Absorbent materials

Abstract

The invention provides absorbent articles which are formed from or which incorporate an absorbent cellulose / alginate-containing material, wherein said material is obtained by a process comprising 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 wet residue; and (iv) de-watering the residual wet residue whereby to provide said absorbent 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 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 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.

[0010] 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.

[0011] Summary of the invention

[0012] The inventors now propose that brown seaweed can be processed in a simple, cost-effective process to produce absorbent materials.

[0013] Brown seaweed is a source of commercially useful products for use in a variety of applications, for example in the food, cosmetics and pharmaceutical industries, as well as in agriculture and in animal feed. To obtain such products, it is generally necessary to process the macroalgae and, in many cases, to extract the products. This is the case for alginate which is a polysaccharide that can be extracted from brown seaweed. The polysaccharides in brown seaweed differ considerably from those found in terrestrial plants. Alginate is the main structural component of the cell wall of Laminaria hyperborea and is present at high concentrations in the main stem (the “stipe”). Cellulose is present in lower amounts. Whereas cellulose found in terrestrial plants, for example in wood, contains significant amounts of lignin and hemi-cellulose that must be chemically removed before it can be used in several of its applications, the cellulose obtained from seaweed does not contain either lignin or hemi-cellulose.

[0014] The inventors have now found that brown seaweed, or its component parts, can be reduced in size (e.g. chopped, milled or ground) to produce particulate materials which, once washed to remove water-soluble components, can be de-watered to produce dry seaweed residues (referred to herein as “cellulose I alginate-containing materials) which are capable of the absorption and retention of water and other aqueous fluids. 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.

[0015] 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.

[0016] Detailed description of the invention

[0017] 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.

[0018] The cellulose I alginate-containing materials comprise cellulose fibres and native 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. 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.

[0019] In one aspect, the invention thus provides an absorbent article comprising an absorbent cellulose I alginate-containing material, wherein said material is obtained by a process comprising at least the following steps:

[0020] (i) providing a brown seaweed, or part thereof;

[0021] (ii) dividing the brown seaweed, or part thereof, into a plurality of portions;

[0022] (iii) washing the plurality of portions with water whereby to remove water- soluble components and recovering the residual wet residue; and

[0023] (iv) de-watering the residual wet residue whereby to provide said absorbent cellulose I alginate-containing material as a dry residue.

[0024] 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.

[0025] 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.

[0026] 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. 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.

[0027] 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.

[0028] 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.

[0029] The process herein described may be performed in respect of any brown seaweed, or any part (or parts) thereof, that contains alginate. The native alginate present in seaweed has a high molecular weight and contains multi-valent cations which render it insoluble in water. Typically, the native insoluble alginate will comprise mainly calcium alginate.

[0030] 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. 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.

[0031] Laminaria spp. are particularly suitable, such as Laminaria hyperborea and Laminaria digitata, in particular Laminaria hyperborea.

[0032] 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.

[0033] 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.

[0034] Alginate is located in the structural tissues of the stipe of brown seaweed, for example in the stipe of Laminaria hyperborea. 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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 step. 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 the step of blending or milling.

[0040] 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.

[0041] 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.

[0042] 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). 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.

[0043] 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.

[0044] 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.

[0045] 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. For example, water washing of stipe may be conducted at ambient temperature for a period of from 10 to 60 minutes.

[0046] 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. For example, water washing of leaf (or whole seaweed where leaf parts are present) may be conducted at a temperature in the range of 30 to 70°C for a period of from 10 to 60 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. For example, any subsequent cold water wash may be conducted at ambient temperature for a period of from 10 to 60 minutes.

[0047] The step of water washing of the plurality of seaweed portions is effective to remove water-soluble components including, but not necessarily limited to, water- soluble salts. This step of the process is required to confer the desired absorbency properties on the final cellulose I alginate-containing material. The extent of removal of water-soluble components may be varied depending on the selected conditions of the washing step(s), but to maximise the absorbency of the final material, water washing will preferably be performed such that substantially all components of the seaweed that are water-soluble are removed.

[0048] The extent of removal of any water-soluble salts from the plurality of seaweed portions can be monitored during the water washing step by measurement of the conductivity of the drained water. 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.

[0049] The difference in the dry matter content of the plurality of seaweed portions before and after the water washing step also provides an indication of the extent of removal of water-soluble components as a result of the washing step. The step of water washing may be effective to remove at least 30% of the dry matter content of the seaweed portions, for example. Preferably, water washing will remove at least 40% of the dry matter content, for example at least 45%. More preferably, water washing will remove from 45 to 65% of the dry matter content of the seaweed. Dry matter content can be measured as set out in the examples.

[0050] 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.

[0051] In step (iv) 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.

[0052] 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.

[0053] In one embodiment, excess water may initially be removed in a process involving mechanical means such as mechanical pressing or centrifugation. Remaining water is then removed by other drying methods such as solvent drying and / or vacuum drying.

[0054] 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, acetone or ether. The use of propan-2-ol is particularly preferred.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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 or jet 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.

[0064] 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.

[0065] In one embodiment, the resulting dry cellulose I alginate-containing material will have a retention capacity of from 5 to 25 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 25 g / g, preferably 8 to 20 g / g, more preferably 10 to 20 g / g. Specific embodiments of the process of the invention are described in more detail with reference to accompanying Figures 1 and 2.

[0066] 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 initial size reduction to approx. 1 cm (e.g. by cutting), the stipe portions are washed by soaking in deionised water to remove salts and other water-soluble components (e.g. water-soluble sugars). The particle size of the stipe portions is further reduced to approx. 2-3 mm whilst in the washing solution. Further size reduction may be achieved by known methods, such as blending of the mixture. Following recovery of the solid fraction from the resulting mixture (e.g. by draining of the liquid), the conductivity of the separated liquid is measured to assess the extent to which salts have been removed from the seaweed. A conductivity of less than 200 pS is considered appropriate for further processing of the solid fraction. If the conductivity exceeds this value, the steps of soaking, further size reduction and water removal can be repeated. The resulting solid phase material that remains is a wet mass that contains cellulose fibres and native alginate. The wet residue is then de-watered, for example by initial centrifugation to remove the bulk of the water, followed by solvent dehydration using an alcohol such as propanol as an anti-solvent. Following initial separation of the solvent (e.g. by draining), the solid fraction is further processed to remove residual solvent, for example by centrifugation or decantation. The resulting solid material is then further dried (e.g. under vacuum at elevated temperature) to provide the final cellulose I alginate-containing material in granular form.

[0067] 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 initial size reduction to approx. 1 cm (e.g. by cutting). The leaf material is then washed by soaking in deionised water at high temperature to remove fucoidan and other water- soluble components (e.g. soluble sugars). The particle size of the leaf portions is further reduced to approx. 2-3 mm whilst in the washing solution. Further size reduction may be achieved by known methods, such as blending of the mixture. Following recovery of the solid fraction from the resulting mixture (e.g. by draining of the liquid), the leaf portions are subjected to further washing by soaking in water at ambient temperature. The solid and liquid fractions are then separated (e.g. by draining of the liquid). The conductivity of the separated liquid is measured to assess the extent to which salts have been removed from the leaf portions. A conductivity of less than 200 pS is considered appropriate for further processing of the solid fraction. If the conductivity exceeds this value, the washing steps can be repeated. The resulting solid phase material that remains is a wet mass that contains cellulose fibres and native alginate. The wet residue is then processed in the same way as described above in respect of the stipe portions.

[0068] As a result of the methods used to process the seaweed materials, 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.

[0069] 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.

[0070] Specifically, the invention provides an absorbent cellulose I alginate-containing material, wherein said material is obtained by a process comprising the following steps:

[0071] (i) providing a brown seaweed, or part thereof;

[0072] (ii) dividing the brown seaweed, or part thereof, into a plurality of portions;

[0073] (iii) washing the plurality of portions with water whereby to remove water- soluble components and recovering the residual wet residue; and

[0074] (iv) de-watering the residual wet residue whereby to provide said absorbent cellulose / alginate-containing material as a dry residue.

[0075] 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.%.

[0076] 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. Particle size can be determined by known methods, such as those herein described.

[0077] 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.

[0078] In one embodiment, the absorbent cellulose I alginate-containing material will have a retention capacity of from 5 to 25 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 25 g / g, preferably 8 to 20 g / g, more preferably 10 to 20 g / g.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] In the environmental and agricultural sectors, absorbent materials may find use in improving water retention in soil.

[0084] 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.

[0085] In a further aspect the invention thus provides a method of producing an absorbent article which is formed from or which incorporates a cellulose I alginate-containing material, said process comprising at least the following steps:

[0086] (i) providing a brown seaweed, or part thereof; (ii) dividing the brown seaweed, or part thereof, into a plurality of portions;

[0087] (iii) washing the plurality of portions with water whereby to remove water- soluble components and recovering the residual wet residue;

[0088] (iv) de-watering the residual wet residue whereby to provide a dry residue;

[0089] (v) optionally reducing the particle size of the dry residue; and

[0090] (vi) forming an absorbent article from the resulting absorbent cellulose I alginate-containing material or incorporating the resulting absorbent cellulose I alginate-containing material into an absorbent article.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.%.

[0095] 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.%. In the case where the absorbent materials herein described are used in a diaper in place of known superabsorbent polymers, it will be understood that the diaper will be substantially free from (e.g. free from) other superabsorbent polymers, in particular non-biodegradable superabsorbent polymers such as sodium polyacrylate.

[0096] Any of the articles or products listed herein which incorporate an absorbent material as herein described also form part of the invention.

[0097] 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.

[0098] 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).

[0099] 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 native alginate from a brown seaweed, and wherein said material is obtained by a process as herein described.

[0100] The invention will be described in more detail by way of the following non-limiting examples and the accompanying figures in which:

[0101] 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.

[0102] 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.

[0103] Figure 3 shows a comparison of the free swelling capacity of the cellulose I alginate-containing materials produced in Examples 1-5 vs. Kraft cellulose pulp PW411.

[0104] Figure 4 shows a comparison of the retention capacity of the cellulose I alginate-containing materials produced in Examples 1-5 vs. Kraft cellulose pulp PW411.

[0105] Examples

[0106] Materials:

[0107] Kraft cellulose pulp PW411 (“fluff pulp”).

[0108] Laminaria hyperborea harvested near Haugesund, Norway.

[0109] Fucus serratus collected from North Landing, Flamborough, UK.

[0110] Laminaria digitata collected at low tide from North Landing, Flamborough, UK.

[0111] Measurement methods:

[0112] 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. Free Swelling

[0113] Free swelling of sample materials was determined according to the following method and calculation:

[0114] Method:

[0115] 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 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).

[0116] Calculation:

[0117] The weight of the dry sample (W4) was calculated: W4 = (W2-W1).

[0118] The mass of fluid absorbed by the sample (W5) was calculated: W5 = (W3-W1). The % swelling of the sample was calculated: ((W5-W4) / W5)*100.

[0119] 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).

[0120] Retention Capacity

[0121] The ability of the sample to retain fluid (i.e. its retention capacity) was determined according to the following method and calculation:

[0122] Method:

[0123] 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 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).

[0124] Calculation:

[0125] The weight of the dry sample (W4) was calculated: W4 = (W2-W1).

[0126] The mass of fluid absorbed by the sample (W5) was calculated: W5 = (W3-W1).

[0127] The mass retention (%) of the sample was calculated: ((W5-W4) / W5)*100.

[0128] 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).

[0129] Dry matter content

[0130] 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.

[0131] Materials:

[0132] Drying dish

[0133] Balance (4 place)

[0134] Oven (103 7.2°C)

[0135] Method:

[0136] 1) Label empty aluminium weighing dish with the sample I.D. and place onto the balance. Record the empty weight (Dish).

[0137] 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.

[0138] 3) Place dish in oven at 103+ / . 2°C and allow drying for 4 hours.

[0139] 4) After 4 hours remove the dish from the oven and allow cooling for 5 minutes.

[0140] 5) Re-weigh the dish and record the dried weight (DRY).

[0141] 6) Calculate residue weight (Dry - Dish) and record on sheet (RES).

[0142] Result is expressed as solids on drying (dry matter) %:

[0143] Dry matter % = (Res / Sample) x 100 Particle size

[0144] 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.

[0145] Example 1

[0146] Preparation of absorbent cellulose / alginate-containing material from stipe of Laminaria hyperborea

[0147] Method:

[0148] 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. The sample was then centrifuged for 5 minutes using a “SI A Centri 772 SEK” spin dryer (2800 rpm generating a g-force of 960) to remove as much free water as possible, 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 reuse). 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.

[0149] The final product was a light green 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. This is evidence that no ion-exchange has taken place, i.e. the alginate in the product remains cross-linked (for example, by Ca2+ions) as in the initial raw material.

[0150] Free swelling and retention capacity of the product were determined and compared to a sample of Kraft cellulose pulp PW411. The following results were obtained:

[0151] Example 2

[0152] Preparation of absorbent cellulose / alginate-containing material from leaf of Laminaria hyperborea

[0153] Method:

[0154] Frozen 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 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 steps 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 further reduced to between about 2-3 mm by blending with a Tefal “Blendforce” BL42 blender (600W), using 2 x 5 second bursts per cycle. The sample was then centrifuged 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, 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 be 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 is 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.

[0155] The final product was a dark green 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. This is evidence that no ion-exchange has taken place, i.e. the alginate in the product remains cross-linked (for example, by Ca2+ions) as in the initial raw material.

[0156] Free swelling and retention capacity of the product were determined and compared to a sample of Kraft cellulose pulp PW411. The following results were obtained:

[0157] Example 3

[0158] Preparation of absorbent cellulose / alginate-containing material from whole Fucus serratus

[0159] Method:

[0160] Fresh Fucus serratus was milled using a Ninja food processor model BN650K (800W) to produce approx. 1 cm pieces. The milled 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.

[0161] The particle size of the resulting solid fraction was further reduced to between about 2-3 mm by blending with a Tefal “Blendforce” BL42 blender (600W), using 2 x 5 second bursts per cycle. The sample was then centrifuged 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, 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.

[0162] The final product was a light green 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. This is evidence that no ion-exchange has taken place, i.e. the alginate in the product remains cross-linked (for example, by Ca2+ions) as in the initial raw material.

[0163] Free swelling and retention capacity of the product were determined and compared to a sample of Kraft cellulose pulp PW411. The following results were obtained:

[0164] Example 4

[0165] Preparation of absorbent cellulose / alginate-containing material from stipe of Laminaria digitata

[0166] Method:

[0167] Stipe from fresh L. digitata 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. The sample was then centrifuged for 5 minutes using a “SI A Centri 772 SEK” spin dryer (2800 rpm generating a g-force of 960) to remove as much free water as possible, 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 reuse). 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.

[0168] The final product was a light green 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. This is evidence that no ion-exchange has taken place, i.e. the alginate in the product remains cross-linked (for example, by Ca2+ions) as in the initial raw material.

[0169] Free swelling and retention capacity of the product were determined and compared to a sample of Kraft cellulose pulp PW411. The following results were obtained:

[0170] Example 5

[0171] Preparation of absorbent cellulose / alginate-containing material from leaf of Laminaria digitata

[0172] Method:

[0173] Leaf from fresh L. 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 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.

[0174] The particle size of the resulting solid fraction was further reduced to between about 2-3 mm by blending with a Tefal “Blendforce” BL42 blender (600W), using 2 x 5 second bursts per cycle. The sample was then centrifuged 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 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 500pm.

[0175] The final product was a dark green 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. This is evidence that no ion-exchange has taken place, i.e. the alginate in the product remains cross-linked (for example, by Ca2+ions) as in the initial raw material.

[0176] Free swelling and retention capacity of the product were determined and compared to a sample of Kraft cellulose pulp PW411. The following results were obtained:

[0177] 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 is obtained by a process comprising 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 wet residue; and(iv) 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 in particulate form.

5. An absorbent article as claimed in claim 5, 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.

6. 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.

7. An absorbent article as claimed in any one of the preceding claims, wherein said material has a retention capacity of from 5 to 25 g / g as measured according to the examples when using an aqueous fluid which is 0.9% NaCI dissolved in deionised water.

8. 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.

9. An absorbent article as claimed in any one of the preceding claims, wherein said material is obtained by a process in which step (iii) is effective to reduce the dry matter content of the plurality of portions by at least 30%, preferably by 45 to 65%.

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) is performed until the washing water drained from the plurality of portions has a conductivity of less than about 200 pS.

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) is carried out by solvent dehydration, direct drying or vacuum assisted drying.

12. An absorbent article as claimed in claim 11 , wherein said material is obtained by a process in which step (iv) is carried out by solvent dehydration, preferably using a solvent selected from propanol, acetone, ethanol and ether.

13. An absorbent article as claimed in claim 12, wherein step (iv) is carried out by propanol dehydration.

14. An absorbent article as claimed in any one of the preceding claims, wherein said material is obtained by a process in which, after step (iii) and prior to step (iv), the residual wet residue is processed whereby to fibrillate the cellulose component.

15. 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.

16. An absorbent article as claimed in claim 15, wherein said material is obtained by a process in which the brown seaweed is Laminaria hyperborea, Laminaria digitata orFucus serratus, preferably Laminaria hyperborea.

17. An absorbent article as claimed in claim 16, wherein said material is obtained by a process in which the brown seaweed is Laminaria hyperborea.

18. 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.

19. An absorbent article as claimed in claim 18, wherein said material is obtained by a process in which the stipe is unpeeled.

20. 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.

21. An absorbent article as claimed in any one of claims 1 to 19, wherein the cellulose I alginate-containing material is incorporated into a fibrous carrier matrix which forms part or all of said article.

22. An absorbent article as claimed in claim 21 , wherein the fibrous carrier matrix is provided in the form of a sheet, layer, pad or film.

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

24. 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.

25. An absorbent article as claimed in claim 24, 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.

26. An absorbent article as claimed in claim 25, wherein the absorbent layer is additionally impregnated with a superabsorbent polymer, preferably sodium polyacrylate.

27. An absorbent article as claimed in claim 24 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.

28. A method of producing an absorbent article which is formed from or which incorporates an absorbent cellulose I alginate-containing material, 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 wet residue;(iv) de-watering the residual wet residue whereby to provide a dry residue;(v) optionally reducing the particle size of the dry residue; and(vi) forming an absorbent article from the resulting absorbent cellulose I alginate-containing material or incorporating the resulting absorbent cellulose I alginate-containing material into an absorbent article.

29. A method as claimed in claim 28, wherein the absorbent cellulose I alginate- containing material is produced by a process as defined in any one of claims 1 to 19.

30. A method as claimed in claim 28 or claim 29, wherein the absorbent article is as defined in any one of claims 20 to 27.

31. Use of a cellulose I alginate-containing material as an absorbent, wherein said material is obtained by a process as defined in any one of claims 1 to 19.

32. Use as claimed in claim 31 , wherein said cellulose I alginate-containing material is formed or shaped into, or otherwise incorporated into an absorbent article as defined in any one of claims 20 to 27.

33. An absorbent cellulose I alginate-containing material, wherein said material is obtained by a process as defined in any one of claims 1 to 19.

34. An absorbent cellulose I alginate-containing material as claimed in claim 33 which is in particulate form.

35. An absorbent cellulose I alginate-containing material as claimed in claim 34 having an average particle size in the range from about 250 to about 600 pm, preferably about 250 to about 500 pm.

36. An absorbent cellulose I alginate-containing material as claimed in any one of claims 33 to 35 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.

37. An absorbent cellulose I alginate-containing material as claimed in any one of claims 33 to 36 having a retention capacity of from 5 to 25 g / g as measured according to the examples when using an aqueous fluid which is 0.9% NaCI dissolved in deionised water.

38. A method of preparing an absorbent cellulose I alginate-containing material as claimed in any one of claims 33 to 37, said method comprising a process as defined in any one of claims 1 to 19.

Images