ITUB20153916A1 - ABSORBENT SANITARY ITEM INCLUDING A PERFORATED POLYMERIC MATERIAL - Google Patents

Description

DESCRIPTION

"ABSORBENT SANITARY ARTICLE INCLUDING A PERFORATED POLYMER MATERIAL"

TECHNICAL FIELD

The present invention relates to an absorbent sanitary article comprising a perforated polymeric material.

STATE OF THE ART

The development of absorbent sanitary articles and, in particular, of multilayer structures suitable for use in diapers or sanitary pads is the subject of intense commercial interest.

In the context of the present invention, an absorbent sanitary article means all absorbent products such as for example disposable absorbent articles, sanitary napkins, panty liners, interlabial devices, catamenial / medicinal / surgical tampons, diapers, incontinence products, towels, dressings, cups, sweat pads, underwear products, pants and shorts, cosmetic removal pads, mattress / bed / chair pads, pet pads and the like.

In the following, an absorbent sanitary article is understood to be any of the aforementioned products.

Originally the absorbent products were formed by composite materials formed by a plurality of layers containing fabrics or fibers generally of cotton which allowed to absorb the body fluids.

Subsequently the structures evolved by incorporating cellulose pulps which are able to absorb 5-6 times their weight. For example, it is now known to incorporate in the structures of sanitary articles and, in particular, diapers or feminine pads or for incontinence, absorbent gel materials such as polyacrylates in combination with cellulosic fibers and in this way it has been possible commercialize relatively thin multilayer structures.

A typical application is that of sanitary absorbent items such as baby diapers either as feminine or incontinence pads.

It is known for these purposes to use multilayer materials comprising a first layer in contact with the user's skin and generally referred to and hereafter as "topsheet" and generally made of non-woven fabric. Under the topsheet, a further layer is optionally arranged for the acquisition and distribution of the liquid, then a layer of absorbent material is arranged and finally a bottom layer which must be waterproof.

The topsheet must be crossed quickly by liquids, but at the same time it must act as a barrier and avoid the return of liquids from the absorbent layer towards the user's skin, in particular it must prevent the surface in contact with the skin from getting wet and maintain the sensation of dryness on the skin.

The passing function is more efficient the more permeable the material of which the topsheet is made.

Furthermore, it is often required that the topsheet be soft and soft to the touch as it is in contact with the user's skin and that it also provides a sense of so-called "cushioning" or cushion effect to the user. Furthermore, it would be desirable that the topsheet could have wet and dry resilience in all directions.

The thicker the layer of material the more difficult it is to permeate the liquid.

This problem was solved by perforating the topsheet to allow liquids to pass through the layer and quickly reach the liquid acquisition and distribution layer and the underlying absorbent material.

The perforation of the topsheet to accelerate the passage of liquids, however, takes place by squeezing the layer of material that forms the topsheet, causing it to lose thickness and therefore the topsheet will be less soft.

Attempts have been made to solve this problem by using topsheets made of special composite materials or by using different methods for drilling.

It is known today to perforate the layers of materials that make up the topsheet using different methods:

a first method is needle punching. In this method, the film or tape of material that will make up the topsheet is passed between two counter-rotating cylinders, the first of which is provided with needles arranged perpendicular to the surface of the cylinder and the second cylinder is provided with cavities in the surface complementary to the needles and suitable for housing the needles when the cylinders rotate.

A second type of perforation also called vacuum perforation occurs when a hot film or web of very thin material is rotated on a roll having a micro perforated and depressurized surface on the inside. Due to the pressure difference between the inside and outside of the roll, the film or tape is subject to micro perforations.

A third type of perforation is also called perforation by abrasion and is described for example in US patent 3408776.

A fourth type of perforation is obtained with a method described for example in the patent EP0596970 and consists of two rotating counter rollers, one smooth and the other provided with protuberances maintained in contact with each other and having different peripheral speeds, in particular the smooth roll has a slower speed than the protruding roll so that when the web of material passes over the nip between the two rolls, the protrusions dig holes in the web due to the differential speed.

Topsheets are generally made of non-woven fabric. The thickness of the layers of non-woven fabric depends on the technology with which they are produced. In any case, the increase in thickness is strictly linked to the increase in weight per square meter of the material, which also generally entails a considerable increase in costs.

For example, it is known to use very thick materials produced with the so-called "Air through bonded" technology or ATB for short. The fibers that make up the non-woven fabric tape are heat-sealed with a jet of hot air without contact with pressure cylinders, as is the case with the most common heat-sealed carded products, also known as "Carded thermal bonded".

Besides being very expensive, the ATBs do not provide a sufficient "cushioning" or "cushion" effect which would be ideal as a topsheet.

The most common non-woven fabrics used as topsheets, although cheap, are no longer considered sufficiently soft and soft to the touch and therefore users are looking for more pleasant alternatives to wear.

The need is therefore felt to have a material that can be used as a topsheet for absorbent sanitary articles, in particular for diapers for children, for incontinence or for feminine sanitary napkins capable of solving the aforementioned problems and which can also be produced at a lower cost.

SUMMARY OF THE INVENTION

The object of the invention is therefore to produce an absorbent article comprising a material which is at the same time soft, which is pleasant in contact with the skin, which allows a rapid passage of body fluids, but which at the same time remains dry and which is therefore usable as a topsheet or acquisition distribution layer of an absorbent sanitary article and which allows to have a resilience to dry and wet in all directions.

According to the present invention, the first object is achieved by an absorbent article according to claim 1.

DESCRIPTION OF THE INVENTION

Within the scope of the present invention, a layer is intended as a mass of homogeneous matter spread out more or less uniformly on a surface.

In the context of the present invention, monolayer material is intended as a material consisting of a single layer which can be subsequently joined by means of pressure or by means of chemical binders such as for example an adhesive or by heat sealing to other materials.

In the context of the present invention, expanded material or "foam" or "foamed" means a material transformed through a process of chemical or physical expansion.

In the context of the present invention, by closed cell foam material is meant a material consisting of "closed microcells", which make it impermeable to water, resilient, with good resistance to compression. Closed cell foam differs from open cell foam in that the cells are spaced apart and each completely surrounded by solid material. Conversely, in an open cell material there is a passage of fluid between one cell and another, which also makes the open cell material not fluid-tight. It should be noted that a closed cell material is hydrophobic and impermeable.

According to the present invention it is advantageous to use the material as a topsheet of an absorbent sanitary article, but the same material can also be used as an acquisition distribution layer.

In one aspect of the present invention the material is a closed cell expanded polymeric material.

The closed-cell expanded polymeric material preferably comprises a polyolefin, more preferably it comprises a material selected from the group consisting of polyethylene, polypropylene or mixtures thereof, even more preferably it comprises polyethylene.

Preferably it is in polyethylene, even more preferably in low density polyethylene.

Even more preferably, the closed cell foam is in the form of a film, tape or sheet.

Preferably, the foam material can be colored or white to differentiate its visual appearance.

Even more preferably, the closed cell foam material has a thickness comprised between 0.2 and 4 mm, more preferably between 0.6 and 3 mm, even more preferably between 0.8 and 2 mm.

Preferably, the closed cell foam material has a density between 5 and 60 Kg / m <3>, more preferably between 10 and 40 Kg / m <3>.

The characteristics of some closed cell polyethylene foam materials usable in the present invention are shown in Table 1.

Table 1

Unit Celi Aire Celi Aire Celi Aire 0,8 mm 1,0 mm 1,5 mm

Weight g / m <2> 13.9 17.7 19.5

base

Thickness Mm 0,83 1,3 1,55

Density Kg / m <3> 16.7 13.6 12.6

In a preferred aspect of the present invention, the expanded material is perforated twice before being coupled to other materials and is therefore hereinafter referred to as bi-perforated.

The perforated material comprises an upper face which in use will be directly in contact with the skin of a user if used as a topsheet or facing the skin if used as an acquisition distribution layer.

The double-holed material is preferably subjected to two distinct drilling steps.

During a first step, first holes or micro-holes are formed and during a second step second holes are formed.

Preferably the first holes formed during the first step are between 300 and 1000 in number per cm <2>, preferably with an average area of each hole less than 0.3 mm <2>, more preferably 0.1 mm <2>, more preferably less than 0.05 mm <2>.

Given their size, these holes can also be defined as micro-holes and in the following the first holes will be designated both as first holes and first micro-holes.

Preferably, the area occupied by the first holes is comprised between 8 and 20%.

The area occupied by the holes, also known as "open area" in English, is measured on the unassociated and unstretched free material.

The measurement of the area of the holes always takes place on the upper face of the film which in use will be in contact with the user's skin.

Preferably, the material is arranged with the cones formed by the first holes facing the user in use. This configuration is the one that provides the softness effect.

The formation of the first holes can preferably be obtained with a vacuum process or by calendering.

This last process is described for example in patent IT1360702,

According to this patent, the holes are preferably formed by means of a method comprising a step of passing the polymeric material between a first smooth cylinder and a second cylinder provided with cusps on the external surface suitable for realizing deformations extending from a first face of the polymeric material in this way allowing to obtain a polymeric material with a tactile sensation similar to fabric or silk or non-woven fabric. The first and second cylinders are pressurized against each other, the first cylinder provided with cusps is rotated at a peripheral speed greater than the peripheral speed of the second smooth cylinder with a consequent reciprocal sliding action between the surfaces of the cylinders. The number of cusps of the first cylinder is greater than 100 per cm2 of surface of the cylinder, preferably the cusps of the first cylinder are between 300 per cm2 and 1000 per cm2 of surface of the cylinder.

For example, in a first phase the linear pressure between the cylinders is respectively 90 N / mm and the percentage of sliding or friction is 50%. The temperature of the cylinder with the cusps can for example be 85 ° C and the temperature of the smooth cylinder 75 ° C. Table 2 shows some examples of polymeric materials obtained starting from cylinders having cusps having a truncated cone shape with an elliptical base.

Table 2

Cylinder 1 Cylinder 2 Cylinder 3 Number of holes (cm <2>) 430 223 531

% Area 21.9% 16.3% 27.1% surface

occupied by holes

Base area 0.051 0.073 0.051

of the hole

Basic shape of the elliptical elliptical elliptical hole

Dimensions 0.26 mm x 0.31 mm x 0.26 mm x 0.25 base diameters 0.25 mm 0.30 mm mm

cusp

Height 0.3mm 0.4mm 0.2mm

15 ° 20 ° 15 ° angle

flanks

Pitch in 0.89mm 1.24 0.81 direction of

machine

Pitch 0.52 mm 0.72 mm 0.47 mm transversal

In a second step, preferably but not necessarily temporally distinct from the first step, second holes are formed on the closed-cell expanded polymeric material.

Since the material is already drilled with the first holes, the new holes can correspond to the old holes in the foam material or they can be separated, but in any case they must be through.

Preferably the second holes occupy a surface comprised between 1 and 50% of the total surface.

The surface occupied by the holes or "open area" is calculated on the upper face which in use will be facing the user.

More preferably, the holes occupy a surface between 1 and 40%, even more preferably between 10 and 30%.

The average area of the individual holes is preferably comprised between 0.05 and 1 cm <2>, more preferably between 0.1 and 0.8 cm <2>.

The number of holes per cm <2> is preferably between 1 and 40 cm <2>, more preferably between 5 and 30 per cm <2>.

The material preferably has a combination of parameters among those reported above and in particular a surface occupied by the holes between 1 and 10% and an average area of the holes between 0.1 and 1 cm <2> and a number of holes per cm <2> between 5 and 25 or an area occupied by the holes between 1 and 10% and an average area of the holes between 0.05 and 0.3 was <2> and a number of holes between 15 and 25 or an area occupied by the holes between 10 and 20% and an average area of the holes between 0.1 and 1 cm <2> and a number of holes between 15 and 25 cm <2>.

The perforations can have different patterns and also be discontinuous and the discontinuities can be in CD or MD or be obtained with any of the methods described above. Preferred perforations are those described in patent EP0596970.

It is clear that further layers can be associated with the material of the present invention, such as for example a further layer of non-woven fabric below or above the closed cell foam material.

It should be emphasized that whatever the machining method for making the holes, it cannot ensure that all the holes are perfectly the same in shape and size and that there is always the same number of holes per unit of measurement and neither that the holes are extend evenly or homogeneously over the surface. However, it is known in the sector how to calculate both the surface occupied by the holes per unit of measurement, also known as "open area", and the number and dimensions of the individual holes always obtained as an average between different measurements, at least 3 measurements.

The material according to the present invention has proved to be particularly effective when used as a topsheet or as an acquisition distribution layer, also said layer suitable for the acquisition and distribution of the liquid in an absorbent sanitary article.

In particular, when it is used as a topsheet, a layer suitable for the acquisition and distribution of the liquid will preferably be arranged below the material, then a layer of absorbent material is arranged and finally a bottom layer which must be waterproof. It is clear that there are numerous variants of absorbent sanitary articles, for example it is possible that the layer suitable for the acquisition and distribution of the liquid and the absorbent layer are made up of a single material or vice versa it is possible that they are made up of 3 or more layers.

It is possible to arrange both below and above the layer of closed cell foam material of the present invention a layer of non-woven fabric to further increase the cushion effect or it is also possible not to use a layer for the distribution of the fluid.

From an examination of the characteristics of the material made according to the present invention, the advantages that it allows to be obtained are evident.

It has been experimentally verified that when the material of the present invention is used in an absorbent sanitary article and the through holes occupy an area between 5 and 40%, the body fluids quickly pass through the monolayer according to the present invention, but the user final does not feel any sensation of humidity thanks to the fact that without it being wet thanks to the hydrophobicity of the closed cell foam layer. In this way the product is externally drier after use and there is also a greater masking (non-visibility) of the fluids on the surface and therefore greater comfort for the user.Thanks to the presence of double holes it is possible to make the fluids flow quickly fluids without leaving a wet effect on the surface of the multilayer material which, in use, is in contact with the skin and without diminishing the effect of softness and three-dimensionality.

The material according to the present invention will be described hereinafter also by means of examples without for this reason that the invention is limited thereto.

EXAMPLE 1

A closed cell polyethylene foam layer 1 mm thick is formed. A material known as Cell-Aire was used. This material has an elongation at break of 8.5 mm, a resistance of 5.5 N to the punching test according to the SAC-PL 012 standard and with a longitudinal tensile strength of 10.9 N and a transversal tensile strength of 4 N according to the standard. DIN 53571 and an elongation at break length of 19.9% and transversal elongation of 34% according to DIN53571.

In a first phase, first holes are formed with a pattern for the perforations having the characteristics shown in table 3;

Table 3

Characteristics Test method Unit of measure Average batch Base weight WSP 130.1 g / meter2 10.35 Thickness WSP 120.6 Mm 0.30

MD Resistance ASTM D882 N / inch 5.04

traction

MD Elongation ASTM D882% 145.74

CD Resistance ASTM D882 N / inch 2.13

traction

CD Elongation ASTM D882% 415.07 '' Open Area "% 13.97

PIN-OUT

The closed cell polyethylene foam layer is perforated with needle technology with two perforation patterns with 11 points / cm2 and 18 points / cm2.

The data relating to the perforation of the two laminates at 11 or 18 pins or dots / cmq are shown in tables 4 and 5: Table 4

Percentage

Area

18 Area Number Average diameter of

pin occupied by Holes / cm <2> holes mm holes

holes

mean 5.69 0.32 17.73 0.64 Table 5

Percentage

Area

11 Area Number of holes Average diameter of holes

pin occupied by / cm <2> mm

holes

holes

average 7.29 0.72 10.13 0.96

Since the drilling method does not allow to ensure that there is always an exact quantity of holes in the unit of measurement, it is necessary to obtain the average which is the result provided in the table. The number and size of holes in a cm <2> can actually be double or half of the average.

EXAMPLE 2

A different perforation pattern is used to form the material to form the second holes, while the same pattern is used to make the first holes.

In particular, a so-called striped perforation pattern is used to make the second holes.

The material is perforated between two rollers under pressure on each other, of which a first roller has protrusions to perforate the material and a second roller rotates at a different speed from that of the first roller and has projections with contact areas arranged to pierce the material together with the protrusions. The contact areas of the projections are spaced by depressions to receive the processed material and have larger dimensions than the contact faces of the drilling protuberances. The perforation is carried out in correspondence of the contact areas that leave an imprint on the material. The contact areas are stretched and the length is at least four times the width to define a line or band. The line thus defined can be continuous or discontinuous in the MD direction. The major axis of the line can be both parallel and inclined with respect to the MD direction. The major axis of the line can follow a wavy path, preferably periodic.

Preferably, the cusps of a cylinder engraved with a pattern of approximately 80 points act in correspondence with the smooth part of the cylinder with channels. It turns out that a row of holes is formed no more than two of them in the CD direction.

Table 6 shows the characteristics of the holes for an example of row drilling obtained with the method described above.

Table 6

Percentage

Area

Holes Area Number of Holes Average diameter of

striped occupied by / cm <2> holes mm holes

holes

average 3.56 0.17 20.69 0.47 EXAMPLE 3

To form the material, a further different perforation pattern is used to form the second holes, while the same pattern is used as in example 1 to make the first holes.

In this case the perforation pattern allows to obtain elliptical holes in the direction of the sliding of the film during the hole formation phase.

Table 7 shows the characteristics of the holes.

Table 7

Percentage

Holes Area Average area Number of holes Wave diameter occupied by holes / cm <2> holes mm from holes

average 14.24 0.65 21.85 0.91 It should be noted that the holes in this case have an elliptical shape.

It is important to note that both the perforation pattern drawn as row perforation of table 6 and as wave perforation of table 7 is a continuous pattern in which the development on a cylinder will be helical.

Claims (13)

CLAIMS 1. Absorbent sanitary article comprising at least one layer of closed-cell expanded polymeric material having a lower face and an upper face, characterized in that said layer of closed-cell expanded polymeric material comprises a number of first micro-holes comprised between 300 per cm2 and 1000 per cm2 and second through holes in a number between 1 and 40 per cm2, said second holes having an average area calculated at the base between 0.05 and 0.5 cm2 and by the fact that said first micro-holes and said second holes occupy a surface comprised between 5 and 40% of the total surface of the upper face of said multilayer material. 2. Absorbent sanitary article according to claim 1, characterized in that said layer of closed-cell expanded polymeric material is made by means of a first drilling step able to form a number of first micro-holes between 300 per cm <2> and 1000 per cm <2> and a second drilling phase designed to form second through holes in a number between 1 and 40 per cm <2>, said second holes having an average area calculated at the base between 0.05 and 0, 5 cm <2> and from the fact that said first holes and said second holes occupy a surface comprised between 5 and 40% of the total surface of the upper face of said multilayer material. 3. Absorbent sanitary article according to claims 1 or 2, characterized in that said upper face of said layer of closed-cell expanded polymeric material is positioned towards the skin of a user and said lower face is positioned towards the inside of said article sanitary absorbent. 4. Absorbent sanitary article according to claims 1 to 3, characterized in that said upper face of said closed cell expanded polymeric material layer is positioned so that in use it is in contact with the skin of a user and said lower face is positioned towards the inside of said absorbent sanitary article. 5. Absorbent sanitary article according to any one of the preceding claims, characterized in that said second through holes occupy an area comprised between 5 and 30% of the total surface of the upper face of said multilayer material, 6. Absorbent sanitary article according to any one of the preceding claims, characterized in that the number of said second through holes is comprised between 5 and 30 per cm <2>. Absorbent sanitary article according to any one of the preceding claims, characterized in that; said second through holes occupy an area between 1 '1 and 10%, the average area of the holes is between 0.1 and 1 cm <2> and the number of holes per cm <2> is between 5 and 25, o - said second through holes occupy an area between 1 and 10%, the average area of the holes is between 0.05 and 0.3 cm <2> and the number of holes is between 15 and 25 for cm <2>, o said second through holes occupy an area between 10 and 20%, the average area of the holes is between 0.1 and 1 cm <2> and the number of holes is between 15 and 25 per cm <2> . 8. Absorbent sanitary article according to any one of the preceding claims, characterized in that said layer of closed-cell expanded polymeric material comprises a polyolefin. 9. Absorbent sanitary article according to any one of the preceding claims, characterized in that said layer of closed-cell expanded polymeric material is made of polyethylene. 10. Absorbent sanitary article according to any one of the preceding claims, characterized in that said layer of closed-cell expanded polymeric material has a density of between 5 and 40 kg / m <3>. 11. Absorbent sanitary article according to any one of the preceding claims, characterized in that said layer of closed-cell expanded polymeric material has a thickness of between 0.2 and 3 mm 12. Absorbent sanitary article according to any one of the preceding claims, characterized in that said first micro-holes have an average area of each micro-hole less than 0.3 mm <2>. 13, Method for making an absorbent sanitary article, said absorbent sanitary article comprising at least one layer of closed-cell expanded polymeric material having a lower face and an upper face, characterized in that said layer of closed-cell expanded polymeric material is made by a first drilling step designed to form a number of first micro-holes between 300 per cm <2> and 1000 per cm <2> and a second drilling step designed to form second through holes in a number between 1 and 40 for cm <2>, said second holes having an average area calculated at the base between 0.05 and 0.5 cm <2> and by the fact that said first holes and said second holes occupy an area between 5 and 40 % of the total surface of the upper face of said multilayer material.