DESCRIPTION Technical field of the invention

The present invention relates to a new disposable compostable absorbent product for bodily fluids and solids. Particularly it relates to a compostable diaper comprising superabsorbent polymers with high capabilities of absorbing bodily fluids.

State of art

The disposable absorbent products for bodily fluids and solids, defined more precisely as disposable absorbent aids such as for example adult diapers, diapers and sanitary towels for feminine hygiene are products extremely widespread among population.

Since their first appearance up to now the diapers have greatly developed and they represent a concrete help in improving the quality of users' life. Generally, such products have improved in terms of ease of use and capability of absorbing bodily fluids and solids. However, the need is much felt for providing products which apart from satisfying practicality requirements and having high absorption performances have also a low environmental impact.

In fact, it is known that the disposable absorbent products of this type constitute daily a huge mass of waste which in some cases, above all in urban areas, constitutes even 10% of the overall produced waste.

Therefore, it is extremely important to provide absorbent products which can be disposed of together with the recycling organic fraction, assigning them to the composting and/or anaerobic digestion for producing compost, biogas or biomethane according to current laws.

However, several disposable absorbent products described in the state of art are not biodegradable and compostable or they have not adequate performances in terms of absorption or comfort for the user.

The state of art as above reconstructed then highlights the need for providing disposable absorbent products for bodily fluids and solids, particularly diapers, having high performances but which are also compostable.

Summary of the invention

The technical problem placed and solved by the present invention is then to provide a disposable absorbent product for bodily fluids and solids, particularly diapers, compostable, with high performances, particularly in terms of absorption of fluids. Such problem is solved by an absorbent product according to claim 1 .

Preferred features of the present invention are set forth in the depending claims.

An additional advantage of the product the present invention relates to is its capability of producing biomethane. As shown in detail in the description the diapers implemented according to the present invention can be used in digestion apparatuses suitable for producing biogas.

Other advantages, features and use modes of the present invention will result evident from the following detailed description of some embodiments, shown by way of example and not for limitative purposes.

Brief description of the figures

The figures of the enclosed drawings will be referred to, wherein:

^■ Figure 1 shows a perspective view of a first preferred embodiment of the product according to the present invention; ■ Figure 2 shows a schematic section view of the embodiment of figure 1 .

^■ Figure 3A shows the methane production speed by using as starting material the absorbent product according to the present invention.

^■ Figure 3B shows the degradation speed

Detailed description of the invention

In the present description under the term disposable absorbent product for bodily fluids and solids one refers to products such as diapers, adult diapers, sanitary towels for the feminine hygiene and other similar products. Based upon the use destination, each absorbent product will have suitable shape and sizes, in order to better adapt to the user's anatomical configuration.

In the present description under the term compostable product one relates to a product which after its natural or industrial degradation transforms into compost. According to what defined in current 13432EU law a product, in order to be considered compostable, has to degrade in less than 3 months. More in details, the compostability is the result of 4 tests:

1 ) the product has to degrade at least by 90% in 6 months if subjected to an environment rich in carbon dioxide; 2) if the product is in contact with organic materials for a period of 3 months, the material mass has to be constituted at least by 90% of fragments with sizes lower than 2 mm;

3) the product must not have negative effects on the composting process (toxicity of materials); 4) the product has to have low concentration in the additivated heavy metals.

By firstly referring to Figures 1 and 2, a disposable compostable absorbent product according to a preferred embodiment of the invention is designated as a whole with 100. Said disposable absorbent product is a multi-layer product wherein the different layers are substantially bidimensional elements, that is having a reduced thickness and with a development in length greater than in width as it can be seen from figures.

Said absorbent product comprises an absorbent layer 8, 9 and 10 characterized by an absorbent core comprising or constituted substantially by cellulose 9, particularly by cellulose of biodegradable vegetable origin not treated with chlorine-based bleaching agents, mixed with a superabsorbent polymer of alkyl cellulose, wherein said alkyl cellulose is selected from carboxymethyl cellulose (CMC), Hydroxyethyl cellulose, methyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose or mixtures thereof. Preferably a superabsorbent polymer of carboxymethyl cellulose (CMC) will be used.

The cellulose apart from the superabsorbent polymer of CMC is mixed with sodium polyacrylate granules 8 in an amount from 0 up to 30% by weight with respect to the absorbent core, particularly between 5 and 15%.

According to an embodiment the cellulose is defibrated during the production process so as to obtain a cellulose pulp which is mixed with the sodium polyacrylate granules (SAP) and with the superabsorbent polymer of carboxymethyl cellulose (CMC). In the absorbent core the cellulose has the function of absorbing and spreading the liquids inside the absorbent core, SAP and CMC have the function of absorbing liquids. The quantity of SAP, CMC and cellulose could vary according to the type and sizes of the product, for example according to the size of the diaper, but the quantity of SAP will be always so as to keep the compostability feature of the end product.

In the Italian patent IT102013902127561 (IT1614349) and in the European patent application n. 14710982.1 , herein incorporated by reference, superabsorbent polymers and the processes for the preparation thereof are described. Such polymers are suitable to be used in the absorbent products according to the present invention. Particularly, according to an embodiment a superabsorbent polymer of CMC will be used, obtained by cross-linking in an aqueous solution having a pH equal to or higher than 7.5, preferably by using NaHC03as alkalizing agent.

Still more preferably a superabsorbent polymer of CMC will be used, crosslinked with a cross-linking agent chosen among boric acid, boronic acid, borax or an ester thereof, preferably in a concentration between 2 and 8% with respect to CMC.

According to an embodiment in the absorbent core superabsorbent polymers of CMC will be used, prepared according to this process: a) preparing an aqueous solution having a pH equal to or higher than 7.5 comprising alkyl cellulose and at least a crosslinking agent, wherein said alkyl cellulose has a concentration by weight between 2 and 10% and wherein said cross-linking agent is selected among boric acid, boronic acid, borax or an ester thereof in a concentration between 2 and 8% with respect to said alkyl cellulose; b) performing the cross-linking reaction by obtaining a gel; c) drying the gel.

Performing the cross-linking reaction at a temperature comprised between 25° and 80°C for a period of time of at least 1 hour. Preferably using NaHC03 as alkalizing agent.

The absorbent layer could comprise additional suitable components, for example anti-odour elements, selected so as not to make the product not compostable.

Said disposable absorbent product further comprises an element 10 enveloping the absorbent core. Such element is made of biodegradable and compostable material, in particular it consists of a sheet of preferably pure cellulose pulp. The function of such enveloping element 10, commonly defined "flimsy element" is to keep cohesive the absorbent core and to avoid the dispersion of SAP, CMC and cellulose pulp.

Above the absorbent layer, in particular above the flimsy element there is an imbibing layer 12 made of biodegradable material too, for example starch fibre. The imbibing layer 12 has a filtering function which facilitates the absorption of the liquids in the absorbent core, since it allows to spread the liquids along the surface of the absorbent core. The imbibing layer 12 has funnel-shaped micro- holes (micro-perforations), the particular conical shape (wide mouth) conveys the fluids in the direction of the absorbent core 8, 9 and the narrow cone prevents the liquids from re-emerging towards the upper layers. According to a preferred embodiment said imbibing layer 12 has at least 80 holes/cm ² , preferably about 100 holes/cm ² and/or it is not treated with surfactants.

The imbibing layer will be made of bioplastics which differently from other plastic materials, is biodegradable and compostable. Particularly it will be a biopolymer obtained from starch fibre, for example bioplastics derived from renewable vegetable raw materials will be used, such as the one commercialized by NOVAMONT with the trade name mater-bi®.

Said disposable absorbent product further comprises a filtering layer 2, intended, in use, to be in contact with the user's skin, and a protective layer 6, suitable for forming the most external layer of the product to prevent any organic fluids from leaking out, thus being able to be placed in case in contact with the user's clothes.

The function of the filtering layer 2, commonly also defined as topsheet, is to filter the fluids towards the underneath layers and to prevent them from re-emerging.

The filtering layer 2 is made of biodegradable and compostable material. According to an embodiment it is made of non-woven fabric of polylactic acid (PLA), more particularly with polylactic acid fibres (PLA) linked therebetween by means of a thermal process, or with known technology called "spunbond". As it is known, the polylactic acid PLA, or polylactate, is a thermopolymer produced by the fermentation of the starch which results to be not biodegradable under natural conditions, but it becomes so at temperatures higher than 60°C, humidity higher than 20% and in presence of suitable microorganisms.

The protective layer 6, commonly also defined as backsheet, is the most external layer of the absorbent product 100 and it is made of biodegradable and compostable bioplastics. In particular with a biopolymer obtained from starch fibre, for example bioplastics derived from renewable vegetable raw materials will be used such as the one commercialized by NOVAMONT with the trade name mater-bi®.

According to an embodiment the layer thickness will be higher than 20 pm in order to have better resistance and breathability features to create a barrier preventing the fluids from leaking out towards outside.

Said absorbent product further comprises blocking elements 5 apt for holding the organic solid waste. The two blocking elements are arranged laterally to the multilayer structure as represented schematically in the figures. The barriers are formed by biodegradable and compostable textile material and they have the function of preventing the liquids from leaking out laterally, at least for a period of time sufficient to allow the absorbent core 8, 9 to acquire the whole or most part of the liquid/fluid ejected by the subject wearing the absorbent product 100 and at the same time to keep the bodily solids or semisolids until the moment of replacing the same manufactured product with a similar one.

Preferably, said filtering layer 2 and/or said protective layer 6 extend for the whole development of the absorbent product 100, by mainly defining the geometry and the sizes thereof.

According to an embodiment the blocking elements 5 are made of non-woven fabric of polylactic acid (PLA), more particularly with polylactic acid fibres (PLA) linked therebetween by means of thermal process, or with known technology called "spunbond". As it is known, the polylactic acid PLA, or polylactate, is a thermopolymer produced by the fermentation of the starch which results to be not biodegradable under natural conditions, but it becomes so at temperatures higher than 60°C, humidity higher than 20% and in presence of suitable microorganisms.

Said absorbent product could further include a closing system 1 ,3,4, preferably a mechanical system repositionable one or more times. The closing system reduces the risks of leaks of dejections and it allows to check the absorbent product 100.

The closing system could be made of polyethylene or polypropylene or polyester. According to the embodiment shown in figure 1 and 2 the closing system comprises a first frontal tape 1 positioned outside the diaper in the front portion made of a film whereon a gauze is glued and it can be made of polyamide or polyester. The closing system further comprises a pair of backers 3 positioned on both rear sides of the product (under rear side the diaper portion resting upon the child's back is meant), such elements preferably will be made of trilaminate of textile+elastomer+ textile. Being made of elastic material such backers 3 allow the diaper to adapt to the different waistlines of children. On these backers 3 in the final portion (the side not glued to the diaper) a second tape 4 is glued, for example made of polyethylene, having hooking means which allow to close the product by anchoring to the gauze existing on the first frontal tape 1 . According to an embodiment the absorbent product comprises additional backers 7 apt to wrinkle the blocking elements 5 and the protective layer 6 so as to create a "bath tube" effect which contains bodily fluids and solids or semisolids. Such backers 7 can be made of polyethylene or polypropylene or polyester.

According to an embodiment the several layers composing the absorbent product are joined together by means of thermoplastic glues, existing in minimum percentage, that is less than 3% with respect to the overall weight of the other layers.

The thermoplastic glues have an application temperature not higher than 175°C in order not to deteriorate the chemical-physical features of the natural materials composing the absorbent product. Static test for determining the Biochemical Methane Potential (BMP)

The absorbent product according to the present invention was subjected to a static test for determining the Biochemical Methane Potential (BMP) according to UNI EN ISO 1 1734:2004 Norm by using a digestor of type C9. Hereinafter the table with the obtained results:

Final Results:

BMP - Methane: 240.8 [Nm ³ Λ SV] 220.8 [Nm ³ /in the unaltered state] BMP - Biogas: 494.8 [Nm °/t SV] 453.5 [Nm °/t in the unaltered state]

SMeq ^(6): 1 .99 [t/t SMst] Neq ^(7): n.d. [kgN/Nm ³ cm]

(1) UNI EN ISO 1 1734:2004 Norm - Water quality - Evaluation of the last anaerobic biodegradability of organic compounds in digested muds - Method for measuring the biogas production

(2) Ratio by weight between the inoculum Volatile Solids and the substrate Volatile Solids

(3) Kmax: maximum speed of degradation of volatile solids

(4) Fmax: maximum degradability of the volatile solids of the substrate subjected to test (gross of moles of H 20 for hydrolysis of Volatile Solids)

(5) F50% and F90%: time interval wherein respectively 50% and 90% is reached of degradation of volatile solids of the substrate subjected to test

(6) Quantity of equivalent SiloMais (SMeq), considering a silage of standard mais (SMst): 33% of ST, 4% of ashes and BMP equal to 350 Nm

CH4/tSV, that is 1 10.9 Nm CH4/t tq

(7) Quantity of nitrogen to be handled per Nm3 of methane produced by the analysed matrix

The present invention has been sofar described with reference to preferred embodiments. It is to be meant that other embodiments belonging to the same inventive core may exist, as defined by the protective scope of the herebelow reported claims.