GB2609040A - Biodegradable and reusable cellulosic microporous superabsorbent materials - Google Patents

Abstract

A process for preparing a cellulose-containing microporous superabsorbent composition includes comminuting dry granulated herbaceous plant material, e.g. sugar beet, orange peel or apple residue, to form microparticles having an average particle diameter from 100μm to 800μm. Preferably the method includes contacting the microparticles with an aqueous alkaline solution, neutralising and/or washing the mixture, removing fluids from the mixture, and drying the obtained material. The starting material may comprise less than 20wt.% lignin. The superabsorbent composition may have a water absorption capacity (WAC) in the range of from 2 to 10. The cellulosic superabsorbent composition may be a material which comprises a fluid-superabsorbent volume area able to absorb 3-6 times of the original weight within 30 seconds, and may exhibit a virucidal activity as expressed by a reduction in viral titre of influenza A and/or human coronavirus of above 90% as determined pursuant to ISO18184:2019. The material may be in the form of a medical, surgical, sanitary or protective article, e.g. a dressing, pad, tampon, gown, glove etc, a packaging material or a particulate absorbent for spills. An antimicrobial or other functional agent may be adhered to the material to form a functionalised superabsorbent composition.

Description

BIODEGRADABLE AND REUSABLE CELLULOSIC MICROPOROUS SUPERABSORBENT MATERIALS

Technical Field

The present invention relates to a process for preparing a biodegradable and reusable cellulose-containing adsorbent materials, with inherent antimicrobial activity, from herbaceous plant material. The materials are useful for a wide variety of applications, such as air filtration; water filtration; garments; surgical bandages and packing materials, and generally, any application where the ability adsorb and desorb humidity and stop bacterial growth and/or viral proliferation is desired.

Background to the Invention

The present invention relates generally to the field of biodegradable cellulosic adsorbent materials, more specifically to highly adsorbent materials with inherent antimicrobial activity, which can be reused after drying off of volatile fluids, and their use in a variety of different applications, including materials for air filtration; water filtration; garments; surgical bandages and packing materials, and generally, any application where the ability adsorb and desorb humidity and stop bacterial growth and/or viral proliferation is desired. A main function of absorbents is the absorption of various fluids. These fluids, e.g. wound exudates, are frequently rich in nutrients and are capable of supporting abundant bacterial growth, which can easily cause serious infection and may also release a variety of harmful toxins. Filter materials may also acquire a number of biological pathogens, such as microbes a viral particles by physical adsorption to the surface thereto, but once the surface is saturated, these may be released and leach out into the medium. This is in particular relevant for filters that are to be reused, e.g. filter materials for breathing air, e.g. face masks or HVAC filters for vehicles or buildings. wherein the filters traditionally have been replaced once fully loaded.

Often, these materials a modified by addition of antimicrobial agents. However, these modifications tend to render the components pricey, and their use may introduce antibiotic agents to the environment, which may lead to resistance development. Yet further, most super-absorbents presently employed lack high biodegradability.

In conclusion, with regard to the above descriptions of the art, it is apparent that there is a need for an improved absorbent that has inherent antimicrobial abilities, is superabsorbent, can be modified or shaped easily, offers antimicrobial activity and is non-leaching upon use, washable and reusable, and that allows complete biodegradation at the end of life due to entirely sustainable components.

Summary of the Invention

In a first aspect, the present invention provides a process for preparing a cellulose-containing microporous superabsorbent composition, the process comprising the steps of: (a) comminuting dry granulated herbaceous plant material to form microparticles having an average particle diameter of from 10 p.m to 1000 pm; to obtain the cellulose-containing microporous superabsorbent composition.

Surprisingly, the present process finds several unexpected advantages despite commencing with particles of plant material of a size broadly equivalent to that obtained in prior art processes which homogenise plant material in water to form a slurry. The advantages noted include a viscosity for the present slurry obtained in step (a) which allows improved processing at a higher solids content relative to prior art processes. Also, It has surprisingly been found that forming the plant material into the particles without complete degradation of the cell wall enables the material to form a superabsorbent material, that can be readily dried and reused, and that exhibit antimicrobial and in particular antiviral properties.

In a second aspect, the present invention provides cellulose-containing superabsorbent material obtainable by the process of the present invention, the cellulose-containing material having a fluidsuperabsorbent volume area able to absorb of from 2 to 10 times of the original weight of water within 30 seconds (WAC), and exhibiting a virucidal activity as expressed by a reduction in viral titre of influenza A and/or human coronavirus of above 90%, as determined pursuant to standard method 1S018184:2019.

Detailed Description of the Invention

The process of the present invention is now described in further detail. Optionally, the process of the present invention can be carried out as a continuous process, rather than being conducted batch-wise. This has significant advantages in terms of the efficiency of the process. The low viscosity of the mixture formed in the present invention enables continuous processing to be conducted without difficulty.

As used herein, the term "antimicrobial" herein relates to having an adverse effect on a range of pathogenic microorganisms, including bacteria and at least some fungi and viruses. "Antibacterial" refers to as having an adverse effect on bacteria, particularly disease-causing bacteria; and the term "antiviral" refers to as having an adverse effect on spread of viral diseases.

As used herein, "a," "an," "the," "at least one," and "one or more" are used interchangeably. Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range. The terms "comprises" and variations thereof do not have a limiting meaning where these terms appear in the description and claims. The words "preferred" and "preferably", advantageous refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.

Plant Material: The starting material for the materials according to the present invention comprises herbaceous plant material. The term "herbaceous" as defined herein refers to plants which are annual, biennial or perennial vascular plants. In annual, biennial or perennial vascular plants, the stem matter dies after each season of growth when the plant becomes dormant, i.e. biennial or perennial plants, or dies, i.e. annual plants. Biennial or perennial plants survive unfavourable conditions underground and will regrow in more favourable conditions from such underground portions of the plant, typically stem, roots, or storage organs such as tubers. In contrast, the stems of woody species remain during any period of dormancy, and in a period of further growth will form growth rings which expand the girth of existing tissue. Herbaceous plants are characterised by parenchymal tissue having an abundance of primary cell walls within the tissue. One skilled in the art would also be aware that the mosses and macro algae also consist of an abundance of primary cell walls, and hence are included within the term "herbaceous plant material" as used herein. Herbaceous plant material is preferably used as a starting material within the present invention.

Optionally, the starting material of the present invention substantially consists of herbaceous plant material. It can be advantageous for the starting material of the present invention to consist of herbaceous plant material, and thereby exclude wood or wood products. Depending upon the intended end use of the cellulose-containing material, however, it may not, however, be necessary to totally avoid inclusion of non-herbaceous plant material such as wood within the plant starting material.

In particular, the plant material used in the process of the present invention can conveniently include vegetables, for example root vegetables, and fruit. Non-limiting examples of suitable root vegetables include carrot, sugar beet, also commonly referenced as "beet", turnip, parsnip and swede. Exemplary fruit materials which can be used within the present invention includes apples, pears, citrus and grapes. Optionally, the plant material may be from tubers, for example potato; sweet potato, yam, rutabaya and yucca root can also be used.

Generally, it is anticipated that the process of the invention will be operated using waste or coproducts from the plant material after a main product has been extracted, for example sugarbeet pellets, vegetable peelings or citrus waste after juicing, jam-making or the like. However this is not strictly necessary, and the process could be operated using vegetable or fruit grown specifically for that purpose. It is also not necessary for the plant material to be used as a starting material in the process of the present invention to comprise material from only one specific plant source.

Optionally, a mixture of materials from different plant sources can be used. For example, the starting material can comprise a mixture of different root vegetables, a mixture of different fruits, a combination of fruit and vegetable(s), including a mixture of root vegetables together with a mixture of fruits.

Generally, the plant material to be used as a starting material for the present invention will not comprise a significant quantity of lignin. Optionally, the starting material for the present invention will comprise less than about 20 wt % lignin, for example less than about 10 wt % lignin, for example less than about 5 wt % lignin, for example less than 2 wt% lignin, for example less than about 1 wt% lignin. A number of methods for the measurement of lignin content are known in the art and include methods such as the "Klason method", the acetyl bromide method and the thioglycolic acid method. Hatfield and Fukushima (Crop Sci. 45:832-839, 2005) discuss methods of lignin measurement.

The plant material preferably comprises chemically untreated raw plant material, i.e. uncooked.

Alternatively, it may have been subjected to an extraction step to remove water soluble compounds, reducing or eliminating the need for an additional washing treatment.

A particularly preferred plant material comprises sugar beet (beta vulgaris) materials obtained after the sugar juice extraction step. Other suitable materials may be passed through a similar process, e.g. orange peels or apple residue obtained from pressing of juice. Ideally, in this process, the raw plant materials are washed to remove any non-plant material debris or contaminants and leaves. Then typically juice is obtained from those plant materials, by washing and cut up into chips having a thickness in the range of from 0.2 to 0.5 cm. In case of sugar beets, sugar is extracted from these chips typically by contacting the chips with hot extraction water, usually in a counter-current direction in an extraction tower. The crude extract is then usually filtered off, and further worked up. The remaining chips were found to form a particularly good starting material for the present process. In the production of sugar, sugar beets are harvested, washed and processed in sugar beet cutting machines to form chips. The beet chips are subsequently extracted with hot water, at a temperature ranging of from 65° C to 75° C, generally in a counter-current flow direction, and primarily using a diffusion process, and eventually a physical separation, such as pressing and/or centrifugation. This results in extracted sugar beet chips and sugar-containing raw sugar beet juice. These extracted sugar beet chips primarily comprise of the cell wall and fibre constituents of the extracted sugar beet. In a subsequent processing stage, the beet chips are typically further dewatered by pressing them in so-called pulp presses, which results in pressed chips and released press water, optionally also using pressing aids. These dewatered and pressed chips are then typically subjected to a thermal removal of the residual water. Herein, the pressed chips are dried at an elevated temperature in rotating and heated drying drums, evaporating residual water and constituents volatile at the conditions. Conventional drying systems apply a so-called high-temperature drying, whereas alternative drying methods make use of indirect drying by means of superheated steam using a fluidized-bed method. Sugar-containing molasses are typically added at this stage if the pressed chips are to be employed as animal feed component. The pressed and dried chips are then usually pelletized, by simultaneously pressing the chips to obtain a compressed composition, and by passing the compressed composition through a granulator such as an extruder or hammer mill, wherein the composition is pelletized. The thus obtained pellets are usually added to animal feedstuff, typically those enriched with sugar-containing molasses.

The plant material may also be treated prior to, or after comminuting to a smaller particle size.

Alternatively, the obtained microparticulate matter may be treated. Accordingly, the material may be subjected to a process involving contacting the plant material or obtained with a suitable reagent, such as an alkaline reagent, such caustic soda or lye, and/or water, or an aqueous solution of a peroxide, such as hydrogen peroxide, and/or an oxidative treatment, such as e.g. a hypochlorite. It is not essential for the reagent to be added simultaneously with the water. However, it is often convenient to add the water and reagent simultaneously. For example, it is possible to premix the reagent with the water and then to add the water-reagent mixture to the plant material, or microparticles. Alternatively, it is possible to add water to the particles of plant material to form an aqueous slurry, and then to add the reagent to the slurry. Advantageously, addition of the water and/or reagent is accompanied by stirring of the resultant mixture to facilitate formation of a homogenous composition. The volume of water to be added is not particularly critical, but may typically be from 2 litres to 30 litres water per kg plant material particles. This is in addition to any solution of reagent which may additionally be added. One of the benefits of the present invention is the relatively high percentage of solids which can be present within the mixture after the addition of water and reagent. In some embodiments, the mixture formed in step (a) can contain more than 2 wt% solids. In some embodiments, the mixture formed in step (a) can contain at least 3 wt% solids, for example at least 4 wt% solids, at least 5 wt% solids, at least 6 wt% solids, at least 7 wt%, at least 8 wt% solids, at least 9 wt% solids, or at least 10 wt% solids.

This treatment step is intended to essentially to not break down the particles, but to remove components that may dissolve easily, and hence later may lead to leaching out of the antimicrobial agents. The process may then be followed by a filtration and washing step to remove unused reagent and soluble components, and drying step.

The cellulosic product, whether washed, treated and washed or directly obtained from a process to remove juices or other desired components is then subjected to a comminution step, e.g. by milling the materials, to obtain a microparticulate material.

The microparticulate material thus obtained was found to be able to super-adsorb fluids, e.g. water in an amount of from 3 to 6 times its dry weight. Also, it was found that the material is doing so very swiftly. Without wishing to be bound to any particular theory, this is believed due to the inherent capillary porosity of the material, which allows wicking of a fluid.

It was found that the superabsorbent composition had a water absorption capacity (WAC) in the range of from 2 to 10, prefearbly of from 3.5 to 6.5.

It was found that surprisingly, the materials as such has an inherent has very good antiviral activity against certain viruses, particularly enveloped, such as COVID and influenza viruses. This is in particular relevant since it has proven difficult to produce an effective disinfectant that does not readily wash out of the material, in particular when subjected to an industrial our household detergents and washing and drying process. Hence wash out, or leaching usually occurs, which reduces effectiveness and may cause irritation, or infections. This is a general problem where absorptive packings are placed in contact with significant possibility for dangerous pathogen load, e.g. viral load, or bacterial growth.

In addition, due to the globalization of transport, the emergence of new diseases and pandemics, the uses for a technology that imparts a essentially non-leaching re-useable antimicrobial modification to a variety of materials is duly recognized. Specific areas of use in are described below herein.

And last but not least, sustainable materials would be desired which may simply be subjected to compost preparations, preferably after extraction of valuable antimicrobial components, metals and the like.

Production of the Superabsorbent Materials The absorbent particles can be formed using any suitable means. Preferably, water or other liquid is not added to the plant material prior to comminution to form the particles. Thus, the plant material is not in the form of a slurry or suspension during the comminution step. Thus the process can include a step of comminuting plant material in the absence of liquid to form particles of plant material. Optionally, the plant material contains less than 30 wt% water prior to comminution, for example contains less than 20 wt% water, for example contains less than 15 wt% water. In some embodiments, the plant material can be dried (e.g. at ambient temperature or at higher temperatures) before being formed into particles. The comminuted material can be screened to select particles of the desired size.

The particles of plant material can be formed by grinding or milling. For example, the plant material can be processed in a mill or using a grinding apparatus such as a classifier mill to provide particles of the required diameter size.

Preferably, a combination of a mechanically acting mill, i.e. one where the plant materials is crushed and torn apart and thus comminuted between actors, and a subsequent particle sizing is employed, e.g. by gravity or density, or sieving. However, the apparatus used to produce the particles from the plant material is not particularly critical to the successful operation of the process.

Methods for comminuting are not limited in particular, and include, for example, methods by a ball mill, a rod mill, a hammer mill, an impeller mill, a high-speed mixer, attritor mills and/or a disk mill. Of these, preferred are attritor or cell mills, as described for instance in publication W020131167851, or in US3131875, US3339896, US3084876, and US3670970. In an attritor mill, a high shear field for is attained causing;attrition or size reduction of the solid particulate matter. A particularly useful cell mill, coupled with sieves, may be obtained from Atritor Limited, Coventry.

Particle Size and Particle Size Distribution: The particles of plant material used within the process of the present invention have a mean average diameter of from 10 pm to 1000 pm, preferably of from Ltm to 300 p.m The term "diameter" refers to the measurement across the particle from one side to the other side. One skilled in the art would recognise the particles would not be perfectly spherical, but may be near-spherical, ellipsoid, disc-shaped, or even of irregular shape. One skilled in the art would also be aware that a range of diameters would be present within the starting material.

To obtain the benefits of the present invention, it is not necessary to meticulously exclude very small quantities of particles which fall outside the stated particle diameter size. However, inclusion of particles of different diameter sizes within the starting material can, in some circumstances, adversely affect the quality of the end product.

Optionally, at least 60% by volume of the particles have a diameter of from 10 pm to 1000 p.m, for example at least 70% by volume of the particles have a diameter of from 10 p.m to 1000 pm, or at least 80% by volume of the particles have a diameter of from 10 pm to 1000 pm, or at least 85% by volume of the particles have a diameter of from 10 pm to 1000 pm, or at least 90% by volume of the particles have a diameter of from 10 Ltm to 1000 pm, or at least 95% by volume of the particles have a diameter of from 10 pm to 1000 pm, or even at least 98% by volume of the particles have a diameter of from 10 pm to 1000 p.m. Conveniently 99% by volume of the particles have a diameter of from 10 pm to 1000 pm. In some circumstances it may be advantageous to ensure that substantially all of the particles have a diameter of from 10 pm to 1000 p.m.

Depending upon the source of the starting material and/or the intended end use of the cellulose-containing material, it can be advantageous to select particles having a mean average particle diameter size within a narrower range. For example, particles of plant material used within step (a) of the process of the present invention can have a mean average diameter of from 50 p.m to 800 pm, or from 100 pm to 600 pm. In some circumstances, at least 60% by volume of the particles have a diameter of from 50 pm to 800 pm, for example at least 70% by volume of the particles have a diameter of from 50 pm to 800 pm, or at least 80% by volume of the particles have a diameter of from 50 pm to 800 pm, or at least 85% by volume of the particles have a diameter of from 50 pm to 800 pm, or at least 90% by volume of the particles have a diameter of from 50 pm to 800 pm, or at least 95% by volume of the particles have a diameter of from 50 pm to 800 p.m, or even at least 98% by volume of the particles have a diameter of from 50 pm to 800 pm. Conveniently, 99% by volume of the particles have a diameter of from 50 pm to 800 pm. In some circumstances it may be advantageous to ensure that substantially all of the particles have a diameter size of from 50 pm to 800 pm.

Alternatively, the particles of plant material used within step (a) of the process of the present invention can have a mean average diameter of from 200 pm to 400 pm. In some circumstances, at least 60% by volume of the particles have a diameter of from 200 pm to 400 pm, for example at least 70% by volume of the particles have a diameter of from 200 pm to 400 pm, or at least 80% by volume of the particles have a diameter of from 200 pm to 400 pm, or at least 85% by volume of the particles have a diameter of from 200 pm to 400 pm, or at least 90% by volume of the particles have a diameter of from 200 p.m to 400 p.m, or at least 95% by volume of the particles have a diameter of from 200 pm to 400 pm, or even at least 98% by volume of the particles have a diameter of from p.m to 400 pm. Conveniently 99% by volume of the particles have a diameter of from 200 pm to 400 pm. In some circumstances it may be advantageous to ensure that substantially all of the particles have a diameter of from 200 pm to 400 pm.

Particles of the required diameter and within the predetermined particle size distribution can be selected using known methods, including (but not limited to) sieving the particle mixture with one or more sieves of known sieve size.

For example, passing the material sample through a sieve having a mesh size of 500 pm will only allow particles having a particle diameter of 500 pm of less to pass through. The sieved material can then be sieved again using a sieve having a smaller mesh size, for example a mesh size of 300 pm.

The particles retained on the smaller mesh (i.e. which do not pass through) will have a particle size distribution of 200 pm and range in size from 300 p.m to 500 pm. Of course, sieves of alternative sieve size and in different combinations can be used to obtain any required particles diameter size range and particle size distribution. Alternatively, a classifier mill or other suitable means can be used to select particles of the required particle size and size distribution.

Step (c) may comprises washing, or, if desired, neutralising the hydrated mixture to form a washed hydrated mixture. As indicated above, step (c) can include one or more washing steps. Typically, washing requires the cellulose material to be separated from the liquid fraction, and then re-suspended (optionally with agitation or stirring) in clean liquid, such as water. The washing step essentially removes any excess reagent, and also any soluble by-products formed in step (a).

Also, if a treatment has been applied, the mixture may be washed, and/or neutralised, to a desired pH. Neutralising the mixture of step (b) after the end point pH has been reached can reduced or even eliminate the requirement for a washing step, thereby reducing the amount of water consumed during the manufacturing process, which is an important environment consideration. Neutralisation can be achieved by addition of an appropriate amount of an acid in an amount sufficient to change the pH of the mixture to a neutral pH. The acid can be added in any convenient form, but typically will be added as a powder or in the form of an aqueous solution. Alkalis such as sodium hydroxide, potassium hydroxide, calcium carbonate or the like can conveniently be used for the treatment. Optionally, once the hydrated mixture has been neutralized (and optionally mixed therewith), the cellulose-containing material can be separated from the liquid fraction by any suitable means.

Alternatively, the step of neutralisation can be performed after the cellulose-containing material has been separated from the liquid fraction. For example, the cellulose-containing material can be separated and then re-suspended before a suitable amount of acid is added. Alternatively, the separated cellulose-containing material can simply be suspended in an acidic solution. The step of separating the cellulose-containing material from the liquid fraction can be achieved using any suitable apparatus or process, including without limitation filtration (simple or vacuum filtration), centrifugation, membrane filtration etc. A woven filter can be used. Alternatively a mesh filter can be used. Optionally, where filtration is used during the washing step, the filter has a pore size of 200 pm or less, for example has a pore size of 100 pm to 200 pm. A smaller pore size can also be used.

Optionally, the washing and/or neutralising step (c), if present, is conducted in a manner which is compatible with a continuous manufacturing process. For example a filter at an angle of approximately 45° to the horizontal may advantageously be used, with the material to be filtered being dropped onto the filter from above so that liquid drains through the filter whilst solids are retained on the upper surface of the filter. The angle of the filter cause these retained solids to slide gently down the filter's upper surface onto a belt, or into a hopper or other receptacle ready for further processing. Alternatively a belt filter press can be used.

Step (d): Once step (c) is complete (including any optional washing and/or neutralising steps), the obtained material may be isolated, and water removed. The material may be dried to touch dryness; e.g. comprising a water content equivalent to exposure of dry material to average air humidity; or dried further and package under exclusion of air humidity Methods for drying are well-know, and include drying cylinders, rotating drums, belts and the like, typically heated by superheated steam or hot air; and also may include reduced pressure. Preferred is heat drying under reduced pressure, i.e. heated vacuum drying. Drying may preferably be done by subjecting the materials to air flow at elevated temperatures in rotating and heated drying drums, evaporating residual water and constituents volatile at the conditions. Conventional drying systems apply a so-called high-temperature drying, whereas alternative drying methods make use of indirect drying by means of superheated steam using a fluidized-bed method.

Additionally, the materials, whether obtained in step (d) or (e), may be modified by adding functional materials, e.g. additional antimicrobial compounds; colouring or pigmentation, or any other useful modifications, such as shaping or compressing into certain shapes or products, optionally with packaging.

Uses of the Cellulose-Containing Material: The present materials are superabsorbent with an advantageous liquid storage capacity combined with a liquid wicking efficacy. Hence, these super-absorbents are economically viable for use in absorbent articles and are fully biodegradable, so that disposal of the absorbent articles used is environmentally friendly.

The term "absorbent article" generally refers to a device that can absorb and contain fluids. As used herein, absorbent articles include baby sanitary products such as diapers, baby wipes, bowel training pants and other disposable garments; Feminine hygiene products such as sanitary napkins, wipes, sanitary pads, pantiliners, panty shields, tampons and tampon applicators; Adult sanitary products such as wipes, pads, incontinence products, urine shields, furniture pads, bed pads and head bands; Public, industrial and household products such as wipes, covers, filters, paper towels, bath tissues and facial tissues; Nonwovens, such as nonwoven rolls; Home comfort products, such as pillows, pads, cushions and masks; And professional and consumer hygiene products, including but not limited to surgical drapes, hospital gowns, wipes, wraps, covers, bands, filters and disposable garments.

Preferred or alternative features of each aspect or embodiment of the invention apply mutatis mutandis to each aspect or embodiment of the invention (unless the context demands otherwise).

The term "comprising" as used herein means consisting of, consisting essentially of, or including and each use of the word "comprising" or "comprises" can be independently revised by replacement with the term "includes", "consists essentially of or "consists of" . Any modifications and/or variations to described embodiments that would be apparent to one of skill in art are hereby encompassed. Whilst the invention has been described herein with reference to certain specific embodiments and examples, it should be understood that the invention is not intended to be unduly limited to these specific embodiments or examples.

The absorbent materials according to the invention, optionally modified, advantageously may be used in wound dressing, sanitary pad, a tampon, an intrinsically antimicrobial absorbent dressing, a diaper, toilet paper, a sponge, a sanitary wipe, food preparation surfaces, gowns, gloves, surgical scrubs, sutures, needles, sterile packings, floor mats, lamp handle covers, burn dressings, gauze rolls, blood transfer tubing or storage container, mattresses, applicators, exam table coves, head covers, cast liners, splint, paddings, lab coats, air filters for autos, planes or HVAC systems, military protective garments, face masks, devices for protection against biohazards and biological warfare agents, food packaging material, and other materials that would profit from biodegradable and antimicrobial properties.

In connection with the care and treatment of wounds, the term "wound" is meant to include burns, pressure sores, punctures, ulcers and the like. For a long time, one critical aspect of wound care has been the consideration of the requirements of the epithelium, i. e., that area of new cell growth directly peripheral to the wound which is formed during the healing process, so that healing is facilitated.

The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The description that follows more particularly exemplifies illustrative embodiments.

The present invention is now further described with reference to the following non-limiting example.

Example 1: Sugar-beet pellets obtained from a sugar extraction process were subjected to a milling step in an attritor mill, selecting a composition comprising at a weight average particles size of from 100 pm to 300 pm, and subsequently subjected to a water washing and drying step, to obtain a cellulose-containing microporous superabsorbent composition.

Example 2:

Water Absorption Capacity (WAC) Water Absorption Capacity (WAC) was determined as follows: Material samples were weighed out in centrifuge tubes, with a minimum sample weight of 0.5g. Distilled water was added to each sample until it was completely wet. The tubes were then centrifuged at 4000 RPM for 10 minutes.

Following completion of centrifuge, the supernatant was discarded and swollen sample weighed, using the following calculation: WAC = (Ssw-Sw)/Sw, wherein Sw= Sample weight and Ssw= Swollen sample weight.

Raw Cellulose of Example 1 Sample weight = 0.7781 Swollen sample weight= 5.2969 WAC = 5.81 Generally, the cellulose active material particles according to the invention were found to have a WAC in the range of from 2 to 10.

Example 3: Antiviral Efficacy The antiviral activity of the materials were evaluated by the protocol of ISO 18184:2019.

Formulations comprising cellulose active material were tested for their viricidal activity against Influenza A virus or Human coronavirus NL63 at a contact time of 2 h relative to a reference control, following 15018184:2019. The formulations tested were cellulose-containing microporous superabsorbent composition of Example 1. The results are shown in Tables land 2.

Table 1: Effect against Influenza A. A value of 2.0> My a0 indicates good antiviral effect. A value of 3.0> Mv 2.0 indicates very good antiviral effect. A value of Mv 3.0 indicates excellent antiviral effect. *Affected cell susceptibility not valid for 15018184.

Cellulose form vs Influenza A ThIlNlj % reduction Mv (antiviral Cytotoxic Affects cell ISO activity) sensitivity compliant Raw cellulose (milled, not washed) 99.9 3.17 N Y N* Water processed Cellulose 99.9 3.63 N V N* Table 3: Effect against Influenza A. A value of 2.0> My:1.0 indicates good antiviral effect. A value of 3.0> My 2.0 indicates very good antiviral effect. A value of My 3.0 indicates excellent antiviral effect.

Cellulose form vs Human Coronavirus [NL63] % My (antiviral Cytotoxic Affects cell ISO compliant reduction activity) sensitivity Raw cellulose (milled, not washed) 99.9 3.53 N N Y Water processed nanocellulose 99.9 3.16 N N Y As can be seen from Tables all the cellulose materials exhibited good to excellent virucidal activity with a 99.9% reduction in viral titre (both influenza A and human coronavirus) at a contact time of 2 h relative to a reference control, as determined by an 15018184:2019 procedure. Under these conditions the were ISO compliant except raw and washed cellulose samples since although they had potent antiviral activity, they were found to slightly influence growth of the type of cells used in the influenza assay.

Claims (10)

1. Claims 1. A process for preparing a cellulose-containing microporous superabsorbent composition from a herbaceous plant material, the process comprising the step of: a) comminuting dry granulated herbaceous plant material to form microparticles having an average particle diameter of from 100 pm to 800 pm; optionally, b) contacting the microparticles with an aqueous solution; optionally comprising an alkaline reagent; neutralising the mixture, and/or washing the aqueous solution; and removing at least part of the fluids from the mixture, and optionally, drying the obtained material; to obtain the cellulose-containing microporous superabsorbent composition.
2. 2. The process according to claim 1, wherein the starting material comprises less than 20 wt.% lignin.
3. 3. The process according to claim 1 or claim 2, wherein the superabsorbent composition has a water absorption capacity (WAC) in the range of from 2 to 10.
4. 4. The process according to any one of the previous claims, wherein the plant material is selected from root vegetables including carrot, sugar beet, turnip, parsnip and swede; fruit materials including apples, pears, citrus and grapes; and/or tubers, including potato; sweet potato, yam, rutabaya and yucca root; preferably sugar beet.
5. 5. The process according to claim 4, wherein the material comprises sugar beet (beta vulgaris) materials obtained after the sugar juice extraction step; orange peels or apple residue obtained from pressing of juice; and wherein the materials are subjected to washing to remove any non-plant material debris or contaminants and leaves; then pressing of the juice, and washing and cutting up into chips having a thickness in the range of from 0.2 to 0.5 cm; and optionally extracting sugar or volatiles from the chips, by contacting the chips with an extractant.
6. 6. The process according claim 1, further comprising a step (c) of modifying and/or shaping the materials obtained in step (b) or step (a).
7. 7. A cellulosic superabsorbent material obtainable by the process according to claim 1 to 6 comprising a fluid-superabsorbent volume area able to absorb of from 3 to 6 times of the original weight within 30 seconds, and exhibiting a virucidal activity as expressed by a reduction in viral titre of influenza A and/or human coronavirus of above 90%, as determined pursuant to 15018184:2019.
8. 8. The material according to claim 7, for use in absorbing fluids, preferably in absorbing aqueous fluids, menses, bodily fluids, skin, cosmetic compositions, wound exudates, and/or oil spills.
9. 9. The material according to claim 6, wherein the material is shaped into, or comprised in a wound dressing, a sanitary pad, a tampon, an absorbent dressing, a diaper, a sponge, a sanitary wipe, isolation and surgical gowns, gloves, surgical scrubs, sutures, sterile packaging, floor mats, burn dressings, mattress cover, bedding, air filters for autos, planes or HVAC systems, military protective garments, face masks, devices for protection against biohazards and biological warfare agents, lumber, paper, cardboard, meat or fish packaging material, apparel for food handling, and other surfaces required to exhibit a non-leaching antimicrobial property and to release over time portions of biologically or chemically active compounds, or as a particulate matter for absorbing spilled fluids.
10. 10. A functionalised superabsorbent composition comprising: i) a material according to claim 5; and ii) an antimicrobial, colouring or otherwise functional agent selected from antibiotics, analgesics, anti-inflammatories, oxidizing agents, metalloproteinase inhibitors, proteins, peptides, and fragrances adhered to the material.