WO2009062998A1

WO2009062998A1 - Perforated and treated material

Info

Publication number: WO2009062998A1
Application number: PCT/EP2008/065455
Authority: WO
Inventors: Fabio Di Berardino; Xavier Conillera Trillas; Robert Garcia Pano
Original assignee: Tesalca-99, S.A.; Texol, S.R.L.
Priority date: 2007-11-13
Filing date: 2008-11-13
Publication date: 2009-05-22

Abstract

The present invention discloses a perforated material, and a process for its manufacturing, in which the material adjacent to the holes and forming their walls is treated with a surfactant to create a surface tension gradient in the holes. Said perforated material can be incorporated in absorbent hygienic products, such as baby diapers, adult incontinence diapers and women's personal hygiene products.

Description

PERFORATED AND TREATED MATERIAL

FIELD OF THE INVENTION

The object of this invention is to develop perforated materials that can be incorporated in absorbent hygienic products (such as baby diapers, adult incontinence diapers and women's personal hygiene products) with improved properties with respect to existing perforated materials regarding their hygienic properties (dryness, transfer time, rewet and/or runoff) and softness.

Also the object of this patent is the method used to manufacture these perforated materials and for deep embossing.

Another object of the patent is the incorporation of these materials in hygienic absorbent products, such as baby diapers, adult incontinence diapers and women's personal hygiene products.

BACKGROUND OF THE INVENTION

There are many existing perforated products and methods for manufacture thereof. Some examples are described in the following patents:

US Patent 4,886,632 describes a method for perforating a non-woven fabric web and the use of these webs as topsheet in feminine hygiene products. This invention foresees the incorporation of heated pins that penetrate the non-woven fabric web to make the corresponding holes, their heat melting the edges of the holes.

US Patent 6,849,319 relates to an absorbing item formed by a backsheet structure, an absorbent core and a topsheet in contact with the user's body, wherein the topsheet is multi-perforated, the topsheet being a simple non-woven fabric that separates the absorbent core from the user's body.

Patent EP 235,309 describes a perforated product that combines hydrophilic and hydrophobic properties to try to improve liquid transfer performance.

US Patent 7,005,558 describes a perforated fibrous material in which the edge of the holes is impermeable to liquids as the material in this area has been fused to create this impermeable barrier. This type of solution can present softness problems when used as a topsheet, as the fused areas are hardened and represent a significant loss of softness.

Patent EP 214,608 describes a material perforated by hot pins, in which the fibres are densified in the areas of the holes, thereby avoiding the softness problems suffered by the previously cited patent. However, there remains the risk of liquid being trapped in the fibres when these are hydrophilic, particularly in the densified area around the holes; there is also a risk of the liquid being distributed in a horizontal sense due to the interfibre capillaries present in the hydrophilic non- woven fabric.

Moreover, the methods and technologies used to manufacture this type of perforated materials are diverse and comprise the use of hot pins (as described in

US Patent 4,886,632), water at a high pressure (as described in US Patent 5,414,914), cutting calenders combined by stretching the fabric (as described in US Patent 5,916,661 ), calenders that work at different speeds (as described in US Patent 5,414,914). These developments show the need to improve the performance of perforated products. The invention of this patent intends to solve the softness and liquid retention problems described, proposing the use of a hydrophobic material with properties very similar to those of a hydrophilic material, as well as hygiene products incorporating it and the method for manufacturing it.

DESCRIPTION OF THE INVENTION

The present invention consists of a perforated material in which the material adjacent to the holes and forming their walls is treated with a surfactant to create a surface tension gradient in the holes.

This material can be a non-woven fabric, a film or a laminate combining a film and a non-woven fabric.

The non-woven fabric can be a carding, a spunbond, a combination of spunbond and meltblown, airlaid or any other type of non-woven fabric. The use of additives to convert a hydrophobic material into a hydrophilic one is known by the expert on the subject. A known way of obtaining textiles that have hydrophilic properties instead of hydrophobic ones is by treatments with surfactants. Suitable conventional additives include, ionic surfactants, cationic surfactants, amphoteric surfactants or mixtures of the same which are commercially available, for example: Cirrasol PP682 marketed by Uniqema, Stantex S 6327 marketed by Cognis, Silastol PST marketed by Schill & Seilacher, Silwet L-7608 marketed by Momentive Performance Materials.

Other additives to convert hydrophobic material into hydrophilic are the melt additives, commonly used for example in films. The commercial melt additives used are for example 100410 AF PE MB marketed by Ampacet, lrgasuf HL560 marketed by Ciba Speciality Chemicals Inc., Hydrosorb 1001 marketed by Goulston Technologies Inc.

The invention relates to a material that can be a non-woven fabric, a film or the combination thereof (hereinafter referred to as a "laminate"). The non-woven fabric comprises a perforated substrate of fibres that can be continuous, such as for example (without being limited to) spunbond or SMS (spunbond-meltblown- spunbond), or discontinuous, such as carding or airlaid.

The fibres can have a circular cross-section or other shapes including multilobal, trilobal, delta, hollow, etc. In addition, they can be monocomponent

(made from a single material, such as polypropylene, polyethylene, polyester,

PLA...), bicomponent (e.g. combination of polypropylene and polyethylene) or multicomponent.

The film can be made of polypropylene, polyethylene, or a combination thereof, including other polymers such as polyester and biopolymers.

The present invention proposes the use of perforated hydrophobic materials in which the surface of the fibres forming the walls of the holes is selectively treated with surfactant.

The hydrophilic fibres may comprise (see Figure 1 ) the total wall of the holes, (from the top to the bottom) (a), or only a partial area, that means the bottom (b), a central area (c) or the top area (d).

The holes are not limited to circular, nearly circular or oval shape. The object of the invention is also valid for any other hole shape.

The limitation is defined by the formula X > Y + Z, where X: The distance between the centre of two contiguous holes.

Y: The shortest distance, when this distance is a straight line passing through the centre of the hole in a perpendicular plane to the axis of the hole, which separates two points comprising hydrophilic fibres arranged around the same hole. Z: The greatest distance, when this distance is a straight line passing through the centre of the hole in a perpendicular plane to the axis of the hole, which separates two points comprising hydrophilic fibres arranged around the same hole.

In the case that the perforated material includes the use of a hydrophobic non- woven fabric, the creation of the surface tension gradient in the holes proposed by this invention is particularly advantageous, as it aids the passage of liquid through the holes, preventing diffusion by capillary action towards the rest of the fabric as the latter is hydrophobic.

The use of hydrophobic material will give a further advantage in terms of dryness compared to the hydrophilic ones. This further advantage could be shown by measuring the Transepidermal Water loss (TEWL). The TEWL measurement is a common method used to determine skin hydratation in hygiene products as can be seen in patents such as US Patent 6,107,537 or US 7,037,1 12.

In this way the channels are made impermeable to liquid passage into the non-woven fabric, without having to fuse the fibres adjacent to the hole as proposed in US Patent 7,005,558, thereby improving the softness of the product obtained.

Also the object of the invention is a material such as those described above wherein instead of being perforated the material has a deep embossing and is manufactured according to any of the procedures described in the state of the art, with the characteristic that the deep areas simulating holes are treated with a surfactant to aid a selective passage of liquids.

The object of the invention as stated throughout the description is appropriate for manufacturing hygienic items such as baby diapers, adult incontinence diapers, feminine hygiene products such as pads or any similar absorbent product. The material can be used as a liquid capture layer under a topsheet, as topsheet, or as a joint topsheet and liquid capture layer. A preferred method for the production of the perforated materials of the invention comprising the following steps:

• Introducing a material sheet through a perforating nip (5) formed by a drum (4) carrying perforating pins and a female roll (3), while the perforating pins applied on the drum pass through a surfactant applicator (6) before becoming in contact with the material sheet.

• The perforated material sheet remains in contact with the pins of the drum roll up to a phase of separation from the pins due to the action of a vacuum roll (7); in addition said vacuum roll enables the removal of the excess amount of surfactant applied by the perforating pins.

• The perforated material sheet (8) is then driven onto a cooling unit (9) which provides surfactant fixing onto the walls of the holes of the perforations; said cooling unit also provides the stabilization of the pattern of the holes so- obtained

By coating the pins with a low surface tension additive (like for example fluorocarbons) the surfactant can be applied only to the bottom area of the walls of the holes of the perforated material, to the central area of the walls or to the top of the walls.

Examples:

Experiments were performed using the test methods WSP (Worldwide Strategic Partners) published by EDANA (European Disposables And Nonwovens Association) and !NDA (Association of the Nonwovens Fabrics Industry) with minor adaptations described below, which as can be seen in the examples allow us to demonstrate the advantages provided by this invention with respect to the existing materials in the state of the art:

(1 ) Strike through time: Norm WSP 70.7(05) has been followed. The original Norm uses 5 filters. In our case 2 and 5 filters were used.

By reducing the number of the filters and keeping the liquid the same we approximate conditions nearer to the saturation point of the filters and thereby increase the analyses of their performance properties. The absorption capacity of the absorbent core is a critical parameter in hygiene products.

(2) Rewet: Norm WSP 80.10(05) was used.

(3) Run-off: Norm WSP 80.9 was used.

(4) Denier is a usual measure used in the non-woven fabric sector to size the diameter of fibres. It is defined as the weight in grams of 9.000 meters of fibre.

Example 1) Non-woven fabric spunbond of polypropylene with basis weight 20 gsm (gsm means "grams per square meter"), fibres with a circular cross section with diameter 1 ,9 denier, perforated with 1 1 holes/cm², hole size 1 ,2 mm², open surface of 13%, three-dimensional holes and 0,45 mm material thickness.

This material has been subjected to three different finishes: i) Hydrophobic finish: No surface treatment was applied to the spunbond non-woven fabric. Thus, given the hydrophobic nature of polypropylene, the spunbond is hydrophobic. ii) Hvdrophilic finish: A surface treatment was applied before perforating with a surfactant commonly used in the hygiene sector. The surfactant used was Silastol-PST, manufactured by the German company Schill & Seilacher, in a concentration by weight of perforated product of 0,6%. iii) Hvdrophilic holes finish: This is the finish object of the present invention. Starting from a hydrophobic material (without treatment, such as that described in point "i" above), the holes were hydrophilised using the impregnated roller method explained in this invention. The hydrophilising agent used was the surfactant Silastol- PST manufactured by Schill & Seilacher, in a concentration by weight of perforated product of 0,3%. The following table shows the results of the hygienic tests (strike through time, rewet and run-off):

Strike through

Rewet

Material time (s) Run-off

(5 filters) (g) (OL

Hydrophobic 5,6 0,12 53

Hydrophilic 3,1 0,14 1

Hydrophilic holes 3,7 0,15 0,4

The table shows that the hydrophobic material presents a slightly lower rewet value but has higher run-off and strike through time values, which renders its use in a hygienic product inadvisable.

The material described in the present invention would allow the use of a hydrophobic material with a performance combining the strike through time and runoff value of a hydrophilic material with a satisfactory rewet value.

Example 2) Laminated material with total basis weight 40 gsm made by a layer of polyethylene film (20 gsm) and polypropylene spunbond (20 gsm), perforated with 1 1 holes/cm², hole size 1 ,9 mm², open surface of 21 %, with three-dimensional holes and 0,92 mm material thickness. The polyethylene film has been extruded with a mixture of hydrophilic additive, (as is well known in the state of the art), while the spunbond is untreated and is thus hydrophobic. The hydrophilic additive used was 100410 AF PE MB marketed by Ampacet at 2,5%. Lamination was performed by the coextrusion process (extrusion of the film on the non-woven fabric) and no glue was used to join the materials.

The following table shows the results of the Strike through time test with a different number of filters, as well as run-off and rewet values:

Test method: RUN-OFF (WSP 80.9)

Data unit: %

Result

12

Test method: REWET (WSP 80.10(05)) Data unit: Grams

Result

0,062

The same material was treated according to the present invention, hydrophilising the holes with the impregnated roller method described in the present invention. The hydrophilising agent used was the surfactant Silastol-PST manufactured by Schill & Seilacher in a concentration by weight of laminated product of 0,4%. The following table shows the results, revealing a very significant improvement in terms of strike through and run-off while keeping low rewet values.

Test method: STRIKE THROUGH (WSP 70.7(05)) Data unit: Seconds

Number of filters Result

2 1 ,9 5 2,1

Test method: RUN-OFF (WSP 80.9)

Data unit: %

Result

0

Test method: REWET (WSP 80.10(05)) Data unit: Grams

Result

0,148

Example 3) Laminated material with total basis weight 25 gsm formed by a layer of polyethylene film (13 gsm) and polypropylene spunbond (12 gsm), perforated with 1 1 holes/cm², hole size 1 ,6 mm², open surface of 18%, three-dimensional holes and 0,63 mm material thickness. Both the polyethylene film and the polypropylene spunbond are hydrophobic, as they have not been treated. Lamination was performed by the coextrusion method (extrusion of the film on the non-woven fabric) without using glues to join the materials.

Test method: STRIKE THROUGH (WSP 70.7(05)) Data unit: Seconds

Number of filters Result

2 2,4 5 1 ,8

Test method: RUN-OFF (WSP 80.9)

Data unit: %

Result

16

Test method: REWET (WSP 80.10(05)) Data unit: Grams

Result

0,022

The same material was treated according to the present invention, hydrophilising the holes with the impregnated roller method described in the present invention. The hydrophilising agent used was the surfactant Silastol-PST manufactured by Schill & Seilacher in a concentration by weight of laminated product of 0,26%.

Test method: STRIKE THROUGH (WSP 70.7(05)) Data unit: Seconds

Number of filters Result

2 1 ,8 5 1 ,4

Test method: RUN-OFF (WSP 80.9)

Data unit: %

Result

1 ,2

These values reveal a significant improvement in terms of strike-through and run-off while keeping similar rewet values.

This data demonstrates that the present invention provides a hydrophobic material suitable for use as a topsheet in absorbent products with considerable advantages mainly in terms of dryness while keeping good strike through time, run-off and rewet values.

Claims

1 .- Hydrophobic perforated substrate characterised in that the walls of the holes are hydrophilic.

2.- Hydrophobic perforated substrate according to claim 1 characterised in that the substrate is a non-woven fabric.

3.- Hydrophobic perforated substrate according to claim 1 characterised in that the substrate is a film.

4.- Hydrophobic perforated substrate according to claim 2 characterised in that the fibres of the walls of the holes are hydrophilic.

5.- Hydrophobic perforated substrate according to claim 2, characterised in that the non-woven fabric is spunbond.

6.- Hydrophobic perforated substrate according to claim 2, characterised in that the non-woven fabric includes a meltblown layer.

7.- Hydrophobic perforated substrate according to claim 2, characterised in that the non-woven fabric is carding.

8.- Hydrophobic perforated substrate according to claim 3 characterised in that the walls of the holes are hydrophilic.

9.- Laminate perforated comprising a hydrophobic film and a hydrophobic non- woven fabric characterised in that the walls of the holes are hydrophilic.

10.- Laminate according to claim 9, characterised in that the non-woven fabric is spunbond.

1 1.- Laminate according to claim 9, characterised in that the non-woven fabric comprises a meltblown layer.

12.- Laminate according to claim 9, characterised in that the non-woven fabric is carding.

13.- Laminate perforated comprising a hydrophilic film and a hydrophobic non- woven fabric characterised in that the fibres of the walls of the holes are hydrophilic.

14.- Laminate according to claim 13, characterised in that the non-woven fabric is spunbond.

15.- Laminate according to claim 13, characterised in that the non-woven fabric comprises a meltblown layer.

16.- Laminate according to claim 13, characterised in that the non-woven fabric is carding.

17.- Hydrophobic perforated substrate according to claims 1 to 8 characterised in that the holes are round shape.

18.- Hydrophobic perforated substrate according to claims 1 to 8 characterised in that the holes are polygonal shape.

19.- Hydrophobic perforated substrate according to claim 17 characterised in that such holes are circular shape.

20.- Hydrophobic perforated substrate according to claim 17 characterised in that such holes are oval shape.

21.- Laminate perforated substrate according to claims 9 to 16 characterised in that the holes are round shape.

22.- Laminate perforated substrate according to claims 9 to 16 characterised in that the holes are polygonal shape.

23.- Laminate perforated substrate according to claim 21 characterised in that such holes are circular shape.

24.- Laminate perforated substrate according to claim 21 characterised in that such holes are oval shape.

25.- Hydrophobic perforated substrate according to the claims 1 to 8 and 17 to 20 characterised in that the hydrophilic walls of the holes may comprise the total wall of the holes or only a partial area.

26.- Laminate perforated substrate according to the claims 9 to 16 and 21 to 24 characterised in that the hydrophilic walls of the holes may comprise the total wall of the holes or only a partial area.

27.- Hygienic product including a topsheet of a hydrophobic perforated substrate according to claims 1 to 26.

28.- Hygienic product according to claim 27 characterised in that it is a baby diaper.

29.- Hygienic product according to claim 27 characterised in that it is an adult incontinence diaper.

30.- Hygienic product according to claim 27 characterised in that it is a feminine hygiene item.

31.- A method for the production of material sheet perforated comprising in the following way: introducing a material sheet through a perforating nip (5) formed by a drum (4) carrying perforating pins and a female roll (3), while the perforating pins applied on the drum pass through a surfactant applicator (6) before becoming in contact with the material sheet.

32.- A method for the production of material sheet according to claim 31 , characterized in that the perforated material sheet remains in contact with the pins of the drum roll up to a phase of separation from the pins due to the action of a vacuum roll (7); in addition said vacuum roll enables the removal of the excess amount of surfactant applied by the perforating pins.

33.- A method for the production of material sheet according to the claim 31 or claim 32, characterized in that the roll (2) is pre-heated.

34.- A method for the production of material sheet according to the claim 31 , 32 or 33 characterized in that the perforated material sheet (8) is then driven onto a cooling unit (9) which provides surfactant fixing onto the walls of the holes of the perforations; said cooling unit also provides the stabilization of the pattern of the holes so-obtained.

35.- Process according to claim 31 , characterised in that the material is one of those described in claims 1 to 30.

36.- Process for the production of material sheet according to the claims 31 to 35, characterized in that the surfactant is applied on the pins of the male roller, which transfers it to the walls of the hole.

37.- Process according to claim 31 to 36, characterised in that the hydrophilic walls of the holes may comprise all the wall or only a partial area.