WO2010104429A1

WO2010104429A1 - An absorbent article comprising an elastic laminate and a method for manufacturing thereof

Info

Publication number: WO2010104429A1
Application number: PCT/SE2009/050251
Authority: WO
Inventors: Inge Gabrielii; Mats Kinderdal; Elisabeth Lakso
Original assignee: Sca Hygiene Products Ab
Priority date: 2009-03-11
Filing date: 2009-03-11
Publication date: 2010-09-16

Abstract

In a personal care absorbent article comprising an elastic laminate said laminate comprises at least one elastic thermoplastic polymeric film laminated to at least one fibrous layer, wherein the fibrous layers are laminated to the film being in a stretched condition, so that the fibrous layers are gathered. The elastic film has a basis weight between 12 and 30 g/m², and the laminate has a tensile strength of at least 5N/25.4 mm, preferably at least 10N/25.4mm in the machine direction of the laminate. The invention further refers a method for producing the absorbent article said method comprising: providing said elastic film, heating and stretching the heated elastic film in at least one direction so that the elastic film during stretching has a temperature of at least 4O°C, wherein stretching is performed so as to extend the dimension of the film in the stretching direction between 100 and 500% of its original dimension, laminating said fibrous layer to the elastic film while this is in its stretched condition and subsequently incorporating the laminate in an absorbent article keeping the laminate either in a stretched or in a relaxed condition..

Description

An absorbent article comprising an elastic laminate and a method for manufacturing thereof

Technical field The present invention refers to a personal care absorbent article comprising an elastic laminate, said laminate comprises at least one elastic thermoplastic polymeric film laminated to at least one fibrous layer. The invention further refers a method for producing the absorbent article.

Background of the invention

Elastic nonwoven laminates are often used in disposable absorbent articles such as diapers, adult incontinence products, sanitary napkins and the like. Elastic films are difficult to handle and have undesirable tactile and strength properties. It is known to laminate nonwoven materials to elastic films. The nonwoven material strengthens the elastic film and provides a soft and non-tacky feel. The problem is that with attached nonwovens the nonwoven elastic film laminate has often little or no elastic properties. Numerous patents have addressed this problem. Many solutions are directed at ways to "activate" the elastic nonwoven laminate, which generally involves weakening the nonwoven in the direction of desired elasticity, generally by stretching. An elastic nonwoven laminate is formed and then placed under tension by a variety of techniques and stretched, see e.g., US patents 4,834,741 and 7,039,990. The stretching weakens the attached nonwoven allowing the underlying elastic to more freely stretch and recover.

Another proposed method to obtain cross-direction elastic properties, discussed in US patent 5,789,065, is by using nonwoven type fabrics that are necked prior to applying them to an elastic sheet. This means stretching of a nonwoven fabric or other fabrics prior to lamination to an elastic film or the like. Necking is the process of reducing the width of a nonwoven, or the like, by stretching the nonwoven lengthwise. Not all nonwovens are neckable so care needs to be made in selecting the nonwoven. The resulting necked nonwoven is subsequently easily stretched in the width or cross direction at least up to the original dimensions of the necked nonwoven.

US patent 6,476,978 discloses necking of a nonwoven web by continuously drawing the web through a web heating mean, wherein the web is subjected to tension to narrow its lateral dimensions and to increase its length. The web can be laminated to an elastomeric film.

WO 98/16380 discloses a cross-direction extensible elastic laminate produced by laminating at least one fibrous layer to at least one elastic layer and subsequently necking and heating the laminate.

US patent 5,789,065 discloses extrusion laminating a thermoplastic elastomeric film between two sheets of nonwoven using a closed nip, followed by necking the laminate while it is at an elevated temperature.

There is however still room for improvements with respect to elastic laminates having features that make them adapted for personal care articles with respect to comfort, strength and cost efficiency.

Object and most important features of the invention

One object of the present invention is to provide a personal care absorbent article comprising an elastic laminate comprising at least one elastic polymeric film laminated to at least one fibrous layer, said article having features like comfort and strength. This has according to the invention been provided by a personal care absorbent article comprising an elastic laminate, wherein the fibrous layers are laminated to the film being in a stretched condition, so that the fibrous layers are gathered, said elastic film having a basis weight between 12 and 30 g/m², and the laminate has a tensile strength of at least 5N/25.4mm, preferably at least 10N/25.4mm, more preferably at least 20N/25.4mm.

In one embodiment the elastic laminate is contained in any of the following components of the absorbent article: in elastic side tabs or ears, in belts or part of belts, in elastic side panels and/or in front and back body panels.

In a further embodiment the absorbent article is selected from the group consisting of: a diaper, a pant diaper, an adult incontinence article and a feminine hygiene article.

In a still further embodiment laminate has a basis weight between 40 and 180 g/m². A further object of the invention is to provide a process for manufacturing a personal care absorbent article comprising an elastic laminate In a special aspect of the invention the process should be adapted for in line lamination of an elastic laminate which is elastic in the machine direction and in a still further aspect to incorporate the laminate in an absorbent pant production line in which the pant articles are arranged side-by-side - so called cross production

A still further object is to provide a cost efficient method for producing absorbent articles comprising elastic chassis portions, such as body panels, side panels and the like, fulfilling demands of strength of the laminate as well as sufficient elasticity

The invention suggests a method for manufacturing a personal care absorbent article comprising an elastic laminate, said laminate comprising at least one elastic thermoplastic polymeric film laminated to at least one fibrous layer, said method comprising providing said elastic film, heating and stretching the heated elastic film in at least one direction so that the elastic film during stretching has a temperature of at least 4O⁰C, wherein stretching is performed so as to extend the dimension of the film in the stretching direction between 100 and 500% of its original dimension, laminating said fibrous layer to the elastic film while this is in its stretched condition and subsequently incorporating the laminate in an absorbent article keeping the laminate either in a stretched or in a relaxed condition

In one embodiment the laminate is produced in a process which is in-line with the incorporation of the laminate in the absorbent article

In a further embodiment the heated film is stretched to extend its dimension in the stretching direction between 200 and 500% of its original dimension

In one aspect of the invention the elastic film after relaxation of the laminate recovers not more than 80% of its elongation

In a further aspect of the invention the elastic film after relaxation of the laminate recovers at least 30% and preferably at least 50% of its elongation In a still further aspect the elastic film is stretched so as to have a basis weight after relaxation of between 12 and 30 g/m².

In one embodiment the film during stretching has a temperature of at least 45⁰C.

In a further embodiment the film during stretching has a temperature which is at least 10⁰C below the melting temperature or the glass transition temperature of the hard blocks of the polymeric material of said elastic film.

In a still further embodiment the lamination is achieved by a bonding process selected from adhesive, thermal and ultrasonic bonding.

In a further aspect of the invention the elastic film is stretched in two or more successive steps.

Description of drawings

Fig. 1 shows a perspective view of an absorbent article in the form of a pant diaper. Fig. 2 is a schematic view of an apparatus for making an elastic laminate according to the invention. Fig. 3 is a schematic representation of a method for producing a pant-type absorbent article comprising the elastic laminate.

Fig. 4 is a graph showing the inflection point in stretch-strain curve vs. temperature of the elastic laminate when the elastic film has been heated to different temperatures.

Definitions

Amount of "stretching" of a material as used herein is defined as a percentage of the initial non-stretched extension of the material in the direction of stretch. By way of example a laminate having a first non-stretched length of 1 m and being stretched by 50% has a stretched length of 1.5 m.

The term "elastic" as used herein defines a material having a permanent elongation after relaxation of less than 10% after the material has been subjected to an elongation of 30% in the Elasticity test described. An elongation of 30% means an elongation to a length 30% longer than the initial length of the sample. The term "fibrous layer" refers to a web material in the form of a sheet of fibres, continuous filaments, or chopped yams of any nature or origin, that have been formed into a layer by any means. Examples of fibrous layers are nonwoven materials in which the fibers or continuous filaments are bonded together by any means, with the exception of weaving or knitting, to form a web. Other examples of fibrous layers that may be used are knits or loosely woven fabrics.

Description of preferred embodiments

The invention refers to a personal care absorbent article comprising a laminated structure in which at least one elastic polymeric film is laminated to at least one fibrous layer, especially at least one nonwoven layer. The term "absorbent article" refers to products that are placed against the skin of the wearer to absorb and contain body exudates, like urine, faeces and menstrual fluid. The invention mainly refers to disposable absorbent articles, which means articles that are not intended to be laundered or otherwise restored or reused as an absorbent article after use. The most important type of absorbent articles of this type are diapers, pant diapers, adult incontinence articles and feminine hygiene articles.

Fig. 1 shows an embodiment of a pant diaper 1 for an infant or an incontinent adult. The pant diaper shown in Fig. 1 comprises an absorbent core 2 located in a core region 3 of the article, and a chassis 4 surrounding the core region. The chassis comprises a front panel 5, a back panel 6 and an elastic waist band 7. The article has a longitudinal direction y and a transverse direction x. The entire or part of the front and/or back panels 5 and 6 may be of an elastic laminate. A pant diaper of this type is disclosed in for example WO 2006/093440.

Fig. 2 shows schematically an apparatus 10 for making an elastic laminate according to the invention . A film 1 1 of elastic material is either formed in situ or made previously and unwound from a supply roll (not shown). The film 11 is preferably formed by extruding an elastomeric thermoplastic polymer through a die (not shown).

Thermoplastic elstomers (TPE), sometimes referred to as thermoplastic rubbers, are a class of copolymers or a physical mix of polymers (usually a plastic and a rubber) which consist of materials with both thermoplastic and elastomeric properties. The principal difference between thermoset elastomers and thermoplastic elastomers is the type of crosslinking bond in their structures. In fact, crosslinking is a critical structural factor which contributes to impart high elastic properties. The crosslink in thermoset polymers is a covalent bond created during the vulcanization process. On the other hand the crosslink in thermoplastic elastomer polymers is a weaker dipole or hydrogen bond or takes place in only in one of the phases of the material. This phase is often referred to as the "hard blocks" and has a melting temperature (Tm) or glass transition temperature (Tg) higher than the other phase, the "soft blocks".

The material is elastic as long as the temperature is between the Tg (glass transition temperature) of the "soft blocks" and the Tg or Tm (melting point) of the "hard blocks". At temperatures above the Tg or Tm of the "hard blocks", the material will be in the form of a melt.

There are six generic classes of TPEs generally considered to exist commercially. These are styrenic block copolymers, polyolefin blends, elastomeric alloys, thermoplastic polyurethanes, thermoplastic copolyester and thermoplastic polyamides. Examples of TPE products that come from block copolymers group are Styroflex™ (BASF), Kraton™ (Shell chemicals), Pellethane™, (Dow Chemicals), Pebax™, Arnitel™ (DSM), Hytrel™ (Du Pont) and more. While there are three main commercial products of elastomer alloy: Santoprene™ (Monsanto), Geolast™ (Monsanto) and Alcryn™ (Du Pont). Examples of polyolefin elastomers are Versify™ and Affinity™ (Dow Chemicals).

In order to qualify as a thermoplastic elastomer, a material must have these three essential characteristics:

1. The ability to be stretched to moderate elongations and, upon the removal of stress, return to something close to its original shape.

2. Processable as a melt at elevated temperature. 3. Absence of significant creep.

The film may be monolayer film or a multilayer film, for example a film having having at least one core layer and outer skin layers. The film may further be breathable, for example by being apertured. A breathable film preferably has a Water Vapour Transmission Rate according to ASTM E96-00 Procedure D of at least 1500 g/m² 24h, more preferably at least 3000 g/m²24h. Alternatively the film is non-breathable.

Before heating and stretching, the film has a basis weight of 20-80 g/m², preferably 20-50 and more preferably 30-50 g/m²,

The film 1 1 is stretched in a stretching device 12, which for example comprises a pair of rolls over which the film is led and that are driven at different speeds so as to cause the film to be stretched in the feeding direction. The way of stretching the film is not critical and other devices for stretching the film in either the feeding or cross-feeding direction may be used.

The film is heated before stretching, for example by heated rolls 13, arranged before the stretching device 12, and/or simultaneously with the stretching process by suitable heating means 14. If the film is heated during stretching, pre-heating may be eliminated, and if preheating is used, heating during stretching can be eliminated. In an alternative embodiment both pre-heating and heating during the stretching process are used.

Heating and stretching means may be the same, for example heated rolls. Other methods for heating the film are by hot air, radiation etc.

The film 11 should be heated so that its temperature during stretching is at least 40^°C, preferably at least 45^°C, The heating temperature should of course not be higher than ensuring that the film integrity is maintained during the process, which means a temperature at least 10^°C below the melting temperature or the glass transition temperature respectively of the hard blocks of the polymeric material of the elastic film.

Polymers have a melting point or a glass transition temperature depending on their degree of crystallinity.

The elasticity of a polymeric material is derived from the ability of the polymer chains to reconfigure themselves to distribute the applied stress. Upon release of the applied stress the polymeric chains seek their relaxed network structure. However, if the applied force is applied under a prolonged time or if the temperature makes the polymers able to move in relation -to each other, the network may not go all the way back to the original configuration. The result is a permanent set/elongation.

The film is stretched to such an extent that its dimension in the stretching direction is increased between 100 and 500%, preferably between 200 and 500%, of its original dimension. The extent of stretching can be determined by the basis weight reduction obtained.

The elastic film will loose some of its elasticity upon this stretching process and thus be permanently deformed to a certain extent. However it will maintain some of its original elasticity, which is sufficient for the intended use of the laminate.

The purpose is to achieve at least 20%, preferably at least 30% and more preferably at least 40% permanent elongation by heating, so that the film does not fully retract upon relaxation. The permanent elongation is determined by the Elasticity test described below.

The stretching may take place in two or more successive steps, which may be more kind to the film, especially at high degrees of stretching.

While kept in said stretched condition the film is laminated to at least one fibrous layer, preferably a nonwoven material. In the embodiment shown in Fig. 2, two nonwoven materials 15 and 16 are laminated to the film 1 1 in a lamination station 17. Examples of suitable nonwoven materials are spunbond materials, meltblown materials and carded webs. The basis weight of the fibrous material layers can vary depending on the intended use of the laminate. For use in personal care absorbent articles the basis weight of the nonwoven material is typically between 10 and 35 g/m².

Examples of suitable polymers used in the fibrous materials are polyethylene, polypropylene and other polyolefin homopolymers and copolymers, polyesters etc. Natural fibres, for example cotton, may also be used as long as they provide the required properties. A mixture of polymers can contribute to a higher flexibility of the nonwoven layer, and through this, give the nonwoven material a higher elongation at maximum load. A mixture of polyethylene and polypropylene polymers has proved to provide good results in this respect. A mixture of fibers of different polymers is also possible. Conjugate fibers may also be used, in which two or more polymers are arranged in positioned distinct zones across the cross-section of the conjugate fibers. Conjugate fibers are also referred to a bicomponent or multicomponent fibers.

Lamination of the nonwoven layers 15 and 16 to the stretched elastic film can be made in conventional way by adhesive bonding, thermal bonding and/or ultrasonic welding or other suitable technique. The laminate is designated with the numeral 18.

After relaxation of the laminate 18 the stretched film will recover at least to some extent. The term "recover" refers to a contraction of a stretched material upon release of a stretching force. The degree of recovery can vary, but preferably the film will recover at least 30% of its elongation. This means that in the case the film has been stretched 100% to a stretched length that is 200% of the original length, the film should recover to a length that is not more than 170% of its original length before stretching. Preferably the elastic film will recover at least 50% of its elongation after relaxation.

The nonwoven layers 15 and 17 laminated to the film 1 1 will contract together with the film and gather, thus allowing the laminate 18 to be stretched at least to a degree up to the original dimension of the nonwoven materials 15 and 16.

Due to the permanent elongation of the film referred to above the thickness of the film is reduced. It is often an advantage to be able to reduce the thickness of the elastic film since elastic films are expensive and a thickness reduction means savings in material and cost. It may also result in a higher comfort, since a reduced thickness results in a more pliable laminate. An advantage of stretching the film while heated is that the permanent deformation of the film is increased as compared to stretching without heating, thus resulting in a higher reduction of the film thickness.

For use in personal care absorbent articles the basis weight of the elastic film is typically between 12 and 30 g/m². The basis weight of the laminate is typically between 40 and 180 g/m².

The temperature to which the elastic film is heated, and the degree of stretching are tools to control the permanent elongation of the elastic film. Thus a higher temperature will result in a higher degree of permanent elongation and so will a higher degree of stretching. It is therefore possible to control the permanent elongation and thus the elasticity of the laminate by controlling one or both of these parameters.

Thin elastic films and thin elastic laminates are advantageous both for cost saving reasons and for comfort reasons. Low basis weight films and laminates when used in for example absorbent articles intended to be worn against the body of a user, means higher comfort and lower pressure against the body.

The elastic laminate produced according to the invention has an elasticity in at least one direction of at least 30% when measured according to the Elasticity test specified below.

It is understood that the elastic laminate according to the invention comprises at least one elastic film layer and at least one fibrous layer laminated thereto. It may further comprise two fibrous layers laminated to the opposite sides of the film layer and it may comprise additional elastic film layers and fibrous layers. In case the laminate comprises two or more elastic films, at least one or all elastic films are heated and stretched according to the method described.

Fig. 3 shows schematically a method for producing pant-type absorbent articles of the type shown in Fig. 1. The process in Fig. 3 is preferably a direct in-line continuation of the stretching and lamination process shown in Fig. 2. A chassis structure is formed that is intended to carry an absorbent core component. In the shown embodiment a core component is formed separately as a "core pack", with an absorbent core 3 enclosed between a topsheet and a liquid impermeable backsheet. In alternative embodiments parts of the chassis structure are utilized as topsheet and/or backsheet.

In the process shown in Fig. 3 continuous webs of material are used to form different chassis web portions such as crotch portion, front and back panel portions and waist band portion. A multiple chassis structure is formed from a compound chassis web 20, first and second elastic laminate webs 18a, b and a first and second waist features 21 , 22. The elastic laminate webs 18a, b are of the elastic laminate 18 produced in the process of Fig. 2.

In an in-line lamination process for pant articles the elastic laminate produces in the process is kept in a stretched condition. Before joining the elastic laminate webs 18a, b to the central nonwoven chassis web 20 the laminate can be passed through a relaxation zone 19 where they are partially relaxed in the machine direction (MD) by at least 4% the reduce the effect of edges to curl. The laminate is preferably kept in a stretched condition including some minor relaxation for processability.

Waist features 21 , 22 are formed by joining separate nonwoven strips 23, 24 to the outer edges of the stretched elastic laminate webs 18a, b, attaching elongated elastic elements 25, such as elastic threads, to the nonwoven strips 23, 24 and folding and securing the nonwoven strips 23, 24 over the elastic elements 25 to create elastic waistbands along the edges of the compound chassis web 20.

The elastic waist portions may alternatively be formed by folding one edge of one or both of the elastic laminate webs 18a, b. The folded web will have greater elastic force than a non-folded web. If desired, the folded laminate web may be supplemented with additional elastic elements. It is also possible to create a waist feature at the edge of one or both of the elastic laminate webs 18a, b by attaching elastic elements to the web and optionally covering the elastic elements with a separate nonwoven.

A core component 26 is produced separately from the pant-forming process and is laid down on the compound chassis web 22. The core component 26 comprises an absorbent core 3 arranged between a liquid barrier layer or backsheet 27 and a liquid pervious topsheet layer 28.

It is to be understood that the construction of the core component 26 and the absorbent core 3 by no means are limiting. Hence, any commonly employed core concepts and materials may be used in the article according to the invention.

The process shown in Fig. 3 does not include the application of leg elastics. However, it is of course possible to apply leg elastics if additional elastification is needed in the leg openings. Leg elastics may be applied by any known manner and using any known elastic elements.

As shown in Fig. 3 the stretched elastic laminate webs 18a, b are joined to the central nonwoven chassis web 20. The process may alternatively involve feeding an elastic web 18 as shown in Fig. 2 and subsequently cutting the web into two web halves 18a and b. After the central nonwoven chassis web 20 has been joined to the stretched elastic laminate webs 18a, b, a portion 30 is cut out from the compound web 22 between the core components 26 to create leg openings 31 . The compound chassis web and the integrated core components 26 are then folded centrally and the web halves are joined in side seams 32 between the core components 26. Finally, individual pant diapers 21 are cut from the production web. The core components 26 may of course alternatively be joined to the chassis web after the leg cut-outs 31 have been made.

By using nonwoven materials having thermoplastic properties in elastic laminate webs, the webs can be joined to other components by thermo-bonding and ultrasonic welding techniques. For example, it may be beneficial if at least one of the fibrous layers in a three- layer nonwove-film-nonwoven laminate 18 is substantially or completely made of thermoplastic fibers. The nonwoven layers can then be used to form side seams with good tensile strength.

Fig. 3 is a highly schematic representation of a method for producing an absorbent article. However all individual steps not closer described, such as cutting, bonding, folding etc. are well known to a person skilled in the art.

The absorbent article shown in Fig. 1 and the method for producing such an article as illustrated in Fig. 3, in which the front and back body panels of a pant-type absorbent article are made of the elastic laminate, are only non-limiting examples of an article and of a method for its production. The elastic laminate 18 may form part of any optional type of absorbent article, as previously mentioned, and be incorporated as any optional elastic component in such an article, for example in elastic side tabs or ears, in belts or part of belts, in elastic side panels and/or in parts of front and back body panels.

It is described above that the elastic laminate is passed through a relaxation zone 19 allowing the elastic laminate to partly relax before it is combined with the other components of the chassis. In an alternative process the relaxation zone may be eliminated and the laminate is incorporated in the article in the stretched condition it had during lamination. Depending on where and how in an absorbent article the elastic laminate is incorporated the laminate may alternatively be more or less fully relaxed when joined to other components of the absorbent article, Description of test methods

Elasticity test The method measures how an elastic material behaves at repeated load and unload cycles. The sample is stretched to a predetermined elongation and a cyclic movement between 0 and said predetermined elongation is performed. Desired load and unload forces are recorded. The permanent, i.e. remaining, elongation of the relaxed material is measured.

A suitable tensile tester, such as Lloyd LRX, able to perform cyclic movements and equipped with a printer/plotter or software presentation is used. The sample is prepared by cutting it to a width of 25.4 mm and a length that is preferably 20 mm longer than the distance between the clamps in the tensile tester. Condition sample at a temperature of 23°C±1°C and 50% RH±5%RH before testing.

The tensile tester is calibrated according to the apparatus instructions. The parameters needed for the test (load and unload forces) are adjusted to:

• Crosshead speed: 500 mm/min ® Clamp distance: 50 mm

• Preload: 0.05 N

The sample is placed in the clamps according to the markings made for the clamps and it is made sure that the sample is centred and fastened perpendicularly in the clamps. The tensile tester is started and three cycles between 0 and the predetermined elongation are performed. There is no pause between the first and second cycle. Before the last cycle, the sample is relaxed for 1 minute, then the permanent elongation is measured by stretching the sample until a force of 0.1 N is detected and the elongation is read.

The term elastic is used herein to define a material having a permanent elongation after relaxation of less than 10% after the material has been subjected to an elongation of 30% in the test above. An elongation of 30% means an elongation to a length that is 30% longer than the initial length of the sample. Tensile strength test

The method is meant for determination of the tensile strength and elongation of elastic films and laminates.

Tensile strength and elongation of a well-defined test piece is tested by means of a suitable tensile tester, for example Lloyd LRX.,

Apparatus: Tensile tester connected to a computer:

Crosshead speed: A 500 mm/m Clamp distance: A 50 mm Sample cutter or cutter tool, accuracy: ± 0.1 mm Silicone paper.

For tests of shorter material pieces than stated above the distance between the clamps should be adapted to the available material length and the test is performed in the same manner as stated above. For pieces having a width less than 25.4 mm the method can also be performed in the same manner, however a recalculation of the test result has to be made to correspond to a width of 25.4 mm.

Sample preparation:

Cut test sample from the entire width of a film or laminate. The width of the sample shall be 25.4 mm and the length 50 mm longer than the clamp distance if possible. Check that the cutter blade is undamaged. It is of importance that the edges of the sample are even and without break notches. Cut samples in the direction of elasticity. Condition samples at least 4h in 50% RH ±5% RH and 23⁰C ±1 ⁰C before testing.

Procedure:

Calibrate the tensile tester according to the apparatus instruction and set it to zero.

Prevent material slipping by using clamps covered with galloon or similar material.

Mount the sample and check that it is not obliquely or unevenly fastened.

Start the tensile tester. Stop the tensile tester after the sample has broken; if it is not automatically controlled. If possible do not use measurements resulting from premature failures, i.e. specimen that breaks at clamp or damaged from sample preparation.

Maximum force N/25.4mm Elongation at maximum force, % Force at 25% elongation, % Force at 10% elongation, % Force at 5% elongation, % Force at 3% elongation, % Break force, N/25.4 mm

Elongation at break force, %.

The tensile strength is defined as maximum force in N/25.4mm. State the accuracy of the results by 1 decimal for forces and round off to the nearest ten for elongation.

The test is a specified version of the ASTM D 882 test.

Example

An elastic laminate was produced comprising an inner layer of an elastic film and a pair of outer nonwoven layers. The film was a 30 g/m² multilayer elastic film form Pliant Corp. having a styrene based core layer and polyolefin skin layers. The nonwoven layers were spunbond nonwovens and each had a basis weight of 17 g/m². The film was heated and stretched 3.7 times its original length and laminated to the two nowoven materials by ultrasonic welding. Heating was in one test made with an IR heating lamp with the power 2000W and with the distance 0.3 m and the film was heated stepwise. In other tests heating was made by heating a roll over which the film was passed. The roll was heated by the IR lamp. The test was made in the temperature interval 23 to 8O⁰C.

Fig. 4 illustrates the available stretch, the so called inflection point in stretch-strain curve, of the laminate, wherein the film has been heated to different temperatures and stretched.

The inflection point in stretch-strain curve is achieved by the Tensile strength test referred to above and is defined as the percent elongation of the laminate when the slope of the stretch-strain curve increases above 0.4N/% per 25.4mm. As is seen from Fig. 4 the inflection point in stretch-strain curve starts to be reduced around the heating temperature 4O⁰C. Table 1 below shows the inflection point in stretch-strain curve, the force at 80% and 100% elongation, maximum force and break elongation for the laminate in the MD of the laminate.

Table 1

Claims

1. A personal care absorbent article comprising an elastic laminate, said laminate comprises at least one elastic thermoplastic polymeric film laminated to at least one fibrous layer, wherein the fibrous layers are laminated to the film being in a stretched condition, so that the fibrous layers are gathered, characterized in that said elastic film has a basis weight between 12 and 30 g/m², and the laminate has a tensile strength of at least 5N/25.4mm, preferably at least 10N/25.4mm in the machine direction of the laminate.

2. The personal care absorbent article as claimed in claim 1 , characterized in that the elastic laminate is contained in any of the following components of the absorbent article: in elastic side tabs or ears, in belts or part of belts, in elastic side panels and/or in front and back body panels or parts thereof.

3. The personal care absorbent article as claimed in claim 1 or 2, characterized in that the article is selected from the group consisting of: a diaper, a pant diaper, an adult incontinence article and a feminine hygiene article.

4. The personal care absorbent article as claimed in any of the preceding claims, characterized in that the laminate has a basis weight between 40 and 180 . g/m².

5. A method for manufacturing a personal care absorbent article comprising an elastic laminate, said laminate comprising at least one elastic thermoplastic polymeric film laminated to at least one fibrous layer, said method comprising: providing said elastic film, heating and stretching the heated elastic film in at least one direction so that the elastic film during stretching has a temperature of at least 4O⁰C, wherein stretching is performed so as to extend the dimension of the film in the stretching direction between 100 and 500% of its original dimension, laminating said fibrous layer to the elastic film while this is in its stretched condition and subsequently incorporating the laminate in an absorbent article keeping the laminate in a stretched or in an at least partly relaxed condition.

6, The method as claimed in claim 5, characterized in that the laminate is produced in a process which is in-line with the incorporation of the laminate in the absorbent article.

7. The method as claimed in claim 5 or 6, characterized in that said heated film

(11 ) is stretched to extend its dimension in the stretching direction between 200 and 500% of its original dimension.

8. The method as claimed in any of claims 5-7, characterized in that after relaxation of the laminate (18) the elastic film (1 1 ) recovers not more than 80% of its elongation.

9. The method as claimed in claim 8, characterized in that after relaxation of the laminate (18) the elastic film (1 1 ) recovers at least 30% and preferably at least 50% of its elongation.

10. The method as claimed in any of claims 5-9, characterized in that said elastic film (1 1 ) is stretched so as to have a basis weight after relaxation of between 12 and 30 g/m².

11. The method as claimed in any of claims 5-10, characterized in that the film during stretching has a temperature of at least 45⁰C.

12. The method as claimed in any of claims 5-1 1 , characterized in that the film during stretching has a temperature which is at least 10⁰C below the melting temperature or the glass transition temperature of the hard blocks in the polymeric material of said elastic film.

13. The method as claimed in any of claims 5-12, characterized in that said lamination (18) is achieved by a bonding process selected from adhesive, thermal and ultrasonic bonding.

14. The method as claimed in any of claims 5-13, characterized in that the elastic film is stretched in two or more successive steps.

15. The method as claimed in any of claims 5-14, characterized in that the elastic laminate is incorporated in a personal care absorbent article selected from a diaper, a pant diaper, an adult incontinence article and a feminine hygiene article

16. The method as claimed in claim 15, characterized in that the laminate is incorporated in any of the following components of an absorbent article in elastic side tabs or ears, in belts or part of belts, in elastic side panels and/or in front and back body panels or parts thereof