DESCRIPTION

TECHNICAL FIELD

The present invention relates to a nonwoven material (hereinafter also abbreviated to NW) suitable to absorb body fluids such as urine, blood, menses, body exudates, feces (in particular liquid feces). The nonwoven of the present invention is particularly suitable to be incorporated in absorbent articles such as articles for incontinence, sanitary pads, panty liners, diapers for babies, absorbent pads for use in the beds of incontinent or long-term care patients, sticking plasters and bandages. More in particular, the NW described is suitable to be used as sole substitution of the parts of the absorbent article intended to come into direct contact with the skin of the user ("Topsheet") and to distribute and acquire the body fluids (Acquisition Distribution Layer or simply ADL).

The subject matter of the invention is also an article incorporating said material and also a method of producing said material.

State of the art

Absorbent articles of hygienic type, such as diapers for babies, articles for incontinence, sanitary pads, panty liners, absorbent pads for use in beds of incontinent or long-term care patients, sticking plasters and bandages, must be able to maintain a surface of the product in contact with the skin of the user dry, i.e. improving the comfort of the product and reducing the occurrence of undesirable skin conditions, such as irritations caused by prolonged exposure of the skin to dampness.

As is known, body fluids can be viscous, such as in the case of menses or liquid feces. This viscosity makes the absorption process slow and at times ineffective, as the viscous material continues to adhere to the surface of the absorbent article. In these situations, it would be desirable to have an absorbent material capable of efficiently conveying the viscous fluid toward the inside of the absorbent article and, at the end of the process, having a cleaner surface, free from residues of the viscous material. In this way skin irritations caused by contact with liquid feces or with menses could be further limited.

A very important parameter, together with the rapid acquisition of biologic fluids, is the ability of the absorbent material not to return the aforesaid fluids toward the skin of the user if subjected to pressure (known as 'rewet'). In the hygiene sector, low rewet is commonly sought through the use of topsheets consisting of films made of perforated hydrophobic material. However, these materials are not marked by softness or by a particularly pleasant handle.

The patent EP 0 767 646 B 1 describes absorbent materials exhibiting a surface energy gradient. In one of the preferred embodiments of this invention, the material consists of a perforated plastic film ("perforated topsheet") having a portion of the film with a lower surface energy than the portion of film below. Establishing a surface energy gradient helps the fluid to be conveyed toward the inner layers of the product to be absorbed rather than tending to return toward the surface in contact with the skin of the user.

The patent EP 0235309 B l describes an absorbent material particularly suitable to be used as topsheet and characterized by remaining, in the part in contact with the body, particularly dry after absorption of body fluids. The absorbent material preferably consists of two fibrous layers formed of different types of fibers. The first fibrous layer intended to come into contact with the skin consists of 70 - 100 % of hydrophobic fibers having a basis weight of at least 15 g/m2 and having apertures with an area of 0.29-30 mm2 formed in this first layer at a ratio of 10 to 50 % with respect to the total area. The secondary layer is composed of 50-100 % by weight of hydrophilic fibers, has a basis weight of 5-50 g/m2 and has no apertures. The materials described are produced by the action of water jets. Joining of the two layers takes place on the whole of the surface.

This last example does not appear adequate for viscous fluids, at least in terms of acquisition time, besides not being particularly soft or flexible. Moreover, it appears to be complex and expensive to produce.

Object and summary of the invention

The object of the present invention is to produce an absorbent material capable of rapidly absorbing fluids, while maintaining softness.

Within this object, another important object is that of producing a material that combines the functions of a topsheet and of a layer suitable for acquisition and distribution of liquids, having the benefits already present at the state of the art and further increased with respect to these.

Moreover, another important object of the present invention is that of producing an absorbent material capable of limiting rewet similar to those of current perforated films, but marked by increased softness and fabric handle. Yet another object of the present invention is that of implementing a method to produce an absorbent material with the aforesaid advantages, which is inexpensive and simple to produce.

These and other objects are achieved with an absorbent material comprising a nonwoven provided with two opposite faces, a first face intended to face the area from which the fluid to be absorbed arrives and a second opposite face; the nonwoven has a first fibrous layer defining the first face, and a second fibrous layer secured to the first layer on the opposite side with respect to the first face, defining said second face; at least a part of the fibers of the first layer are hydrophobic, while at least a part of the fibers of the second layer are hydrophilic, so that the first layer has hydrophobic properties while the second layer has hydrophilic properties; first impressions are provided on the first face of the NW; for each first impression, a second impression is present on the second face of the NW; therefore they have the same number of first and second impressions; more in particular, each second impression is centered with the respective first impression; the two layers are joined at the bottoms of said impressions; the corresponding pairs of first and second impressions being channels for acquisition of the fluid from said first face toward said second face.

In practice, the material according to the invention comprises a nonwoven formed by the combination of at least two materials, stratified one on top of the other. At least one of these different layers is more hydrophobic with respect to the other layer, a result that can be obtained using a mixture of fibers for the first layer as a whole more hydrophobic with respect to the mixture of fibers used for the second layer.

At the bottoms of these centered pairs of impressions, the two layers lose their original properties, creating a surface with hybrid properties, which has surprisingly been found to have high energy due to the simultaneous presence of hydrophilic and hydrophobic materials. This surface therefore has mixed mechanism in relation to the passage of body fluids, also facilitated by the channel shape on both the faces. Some fibers of the lower layer, more hydrophilic, can be forced to pass through the upper layer, having the possibility of coming into contact with the surface. Moreover, some fibers of one layer and of the other layer in the joining areas at the bottoms of respective impressions can integrate with one another, giving rise to fibers with mixed properties that facilitate passage through the double channel. In the present description, the term "impression" means an area that is sunken with respect to an upper level. Necessarily, an impression according to the present description is not a through hole, i.e. each impression always has a bottom and walls and is open at the face on which it is generated.

In practice, the absorbent material of the invention has no through perforations at said impressions.

Preferably, the materials of the present invention formed by coupling a first layer, as a whole hydrophobic, typically facing upward during use, (i.e. an upper layer) with a second layer as a whole hydrophilic (i.e. a lower layer).

In some embodiments, the fibers of the first layer are all hydrophobic.

In some embodiments, the fibers of the second layer are all hydrophilic.

Hydrophobic fiber is intended both as a fiber by nature provided with hydrophobic properties, and as a fiber treated to make it hydrophobic, for example with appropriate finishing techniques.

Analogously, hydrophilic fiber is intended both as a fiber by nature provided with hydrophilic properties, and as a fiber treated to make it hydrophilic, for example with appropriate finishing techniques.

According to preferred embodiments, the first and the second layer are thermally bonded together substantially for the whole of their surface extension, while the bottoms of said first and second impressions are heat welded together.

According to other embodiments, the bottoms of said impressions are the only joining areas between the two layers and the first and the second layer are not thermally bonded together prior to the production of said impressions.

According to preferred embodiments, the fibers of said first layer of nonwoven are of crimped type.

According to preferred embodiments, the fibers of said second layer of nonwoven are of crimped type.

According to preferred embodiments, the first impressions on said first layer of nonwoven and second impressions on said second layer of nonwoven are obtained by means of the passage through a calender, said two layers being joined together by thermal melting at the bottoms of said impressions.

According to preferred embodiments, the overall area of the bottoms of said first impressions is between 25% and 25% of the total area, and more preferably between 5 and 15%. According to preferred embodiments, the number of said first impressions is between 1 and 30 per cm ^A 2, and more preferably between 5 and 15.

According to preferred embodiments, the dimensions of said first impressions are between 0.1 mm ^A 2 and 10 mm ^A 2, and more preferably between 0.5 mm ^A 2 and 5.0 mm ^A 2.

For example, the first and the second layer can be produced with fibers (used alone or mixed together) with average linear density between 0.7 and 15 dtex, and more preferably between 1.0 and 6.7 dtex

According to preferred embodiments, the material according to the invention has a grammage between 15 and 150 grams per square meter (gsm), more preferably between 30 and 100 gsm and even more preferably between 40 gsm and 90 gsm.

Preferably, the weight of the first layer is between 10 and 50 grams per square meter.

Preferably the first layer can consist of 30 to 100 % of hydrophobic fibers and more preferably of 70 to 100 % of hydrophobic fibers.

Preferably, the denier of the fibers of the first layer can vary between 0.7 and 15 Dtex and more preferably between 1.0 and 4 Dtex.

Preferably, hydrophobic fibers useful for the first layer can comprise one or more of the following: polyester, polypropylene, polyethylene, acrylics, polyurethanes.

Preferably, the hydrophobic fibers are synthetic fibers.

Preferably, the hydrophobic fibers are thermoplastic fibers.

Preferably, the hydrophobic fibers are synthetic thermoplastic fibers.

Preferably, the second layer can consist of 30 to 100 % of hydrophilic fibers and more preferably of 70 to 100 % of hydrophilic fibers.

Preferably, the weight of the second layer can vary between 10 and 150 grams per square meter and more preferably between 20 and 80 grams per square meter.

Preferably, the denier of the fibers of the second layer can vary between 0.7 and 15 Dtex and more preferably between 2.0 and 10 Dtex.

Preferably, the hydrophilic fibers useful for the lower layer comprise, or consist of, one or more of the following: synthetic fibers such as polyester, polypropylene, polyethylene, polyurethane, the surface of which has been made hydrophilic, for example using a surfactant or a mixture of surfactants.

Advantageously, the hydrophilic fibers comprise, or consist of, synthetic fibers of thermoplastic type. Advantageously, the total thickness "s" of the material 10 (i.e. the thickness between the two faces 12 and 13) is between 0.25 and 5.0 mm, and more preferably between 0.5 and 2.5 mm.

Advantageously, the thickness "f ' of the bottom of the impressions (i.e. the thickness between the bottoms of a first and a second impression 16 and 17, arranged corresponding), is between 0.02 and 0.50 and more preferably between 0.03 and 0.25 mm. Advantageously the ratio between the total thickness s and the thickness of the bottom of the impressions f is between 3 and 30, and more preferably between 5 and 20.

The advantages of implementation of the present invention consist of providing a single absorbent product, not produced by means of coupling or lamination, which remains drier and cleaner on the surface after contact with the aforesaid body fluids. In particular, the advantages are evident even when the body fluids are much more viscous with respect to common watery fluids such as urine, such as in the case of particularly viscous menses and liquid feces.

A method of producing a material as described above provides for:

obtaining a first layer of nonwoven of hydrophobic fibers, preferably of crimped type,

obtaining a second layer of nonwoven of hydrophilic fibers, preferably of crimped type,

simultaneously creating first impressions on said first layer of nonwoven and second impressions on said second layer of nonwoven by means of their simultaneous passage through a calender comprising a first cylinder with surface protuberances and a second smooth cylinder, provided with a temperature between 70°C and 240°C, pressing against each other, counter-rotating and with substantially the same peripheral rotation speed; during the creating of said impressions said two nonwovens being joined together by thermal melting at the bottoms of said impressions.

Preferably, the first layer of nonwoven is adapted to come into contact with said first cylinder and said second layer of nonwoven is adapted to come into contact with said second cylinder. In other embodiments, the first layer of nonwoven is adapted to come into contact with said second cylinder and said second layer of nonwoven is adapted to come into contact with said first cylinder.

In preferred embodiments, the first layer of nonwoven and the second layer of nonwoven are formed starting from respective carding machines and bonded in a common oven, so that said two layers are already joined when they enter said calender. In other embodiments, the first layer of nonwoven and the second layer of nonwoven are formed starting from respective carding machines and bonded separately in the oven, so that said two layers are not already joined when they enter said calender and said joining takes place only by thermal melting at the bottoms of said impressions.

According to another aspect, the invention also relates to an absorbent article of hygienic type, such as diapers for babies, articles for incontinence, sanitary pads, panty liners, absorbent pads for use in beds of incontinent or long-term care patients, sticking plasters and bandages etc., which comprise a material as described above.

Preferably, this material in this article is arranged so as to come into direct contact with the skin of the user.

Preferably, this material in this article integrates a topsheet and an ADL, i.e. allows direct contact with the skin of the user and the simultaneous acquisition and distribution of body fluids.

Brief description of the drawings

Further characteristics and advantages of the invention will become more apparent from the description of some preferred but non-exclusive embodiments thereof, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Fig. 1 represents a production method according to the state of the art in which no impressions are created on the two faces in which intimate contact between the two layers is obtained, but through holes 116 on the first layer 114, closed at the bottom by the second layer 115;

Fig. 2 represents a diagram of the section of the material according to the invention, and corresponds to Example 1 cited below;

Fig. 3 represents a photograph of the first face of a nonwoven of the present invention; in particular, the material represented is the one described in Example 1;

Fig. 4 represents a photograph of a further example of the first face of a nonwoven of the present invention; in particular, the material has impressions of different dimensions;

Fig. 5 is an enlargement of around 50 times of Fig. 3;

Fig. 6 is an enlargement of around 50 times of Fig. 4; Fig. 7 represents a diagram of a system for producing a material according to the invention.

Detailed description of embodiments of the invention

Wettability of a material is intended as the tendency of the material to be easily wetted by watery fluids. A useful parameter for defining wettability is the contact angle that a drop of liquid forms with the solid surface (gas-liquid interface). In the case in which the wettability of the solid surface increases, the contact angle decreases. On the contrary, if the wettability of the surface decreases, the contact angle increases. The term "hydrophilic" or "hydrophilia" refers to surfaces or fibers that are wettable by watery fluids (for example, watery body fluids such as urine, blood or menses). Hydrophilia and wettability are typically defined in terms of contact angle and of surface tension of the fluids and of the solid surfaces involved. A surface is said to be wettable by a watery (hydrophilic) fluid when the fluid tends to spread spontaneously through the surface. On the contrary, a surface is considered to be hydrophobic if the fluid does not tend to spread spontaneously through the surface. The angle of contact depends on inhomogeneity (for example roughness), presence of contaminants, chemical or physical treatments, composition of the solid surface, nature of the fluid. Also, the surface energy of the solid influences the contact angle. If the surface energy of the solid decreases the contact angle increases. If the surface energy of the solid increases the contact angle decreases.

"Absorbent article" is intended as a device suitable to absorb and contain body fluids and more specifically it refers to devices that are arranged close to the body of the user to absorb and contain body fluids of various types emitted from the body of the user. The term "absorbent article" includes articles such as diapers for babies, sanitary pads, tampons for feminine hygiene, panty liners, absorbent articles for incontinence and similar products, including sticking plasters and bandages. The term "disposable" is intended as absorbent articles that are not intended to be washed or in any other way recovered and re-utilized as absorbent articles after initial use. (for example, these articles are disposed of as waste after initial use and, preferably, are recycled, composted or disposed of in another manner compatible with the environment). "Unitary" absorbent article is intended as an absorbent article formed from separate parts joined together to form a body coordinated so that said parts do not require to be handled by different equipment.

An absorbent article has two surfaces, a first surface, which in jargon is called "Topsheet", forming the part of the absorbent article that comes into contact with the body of the user, in particular with the skin of the user. The second surface, which in jargon is called "Backsheet", is positioned in the part opposite the Topsheet. The position of the Backsheet is also defined as "garment side".

An absorbent article generally consists of a Topsheet, an Acquisition Distribution Layer (ADL) that distributes the liquids, an absorbent core that traps the liquids and a Backsheet that prevents the passage of liquids toward the garments.

The topsheets currently most widely used for feminine hygiene are perforated films, as they have a high capacity to obstruct the return of liquids (term defined as 'rewet'). On the other hand, the perforated film is not particularly aesthetically pleasing, nor is it very soft or pleasant to the touch.

The material of the present invention can therefore also be defined as a combined topsheet and ADL, as it is provided, as shown in Fig. 2, with a first surface A that comes into in contact with the skin of the use and a second surface B that has the task of distributing the liquid to the layer below (core). It must be noted that the material forming the subject matter of the invention has a fabric handle and softness greatly superior to perforated films according to the state of the art.

With particular reference to Fig. 2 cited above, a material according to the invention is indicated as a whole with the number 10.

In this example, the absorbent material comprises a nonwoven (hereinafter also indicated with 10) with two opposite faces 12 and 13. It is formed by two layers, a first layer 14 and a second layer 15, joined together.

The first layer 14 is preferably intended for use as the upper layer with respect to the second layer 15 (which is therefore the lower) and to face the part from which the fluid to be absorbed arrives. For example, when the material 10 forms an absorbent article such as articles for incontinence, sanitary pads, panty liners, diapers for babies, absorbent pads for use in the beds of incontinent or long-term care patients, sticking plasters and bandages, etc., it is the first layer 14 that comes into contact with the skin of the user, or in any case is facing the user.

Therefore, the first layer 14 defines the first face 12 of the NW, while the second layer 15 defines a second face 13 of the NW.

The first layer 14 is fibrous and is formed substantially by hydrophobic fibers. Although in this example all the fibers are hydrophobic, in other examples only a percentage of these may have hydrophobic properties. Naturally, as a whole, for this first layer, the hydrophobicity must be greater with respect to hydrophilicity.

The second layer 15 is fibrous and is formed substantially of hydrophilic fibers. Although in this example all the fibers are hydrophilic, in other examples only a percentage of these may have hydrophilic properties. Naturally, as a whole, for this first layer, the hydrophilicity must be greater with respect to the hydrophobicity.

First impressions 16 are provided on the first face 12 of the NW 10. In particular, these impressions 16 do not pass through the whole of the thickness of the first layer 14 and therefore each define a respective first bottom 16A.

For each first impression 16, a second impression 17 is present on the second face 13 of the NW. Therefore, the first and second impressions are the same in number. Also in this case the second impressions 17 do not pass completely through the thickness of the second layer 15 and each define a respective second bottom 17A.

Each second impression 17 is centered on the respective first impression 16 and therefore, as can be seen in the figure, the corresponding pairs of first and second impressions define channels K for acquisition of the fluid from the first face toward the second face.

In this example, the impressions have an approximately circular surface and are centered, i.e. the centers of corresponding first and second impressions are coaxial.

The two layers 14 and 15 come into intimate contact by means of heat treatment at the bottoms 16A and 17A of said impressions 16 and 17, as better explained below.

Advantageously, the total thickness "s" of the material 10 (i.e. the thickness between the two faces 12 and 13) is between 0.25 and 5.00 mm, and more preferably between 0.5 and 2.5 mm.

Advantageously, the thickness "f ' of the bottom of the impressions (i.e. the thickness between the bottoms of a first and a second impression 16 and 17, arranged so that they correspond), is between 0.02 and 0.50 mm, and more preferably between 0.03 and 0.25 mm.

Advantageously, the ratio between the total thickness s and the thickness of the bottom of the impressions f is between 3 and 30, and more preferably between 5 and 20.

The two layers 14 and 15 are produced, for example, by means of carding processes of crimped fibers, in which thermoplastic fibers are present, with subsequent thermal bonding.

For example, plies of fibers relating to the first layer and those relating to the second layer are delivered from respective carding machines and are conveyed through a hot air oven, which operating at suitable temperature ranges cause the thermoplastic fibers to melt, bonding the respective plies, and thereby producing the two nonwovens that form the first and the second layer, characterized by high values of mechanical strength and thicknesses. The two plies of fibers can pass through the oven together and bond together, obtaining a single preliminary nonwoven already joined along the whole of its surface. Differently, the two plies of fibers can pass through the oven separately (or through different ovens) becoming bonded separately from each other, obtaining two preliminary nonwovens separate from each other. Subsequently, they can be joined together along the whole of their surface or only in areas, for example preferably in the areas corresponding to the common bottoms of the first and second impressions.

Preferably the thermoplastic fibers capable of melting are bicomponent fibers (concentric or eccentric core / sheath structures, or side to side structures) well known to those skilled in the art.

For example, the first and the second layer can be produce with fibers (used alone or mixed together) with average linear density between 0.7 and 15 dtex, and more preferably between 1.0 and 6.7 dtex. For example, the materials of these fibers are selected from one or more of the followings: polyesters, polyolefins, polyamides and combinations thereof. The polyesters can include PET, PBT, copolymers of polyester (e.g. low melting fibers based on isophthalic acid) and mixtures thereof. The polyolefins can include polyethylene PE, polypropylene PP, polybutene PB, copolymers and mixtures thereof.

Production lines provided with double (or multiple) carding machines can produce, directly and at low costs, the multi-layer material, without having to use techniques for coupling or lamination of the materials. This production mode is particularly beneficial as the various layers are strongly bonded by the melting of the bicomponent fibers, without having to use glues or other techniques that are known to have a negative influence on the permeability and on the degree of aperture of the nonwoven.

Before the carding step, the fibers are subjected to a finishing step to impart thereto hydrophilic (if related to the second layer) or hydrophobic (if related to the first layer) properties.

In particular, the hydrophilic finishing agents promote absorption or conveying of water and therefore help the wettability of the fibers. For example, some hydrophilic finishing agents for fibers usable in the present invention, without being limiting, are anionic surfactants (salts of fatty acids, esters of fatty acids, phosphoric esters, long-chain alkyl sulfates and alkyl sulfonates), non-ionic surfactants such as derivatives of polyethylene glycol or polysorbates, cationic surfactants such as quaternary ammonium salts, long chain alcohols, silicone based surfactants such as dimethicone-copolyols. Examples of commercial products for hydrophilic finishing are the finishes Silastol® PHP by Schill & Seilacher and Cirrasol® by CRODA (based on non-ionic surfactants and cationic antistatic agents), TEGOPREN® by Evonik and TEGO® by Degussa and Xiameter® by Dow-Corning (various silicone based formulations), or Z-QUAT™ by Evonik (cationic surfactants).

Hydrophobic finishing agents are instead used to increase the impermeability of the fibers in relation to water. Non-limiting examples of finishing agents are silicone oil derivatives, such as some belonging to the families TEGOPREN® by Evonik or Xiameter® by Dow-Corning or Silastol CUT 1 by Schill & Seilacher or the esters of fatty acids with long chain alcohols.

The hydrophobic value of the fibers of the first layer can be determined by means of the 'sinking time' test described below (Test Method 4). The fibers of the first layer must have a sinking time greater than 120 s, preferably greater than 600 s. The hydrophilic value of the second layer, is for example between 0 and 20 seconds, preferably between 0 and 5 seconds, again measured according to the 'sinking time' test described below (Test Method 4). Generally, the hydrophobic fibers themselves do not sink with the aforesaid method in times of less than 30 minutes.

As said, the two layers 14 and 15 are generally thermally joined by bonding in a single oven. Subsequently they are joined further, again thermally, at the bottoms 16A and 17 A of said impressions 16 and 17.

For example, as shown in Fig. 7, two continuous plies 14' and 15'of fibers that will form the first and the second layer 14 and 15, coming from carding stations CI and C2, are conveyed to a common solidifying oven F, which produces a preliminary bonded nonwoven 10' having the two layers 14 and 15. This preliminary bonded nonwoven 10' enters a calender that comprises two counter-rotating cylinders HI and H2.

The upper cylinder HI has surface protuberances with the same shape as the first impressions 16, while, in this example, the lower cylinder H2 is smooth. The protuberances are, in this example, truncated cone shaped.

Preferably, the lower cylinder H2 is rigid and hard, for example like steel or consists of an elastically yielding material like rubber. The two cylinders are pressed against each other, for example with pressure between 20 and 100 kg/cm ^A 2.

Preferably, the due cylinders HI and H2 have a surface temperature between 70°C and 270°C.

To prevent the assembly of the two layers 14 and 15 from being perforated with through holes during passage through the calender, the peripheral rotation speed of the two cylinders must be substantially the same. In fact, if this were not the case, different speeds would create slippage between the cylinders, which would tear the material being processed, producing holes.

The first impressions 16 are formed by the deformation of the protuberances of the upper cylinder HI. The second impressions 17, in the preferred examples in which the lower cylinder H2 is smooth, as in the present example, are also caused by the action of the pressure of the protuberances of the upper cylinder. In fact, the protuberances compress the first and the second layer in the point of maximum contact of the cylinders of the calender, to obtain maximum compression at what will become the bottoms of the first impressions 14, actually forming these first impressions. When the protuberances of the first cylinder HI start to move away from the second cylinder H2, the reaction of the material deformed during passage through the calender is that of creating on its second face 13 a deformation effect that creates depressions at the first impressions, which correspond to the second impressions 17.

The effect of the pressure and of the temperature cause melting of the hydrophobic fibers of the first layer 14 and hydrophilic fibers of the second layer 15 at the bottoms of the impressions 16 and 17. The two layers 14 and 15 are therefore joined in these areas (the bottoms of the impressions). Preferably, the bottoms of the impressions are the only areas of intimate interconnection of the fibers of the two layers. Here, as already mentioned, the two layers lose their original properties, creating a high-energy surface, with hybrid properties, due to the simultaneous presence of hydrophilic and hydrophobic materials. This surface therefore has a mixed mechanism in relation to the passage of part of the body fluids, facilitated by the channel shape K on both faces.

In other examples of embodiment, the preliminary bonded nonwoven 10' can enter the calender "overturned" with respect to what is described above, i.e. in this case with the first layer in contact with the second cylinder H2 and the second layer in contact with the first cylinder HI, so that the second impressions are produced directly by the protuberances of the first cylinder, while the first impressions are produced through a deformation effect of "reaction" of the material, as described above.

With regard to processes adapted to produce the type of impressions described in the present invention, procedures known in the state of the art can be used. For example, EP-A-0598970 describes a method and a system for producing a perforated material both in the form of film and of nonwoven. In accordance with this method, the material is sent to a calender comprising two counter-rotating cylinders. One of the two cylinders has protuberances while the other is substantially smooth and, if necessary can consist of an elastic cylindrical surface or can consist of a hard surface such as steel. The material is perforated through the combined effect of the pressure between the two cylinders, the temperature to which the cylinders are heated and the difference in the peripheral speed between the two cylinders. The cylinder equipped with the protuberances is faster than the smooth cylinder and this causes an effect of deformation and of detachment of the material on the protuberances. Other apparatus and methods adapted to perforate a nonwoven are described in the patents GB-B- 484929, DE-A2614160, US-A-3,085,608, EP-A-502273, US-A-3,509,007, US-A- 3,292,619. To adapt the systems and the methods described in these patents in order to obtain on the material being processed impressions and not through holes, it is necessary to prevent the cylinders of the calenders from rotating with different, or significantly different, speeds.

With regard to the shape of the first impressions (and, preferably, also of the second impressions), they have a circular plan section; it is understood that other shapes can also be used. For example, the impressions can have an oval, rectangular, star or irregular shape or be in a shape that represents patterns, such as flowers.

With regard to the dimension of the first impressions (and also of the second impressions), it can vary from 0.1 to 10 mm ^A 2 with regard to the single impression (measured on the edge of the impression relating to the first face). The number of first impressions 14 per square centimeter can vary from 1.0 up to 30.0.

According to preferred embodiments, the overall area of the bottoms of said first impressions is between 2.5% and 25% of the total area, and more preferably between 5% and 15%.

Figs. 3 and 4 (and related enlargements of Figs. 5 and 6) show two examples of materials produced according to the present invention. Fig. 3 shows an example in which the first impressions are all the same, while Fig. 4 shows an example in which the first impressions can be divided into groups of impressions with different dimensions, according to a desired pattern.

With regard to the process of obtaining the materials of the present invention, two modes can be used.

In the preferred mode, as shown in Fig. 7, the two layers of material are produced at the same time on the production line using, for example, two separate carding machines. The first carding machine can be used to produce the upper layer essentially consisting of hydrophobic fibers, while the second carding machine can be used to produce the lower layer essentially consisting of hydrophilic fibers. In this way, even if the two carding machines are in line, each carding machine is fed separately with different fibers or mixtures of fibers. The two layers exiting from the carding machines are laid on a conveyor belt one over the other and are sent to a hot air oven that bonds the layers both internally and together in the contact surface.

After being thermally bonded, the nonwoven is sent to the calender K where by operating as described previously the impressions are produced, so as to obtain the advantages of the invention.

As already mentioned, the material of the present invention consists of two layers of materials with a composition of fibers that is different from each other. More in particular, the upper layer (in this example, the first layer 14) as a whole is more hydrophobic than the lower layer (second layer 15).

The upper layer can consist of 30 to 100 % of hydrophobic fibers and more preferably from 50 to 100 % of hydrophobic fibers.

The grammage of the upper layer can vary from 10 to 50 grams per square meter.

The denier of the fibers can vary between 0.7 and 15 Dtex and more preferably between 1.0 and 4 Dtex. Hydrophobic fibers useful for the upper layer can consist of polyester, polypropylene, polyethylene, acrylics, polyurethanes, etc.

The lower layer can consist of between 30 and 100 % of hydrophilic fibers and more preferably between 70 and 100 % of hydrophilic fibers.

The grammage of the lower layer can vary from 10 to 150 grams per square meter and more preferably from 20 to 60 grams per square meter.

The denier of the fibers can vary between 0.7 and 15 Dtex and more preferably between 2.0 and 10 Dtex.

Hydrophilic fibers useful for the lower layer can consist of synthetic fibers such as polyester, polypropylene, polyethylene, polyurethane, the surface of which has been made hydrophilic, for example using a surfactant or a mixture of surfactants.

Other useful hydrophilic fibers can be represented by viscose, cotton, etc. Another type of fiber useful in the preparation of the lower layer consists of Super Absorbent Fibers (SAF), these fibers being of hydrophilic nature and also capable of tenaciously absorbing and retaining large quantities of fluid.

Test methods

Test Method 1 - "Acquisition and Rewet test"

An artificial menses solution obtained by mixing the following substances for 1 liter of aqueous solution is used for this test: 10 g of sodium chloride, 4 g of sodium bicarbonate, 100 g of glycerol, and 14 g of carboxymethyl cellulose (Sigma catalog code C5678). To make dissolution of the carboxymethyl cellulose easier, this latter is first mixed with the quantity of glycerol and the two components are then added to the aqueous solution.

The "Acquisition and Rewet" test is used to evaluate the absorbent properties of sanitary pads. The comparative tests can be implemented with a commercial product, substituting a layer of material (for example the topsheet) present in the commercial product with the product of interest. After having made the substitution, a replica of the commercial product is created by closing the structure and holding the various components in place with staples.

The materials required to carry out the test are a balance with sensitivity of 0.001 grams, a wetting plate consisting of a Plexiglas rectangle measuring 70 mm x 220 mm with an acquisition cylinder in central position with inner diameter 22 mm and height 47 mm. A cylindrical rewet weight of 5 kg with a diameter of 10 cm. A stopwatch. S&S absorbent paper grade 604, 79 gsm (grams per square meter), thickness 0.19 mm, dimensions 14 cm x 8.5 cm.

To carry out the test, the wetting plate is placed on the absorbent structure so as to have the acquisition cylinder in central position. 5 ml of artificial menses solution is collected with a pipette. The stopwatch is activated and, simultaneously, the volume of artificial menses is deposited in the center of the wetting cylinder placed on the pad. The stopwatch is stopped as soon as the artificial menses has passed completely from wetting cylinder to the absorbent structure. The acquisition time is recorded (Tl). After 10 minutes, a further 5 ml of liquid is deposited, measuring the second acquisition time (T2). After a further 10 minutes, the third and last 5 ml of artificial menses is deposited, measuring the third acquisition time (T3). The total acquisition time given by the sum of the single times T1+T2+T3 is then calculated. Finally, the absorbent paper is weighed (PI - the absorbent sheets must be sufficient in number that after the rewet the upper sheet remains dry). The sheets of absorbent paper are placed on the absorbent structure, taking care to position them centrally. The absorbent paper must be placed with the smooth side in contact with the sample. The rewet weight (5 kg) is placed on the sheets of absorbent paper, taking care to position it centrally with respect to the structure. The weight must be placed taking care not to exert additional pressure on the sample. Leave the weight to exert its pressure on the sample for 15 seconds. Lift the rewet weight and carefully remove the absorbent paper. Weigh the absorbent paper (P2). For each sample the test is repeated 5 times, calculating the average acquisition time in seconds and the standard deviation. The rewet is calculated by calculating the rewet of each single repletion subtracting the weight of the corresponding paper PI from the weight of the wet paper P2 and obtaining the rewet in grams. For each sample, the average rewet and the standard deviation are measured.

Test Method 2 - "Run-off test"

For this test, an ED ANA standard method (NWSP 080.9.R0 (15)) is used. The "Run-off test" measures the quantity of test liquid that runs down a nonwoven sample, when the specified mass of the test liquid is poured onto the nonwoven sample superimposed on a standard absorbent media and placed on an inclined plane. The test is particularly suitable to evaluate the capacity of a topsheet to interact with the test liquid. The principle of the test consists of pouring a specific quantity of artificial urine at a predetermined speed onto a nonwoven sample that is superimposed on a standard absorbent media and placed on an inclined plane. Any portion of liquid in excess that flows along the sample is collected by a standard receiver positioned under the lower end of the nonwoven sample. The run-off test measures the mass of the liquid collected in the standard receiver. A high run-off value is an indication of low liquid retention capacity of the topsheet. The equipment required consists of an analytical balance capable of measuring 30 grams with an accuracy of 0.001 grams, an inclined plane as shown in Figs. 5 and 6, stopwatch, artificial urine (formed of 0.9 % by weight sodium chloride solution), absorbent paper for standard absorbent media consisting of a sheet of 140 mm x 275 mm grade 989 by the company Ahlstrom. These sheets of paper are positioned with the absorbent part facing upward (in contact with the test piece to be tested). Absorbent paper for standard receiver consisting of two layers of absorbent paper 35 mm x 175 mm grade 989 by the company Ahlstrom. These sheets of absorbent paper are positioned with the absorbent part facing upward (to receive any excess test liquid).

To carry out the test, a sheet of absorbent paper is placed under the nonwoven rectangle to be tested. The nonwoven must be 5 mm longer with respect to the absorbent paper. Place the two superimposed layers on the inclined plane, the two rectangles must be positioned with the longer side along the plane. The layer with nonwoven must remain facing upward. Fix the test piece obtained to the inclined plane with the clamp leaving the lower base, the side from which the liquid must presumably percolate, free. Weigh the standard receiver with a precision of 0.01 grams (P0) and position it in the receptacle placed at the bottom of the inclined plane. Start wetting with the test liquid pouring 25 ml from a distance of around 25 mm from the nonwoven to be tested in a time of 4 seconds. Wait 5 seconds until the liquid has completed distribution and weigh the standard receiver (PI) again. Ensure run-off has been completed before weighing the standard receiver. Repeat the measurement 5 times for each sample. For each sample analyzed the run-off value is determined both in grams and in percentage of the liquid retained by the standard receiver. The run-off value for each sample expressed in grams (RFn) will be:

RFn = Pl - P0 while the run-off percentage for each sample (RFn%) will be: RFn% = RFn . 100 / P0

For each product, the values are expressed as average and standard deviation of the 5 tests.

Test Method 3 - Measuring the production parameters of the impressions

The object of the method is determining on a nonwoven with impressions: a) number of impressions per square centimeter and b) the average area of the impressions expressed in square millimeters.

The measurements in question are determined electronically with the aid of a camera calibrated so as to distinguish areas with different color grades. In particular, the material in question is placed on top of a media of a different color from that of the sample (e.g. white sample, black media), the camera is set to recognize the free areas, i.e. the areas of the same color as the media. The computer connected to the camera processes the pixel number data associated with each free area.

The equipment consists of a "Flexi-lab" camera connected to a computer with data processing system. Electronic System Supplier. Balance with accuracy of 0.1 % of the weight of the sample being tested.

The process consists of taking a minimum of three samples for each product type. The grammage is determined on each sample to be tested. The samples are positioned on the media of the instrument with the using side (side in contact with the skin) facing upward. Three different positions are selected, at each of the two ends and in the center of the sample, and the electronic measurements are taken on each. The computer processes the pixel data transforming them into the corresponding number and area values of the impressions.

Based on the values supplied for each single sample the average number of holes per square centimeter and average area of the holes, expressed in square millimeters, is determined.

Test Method 4 - Measuring the hydrophilia of the fibers (sinking time)

The object of the method is to determine the hydrophilic or hydrophobic properties of the fibers used to produce the nonwoven. The method derives from adaption to staple fibers of the standardized method for nonwovens (EDANA test 10.4-02 or NWSP 010.1.R0 (15)). The test consists of measuring the sinking time of a sample of fiber in demineralized water. In the test, around 5.0 grams of fiber is collected and opened by means of a manual carding machine until it has the appearance of wadding. The sample is inserted into a metal cylinder open on one side, height 80 + 1 mm, diameter 50 + 1 mm and weight 3 + 0.1 g. The cylinder must have mesh with an area of around 20 square millimeters. The mesh is welded so as to maintain the structure stable. The welds must be evenly distributed on the cylinder to ensure equal weight distribution.

Subsequently, the sample is placed on the surface of the liquid (demineralized water) contained in a transparent beaker, if possible glass, with a minimum capacity of 1000 ml. The beaker must have an aperture that enables the basket to be accommodated along the height (80 mm) without contact with the walls (diameter of the beaker > 90 mm).

Using a stopwatch with sensitivity of at least 0.1 s, the sinking time of the cylinder containing the fiber below the level of the water is measured.

With reference to the classification of hydrophilia in this application, hydrophilic fibers are considered as those that give rise to sinking times in the order of a few seconds, while hydrophobic fibers are those that exhibit times of over 5 minutes.

Moreover, fibers that exhibit hydrophilic properties even after being washed or in contact with water (and subsequently dried) are classified as "repeatable" or "durable" hydrophilic fibers.

Test Method 5 - EDANA thickness test (EDANA Method 30.5-99)

The thickness of the materials is measured in accordance with the harmonized test EDANA 30.5-99 using a KARL SCHRODER KG thickness gage equipped with a model S229 Sylvac dial gage. The values are expressed in millimeters (mm).

With reference to the thickness of the bottom of the impressions, due to their limited surface, the method in question is not applicable. In these cases, the thickness is determined via optical microscopy or SEM on sections of the material.

Test Method 6 -EDANA test for grammage or basis weight (EDANA Method

40.3.90)

The grammage is measured in accordance with the harmonized test EDANA 40.3-90 through the use of a Mettler Toledo Model ML303/01 balance. The values are expressed in grams per square meter (gsm).

Examples

Example 1 A material representative of the present invention can be produced using for the upper layer 14 a carding machine CI supplied with bicomponent fibers consisting of polyester (PET, inner part or core) and polyethylene (PE, outer part or sheath) so that the polyethylene outer part with a lower melting point melts in the oven giving rise to bonding points between the fibers. The fibers have a denier of 2.2 DTex and length of 38 mm. The fibers are treated on the surface (finished) with hydrophobic agents (or alternatively untreated, retaining the hydrophobic nature of the polymer). The upper layer is produced with a grammage of 28 gsm. A carding machine C2 supplied with a blend consisting of 40% bicomponent polyester and polyethylene fibers (denier 2.2 dtex and length 38 mm) and of 60% bicomponent polypropylene and polyethylene fibers (denier 6.7 dtex and length 40 mm) is used for the lower layer 15. Unlike the fibers of the upper layer, all the fibers of the lower layer are treated with a mixture of surfactants (finishing agent) suitable to impart a hydrophilic nature to the fibers even after being repeatedly wet with fluid. The lower layer is produced with a grammage of 32 gsm. The upper and lower layers are simultaneously processed on the same conveyor belt and sent to a hot air oven F to be thermally bonded together. At the end of the process the nonwoven formed by the layers 14 and 15 is sent to a heat calender where, by means of the process for producing the impressions, the material described in Fig. 2 is produced. The test carried out in accordance with the Test Method 3 "Measuring the production parameters of the impressions" provides the following results (average values): average area of impressions 0.8 square millimeters, number of impressions per square centimeter 10.04.

The test carried out in accordance with the Test Method 5 "EDANA thickness test" provides a material thickness, corresponding to the parameter s, of 1.35 mm. Example 2

A second material representative of the present invention is produced to carry out comparative tests with the material of Example 1. It too is comparable in structure to the material shown in Fig. 2. In the preparation two separate nonwovens are produced, both by means of a process of carding and thermally bonding bicomponent fibers. They are bonded separately and sent the calendar separated.

The nonwoven relating to the first layer 14 consists of bicomponent polyester (PET, inner part or core) and polyethylene (PE, outer part or sheath) fibers with denier of 2.2 DTex and length of 38 mm and hydrophobic finish (or alternatively untreated, retaining the hydrophobic nature of the polymer). The NW 14 is produced with a grammage of 28 gsm.

The NW 15 (relating to the second layer 15) is prepared with a mixture consisting of 40% bicomponent polyester and polyethylene fibers (denier 2.2 dtex and length 38 mm) and of 60% bicomponent polypropylene and polyethylene fibers (denier 6.7 dtex and length 40 mm). All the fibers of the lower layer are treated with a hydrophilic finish. The NW 15 is produced with a grammage of 32 gsm.

The two NWs 14 and 15 are then sent, as said, to a heat calender where by means of a process of impression with a pattern analogous to Example 1 (engraving and open area of the pattern) they are joined, maintaining the first layer 14 as upper layer and the second layer 15 as lower layer.

Example 3

A material not representative of the present invention is produced to carry out comparative tests in the same way as Example 1, with the exception that at the end of bonding in the hot air oven, the nonwoven is not subjected to the action of the heat calender, and therefore the material has no impressions or holes.

Example 4

A material not representative of the present invention is produced to carry out comparative tests in the same way as Example 1, with the exception that fibers with analogous hydrophilic properties to those of the lower layer 15, in particular PET/PE fiber with repeated hydrophilic finish, are used for the upper layer 14. At the end of the process the nonwoven formed by the layers 14 and 15 is sent to a heat calender where a process for producing impressions with a pattern analogous to Example 1 (engraving and open area of the pattern) is carried out. The test carried out in accordance with Test Method 3 "Measurement of the production parameters of the impressions" provides the following results (average values): average area of the impressions 0.79 square millimeters, number of impressions per square centimeter 10.10.

Example 5

A material not representative of the present invention is produced to carry out comparative tests with the materials of Examples 1 and 2. The material has a grammage of 28 gsm, is produced with fibers treated on the surface (finished) with hydrophobic agents (or alternatively untreated, retaining the hydrophobic nature of the polymer) and is subjected to complete perforation by means of a heat calender with the same pattern as Examples 1 and 2. In practice this is a completely perforated hydrophobic Air-Through-Bonded NW.

Example 6

A material not representative of the present invention is produced to carry out comparative tests with the materials of Examples 1 and 2. In the preparation two separate layers are produced (materials A and B), both by means of a process of carding and thermally bonding bicomponent fibers as indicated in Example 2. The material A has a grammage of 28 gsm, is produced with fibers treated on the surface (finished) with hydrophobic agents (or alternatively untreated, retaining the hydrophobic nature of the polymer) and is subjected to complete perforation using a heated calender with the same pattern as Examples 1 and 2. The material B instead has a grammage of 32 gsm, is produced with fibers treated on the surface (finished) with hydrophilic agents and is not perforated. The two materials are then joined (perforated upper layer and unperforated lower layer) by means of passage through a heated calender on smooth rollers or with ultrasound. This end material no longer has open holes and has a structure conforming to the pattern of Fig. 1. However, the material does not have areas in which the fibers of the two layers are efficiently mixed (such as in Examples 1 and 2).

Example 7

A material representative of the present invention can be produced using for the upper layer 14 a carding machine supplied with bicomponent fibers consisting of polyester (PET, inner part or core) and polyethylene (PE, outer part or shell) so that the polyethylene outer part with a lower melting point melts in the oven giving rise to bonding points between the fibers. The fibers have a denier of 2.2 DTex and a length of 38 mm and are treated with hydrophobic finishing agents (or alternatively untreated, retaining the hydrophobic nature of the polymer). The upper layer 14 is produced with a grammage of 18 gsm. A carding machine supplied with bicomponent fibers consisting of the same polyester and polyethylene as the upper layer is used for the lower layer 15, with the difference that these fibers are treated with an agent (finished) capable of making the fibers hydrophilic, consisting of a mixture of surfactants capable of imparting a hydrophilic nature to the fibers even after being repeated wet with fluid. The lower layer is produced with a grammage of 20 gsm. The upper and lower layers are simultaneously processed on the same conveyor belt and sent to a hot air oven for thermal bonding. At the end of the process the nonwoven formed by the layers 14 and 15 is sent to a heat calender with an embossing profile that allows the material described in the photograph of Fig. 4 and in Fig. 6 to be obtained. In this case, the impressions have an experimentally determined surface of around 0.8 mm 2 (small) and 5.0 mm 2 (large), with an impression area of 10.01 %.

The test carried out in accordance with Test Method 5 "EDANA thickness Test" provides a thickness of the material, corresponding to the parameter s, of 1.02 mm.

Example 8

Absorbent articles used for the comparative tests between the materials are produced by inserting the materials of Examples 1, 2, 3, 5 and 6 in a commercially available structure, substituting the original topsheet and ADL with them. The structure used is the "Coop" Ultra Sottile (Ultra Thin) sanitary pad. It has been experimentally determined that this article contains:

a topsheet consisting of a perforated polyolefin film of 20 gsm joined to a spunbond polypropylene of 12 gsm;

an Acquisition and Distribution Layer (ADL) in airlaid material of 70 gsm; a core consists of fluff and superabsorbent polymer (SAP) with a total grammage of around 300 gsm.

The absorbent products assembled in the manner described above and having as topsheets and ADL the materials prepared as indicated in Examples 1, 2, 3, 4 and 6 are tested with Test Method 1 to evaluate and compare to one another and to the original commercial structure the acquisition times and the rewet.

The results are set down in Table 1 :

Example 2

Material claimed (second 95 6 1 .7 0.2 embodiment)

Example 3

n.a.(l): not experimentally measurable as the fluid

(material without impressions or

tends not to penetrate the product spontaneously. actual holes)

Example 4

(material with impressions, but 60 9 2.3 0.2 with two hydrophilic layers)

Example 6

(material without impressions, but

55 7 1 .6 0.2 with actual holes on the

hydrophobic layer)

Coop Ultra Sottile

1 1 2 20 1 .2 0.4 (commercial structure)

From the data in Table 1 it can clearly be observed that the material of the present invention (Example 1) is able to decrease the rewet value considerably compared to the analogous hydrophilic material with impressions (Example 4), maintaining acquisition times suitable for use in the hygiene sector. In fact, the material of Example 1 is surprisingly marked by faster acquisition times than the analogous hydrophilic material with impressions (Example 4). Moreover, it has been found that the material of the present invention, in particular produced according to the method of the Example 1, having impressions in which mixed mode mechanisms are established, is marked by acquisition times that are even faster than the material of Example 6, operating with the same rewet. Therefore, the presence of impressions in which the properties of the two layers of which it consists interact intimately (structure of Fig. 2) offers surprising advantages with respect to simple joining of a perforated layer and a flat layer (structure of Fig. 1, conceptually attributable to the description provided in the patent EP 0235309 B 1 , cited as prior art).

On the contrary, as expected, a material having the surface of the topsheet completely hydrophobic and without impressions or holes, which could have improved rewet values, has unacceptable values of fluid acquisition time.

Moreover, the material of the present invention is capable of taking the rewet values to reference levels of the perforated film used in the commercial structure selected, which is the material chosen in the hygiene sector to reduce this phenomenon. Further, with the same rewet value, the considerable decrease in acquisition times exhibited by the material of the present invention with respect to the perforated film contributes to reducing the feeling of wetness in the user.

Especially important among the results achieved by the materials in question is the ability to obtain similar rewet and improved acquisition speeds with respect to the perforated film topsheet, simultaneously providing the softness and fabric handle typical of nonwovens.

Run-off

The materials of Examples 1, 2, 3, 4, 5 and 6 are tested with Test Method 2 to determine run-off. Five repetitions are carried out for each test, at the end of which the averages and the standard deviations are calculated.

The results are indicated in Table 2 Table 2

Run-off (g) Run-off (%)

Average Std. dev. Average Std. dev.

Example 1

Material claimed 2.6 0.6 10.3 2.6

Example 2

Material with first layer 8,4 2.4 33.6 9.4 completely perforated

Example 3

n.a. (2): all the fluid tends to run off the surface of the material into

(material without impressions

the receptacle of the receiver (run-off 25.0 g, i.e. 100%)

or actual holes)

Example 4

(material with impressions,

0.0 0.0 0.0 0.0 but with two hydrophilic

layers)

Example 5

(single layer hydrophobic 21 .0 1 .1 83.8 4.2 material with actual holes)

Example 6

(material without impressions,

8.1 1 .4 32.3 5.5 but with actual holes on the

hydrophobic layer)

From Table 2 it can be observed that a simple perforated hydrophobic material (Example 5) or double layer materials that have an unperforated upper hydrophobic layer (Example 3), have unacceptable run-off values, close to 100%. 5 Vice versa, a completely hydrophilic material (Example 4) has a very low run-off value (generally zero). The materials of Examples 1, 2 and 6 all exhibit run-off values suitable for use in the hygiene sector. However, it has been seen that, while the solution of Example 2 has almost the same run-off value as the solution produced according to Example 6 (which has no impressions), the solution produced according to Example 1 exhibits a considerably lower run-off (around 2.5 grams, i.e. 10%), more similar to that of a completely hydrophilic material. This is further proof of the improved performance of the impressions.

It is understood that the drawing only shows possible non-limiting embodiments of the invention, which can vary in forms and arrangements without however departing from the scope of the concept on which the invention is based.

Any reference numerals in the appended claims are provided purely to facilitate the reading thereof, in the light of the above description and accompanying drawings, and do not in any way limit the scope of protection.