Absorbent materials

Abstract

The invention provides absorbent articles which are formed from or which incorporate a cellulose / alginate-containing material, wherein said material comprises cellulose fibres and a residue of alginate from a brown seaweed, and wherein said material is obtained by a process comprising at least the following steps: (i) providing a brown seaweed, or part thereof; (ii) dividing the brown seaweed, or part thereof, into a plurality of portions; (iii) washing the plurality of portions with water whereby to remove water-soluble components and recovering the residual solids; (iv) extracting alginate from the residual solids and recovering a residual wet residue comprising cellulose fibres and a residue of alginate; and (v) de-watering the residual wet residue whereby to provide said cellulose / alginate-containing material as a dry residue.

Description

[0001] Absorbent Materials

[0002] Field of the invention

[0003] The present invention relates to absorbent materials and to absorbent products which incorporate or are formed from such materials. It further relates to methods for the production of such materials and to their use as absorbents in applications that require the absorption and retention of aqueous fluids.

[0004] More specifically, the invention relates to absorbent materials obtained from brown seaweed and to products, such as consumer articles, made from such materials. The absorbent materials are capable of the uptake and retention of water and other aqueous fluids, in particular saline solution.

[0005] Advantageously, the absorbent materials are obtained from by-products produced in the commercial extraction of alginate from brown seaweed or are derived from such by-products. They are also biodegradable.

[0006] Background of the invention

[0007] Absorbent materials are capable of imbibing and holding onto aqueous fluids and may absorb many times their own weight in water or other aqueous fluids, for example saline solution. Such materials are used in a wide range of applications, for example to absorb and retain bodily fluids and exudates in absorbent textile materials, for liquid or moisture absorption in food packaging, and as water retention agents in agriculture and horticulture.

[0008] Cellulose-based materials have long been used for the absorption of water and other aqueous fluids. These include fluff pulps which are generally based on Kraft pulping and optimised for high bulk and absorbency. Kraft fibres, produced by chemical pulping of wood chips, are capable of absorbing between 5 and 10 times their mass of water. The pores left behind by the breakdown and dissolution of the lignin during pulping and bleaching gives rise to extensive porosity which allows the materials to take up liquids via capillary action. However, Kraft fibres suffer from a key deficiency in that the wet Kraft fibres have low retention capacity, especially when pressure is applied. In recent decades, this has led to the increased use of superabsorbent polymer (SAP) materials (also known as “hydrogels”), such as sodium polyacrylate. Such materials have reported absorbency levels in the hundreds of grams of water per gram of SAP and are able to provide significant resistance to the release of fluid on compression. Hydrogels that can accommodate more water than 10 g / g are commonly referred to as “superabsorbents”. The ability of SAP materials to swell and restrain liquids to a remarkable extent has led to their widespread use in disposable diapers and in related products, such as other sanitary hygiene products.

[0009] Hybrid products combining cellulosic fibres with SAPs are well known. Within such products, the cellulosic fibres (i.e. the fluff pulp) are used primarily to provide structure (i.e. integrity) and wicking. Although these fibres can accommodate some liquid, most of the absorption capacity of such products is attributed to the inclusion of SAPs such as sodium polyacrylate.

[0010] Hybrid products combining cellulosic fibres with superabsorbent polymer (SAP) materials, such as sodium polyacrylate, are well known. Within such products, the cellulosic fibres (i.e. the fluff pulp) are used primarily to provide structure (i.e. integrity) and wicking. Although these fibres can accommodate some liquid, most of the absorption capacity of such products is attributed to the inclusion of SAPs such as sodium polyacrylate.

[0011] There remains a need for alternative absorbent materials. In particular there is a need for such materials that are not only biodegradable and which can be produced sustainably from renewable resources, but which can absorb and retain bodily fluids containing electrolytes such as NaCI.

[0012] Summary of the invention

[0013] The inventors now propose that the seaweed residue remaining after alginate extraction from brown seaweed can be processed to produce materials that contain both cellulose fibres and a residue of alginate (referred to herein as “cellulose I alginate-containing materials”) and which are capable of the absorption and retention of water and other aqueous fluids. Advantageously, such materials are produced from a product which traditionally has been considered a waste material in the production of alginate. The extent of re-hydration and, in particular, retention capacity of such materials is unexpected, particularly in the presence of electrolytes such as sodium chloride. This makes the materials suitable for use as an alternative to conventional cellulosic fibres (i.e. fluff pulp) in a wide range of potential applications that require the uptake and retention of fluids, such as in the production of personal hygiene products and in packaging materials for the food industry, such as meat soaker pads.

[0014] Brown seaweed is a source of a wide range of commercially useful products such as alginate. The native alginate present in seaweed has a high molecular weight and contains multi-valent cations, both of which render it insoluble in water. In the commercial production of alginate, it must therefore be extracted from the seaweed in a multi-stage process which involves treatment in acid solution, typically hydrochloric or sulphuric acid, to convert the native alginate to alginic acid followed by treatment with sodium carbonate to convert the insoluble alginic acid to water soluble sodium alginate. Treatment with sodium hydroxide at high pH (typically pH 11 or higher) and heat is also generally required to facilitate limited hydrolysis of the alginate chains to reduce their molecular weight to the point where they become soluble. The result of the process is a viscous fluid which requires ‘thinning’ (e.g. by dilution in water) to allow separation of the soluble alginate from the remaining seaweed residue. The dissolved alginate is then recovered from the aqueous solution, for example by adding acid to precipitate alginic acid, by adding a calcium salt to precipitate calcium alginate (from any alginate fragments that contain G- blocks), or by adding an anti-solvent such as ethanol.

[0015] After the extraction of alginate from brown seaweed, an insoluble seaweed residue remains. This is generated in large quantities when alginate is extracted on an industrial scale and contains insoluble cellulose and other polysaccharides, in addition to some remaining (i.e. non-extracted) alginate (also referred to herein as “residual alginate” or “residues of alginate”). Any remaining alginate must be removed by hydrolysis (e.g. by treatment of the seaweed residue with 5% sodium hydroxide at 80°C) before the residue can be further processed to isolate the cellulose. This process is energy intensive and may not always be commercially viable. In most cases, the seaweed residue remaining after any industrial alginate extraction process is considered to be of low commercial value and is treated as a waste material which is disposed of without attempting recovery of the cellulose. As a low-value by-product it is typically pumped back into the sea or dumped as land-fill.

[0016] It has now been found that the seaweed residue remaining after alginate extraction from brown seaweed has useful properties. Once the wet seaweed residue has been further processed to remove most of the water, a dry cellulose I alginate- containing material is provided which is capable of the absorption and retention of water and other aqueous fluids. This property, which has not previously been recognised, makes the material suitable for use as an absorbent. The extent of hydration and fluid retention of the material is unexpected. Pure cellulose fibres, once dried, do not re-swell to any significant degree on contact with a liquid, even once the cellulose has been fibrillated (any small degree of re-swelling may be considered to arise from capillary forces). That a dried cellulose residue obtained from brown seaweed and from which all extractable alginate has been recovered can be re-hydrated not only by water but also by a saline solution is surprising.

[0017] As disclosed herein, the inventors therefore propose the use of the ‘by-product’ from an alginate extraction process, or materials produced from this ‘by-product’, as an absorbent, for example as a replacement for cellulosic fibres such as Kraft fluff pulp in a wide range of potential applications.

[0018] Although not wishing to be bound by theory, the inventors postulate that the residues of alginate remaining in the seaweed residue after the extraction of alginate form part of a network structure in which alginate polymers and cellulose fibres are closely entangled, inter-twined or covalently bound. The presence of cellulose imparts a structural integrity to the material. The presence of residual alginate entangled or inter-twined with the cellulose fibres is thought to allow the cellulose fibres, once dried, to take up and bind an aqueous liquid via osmosis without the need for any further functionalisation, such as micro- or nano-fibrillation, which is generally required to enable pure cellulose fibres obtained from seaweed (i.e. from which all native alginate has been removed) to re-swell by capillary uptake of a liquid, once the cellulose has been dried. The ability of the dried seaweed residue to re-swell on contact with an aqueous liquid and to retain the liquid makes it suitable for use in a wide range of applications in which the uptake of free liquid is desirable. Such applications are described herein and include, but are not limited to, wound dressings (to absorb wound exudate), baby diapers (nappies), feminine hygiene products (sanitary pads, tampons, etc.), incontinence pads, and packaging materials for foods such as fresh or frozen meat or fish, and fruit.

[0019] Detailed description of the invention

[0020] The invention generally relates to absorbent cellulose I alginate-containing materials obtained from brown seaweed. As used herein, the term “absorbent” means capable of imbibing and holding onto an aqueous fluid.

[0021] The materials are either by-products from a commercial production process in which alginate is extracted from brown seaweed (either from the whole seaweed or from a part of the seaweed), or the materials are derived from such by-products by further processing steps such as, but not limited to, drying and / or size reduction. The cellulose I alginate-containing materials comprise cellulose fibres and residues of alginate and are obtained, obtainable, or directly obtained by a process as herein described. For use as absorbents, such materials are generally provided in dry particulate form.

[0022] Based on their absorbent properties, the materials herein described find use in the production of absorbent products. Such products are generally referred to herein as “absorbent articles”. The term “article” is used herein to define an object which has a given shape, surface or design which determines its function.

[0023] In one aspect, the invention thus provides an absorbent article comprising an absorbent cellulose I alginate-containing material, wherein said material comprises cellulose fibres and a residue of alginate from a brown seaweed, and wherein said material is obtained by a process comprising at least the following steps:

[0024] (i) providing a brown seaweed, or part thereof;

[0025] (ii) dividing the brown seaweed, or part thereof, into a plurality of portions; (iii) washing the plurality of portions with water whereby to remove water- soluble components and recovering the residual solids;

[0026] (iv) extracting alginate from the residual solids and recovering a residual wet residue comprising cellulose fibres and a residue of alginate; and

[0027] (v) de-watering the residual wet residue whereby to provide said absorbent cellulose I alginate-containing material as a dry residue.

[0028] As used herein, the term “dry residue” refers to a residue having a water content of less than about 20 wt.%, preferably less than about 15 wt.% (based on the total weight of the dry residue). In some embodiments, the dry residue will have a water content of from 1 wt.% to 20 wt.%, preferably from 5 wt.% to 15 wt.%, more preferably from 10 to 12 wt.%, for example about 10 wt.%. Water content may be determined by any method known in the art, for example the method described herein in the examples.

[0029] The absorbent article may be formed from the absorbent cellulose I alginate- containing material or it may incorporate the absorbent cellulose I alginate- containing material.

[0030] In one embodiment, the absorbent article has a structure which serves to retain the absorbent material. The absorbent cellulose I alginate-containing material may, for example, be dispersed, embedded or otherwise attached to the structure to form the article.

[0031] In one embodiment, the absorbent article is formed from the absorbent material. In this embodiment, the absorbent cellulose I alginate-containing material may be formed, shaped or moulded to form the article.

[0032] In one embodiment, the absorbent article is a consumer article which in use is intended to absorb and retain an aqueous fluid, for example water or a bodily fluid. In one embodiment, the absorbent article will be a disposable absorbent article. By “disposable” it will be understood that the article is intended to be single use.

[0033] As a result of the process used in its production, the absorbent cellulose I alginate- containing material will be provided in particulate form. Depending on its intended use, the particle size of the material may be adjusted. In some embodiments, the process for production of the absorbent material may additionally comprise further processing of the dry residue to reduce its particle size. The need for any further reduction in particle size, or the extent of any such reduction, will depend on the intended end use of the absorbent material and the extent of size reduction that has already been carried out to produce the plurality of portions in step (ii) of the process. Methods suitable for reducing the particle size of the dry residue are well known in the art and can readily be selected, but include milling and / or grinding, for example.

[0034] The process herein described may be performed in respect of any brown seaweed, or any part (or parts) thereof, that contains alginate.

[0035] As used herein, and unless otherwise specified, the term “alginate” is broadly used to refer not only to alginic acid salts (which may be referred to in the art as “alginates”), but to any other derivative of alginic acid and alginic acid itself. As noted herein, alginic acid is a polysaccharide consisting of blocks of (1 -4)-linked - D-mannuronate (M), a-L-guluronate (G), and blocks having an alternating structure (MG). Any reference herein to “native insoluble alginate” is intended to refer to alginate in its naturally occurring form, in particular calcium alginate. Where reference is made to a “soluble alginate”, it will be understood that this refers to a soluble form, for example the soluble sodium form. It may, however, also refer to any other mono-ion form that is soluble such as potassium alginate or ammonium alginate. As will be understood, any reference herein to a “soluble alginate” refers to an alginate that is soluble in water. An “insoluble alginate” will be understood to refer to an alginate that is insoluble in water, such as an insoluble salt of alginic acid with a multi-valent cation, such as calcium or aluminium. Typically, the native insoluble alginate will comprise calcium alginate. Examples of soluble alginates include sodium alginate, potassium alginate and ammonium alginate. Typically, the soluble alginate will be sodium alginate. Any “soluble” form of alginate that is not intimately entangled or inter-twined with cellulose may also be referred to herein as “extractable alginate”, i.e. it can be extracted from the seaweed by direct solubilisation. Examples of brown seaweeds (i.e. Phaeophyceae) that contain alginate and which may be employed in the process herein described include, but are not limited to, those selected from the group consisting of Laminaria spp., Fucales spp., Ascophyllum spp., Durvillaea spp., Ecklonia spp., Lessonia spp., Macrocystis spp., Sargassum spp., and Saccharina spp.

[0036] Examples of particular species of brown seaweed that find use in the invention include, but are not limited to, Laminaria hyperborea, Laminaria digitata, Lessonia trabeculata, Lessonia flavicans, Lessonia brasiliensis, Lessonia nigrescens Saccharina latissima, Saccharina japonica and Fucus serratus.

[0037] Laminaria spp. are particularly suitable, such as Laminaria hyperborea and Laminaria digitata, in particular Laminaria hyperborea.

[0038] The process described herein may be carried out in respect of fresh, frozen or dried brown seaweed or any part thereof that contains alginate. By “fresh”, it is intended that the seaweed or part thereof has not dehydrated to any appreciable extent following harvest. Alternatively, following commercial harvesting, the seaweed or any part (or parts) thereof may be dried. For example, it may be air dried at ambient temperature or at an elevated temperature. Following drying, it may be shredded or flaked to produce a material which can be stored prior to processing as herein described. Any dried seaweed material may be re-hydrated prior to subjecting it to a process as herein described. Alternatively, contact with water in the washing step may be used for the purpose of re-hydration.

[0039] Brown seaweed typically comprise three distinct morphological parts or sections: the leaf (also known as the “frond” or “blade”), the stipe (a ‘stem-like’ structure), and the haptera (a ‘root-like’ structure which anchors the seaweed to the ocean floor and which is also sometimes referred to as the “holdfast”). These parts are different in terms of their physical properties and chemical composition. Harvesting methods involve cutting of the stipe close to the holdfast. Following harvesting, the leaf and stipe will typically be separated from one another to form the different “parts”. Whilst the process herein described may be performed in respect of the whole seaweed (i.e. the stipe and leaf), typically it will be carried out in respect of one or more separated parts. Alginate is located in the structural tissues of the stipe of brown seaweed, for example in the stipe of Laminaria hyperborea. In the commercial production of alginate, it is the stipe which is generally used in order to maximise the alginate yield. In one embodiment, the process will be performed on the stipe of the seaweed. The seaweed part which is used in the process may therefore comprise substantially only the stipe. Use of the stipe of Laminaria hyperborea is particularly preferred. Alternatively, the process may be performed on the leaf of the seaweed, or on part of the leaf. Where part of the leaf is used, this will generally be the thickest part taken from the base of the leaf. Use of the leaf, or any part of the leaf, of Laminaria hyperborea is preferred. Alternatively, the process may be performed in respect of the whole seaweed, for example a combination of both the stipe and the leaf.

[0040] Epiphytes are organisms that grow on the surface of brown seaweed in the marine environment. These include other species of algae, bacteria, fungi, sponges, bryozoans, ascidians, protozoa, crustaceans, molluscs and other sessile organisms. It may be beneficial for these to be removed (or substantially removed) prior to use of the seaweed, or any part of the seaweed, in the process as herein described. Where it is desirable to remove epiphytes from the surface of the seaweed or part thereof, any conventional method may be used. For example, these may be removed by high pressure water washing. In some embodiments, however, the epiphytes need not be removed. The seaweed, or part thereof, which is used in the process may therefore carry epiphytes on its surface.

[0041] The stipe of the seaweed may be selected for use in the process of the invention due to its higher alginate content and / or the higher G-content of the alginate. The stipe may be substantially cylindrical and comprises three distinctive regions defined based on their radial distance from the centre axis of the stipe. The radially inner portion comprises a core region of the stipe referred to as the “inner core”; the radially intermediate portion surrounding the core comprises a tissue region referred to as the “outer core”; and the radially outermost portion comprises a protective surface layer which may be referred to as the “outer layer”. This outer layer may also be referred to as the “bark”, “peel” or “skin” of the stipe. The stipe may be processed to remove some or all of its outer surface layer prior to processing as herein described. However, in one embodiment, it need not be removed. For example, stipe which has not been subjected to any chemical or physical process to remove the outermost surface layer, i.e. in which the outer layer remains substantially “intact”, may be used in the process. Such a stipe may be referred to as “unpeeled” stipe. In one set of embodiments, therefore, the seaweed for use in the process may be whole seaweed (i.e. stipe and leaf) in which the stipe retains the outer surface layer, or stipe which has been separated from the leaf but which still retains the outer surface layer. In one set of embodiments, the unpeeled stipe of Laminaria hyperborea may be used.

[0042] The process herein described may also be carried out in respect of a stipe from which the outermost layer has been substantially removed, i.e. “peeled” stipe. In an embodiment, the process may therefore comprise the step of removal of an outwardly facing surface layer from the stipe or sections of stipe which contains unwanted pigments such as polyphenols. The outwardly facing surface layer for removal will comprise at least the epidermis layer and may additionally comprise the meristoderm layer. Typically, the outwardly facing surface layer that is removed will include at least the epidermis and meristoderm layers. Removal of the surface layer may be carried out using any method known in the art. For example, it may be removed by a chemical stripping process or by a mechanical method. Mechanical methods include peeling, abrasion or scraping. These may be done manually (i.e. by hand) but more typically will be carried out using an automated machine such as a peeling and / or abrading machine known in the art for peeling and / or abrading vegetables. Suitable peeling methods are described in WO 2015 / 067971 , the entire contents of which are incorporated herein by reference. The thickness of the outwardly facing surface layer of the stipe to be removed will be dependent on the type, age and thickness (i.e. diameter) of the macroalgae but can readily be determined by those skilled in the art in order to ensure that substantially all of the pigment-bearing outer layer has been removed. The outwardly facing surface layer of the stipe that is removed may have a thickness of at least 0.5 mm, preferably at least 1.5 mm. For example, it may have a thickness in the range of from 0.5 mm to 2.5 mm. Prior to processing the seaweed, or part thereof, to extract alginate, the seaweed, or part thereof, will be reduced in size in order to increase its surface area and thus improve the efficiency of the washing and extraction process. This is step (ii) of the process as herein described. The method used to divide the seaweed, or part thereof, into a plurality of portions, for example a plurality of stipe or leaf portions, is not of particular importance and any known method may be used to reduce the size of the material. For example, the seaweed or part thereof (e.g. the stipe or the leaf) may be divided by any combination of cutting, chopping, blending, and milling. If appropriate, it may be cut into smaller sections (for example, by cutting or chopping) prior to blending or milling. This may be useful to aid in handling of the material during any subsequent step of blending or milling.

[0043] In one embodiment, in step (ii), the seaweed or part thereof may be divided into a plurality of portions by cutting or chopping. Cutting or chopping may be appropriate to reduce the size of the seaweed, or part thereof, into smaller portions. For example, the stipe may be cut into lengths of from 5 to 100 mm, for example 5 to 10 mm.

[0044] The cut portions of the seaweed or part thereof may be passed directly to the washing stage of the process. In this case, further size reduction of the material may be performed during the washing step, for example by wet milling or blending. Alternatively, the cut portions may be further reduced in size prior to washing. In one embodiment, in step (ii), the seaweed or part thereof may thus be divided into a plurality of portions by cutting followed by milling. Milling may be carried out using any conventional milling machine known in the art. If desired, milling may involve more than one milling stage involving the use of progressively finer screens to provide the desired particle size. Milled portions may have a particle size ranging from 0.1 mm to 10 mm, preferably from 1 mm to 5 mm, e.g. from 1 mm to 2 mm.

[0045] In step (iii) of the process herein described, the plurality of seaweed portions (e.g. the stipe and / or leaf portions) are subjected to water washing in order to remove water-soluble components (such as unwanted salts and other low molecular weight components) prior to carrying out alginate extraction. Washing of the plurality of seaweed portions is carried out by contacting the portions of seaweed with water. Deionised or demineralised water may be used for this purpose, but it is generally preferred that potable water (containing calcium ions) or seawater is used in order to reduce the loss of any low molecular weight “G” bearing alginate from the material.

[0046] Water washing may be carried out by adding the plurality of seaweed portions, for example dried or wet flakes, to water, stirring and allowing to stand. In some embodiments, the seaweed portions may be further reduced in size during water washing, for example by methods such as blending or wet milling. Washing may be carried out in a continuous or batch-wise process. Multiple water washing steps may be conducted in which water is removed from the solid-liquid mass at the end of each washing step, the solid seaweed residue is collected and transferred to the next washing stage.

[0047] The temperature of the water used for washing and duration of washing may readily be selected by those skilled in the art and will take account of the type of seaweed, whether the seaweed portions are obtained from the whole seaweed, or from the stipe or leaf, the number of washing steps, etc. Lower temperatures and / or shorter treatment times are generally preferred to reduce the energy requirements of the process and may be appropriate for washing of stipe portions, for example. Where any leaf portions are present, for example when processing the seaweed as a whole or the separated leaf, a higher washing temperature will generally be required to effectively remove the fucoidan.

[0048] For stipe, the water washing step may conveniently be conducted at ambient temperature, i.e. at 18 to 25°C. The duration of water washing may range from 10 to 60 minutes, for example it may be about 30 minutes.

[0049] In the case of leaf (or whole seaweed where leaf parts are present), the water washing step may conveniently be conducted at a temperature in the range of 30 to 70°C, preferably 50 to 70°C, for example about 60°C. The duration of water washing may range from 10 to 60 minutes, for example it may from 30 to 60 minutes, for example about 30 minutes. Hot water washing will generally be followed by a cold water wash, for example by washing of the material at ambient temperature, i.e. at 18 to 25°C. The duration of any cold water wash may range from 10 to 60 minutes, for example it may be about 30 minutes and may be repeated as required.

[0050] Washing may be carried out until the conductivity of the water which is removed is sufficiently reduced and indicative of the removal of a sufficient amount of unwanted salts from the material. A conductivity of less than about 200 pS may, for example, be appropriate. If necessary, multiple washing steps may be performed.

[0051] In one embodiment, the wash solution removed from the solid-liquid mass at the end of each washing step may be collected and processed to recover one or more water-soluble components. For example, one or more of fucoidan, laminarin and mannitol may be recovered. Methods for the recovery of such substances are well known in the art and include, but are not limited to, ultrafiltration and spray-drying. Typically, recovery might be performed by carrying out ultrafiltration followed by spray-drying. Advantageously, by recovery of water-soluble components from the wash solution, the process herein described provides a biorefinery process in which multiple components can be obtained from the original biomass.

[0052] Following the washing step (or final washing step), the material may be processed to remove excess water prior to further processing as described herein to extract alginate from the residual solids. Excess water will typically be removed by mechanical methods such as centrifugation. A horizontal centrifuge may, for example, be used.

[0053] Any conventional alginate extraction method may be employed as part of the process herein described. This is step (iv) of the process. The aim is to convert the insoluble native alginate present in the seaweed material into a soluble form. The solubilised alginate can then be separated from the solid residue and recovered.

[0054] As herein described, it is envisaged that the absorbent materials will primarily be produced as a by-product in the commercial extraction of alginate from brown seaweed or by further processing of this by-product. In most cases, it will therefore be of primary commercial importance to maximise the yield of alginate in performing the extraction process. Alginate yield will vary depending on factors such as the type of brown seaweed, the part (or parts) of the seaweed employed, the processing steps used to treat the seaweed and perform the alginate extraction. Harsh treatment and extraction conditions may, for example, increase yield whilst producing alginate having a lower molecular weight. As will be understood, in the context of any commercial process it will simply not be viable to extract all alginate from the seaweed due to the additional cost involved in performing multiple extractions. Typically, a maximum of two cycles of alginate extraction might be performed in any commercial process. Thereafter, it is not commercially viable to attempt to extract further alginate since the additional yield is minimal.

[0055] Step (iv) of the process herein described involves extracting alginate from the residual solids. As used herein, the term “extraction” is intended to refer to the conversion of the insoluble alginate salts and / or alginic acid present in the residual solids and its recovery (i.e. separation) from the residual solid residue of the seaweed. In one embodiment, step (iv) involves extracting substantially all extractable alginate from the residual solids. This is intended to mean that substantially all alginate that can be extracted by commercially viable means when performing any chosen extraction method will be removed from the residual solids, i.e. it is the intention that most of the alginate which is in extractable form will be separated from the seaweed residue and recovered.

[0056] The yield of alginate (i.e. the amount of alginate extracted) may be quantified in terms of the loss of dry matter following the step of alginate extraction. The “loss of dry matter” is the difference in the dry matter content of the washed seaweed material (i.e. following removal of salts and other water-soluble components in accordance with step (iii) of the process as herein described) and the dry matter content of the residual seaweed material following alginate extraction (i.e. following completion of step (v) of the process as herein described). In some embodiments, the extraction step of the process will result in a loss of dry matter of at least about 15%, preferably at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45% or at least about 50%.

[0057] In one embodiment, the alginate extraction method will involve conversion of the native insoluble alginate into soluble sodium alginate and employ an alkaline treatment step. Typically, the seaweed will be treated with mineral acid before alkaline extraction of alginate. Treatment with a dilute mineral acid is considered to make the alginate more readily soluble in an alkaline solution. Acidification of the seaweed may also have the advantage of removing salts and other non-target compounds such as polyphenols and other polysaccharides such as fucoidans and laminarins. Step (iv) of the process may thus comprise an acid cation exchange step in which the residual solids produced in step (iii) are contacted with an aqueous solution of a mineral acid whereby to convert the native insoluble alginate to alginic acid and form a pre-treated seaweed material, followed by contacting said pre-treated seaweed material with an alkaline solution to convert the alginic acid into a soluble alginate (e.g. to sodium, potassium or ammonium alginate).

[0058] Thus, in one embodiment, an initial metal cation exchange step is employed to convert the insoluble alginate to alginic acid by exchanging metal cations with protons. This is carried out by the addition of a mineral acid which is added to reduce the overall pH of the residual solids, for example to a pH in the range of about 1.5 to about 2, e.g. 1.7 to 1.9. Suitable mineral acids include hydrochloric acid and / or sulphuric acid. Conveniently, the mineral acid will be hydrochloric acid. Alternatively, the mineral acid may be sulphuric acid. The material can be left to stand in the presence of the mineral acid for up to 60 mins, for example up to 30 mins, for example up to approximately 15 minutes. During contact with the mineral acid, the mixture may be agitated (e.g. stirred). In some embodiments, the step of mineral acid treatment may be carried out at elevated temperature, for example in the range of 50 to 70°C

[0059] Following mineral acid treatment, the process will then typically comprise the step of separating the resulting mixture into a solution phase and residual solids. For example, the material may be drained through a filter or transferred to a centrifuge to remove the acid water. The filtrate or the liquid phase from the centrifuge, which is a mineral acid solution, may be collected and if desired can be used in a subsequent metal cation exchange step, thereby improving process efficiency. The obtained solid fraction may be washed with water in one or more washing steps to remove excess mineral acid. The water for use in this part of the process will typically be deionised water in order to avoid the re-introduction of calcium ions. Washing with water is effective to increase the pH of the material, e.g. to a pH in the range of from about 3 to about 5, preferably about 3 to about 4, e.g. about 3.5 to 4, and may be repeated as required. After the washing step (or final washing step), the material is drained or centrifuged to remove as much free water as possible.

[0060] At this point, the native alginate will be present in an insoluble form, i.e. primarily in the form of alginic acid. Calcium alginate residues may also still be present. The next step of the process involves conversion of the insoluble alginate salts and / or alginic acid present in the seaweed to the soluble form (e.g. the soluble sodium form). The solubilised alginate is then separated (e.g. by filtration or centrifugation) from the residual solid components of the seaweed and further processed to recover the alginate. For example, sodium, potassium or ammonium alginate may be recovered, e.g. in dry powdered form.

[0061] The step of extracting alginate will typically comprise contacting the seaweed residue with an alkali whereby to produce solubilised alginate, i.e. it is an alkaline extraction process. As used herein, the term “extraction” is intended to refer to a process that involves solubilisation of the alginate present in the seaweed residue in an insoluble form, typically as calcium alginate. Following extraction, the resulting solution containing the solubilised alginate is separated (e.g. filtered) from the residual solid components of the seaweed residue. Separation of the solution containing the solubilised alginate provides a residual wet residue containing cellulose and ‘non-extractable’ alginate (i.e. alginate residues).

[0062] The alkali may be employed in solid or solution form, but typically may be used in the form of an alkaline solution. Where it is used in the form of a solution this will generally be a saturated solution.

[0063] Typically, the alkaline solution for use in the extraction may be selected from sodium hydroxide, potassium hydroxide, ammonium hydroxide and sodium carbonate. Conveniently, it may comprise carbonate ions, for example it may be a sodium carbonate solution. For example, the step of extracting alginate from the seaweed residue will comprise the use of sodium carbonate and / or sodium hydroxide, preferably sodium carbonate (e.g. a saturated sodium carbonate solution). In one embodiment, sodium hydroxide is used in combination with sodium carbonate to increase the pH, for example to a pH of between 10 and 11. The alkaline solution, for example sodium carbonate, may be employed at a suitable concentration. Preferably, it will be used at a concentration of about 10 to 15%.

[0064] Contact with the alkaline solution may comprise soaking of the seaweed residue in the alkaline solution or it may involve mixing, e.g. high shear mixing, with the alkaline solution. Soaking or mixing may be carried out for a period of about 2 minutes to about 24 hours, for example 30 minutes to 24 hours, for example 30 to 45 minutes. During contact, the pH will increase and may be in range from about 6 to about 10, preferably from about 8 to 10, more preferably from about 9 to about 10. In some embodiments, the alkaline solution is added to effectively neutralise the solid residue, for example to adjust its pH to within the range of about 6 to about 8, preferably about 6 to about 7. If necessary, additional alkali can be added as required. Reaction temperature and reaction time can readily be varied. For example, the reaction temperature may be in the range from 30 to 80°C, preferably 40 to 70°C, e.g. 50 to 60°C. Conveniently, the reaction may be carried out at ambient temperature (18 to 25°C).

[0065] Other methods known in the art for the extraction of alginate from brown seaweed also find use in the production of the absorbent materials herein described. Such methods include those involving pre-treatment of the seaweed prior to conversion of the native alginate into a soluble (i.e. extractable) form which can be extracted and recovered. One such method involves exposing the portions of seaweed to a weak organic acid, such as citric acid, followed by cation exchange with a mineral acid. Treatment with the weak organic acid is effective to reduce the native alginate molecular weight and decolourise the material. Thereafter, the decolourised material is subjected to treatment with a mineral acid whereby to exchange the metal ions present in the alginate structure (e.g. calcium) with hydrogen ions in order to facilitate subsequent extraction. This organic acid pre-treatment process is disclosed in WO 2023 / 281262, the entire contents of which are incorporated herein by reference.

[0066] In one embodiment, step (iv) of the process herein described may comprise the following steps: contacting the residual solids with an aqueous solution of a weak organic acid; recovering the resulting solid fraction; contacting the resulting solid fraction with an aqueous solution of a mineral acid whereby to effect exchange of native calcium ions with hydrogen ions to produce alginic acid; recovering the resulting solid fraction; contacting the solid fraction with an alkali whereby to convert the alginic acid to a water-soluble form of alginate; and separating the water-soluble form of alginate from the solid fraction thereby recovering a residual wet residue comprising cellulose fibres and a residue of alginate.

[0067] As used herein, the term “organic acid” denotes an organic compound which has acidic properties. Organic acids for use in the invention may possess one or more acid groups and include any of the acids disclosed in WO 2023 / 281262. Preferred for use in the invention are any of the following acids: lactic acid, malic acid, tartaric acid, citric acid, ascorbic acid, and glycolic acid. Of these, lactic acid (E270), malic acid (E296), tartaric acid (E334), citric acid (E330), and ascorbic acid (E300) have E-numbers and are generally preferred. Particularly preferred for use in the invention are malic, citric and ascorbic acids. The use of citric acid is especially preferred.

[0068] The precise conditions for any organic acid treatment, such as the concentration of the acid, temperature and duration of treatment, etc. can readily be selected by those skilled in the art. As described in WO 2023 / 281262, by varying the organic acid treatment conditions, the nature of the alginate obtained can be suitably adjusted. For example, the duration of exposure of the seaweed material to the organic acid, its concentration, and the temperature of the organic acid treatment have an impact on the molecular weight of the alginate that is extracted. This, in turn, intrinsically influences the viscosity of the alginate when dissolved in solution. Longer treatment times and / or higher temperatures are effective to reduce the molecular weight and viscosity of the alginate, for example. The use of higher concentrations of the organic acid also reduces the molecular weight (and thus viscosity) of the extracted alginate. Advantageously, the conditions of the organic acid pre-treatment can be adjusted to recover alginate having desired functional properties.

[0069] Typically, the organic acid may be employed in the form of an aqueous solution having a concentration of from 0.1 to 10.0 % w / v, from 0.25 to 5.0 % w / v, from 0.75 to 2.5 % w / v, from 1.0 to 2.0 % w / v, or from 1.0 to 1.5 % w / v, preferably about 1 % w / v. The use of a lower concentration of the organic acid may be preferred when it is desirable to provide an alginate having a higher molecular weight (and thus higher viscosity). Higher concentrations may be appropriate where a lower molecular weight (and thus lower viscosity) of the extracted alginate is desirable and may be selected accordingly. For example, an aqueous solution of the organic acid having a concentration in the range of from 5.0 to 10.0 % w / v, from 6.0 to 10.0 % w / v, or from 8.0 to 10.0 % w / v may be employed.

[0070] The temperature of the organic acid treatment may be selected depending on the desired molecular weight (and thus viscosity) of the extracted alginate. Generally, temperatures up to about 100°C may be employed. However, lower temperatures are generally preferred in order to reduce the overall energy requirement of the process. The use of lower temperatures may also provide a greater degree of control over the organic acid pre-treatment step (and thus its impact on the properties of the extracted alginate). Temperatures in the range from 10 to 100°C, preferably 10 to 50°C, more preferably 15 to 30°C, e.g. 20 to 25°C, may be employed. Advantageously, however, this step of the process will be conducted at ambient temperature, for example in the range from 18 to 25°C. As will be understood, ambient temperature does not require any additional heating.

[0071] Higher temperatures for the organic acid treatment may be appropriate where a lower molecular weight (and thus lower viscosity) of the extracted alginate is desirable and may be selected accordingly. Where higher temperatures are used, these may be in the range from 60 to 100°C, for example from 65 to 100°C, from 70 to 100°C, from 80 to 100°C, from 90 to 100°C, or from 95 to 99°C.

[0072] Duration of the organic acid treatment may be appropriately selected by those skilled in the art. For example, the timing of treatment may range from a few minutes to several hours. As will be understood, the duration for the treatment will be influenced by the selected concentration of the organic acid and the temperature employed in this step of the method. If a low concentration of organic acid is employed, the duration of treatment may for example extend to several days or even weeks. Typically, however, organic acid treatment may be carried out for up to 2 hours, for example up to 1.5 hours, e.g. up to 1 hour. Treatment may be carried out for shorter times, e.g. less than an hour, particularly in cases where elevated temperatures and / or higher concentrations of organic acid are employed. For example, treatment times may be as low as 2 minutes, or as low as 5 minutes. Treatment times may, for example, range from 2 to 60 minutes, or from 5 to 50 minutes, or from 10 to 40 minutes, or from 20 to 30 minutes.

[0073] Appropriate combinations of temperature and duration of the organic acid treatment may be selected by those skilled in the art. For example, treatment at ambient temperature for about 1 hour may be particularly suitable for the production of alginate having a high viscosity, for example a viscosity of greater than 800 cps, greater than 900 cps, greater than 1000 cps, greater than 1500 cps, greater than 1600 cps, greater than 1700 cps, greater than 1800 cps, or greater than 1900 cps. Where a higher temperature is employed, for example about 60°C, a treatment time in the range of about 5 to 10 minutes may be selected to produce alginate having a medium viscosity, for example a viscosity in the range from 400 to 800 cps, and a treatment time of about 30 to 40 minutes may be selected to produce an alginate having a low viscosity, for example a viscosity in the range from 50 to 400 cps. Where an ultra-low viscosity alginate is desired, a higher treatment temperature of up to about 100°C, for example about 95°C to about 99°C, e.g. about 95°C, for a period of about 20 minutes may be suitable. A higher treatment temperature for a period of about 20 to 45 minutes, for example 35 to 40 minutes, may be appropriate to provide an ultra-low viscosity alginate. An ultra-low viscosity may be in the range from 5 to 50 cps. All viscosities referred to herein refer to the viscosity of a 1 wt.% solution of alginate in water at 20°C measured using a Brookfield-type viscometer.

[0074] Selection of the temperature and duration of the organic acid pre-treatment step of the method should take account of the concentration of the organic acid solution that is employed. When using higher concentrations of the organic acid, for example, shorter treatment times and / or lower temperatures may be appropriate in order to provide the desired degree of control in producing an extracted alginate having the required functional properties.

[0075] The extraction process herein described comprises the step of separating the solubilised alginate from the residual solids to provide the residual wet residue comprising cellulose fibres and a residue of alginate. Separation of the solubilised alginate from the residual solids may be carried out by known methods, for example by dilution with water (if necessary) and filtration, for example by centrifugation. These separation steps may be repeated, as desired.

[0076] Alginate can be recovered from any separated sodium (or potassium or ammonium) alginate solution using conventional methods such as the well-known “alginic acid” or “calcium alginate” methods which are described herein. In one set of embodiments, the process herein described further comprises the step of recovering alginate from the solubilised alginate.

[0077] Following step (iv), the residual wet residue which remains contains cellulose fibres in addition to alginate residues, i.e. the residue is a cellulose I alginate-containing material. It may also contain additional components such as proteins and lipids.

[0078] The amount of cellulose in the residue will depend on the seaweed species and the part of the seaweed used in the process. The amount of alginate in the residue will depend on the efficiency of the alginate extraction process employed.

[0079] Initially, the cellulose and alginate-containing material will be produced in the form of a residual wet residue. If necessary, prior to de-watering, this may be treated with a mineral acid in a neutralisation step. For example, it may be treated with hydrochloric acid, for example to reduce the pH to between about 6 and about 8, for example to between about 6.5 and 6.7.

[0080] In step (v) of the process, the residual wet residue is de-watered to provide a dry residue. In some embodiments, the dry residue will have a water content of less than about 20 wt.%, preferably less than about 15 wt.% (based on the total weight of the dried residue). In some embodiments, the dry residue will have a water content of from 1 wt.% to 20 wt.%, preferably from 5 wt.% to 15 wt.%, more preferably from 10 to 12 wt.%, for example about 10 wt.%. Water content may be determined by any method known in the art, for example the method described herein in the examples.

[0081] De-watering of the residual wet residue may be carried out by any conventional method including any mechanical and / or chemical methods such as but not limited to, one or more of the following: mechanical pressing, solvent drying, spray drying, air drying, fluid bed drying, drum drying, vacuum drying and freeze drying. Solvent drying and / or vacuum drying is preferred.

[0082] In one embodiment, the residual wet residue is de-watered by solvent drying. Solvent drying may involve the use of an alcohol solvent such as ethanol, propan-2- ol, or acetone. The use of propan-2-ol is particularly preferred. The use of a solvent, such as propanol, may be beneficial in order to retain an open structure in the final material.

[0083] In certain embodiments, the seaweed residue produced in the process herein described may be processed to further adjust its physicochemical properties prior to its use as an absorbent. For example, fibrillation of the cellulose component may be desirable. Fibrillation methods are well known in the art and will generally be performed in respect of the residue before it is de-watered, i.e. whilst it remains in a wet state. If desired, therefore, fibrillation of the cellulose may be carried out to produce cellulose nanofibrils. In the preparation of nanofibrillar cellulose, cellulose fibres are disintegrated to produce fibrils having a sub-micron diameter. For example, these may have a diameter which is in the nanometer range. Disintegration methods are well known in the art and include mechanical disintegration of the cellulose material in the presence of water. Mechanical disintegration may involve grinding, crushing, or shearing of the fibrous cellulose material or any combination of these. It may be carried out using known equipment such as a fluidizer, high sheer homogenizer (e.g. a microfluidizer), grinder, etc. Disintegration may, for example, be carried out using a homogenizer in which the material is subjected to homogenization under pressure.

[0084] Following fibrillation, the resulting cellulose nanofibrils or nanofibril bundles are characterised by a high aspect ratio (i.e. length : diameter). Their length may exceed 1 pm, but their diameter is in the submicron range, i.e. less than 1 pm. Precise dimensions and size distribution of the nanofibrils or nanofibril bundles will depend on the disintegration (i.e. fibrillation) method and may vary to some extent. Typically, the diameter of the nanofibrils or nanofibril bundles will be on the nanometer scale, for example less than 20 nm. For example, their average diameter may range from 3 to 20 nm, preferably from 5 to 20 nm, e.g. from 5 to 10 nm. Typically, the average length of the nanofibrils or nanofibril bundles will be in the range from 5 to 10 pm. For example, it may be in the range from 1 to 5 pm, e.g 0.5 to 1 pm, or 0.2 to 0.5 pm.

[0085] The step of fibrillation of the seaweed residue as herein described is optional. In one set of embodiments, the process of the invention does not involve any step of nanofibrillation. In one set of embodiments, the process of the invention does not involve any step of fibrillation.

[0086] The resulting dry cellulose I alginate-containing material has the capacity to absorb free liquid making it suitable for use as an absorbent in any application where the uptake of free liquid is desired.

[0087] Even though all available (i.e. extractable) alginate has been removed from the seaweed during processing, the resulting dried seaweed material is capable of absorbing a significant amount of free liquid. As a result of this finding, the process herein described allows for the maximum recovery of alginate from brown seaweed whilst providing a cellulose I alginate-containing residue that can be employed as an absorbent.

[0088] For use in certain applications, it may be desirable for the absorbent material to be free from colour or light in colour. A reduction in colour of the material may be achieved be appropriate selection of the starting material. For example, the use of peeled stipe from which the pigment-containing bark has been removed may be desirable. Alternatively, the seaweed residue may be further treated to remove or to disguise any undesired pigmentation. For example, it may be bleached or additional pigments may be added. Bleaching, or the addition of pigments to the final material, may be desirable when using unpeeled stipe or when using leaf material in the process of the invention, for example. The leaf material is more highly pigmented than the stipe. Where bleaching is desirable, this will typically be carried out on the wet residue that is produced, i.e. prior to any drying or further processing steps. Any bleaching step may involve the use of a bleaching agent. As used herein, the term “bleaching agent” refers to a chemical agent which is capable of lightening or whitening a substrate via a chemical reaction. Typically, a bleaching agent will be one involved in a bleaching reaction which involves an oxidative or reductive process that degrades a colour pigment.

[0089] Examples of bleaching agents include, but are not limited to, any of the following: a compound comprising, or that acts as a source of, peroxide or peroxy acid, for example hydrogen peroxide, peroxide salt, peroxy acid, hydroperoxide, carbonate salt, percarbonate salt, 6-(phthalimido) peroxyhexanoic acid (PAP), peracetic acid; an oxidation catalyst, for example a mononuclear or dinuclear transition metal catalyst (for example manganese) (for example the oxidation catalyst may be selected from one or more groups selected from [(Mnlv)2(u-O)3(Me3-TACN)2]2+, [(Mnlll)2(u-O)(u-CH3COO)2(Me3-TACN2]2+and [MnlllMnlv(u-O)2(u-CH3COO)(Me4- DTNE)]2+and suitable salts thereof; a peroxide activator (i.e. a compound that reacts with a source of a peroxide group to provide a peroxide group), for example tetra acetyl ethylene diamine (TAED); a peroxy acid activator (i.e. a compound that reacts with a source of a peroxy acid to provide a peroxy acid group) for example tetra acetyl ethylene diamine (TAED); hypochlorite; a compound comprising, or that acts as a source of, chlorite; chlorine dioxide; a chlorite salt; and chlorine. Typical bleaching agents include hydrogen peroxide, peroxyacids, persulfates, organic peroxides and hypochlorite. Hydrogen peroxide or sodium hypochlorite is generally preferred.

[0090] An appropriate amount of any bleaching agent may readily be selected depending on the extent of lightening that is required or is desirable. The amount of bleaching agent may range from 1 to 10% by weight, preferably from 3 to 5% by weight (based on the weight of the residue). Bleaching may be carried out at a temperature in the range from 10 to 50°C, preferably from 20 to 30°C.

[0091] The step of bleaching as herein described is optional. In one set of embodiments, the process of the invention does not involve any bleaching step, i.e. the process does not involve the use of any bleaching agent. For example, the process does not involve the step of contacting any of the following materials with a bleaching agent: the seaweed, or part thereof, any of the intermediate products produced during the process, and the final seaweed residue containing cellulose and alginate.

[0092] The resulting dry cellulose I alginate-containing material will be provided in particulate form, for example as a granular material. The material will include a range of particle sizes, i.e. it will be polydisperse. The precise particle size of the material may not be important but can be adjusted depending on the intended use of the material. In certain embodiments, the residue produced in the process of the invention may be further processed to reduce the particle size of the material. Size reduction may be effected by known methods such as, but not limited to, milling and / or grinding. Methods for size reduction of cellulose materials are well known in the art and include, for example, milling (e.g. ball milling, jet milling or wet milling), or grinding. The particle size of the residue will depend on factors such as the method used for size reduction. Generally, the material will have an average particle size in the range from 100 to 1000 pm, preferably 200 to 700 pm, more preferably 250 to 600 pm, e.g. 250 to 500 pm. Particle size can be determined by known methods, for example by “sieve analysis” in which a sample is shaken on a stack of sieves of graduated size (largest at the top and smallest on the bottom). These are weighed empty and then at the end of the test to allow the determination of the mass (and hence %) retained at each level. Industry standards which may be followed are as follows: ISO 19.120 or ASTM 214.

[0093] In one embodiment, the resulting dry cellulose I alginate-containing material will have a free swelling capacity of from 5 to 35 g / g as measured according to the examples when using an aqueous fluid which is 0.9% NaCI dissolved in deionised water. In other embodiments, the material will have such a free swelling capacity of from 7 to 35 g / g, preferably 10 to 30 g / g, more preferably 15 to 30 g / g.

[0094] In one embodiment, the resulting dry cellulose I alginate-containing material will have a retention capacity of from 5 to 35 g / g as measured according to the examples when using an aqueous fluid which is 0.9% NaCI dissolved in deionised water. In other embodiments, the material will have such a retention capacity of from 6 to 30 g / g, preferably 10 to 30 g / g, more preferably 15 to 30 g / g. If desired, alginate can be recovered from any sodium (or potassium or ammonium) alginate solution that is produced as a result of carrying out a process as herein described. Recovery of alginate may be performed using any known method. Suitable methods include the “alginic acid” or “calcium alginate” methods. Such methods are well known and described in the prior art, for example in McHugh (Dennis J. McHugh - Chapter 5 (Alginate) in “A guide to the seaweed industry”, FAO Fisheries Technical Paper 441 , Food and Agriculture Organisation of the United Nations, 2003), the entire contents of which are incorporated herein by reference.

[0095] In the “alginic acid” method, the pH of the solution is adjusted by contacting with a mineral acid such as hydrochloric acid and / or sulphuric acid to form a precipitate of alginic acid. The acid may be employed in an amount and concentration sufficient to reduce the pH of the solution to about 2 or less, preferably between 1.7 and 1.9, whereby to form an alginic acid precipitate. Preferably, hydrochloric acid is used. The alginic acid precipitate is recovered in the form of a gel, for example by centrifugation. The resulting gel may optionally be rinsed with water to remove excess acid and to increase the pH to provide a solution having a pH of about 3.5 to about 4. If desired, the alginic acid gel may then be converted to sodium alginate by the addition of an alkali containing sodium ions, for example by the addition of a sodium carbonate solution. Addition may be carried out with stirring. The amount and concentration of sodium carbonate solution can readily be adjusted but will typically be sufficient to adjust the pH of the solution to between 7.0 and 7.3. To recover the desired alginate product, the resulting solution may be contacted with an anti-solvent, such as an alcohol or mixture of alcohols, or acetone. Suitable alcohols include, for example, propan-2-ol and ethanol. This causes sodium alginate to be displaced from solution as a fibrous precipitate. Subsequently, this precipitate can be removed from the solvent mixture, for example by centrifugation. The anti-solvent can be recovered and recycled, which improves process efficiency. The resulting alginate can then be dried, for example in a vacuum oven, for example at a temperature of up to 100°C, for example up to 95°C, for example up to 85°C, for example up to 50°C, for example up to 30°C, preferably at 30°C. In the “calcium alginate” method, calcium chloride is added to cause calcium alginate to precipitate or to form a gel, which can then be recovered. The pH of the precipitate or gel is then reduced to less than about 2.3 using a mineral acid such as hydrochloric and / or sulphuric acid. The resulting alginic acid precipitate or gel is recovered, for example by centrifugation. This may optionally be rinsed with water to remove excess acid and to increase the pH to provide a solution having a pH of about 3 to about 4. If desired, the alginic acid material may then be converted to sodium alginate by the addition of an alkali containing sodium ions, for example by the addition of a sodium carbonate solution. Addition may be carried out with stirring. The amount and concentration of sodium carbonate solution can readily be adjusted but will typically be sufficient to adjust the pH of the solution to between 7.0 and 7.3. To recover the desired alginate product, the resulting solution may be contacted with an anti-solvent, such as an alcohol or mixture of alcohols, or acetone such as described above for the “alginic acid” method.

[0096] Specific embodiments of the process of the invention are described in more detail with reference to accompanying Figures 1 and 2.

[0097] In Fig. 1 , the process involves obtaining brown seaweed (e.g. Laminaria hyperborea) having stipe and leaf portions and removing the non-stipe portions to provide a seaweed part which consists of stipe only. The non-stipe parts are removed by manual or automated cutting, for example using a cutting machine generally used in the art. The stipe may be washed to remove epiphytes and then further processed intact. Following size reduction (e.g. by cutting and / or milling), the stipe portions are washed to remove salts and other water-soluble components (for example water-soluble sugars). Optionally, the recovered solid fraction is pretreated with citric acid (either at high or low temperature, depending on the desired molecular weight of the extracted alginate) prior to performing alginate extraction. The extraction process is an alkaline extraction and involves mineral acid treatment to effect cation exchange and convert the native insoluble alginate to alginic acid, followed by washing to remove excess mineral acid, then treatment with a sodium- based alkali to convert the alginic acid to sodium alginate. Treatment with the sodium-based alkali may be performed according to current industry standards, i.e. at high temperature (40-70°C) and high pH (pH 9-10) for 2-24 hours. Alternatively, it may be performed under milder treatment conditions such as those described in WO 2023 / 281262 at ambient temperature, lower pH (pH 7.0-7.5) and for a shorter period (2-3 hours). The maximum amount of solubilised (i.e. extractable) alginate is separated by filtration. The solid phase material that remains is a wet mass that contains cellulose fibres and residual (i.e. non-extractable) alginate that remains in the matrix and is present in the soluble sodium form. The pH of the wet residue is reduced to 6.5-6.7 by the addition of a mineral acid, e.g. hydrochloric acid. Following removal of any excess acid, the wet residue is then de-watered, for example using an alcohol such as propanol as an anti-solvent. The material may then be further dried to provide the final cellulose I alginate-containing material in granular form. Following alkaline extraction, the liquid phase is processed to recover alginate in the form of sodium alginate.

[0098] Fig. 2 shows methods for processing of leaf material in accordance with the invention. Leaf material is obtained from seaweed (e.g. Laminaria hyperborea). It contains alginate having a higher “M” content than that present in the stipe. Following separation from the stipe, the leaf material is subjected to size reduction (e.g. by cutting and / or milling). The leaf material is then subjected to water washing at high temperature to remove fucoidan and other water-soluble components (e.g. soluble sugars). The washed leaf portions are then processed in the same way as described above in respect of the stipe portions.

[0099] As a result of the methods used to process the “by-product”, including but not limited to the additional steps of de-watering and / or further size reduction, the materials herein described are considered novel. The invention thus further relates to the absorbent materials obtained as a result of carrying out any of the processes herein described.

[0100] In another aspect, the invention therefore provides an absorbent cellulose I alginate-containing material obtained, obtainable, or directly obtained by any process as herein described.

[0101] Specifically, the invention provides an absorbent cellulose I alginate-containing material, wherein said material comprises cellulose fibres and a residue of alginate from a brown seaweed and is obtained by a process comprising at least the following steps: (i) providing a brown seaweed, or part thereof;

[0102] (ii) dividing the brown seaweed, or part thereof, into a plurality of portions;

[0103] (iii) washing the plurality of portions with water whereby to remove water- soluble components and recovering the residual solids;

[0104] (iv) extracting alginate from the residual solids and recovering a residual wet residue comprising cellulose fibres and a residue of alginate; and

[0105] (v) de-watering the residual wet residue whereby to provide said absorbent cellulose I alginate-containing material as a dry residue.

[0106] In one embodiment, the absorbent cellulose I alginate-containing material is provided in dry, particulate form. In some embodiments, the material may have a water content of less than 20 wt.%, for example less than 15 wt.%. In some embodiments, the material may have a water content in the range of from 1 to 20 wt.%, from 2 to 18 wt.%, from 3 to 17 wt.%, from 4 to 16 wt.%, or from 5 to 15 wt.%, for example about 10 wt.%.

[0107] The absorbent material will generally be provided in particulate form having a range of particle sizes, i.e. it will be polydisperse. Its average particle size can readily be adjusted according to the intended application. In some embodiments, the material may have an average particle size in the range of several mm, preferably from 1 to 5 mm, for example from 2 to 3 mm. In some embodiments, the material may have an average particle size in the range of from 100 to 1000 pm, or from 200 to 800 pm, or from 200 to 700 pm, or from 250 to 600 pm, e.g. from 250 to 500 pm.

[0108] Particle size can be determined by known methods, such as those herein described.

[0109] In one embodiment, the absorbent cellulose I alginate-containing material will have a free swelling capacity of from 5 to 35 g / g in the presence of an aqueous fluid which is 0.9% NaCI dissolved in deionised water and as measured according to the method set out in the examples. In other embodiments, the material will have a free swelling capacity, when measured under these conditions, of from 7 to 35 g / g, preferably 10 to 30 g / g, more preferably 15 to 30 g / g.

[0110] In one embodiment, the absorbent cellulose / alginate-containing material will have a retention capacity of from 5 to 35 g / g in the presence of an aqueous fluid which is 0.9% NaCI dissolved in deionised water and as measured according to the method set out in the examples. In other embodiments, the material will have a retention capacity, when measured under these conditions, of from 6 to 30 g / g, preferably 10 to 30 g / g, more preferably 15 to 30 g / g.

[0111] Due to the absorbent properties of the cellulose I alginate-containing materials produced according to the methods herein described, these find use in a broad range of industrial applications where the ability to absorb and retain a free liquid is desired. Such applications include consumer products, medical products, as well as environmental and agricultural applications. Examples of such products are provided herein but are not intended to be limiting. The invention extends to any product which incorporates or is formed from the absorbent materials herein described.

[0112] Absorbent technology is employed in the hygiene industry for a range of products including, but not limited to, diapers for babies, children and adults (also known as “nappies”), feminine hygiene products such as sanitary pads (“sanitary napkins”) and tampons, incontinence pads, pet pads, etc.

[0113] In the medical sector, absorbent materials are employed in wound dressings, medical bandages and in disposable bed sheets, bed pads, and absorbent pads for chairs.

[0114] In the food industry, absorbent technology is employed in the form of absorbent packaging capable of absorbing moisture or fluids, such as meat or fish juices, released from any food product during transport or storage. Such packaging includes, but is not limited to, absorbent pads (also known as soaker pads), absorbent mats, absorbent liners and absorbent inter-leavers. Absorbent pads may, for example, be used in food display trays which carry fresh or frozen meats, fresh or frozen seafood (e.g. fish), or inside food punnets which carry fresh fruit, and are intended to improve the shelf-life and appearance of the food. Absorbent mats and liners may be used in crates in which fresh or frozen meat or fish is stored and / or transported. Absorbent inter-leavers may be used in the packaging of sliced meats or fish. In the environmental and agricultural sectors, absorbent materials may find use in improving water retention in soil.

[0115] Methods for the production of absorbent articles which are formed from or incorporate any of the absorbent cellulose I alginate-containing materials herein described also form part of the invention.

[0116] In a further aspect the invention thus provides a method of producing an absorbent article which is formed from or which incorporates an absorbent cellulose I alginate- containing material which comprises cellulose fibres and a residue of alginate from a brown seaweed, said method comprising at least the following steps:

[0117] (i) providing a brown seaweed, or part thereof;

[0118] (ii) dividing the brown seaweed, or part thereof, into a plurality of portions;

[0119] (iii) washing the plurality of portions with water whereby to remove water- soluble components and recovering the residual solids;

[0120] (iv) extracting alginate from the residual solids and recovering a residual wet residue comprising cellulose fibres and a residue of alginate;

[0121] (v) de-watering the residual wet residue whereby to provide a dry residue;

[0122] (vi) optionally reducing the particle size of the dry residue; and

[0123] (vii) forming an absorbent article from the resulting cellulose I alginate- containing material or incorporating the resulting cellulose I alginate- containing material into an absorbent article.

[0124] Methods for incorporation of absorbent materials into the types of products, for example consumer articles, herein described and which are intended to be used for absorption of fluids depend on the nature of the article or product and are generally well known in the art. The level of incorporation will vary depending on the absorbency required in any given application but can be varied according to need.

[0125] In some embodiments, the absorbent cellulose I alginate-containing material herein described may be formed or shaped into an absorbent sheet, layer, pad or film. Such products also form part of the invention. In other embodiments, the absorbent cellulose I alginate-containing material herein described will be incorporated (e.g. dispersed or embedded) into a carrier matrix, for example a fibrous carrier matrix, to form a composite material. Such composite materials also form part of the invention. In a further aspect, the invention thus provides a composite material comprising a carrier matrix which incorporates an absorbent cellulose I alginate-containing material as herein described.

[0126] The carrier matrix may be provided in the form of a sheet, layer, pad or film which may be used as such or which may be incorporated into a final product. The nature of the carrier matrix will depend on the intended use and can readily be selected based on materials generally known and used in the art. Typically, the carrier matrix will be a fibrous matrix which functions as a reservoir to hold liquid until the liquid is absorbed by the absorbent material dispersed therein. The fibrous matrix may, for example, be formed from a hydrophobic polymeric material (e.g. meltblown polyolefin fibres) and / or from cellulosic fibres (e.g. airlaid cellulosic fibres or Kraft cellulose pulp). Fibres commonly known as wood pulp fluff may, for example, form the fibrous matrix. A typical level of incorporation of the absorbent material into the fibrous carrier matrix may be at least 20 wt.%, at least 30 wt.% or at least 50 wt.%.

[0127] In the case of a diaper, for example, the absorbent materials herein described may be used in place of known superabsorbent polymers, such as sodium polyacrylate, which are conventionally used in an absorbent core layer of the diaper to absorb and trap urine. Such core layers typically comprise a carrier matrix, such as cotton or Kraft cellulose pulp (“fluff pulp”), which provides an open matrix or channels through which urine can flow to reach the absorbent material embedded therein. An appropriate level of incorporation of the absorbent material in the carrier matrix may be at least 20 wt.%, at least 30 wt.%, at least 50 wt.%, at least 60 wt.% or at least 70 wt.%.

[0128] Any of the articles or products listed herein which incorporate an absorbent material as herein described also form part of the invention.

[0129] In one embodiment, the invention provides a diaper having an absorbent core layer which comprises a carrier matrix having dispersed therein particles of a cellulose I alginate-containing material as herein described. In one embodiment, the invention provides an absorbent food packaging material such as a soaker pad for packaging fresh or frozen meat or fish and which is capable of absorption and retention of exudate from the meat or fish. This product may be provided in the form of a fluid-permeable envelope or sleeve which retains particles of an absorbent cellulose I alginate-containing material as herein described. Fluid-permeable materials for use in the production of soaker pads for foods are well known in the art and may be made from a range of materials including, but not limited to, poly-lactic acid (PLA).

[0130] Use of any of the cellulose I alginate-containing materials herein described as an absorbent also forms part of the invention. In a further aspect the invention thus provides the use of cellulose I alginate-containing material as an absorbent, wherein said material comprises cellulose fibres and a residue of alginate from a brown seaweed, and wherein said material is obtained by a process as herein described.

[0131] The invention will be described in more detail by way of the following non-limiting examples and the accompanying figures in which:

[0132] Figure 1 is a flowchart illustrating embodiments of the process according to the invention in which stipe is processed to produce an absorbent cellulose I alginate-containing material.

[0133] Figure 2 is a flowchart illustrating embodiments of the process according to the invention in which leaf is processed to produce an absorbent cellulose I alginate-containing material.

[0134] Figure 3 shows a comparison of the free swelling capacity of the cellulose I alginate-containing materials produced in Examples 1-9 vs. Kraft cellulose pulp PW411 in the presence of a 0.9% NaCI solution (0.9% NaCI dissolved in deionised water).

[0135] Figure 4 shows a comparison of the retention capacity of the cellulose I alginate-containing materials produced in Examples 1-9 vs. Kraft cellulose pulp PW411 in the presence of a 0.9% NaCI solution (0.9% NaCI dissolved in deionised water). Examples

[0136] Materials:

[0137] Kraft cellulose pulp PW411 (“fluff pulp”).

[0138] Laminaria hyperborea harvested near Haugesund, Norway.

[0139] Fucus serratus collected from North Landing, Flamborough, UK.

[0140] Laminaria digitata collected at low tide from North Landing, Flamborough, UK. The sodium-based alkali used in all examples is a saturated solution of sodium carbonate.

[0141] Measurement methods:

[0142] An analytical balance capable of weighing to 0.001 g was used and all weights were recorded to the nearest 0.01 g. The balance used was a Bonvoisin HZ5003B with a maximum capacity of 500 g.

[0143] Free Swelling

[0144] Free swelling of sample materials was determined according to the following method and calculation:

[0145] Method:

[0146] A 20 ml centrifuge tube was weighed to record its empty weight (W1). A sample of the material (0.2 to 0.5 g) was added to the tube and the weight of the tube + contents was recorded (W2). An aqueous fluid (0.9% NaCI dissolved in deionised water) was added to the sample in the tube. Once swelling started, additional fluid was added to ensure that an excess was always present. The sample was left to equilibrate for a period of 2-4 hours. Using a pipette, all excess fluid was removed from the tube. The tube + sample was reweighed and the weight recorded (W3).

[0147] Calculation:

[0148] The weight of the dry sample (W4) was calculated: W4 = (W2-W1).

[0149] The mass of fluid absorbed by the sample (W5) was calculated: W5 = (W3-W1).

[0150] The % swelling of the sample was calculated: ((W5-W4) / W5)*100.

[0151] The swelling of the sample in g / g (i.e. mass of fluid taken up by the sample based on the mass of the sample) was calculated: (W5 / W4). Retention Capacity

[0152] The ability of the sample to retain fluid (i.e. its retention capacity) was determined according to the following method and calculation:

[0153] Method:

[0154] A 20 ml centrifuge tube was weighed to record its empty weight (W1). A sample of the material (0.2 to 0.5 g) was added to the tube and the weight of the tube + contents was recorded (W2). An aqueous fluid (0.9% NaCI dissolved in deionised water) was added to the sample in the tube. Once swelling started, additional fluid was added to ensure that an excess was always present. The sample was left to equilibrate for a period of 2-4 hours. Using a pipette, all excess fluid was removed from the tube. Additional fluid (0.9% NaCI solution or deionised water) was added, and the sample was left to equilibrate for 15 minutes. The tube containing the sample was placed in a centrifuge (Goldenwall 80-2) and centrifuged for 5 minutes at 2500 rpm (g-force 700). Using a pipette, the excess fluid was removed from the tube. The steps of adding additional fluid, centrifugation and removal of excess fluid were repeated (to complete two cycles). The tube + sample was reweighed and the weight recorded (W3).

[0155] Calculation:

[0156] The weight of the dry sample (W4) was calculated: W4 = (W2-W1).

[0157] The mass of fluid absorbed by the sample (W5) was calculated: W5 = (W3-W1). The mass retention (%) of the sample was calculated: ((W5-W4) / W5)*100.

[0158] The swelling of the sample in g / g (i.e. mass of fluid taken up and retained by the sample based on the mass of the sample) was calculated: (W5 / W4).

[0159] The following is basically the industry standard method for the determination of either loss on drying (% moisture) or total solids (% dry matter)

[0160] Dry matter content

[0161] The amount of dry matter is determined by drying a weighed amount of material at 103°C for 4 hours in a conventional oven. This test can be carried out on material at any stage of the process. This includes raw materials and finished products. The test is carried out in duplicate. Materials:

[0162] Drying dish Balance (4 place) Oven (103 7.2°C)

[0163] Method:

[0164] 1) Label empty aluminium weighing dish with the sample I.D. and place onto the balance. Record the empty weight (Dish).

[0165] 2) Transfer approximately 5 g of material into the drying dish and record this weight (Dish + Sample). Calculate the weight transferred (Dish + Sample - Dish) and record as (Sample) on record sheet.

[0166] 3) Place dish in oven at 103+ / . 2°C and allow drying for 4 hours.

[0167] 4) After 4 hours remove the dish from the oven and allow cooling for 5 minutes.

[0168] 5) Re-weigh the dish and record the dried weight (DRY).

[0169] 6) Calculate residue weight (Dry - Dish) and record on sheet (RES).

[0170] Result is expressed as solids on drying (dry matter) %: Dry matter % = (Res I Sample) x 100

[0171] Loss of dry matter - alginate yield

[0172] Alginate yield (i.e. the amount of alginate removed) can be quantified either based on the amount of alginate recovered or based on the loss of dry matter from the brown seaweed. The initial step (or steps) of washing the portions of seaweed results in the removal of salts and other water-soluble substances from the seaweed matrix. At this stage, the alginate remains in its native insoluble form and is not removed. The starting point for determining the loss of dry matter, and thus quantifying the amount of alginate extracted, is the dry matter content of the washed seaweed material. As referred to herein, the “loss of dry matter” is thus the difference in the dry matter content of the washed seaweed material (i.e. the “residual solids” produced following removal of salts and other water-soluble components in accordance with step (iii) of the process as herein described) and the dry matter content of the final seaweed residue (i.e. the material produced following completion of step (v) of the process as herein described).

[0173] Loss of dry matter is determined as follows: Initial dry matter content: the dry matter content of the material is determined after washing, i.e. following removal of water-soluble components, according to the method specified under “dry matter content”.

[0174] Final dry matter content: the dry matter content of the final material is determined according to the method specified under “dry matter content”.

[0175] Loss of dry matter % = (difference between initial and final dry matter content I initial dry matter content) x 100

[0176] Where ranges for loss of dry matter are recorded in any of the examples, these are based on multiple repeats performed under the same conditions. As will be appreciated, variability can arise due to the natural variability in the composition of the biomass itself (it is a non-homogeneous material).

[0177] Particle size

[0178] Particle size was estimated by eye, but can be determined by methods such as “sieve analysis” in which a sample is shaken on a stack of sieves of graduated size (largest at the top and smallest on the bottom). These are weighed empty and then at the end of the test to allow the determination of the mass (and hence %) retained at each level. Industry standards which may be followed in respect of the measurement of particle size of the type of materials herein described are as follows: ISO 19.120 or ASTM 214.

[0179] Example 1

[0180] Preparation of absorbent cellulose / alginate-containing material from stipe of Laminaria hyperborea

[0181] Acid cation exchange: HCI

[0182] Alkaline extraction: T = 50-60°C; pH = 9.5-10; t = 4-6 hours Propan-2-ol drying

[0183] Stipe from L. hyperborea was milled using a Ninja food processor model BN650K (800w) to produce approx. 1 cm pieces. These were then soaked for 30 minutes in deionised water at ambient temperature, while stirring using a VEVOR JJ-1 overhead stirrer, followed by blending to reduce the particle size with a Tefal “Blendforce” BL42 blender (600W) using 2 x 5 second bursts per cycle. Water was then drained from the sample to recover the solid fraction. The conductivity of the drained water was measured using a Hanna instruments model “Primo 5” conductivity meter (scale 0 to 2000 pS). The steps of soaking, blending to reduce the particle size and water removal were repeated until the water conductivity was less than 200 pS. The particle size of the resulting solid fraction was in the range of about 2-3 mm.

[0184] Deionised water was added to the resulting product in a ratio of 2:1 (water : solid), followed by the addition of HCI to obtain a pH of between 1.7 to 1.9 as measured using a Hanna instruments pH checker (model number HI98103). After a period of 20 minutes at ambient temperature, the acid water was drained and the solid fraction was recovered. An additional quantity of deionised water was added to the resulting solid fraction in a ratio of 2:1 (water : solid), followed by mixing for 10 minutes at ambient temperature, draining of acid water and recovery of the solid fraction. This water washing step was repeated.

[0185] The solid fraction was transferred to an extraction tank, low calcium water was added, and the resulting mixture heated to a temperature of 50 to 60°C using a 9L water heater (model number MIS882). Stirring was maintained with a VEVOR JJ-1 overhead stirrer to ensure free movement of the material. Sodium carbonate I sodium hydroxide was added to adjust the pH to between 9.5 to 10. The mixture was held for 4-6 hours to extract alginate into solution. The mixture was then filtered, and the solid and liquid fractions recovered. Alginate was recovered from the liquid fraction. The solid fraction was neutralised by the addition of acid to achieve a pH of between 6.7 and 7.1 , followed by centrifugation for 5 minutes using a “SIA Centri 772 SEK” spin dryer (2800 rpm generating a g-force of 960) to remove as much free water as possible. This was followed by drying to recover the final product. Drying was achieved by mixing the “wet” sample with propan-2-ol at a ratio of 1:1 in a sealed container and allowing to equilibrate for 5 minutes. The solvent was then recovered by filtration and the solid portion centrifuged for 5 minutes to remove any remaining excess liquid (all recovered solvent was recycled by evaporation for re-use). The centrifuged sample was then dried under vacuum (100 mbar) at a temperature of 70°C for approx. 2 hours. The particle size of the dried material was reduced further using a “Cosicosy” coffee grinder (350W) for 30 seconds to obtain a final particle size of approx. 500 pm. The final product was a dark brown granular material with a residual moisture content of less than 10%. When mixed with water and treated with 20% calcium chloride solution, no gelling was observed.

[0186] Loss of dry matter: 30 to 34%.

[0187] Free swelling and retention capacity were determined and compared to a sample of Kraft cellulose pulp PW411. The following results were obtained:

[0188] Example 2

[0189] Preparation of absorbent cellulose / alginate-containing material from stipe of Laminaria hyperborea

[0190] Acid cation exchange: HCI

[0191] Alkaline extraction: T = 50-60°C; pH = 9.5-10; t = 4-6 hours Direct vacuum drying

[0192] Stipe from L. hyperborea was milled using a Ninja food processor model BN650K (800W) to produce approx. 1 cm pieces. These were then soaked for 30 minutes in deionised water at ambient temperature, while stirring using a VEVOR JJ-1 overhead stirrer, followed by blending to reduce the particle size with a Tefal “Blendforce” BL42 blender (600W) using 2 x 5 second bursts per cycle. Water was then drained from the sample to recover the solid fraction. The conductivity of the drained water was measured using a Hanna instruments model “Primo 5” conductivity meter (scale 0 to 2000 pS). The steps of soaking, blending to reduce the particle size and water removal were repeated until the water conductivity was less than 200 pS. The particle size of the resulting solid fraction was in the range of about 2-3 mm. Deionised water was added to the resulting product in a ratio of 2:1 (water : solid), followed by the addition of HCI to obtain a pH of between 1.7 to 1.9, measured using a Hanna instruments pH checker (model number H 198103). After a period of 20 minutes at ambient temperature, the acid water was drained, and the solid fraction was recovered. An additional quantity of deionised water was added to the resulting solid fraction in a ratio of 2:1 (water : solid), followed by mixing for 10 minutes at ambient temperature, draining of acid water and recovering of the solid fraction. This water washing step was repeated.

[0193] The solid fraction was transferred to an extraction tank, low calcium water was added, and the resulting mixture heated to a temperature of 50 to 60°C using a 9L water heater (model number MIS882). Stirring was maintained with a VEVOR JJ-1 overhead stirrer to ensure free movement of the material. Sodium carbonate I sodium hydroxide was added to adjust the pH to between 9.5 to 10. The mixture was held for 4 to 6 hours to extract alginate into solution. The mixture was then filtered, and the solid and liquid fractions recovered. Alginate was recovered from the liquid fraction. The solid fraction was neutralised by the addition of acid to achieve a pH of between 6.7 and 7.1 , followed by centrifugation for 5 minutes using a “SIA Centri 772 SEK” spin dryer (2800 rpm generating a g-force of 960) to remove as much free water as possible. This was followed by drying to recover the final product. Drying was achieved under vacuum (100 mbar) at a temperature of 70°C for approx. 2 hours. The particle size of the dried material was reduced further using a “Cosicosy” coffee grinder (350W) for 30 seconds to obtain a final particle size of approx. 500 pm.

[0194] The final product was a dark brown granular material with a residual moisture content of less than 10%. When mixed with water and treated with 20% calcium chloride solution, no gelling was observed. When mixed with water and treated with 20% calcium chloride solution, no gelling was observed.

[0195] Loss of dry matter: 30 to 34%.

[0196] Free swelling and retention capacity were determined and compared to a sample of Kraft cellulose pulp PW411. The following results were obtained: Example 3

[0197] Preparation of absorbent cellulose / alginate-containing material from leaf of Laminaria hyperborea

[0198] Acid cation exchange: HCI

[0199] Alkaline extraction: T = 50-60°C; pH = 9.5-10; t = 4-6 hours Propan-2-ol drying

[0200] Method - Stage 1:

[0201] Leaf from L. hyperborea was milled using a Ninja food processor model BN650K (800W) to produce approx. 1 cm pieces. The leaf pieces were then soaked for 30 minutes in deionised water at 60°C using a 9L water heater (model number MIS882). Stirring was maintained with a VEVOR JJ-1 overhead stirrer to ensure free movement of the material. Excess water was drained and the solid fraction recovered. The recovered solid fraction was soaked for 15 minutes in deionised water at ambient temperature, excess water was drained, and the solid fraction recovered. These steps were repeated to provide two complete treatment cycles at 60°C. Following the second treatment cycle, the conductivity of the drained water was measured using a Hanna instruments model “Primo 5” conductivity meter (scale 0 to 2000 pS). The step of washing at ambient temperature and water removal were repeated until the water conductivity was less than 200 pS. The particle size of the resulting solid fraction was reduced to between about 2-3 mm by blending with a Tefal “Blendforce” BL42 blender (600w), using 2 x 5 second bursts per cycle.

[0202] Method - Stage 2:

[0203] Deionised water was added to the resulting product in a ratio of 2:1 (water : solid), followed by the addition of HCI to obtain a pH of between 1.7 to 1.9, measured using a Hanna instruments pH checker (model number HI98103). After a period of 20 minutes at ambient temperature, the acid water was drained, and the solid fraction was recovered. An additional quantity of deionised water was added to the resulting solid fraction in a ratio of 2:1 (water : solid), followed by mixing for 10 minutes at ambient temperature, draining of acid water and recovering of the solid fraction. This water washing step was repeated. The solid fraction was transferred to an extraction tank, low calcium water was added, and the resulting mixture heated to a temperature of 50 to 60°C using a 9L water heater (model number MIS882). Stirring was maintained with a VEVOR JJ-1 overhead stirrer to ensure free movement of the material. Sodium carbonate I sodium hydroxide was added to adjust the pH to between 9.5 to 10. The mixture was held for 4-6 hours to extract alginate into solution. The mixture was then filtered, and the solid and liquid fractions recovered. Alginate was recovered from the liquid fraction. The solid fraction was neutralised by the addition of acid to achieve a pH of between 6.7 and 7.1 , followed by centrifugation for 5 minutes using a “SIA Centri 772 SEK” spin dryer (2800 rpm generating a g-force of 960) to remove as much free water as possible. This was followed by drying to recover the final product. Drying was achieved by mixing the “wet” sample with propan-2-ol at a ratio of 1:1 in a sealed container and allowing to equilibrate for 5 minutes. The solvent was then recovered by filtration and the solid portion centrifuged again for 5 minutes to remove any remaining excess liquid (all recovered solvent was recycled by evaporation for re-use). The centrifuged sample was then dried under vacuum (100 mbar) at a temperature of 70°C for approx. 2 hours. The particle size of the dried material was reduced further using a “Cosicosy” coffee grinder (350W) for 30 seconds to obtain a final particle size of approximately 500 pm.

[0204] The final product was a dark brown granular material with a residual moisture content of less than 10%. When mixed with water and treated with 20% calcium chloride solution, no gelling was observed.

[0205] Loss of dry matter: 82%.

[0206] Free swelling and retention capacity were determined and compared to a sample of Kraft cellulose pulp PW411. The following results were obtained: Example 4

[0207] Preparation of absorbent cellulose / alginate-containing material from stipe of Laminaria hyperborea

[0208] Acid cation exchange: HCI

[0209] Alkaline extraction: T = 20-25°C; pH = 6.8-7.1; t = 2-3 hours Propan-2-ol drying

[0210] Method - Stage 1:

[0211] Frozen stipe from L. hyperborea was milled using a Ninja food processor model BN650K (800w) to produce approx. 1 cm pieces. These were then soaked for 30 minutes in deionised water at ambient temperature, while stirring using a VEVOR JJ-1 overhead stirrer, followed by blending to reduce the particle size with a Tefal “Blendforce” BL42 blender (600W) using 2 x 5 second bursts per cycle. Water was then drained from the sample to recover the solid fraction. The conductivity of the drained water was measured using a Hanna instruments model “Primo 5” conductivity meter (scale 0 to 2000 pS). The steps of soaking, blending to reduce the particle size and water removal were repeated until the water conductivity was less than 200 pS. The particle size of the resulting solid fraction was in the range of about 2-3 mm.

[0212] Method - Stage 2:

[0213] Deionised water was added to the resulting product in a ratio of 2:1 (water : solid), followed by the addition of HCI to obtain a pH of between 1.7 to 1.9 as measured using a Hanna instruments pH checker, model number HI98103. After a period of 20 minutes at ambient temperature, the acid water was drained, and the solid fraction was recovered. An additional quantity of deionised water was added to the resulting solid fraction in a ratio of 2:1 (water : solid), followed by mixing for 10 minutes at ambient temperature, draining of the acid water and recovering of the solid fraction. This water washing step was repeated.

[0214] The solid fraction was transferred to an extraction tank, low calcium water was added, and the resulting mixture heated to a temperature of 20 to 25°C using a 9L water heater model number MIS882. Stirring was maintained with a VEVOR JJ-1 overhead stirrer to ensure free movement of the material. Sodium carbonate I sodium hydroxide was added to adjust the pH to between 6.8 to 7.1. The mixture was held for 2-3 hours to extract alginate into solution. The mixture was then filtered, and the solid and liquid fractions recovered. Alginate was recovered from the liquid fraction.

[0215] The resulting solid portion was then dried by mixing the “wet” sample with propan-2- ol at a ratio of 1 :1 in a sealed container and allowing to equilibrate for 5 minutes. The solvent was then recovered by filtration and the solid portion centrifuged again for 5 minutes to remove any remaining excess liquid (all recovered solvent was recycled by evaporation for re-use). The centrifuged sample was then dried under vacuum (100 mbar) at a temperature of 70°C for approx. 2 hours. The particle size of the dried material was reduced further using a “Cosicosy” coffee grinder (350W) for 30 seconds to obtain a final particle size of approx. 500 pm.

[0216] The product was a light brown granular material with a residual moisture content of less than 10%. When mixed with water and treated with 20% calcium chloride solution, a firm cohesive gel was formed.

[0217] Loss of dry matter: 20 to 22%.

[0218] Free swelling and retention capacity were determined and compared to a sample of Kraft cellulose pulp PW411. The following results were obtained:

[0219] Example 5

[0220] Preparation of absorbent cellulose / alginate-containing material from stipe of

[0221] Laminaria hyperborea

[0222] Citric acid pre-treatment: 1% citric acid solution; T= 20-25°C; t = 60 minutes

[0223] Acid cation exchange: HCI

[0224] Alkaline extraction: T = 20-25°C; pH = 6.8-7.1; t = 2-3 hours

[0225] Propan-2-ol drying The method of Example 4 was repeated but with an additional citric acid pretreatment step prior to acid cation exchange. The solid fraction from Stage 1 was treated with 1% citric acid solution at ambient temperature for 60 minutes. The resulting mixture was then drained to remove excess solution and the solid fraction was recovered. This solid fraction was then subjected to the treatment set out in Example 4 to obtain the final product.

[0226] The final product was a pale green granular material with a residual moisture content of less than 10%. When mixed with water and treated with 20% calcium chloride solution, a firm highly cohesive gel was formed.

[0227] Loss of dry matter: 15 to 23%.

[0228] Free swelling and retention capacity were determined and compared to a sample of Kraft cellulose pulp PW411. The following results were obtained:

[0229] Example 6

[0230] Preparation of absorbent cellulose / alginate-containing material from leaf of Laminaria hyperborea

[0231] Citric acid pre-treatment: 1% anhydrous citric acid; T= 20-25°C; t = 60 minutes Acid cation exchange: HCI

[0232] Alkaline extraction: T = 20-25°C; pH = 6.8-7.1; t = 2-3 hours

[0233] Propan-2-ol drying

[0234] Method - Stage 1:

[0235] This was performed as set out in Example 4.

[0236] Method - Stage 2:

[0237] The solid fraction was added to a solution containing 1% anhydrous citric acid (APC pure, BP / LISP grade 99.5 to 100.5%) in a ratio of 2:1, and stirred at ambient temperature (18 to 25°C) for 60 minutes using a VEVOR JJ-1 overhead stirrer. After 60 minutes the acid water was drained and the solid fraction was recovered. An additional quantity of deionised water was added to the resulting solid fraction in a ratio of 2:1 (water : solid), followed by mixing for 10 minutes at ambient temperature, draining of acid water and recovering of the solid fraction. Deionised water was added to the resulting product in a ratio of 2:1 (water : solid), followed by the addition of HCI to obtain a pH of between 1.7 to 1.9 as measured using a Hanna instruments pH checker, model number HI98103. After a period of 20 minutes at ambient temperature, the acid water was drained, and the solid fraction was recovered. An additional quantity of deionised water was added to the resulting solid fraction in a ratio of 2:1 (water : solid), followed by mixing for 10 minutes at ambient temperature, draining of acid water and recovering of the solid fraction. This water washing step was repeated.

[0238] The solid fraction was transferred to an extraction tank, low calcium water was added, and the resulting mixture heated to a temperature of 20 to 25°C using a 9L water heater model number MIS882. Stirring was maintained with a VEVOR JJ-1 overhead stirrer to ensure free movement of the material. Sodium carbonate I sodium hydroxide was added to adjust the pH to between 6.8 to 7.1. The mixture was held for 2-3 hours to extract alginate into solution. The mixture was then filtered, and the solid and liquid fractions recovered. Alginate was recovered from the liquid fraction.

[0239] The resulting solid portion was then dried by mixing the “wet” sample with propan-2- ol at a ratio of 1 :1 in a sealed container and allowing to equilibrate for 5 minutes. The solvent was then recovered by filtration and the solid portion centrifuged again for 5 minutes to remove any remaining excess liquid (all recovered solvent was recycled by evaporation for re-use). The centrifuged sample was then dried under vacuum (100 mbar) at a temperature of 70°C for approx. 2 hours. The particle size of the dried material was then reduced further using a “Cosicosy” coffee grinder (350W) for 30 seconds to obtain a final particle size of approx. 500 pm.

[0240] Loss of dry matter: 37 to 51%. The product was a light brown granular material with a residual moisture content of less than 10%. When mixed with water and treated with 20% calcium chloride solution, a firm cohesive gel was formed.

[0241] Free swelling and retention capacity were determined and compared to a sample of Kraft cellulose pulp PW411. The following results were obtained:

[0242] Example 7

[0243] Preparation of absorbent cellulose / alginate-containing material from whole Fucus serratus

[0244] Citric acid pre-treatment: 1% anhydrous citric acid; T= 20-25°C; t = 60 minutes Acid cation exchange: HCI

[0245] Alkaline extraction: T = 20-25°C; pH = 6.8-7.1; t = 2-3 hours Propan-2-ol drying

[0246] Method - Stage 1:

[0247] Fresh Fucus serratus was obtained. This stage was performed as set out in Example 4.

[0248] Method - Stage 2:

[0249] The solid fraction was added to a solution containing 1% anhydrous citric acid (APC pure, BP / LISP grade 99.5 to 100.5%) in a ratio of 2:1, and stirred at ambient temperature (18 to 25°C) for 60 minutes using a VEVOR JJ-1 overhead stirrer.

[0250] After 60 minutes the acid water was drained, and the solid fraction was recovered. An additional quantity of deionised water was added to the resulting solid fraction in a ratio of 2:1 (water : solid), followed by mixing for 10 minutes at ambient temperature, draining of acid water and recovering of the solid fraction. Deionised water was added to the resulting product in a ratio of 2:1 (water : solid), followed by the addition of HCI to obtain a pH of between 1.7 to 1.9 as measured using a Hanna instruments pH checker, model number HI98103. After a period of 20 minutes at ambient temperature, acid water was drained, and the solid fraction was recovered. An additional quantity of deionised water was added to the resulting solid fraction in a ratio of 2:1 (water : solid), followed by mixing for 10 minutes at ambient temperature, draining of acid water and recovering of the solid fraction. This water washing step was repeated.

[0251] The solid fraction was transferred to an extraction tank, low calcium water was added, and the resulting mixture heated to a temperature of 20 to 25°C using a 9L water heater model number MIS882. Stirring was maintained with a VEVOR JJ-1 overhead stirrer to ensure free movement of the material. Sodium carbonate I sodium hydroxide was added to adjust the pH to between 6.8 to 7.1. The mixture was held for 2-3 hours to extract alginate into solution. The mixture was then filtered, and the solid and liquid fractions recovered. Alginate was recovered from the liquid fraction.

[0252] The resulting solid portion was then dried by mixing the “wet” sample with propan-2- ol at a ratio of 1 :1 in a sealed container and allowing to equilibrate for 5 minutes. The solvent was then recovered by filtration and the solid portion centrifuged again for 5 minutes to remove any remaining excess liquid (all recovered solvent was recycled by evaporation for re-use). The centrifuged sample was then dried under vacuum (100 mbar) at a temperature of 70°C for approx. 2 hours. The particle size of the dried material was reduced further using a “Cosicosy” coffee grinder (350W) for 30 seconds to obtain a final particle size of approx. 500 pm.

[0253] The product was a light brown granular material with a residual moisture content of less than 10%. When mixed with water and treated with 20% calcium chloride solution, a non-cohesive gel was formed.

[0254] Loss of dry matter: 20 to 25%.

[0255] Free swelling and retention capacity were determined and compared to a sample of Kraft cellulose pulp PW411. The following results were obtained: Example 8

[0256] Preparation of absorbent cellulose / alginate-containing material from stipe of Laminaria digitata

[0257] Citric acid pre-treatment: 1% citric acid; T= 20-25°C; t = 60 minutes Acid cation exchange: HCI

[0258] Alkaline extraction: T = 20-25°C; pH = 6.8-7.1; t = 2-3 hours Propan-2-ol drying

[0259] The method of Example 3 was repeated but with an additional citric acid pretreatment step prior to acid cation exchange. The solid fraction from Stage 1 was treated with 1% citric acid solution at ambient temperature for 60 minutes. The resulting mixture was then drained to remove excess solution and the solid fraction was recovered. This solid fraction was then subjected to the treatment set out in Example 3.

[0260] The product was a pale green granular material with a residual moisture content of less than 10%. When mixed with water and treated with 20% calcium chloride solution, a firm cohesive gel was formed.

[0261] Loss of dry matter: 25 to 30%.

[0262] Free swelling and retention capacity were determined and compared to a sample of Kraft cellulose pulp PW411. The following results were obtained:

[0263] Example 9

[0264] Preparation of absorbent cellulose / alginate-containing material from leaf of

[0265] Laminaria digitata

[0266] Citric acid pre-treatment: 1% anhydrous citric acid; T= 20-25°C; t = 60 minutes

[0267] Acid cation exchange: HCI

[0268] Alkaline extraction: T = 20-25°C; pH = 6.8-7.1; t = 2-3 hours Propan-2-ol drying

[0269] Method - Stage 1:

[0270] Fresh Laminaria digitata was milled using a Ninja food processor model BN650K (800W) to produce approx. 1 cm pieces. The leaf pieces were then soaked for 30 minutes in deionised water at 60°C using a 9L water heater model number MIS882. Stirring was maintained with a VEVOR JJ-1 overhead stirrer to ensure free movement of the material. Excess water was drained and the solid fraction recovered. The recovered solid fraction was soaked for 15 minutes in deionised water at ambient temperature, excess water was drained, and the solid fraction recovered. These steps were repeated to provide two complete treatment cycles at 60°C.

[0271] Following the second treatment cycle, the conductivity of the drained water was measured using a Hanna instruments model “Primo 5” conductivity meter (scale 0 to 2000 pS). The step of washing at ambient temperature and water removal were repeated until the water conductivity was less than 200 pS.

[0272] The resulting solid fraction was milled to reduce the particle size of the material to between about 2-3 mm by blending to reduce the particle size with a Tefal “Blendforce” BL42 blender (600W), using 2 x 5 second bursts per cycle.

[0273] Method - Stage 2:

[0274] The solid fraction was added to a solution containing 1% anhydrous citric acid (APC pure, BP / LISP grade 99.5 to 100.5%) in a ratio of 2:1, and stirred at ambient temperature (18 to 25°C) for 60 minutes using a VEVOR JJ-1 overhead stirrer. After 60 minutes the acid water was drained, and the solid fraction was recovered. An additional quantity of deionised water was added to the resulting solid fraction in a ratio of 2:1 (water : solid), followed by mixing for 10 minutes at ambient temperature, draining of acid water and recovering of the solid fraction. Deionised water was added to the resulting product in a ratio of 2:1 (water : solid), followed by the addition of HCI to obtain a pH of between 1.7 to 1.9 as measured using a Hanna instruments pH checker, model number HI98103. After a period of 20 minutes at ambient temperature, the acid water was drained, and the solid fraction was recovered. An additional quantity of deionised water was added to the resulting solid fraction in a ratio of 2:1 (water : solid), followed by mixing for 10 minutes at ambient temperature, draining of acid water and recovering of the solid fraction. This water washing step was repeated.

[0275] The solid fraction was transferred to an extraction tank, low calcium water was added, and the resulting mixture heated to a temperature of 20 to 25°C using a 9L water heater model number MIS882. Stirring was maintained with a VEVOR JJ-1 overhead stirrer to ensure free movement of the material. Sodium carbonate I sodium hydroxide was added to adjust the pH to between 6.8 to 7.1. The mixture was held for 2-3 hours to extract alginate into solution. The mixture was then filtered, and the solid and liquid fractions recovered. Alginate was recovered from the liquid fraction.

[0276] The resulting solid portion was then dried by mixing the “wet” sample with propan-2- ol at a ratio of 1 : 1 in a sealed container and allowing to equilibrate for 5 minutes. The solvent was then recovered by filtration and the solid portion centrifuged again for 5 minutes to remove any remaining excess liquid (all recovered solvent was recycled by evaporation for re-use). The centrifuged sample was then dried under vacuum (100 mbar) at a temperature of 70°C for approx. 2 hours. The particle size of the dried material was reduced further using a “Cosicosy” coffee grinder (350W) for 30 seconds to obtain a final particle size of approx. 500 pm.

[0277] The product was a light brown granular material with a residual moisture content of less than 10%. When mixed with water and treated with 20% calcium chloride solution, a firm cohesive gel was formed.

[0278] Loss of dry matter: 38 to 42%.

[0279] Free swelling and retention capacity were determined and compared to a sample of Kraft cellulose pulp PW411. The following results were obtained: Example 10

[0280] Determination of the composition of the residue produced following alkaline extraction of alginate from intact stipe of Laminaria hyperborea

[0281] Whole (i.e. unpeeled) stipe was processed to recover the available alginate (yield = 38.7% of the starting dry mass). The solid residue remaining after alginate recovery was investigated to determine its composition.

[0282] Recovery of alginate

[0283] Metal cation exchange:

[0284] The stipe sample was transferred to a blender and hydrochloric acid added to the reaction mixture to reduce the overall pH to between 1.7 and 1.9. The acidified sample was then blended using 2 x 5 second blending pulses, and the sample left to stand. The sample was then drained through a filter, and then rinsed with demineralised water to remove excess hydrochloric acid.

[0285] Extraction of alginate:

[0286] The mineral acid treated sample was then drained through a filter and the solids transferred to a blender along with deionised water. A saturated sodium carbonate solution was added to the blender, and the resultant mixture blended using 2 x 5 second blending pulses. The pH of the blended mixture was approximately 9. The blended mixture was then transferred to a reaction vessel and further saturated sodium carbonate solution was added with stirring over a period of 30 to 45 mins to maintain a solution pH of approximately 7.5 to 8. During this process, the alginic acid is neutralised by the sodium carbonate. This produces soluble sodium alginate, which can be extracted into solution for recovery.

[0287] After stirring for 30 to 45 mins, the solid particles were removed from the solution by filtration to obtain a primary extract. Once all of the liquid had been collected, the solids on the filter were transferred to a beaker and mixed with demineralised water. This mixture was left to stand for 10 mins, during which time most of the remaining alginate was extracted, and then filtered to obtain a secondary extract. The primary and secondary extracts were then combined to form an alginate solution. Alginate recovery (“alginic acid route”):

[0288] Hydrochloric acid was added to the alginate solution with mixing to reduce the pH to between 1.7 and 1.9. This converts the sodium alginate to alginic acid, which is insoluble and precipitates as a thick transparent gel. The solution was then filtered, and the gel was retained on the filter. The gel was then converted to sodium alginate. The gel was transferred to a reaction vessel, and a saturated sodium carbonate solution was added to the gel with stirring until the pH was between 7.0 and 7.3.

[0289] An equal volume (1:1 ratio) of propan-2-ol was added to the solution of sodium alginate. The solution was then mixed, which caused sodium alginate to be displaced from solution as a thick gel. The resulting mixture was then transferred to a blender and pulsed for 5 seconds to disperse the gel and complete the precipitation process. The mixture was then filtered to recover the product, and the propan-2-ol recovered using a rotary evaporator. To remove the remaining water from the gel-like product obtained, the sample was returned to the blender and a further portion of propan-2-ol was added. The resulting mixture was blended for 5 seconds, and then filtered. The sodium alginate was obtained as a pellet on the filter, and the propan-2-ol was recovered. The pellet of alginate was then dried at 30°C.

[0290] Recovery of solid residue

[0291] The solid residue from the alginate extraction process was collected and further extracted in water at 60°C, whereupon an additional amount of alginate was recovered (yield = 8% of the starting dry mass) bringing the total alginate yield to 46.7%. The remaining solid residue was a wet mass having a slightly sticky surface which implies the presence of non-extracted (i.e. residual) alginate. The wet residue was treated sequentially with propan-2-ol to remove the remaining water and facilitate drying at low temperature (30°C). This resulted in a light-coloured powder. The dried residue was weighed to determine the yield, which was calculated as 32.1% of the starting dry mass.

[0292] To test for the presence of calcium reactive alginate in the dried residue, it was hydrated to form a paste before being treated with a calcium chloride solution. The hydrated residue reacted to form a solid gel which indicates the presence of calcium reactive (G-block) bearing alginate. The wet residue was also extruded into a calcium chloride solution from a pipette.

[0293] The native cellulose content of the residue was determined by hydrating the dried material then hydrolysing with two cycles of 5% sodium hydroxide at 80°C for 4 hours. The remaining residue was washed with deionised water until the pH was less than 8, whereupon it was collected and dried. This was weighed and the yield determined as 18.3% of the starting dry mass. The composition of the solid residue could therefore be calculated. The process residue yield was 32.1%. As the cellulose yield was 18.3%, the alginate remaining in the process residue can be assumed to be 13.8%. The composition of the residue was therefore determined as 43% alginate and 57% cellulose. While the invention has been described in detail with reference to specific embodiments thereof, it will be understood that various changes and modifications can be made without departing from the spirit and scope thereof.

Claims

Claims:

1. An absorbent article comprising an absorbent cellulose I alginate-containing material, wherein said material comprises cellulose fibres and a residue of alginate from a brown seaweed, and wherein said material is obtained by a process comprising at least the following steps:(i) providing a brown seaweed, or part thereof;(ii) dividing the brown seaweed, or part thereof, into a plurality of portions;(iii) washing the plurality of portions with water whereby to remove water- soluble components and recovering the residual solids;(iv) extracting alginate from the residual solids and recovering a residual wet residue comprising cellulose fibres and a residue of alginate; and(v) de-watering the residual wet residue whereby to provide said absorbent cellulose I alginate-containing material as a dry residue.

2. An absorbent article as claimed in claim 1 , wherein said material is obtained by a process in which the dry residue has a water content of less than about 20 wt.%, preferably a water content of about 5 to about 15 wt.%, based on the total weight of the dry residue.

3. An absorbent article as claimed in claim 1 or claim 2, wherein said material is obtained by a process which further comprises the step of reducing the particle size of the dry residue, for example by subjecting said dry residue to milling and / or grinding.

4. An absorbent article as claimed in any one of the preceding claims, wherein said material is obtained by a process in which the loss of dry matter from the residual wet residue produced in step (iii) is at least about 15%, preferably at least about 20%.

5. An absorbent article as claimed in any one of the preceding claims, wherein said material is obtained by a process in which the loss of dry matter from the residual wet residue produced in step (iii) is at least about 30%.

6. An absorbent article as claimed in any one of the preceding claims, wherein said material is in particulate form.

7. An absorbent article as claimed in claim 6, wherein said material has an average particle size in the range from about 250 to about 600 pm, preferably about 250 to about 500 pm.

8. An absorbent article as claimed in any one of the preceding claims, wherein said material has a free swelling capacity of from 5 to 35 g / g as measured according to the examples when using an aqueous fluid which is 0.9% NaCI dissolved in deionised water.

9. An absorbent article as claimed in any one of the preceding claims, wherein said material has a retention capacity of from 5 to 35 g / g as measured according to the examples when using an aqueous fluid which is 0.9% NaCI dissolved in deionised water.

10. An absorbent article as claimed in any one of the preceding claims, wherein said material is obtained by a process in which step (iii) comprises washing the plurality of portions with potable water, seawater, demineralised water or deionised water.

11. An absorbent article as claimed in any one of the preceding claims, wherein said material is obtained by a process in which step (iv) comprises extracting alginate from the residual solids, adjusting the pH of the residual solids to within the range from about 6 to about 7, preferably from about 6.5 to 6.7, and recovering a residual wet residue comprising cellulose fibres and a residue of alginate.

12. An absorbent article as claimed in any one of the preceding claims, wherein said material is obtained by a process in which step (iv) comprises extracting substantially all extractable alginate from the residual solids.

13. An absorbent article as claimed in any one of the preceding claims, wherein said material is obtained by a process in which step (iv) comprises at least the following steps:contacting the residual solids with an aqueous solution of a mineral acid whereby to effect exchange of native calcium ions with hydrogen ions to produce alginic acid; recovering the resulting solid fraction; contacting the resulting solid fraction with an alkali (e.g. an alkaline solution) whereby to convert the alginic acid to a water-soluble form of alginate; and separating the water-soluble form of alginate from the solid fraction thereby recovering said residual wet residue comprising cellulose fibres and a residue of alginate.

14. An absorbent article as claimed in claim 13, wherein said material is obtained by a process in which the step of contacting the residual solids with an aqueous solution of a mineral acid is effective to reduce the pH to about 1.5 to about 2, e.g. to about 1.7 to about 1.

915. An absorbent article as claimed in claim 13 or claim 14, wherein the mineral acid is hydrochloric acid or sulphuric acid.

16. An absorbent article as claimed in any one of claims 13 to 15, wherein the step of contacting the resulting solid fraction with an alkali (e.g. an alkaline solution) is effective to increase the pH to about 6 to 10.

17. An absorbent article as claimed in claim 16, wherein said material is obtained by a process in which the alkali is selected from sodium hydroxide, potassium hydroxide, ammonium hydroxide, potassium carbonate and sodium carbonate and mixtures thereof, preferably wherein the alkali is sodium carbonate.

18. An absorbent article as claimed in claim 17, wherein said material is obtained by a process in which the alkali is solid sodium carbonate or a solution of sodium carbonate, for example a saturated sodium carbonate solution.

19. An absorbent article as claimed in any one of the preceding claims, wherein said material is obtained by a process in which step (v) is carried out by solvent dehydration, direct drying or vacuum assisted drying.

20. An absorbent article as claimed in claim 19, wherein said material is obtained by a process in which step (v) is carried out by solvent dehydration, preferably using a solvent selected from propanol, acetone, ethanol and ether.

21. An absorbent article as claimed in claim 20, wherein said material is obtained by a process in which step (v) is carried out by propanol dehydration.

22. An absorbent article as claimed in any one of the preceding claims, wherein said material is obtained by a process in which the brown seaweed is selected from the group consisting of Laminaria spp., Fucales spp., Ascophyllum spp., Durvillaea spp., Ecklonia spp., Lessonia spp., Macrocystis spp., Sargassum spp., and Saccharina spp.

23. An absorbent article as claimed in claim 22, wherein said material is obtained by a process in which the brown seaweed is Laminaria hyperborea, Laminaria digitata orFucus serratus, preferably Laminaria hyperborea.

24. An absorbent article as claimed in any one of the preceding claims, wherein said material is obtained by a process in which the brown seaweed part is stipe or leaf.

25. An absorbent article as claimed in claim 24, wherein said material is obtained by a process in which the stipe is unpeeled.

26. An absorbent article as claimed in any one of the preceding claims, wherein the cellulose I alginate-containing material is formed or shaped into a sheet, layer, pad or film which forms part or all of said article.

27. An absorbent article as claimed in any one of claims 1 to 25, wherein the cellulose I alginate-containing material is incorporated into a fibrous carrier matrix which forms part or all of said article.

28. An absorbent article as claimed in claim 27, wherein the fibrous carrier matrix is provided in the form of a sheet, layer, pad or film.

29. An absorbent article as claimed in any one of the preceding claims which is a disposable absorbent article.

30. An absorbent article as claimed in any one of the preceding claims which is a wound dressing, a diaper, a feminine hygiene product, an incontinence pad, or a packaging material for food.

31. An absorbent article as claimed in claim 30, wherein said article is a diaper in which the absorbent cellulose I alginate-containing material forms the fibrous matrix of an absorbent layer within the diaper.

32. An absorbent article as claimed in claim 31 , wherein the absorbent layer is additionally impregnated with a superabsorbent polymer, preferably sodium polyacrylate.

33. An absorbent article as claimed in claim 30 which is a packaging material for meat, fish or fruit, for example a packaging material for fresh or frozen meat or fish, or fresh fruit.

34. A method of producing an absorbent article which is formed from or which incorporates an absorbent cellulose I alginate-containing material, wherein said material comprises cellulose fibres and a residue of alginate from a brown seaweed, said method comprising at least the following steps:(i) providing a brown seaweed, or part thereof;(ii) dividing the brown seaweed, or part thereof, into a plurality of portions;(iii) washing the plurality of portions with water whereby to remove water- soluble components and recovering the residual solids;(iv) extracting alginate from the residual solids and recovering a residual wet residue comprising cellulose fibres and a residue of alginate;(v) de-watering the residual wet residue whereby to provide a dry residue;(vi) optionally reducing the particle size of the dry residue; and(vii) forming an absorbent article from the resulting absorbent cellulose I alginate-containing material or incorporating the resulting absorbent cellulose / alginate-containing material into an absorbent article.

35. A method as claimed in claim 34, wherein the absorbent cellulose I alginate- containing material is produced by a process as defined in any one of claims 1 to 25.

36. A method as claimed in claim 34 or claim 35, wherein the absorbent article is as defined in any one of claims 26 to 33.

37. Use of a cellulose I alginate-containing material as an absorbent, wherein said material comprises cellulose fibres and a residue of alginate from a brown seaweed, and wherein said material is obtained by a process as defined in any one of claims 1 to 25.

38. Use as claimed in claim 37, wherein said cellulose I alginate-containing material is formed, moulded or shaped into, or otherwise incorporated into an absorbent article as defined in any one of claims 26 to 33.

39. An absorbent cellulose I alginate-containing material, wherein said material comprises cellulose fibres and a residue of alginate from a brown seaweed, and wherein said material is obtained by a process as defined in any one of claims 1 to 25.

40. An absorbent cellulose I alginate-containing material as claimed in claim 39 which is in particulate form.

41. An absorbent cellulose I alginate-containing material as claimed in claim 40 having an average particle size in the range from about 250 to about 600 pm, preferably about 250 to about 500 pm.

42. An absorbent cellulose I alginate-containing material as claimed in any one of claims 39 to 41 having a free swelling capacity of from 5 to 35 g / g as measured according to the examples when using an aqueous fluid which is 0.9% NaCI dissolved in deionised water.

43. An absorbent cellulose I alginate-containing material as claimed in any one of claims 39 to 42 having a retention capacity of from 5 to 35 g / g as measuredaccording to the examples when using an aqueous fluid which is 0.9% NaCI dissolved in deionised water.

44. A method of preparing an absorbent cellulose I alginate-containing material as claimed in any one of claims 39 to 43, said method comprising a process as defined in any one of claims 1 to 25.

45. A method as claimed in claim 44 which additionally comprises the step of recovering alginate, preferably sodium alginate.

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