DESC:Field of the Invention
[001] The present invention relates to production of absorbent fibres. Particularly, the present invention relates to a process for producing absorbent fibres from non-wood lignocellulosic biomass.
Background of the Invention
[002] Fluff pulp is primarily produced from long and coarse fibres of softwood species and used for speciality applications. The major production of fluff pulp currently is shared by Southern and Northern US. The demand of fluff pulp is continuously increasing due to increasing world population. In 2022, fluff pulp production capacity is estimated at around 8.0 million (air dried) tonnes. The fluff pulp has wide range of applicability in manufacturing the hygiene products, including the large global diaper/nappies, feminine hygiene, and adult incontinence markets, as well as nonwovens. This sector consumes highest fluff pulp due to its high absorption and retentive quality. The data reported that, in 2017, global fluff pulp consumption was 5.8 million air-dried tonnes which increased by 3.8%in 2022. The global annual growth rate of 4.1% has been expected till 2023.
[003] Southern soft wood pines (with long and coarse fibres) remains the primary tree species to produce fluff pulp along with South American eucalyptus tree species (with short and thin fibres). Fluff pulp is typically produced in sheet form or roll form by using conventional pulping methods. These fluff pulp sheets are then fed into a hammermill to separate individual fibres from the pulp sheet through a process called “Defiberization”. The individualized fibres are “air laid” on a moving conveyer belt to form a porous fibre network which makes the absorbent core of an absorbent hygiene product such as sanitary pad, diaper, pet pad, fruit pad, air-laid paper, etc.
[004] The increased demand of softwood and hardwood to produce fluff pulp may lead to the destruction of forest resources which can directly impact with biodiversity, global environmental quality, and climate.
[005] Further, the conversion of wood into absorptive fibre requires a multistep process based on harsh mechanical and chemical treatments, which results into generation of huge amount of wastewater. Moreover, the chemical-based treatments are energy and water intensive which can make the production of fluff pulp unsustainable. This pushes the demand for establishing an eco-friendly, cost effective and sustainable process to produce absorbent and retentive pulp.
[006] In the developing world, the agricultural residue is an abundant source of lignocellulosic raw materials for various applications. To get rid of this huge amount of agriculture residue farmers often burn these residues in open field. This results in the release of greenhouse gases and loss of beneficial micro flora which is presents in topmost layer of soil. So, by converting this waste into valuable raw material in highly absorbent matrix/fibre is an eco-friendly approach for waste management. This biomass contains significant amounts of cellulose, hemicelluloses and lesser amount of lignin as compared to forest based raw material.
[007] Sugarcane bagasse is a by-product of sugar industry and one of the world’s most abundantly available lignocellulose agricultural residues. Bagasse has also been widely used in pulp and paper making industry. Bagasse is a tree-free, sustainable, cost-effective, high performing and truly circular alternative source of fluff pulp. In India, around 400 million tons of sugarcane is produced every year. Sugar factories typically generate around 250 to 300 kg of bagasse per metric ton of sugarcane, resulting in over 100 million tons of inexpensive and readily available source of renewable lignocellulose biomass.
[008] In terms of chemical composition, sugarcane bagasse contains around 40-45% cellulose, 25-30% hemicellulose, 20-25% lignin and 2-4% ash content. With average fibre length of round 1.6 mm (varying from 0.5 mm to 3.9 mm), average fibre diameter of around 19-20 micrometre (µm) and cell wall thickness of around 6-7 micrometres (µm), bagasse fibres can offer multiple advantages.
[009] There are several conventional processes that utilize the lignocellulosic biomass to produce absorbent fibres. JP55104649 discloses a method of preparation of adsorbing material from bagasse by steaming the bagasse with a liquid containing sodium sulfate and sulphur dioxide, wherein fibres are unravelled, the bagasse is crushed, and the adsorbing material is manufactured. The limitation of this method is that the absorbent pulp obtained has low strength, which would result in dust formation during dry defiberization in a hammermill. This process does not address removal of ash or silica. The pulping method mentioned in this process uses harsh chemical treatment which can be harmful for the environment as the chemical recovery is difficult.
[010] US2015259709A1 discloses a process for producing fluff pulp and ethanol from sugarcane bagasse or straw, comprising: fractionating the feedstock in the presence of an acid catalyst, a solvent for lignin, and water to generate a solid/liquid slurry comprising cellulose-rich solids, hemicelluloses, and lignin; separating the solid/liquid slurry into a solid stream and a liquid stream; further treating the cellulose-rich solids to produce fluff pulp; hydrolysing the hemicelluloses to generate hemicellulose monomers; and fermenting at least a portion of the hemicellulose monomers to cellulosic ethanol. This method suffers from the disadvantages such as the requirement of high energy and provides low pulp yield, thus results in significantly high cost of pulp production. The absorbent pulp obtained has low strength, which would result in dust formation during dry defiberization in a hammermill. This process does not address removal of ash or silica.
[011] Rekha V. et al (Bhanu Rekha V, Ramachandralu K, Rasigha T in their article “Enhancing the Absorbency of Bagasse through Enzymatic Delignification” (2013). J Fashion Technol Textile Eng 1:1) suggests the suitability of the bagasse fibres to be used for the absorbent hygiene products were improved by enzymatic delignification process, which is the removal of the structural polymer lignin from plant tissue by using laccase enzyme (Bactosal LAC powder) to increase the absorbency of the fiber, which is the main requirement for sanitary napkins. The suggested approach has several shortcoming such as it results in lignin rich pulp with 11.68% lignin content in the pulp which negatively impacts the absorbency of the pulp. This process does not address removal of ash or silica. Therefore, the absorbent pulp would result in dust formation during dry defiberization in a hammermill. Since this process results in high lignin content of 11.68%, it will require harsh bleaching treatment which can impact the quality of the fibres as well as the process would be harmful for the environment.
[012] Conventionally, the bagasse has very high ash content of around 2–4% and 1-1.25% silica content the same being significantly higher than other wood-based fibres. Due to the high ash content, and silica content, use of bagasse to obtain individualized fibres that can be used in absorbent hygiene product results in a number of challenges. For example, high amount of silica in bagasse affects the chemical recovery process during pulp production and causes abrasion in hammermill blade during defiberization reducing the lifespan of the device parts. Besides, very high fiber damage occurs during dry defiberization due to higher burst factor and high amount of dust is formed and average mean length is less.
[013] The known methods so far do not address the challenges due to high ash and silica contents, which render the bagasse fibres unsuitable for absorbent hygiene products.
[014] In view thereof, there is an unmet need to provide process of producing absorbent fibres from non-wood lignocellulosic biomass that can overcome one or more disadvantages of known methods such as avoid use of strong and toxic chemical pre-treatment, provide satisfactory reduction is ash and silica content in the absorbent fibres produced, provide fibers with improved characteristics suitable for making absorbent hygiene products, and easily compostable.
OBJECTS OF THE INVENTION
[015] It is an object of the present invention to provide a process for producing absorbent fibers from non-wood lignocellulosic biomass.
[016] It is one object of the present invention to provide a process for producing absorbent fibers comprising enzymatic treatments at various stages and mild mechanical and chemical treatments.
[017] It is another object of the present invention to provide a process for producing absorbent fibers with reduced ash and silica content.

SUMMARY OF THE INVENTION
[018] In a general aspect of the present invention there is provided a process for producing absorbent fibers that obviates one or more disadvantages of methods known hereto in the art by avoiding need for excessive toxic and harsh chemical treatment, use of chlorine-based chemicals amongst others.
[019] In an aspect, the present invention provides a process for producing absorbent fibers from non-wood lignocellulosic biomass.
[020] In an aspect, the present invention provides a process for producing absorbent fibers from non-wood lignocellulosic biomass, wherein the process comprises combination of enzymatic treatments and gentle pulping by chemithermomechanical also known as CTMP pulping steps.
[021] In one aspect, the present invention provides a process for producing absorbent fibers from non-wood lignocellulosic biomass comprising:
(i) providing a depithed non-wood lignocellulosic biomass by subjecting a non-wood lignocellulosic biomass material to a depithing;
(ii) subjecting said depithed non-wood lignocellulosic biomass to an enzyme treatment-1 for 30 minutes to 240 minutes at 30°C- 60°C;
(iii) subjecting the pulp after enzyme treatment-1 to mechanical pulping and separating into a pulp fraction comprising cellulose and hemicellulose, and a lignin fraction;
(iv) subjecting the pulp comprising cellulose and hemicellulose obtained after mechanical pulping to a chemical treatment;
(v) subjecting the pulp in step (iii) to an enzyme treatment-2 for30 minutes to 240 minutes at 30°C- 60°C;
(vi) subjecting the pulp after enzyme treatment-2 to a bleaching treatment;
(vii) subjecting the bleached pulp to an enzyme treatment-3 to obtain a pulp with reduced ash and silica content;
(viii) dewatering and drying the pulp of step (vii);
(ix) defibering the dry pulp at 3000 rpm to 6000 rpm to produce absorbent fibers.
[022] The absorbent fibers obtained can be used in making air laid, fruit pad, pet pad, adult diaper, under pad, pads for urinary incontinence, sanitary pads, hygiene products amongst others.

BRIEF DESCRIPTION OF DRAWING
[023] Figure 1 depicts a flow chart of the process in accordance with one of the exemplary embodiment of the present invention for producing absorbent fibers from non-wood lignocellulosic biomass.

DETAILED DESCRIPTION OF INVENTION
[024] While the disclosed subject matter is amenable to various modifications and alternative forms, specific embodiments are described herein in detail. The intention, however, is not to limit the disclosure to the particular embodiments described. On the contrary, the disclosure is intended to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure as defined by the appended claims.
[025] Similarly, although illustrative processes or methods may be described herein, the description of the same should not be interpreted as implying any requirement of, or particular order among or between, the various steps disclosed herein. However, certain embodiments may require certain steps and/or certain orders between certain steps, as may be explicitly described herein and/or as may be understood from the nature of the steps themselves (e.g., the performance of some steps may depend on the outcome of a previous step).
[026] Unless defined otherwise, all technical and scientific terms used herein shall have their same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.
[027] In this specification and in the claims that follow, reference will be made to a number of terms that shall be defined to have the following meanings.
[028] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a,” '‘an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.
[029] The present invention relates to a process for producing absorbent fibers from agriculture waste material. The present invention provides a process for producing highly absorbent fibers from non-wood lignocellulosic biomass.
[030] In an embodiment, the present invention provides a process for producing absorbent fibers from agricultural waste residue.
[031] In one embodiment, the present invention provides a process for producing absorbent fibers from non-wood lignocellulosic biomass.
[032] In one embodiment, the present invention provides a process for producing absorbent fibers from non-wood lignocellulosic biomass comprising:
(i) providing a depithed non-wood lignocellulosic biomass by subjecting a non-wood lignocellulosic biomass material to a depithing;
(ii) subjecting said depithed non-wood lignocellulosic biomass to an enzyme treatment-1 for 30 minutes to 240 minutes at 30°C- 60°C;
(iii) subjecting the pulp after enzyme treatment-1 to mechanical pulping and separating into a pulp fraction comprising cellulose and hemicellulose, and a lignin fraction;
(iv) subjecting the pulp comprising cellulose and hemicellulose obtained after mechanical pulping to a chemical treatment;
(v) subjecting the pulp in step (iii) to an enzyme treatment-2 for 30 minutes to 240 minutes at 30°C- 60°C;
(vi) subjecting the pulp after enzyme treatment-2 to a bleaching treatment;
(vii) subjecting the bleached pulp to an enzyme treatment-3 to obtain a pulp with reduced ash and silica content;
(viii) dewatering and drying the pulp of step (vii);
(ix) defibering the dry pulp at 3000 rpm to 6000 rpm to produce absorbent fibers.
[033] The process of present invention utilizes the combination of enzymatic treatment and gentle pulping (chemithermomechanical, also known as CTMP pulping) for desilication and delignification of non – wood lignocellulosic raw material followed. CTMP process is used to minimize the use of harsh chemical that is used in conventional chemical pulping. The gentle pulping process can also involve mild chemical post-treatment of the fibre obtained from mechanical pulping for improving the swelling capacity of fibre for enhanced absorbency. The cellulose, hemicellulose and lignin present in these non-wood lignocellulosic materials can be in an amount of 40 to 70%, 17 to 35% and 10 to 20 % respectively.
[034] In an embodiment, the non-wood lignocellulosic biomass can be selected from waste resides selected from sugarcane bagasse, straw wastes, corn wastes, spent grains, banana fiber, bast fiber such as flax, hemp, jute, kenaf, ramie and alike.
[035] In one preferred embodiment, the non-wood lignocellulosic biomass is sugarcane bagasse.
[036] The raw bagasse typically contains significant amount of pith, which is made of fine, thin walled cellulosic cells. One of the major barriers in utilizing the bagasse for production of absorbent pulp is large amount of pith in it. This pith is generally non-fibrous in nature, which also affects the absorbency of the fibre. If bagasse is processed without removing the pith, it can adversely affect the final quality of fluff pulp. The pith can be crushed and generate fines during mechanical treatment. Crushed pith can also create dust during dry defiberization process. Thus, depithing helps to remove these undesirable cells and obtain high quality, clean bagasse fibers.
[037] In certain embodiment, in the process of the present invention, in step (i) the non-wood lignocellulosic biomass is subjected to a depithing. The depithing can be carried out in dry or wet condition.
[038] In one embodiment, the pith can be removed by drying the bagasse and applying mechanical treatment to separate pith from bagasse fibers.
[039] In one embodiment, the depithed non-wood lignocellulosic biomass of step (i), can be obtained by subjecting the selected non-wood lignocellulosic biomass to depithing by drying the bagasse and subjecting the dried bagasse to a mechanical treatment, separating the pith from bagasse fibers. During wet depithing, moist raw bagasse is mixed with water to form a slurry of 4-5% consistency. This slurry is uniformly mixed and is passed through mechanical action which separates the loosely attached pith from the bagasse fibers. The slurry then goes through a screen with 20 mesh to obtain depithed bagasse fiber.
[040] The depithed non-wood lignocellulosic material can be pre-treated to reduce the silica content. The non-wood lignocellulosic material such as bagasse can be pre-treated by washing with water at a temperature of about 40°C- 60°C or acidic water or a combination thereof. The pH of water can be 2 to 6. The pre-treatment can be repeated to reduce as much silica as possible during the pre-treatment stage. The pre-treatment also prepares the fibre for the next stage of the pulping process where further silica is removed.
[041] In one embodiment, the bagasse is pretreated by washing with water at a temperature ranging from about 30°C- 80°C.
[042] The process of the present invention comprises multiple enzyme treatments namely enzyme treatment-1, enzyme treatment-2, and enzyme treatment-3. The enzyme treatments in accordance with the present invention comprises treating the non-wood lignocellulosic fibre pulp such as bagasse with an enzyme or combination of enzymes.
[043] The concentration of enzyme or mixture of enzyme can be 0.15 to 2 % by weight of the pulp to be treated with enzyme. The pulp consistency can be of 5 to 15%. The enzyme treatment can be carried out for 30 min to 240 min, preferably for 30 min to 120 min. The temperature for enzyme treatment can be 30°C- 60°C, preferably 40°C- 60°C.The ratio of enzyme to pulp may vary from 1:5 to 1:10. The enzyme treatment can be given at pH 3 to 8 preferably at pH 5 to 7.
[044] In one embodiment, the non-wood lignocellulosic fibres such as bagasse is processed after depithing and pre-treatment steps. The presence of pith may affect the pulping process, which may suppress the action of enzymes.
[045] The enzymes used for the enzyme treatment is selected from cellulase, endoglucanase, xylanase, laccase, pectinase, polygalacturonase, silicase, or mixtures thereof.
[046] In one embodiment, the enzyme silicase used belongs to the class of carbonic anhydrases.
[047] In one embodiment, a mixture of enzymes comprising two or more of enzyme selected from cellulase, endoglucanase, xylanase, laccase, pectinase, polygalacturonase, and silicase is used.
[048] In certain embodiments, the mixture of enzyme comprises 0.1-10% of cellulase, 0.2-8% of xylanase, 0.1-10% of pectinase, 0.1-10% of polygalacturonase, 0.1-15% silicase and/or 0.1-5% of laccase.
[049] In certain embodiment, a solution of the enzyme mixture is used. The enzyme mixture solution is prepared by adding 0.1-10% of cellulase, 0.2-8% of xylanase, 0.1-10% of pectinase, 0.1-10% of polygalacturonase, 0.1-15% silicase and/or 0.1-5% of laccase in distilled water and mixing.
[050] In certain embodiments, the mixture of enzyme comprises 0.1-5% of cellulase, 0.2-4% of xylanase, 0.1-5% of pectinase, 0.1-5% of polygalacturonase, 0.1-5% silicase and/or 0.1-5% of laccase.
[051] In certain embodiments, the mixture of enzyme comprises 0.1-1% of cellulase, 0.2-1% of xylanase, 0.1-2.5% of pectinase, 0.1-2.5% of polygalacturonase, 0.1-1% silicase and/or 0.1-1% of laccase.
[052] Without bound by any theory, the enzyme treatment in accordance with the present invention is found to reduce the amorphous silica present (silica content) in the lignocellulosic material. The enzyme treatment aids in degrading the non-fibrous component of the fiber cell wall resulting in enhanced absorption of the resultant pulp.
[053] In one embodiment, in step (ii), the process comprises subjecting the depithed non-wood lignocellulosic biomass to an enzyme treatment-1 for 30 minutes to 240 minutes at 30°C- 60°C at a pH of 5-7 with enzyme dose of be 0.15 to 2 % by weight,
[054] The enzyme treated pulp obtained in step (ii) is subjected to mild mechanical treatment for pulping in step (iii).
[055] The mechanical pulping of the enzyme treated fiber can be carried out with a tool selected from a disc refiner, valley beater, blender, single disc refiner, double disc refiner or alike.Preferably, the enzyme treated fiber can be passed through refiner at about 1500 to 1800 rpm.
[056] In certain embodiment, the enzyme treated fiber can be passed through a single pass in a disk refiner at 1500 rpm to 1800 rpm with the plate gap ranging 0.07 mm to 0.7 mm so that Canadian Standard Freeness (CSF) value is between 600 ml to 800 ml.
[057] Without bound by any theory it is believed that the mild mechanical pulping open ups the fiber for better penetration of chemicals enabling the mild chemical treatment to be applied at a lower temperature with low chemical dosage.
[058] The mechanically processed enzyme treated pulp obtained in step (iii) is subjected to a mild chemical treatment in step (iv).
[059] The mild chemical treatment can be carried out for about 10 to 180 minutes, preferably 30 minutes to 180 minutes.
[060] The temperature of the pulp during the chemical treatment can range from 60°C- 180°C, preferably 80°C- 170°C.
[061] The concentration of chemical used can range from 1 to 18%. The ratio of chemical to pulp can be 1:2 to 1:10.
[062] The chemical for the chemical treatment can selected from NaOH, Kraft (solution of sodium hydroxide (NaOH), and sodium sulfide (Na2S)), or sulphite (solutions of sulfite and bisulfite ions).
[063] The concentration of the chemical for the chemical treatment of the pulp in step (iv) is from 10% to 20%.
[064] In a certain embodiment, post the mild chemical treatment, optionally an additional mild mechanical treatment for pulping can be performed on the pulp obtained in step (v), to further open the fibers and to improve the swelling capacity of fiber for enhanced absorbency. Preferably, the treated pulp can be passed through a double disk refiner at 1500 rpm to 1800 rpm with plate gap between 0.07 mm to 0.7 mm so that the Canadian Standard Freeness (CSF) value is between 550 ml to 750 ml.
[065] The pulp obtained after the mild chemical treatment or the pulp after the mild chemical treatment followed by mild mechanical treatment is subjected to an enzyme treatment-2 in accordance with the present invention.
[066] In one embodiment, in step (v), the process comprises subjecting the pulp obtained in previous step to an enzyme treatment-2 for 30 minutes to 240 minutes at 30°C- 60°C at a pH of 5-7 with enzyme dose of be 0.15 to 2 % by weight and at a pulp consistency of 5 to 15%.
[067] For the enzyme treatment can be carried out using a single or a combination of enzymes selected from pectinase, polygalacturonase, xylanase, cellulase, endoglucanase, amylase and silicase to further reduce silica content.
[068] The pulp obtained in step (v) after chemical treatment is subjected to bleaching treatment in step (vi) to obtain a pulp with reduced ash and silica content.
[069] The bleaching treatment comprises bleaching the pulp obtained after enzyme treatment-2 by Elemental Chlorine Free (ECF) bleaching or Totally Chlorine Free (TCF) bleaching process.
[070] In an embodiment, the bleaching is carried out in presence of a chelating agent along with the bleaching agent.
[071] The bleaching agent in an embodiment is hydrogen peroxide.
[072] The chelating agent in an embodiment can be selected from but not limiting to ethylenediaminetetraacetic acid (EDTA), magnesium sulfate (MgSO)4, diethylenetriamine penta(methylene phosphonic acid) (DTPMPA), and diethylenetriamine pentaacetate (DTPA).
[073] One or more of the ECF and TCF bleaching sequence is applied to enhance brightness of the pulp.
[074] Without bound by any theory, it is believed that the pre- and post- enzyme treatments expose pulp for better chemical and enzymatic penetration, which collectively reduces the overall silica content and amount of dust formation and fines generation during later defiberization process. Further, the integrity and the strength of the cellulose fiber in the pulp is maintained as the weak cellulose fibers results in dust and fines formation during the late defiberization stage. Moreover, the gentle belching in accordance with the present invention is not only environment friendly, but also result in lower effluent that needs to be treated at wastewater treatment plant.
[075] The bleached pulp of step (vi) is subjected to enzyme treatment-3 (step (vii)) before dewatering and drying.
[076] In one embodiment, in step (vii), the process comprises subjecting the pulp obtained in previous step (vi) to an enzyme treatment-3 for 30 minutes to 240 minutes at 30°C- 60°C at a pH of 5-7 with enzyme dose of be 0.15 to 2 % by weight and at a pulp consistency of 5 to 15%.
[077] In an embodiment, in step (viii) for dewatering, the pulp obtained in step (vii) can be passed preferably through a wired screen and pressed. Such dewatering cycles are repeated to remove the maximum possible water from the pulp. The dewatered pulp with reduced moisture and water content is dried either at room temperature or with hot air at 90°C to 210°C. Gentle dewatering and gentle drying cycles are repeated to transform the pulp into a pulp sheet. Such dewatering and drying process enhances the optimal fiber to fiber bonding. The fibers can further be individualized during defibration stage to form a highly porous fiber matrix for improved absorption and retention properties and result in less fines generation and dust formation during dry defiberization process.
[078] A sheet of desired dimensions, for example a sheet of 12” by 12” is formed with 300 to 600 GSM basis weight using a suitable tool for example a hand sheet former.
[079] The dried pulp sheet obtained in step (viii)is subjected to defiberization in step (ix). The dried pulp sheet is defiberized using an appropriate means for example, a lab hammer mill.
[080] The defiberization of the pulp obtained in step (viii) is carried out between 3000 rpm to 6000 rpm in a hammermill. Further, the defiberization is carried out with blade gaps between 0.2 mm to 1.2 mm, preferably between 0.5 mm to 1 mm. The defiberization helps to reduce generation of fines and knots formation in fibres and improves the amount of “good fiber” that is short to medium fiber as compared to the pine wood (softwood) fibres (long fibres).
[081] An optimal defiberization can be achieved by adjusting the blade gap between hammers and breaker bar.
[082] In certain embodiment bagasse fluff pulp in step (ix) is obtained by subjecting the 100% bagasse pulp from the previous step to defiberization.
[083] In certain embodiment(s), the bagasse pulp from the previous step is blended with soft wood or hard wood pulp during defiberization to vary the performance of rewet, fluid distribution and obtain thinner products. Further, mixing of non-wood lignocellulosic fluff pulp (short fibers obtained in accordance with the present invention) with conventional pinewood (long fiber) can offer flexibility of providing different absorption and retention properties that can be tailored for different applications.
[084] In one embodiment the process of the present invention provides shorter bagasse fibers with thinner cell walls resulting in smaller void spaces between fibers, thereby effectively holds the fluid, resulting in improved fluid retention. The denser core formation improves capillary action between fibers by imparting increased wicking which allows more pad area to be utilized.
[085] The process of the present invention provides absorbent fibers with an average fiber length ranging from 1.4 to 1.7 mm.
[086] The process of the present invention significantly reduces the ash and silica content of the absorption fibres.
[087] The burst factor of the absorbent fiber obtained through the present process is in the range of 1.41 kpa m2/g to 0.9 kpa m2/g, with the absorption capacity ranging from 9 g/g to 10g/g and absorption time ranging from 2.5 s/3g to 5 s/3g.
[088] The reduced burst factor indicates that optimal fiber-to-fiber bonding is achieved aiding in proper individualization of fibers during dry defibration stage to form a highly porous fiber matrix for better absorption and retention properties and result in less fines generation and dust formation. Low burst factor means that less energy is required to individualize the fibers.
[089] The process of the present invention provides absorption fibres with average mean length of fiber improved compared to conventional pulp since less fiber damaged occurs during dry defiberization due to lower burst factor and less dust formation while simultaneously ensuring that the pulp also has high hemicellulose content.
[090] The water Retention value of the fluff pulp obtained by the process of the present invention is the higher compared to the conventional softwood fluff pulp as well as hardwood fluff pulp. Besides, the absorption capacity of the fluff pulp of the present invention is increased as compared to the conventional softwood and hardwood fluff pulp and the absorption time is decreased. Thus, the process of the present invention provides the absorption fibres with significantly improved overall characteristics.
[091] The process of the present invention uses as a starting material, agricultural waste residue, which is otherwise burnt causing sever pollution. Thus, the process of the present invention is sustainable, economical and environment friendly.
[092] The process of the present invention produces absorbent fibers with substantially high absorbency and water retention capacity for various applications like producing thin compressed fibers which can help reduce packaging, storage and transportation costs, personal hygiene products like diapers and sanitary pads or the like, air laid, fruit pad, pet pad, under pad, urinary incontinence pad amongst others.
[093] The process of the present invention for producing absorbent fibers therefore obviates one or more disadvantages existing in the art.

EXAMPLES
[094] The invention is further illustrated herein by mean of examples. The following examples are given by way of illustration only and therefore should not be constructed to limit the scope of the present invention.

Abbreviation:
[095] Exp = Experiment

Testing Methods:
[096] The following testing methods were employed to determine various characteristics features of the pulp and fibres.

(i) Ash and silica content:
[097] The Ash content was determined by combustion of the sample material in a muffle furnace at 525 °C as per the TAPPI test method T 211 om-93. Ash content present at 525 °C is calculated in percentage on a moisture-free sample basis.
[098] The Silica content was determined by the TAPPI (T-244) & HF treatment method. The ashed material was treated with HCl to decompose silicates and dissolved silica forming silicic acid that is precipitated as partially dehydrated silica during evaporation and baking. Silica was dehydrated at 525 °C for 2 h and weighed. Dehydrated silica was then treated with hydrofluoric acid (HF) and kept at 800 °C for 1 h. Silica is volatilized as silicon tetrafluoride leaving non-volatile residue as “other inorganic material (O In O).” The residue was weighed, and silica was determined as loss on volatilization.
(ii) Water Retention Value (WRV):
[099] The Water Retention Value (WRV) test was performed using SCAN-C 62:00 (Pulps – Determination of WRV). In this method (SCAN-C 62:00 (Pulps – Determination of WRV), 1 g of pulp was disintegrated to make 1 percent pulp slurry. The pulp slurry was allowed to settle for 2 hours so that the pulp has time to swell and absorb as much water as possible. After 2 hours, the pulp was filtered through a gouch crucible. The filtered pulp was centrifuged at 3000 rpm for 30 min. After centrifuge, the pulp was weighed, which indicates that amount of water that the pulp can retain after the centrifuge. The pulp was then dried in oven overnight to remove complete the moisture completely. The weight of the oven dried pulp was measured to obtain the WRV.
(iii) GSM Weight:
[100] The GSM of pulp sheet was determined by the specific standard method by ISO 536. The area of the pulp sheet was calculated by multiplying the length and the width of the pulp sheet. The mass of the pulp sheet was determined by weighing the pulp sheet with a defined area. The GSM of the pulp sheet was calculated by dividing the weight of pulp sheet by the respective area of the pulp sheet.
(iv) Moisture Content:
[101] The moisture content of the pulp sheet was determined by heating 3g to 4g samples for about 2h at 105 ± 2 °C in an oven. Moisture content of samples was calculated as the percentage loss of the original weight of the specimen as per the TAPPI test method T 412 om-94.
(v) Absorption time and capacity:
[102] The absorption time and capacity was calculated by making the pad according to standard method SCAN-C 33:80. In this method 3.0 g of defiberized pulp was placed at an inlet tube of specific volume tester under continuous suction of air which sucks the fibers to form a circular pad with a diameter of 50 mm. The apparatus was connected to a vacuum line maintaining a constant air stream, from the inlet to the outlet tube, applying a pressure difference of 0.14 bar. After obtaining the pulp weight to exactly 3.0 g, the pad was subjected to absorption and specific volume tests. Measurement of the absorption time was taken when a constant pressure of 2.5 kPa was applied to the pad. The total absorption capacity was calculated by weighing the wet pad, as the relative increment of the pad mass before and after the pad was soaked in water.
(vi) Burst Factor:
[103] The test absorbent fiber was held between annular clamps and was subjected to an increasing pressure by a rubber diaphragm, which is expanded by hydraulic pressure at a controlled rate, until the test specimen ruptures. The maximum pressure reading up to the rupture point was recorded as the bursting strength.

Examples 1
Depithing of bagasse
[104] Raw bagasse waste (10 kg) was collected from a sugar mill in Surat, Gujarat, dried and cleaned. To the dried and cleaned bagasse, a mechanical treatment was applied to separate the pith from bagasse fibres to obtain of depithed bagasse (8 kg).

Example 2A
Comparative acid treatment of depithed bagasse
[105] 1 kg Depithed bagasse (1 Kg) was washed with warm water (10 ltr) and with individual acids and combination of acids as shown in Table 1 for maximum removal of ash and silica content loosely attached on the surface of the fiber. The individual acids used were sulphuric acid, hydrochloric acid, acetic acid, formic acid, citric acid, and sulphamic acid. The combination of acids used were sulphuric acid, citric acid and formic acid. For certain treatments, 1% acid solution was prepared by adding CH3COOH, HCOOH, citric acid and sulphamic acid separately to water to obtain a solution with pH of 2, 4, and 6 respectively. For some other treatments mixture of 1% acid solution was prepared by adding H2SO4, citric acid, and HCCOH to water to obtain a solution with pH of 2, 4 and 6 respectively. It was observed that applying three or more pre-treatments from the following pre-treatments, in the same order or in different order, could reduce the ash and silica content during the pre-treatment stage.

Table 1: Effect of washing the depithed bagasse with individual 1% acid solution of H2SO4 and HCl on silica and ash content
Parameters Exp-1 Exp-2
(Control) Exp-3 Exp-4 Exp-5 Exp-6 Exp-7 Exp-8
No washing Ambient water washing H2SO4 HCL
pH - - 2 4 6 2 4 6
Temperature 35?C
Ash (%) 2.26 2.06 1.61 1.70 1.81 1.59 1.68 1.78
Silica (%) 1.24 1.11 0.87 0.96 1.02 0.88 0.97 1.04

Table 2: Effect of washing the depithed bagasse with individual 1% acid solution of CH3COOH and HCOOH, on silica and ash content
Parameters Exp-1 Exp-2
(Control) Exp-9 Exp-10 Exp-11 Exp-12 Exp-13 Exp-14
No washing Ambient water washing CH3COOH HCOOH
pH - - 2 4 6 2 4 6
Temperature 35?C
Ash (%) 2.26 2.06 1.63 1.81 1.84 1.58 1.71 1.79
Silica (%) 1.24 1.11 0.89 0.98 1.04 0.86 0.94 0.98

Table 3: Effect of washing the depithed bagasse with mixture of 1% acid solution of citric acid and sulphamic acid, on silica and ash content
Parameters Exp-1 Exp-2
(Control) Exp-15 Exp-16 Exp-17 Exp-18 Exp-19 Exp-20
No washing Ambient water washing Citric acid Sulphamic Acid
pH - - 2 4 6 2 4 6
Temperature 35?C
Ash (%) 2.26 2.06 1.59 1.72 1.84 1.58 1.77 1.88
Silica (%) 1.24 1.11 0.87 0.96 1.02 0.87 0.98 1.03

Table 4: Effect of washing the depithed bagasse with mixture of 1% acid solution comprising H2SO4, citric acid, and HCCOH with pH of 2 at different temperatures, on silica and ash content
Parameters Exp-1 Exp-2
(Control) Exp-21 Exp-22 Exp-23
No washing Ambient water washing H2SO4 + Citric acid + HCCOH
Temperature - - 40 50 60
pH - - 2 2 2
Ash (%) 2.26 2.06 1.62 1.57 1.53
Silica (%) 1.24 1.11 0.89 0.87 0.86

Table 5: Effect of washing the depithed bagasse with mixture of 1% acid solution comprising H2SO4, citric acid, and HCCOH with pH of 2, 4, and 6 respectively, on silica and ash content
Parameters Exp-1 Exp-2
(Control) Exp-24 Exp-25 Exp-26
No washing Ambient water washing H2SO4 + Citric acid + HCCOH
Temperature 35?C
pH - - 2 4 6
Ash (%) 2.26 2.06 1.58 1.69 1.78
Silica (%) 1.24 1.11 0.88 0.90 0.95

[106] From Table 1 to Table 5, it can be observed that the maximum silica content of depithed bagasse reduced was by around 22% (from 1.11% to 0.86%) after giving a treatment with mixture of acidic water. It can also be observed that reduction of 22% silica is achieved after giving a harsh acidic treatment at very low pH. This proves that to remove maximum ash and silica content from depithed bagasse very harsh acidic treatment at very low pH is required, which can damage the fibres and render them unsuitable for use in the hygiene products.

Examples 2
Process for preparing absorbent fibers from depithed bagasse (non-wood lignocellulosic biomass) as per the present invention
[107] The process of preparing absorbent fibers from depithed bagasse obtained as per Example 1 in accordance with the present invention comprised following steps as can be seen from Figure 1:
I. Depithing of bagasse (step (201) (as per Example 1)
II. Enzymatic treatment-1 (202)
III. Mild mechanical treatment (Gentle pulping (203))
IV. Gentle chemical treatment (204)
V. Enzymatic treatment-2 (205)
VI. Gentle bleaching (206)
VII. Enzymatic treatment-3 (207)
VIII. Dewatering and drying (208)
IX. Dry defiberization (209)

[108] In order to improve reduction in ash and silica content as compared to acidic treatment of conventional pulping involving harsh chemical treatment and intense mechanical pulping that can damage the fiber due to harsh treatment and result into dust formation and fines generation during dry defiberization process was avoided with the process of the present invention that can keep fibre’s inherent strength.

I. Enzyme treatment-1
[109] Depithed bagasse (1 kg) steeped in and treated with a singular enzyme or with a combination of enzymes. The enzymes used were cellulase, xylanase, laccase, pectinase, polygalacturonase, and silicase (carbonic anhydrase family) to reduce the ash and silica content of bagasse.
The enzyme treatment was carried out at conditions mentioned in Table 6. The enzymes were used individually or as a mixture for the treatment of the depithed bagasse.
[110] To prepare a mixture of enzyme, enzyme solution was prepared by adding : 0.5% of cellulase, 0.4% of xylanase, 1% of pectinase, 1% of polygalacturonase, 0.5% silicase and 0.3% of laccase in distilled water and mixing.
[111] As can be seen from the below results, treatment of depithed bagasse with enzymes individually or in a combination reduced the ash and silica content.
? Indicates no treatment is given
? Indicates a treatment is given

Table 6: Conditions for treatment of depithed bagasse with enzyme
Parameter Control 1 Treatment Conditions
Enzyme dose (%) ? 0.15 to 2.0 %
Time (min) ? 30 to 120
Temperature (ºC) ? 40- 60
pH Range ? 5 to 7
Pulp Consistency (%) ? 5 -15

Table 7: Effect of the enzyme treatment-1 of depithed bagasse with individual enzyme on silica and ash content
Parameters Exp-2 Control Exp-27 Exp-28 Exp-29 Exp-30 Exp-31 Exp-32
Enzyme Without Enzyme Cellulase Xylanase Pectinase Polygalact-uronase Silicase Laccase
Time (min) ? 60
Enzyme dose (%) ? 1.0
Temperature (ºC) ? 50
pH ? 7
Pulp Consistency (%) ? 10
Ash (%) 2.06 1.77 1.82 1.90 1.89 1.71 1.88
Reduction (%) 14.08 13.56 8.70 8.95 18.23 10.53
Silica (%) 1.11 0.97 1.00 1.03 1.02 0.94 1.02

Table 8: Effect of the enzyme treatment-1 of the depithed bagasse with mixture of enzymes on silica and ash content
Parameters Exp-2 Control Exp-33
Enzyme Without Enzyme Mixture of Enzymes comprising 0.5% of cellulase, 0.4% of xylanase, 1% of pectinase, 1% of polygalacturonase, 0.5% silicase and 0.3% of laccase.
Time (min) ? 60
Enzyme dose (%) ? 1.0
Temperature (ºC) ? 50
pH ? 7
Pulp Consistency (%) ? 10
Ash (%) 2.06 1.48
Reduction (%) 28.16
Silica (%) 1.11 0.81

[112] From Table 8, it can be observed that the maximum silica content of raw depithed bagasse reduced by around 27% (from 1.11% to 0.81%) after treating the depithed bagasse with a mixture of enzymes.

Table 9: Effect of enzyme treatment-1 of depithed bagasse with mixture of enzymes at different doses, on silica and ash content
Parameters Exp-2 Control Exp-34 Exp-35 Exp-36 Exp-37 Exp-38
Enzyme Without Enzyme Mixture of Enzymes as per Exp-33
Time (min) ? 60
Enzyme dose (%) ? 0.15 0.3 0.5 1.0 2.0
Temperature (ºC) ? 50
pH ? 7
Pulp Consistency (%) ? 10
Ash (%) 2.06 1.92 1.84 1.79 1.48 1.40
Reduction (%) 6.80 10.68 14.67 28.16 32.04
Silica (%) 1.11 1.05 1.02 0.97 0.80 0.76

Table 10: Effect of enzyme treatment-1 of depithed bagasse with mixture of enzymes for different time duration on silica and ash content
Parameters Exp-2 Control Exp-39 Exp-40 Exp-41
Enzyme Without Enzyme Mixture of Enzymes as per Exp-33
Time (min) ? 30 60 120
Enzyme dose (%) ? 1
Temperature (ºC) ? 50
pH ? 7
Pulp Consistency (%) ? 10
Ash (%) 2.06 1.81 1.47 1.43
Reduction (%) 12.14 28.64 30.58
Silica (%) 1.11 0.97 0.81 0.79
Reduction (%) 12.61 27.03 28.83

Table 11: Effect of enzyme treatment-1 of depithed bagasse with mixture of enzymes at different temperatures, on silica and ash content
Parameters Exp-2 Control Exp-42 Exp-43 Exp-44
Enzyme Without Enzyme Mixture of Enzymes as per Exp-33
Time (min) ? 60
Enzyme dose (%) ? 1
Temperature (ºC) ? 40 50 60
pH ? 7
Pulp Consistency (%) ? 10
Ash (%) 2.06 1.79 1.49 1.61
Reduction (%) 13.11 27.67 21.84
Silica (%) 1.11 0.97 0.80 0.86

Table 12: Effect of enzyme treatment-1 of depithed bagasse with mixture of enzymes at different pH, on silica and ash content
Parameters Exp-2 Control Exp-45 Exp-46 Exp-47
Enzyme Without Enzyme Mixture of Enzymes as per Exp-33
Time (min) ? 60
Enzyme dose (%) ? 1
Temperature (ºC) ? 50
pH ? 5 6 7
Pulp Consistency (%) ? 10
Ash (%) 2.06 1.6 1.48 1.47
Reduction (%) 22.33 28.16 28.64
Silica (%) 1.11 0.88 0.80 0.79

Table 13: Effect of enzyme treatment-1 of depithed bagasse with mixture of enzymes at different consistency, on silica and ash content
Parameters Exp-2 Control Exp-48 Exp-49 Exp-50
Enzyme Without Enzyme Mixture of Enzymes as per Exp-33
Time (min) ? 60
Enzyme dose (%) ? 1
Temperature (ºC) ? 50
pH ? 10
Pulp Consistency (%) ? 5 10 15
Ash (%) 2.06 1.75 1.47 1.58
Reduction (%) 15.05 28.64 23.30
Silica (%) 1.11 0.96 0.82 0.86

[113] From Table 8 to Table 13, it can be observed the maximum silica content of raw depithed bagasse reduced by around 28% (from 1.11% to 0.80%) after giving a mixture of enzymes treatment.

Table 14: Comparison of treatment of depithed bagasse: control (without enzyme treatment), conventional acid treatment and enzyme treatment-1 as per the present invention on silica and ash content
Parameter Exp-2 Control Exp-24 Exp-33
Treatment Without enzyme Acid Treatment Enzyme Treatment
Enzyme dose (%) ? ? 1.0
Pulp Consistency (%) ? 10 10
Time (min) ? ? 60
Temperature (ºC) ? 35 50
pH ? 2 7
Ash (%) 2.06 1.58 1.48
Silica (%) 1.11 0.88 0.80
[114] From Table 14, it can be observed the silica content of raw depithed bagasse is reduced by around 28% (from 1.11% to 0.80%) after giving an enzymatic treatment with a mixture of enzymes and by only around 22% (from 1.11% to 0.87%) after giving a harsh acidic treatment at very low pH at the same temperature.

II. Mild mechanical treatment
[115] A mild mechanical treatment was given post enzyme treatment-1 and prior to subjecting the pulp to a gentle chemical treatment. Without bound by any theory it is believed that the mild mechanical pulping opens up the fiber for better penetration of chemicals so that gentle chemical treatment can be applied at lower temperature with low chemical dosage.
[1] The pulp obtained after the enzyme treatment-1 was passed through a single pass in a disk refiner at 1500 rpm to 1800 rpm with plate gap between 0.07 mm to 0.7 mm so that Canadian Standard Freeness (CSF) value is between 600 ml to 800 ml.
? Indicates no treatment is given
? Indicates a treatment is given

Table 15: Comparison of effect of control (without enzyme treatment), enzyme treatment-1 alone, and enzyme treatment-1 followed by mild mechanical treatment, on silica and ash content
Parameter Exp-2 Control
(conventional) Exp-33 Exp-51
Enzyme treatment ? ? ?
Mechanical Treatment ? ? ?
Ash% 2.06 1.48 1.41
Silica% 1.11 0.80 0.76
[116] From Table 15, it can be observed that further reduction of silica content is achieved when the enzyme treatment-1 is followed by a mild mechanical treatment.

III. Gentle chemical treatment
[117] A gentle chemical treatment was performed after combination of the mild mechanical treatment and enzyme treatment-1 for delignification. The combination of enzyme treatment and mild mechanical treatment before the gentle chemical treatment is believed to results in improved chemical penetration at lower temperature, which results in less fibre damage. The conditions for the gentle chemical treatment are mentioned in Table 16.

Table 16: Conditions for gentle chemical treatment
Bath ratio 1:2 to 1:10
Chemical Dose 10% to 20%
Chemical NaOH
Temperature( ºC) 80 to 170
Time (min) 30 to 180

Table 17: Effect of treatment: control (conventional chemical treatment); enzyme treatment-1 followed by gentle chemical treatment; and the treatment as per the process of the present invention comprising enzyme treatment-1, mild mechanical treatment, and gentle chemical treatment, on ash and silica content of pulp
Parameter Exp-52 Control
(conventional) Exp-53 Exp-54
Mechanical Treatment ? ? ?
Enzyme Treatment-1 ? ? ?
Chemical treatment ? ? ?
NaOH (%) 20 16 16
Temperature (ºC) 166 166 166
Time (min) 30 30 30
Bath Ratio 1:4 1:4 1:4
Pulp yield (%) 44.2 45.1 44.6
Pulp Ash% 0.92 0.70 0.62
Pulp Silica% 0.52 0.44 0.31
[118] From Table 17, it can be observed that the treated pulp using the process described in the present invention shows higher reduction in ash and silica content compared to the conventional bagasse treatment using alkali (NaOH). The conventional chemical treatment using higher concentration of alkali is known to be detrimental to the fibre quality rendering such alkali treated fibres unsuitable for use in the hygiene products.
[119] It can be seen from Table 17 that the pulp obtained by the process of the present invention comprising enzyme treatment, mechanical and chemical treatment provided absorbent fibres with much improved characteristics in comparison to conventional treatment.

IV. Enzyme treatment-2
[120] Pre-bleaching enzyme treatment-2 was carried to reduce abrasive minerals, residual pith and silica content. The pulp obtained from Exp-53 and Exp-54 was subjected to an enzyme treatment-2 followed by gentle bleaching and post-bleaching enzymatic treatment-3.
[121] For the enzyme treatment-2, mixture of enzymes as prepared under Enzyme Treatment-1 (Exp-33) was used.

V. Gentle Bleaching
[122] To enhance the brightness of the pulp, Elemental Chlorine Free (ECF) bleaching or Totally Chlorine Free (TCF) bleaching process was carried out. The pulp obtained after enzyme treatment-2 was subjected to (ECF) bleaching and TCF bleaching separately. The integrity and strength of cellulose fibre during belching process is very important as weak cellulose fibre results in dust and fines formation during dry defiberization stage when the pulp sheet comes in contact with rotating hammermill blades at high rpm. To protect the integrity of cellulose fiber during peroxide treatment, treatments with chelating agent EDTA along with hydrogen peroxide was given.
[123] These gentle belching methods are not only environmentally friendly, but also result in lower effluent that needs to be treated at wastewater treatment plant.

VI. Enzyme treatment-3
[124] To further reduce silica and minerals, subsequent to enzyme treatment-2 (pre-treatment) followed by gentle bleaching, an enzyme treatment-3 (post-treatment) was applied in accordance with Exp-54.
[125] The pre and post enzyme treatments collectively reduce the overall silica content and amount of dust formation during dry defiberization process.

Table 18: Effect of : enzyme treatment-1, mild mechanical treatment, and gentle chemical treatment; enzyme treatment-1, mild mechanical treatment, gentle chemical treatment; enzyme treatment-2,ECF bleaching (DOEOPD) and enzyme treatment-3, on ash and silica content
Parameter Control Exp-54 Exp-55 Exp-56
Pulp Ash% 0.92 0.70 0.62
Pulp Silica% 0.52 0.44 0.31
Kappa number 14.7 14.5 14.3
Enzyme treatment-2 (pre-treatment)(Consistency - 8.0%, Temperature - 50°C, Time - 1 h, dose 0.02%)
Enzyme treatment-2 (pre-treatment) Dose (g/T) ? 200 200
D0 stage (Consistency - 5%, Time - 45 min, Temperature-55°C)
ClO2 added (%) 1.34 1.32 1.30
End pH 2.5 2.4 2.4
EOP stage (Consistency - 10.0%, Time - 120 min, Temperature - 80oC, H2O2- 0. 5%)
NaOH added (%) 2.0 2.0 2.0
End pH 10.4 10.5 10.5
Kappa number 1.8 1.7 1.7
D Stage (Consistency - 10%, Temperature - 75°C, Time - 180 min.)
ClO2 added (%) 0.3
End pH 3.4

Enzyme treatment-3 (post–bleaching treatment) Dose (g/T) ? 200 200
Conditions ( Temperature- 50(ºC), pH 7.0, consistency 10%, time 1h)
Ash% 0.43 0.27 0.18
Silica% 0.043 0.017 0.012

Table 19: Effect of : enzyme treatment-1, mild mechanical treatment, and gentle chemical treatment; enzyme treatment-1, mild mechanical treatment, gentle chemical treatment; enzyme treatment-2, TCF bleaching (P), and enzyme treatment-3, on ash and silica content
Parameter Control Exp-54 Exp-57 Exp-58
Pulp Ash% 0.92 0.70 0.62
Pulp Silica% 0.52 0.44 0.31
Enzyme treatment-2 (pre-treatment)(Consistency - 8.0%, Temperature - 50°C, Time - 1 h, dose 0.02%)
Enzyme treatment-2 (pre-treatment) Dose (g/T) ? 200 200
Kappa number 14.7 14.5 14.3
P-stage (Consistency - 10.0%, Time - 120 min, Temperature - 80oC, EDTA- 0.5%, H2O2- 2.0%)
NaOH added (%) 2.0 2.0 2.0
End pH 10.2 10.2 10.1
Kappa number 14.7 10.1 9.9
P- Stage (Consistency - 10%, Temperature - 80°C, Time - 120 min., EDTA- 0.5%, H2O2- 1.0%)
NaOH added (%) 1.0
End pH 10.4

Enzyme treatment-3 (post–treatment) Dose (g/T) ? 200 200
Conditions ( Temperature- 50(ºC), pH 7.0, consistency 10%, time 1h)
Ash% 0.52 0.32 0.22
Silica% 0.072 0.020 0.016
[126] From Table 18 and 19, it can be observed that the bleached pulp with pre-bleaching and post-bleaching enzyme treatments in accordance with the process of the present invention shows higher reduction in ash and silica content compared to bagasse pulp without such treatments.

VII. Dewatering and drying
[127] Bleached pulp slurry was passed through a wire screen and was subjected to gentle dewatering and pressing cycles. Dewatered pulp with reduced moisture and water content was further dried either at room temperature or with hot air. Gentle dewatering and gentle drying cycles transformed the pulp into sheet.

Table 20: Comparison of physical properties, chemical constituent and fiber morphology of control and pulp obtained by and the process of the present invention
Pulp properties Control Exp-54 Exp-55 Exp-56 TEST METHOD
Moisture, % 8.4 8.3 8.4 TAPPI (T-550)
Bulk (g/cm3 ) 1.21 1.35 1.34 TAPPI (T-411)
Grammage (oven dry), g/m2 500 500 500 ISO 536
Burst (kpa m2/g) 1.41 0.10 0.98 TAPPI (T-403)
Ash (%) 0.43 0.27 0.18 TAPPI (T-211)
Silica (%) 0.043 0.017 0.012 TAPPI (T-244) & HF treatment
Chemical constituents of Pulp with ECF treatment
Cellulose (%) 77.8 78.2 78.4 Updegraff DM (1969)
Hemicellulose (%) 18.3 18.2 18.4 Deschatelets and Ernest, 1986
Lignin (%) 2.01 1.80 1.62 T 222 om-98
Fiber Morphology
Average fiber mean length (mm) 0.87 1.00 1.01 MorFi Neo
[128] From Table 20, it can be observed that the pulp obtained by the process of the present invention showed several advantageous characteristic features. The burst factor of pulp obtained by the process of the present invention reduced from 1.41 to 0.98 kpa m2/g, indicating optimal fiber-to-fiber bonding achieved so that the fibers can be properly individualized during dry defibration stage to form a highly porous fiber matrix for better absorption and retention properties and result in less fines generation and dust formation. Low burst factor means that less energy is required to individualize the fibers.
[129] The ash content of the pulp is significantly reduced from 0.43 % to 0.18% and the silica content of pulp is significantly reduced from and 0.043 % to 0.012%. Ash and silica can have a significant impact abrasion of hammer mill blade due to their abrasive nature.
[130] The average mean length of fiber is improved compared to the pulp obtained by control chemical treatment as less fiber damaged occurs during dry defiberization due to lower burst factor and less dust formation while simultaneously ensuring that the pulp also has high hemicellulose content.

VIII. Dry defiberization
[131] Dry defiberization was performed between 3000 rpm to 6000 rpm and at blade gaps between 0.2 mm to 1 mm that increased the amount of “good fiber” (which is fibre without broken throughout its length).

Table 21: Comparison of fluff pulp properties after defiberization of control bagasse pulp and the fluff pulp obtained by the process of the present invention
Fluff Pulp properties Control
Exp-54 Exp-55 Exp-56 TEST METHOD
“Good Fiber” Amount (%) 72 91 93 NIT Counter
Dust Formation (%) 28 9 7 NIT Counter
Absorption capacity, (g/g) 8.2 8.7 9.1 SCAN-C 33:80
Absorption Time (sec)/3g 6 4 4 SCAN-C 33:80
[132] From Table 21, it can be observed that the fluff pulp properties are significantly improved in treated pulp of the present invention. The “Good fiber” content in the treated pulp obtained by the process of the present invention is around 93% which is significantly higher than that of around 72% in untreated fluff pulp. Similarly, dust formation in treated pulp is around 7% which is significantly lower than that of around 28% in untreated bagasse fluff pulp.
[133] The absorption capacity of pulp also increased from 8.2 to 9.1 g/g and absorption time is improved from 6 seconds to 4 seconds.

Table 22: Comparison of fluff pulp properties of softwood fluff pulp, hardwood fluff pulp and treated bagasse fluff pulp obtained by the process of the present invention
Parameter Softwood fluff pulp Hardwood fluff pulp Fluff pulp Exp-56 (present invention)
Water Retention Value (g/g) 0.79 1.07 1.28
Absorption capacity (g/g) 9.0 8.89 9.1
Absorption rate (sec/3g) 3 6 4
Ash% 0.18 0.29 0.18
Silica (%) 0.014 0.010 0.012
[134] From Table 22, it can be observed that the fluff pulp obtained by the process of the present invention shows enhanced properties when compared with softwood and hardwood pulp. Water Retention Value of bagasse fluff pulp obtained by the process of the present invention is higher compared to the conventional softwood fluff pulp as well as hardwood fluff pulp.

Table 23: Comparison between conventional bagasse pulp and pulp obtained by the process of the present invention
Pulp properties Conventional Bagasse Pulp Fluff pulp Exp-56 (present invention) Test Method
Moisture, % 8 -12 8 -12 TAPPI (T-550)
Bulk (g/cm3 ) 1.21 1.34 TAPPI (T-411)
Grammage (oven dry), g/m2 500±20 500±20 ISO 536
Burst (kpa m2/g) 1.41 0.98 TAPPI (T-403)
Ash (%) 0.43 0.18 TAPPI (T-211)
Silica (ppm) 430 120 TAPPI (T-244) & HF treatment
“Good Fiber” Amount (%) 72= =90 NIT Counter
Absorption Time (sec)/3g 6 4 SCAN-C 33:80
Absorption capacity, g/g 7.9 9.1 SCAN-C 33:80

[135] It can be clearly seen form Table 21 that the pulp properties are significantly improved in the pulp obtained by the process of the present invention. The “Good fiber” content in untreated conventional pulp is 72= % and dust formation is =28 while in pulp obtained by the process of the present invention it is increased to =90 and dust formation is reduced to 10=.
[136] The overall result shows that fluff pulp obtained by the process of the present invention exhibited enhanced properties when compared with softwood pulp, hardwood pulp and conventional bagasse pulp.

ADVANTAGES OF THE PRESENT INVENTION
[137] Treatment of depithed bagasse with enzyme(s) results in removal of ash and silica contents.
[138] Hemicellulose rich pulp is obtained while reducing ash and silica contents.
[139] Treatment of the pulp per- and post- bleaching of the pulp helps in further removal of ash and silica contents.
[140] “Good fiber” content is increased and dust formation is decreased during defiberization.
[141] High water retention values are achieved compared to conventional fluff pulp made from soft wood of hard wood in shorter duration.
[142] The embodiments as described above explain various aspects and features of the present invention and its practical application, to thereby enable others, skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may require or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.
,CLAIMS:

1. A process for preparing absorbent fibers from non-wood lignocellulosic biomass comprising:
(i) providing a depithed non-wood lignocellulosic biomass by subjecting a non-wood lignocellulosic biomass material to a depithing;
(ii) subjecting said depithed non-wood lignocellulosic biomass to an enzyme treatment-1 for 30 minutes to 240 minutes at 30°C- 60°C;
(iii) subjecting the pulp after enzyme treatment-1 to mechanical pulping and separating into a pulp fraction comprising cellulose and hemicellulose, and a lignin fraction;
(iv) subjecting the pulp comprising cellulose and hemicellulose obtained after mechanical pulping to a chemical treatment;
(v) subjecting the pulp in step (iii) to an enzyme treatment-2 for 30 minutes to 240 minutes at 30°C- 60°C;
(vi) subjecting the pulp after enzyme treatment-2 to a bleaching treatment;
(vii) subjecting the bleached pulp to an enzyme treatment-3 to obtain a pulp with reduced ash and silica content;
(viii) dewatering and drying the pulp of step (vii);
(ix) defiberizng the dry pulp at 3000 rpm to 6000 rpm to produce absorbent fibers.
2. The process as claimed in claim 1, wherein said non-wood lignocellulosic biomass is an agricultural waste reside selected from sugarcane bagasse, straw wastes, corn wastes, spent grains, banana fiber, bast fiber such as flax, hemp, jute, kenaf and ramie.
3. The process as claimed in claim 1, wherein the process optionally includes pretreatment step, wherein the depithed non-wood lignocellulosic biomass is washed with water or acid.

4. The process as claimed in claim 3, wherein the pretreating of the depithed non-wood lignocellulosic biomass with water is carried out at a temperature of 30°C- 80°C.
5. The process as claimed in claim 1, wherein the pH during the enzyme treatment-1, enzyme treatment-2 and enzyme treatment-3 is from 5 to 7.
6. The process as claimed in claim 1, wherein the concentration of enzyme(s) in the enzyme treatment-1, enzyme treatment-2 and enzyme treatment-3 ranges from 0.15-2.00%.
7. The process as claimed in claim 1, wherein the pulp to enzyme ratio in the enzyme treatment-1, enzyme treatment-2 and enzyme treatment-3 is 1:5 to 1:10.
8. The process as claimed in claim 1, wherein the mechanical pulping of fibers is carried out with a tool selected from a disc refiner, valley beater, blender, single disc refiner, and double disc refiner.
9. The process as claimed in claim 1, wherein the ratio of pulp to chemical in step (iv) is 1:2 to 1:10.
10. The process as claimed in claim 1, wherein the chemical for the chemical treatment of the pulp in step (iv) is selected from NaOH, Kraft, or Sulphite.
11. The process as claimed in claim 1, wherein the concentration of the chemical for the chemical treatment of the pulp in step (iv) is from 10% to 20%.
12. The process as claimed in claim 1, wherein the process includes an enzyme treatment-2 as a pretreatment to bleaching step.
13. The process as claimed in claim 1, wherein said bleaching treatment in step (vi) includes step of bleaching with Elemental Chlorine Free (ECF) bleaching or Totally Chlorine Free (TCF) bleaching.
14. The process as claimed in claim 1, wherein the bleaching is carried out in the presence of a chelating agent selected from ethylenediaminetetraacetic acid (EDTA), magnesium sulfate (MgSO4), diethylenetriamine penta(methylene phosphonic acid) (DTPMPA), and diethylenetriamine pentaacetate (DTPA).
15. The process as claimed in claim 1, wherein the process includes an enzyme treatment-3 as a post treatment to bleaching step.
16. The process as claimed in any one of the claims 1-15, wherein the enzyme is selected from cellulase, endoglucanase, xylanase, laccase, pectinase, polygalacturonase, silicase, or mixture thereof.
17. The process as claimed in claim 16, wherein the mixture of enzyme comprises cellulase, xylanase, pectinase, polygalacturonase, silicase, and laccase.
18. The process as claimed in claim 16, wherein the mixture of enzyme comprises cellulase 0.1-10%, xylanase 0.2-8%, pectinase 0.1-10%, polygalacturonase 0.1-10%, silicase 0.1-15%, and laccase 0.1-5%.
19. The process as claimed in any one of the claims 1 to 18, wherein the absorbent fibers have a length of 0.9 to 2.8 mm.
20. The process as claimed in any one of the claims 1 to 19, wherein said absorbent fibers have a burst factor in the range of 0.98 to1.41 kpa m2/g.
21. The process as claimed in any one of the claims 1 to 20, wherein said absorbent fibers have an absorption capacity of 9 to 10 g/g with absorption time ranging from 2.5 to 5 s/3g unit.
22. The process as claimed in any one of the claims 1 to 21, wherein said absorbent fibers have a water retention value of 1.28 (g/g).