large volumes of water (approximately 100 tonnes of water per tonne of pulp). The wash effluent also contains bleaching chemicals in conventional processes, and therefore is hazardous to the environment. The presence of contaminants in the effluent material necessitates use of recovery systems to render the effluents safe.

Existing processes for cellulose extraction often require 4-6 hours for the digestion step alone. Often, processes and systems are specific to certain raw materials, thereby increasing cost.

Existing processes tend to be directed to the use of wood and cotton as the raw material. There is currently much effort worldwide to find alternative fibrous raw materials to replace wood, primarily for environmental reasons. In addition, due to the low (approximately 20%) residual alpha-cellulose content of most woods, the cellulose containing products obtained from it cannot be used in those specialized applications requiring products containing a high alpha-cellulose content.

Accordingly, the present invention provides a process for the extraction of cellulose from a cellulosecontaining material, the process comprising: providing a raw material comprising or consisting of cellulose; forming a mixture comprising the raw material and water; adding a digestion liquor, said digestion liquor comprising an algae excretion, a polysaccharide and an oxidising agent ; whereby cellulose is extracted from the raw material to form a material comprising or consisting of pulp.

A range of raw materials comprising or consisting of cellulose are suitable for extracting cellulose according to the process described above; for example, cotton, wood and jute.

When using a raw material comprising or consisting of cotton or jute, it has been found that the pulp produced from the process described above may comprise in excess of 65% of alpha-cellulose.

The digestion liquor used in the process described above comprises an algae excretion, a polysaccharide and an oxidising agent.

The algae excretion is preferably obtained from the strain"Gigartina Stellata", cultured under standard laboratory conditions.

The polysaccharide is preferably cellulose, which may

be added in a powdered form.

The oxidising agent preferably comprises a solution of

sodium hydroxide (NaOH) in which chlorination is achieved by injecting chlorine (Clz) gas. The particular, active oxidising ingredient in the digestion liquor may comprise NaOCl, according to this formulation.

A preferred digestion liquor comprises from 6 to 30 g (preferably 12g) of powdered cellulose; from 5 to 25ml (preferably 10ml) of an algae excretion from the strain"Gigartina Stellata" ; from 50 to 200ml (preferably 100ml) of a 1.5 to 4 molar (preferably 2.5 molar) solution of sodium hydroxide which is chlorinated by injecting 2-6% (preferably 4%) chlorine (Cl2) gas, the concentration of chlorine being established by titration.

When forming a mixture of the raw material jute with water and adding a digestion liquor as described above, digestion can be achieved in as little time as 25 minutes. Another advantage is that digestion can be achieved, without the use of any external heating means. That is, the process may be carried out at room temperature (20-30 C).

Preferably, raw material is added to water such that there is a ratio of from 1: 2 to 1: 8 of raw material to water. Digestion liquor is then added such that there is a ratio of from 1: 8 to 1: 32 of digestion liquor to water.

It has been found preferable to store the digestion liquor used in an oxygen-rich environment with a moisture content of 15-25% and at a storage

temperature between 20 and 30'C, prior to use. The preferred storage vessel for the digestion liquor is a reservoir made of stainless steel.

Unlike in existing pulping processes where digestion times of several hours are required, it has been found that the desired level of digestion can be achieved in only 20-30 minutes in the present invention.

Furthermore, the digestion apparatus comprises a mixer, operating under ambient temperature and pressure, unlike conditions employed in existing methods, which often require digesters operating at temperatures in the range of 145-160 C and pressures of 100-120 psi. Furthermore, whereas existing pulping methods often employ corrosive and highly pungent chemicals, the current technology is based upon substantially odourless and relatively dilute biochemical solutions.

It is suggested that in the present invention, the polysaccharide (for example, cellulose) contained in biochemical solution creates a microenvironment for the solubilization of the fibers of the raw material, for example jute. Consequently, the liquor penetrates quickly into the body of the fibers, initiating the action of weakening"intra-fibril"bonding. Within just 10 minutes, the liquor may completely penetrate into the outer body of the fibers and begin to dissolve non-carbohydrate molecules such as lignins and silicon dioxide.

Complete solubilization of bonding material may be effected after a further 10-15 minutes, thus rendering digestion, and hence pulping, complete in a total of 20-25 minutes according to the method described.

Preferably, the raw material provided passes through a shredder and is shredded to a suitable length prior to digestion. In the case of the production of certain grades of cellulose, shredding can maximise the strength of the resulting fibers and can increase yield.

In addition, prior to digestion, the raw material may be fed into a dusting unit thereby removing dust particles. Following the dusting step, the raw material may enter a washer, to remove the remaining dust and any other impurities.

Particularly in cases where the raw material must be transported to another site for the digestion process, it has been found preferable that it enters a bailing unit where it is compacted into bails and covered with a protective material following the dusting and washing steps.

Following digestion, the resulting pulp may be fed into a system of washers, responsible for separating off excess liquid, and any impurities. It is suggested that the cavities produced by the solubilization of bonding material during the digestion step are filled by water molecules in this washing stage.

It is possible to recover the digestion liquor used in the present invention, following the washing stage described above. The effluent from the washers may be filtered to separate impurities, which are then discharged, while the remaining digestion liquor may be returned to a chamber where it is made into fresh digestion liquor.

Further to the digestion and washing steps described above, the resulting pulp may now be treated in a

number of ways, depending upon the desired grade of product in the cellulose extraction process.

In the production of certain grades of cellulose, a "defibration" step may be carried out, effecting the mechanical compression of the pulp resulting from the digestion and washing steps.

Within the pulp, fibers are saturated with liquor plus water, and defibration compels the water and liquor solution out of the fibers, at the same time splitting the fibers, thus converting them into"fibrils". In contrast with existing methods, the defribrator apparatus used in the present invention does not require the use of a boiler to produce steam, thus reducing energy consumption and costs.

The creation of fibrils alters the nature of bonding in the pulp, and increases the strength of the final product. Following defibration, micro analysis techniques may be used to monitor the bonding characteristics in the fibrils, ensuring that maximum kinking has taken place.

Following defibration, the pulp may be obtained in a form containing approximately 67% alpha-cellulose, and, as such, is often referred to as"premier quality unbleached pulp". Premier quality unbleached pulp is suitable for use in a wide variety of paper and hardboard products.

In the production of certain grades of cellulose, the pulp may now pass to an Acid Base Shock Chest where it undergoes an Acid-Base Shock treatment, which may have the effect of increasing the hardness and strength of the material.

The Acid-Base Shock treatment comprises treatment of the pulp with an alkaline liquor, significantly raising the pH, and treatment of the pulp with acidic liquor, significantly reducing the pH.

Preferably, the alkaline liquor is added first, followed by the addition of the acidic liquor.

A preferred alkaline liquor comprises a 2 to 4 molar (preferably approximately 3 molar) solution of sodium hydroxide (NaOH).

A preferred acidic liquor comprises from 10 to 15ml (preferably approximately 12ml) of an acidic solution extracted from the algae"Gigartina Stellata", cultured under standard laboratory conditions.

Preferably, both alkaline and acidic liquors are added such that there is 1 litre of liquor per 2 to 10kg (preferably 5kg) of dry weight of cellulose. The dry weight of cellulose is established by use of a hydrometer. The pulp may be exposed to the resulting mixture for a period of from 10 to 30 minutes, preferably from 15 to 25 minutes, still more preferably approximately 20 minutes.

In the production of certain grades of cellulose in the present invention, the pulp may preferably be subjected to more than one Acid-Base shock treatment, and between the first and second treatments, the pulp may pass through washers, in order to separate debris from the desired material.

The pulp may also enter a bleach chest, in which it undergoes one or more bleaching steps. Bleaching is preferably followed by washing. In this way, the bleaching liquor can be recovered, by passing the

effluent from mechanical washers through a filtration medium, thus separating solid impurities from the liquor. The liquor may then be pumped back to a liquor chamber where it is reused for the fresh preparation of liquor, thus improving cost efficiency.

In the present invention, is has been found that the pulp has a high absorption affinity for the bleaching liquor, particularly when it is in the form of fibrils, following a defibration step. The bleaching liquor dissolves the colouring pigments in the superficial layers of the fibrils, possibly through an oxidative mechanism.

A preferred bleaching liquor comprises from 5 to 7 molar (preferably approximately 6 molar) solution of sodium hydroxide (NaOH) ; an injection of from 1 to 10 % (preferably 5%) chlorine gas, the chlorine concentration being established by titration; and from 5 to 15 ml (preferably 10ml) of a solution excreted from the algae"Gigartina Stellata", cultured under standard laboratory conditions.

Preferably, the bleaching liquor is added such that there are 1.5 litres of liquor per 2 to 8kg (preferably 4kg) of dry weight of cellulose. The dry weight of cellulose is established by use of a hydrometer. The pulp may be exposed to the bleaching liquor for a period of from 5 to 60 minutes, preferably from 15 to 45 minutes, more preferably still from 20 to 30 minutes.

When the pulp has undergone two successive bleaching steps, it may be obtained in a form containing approximately 67-85% alpha cellulose, and, as such, is often referred to as"premier grade bleached pulp".

Premier grade bleached pulp is suitable for use in

products such as writing and printing paper, duplex board, bleached board and file card.

For the production of certain grades of cellulose, a heater is attached to the bleaching mixer in a second bleaching step, whereupon heating to a temperature of from 60 to 80 C, (more preferably 70 C) for a period preferably of from 5 to 60 minutes (more preferably from 10 to 15 minutes), leads to liquefaction of the contents of the mixer.

In the production of certain grades of cellulose, the first or subsequent bleaching step may be followed with a further Acid Base Shock treatment.

In the production of certain grades of cellulose, pulp is passed through a dryer which has the effect of reducing the moisture content to a value of approximately 10% (established with the aid of a hydrometer) through a spinning mechanism.

In the production of certain grades of cellulose, the dried material enters a pulveriser and is pulverised, after which its mesh-size is quantified. For example, a mesh size of 200 corresponds to a particle size in the range of 74 micrometers. The pulverised material of the desired particle size may then be obtained by sieving through a mesh of appropriate size.

In the production of certain grades of cellulose, a filtration step may be required to remove solid residue, prior to obtaining the final product.

The particular grade of cellulose which has been extracted, is packed according to its physical form.

For example, in the case of an extract in liquid form,

bottles may be used. In the case of a solid material, another appropriate packaging, such as compaction into bails, may be used.

The present invention will now be described further, by way of example, with reference to the following drawings :- Figure 1 is a flow diagram outlining the process steps for Example 1; Figure 2 is a flow diagram outlining the process steps for Example 2; Figure 3 is a flow diagram outlining the process steps for Example 3; Figure 4 is a flow diagram outlining the process steps for Example 4; Figure 5 is a schematic illustration of an apparatus suitable for producing fibrous cellulose from raw jute, in accordance with the invention, and described in Example 1.

The process described in the present invention will now be exemplified, with reference to the extraction of four grades of cellulose.

The four grades of cellulose are fibrous cellulose, dissolving pulp, microcrystalline cellulose powder and liquid cellulose.

Example 1: Production of Fibrous Cellulose from jute: Fibrous cellulose is a specific grade of the cellulose present in dissolving pulp, and may contain a concentration of alpha-cellulose of from 85 to 99.9% when produced by the following method: The first steps in the production of fibrous cellulose are the shredding, dusting, washing and bailing of the jute provided as raw material.

The bails of jute are then placed in a digestion mixer and soaked in water. Next, a volume of digestion liquor comprising :- 100ml 2.5 molar NaOH ; an injection of 4% Chlorine gas ; 12g powdered cellulose ; and 10ml of a solution excreted from the algae"Gigartina Stellata", cultured under standard laboratory conditions, is added such that there is 1 litre of liquor per 4kg of jute in 16 litres of water.

After a 20-30 minute period of digestion, the raw material, now in the form of pulp, is fed into a series of washers which separate off excess liquid and remove impurities.

The pulp then undergoes defibration, in which the material is refined and the fibers split into fibrils.

The refined pulp then undergoes an Acid-Base shock treatment. The pulp is neutral after the defibration

step and requires the Acid-Base shock treatment to render the fibrils hard and strong.

Acid-Base shock is carried out for a period of 20 minutes in a 1: 1 ratio of alkaline and acidic liquors which have the following compositions: The alkaline liquor is a 3 molar solution of sodium hydroxide and the acidic liquor is 12ml of a solution excreted from the algae"Gigartina Stellata", cultured under standard laboratory conditions. The alkaline liquor is added first, followed by addition of the acidic liquor, and both are added in quantities such that there is 1 litre of liquor per 5kg of dry weight of cellulose.

Following this first Acid-Base shock step, the pulp passes to the bleaching chest where 1st stage bleaching is carried out. The bleaching liquor comprises: a 6 molar solution of sodium hydroxide containing a 5% injection of chlorine gas and 10ml of a solution excreted from the algae"Gigartina Stellata", cultured under standard laboratory conditions; and is added such that there is 1.5 litres of bleaching liquor to 4kg of dry weight of pulp. The pulp is exposed to the bleaching liquor for a period of from 20 to 30 minutes.

Following bleaching, the material is transferred to washers for mechanical washing, thus removing impurities as well as excess bleaching liquor.

Next the raw material is passed to a second bleaching

stage, carried out under the same operating conditions and with the same bleaching liquor as used in the first stage.

The material then undergoes a second Acid-Base shock treatment, (again under the same conditions as were used for the first treatment) followed by washing to separate any debris material.

Lastly, the material is dried such that the moisture content is reduced to approximately 10% and the resulting, fibrous cellulose bailed and packed for transportation.

A flow diagram outlining the process steps for Example 1 is shown in Figure 1.

A schematic illustration of an apparatus suitable for producing fibrous cellulose from raw jute, in accordance with the invention, is given in Figure 5.

The apparatus comprises 1 a silo of raw jute and a means for conveying the raw jute to 3 a shredder.

Following shredding, the raw material passes through a means for conveying the shredded jute to 5 a dusting unit. When dusting is complete, raw material passes along a means for conveying the shredded, dusted jute to 7 a washer. Following washing, the raw jute passes along a means for conveying the washed jute to 9 a bailing unit. The bails of jute are then conveyed to 13 a digestion mixer, to which digestion liquor is delivered from 11 a digestion tank.

The pulp resulting from digestion theapasses to 14 a washer and on to 15 a defibrator, and then passes to 17 an Acid Base Shock chest. Following the first Acid Base Shock Treatment the material enters 21 a bleach

chest before being conveyed to 19 a washer. The material is then conveyed again to 21 a bleach chest and then on to 23 a further Acid Base Shock chest.

Further washing is then carried out in 25 a washer, before drying in 27 a spinner dryer. The resulting material is then packed in 29 a packing unit, prior to transportation.

Example 2: Production of Dissolving Pulp from jute: Dissolving pulp prepared from jute according to the following process contains alpha-cellulose in a concentration in excess of from 99%.

The first steps in the production of dissolving pulp from jute, are the shredding, dusting, washing and bailing of the raw material.

The digestion, washing and defibration steps are then performed in the same manner described in Example 1 for the production of fibrous cellulose.

The refined pulp then undergoes a 1st Acid-Base shock treatment followed by 1st stage bleaching, again both carried out under the same operating conditions as described in Example 1 for the production of fibrous cellulose.

Next, the material is washed before passing again to the bleaching chest, where it undergoes a further bleaching step under the same operating conditions as used for the first bleaching step. Lastly, the material is washed further to remove any remaining impurities.

A flow diagram outlining the process steps for Example 2 is shown in Figure 2.

Example 3: Production of Microcrystalline cellulose powder from jute: Further to the steps described in Example 2, the resulting dissolving pulp is dried in a spinner such that the moisture content is reduced to approximately 10%.

A pulverising step is now required, after which the material is sorted and classified according to mesh size, as microcrystalline powder cellulose. The particle size of microcrystalline cellulose powder is in the range of from 50 to 500pm.

Lastly, the pulverised product is packed ready for transportation.

A flow diagram outlining the process steps for Example 3 is shown in Figure 3.

Example 4: Production of Liquid Cellulose from jute: Liquid cellulose may contain alpha-cellulose in a concentration in excess of 99%, when produced by the following method: The first steps in the production of liquid cellulose are the shredding, dusting, washing and bailing of the raw material.

The digestion and washing steps are then performed in

under the same operating conditions as those described in Examples 1,2 and 3.

There are no defibration or Acid-Base Shock treatments required for the production of liquid cellulose, unlike in the cases of fibrous cellulose, dissolving pulp and microcrystalline cellulose powder.

Following digestion and washing, the material is conveyed directly to a 1st bleaching stage, (using the same bleaching liquor as that used in Example 1).

Next, the feed material enters a bleaching mixer fitted with a heater, for 2nd stage bleaching. On combining the pulp with the same bleaching liquor as used in 1st stage bleaching, the contents of the mixer are heated to a temperature of 700C for a period of 10-15 minutes. In this way, the cellulose pulp is converted to liquid cellulose.

Prior to packing of the liquid cellulose in bottles, it passes through a filter medium to separate off any solid residue remaining. The solid residue obtained is recycled to the 2nd bleaching mixer.

A flow diagram outlining the process steps for Example 4 is shown in Figure 4.

Claims

CLAIMS: 1. A process for the extraction of cellulose from a cellulose-containing material, the process comprising: providing a raw material comprising or consisting of cellulose; forming a mixture comprising the raw material and water; adding a digestion liquor, said digestion liquor comprising an algae excretion, a polysaccharide and an oxidising agent; whereby cellulose is extracted from the raw material to form a material comprising or consisting of pulp.
2. A process as claimed in claim 1, wherein the digestion liquor comprises an algae excretion and a polysaccharide in a chlorinated solution.
3. A process as claimed in claim 1 or claim 2, wherein the digestion liquor includes NaOCl.
4. A process as claimed in any one of the preceding claims, wherein the formation of the digestion liquor involves dissolving a polysaccharide, preferably cellulose, in an alkaline solution, preferably sodium hydroxide, said alkaline solution being chlorinated either before, after or at the time of the addition of cellulose.
5. A process as claimed in any one of the preceding claims, wherein the cellulose extracted from the raw material is in the form of pulp containing at least 65% of alpha-cellulose.

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6. A process as claimed in any one of the preceding claims, wherein the digestion liquor comprises: 6 to 30 g of powdered cellulose; 5 to 25 ml of a solution excreted from the algae "Gigartina Stellata"cultured under standard laboratory conditions; and a chlorinated NaOH solution, in which chlorination is achieved by injecting 2 to 6% chlorine (Cis) gas, the concentration of chlorine being established by titration.
7. A process as claimed in any one of the preceding claims, wherein the mixture is allowed to digest at room temperature, preferably for a period of time of from 5 to 120 minutes.
8. A process as claimed in any one of claims 1 to 5, wherein the digestion liquor comprises: 100 ml of from 1.5 to 4 molar (preferably approximately 2.5 molar) NaOH ; an injection of from 2 to 6 % (preferably approximately 4%) chlorine gas, the chlorine concentration being established by titration; from 7 to 17 g (preferably approximately 12 g) of powdered cellulose; and from 5 to 15 ml (preferably approximately 10 ml) of a solution excreted from the algae"Gigartina Stellata", cultured under standard laboratory conditions.
9. A process as claimed in any one of claims 1 to 5 and 8, wherein the mixture is allowed to digest at room temperature for a period of time of from 20 to 30 minutes.

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10. A process as claimed in any one of the preceding claims, wherein the digestion liquor is added in a volume such that there is 1 litre of liquor per 4 kg of raw material in 16 litres of water.
11. A process as claimed in any one of the preceding claims, further comprising the step of washing the pulp with water.
12. A process as claimed in any one of the preceding claims, further comprising the step of defibration.
13. A process as claimed in any one of the preceding claims, further comprising the step of an acid-base shock treatment of the pulp.
14. A process as claimed in claim 13, wherein the acid-base shock treatment comprises: adding an alkaline liquor comprising a 2 to 4 molar (preferably approximately 3 molar) solution of sodium hydroxide (NaOH); adding an acidic liquor comprising from 10 to 15 ml (preferably approximately 12 ml) of an acidic solution excreted from the algae"Gigartina Stellata", cultured under standard laboratory conditions; exposing the pulp to the mixture resulting from the alkaline and acidic liquors for a period of from 10 to 30 minutes, more preferably from 15 to 25 minutes, still more preferably approximately 20 minutes.
15. A process as claimed in claim 14, wherein the alkaline and acidic liquors are added in a volume such that there is approximately 1 litre of liquor per 5 kg of dry weight of cellulose.

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16. A process as claimed in any one of the preceding claims, further comprising the step of bleaching of the pulp by the addition of a bleaching liquor.
17. A process as claimed in claim 16, wherein the bleaching liquor comprises: a from 5 to 7 molar (preferably approximately 6 molar) solution of sodium hydroxide (NaOH); an injection of from 1 to 10 % (preferably 5%) chlorine gas, the chlorine concentration being established by titration; and 5 to 15 ml (preferably 10ml) of a solution excreted from the algae "Gigartina Stellata", cultured under standard laboratory conditions.
18. A process as claimed in claim 16 or claim 17, wherein the pulp is exposed to the bleaching liquor for a period of from 20 to 30 minutes.
19. A process as claimed in any one of claims 16 to 18, wherein the bleaching liquor is added such that there are approximately 1.5 litres of liquor per 4 kg dry weight of pulp.
20. A process as claimed in any one of claims 16 to 19, further comprising the step of washing the pulp with water.
21. A process as claimed in claim 20, further comprising the step of bleaching the pulp, preferably using the conditions defined in any one of claims 17 to 19.

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22. A process as claimed in any one of claims 16 to 21, comprising a further acid-base shock treatment of the pulp, preferably using the conditions defined in claim 14 or claim 15.
23. A process as claimed in claim 22, comprising a further step of washing the pulp with water.
24. A process as claimed in any one of the preceding claims, further comprising the step of drying the pulp.
25. A process as claimed in any one of claims 1 to 15, further comprising the step of bleaching the pulp, preferably using the conditions defined in any one of claims 17 to 19.
26. A process as claimed in claim 25, further comprising the step of washing the pulp with water.
27. A process as claimed in claim 26, further comprising a further bleaching of the pulp, using the conditions defined in any one of claims 17 to 19.
28. A process as claimed in claim 27, further comprising the step of washing the pulp with water.
29. A process as claimed in claim 28, further comprising the step of drying the pulp.
30. A process as claimed in claim 29, further comprising the step of pulverizing the dried material.
31. A process as claimed in claim 30, further comprising the step of sieving the pulverized, dried material.

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32. A process as claimed in any one of claims 1 to 11, further comprising the step of bleaching the pulp, preferably using the conditions defined in any one of claims 17 to 19.
33. A process as claimed in claim 32, wherein the step of bleaching involves heating, preferably to a temperature of from 60 to 80 C (more preferably 70OC) for a period preferably of from 5 to 20 minutes (more preferably 10 to 15 minutes).
34. A process as claimed in claim 32 or claim 33, further comprising the step of filtering the pulp.
35. A process as claimed in any one of the preceding claims, wherein the raw material is provided in a shredded form.
36. A process as claimed in any one of the preceding claims, wherein the raw material is provided after having being passed through a dusting and/or washing unit.
37. A process as claimed in any one of the preceding claims, wherein the raw material is provided after having been compacted into bails.
38. A process as claimed in any one of the preceding claims, wherein the raw material provided comprises or consists of jute and/or cotton.
39. A fibrous cellulose containing material whenever produced by a process as defined in any one of claims 1 to 24.
40. A dissolving pulp containing material whenever

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produced by a process as defined in any one of claims 25 to 28.
41. A microcrystalline cellulose powder containing material whenever produced by a process as defined in any one of claims 29 to 31.
42. A liquid cellulose containing material whenever produced by a process as defined in any one of claims 32 to 34.
43. Premier quality unbleached pulp whenever produced by a process as defined in any one of claims 1 to 12.
44. Premier grade bleached pulp whenever produced by a process as defined in any one of claims 1 to 21.
45. A digestion liquor for use in a process for the extraction of cellulose from a cellulose-containing material, the liquor comprising: 6 to 30 g of powdered cellulose; 5 to 25 ml of a solution excreted from the algae "Gigartina Stellata"cultured under standard laboratory conditions ; and a chlorinated NaOH solution, in which chlorination is achieved by injecting 2 to 6% chlorine (C12) gas, the concentration of chlorine being established by titration.
46. A bleaching liquor for use in a process for the extraction of cellulose from a cellulose-containing material, the liquor comprising: 5 to 7 molar (preferably 6 molar) solution of sodium hydroxide (NaOH); an injection of from 1 to 10 % (preferably 5%) chlorine gas, the chlorine concentration being

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established by titration ; and 5 to 15 ml (preferably 10ml) of a solution excreted from the algae"Gigartina Stellata", cultured under standard laboratory conditions.
47. A laquer comprising a material as defined in any one of claims 39 to 42.
48. Carboxymethylcellulose whenever formed from a material as defined in any one of claims 39 to 42.
49. Melamine, cellophane or viscose comprising or whenever formed from a material as defined in any one of claims 39 to 42.
50. Craft paper, liner board, cement bag paper, medium density board, hard board or file board comprising or whenever formed from a material as defined in any one of claims 39 to 42.
51. Writing paper, printing paper, duplex board, bleached board and file card comprising or whenever formed from a material as defined in any one of claims 39 to 42.