Tackified hot melt adhesive composition

Abstract

A hot melt composition is provided that includes a low molecular weight metallocene catalyzed polymer, a high molecular weight polymer, an amorphous polyolefin, and a tackifier. The hot melt composition is particularly useful in absorbent articles such as diapers. The hot melt composition provides particularly good nonwoven-film bonds, but can also be used in nonwoven-nonwoven bonds.

Description

[0001] The present invention relates to a hot melt adhesive composition useful for bonding a first substrate to a second substrate. The hot melt adhesive can be used in absorbent articles such as diapers and provides particularly good nonwoven-film bonds, but can also be used in nonwoven-nonwoven bonds. The hot melt adhesive comprises a blend of polymers with different properties and tackifiers. BACKGROUND

[0002] Disposable absorbent articles, such as diapers, training pants or adult incontinence articles, generally include a liquid permeable topsheet, a liquid impermeable backsheet, and an absorbent core positioned between the topsheet and the backsheet, among other features. The liquid permeable topsheet is positioned next to the wearer's body when the disposable article is worn and allows body fluids to pass into the absorbent core. The liquid impermeable backsheet generally includes a plastic film and optionally a nonwoven outer cover, which prevents leakage of fluids retained in the absorbent core. The absorbent core generally includes superabsorbent polymers (SAP) that can absorb several times its weight of urine or other liquids.

[0003] The various components of a disposable absorbent article are bonded together, either directly or indirectly. Hot melt adhesives have been used to bond the various layers, particularly the topsheet, backsheet, and absorbent core, which together form the chassis of the article. Hot melt adhesives have also been used to bond other discrete components such as fasteners and leg elastics or cuffs to the chassis of the article. Hot melt adhesives are often referred to as construction adhesives for these applications because they help construct the absorbent article from the various components. Adhesives are also used to form the backsheet laminate, which includes a liquid impermeable film and an outer-facing nonwoven cover. Other bonding means such as fusion bonding and ultrasonic bonding can also be used, but these means are generally not practical for thin layers and when large surfaces are to be bonded.

[0004] Hot melt adhesives are made by combining polymeric components and additive components in a substantially homogeneous thermoplastic blend. Typical additive components include tackifiers, plasticizers, and / or waxes.

[0005] Various hot melt compositions have been disclosed in the prior art. WO 2019 / 204,541 (Turner et al.) discloses adhesive compositions having a viscosity at 150°C of about 2.000 mPa.s to about 11,500 mPa.s, a storage modulus (G') at 37°C of between about 3 MPa to about 9.5 MPa, a yield stress at 37°C of about 0.8 MPa to about 1.45 MPa, perform well in adhesive hard film laminates, and generally also perform well in nonwoven-nonwoven laminates. These adhesive hot melt compositions comprise copolymers and preferably have a heat of fusion at 37°C of about 2 MJ / m 3 to about 8 MJ / m 3Its resilience.

[0006] Instead of using formulated binders, unblended polymers have been proposed. Unblended polymers consist of blends of polymers of only one type (formed by themselves and specific polymerization methods) rather than polymers prepared by separate polymerization methods and then mixed (blended) together after polymerization. Unblended polymers may also contain trace amounts of additives, such as antioxidants, fragrances, and other low molecular weight components, but are essentially free of other polymers, mineral oils, or tackifiers.

[0007] Hot melt compositions of propylene-based copolymers incorporating metallocene catalysts have been proposed, see, for example, WO2016 / 153,663A1, WO2014 / 194,074A1, WO2019 / 94659A1 and US2020 / 0108,168A1. For example, US2016 / 053,149A1 (Clariant) discloses a ready-to-use hot melt adhesive comprising at least 95% of one or more polyolefin copolymer waxes prepared using a metallocene catalyst, characterized in that the polyolefin copolymer wax is composed of propylene and one or more additional monomers selected from ethylene and branched or unbranched 1-olefins having 4 to 20 carbon atoms, and the propylene-derived structural units in the copolymer wax are present in an amount of 80% to 99.9% by weight, and the hot melt adhesive has a melt surface tension of up to 23 mN / m measured at a temperature of 170°C.

[0008] Clariant manufactures and sells products made from metallocene catalysts (mPO) under the trademark [brand name missing]. Pure polyolefins (mPO) are marketed as hot melt adhesives. However, hot melt compositions containing pure mPO have been found to have several limitations. First, NW-film adhesives prepared using pure mPO as an adhesive are relatively weak. They are prone to failure due to adhesive breakage between the adhesive and the film. Second, ligocenes (such as Licocenes 2502) have relatively short open times, and for some applications, this requires additional bonding rollers in the process, which incurs costs. Third, after a run time of 1 to 3 minutes, for high-speed slit applications, they often lead to adhesive buildup (“contamination”) downstream of the slit nozzle.

[0009] When developing mPO-based blends, the benefits of pure mPO should be minimized while overcoming the aforementioned limitations.

[0010] Conventionally, it was found beneficial to add a plasticizer to compensate for the too high hot melt blend viscosity. Typically, for this purpose mineral oil is added. Mineral oil has several drawbacks such as volatility (odour), spreading over time into other substrates like PE films or onto the surface of other materials (like SAP) which weakens the bond and deteriorates the function of other parts of the diaper. Mineral oil also helps to reduce the thermal stability of the adhesive in the heated melt tank during processing, making the adhesive thermally degrade faster over time.

[0011] Therefore, there is a need for a hot melt composition which is able to provide good nonwoven-film bonds, ideally also nonwoven-nonwoven bonds, and which can optionally be formulated without mineral oil. SUMMARY

[0012] In a first aspect, the present invention provides a hot melt composition comprising:

[0013] - a low molecular weight metallocene catalysed polymer having a peak molecular weight below 130,000 g / mol;

[0014] - a high molecular weight polyolefin having a peak molecular weight of 130,000 g / mol to 700,000 g / mol;

[0015] - an amorphous polyolefin having a crystallization enthalpy of less than 10 J / g; and

[0016] - a tackifier.

[0017] The hot melt composition according to the present invention can be formulated in relatively low amounts and is preferably free of mineral oil. The hot melt composition is particularly useful in absorbent hygiene articles, such as baby diapers, adult incontinence diapers or sanitary napkins, to make nonwoven-film bonds and / or nonwoven-nonwoven bonds. In a second aspect, the present invention thus provides an absorbent article comprising a first substrate and a second substrate, the first substrate and the second substrate being bonded to each other by the hot melt composition. The invention is in a third aspect a method of bonding a first substrate with a second substrate with the hot melt composition.

[0018] The inventors have found that the high molecular weight polyolefins described herein exert a surprising strong strain hardening effect, i.e. even an increased resistance to crack propagation deformation. Strain hardening is considered a “self-repairing mechanism” of the hot melt composition upon straining, which avoids early breakage. The hot melt formulation of the present invention can also be easily applied with the desired open time.

[0019] The above and other features and advantages of the present disclosure and the manner of obtaining them will become more apparent, and the present disclosure itself will be better understood by reference to the following description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A perspective view of an exemplary taped diaper is shown, in a closed configuration, as it would be worn by a wearer;

[0021] Figure 2 A garment-facing side of the diaper of Figure 1 is shown, with the diaper laid flat;

[0022] Figure 3 A wearer-facing side of the diaper of Figure 1 is shown, with the diaper laid flat;

[0023] Figure 4 A top view of an exemplary absorbent core is shown, with the top layer partially removed;

[0024] Figure 5 A longitudinal cross-sectional view of the absorbent core of Figure 4 is shown;

[0025] Figure 6 A transverse cross-sectional view of the absorbent core of Figure 4 is shown. DETAILED DESCRIPTION

[0026] INTRODUCTION

[0027] As used herein, "comprising" and "including," mean the inclusion of one or more steps, elements, components, steps, features, or aspects of the method, process, system, composition, or apparatus, but not the exclusion of any other steps, elements, components, steps, features, or aspects. Any feature shown in the following description is optional, unless otherwise indicated. Each component of the application can contain one or more sub-components having the specified properties, unless otherwise indicated. For example, "a low molecular weight polymer" means "one or more low molecular weight polymers" having the specified molecular weight.

[0028] The components of the hot melt composition of the present application are described in more detail below.

[0029] Low molecular weight metallocene catalyzed polymers

[0030] The hot melt composition comprises a low molecular weight metallocene catalysed polymer having a peak molecular weight below 130,000 g / mol. The peak molecular weight can for example be in the range of 5,000 g / mol to 130,000 g / mol. The peak molecular weight is measured as further indicated below in the experimental section. For any component indicated in the claims, the composition can comprise one such low molecular weight metallocene catalysed polymer, or a blend of two or more such low molecular weight metallocene catalysed polymers. Thus, unless otherwise indicated, when the term "low molecular weight metallocene catalysed polymer" is used, it refers to "one or more low molecular weight metallocene catalysed polymers".

[0031] The hot melt composition can typically comprise 20 wt% to 70 wt% of the low molecular weight metallocene catalysed polymer (or mixture thereof), in particular 30 wt% to 60 wt% of the low molecular weight metallocene catalysed polymer.

[0032] The metallocene catalysed polymer typically has a conventional spatial repeat monomer unit distribution and a narrow molecular weight distribution, as known in the art. The metallocene catalysed polymer useful in the present application can be described as low crystalline or semi-crystalline, having a crystallisation enthalpy typically in the range of 5 J / g to 45 J / g, measured according to the crystallisation enthalpy test method described below.

[0033] The low molecular weight metallocene catalysed polymer can in particular be propylene based. The propylene based metallocene catalysed polymer can be a homopolymer or a copolymer, in particular a propylene-ethylene copolymer.

[0034] The propylene-ethylene copolymer comprises a copolymer of at least 50 wt%, in particular at least 60 wt%, or at least 70 wt%, or at least 80 wt% of propylene units. The remaining monomers are ethylene monomers, optionally other alpha olefin monomers can be present in the copolymer, for example 4-methyl-1-pentene, pentene-1, 2-methylpentene-1, 3-methylbutene-1, heptene-1, dimethylpentene-1, trimethylbutene-1, ethylpentene-1, methylpentene-1, trimethylpentene-1, methylethylpentene-1, 1-octene, diethylbutene-1, propylpentane-1, decene-1, methylnonene-1, nonene-1, trimethylheptene-1, methylethylbutene-1, dodecene-1, and hexadecene-1, and combinations thereof. The exact monomer distribution is typically disclosed by the supplier, but can also be determined by suitable methods, such as nuclear magnetic resonance or infrared spectroscopy.

[0035] Suitable metallocene catalysed propylene-ethylene copolymers can be in the polymer range are commercially available from Clariant with a wide range of properties such as molecular weight, viscosity, crystallinity, etc. US 2016 / 053,149 Al assigned to Clariant also describes suitable copolymers and shows on page 5 that these examples were produced by the method shown in EP 571,882. For a given catalyst system and a given comonomer ratio, the molecular weight is adjusted via the hydrogen partial pressure as a molar mass regulator.

[0036] The low molecular weight metallocene catalysed polymer can also comprise a blend of two copolymers, in particular:

[0037] - a first low molecular weight metallocene catalysed propylene-ethylene copolymer having a crystallisation enthalpy below 20 J / g;

[0038] and

[0039] - a second low molecular weight metallocene catalysed propylene-ethylene copolymer having a crystallisation enthalpy above 20 J / g.

[0040] Without being bound by theory, it is believed that the stiffness of a hot melt composition based on semi-crystalline polymers is related to the crystallinity of the polymer. Therefore, when formulating the composition according to the present application, the crystallinity of the low molecular weight metallocene based polymer as backbone of the formula should be considered. The crystallisation enthalpy is measured according to the crystallisation enthalpy test method described hereinafter.

[0041] The first low molecular weight metallocene catalysed propylene-ethylene copolymer has a crystallisation enthalpy of less than 20 J / g, in particular 5 J / g to 15 J / g, and can be described as low crystalline. A commercial example of the first copolymer is Licocene® PP 1602 from Clariant. PP 1602. Licocene PP 1602 is sold as granules and is described as a low melting, metallocene technology based propylene-ethylene copolymer which exhibits a low degree of crystallinity. The Mp of PP 1602 is measured as 75,900 g / mol and its crystallisation enthalpy is 16.7 J / g (see measurement method hereinafter). Another example is PP 1302. The Mp of PP 1302 is measured as 24,100 g / mol and its crystallisation enthalpy is 11.8 J / g.

[0042] The second low molecular weight metallocene catalysed propylene-ethylene copolymer has a crystallisation enthalpy of at least 20 J / g, in particular 25 J / g to 45 J / g, which is higher than the first copolymer. Polymers in this range can be described as semi-crystalline. The second copolymer can have an Mp in the range of 50,000 g / mol to 130,000 g / mol, or 60,000 g / mol to 110,000 g / mol. A commercial example of the second copolymer is PP 3602, which is sold as a granulate, and which is described as a low crystalline metallocene catalyzed propylene-ethylene copolymer. 3602 has a measured crystallization enthalpy of 35.0 J / g.

[0043] The first and second copolymers described above can typically be blended in a weight ratio of 10:90 to 90:10, for example 50:50 or 2:1 or 1 :2. It was found that blending two lower molecular weight copolymers with different crystallinities enables to achieve low stiffness (as specifically required for NW film construction bonds), while still maintaining high toughness (as generally required for NW-NW and NW film construction bonds).

[0044] One example is a blend of 3602 and 1602, both propylene-ethylene copolymers from Clariant. Licocene 3602 is a relatively highly crystalline polymer, while Licocene 1602 has a medium crystallinity. In a blend of the two copolymers, the overall crystallinity can be adjusted in a way that the resulting hot melt composition has a sufficiently low stiffness as required for strong NW-film bonds, but still has a high toughness. For example, it was found that the "building blocks" of Licocene 1602 and Licocene 3602 in a 2:1 ratio are superior to the use of pure Licocene 2502. The 2:1 blend of 1602 and 3602 has a lower crystallinity and thus a lower stiffness than Licocene 2502, while the higher peak molecular weight of 1602 and 3602 (75,900 g / mol and 62570 g / mol) compared to 2502 (57,100 g / mol) compensates for toughness. Of course, other ratios can be used depending on the application.

[0045] The low molecular weight metallocene catalyzed polymer can also consist of a single low molecular weight metallocene catalyzed polymer copolymer. The inventors found that the low molecular weight metallocene catalyzed polyolefin PP 2402 is particularly suitable for this purpose, as it enables to use a high molecular weight polyolefin with a peak molecular weight - in particular higher than 200,000 g / mol, while still maintaining a low viscosity, for example lower than 3000 mPa.s at 150°C. A low viscosity is required whenever the hot adhesive is applied directly to a heat sensitive substrate, for example a polyethylene film as "first substrate", instead of to a less heat sensitive polypropylene nonwoven which is combined with the heat sensitive substrate (as "second substrate") after the adhesive has cooled down to a certain extent. The low molecular weight metallocene catalyzed polyolefin PP 2402 is a low molecular weight metallocene catalyzed polyolefin having a crystallization enthalpy of about 24 J / g, a peak molecular weight (Mp) of about 28,000 g / mol and a viscosity at 150°C of about 2,000 mPa.s.

[0046] High molecular weight polyolefins

[0047] According to the present invention, the inventors have found that the cohesive strength of the formulation can be significantly increased when using a polyolefin having a high peak molecular weight Mp of 130,000 g / mol to 700,000 g / mol. The high molecular weight polyolefin can have a peak molecular weight that is at least 10,000 g / mol, in particular at least 20,000 g / mol or even at least 50,000 g / mol greater than the peak molecular weight (of the highest value of the blend) of the low molecular weight metallocene catalyzed polymer described above. The high molecular weight polyolefin can in particular have a peak molecular weight of 140,000 g / mol to 410,000 g / mol, or 150,000 g / mol to 360,000 g / mol.

[0048] The inventors have surprisingly found that the addition of a longer molecular weight polyolefin significantly increases the strain hardening of the blend in addition to increasing the elongation at break, which in combination results in a significantly higher toughness of the formulation. Strain hardening is believed to be a "self-repair mechanism" of the blend upon straining, which avoids early breakage.

[0049] The high molecular weight polyolefin can advantageously consist of a single material to simplify compounding and formulation of the hot melt composition, but it is not excluded that it can also be a blend of individual materials falling within this definition. The hot melt composition can typically comprise 1% to 20% of such high molecular weight polyolefin (or mixtures thereof) by weight of the hot melt composition, in particular 2% to 15% by weight of the hot melt composition, especially 5% to 10%. It is believed that the addition of small amounts of longer molecular weight polyolefin can significantly enhance the strain hardening and thus the toughness. On the other hand, more than 10% can increase the viscosity. The toughness, strain hardening and elongation at break are measured and observed in the Tensile Test Method, subjecting the adhesive to large deformations as relevant when the bond is subjected to forces in use.

[0050] The high molecular weight polyolefin can be a homopolymer or a copolymer. The copolymer can comprise different alpha olefin monomers such as ethylene, propylene, 4-methyl-1-pentene, pentene-1, 2-methylpentene-1, 3-methylbutene-1, heptene-1, dimethylpentene-1, trimethylbutene-1, ethylpentene-1, methylpentene-1, trimethylpentene-1, methyl ethyl pentene-1, 1-octene, diethylbutene-1, propylpentane-1, decene-1, methyl nonene-1, nonene-1, trimethylheptene-1, methyl ethyl butene-1, dodecene-1, and hexadecene-1, and combinations thereof.

[0051] Non-limiting examples of commercially available high molecular weight polyolefins are Affinity EG 8200G, Engage 8200, Infuse 9817, Vistamaxx 3000, Vistamaxx 6102, Vistamaxx 6202, Vistamaxx 6502, VERsify 4200, VERsify 4301.

[0052] The high molecular weight polyolefin can in particular be a propylene-ethylene copolymer. The high molecular weight polyolefin can in particular be a propylene-ethylene copolymer comprising more than 80 wt% of polypropylene units with isotactic stereochemistry. The high molecular weight polyolefin can also be a metallocene catalyzed copolymer, in particular a metallocene catalyzed propylene-ethylene copolymer. Examples of such copolymers are commercially available as the Vistamaxx series from ExxonMobil. For example, Vistamaxx 6202 and Vistamaxx 6502 are sold as pellets and are described by their manufacturer as consisting mainly of isotactic propylene repeat units with a random distribution of ethylene produced using metallocene catalyst technology. Vistamaxx 6202 and 6502 are used as high molecular weight polymers in the formulation product examples below. Vistamaxx 6502 has the lowest viscosity and therefore the smallest impact on increasing the viscosity of the total composition.

[0053] It was found that a higher molecular weight is beneficial to achieve the required toughness, as long as it can still be balanced against the increase in viscosity. In particular for applications where a sprayable adhesive equal to or below 155°C is required to avoid thermal damage of heat sensitive first substrates, there is usually a limitation in the choice of high molecular weight polyolefins to avoid too high a viscosity. Polyolefins with a melt flow rate measured according to ASTM D1238 at 230°C / 2.16 kg of 20 to 300 g / 10 min, such as Vistamaxx 6502, are typically used, while higher molecular weight polyolefins with a corresponding low melt flow rate, in particular a melt flow rate measured at 230°C / 2.16 kg of less than 20 g / 10 min, such as Vistamaxx 6202, are typically avoided to keep the low viscosity of the composition.

[0054] The present invention also enables the use of high molecular weight polyolefins having a melt flow rate below 20 g / 10 min measured at 230°C / 2.16 kg, while still enabling the composition to have a low viscosity and good sprayability. This is achieved by combining with a low molecular weight polyolefin having a crystallization heat in the range of 20 J / g to 30 J / g and a peak molecular weight between 25,000 g / mol and 35,000 g / mol, such as Licocene PP 2402.

[0055] Amorphous polyolefins

[0056] According to the present invention, it was found that the addition of an amorphous polyolefin to the above-mentioned polymers provides a processable hot melt adhesive. The hot melt composition can comprise a single amorphous polyolefin or a mixture thereof. In the following, "amorphous polyolefin" means "at least one amorphous polyolefin", unless otherwise specified. The hot melt adhesive composition can comprise at least 1 wt.% of such amorphous polyolefin, in particular, the amorphous polyolefin can be in the range of 1 % to 30 %, in particular 2 % to 25 %, or 5 % to 25 %, by weight of the hot melt adhesive composition.

[0057] The amorphous polyolefin preferably has a crystallization enthalpy of less than 10 J / g, preferably less than 5 J / g, more preferably less than 1 J / g, measured according to the following Crystallization Enthalpy Test Method. The amorphous polyolefin preferably has no crystallinity and thus has a crystallization enthalpy of (about) 0 J / g. The amorphous polyolefin can also be a propylene-based polymer.

[0058] The amorphous polyolefin can have one or more or all of the following properties:

[0059] - a pour point of < 50°C, preferably < 30°C, more preferably < 25°C;

[0060] - a viscosity at 170°C of between 20 mPa.s and 3000 mPa.s, preferably 50 mPa.s to 1000 mPa.s, particularly preferably 80 mPa.s to 500 mPa.s (see Viscosity Test Method below);

[0061] - a density at 23°C of less than 0.95 g / cm3, preferably less than 0.92 g / cm3, particularly between 0.83 g / cm3and 0.90 g / cm3(measured according to ISO 1183); 3 3 3 3

[0062] - a glass transition temperature of <- 35°C, preferably <- 40°C, more preferably <- 45°C, determined by the DSC method according to DIN 11357-2; ​​​​

[0063] - a polydispersity index of less than 5, preferably less than 3, particularly preferably less than 2.5. The polydispersity index PDI is calculated from the quotient of the weight average molecular weight Mw and the number average molecular weight Mn and is determined according to standard ISO 16014.

[0064] The amorphous polyolefin supports the function of the base matrix polymer. This leads to further advantages for the user. For example, fewer components need to be melted and mixed, resulting in a faster and more cost-effective process. The hot melt composition of the present application can advantageously be free of waxes or nucleating agents. The hot melt composition of the present application can also advantageously be free of plasticizers.

[0065] The amorphous polyolefin of the present application preferably comprises or consists of at least one propylene-based polymer. The propylene-based polymer can be a linear propylene homopolymer or copolymer produced using a Ziegler or metallocene catalyst having a propylene content of at least 50 wt.-% or more. Suitable monomer materials preferably include propylene and one or more other monomers selected from ethylene and C4-C18 higher alpha-olefins. The amorphous polyolefin can in particular be a propylene-ethylene copolymer.

[0066] The amorphous propylene-based polymer is preferably prepared by metallocene catalysis, preferably as an amorphous polyalphaolefin copolymer. Without wishing to be bound by theory, the inventors believe that metallocene-catalyzed propylene-based amorphous polymers are able to better compatibilize with other metallocene-catalyzed propylene-based polymers in the composition. The amorphous propylene-based polymer can be a copolymer of propylene with another monomer selected from ethylene and C4-C18 alpha-olefins. The amorphous propylene-based polymer can have a glass transition temperature Tg of less than -20°C, preferably less than -30°C and particularly preferably less than -40°C, as determined by DSC according to DIN EN ISO 11357-2.

[0067] The amorphous propylene-based polymer can be a propylene random copolymer with a propylene fraction of less than 90 wt.-%, preferably a propylene fraction of between 60 wt.-% and 85 wt.-%, more preferably between 72 wt.-% and 82 wt.-%. The amorphous propylene-based polymer can be a copolymer of propylene and ethylene, wherein the copolymer is derived from 60 wt.-% to 85 wt.-% of propylene and 15 wt.-% to 40 wt.-% of ethylene.

[0068] Amorphous polyolefins advantageously have a weight-average molecular weight, measured according to DIN 55672, between 1,000 g / mol and 50,000 g / mol, preferably between 5,000 g / mol and 30,000 g / mol. In particular, the amorphous polyolefin used can be a low molecular weight polymer with a weight-average molecular weight Mw of less than 10,000 g / mol, preferably less than 9,000 g / mol, and particularly preferably less than 7,000 g / mol (measured according to DIN 55672). Amorphous polyolefins also advantageously have a viscosity of less than 500 mPa·s at 170°C, most preferably less than 300 mPa·s. Amorphous polyolefins advantageously have a viscosity of less than 500 mPa·s at 190°C, preferably from 10 mPa·s to 300 mPa·s, more preferably from 50 mPa·s to 200 mPa·s.

[0069] The low viscosity of amorphous polyolefins allows for formulations that are essentially free of mineral oil, while the resulting blends still have sufficiently low viscosity to enable processing via slotting and spraying.

[0070] The amorphous polyolefin exemplified in this article, Licocene PPA 330 from Clariant, is a metallocene-catalyzed propylene-based copolymer with a weight-average molecular weight (Mw) of less than 10,000 g / mol (however, other amorphous polyolefins are also suitable). Because it is completely amorphous (both its enthalpy of crystallization and enthalpy of melting are 0 as measured by DSC), its melting point cannot be detected by DSC. Licocene PPA 330 has the following properties:

[0071] -79.5% by weight propylene content;

[0072] The pour point is -21℃.

[0073] - Viscosity of 141 mPa·s at 170°C and 93 mPa·s at 190°C;

[0074] - Glass transition temperature of -44°C, determined by DSC method according to DIN 11357-2;

[0075] -1.5 polydispersity index (according to standard ISO 16014).

[0076] Tackifier

[0077] The hot melt composition comprises a tackifier (one tackifier or a mixture of tackifiers). It has been found that the tackifier can increase the cohesive strength and open time of the composition. The hot melt composition can generally comprise from 10% to 70%, in particular from 20% to 65%, or from 25% to 60%, or from 26% to 60%, or from 30% to 60%, by weight of the composition, of tackifier. The tackifier, also referred to as "tackifier resin" or "tackifying resin", is a low molecular weight compound (oligomer) which is added to adhesive formulations to improve tack and peel adhesion to adherend materials. Commonly used tackifiers known in the art can be used in the present invention. Typical tackifiers are thermoplastic materials which are stable at least up to 200°C, are amorphous glasses at room temperature, and have a Tg higher than 50°C, preferably comprised between 80°C and 125°C. The tackifier generally has a molecular weight comprised between 500 g / mol and 2000 g / mol.

[0078] The tackifier is typically an organic chemical having a polycyclic structure. Commonly used tackifiers are selected from the group consisting of rosin resins and their derivatives (rosin esters), hydrocarbon resins produced from petroleum-based by-products of naphtha crackers and terpene resins (modified or unmodified). The hydrocarbon resins can be aliphatic, cycloaliphatic and aromatic resins (in particular C5 aliphatic resins, C9 aromatic resins and C5 / C9 aliphatic / aromatic resins), and can optionally be hydrogenated hydrocarbon resins.

[0079] Exemplary tackifiers include aliphatic hydrocarbon resins, aromatic modified aliphatic hydrocarbon resins, hydrogenated polycyclopentadiene resins, polycyclopentadiene resins, gum rosin, gum rosin esters, wood rosin, wood rosin esters, tall oil rosin, tall oil rosin esters, polyterpenes, aromatic modified polyterpenes, terpene-phenolic resins, aromatic modified hydrogenated polycyclopentadiene resins, hydrogenated aliphatic resins, hydrogenated aliphatic aromatic resins, hydrogenated terpenes and modified terpenes, and hydrogenated rosin esters. Particularly suitable tackifiers are rosin (and derivatives thereof) resins and hydrogenated hydrocarbon tackifiers which are solid at room temperature. The tackifier is preferably at least partially hydrogenated, preferably fully hydrogenated. Without wishing to be bound by theory, the inventors believe that a partially hydrogenated or in particular a fully hydrogenated tackifier is better compatible with the other components of the adhesive composition of the present invention. Furthermore, a fully hydrogenated tackifier is preferred because it has a lower tendency to deteriorate the odor of the adhesive formulation and thus of the absorbent article.

[0080] Compounding and optional ingredients

[0081] The hot melt composition can be prepared by heating the polymers at a temperature high enough (e.g., from about 135°C to about 175°C) to melt the polymers. The tackifier and other ingredients (e.g., additives or other polymers) can be added to the molten primary polymer blend. A mixer can be used to mix the polymers and or other additives together into the final hot melt composition.

[0082] The resulting mixture is cooled and adjusted for transport and storage. During application, the hot melt composition is remelted, and any known applicator device, particularly a slit-type coating applicator device (which is a contact applicator), can be used to apply the hot melt composition to the substrate.

[0083] The hot melt composition according to the present invention preferably has a viscosity in the range of about 1,000 mPa·s to about 7,000 mPa·s at 170°C, as measured by the viscosity testing method described herein.

[0084] A significant advantage is the minimization or avoidance of mineral oil use. This reduces the cost of hot-melt compositions and eliminates the potential problems associated with additional ingredients and their supply.

[0085] The hot-melt composition may optionally contain an antioxidant. Non-limiting examples of suitable antioxidants include amine-based antioxidants such as alkyl diphenylamines, phenyl-naphthylamines, alkyl or aralkyl-substituted phenyl-naphthylamines, alkylated p-phenylene diamines, tetramethyl-diaminodiphenylamines, etc.; and hindered phenolic compounds such as 2,6-di-tert-butyl-4-methylphenol; 1,3,5-trimethyl-2,4,6-tris(3',5'-di-tert-butyl-4-hydroxybenzyl)benzene; tetrakis[(methylene(3,5-di-tert-butyl-4-hydroxycinnamate)]methane (e.g., IRGANOX™ 1010, available from Ciba Geigy, New York); octadecyl-3,5-di-tert-butyl-4-hydroxycinnamate (e.g., IRGANOX™ 1076, available from Ciba Geigy, New York). (Available commercially from Geigy) and combinations thereof. When used, the amount of antioxidant in the hot-melt composition may be correspondingly less than 1% by weight, alternatively from about 0.05% to about 0.75%, and alternatively from about 0.1% to about 0.5%.

[0086] The hot-melt composition may optionally contain a UV stabilizer that prevents or reduces degradation of the composition due to radiation. Any UV stabilizer known to those skilled in the art can be used in the hot-melt composition. Non-limiting examples of suitable UV stabilizers include benzophenone, benzotriazole, aryl esters, oxaloaniline, acrylates, formamidinium black, hindered amines, nickel quenchers, hindered amines, phenolic antioxidants, metal salts, zinc compounds, and combinations thereof. When used, the amount of UV stabilizer in the hot-melt composition may be less than 1% by weight, alternatively from about 0.05% to about 0.75%, and alternatively from about 0.1% to about 0.5%.

[0087] The hot melt composition can optionally comprise a whitening agent, a colorant, and / or a pigment. Any colorant or pigment known to those of ordinary skill in the art can be used in the hot melt composition. Non-limiting examples of suitable whitening agents, colorants, and / or pigments include fluorescent materials and pigments such as triazine-stilbene, coumarin, imidazole, diazole, titanium dioxide and carbon black, phthalocyanine pigments and other organic pigments such as IRGAZIN B, CROMOPHTAL B, MONASTRA B, CINQUASIA B, IRGALITE B, ORASOL B, all of which are available from Ciba Specialty Chemicals, Tarrytown, N.Y. In use, the amount of whitening agent, colorant, and / or pigment in the hot melt composition can be less than 10%, alternatively from about 0.01% to about 5%, and alternatively from about 0.1% to about 2%, by weight of the hot melt composition.

[0088] The hot melt composition can optionally comprise a fragrance such as a perfume or other flavor enhancer. Such fragrances can be retained by the liner or contained in a release agent such as a microcapsule that can release the fragrance, for example, upon removal of the release liner from the adhesive composition or upon compression on the adhesive composition. In use, the amount of fragrance in the hot melt composition can be less than 3%, alternatively less than 2%, alternatively less than 1%, alternatively from about 0.05% to about 0.75%, and alternatively from about 0.1% to about 0.5%, by weight of the hot melt composition.

[0089] Hot melt composition properties

[0090] The hot melt composition according to the present application can have at least one, and preferably all, of the following properties:

[0091] - a viscosity in the range of from about 2,000 mPa.s to about 15,000 mPa.s at 150°C, as measured according to the Viscosity Test Method as described herein;

[0092] - a storage modulus (G') of less than 9.5 MPa, preferably less than 7.5 MPa, most preferably below 5 MPa at 37°C, as measured in a cold to hot temperature ramp by the Oscillatory Rheology Test Method disclosed herein;

[0093] - a yield stress of less than 1.7 MPa at 37°C, as measured by the Tensile Test Method disclosed herein;

[0094] - a toughness of higher than 2 MJ / m2, preferably higher than 5 MJ / m2, as measured by the Tensile Test Method disclosed herein; 3 3

[0095] ​​- a cross-over temperature below 70°C, preferably below 65°C, measured according to the oscillatory rheology test method disclosed herein in a hot-to-cold temperature ramp.

[0096] Renewable materials

[0097] Any ingredient of the hot melt composition can be partially derived from renewable sources, in particular any one of the components or the hot melt composition as a whole can have a bio-based content of at least 50%. The "bio-based content" refers to the amount of carbon from renewable resources in a material as a percentage of the total organic carbon mass in the material, as determined by ASTM D6866-10 Method B.

[0098] The metallocene catalyzed polyolefins for use in the present application can be used with a significant (at least 50%) bio-based content. The Licocene grades from Clariant can be used in a renewable based version under the trade name Terra. Thus, the grade "Licocene PPA 330" can be used instead of the grade "Licocene PPA 330 Terra", or the grade "Licocene PP 1602" can be used instead of the grade "Licocene PP 1602 Terra".

[0099] Examples and data

[0100] Table 1 discloses the peak molecular weight (Mp) in g / mol of some commercially available polymers that can be used in the present application.

[0101] Table 1

[0102]

[0103]

[0104] 1) Correlated (not directly measured)

[0105] Table 2 discloses the enthalpy of crystallization in J / g of some commercially available polymers that can be used in the present application:

[0106] Table 2

[0107] Crystallization enthalpy (J / g) Licocene PP 1302 11.8 Licocene PP 1602 16.7 Licocene PP 2502 29.4 Licocene PP 3602 35.0 Licocene PPA 330 0

[0108] Table 3 shows exemplary formulations according to the present application (all ingredient values are expressed in weight percent). The open time of each exemplary composition can be evaluated using the Hot to Cold Cross-Over Temperature [°C] method, which measures the temperature at which the hot melt composition cures upon cooling. A lower cross-over temperature correlates with a longer open time for the hot melt adhesive, as for a given application temperature (typically 160°C), it takes a longer time for the adhesive to cool to reach the cross-over temperature at a given basis weight. The hot melt compositions of the present application are characterized by a longer open time, which is advantageous for the bonds in a diaper in which the compositions are preferably used. Those bonds are mainly the NW-film bonds in the chassis applications, which typically require a complex manufacturing process on the production line, which is accompanied by a longer distance between the adhesive application onto the first substrate and the additional cooling in combination with the second substrate or via vacuum (e.g. to temporarily fix the cut of the substrate with the adhesive before it is attached onto the second substrate). The inventors found that a propylene rich formulation and the absence of a wax or nucleating agent help to achieve the long open time required for the formulation. The inventors found that the cross-over temperature should be below 70°C, or preferably below 65°C. The toughness, the storage modulus (G') and the yield stress are also shown, the latter two being a measure of the stiffness of the hot melt composition.

[0109] Table 3

[0110]

[0111] Application examples

[0112] In the following examples, the adhesive was coated onto the first substrate with a 1 mm wide stripe / 1 mm gap slot between stripes at the specified basis weight (on the stripe) and combined with the second substrate. When only half of the area was covered, the average basis weight over the whole area was half of the basis weight on the stripe. The repeating pattern of stripes was applied over a lateral dimension of 120 mm.

[0113] Peel strength of the laminates was measured with a tensile tester in 180° peel mode at a crosshead speed of 305 mm / min. The peel strength is the average force per unit width required to separate two bonded substrates at a separation angle of 180 degrees. This force is averaged over the length of travel while the sample is under tension. The samples were equilibrated at 23 °C and 50% relative humidity for at least 1 hour prior to testing at the same temperature. The samples tested were essentially straight line shapes with a width of 1 inch (25.4 mm). The long axis of the sample was the cross direction and included a repeating pattern of adhesive strips and the short axis of the sample with the width of 25.4 mm was the machine direction. The axis of stretch was the long axis of the sample which corresponds to the cross direction of the laminate. The test was stopped after a 90 mm length of travel, the sample was still under tension (not completely separated). The force and extension data were collected automatically by TestWorks software available from MTS Systems Corporation of Eden Prairie, MN. Force and extension data were acquired at a rate of 200 Hz during the test.

[0114] In the examples of Table 4, the first substrate was a spunbond nonwoven with a basis weight of 22 gsm and the second substrate was a polyethylene film with a basis weight of 15 gsm.

[0115] Table 4

[0116] Adhesive Binder average basis weight [g / m 2 ]]]> Peel strength [N / inch] D3166 (comparative) 1.0 0.15 Example 4 (invention) 1.0 1.51 Example 4 (invention) 0.5 1.46 Example 4 (invention) 0.25 0.30 Example 5 (invention) 1.0 1.05 Example 5 (invention) 0.5 0.47 Example 6 (invention) 1.0 0.27 Example 7 (invention) 1.0 0.30 Example 7 (invention) 0.5 0.24

[0117] Due to their lower viscosity, Examples 6 and 7 can also be applied directly to more heat sensitive substrates such as polyethylene films, particularly by intermittent spray application (e.g. ). In intermittent spray application, larger droplets of adhesive that can form at the beginning of the intermittent spray interval can thermally damage the film if the adhesive is applied at too high a temperature. Thus, Examples 6 and 7 can be used in a variety of construction bonds, which enables the combination of several adhesive applications into one and reduces the number of adhesive tanks on a diaper production line. This additional benefit compensates for the relatively less strong performance increase compared to the reference compared to Examples 4 and 5. In addition, Examples 6 and 7 provide a performance increase of about 2-fold, which can translate into a reduction of adhesive usage of about 2-fold.

[0118] In the examples of Table 5, the first substrate was a landing zone laminate 44, and the second substrate was a 22 gsm spunbond nonwoven. The landing zone laminate (EBLV, available from 3M) was composed of an extruded film layer (extrudate) and carded staple fibers that had been thermally bonded to the extrudate. The total basis weight of the landing zone was 47.0 gsm, the fiber basis weight was 22.0 gsm, and the extrudate basis weight was 25.0 gsm. Adhesive was applied to the film side of the landing zone at an average basis weight of 10.6 gsm of adhesive. Since higher bond strength is required for this bond in a diaper, a higher basis weight adhesive was used in these examples. These samples were stored for 8 months at 23°C prior to measurement. Without wishing to be bound by theory, the inventors believe that the absence of mineral oil in the formulations of the present application reduces the degradation of the bond over time, which is typically observed for hot melt adhesives in nonwoven-film bonds as mineral oil diffuses from the adhesive into the adjacent film.

[0119] Table 5

[0120] Adhesive Peel strength [N / inch] D3166 (comparative) 3.51 Example 4 (invention) 14.04 Example 5 (invention) 13.12

[0121] General description of absorbent articles

[0122] As used herein, "absorbent article" refers to personal care products that are placed against or adjacent to the body of a wearer to absorb and contain various exudates discharged from the body. Absorbent articles include infant diapers, training pants, adult incontinence undergarments, feminine hygiene products, and the like. As used herein, the term "bodily fluid" or "body exudate" includes, but is not limited to, urine, blood, vaginal secretions, and fecal matter.

[0123] An exemplary absorbent article according to the present application in the form of an infant taped diaper 20 is shown in Figures 1-3 . Figure 1 A perspective view of an exemplary diaper as it would appear when worn by a wearer in a closed condition. The diaper 20 is shown for illustrative purposes only, as the present application can be used to make a wide variety of diapers or other absorbent articles, such as infant diaper pants, adult incontinence pants, or feminine hygiene pads. In the following description, the words "diaper" and "absorbent article" are used interchangeably. The drawings are used as an exemplification of one way to carry out the application and do not limit the scope of the claims.

[0124] The absorbent article includes a liquid permeable topsheet 24 on a wearer-facing surface thereof, a liquid impermeable backsheet 25 on a garment-facing surface thereof, and an absorbent core 28 between the topsheet and the backsheet (in Figure 2 and Figure 3(Seen in dashed lines). The topsheet typically forms most of the wearer-contact surface of the article and is the first layer in contact with bodily fluids. The topsheet is liquid-permeable, allowing liquids to easily penetrate its thickness. Any known topsheet can be used in this invention. The backsheet typically comprises a fluid-impermeable plastic film on which a backsheet pattern can be printed, and a low-basic-weight nonwoven outer cover adhesively bonded to the impermeable film to give the backsheet a better feel and appearance.

[0125] As used herein, “nonwoven fabric” refers to a manufactured sheet, web, or layer of fibers bonded together by friction and / or cohesion and / or adhesion, either oriented or randomly oriented, excluding paper and yarns or filaments bound together by weaving, braiding, tufting, stitching, or felting, whether or not they are additionally sewn. These fibers may be of natural or man-made origin and may be short fibers, continuous filaments, or fibers formed in situ. Commercially available fibers range in diameter from less than 0.001 mm to greater than 0.2 mm and come in several different forms: short fibers (called chopped yarns or short-staple fibers), continuous monofilaments (filaments or monofilaments), untwisted continuous filament bundles (tows), and twisted continuous filament bundles (yarns). Nonwoven fabrics can be formed by a variety of methods such as meltblowing, spunbonding, solution spinning, electrospinning, and carding. The basis weight of nonwoven fabrics is typically expressed in grams per square meter (gsm or g / m²). 2 () indicates. For example, a typical nonwoven fabric that can be used in absorbent articles has a basis weight in the range of about 5 gsm to about 50 gsm, or at most about 40 gsm.

[0126] Absorbent articles may also typically include a fluid collection layer and / or fluid distribution layer between the top sheet and the absorbent core (not shown in the figures for simplicity but present in most diapers), as well as an outer barrier band 32 and an inner barrier band 34, as is known in the art. If it is desired to improve the performance of the article, the absorbent article may also include other common components such as lateral barrier bands, front and / or rear elastic waistbands, detergent application on the top sheet, longitudinally extending channels in the core and / or distribution layer, wetting indicator markings, etc. All of these components have been well described and illustrated in the art. To name just a few, more detailed disclosures of examples of such components are provided, for instance, in WO201493323, WO2015 / 183669 (both by Bianchi et al.), WO2015 / 031225 (by Roe et al.), or WO2016 / 133712 (by Ehrnsperger et al.).

[0127] Absorbent articles generally include a front edge 10, a back edge 12, and two longitudinally extending side (lateral) edges 13, 14. The front edge 10 is the edge of the article intended to be placed toward the front of the user when worn, and the back edge 12 is the opposite edge, and together form the waist opening of the diaper. The lateral edges 13, 14 form two leg openings, respectively. The topsheet 24, backsheet 25, absorbent core 28, and other article components can be assembled in a variety of well-known configurations, particularly by gluing, melting, and / or pressure bonding. The absorbent articles of the present invention can include any typical layers and components for absorbent articles of the diaper type, and the layers and components are not necessarily shown in the simplified Figures 1-3 diagrams. Multiple absorbent articles can be packaged together in a package.

[0128] General description of absorbent core 28

[0129] "Absorbent core" means an absorbent structure disposed between the topsheet and the backsheet for absorbing and containing liquid such as urine received by the absorbent article. The absorbent core includes absorbent material generally enclosed within, or interposed between, core wraps. The core wraps can be a single material folded and attached to itself, or it can include separate top and bottom layers that are bonded together. The absorbent material generally includes superabsorbent particles, optionally mixed with cellulosic fibers. As used herein, "absorbent core" does not include any acquisition system, topsheet, or backsheet of the absorbent article.

[0130] Absorbent core 28 is a component of the absorbent article having the maximum absorbent capacity. An exemplary absorbent core 28 is shown individually in Figures 4-6 , in a dry state (before use). The absorbent core can generally have a generally rectangular shape, as defined by longitudinal edges 284, 286 and transverse front and back edges 280 and 282. The absorbent core 28 includes absorbent material 60 deposited in the form of a layer having a generally rectangular profile, as shown in Figure 4 . This absorbent core shown is of course not limiting the scope of the invention, as the invention is applicable to a wide variety of absorbent cores. It is common to have the layer of absorbent material 60 including a non-rectangular profile ("shaped" core), particularly the absorbent material layer can define a tapering (or "dog bone" shape) along its width toward the central region of the core. In this way, the absorbent material deposition region can have a relatively narrow width in the region of the core intended to be placed in the crotch region of the absorbent article. This can provide, for example, better wearing comfort. Other shapes such as "T" or "Y" or "hourglass" shapes can also be used for the region of absorbent material.

[0131] The absorbent material 60 can be any conventional absorbent material known in the art. For example, the absorbent material can include a blend of cellulosic fibers and superabsorbent particles ("SAP"), typically in a percentage of SAP in the range of about 50% to about 75% by weight of the absorbent material. The absorbent material can also be free of cellulosic fibers, as is known in so-called airfelt-free cores, in which the absorbent material consists of SAP.

[0132] "Superabsorbent polymer" or "SAP" means herein absorbent materials, typically crosslinked polymeric materials, which are capable of absorbing at least 10 times their own weight of aqueous 0.9% saline solution, measured using the Centrifuge Retention Capacity (CRC) test (EDANA method WSP 241.2.R3 (12)). SAP can in particular have a CRC value of at least 20 g / g, in particular 20 g / g to 40 g / g. As used herein, "superabsorbent polymer particles" means superabsorbent polymer materials in the form of particles such that they are flowable in the dry state.

[0133] Various absorbent core designs comprising high amounts of SAP have been proposed in the past, see for example US 5,599,335 (Goldman), EP 1,447,066 (Busam), WO 95 / 11652 (Tanzer), US 2008 / 0312622 Al (Hundorf), WO 2012 / 052172 (Van Malderen). In particular, the SAP printing techniques as disclosed in US 2006 / 024433 (Blessing), US 2008 / 0312617 and US 2010 / 0051166 Al (both to Hundorf et al.) can be used. However, the present application is not limited to a particular type of absorbent core. The absorbent core can also comprise one or more glues, such as a secondary glue applied between the inner surface of one (or both) of the core wrap layers and the absorbent material, to reduce SAP leakage outside the core wrap. A network of microfiber adhesive can also be used in airfelt-free cores, as described in the above Hundorf references. For simplicity, these glues are not shown in the drawings.

[0134] The absorbent material can be deposited in the form of a continuous layer within a core enclosure. The absorbent material can also be present discontinuously, for example, as individual pits or strips of absorbent material encapsulated within a core enclosure and separated from each other by bonding regions without material. Continuous layers of absorbent material, particularly SAP, can also be obtained by combining two absorbent layers with a pattern of matching discontinuous absorbent material application, wherein the resulting layers are distributed substantially continuously over regions of the absorbent particle polymer material. As taught, for example, in US2008 / 312,622A1 (Hundorf), each absorbent material layer can therefore include a pattern having absorbent material landing regions and bonding regions without absorbent material, wherein the absorbent material landing regions of the first layer substantially correspond to the bonding regions without absorbent material of the second layer, and vice versa.

[0135] The basis weight (amount deposited per unit surface area) of the absorbent material can also be varied, particularly in the longitudinal direction (e.g., Figure 5 (Illustrated schematically) However, the absorbent material can also be irregularly distributed in the transverse direction or in both directions of the core to provide greater absorbency toward the center and middle of the core. The absorbent core may also include longitudinally extending channels that are substantially free of absorbent material within areas of absorbent material. The core wrapping can be bonded through these material-free areas. Exemplary disclosures of such channels in cores without breathable felt can be found in WO2012 / 170778 (Rosati et al.) and US2012 / 0312491 (Jackels). Channels can, of course, also be formed in absorbent cores comprising cellulose fibers.

[0136] Core wrap

[0137] The function of the core wrapper is to contain absorbent material. Different core wrapper constructions can be used. A typical core wrapper construction comprises two nonwoven substrates 16, 16', which are attached to each other and form the top layer 16 and bottom layer 16' of the core wrapper, respectively. These two layers are typically attached to each other along at least a portion of the periphery of the absorbent core to form a seal. Typically, neither the first nor the second substrate needs to be molded, allowing them to be rectangularly cut for ease of fabrication, but other shapes are not excluded. The term "seal" should be interpreted broadly. A seal does not need to be continuous along the entire periphery of the core wrapper, but can be discontinuous along part or all of it, such as being formed by a series of sealing points spaced apart along a line. Typically, the seal can be formed by adhesive and / or thermal bonding.

[0138] The core wrap shown in the drawings comprises a top layer 16 which is wider than the bottom layer 16' such that two flaps of the top layer can be folded over the bottom layer along the longitudinal edges 284, 286 of the core to which they are attached, typically forming longitudinal seals 284', 286' by adhesive. The front edge 280 and the back edge 282 can also be sealed, for example by sandwich seals 280', 282'. Such transverse seals can for example be made from adhesive strips which are applied in the machine direction by slot die technology, as is known in the art. Alternatively, the transverse edges 280, 282 can be left open without seals. For example, there can be sufficient core wrap material between the edges of the core and the absorbent material 60 to provide a buffer zone at these extremities.

[0139] The present invention is applicable to any of these core wrap seals as well as the core channel bonds (to be discussed further below). Alternatively, the core wrap can be made from a single nonwoven which has been folded over itself around the absorbent material layer 60 and bonded to itself along a single longitudinal seal rather than two longitudinal seals 284' and 286' as shown in the drawings. The present invention is also applicable to such core wraps.

[0140] The top layer 16 and the bottom layer 16' can be made from the same base substrate material which has been treated differently. Such nonwoven substrates can have a basis weight in the range of about 8 gsm to about 12 gsm. The top layer can typically be a nonwoven layer made from synthetic fibers which have been treated with a surfactant to increase their hydrophilicity. The core wraps can in particular each comprise or be formed from a nonwoven web such as a carded nonwoven fabric, a spunbond nonwoven fabric ("S") or a meltblown nonwoven fabric ("M"), as well as multiple layers of any of these. For example, spunbond / meltblown laminates (spunmelt) polypropylene nonwovens are commonly used and are particularly suitable, especially those having a multi-layer SMS, or SMMS, or SSMMS structure. Examples are disclosed in US 7,744,576, US 2011 / 0268932 Al, US 2011 / 0319848 Al or US 2011 / 0250413 Al. Typical materials for making the synthetic fibers are PE (polyethylene), PET (polyethylene terephthalate), and in particular PP (polypropylene).

[0141] Spunbond (also known as spunlaid) nonwovens are produced in a continuous process. Fibers are spun through multiple small orifices in a spinneret to form fibers or filaments that are then dispersed directly into a fiber web by a deflector or can be guided by an air stream onto a moving porous surface such as a wire mesh conveyor. Meltblown nonwovens are produced by extruding molten polymer fibers through a spinneret or die consisting of up to 40 holes per inch to form long, thin fibers that are stretched and cooled by passing hot air over the fibers as they fall from the die. The diameter of the fibers is significantly reduced by the hot air, which also breaks the continuous filaments into microfibers of varying length to diameter ratios. Microfine fibers (typically polypropylene) differ from other extrudates, especially spunbond fibers, because they have low inherent strength but are much smaller in size, providing key properties.

[0142] Spunbond processes can be combined with meltblown processes to form multilayer webs with S (spunbond) and M (meltblown) layers, particularly SM, SMS, or SMMS webs, which are strong and provide the inherent benefits of fine denier fibers. Nonwovens can be consolidated using known techniques, typically thermal point bonding. In thermal point bonding, heat is applied locally on individual areas of the nonwoven material to locally melt the fibers and fuse the fibers together. Fused bonding patterns are disclosed, for example, in US 2011 / 0250413 (Hu et al.) and US 2014 / 0072,767 Al (Klaska et al.). The resulting webs are typically collected into rolls at the supplier and subsequently converted into finished products.

[0143] Core channel

[0144] The absorbent core 28 can comprise one or more channels 26, in particular at least one channel on each side of the longitudinal centerline of the core, which can or can not be connected and which exist within the layer of absorbent material. In particular, the channels can be areas substantially free of absorbent material, in particular areas completely free of absorbent material (ignoring incidental trace amounts of absorbent material resulting from non-autonomous contamination of the channels due to the high speed of the manufacturing process).

[0145] The channels 26 can include channel bonds 27 between the topside 16 of the core wrap and the bottom side 16' of the core wrap. The bonds 27 provide structural integrity to the channels in the dry state and in the wet state. Any known bonding technique known in the art can be used to provide the bonds, particularly a technique selected from adhesive bonding, thermal bonding, mechanical bonding, ultrasonic bonding, or any combination thereof. Adhesive can be applied, for example, on the inside of the topside and / or the inside of the bottom side of the core wrap in the channel areas, typically by slot die application or any other method, followed by the application of pressure in the channel areas to provide good adhesive bonds in these areas. Exemplary patent disclosures of such adhesive bonding processes can be found in WO 2012 / 170,798 Al (Jackels et al.), EP 2,905,000 (Jackels et al.), and EP 2,905,001 (Armstrong-Ostle et al.) for airfelt or airfelt-free absorbent cores.

[0146] In addition to the core perimeter bonds 280'-286', or alternatively, the hot melt composition of the present application can be used to make these channel bonds 27. Typically, the bonds 27 can generally have the same profile and shape as the channel areas 26 in which they are housed, but can be slightly smaller to allow for a safety margin (e.g., differ by a few mm) as some misregistration can occur during high speed processes. Desirably, the channel bonds 27 can be made more efficiently and be more robust if they are disposed in macro areas that do not carry absorbent material (except for incidental contamination, of course) as compared to bonds disposed in areas that contain non-negligible amounts of absorbent material.

[0147] Backsheet

[0148] The backsheet 25 is a liquid impermeable layer that generally forms the garment-facing side of the absorbent article. The backsheet 25 prevents or at least inhibits body exudates absorbed and contained by the absorbent core 28 from soiling articles such as bed sheets, undergarments, and / or garments. The backsheet typically includes a liquid impermeable, or at least substantially liquid impermeable, layer, typically a plastic film, having a thickness of about 0.01 mm to about 0.05 mm. Suitable backsheet materials also include breathable materials that permit vapors to escape from the absorbent article, while still preventing or at least inhibiting body exudates from passing through the backsheet.

[0149] The backsheet 25 is typically a laminate that includes a plastic film and further includes a nonwoven outer cover on the outside thereof for improving the overall feel of the backsheet. The outer cover nonwoven, sometimes referred to as the backsheet nonwoven, is joined to and covers the backsheet film. Thus, the outer cover material generally forms at least a portion of the garment-facing surface of the absorbent article 20. The outer cover material can include a bond pattern, apertures, and / or three-dimensional features.

[0150] Land zone

[0151] Referring to Figure 1 and Figure 2 An absorbent article 20 in the form of a taped diaper can have a discrete landing zone 44 on the garment-facing side of the article, which is typically disposed proximate the front edge 10 of the article 20. The landing zone 44 is configured to receive fasteners 42 and can include, for example, a plurality of loops configured to engage a plurality of hooks on the fasteners 46, or vice versa.

[0152] The landing zone 44 typically includes one or more discrete nonwoven materials that are attached to a portion of the outer cover material 40 in the front waist region 12. The present disclosure is particularly applicable to the area of adhesion between such landing zones and back sheets.

[0153] Pant diaper

[0154] An absorbent article can also be in the form of a pant having permanent or refastenable side seams, which are not shown herein, but to which the present disclosure can also be applicable. Pant-type articles including refastenable seams are disclosed, for example, in US 2014 / 0,005,020 and US 9,421,137. A typical pant-type article includes a chassis, sometimes referred to as a central chassis or central panel, including a topsheet, a backsheet, and an absorbent core as can be disclosed herein, and a front belt defining a front waist region and a back belt defining a back waist region. The chassis can be joined to the wearer-facing surface of the front and back belts, or to the garment-facing surface of the belts. The side edges of the front belt can be joined to the side edges of the back belt to form two side seams. The side seams can be any suitable seams known to those skilled in the art, such as, for example, abutted seams or overlapping seams. When the side seams are permanently formed or refastenably closed, the absorbent article in the form of a pant has two leg openings and a waist opening periphery. The side seams can be permanently joined using, for example, adhesives or bonds, or can be refastenably closed using, for example, hook-and-loop fasteners.

[0155] Alternatively, discrete side panels can be attached to the side edges of the chassis instead of attaching a belt to the chassis to form a pant. Suitable forms of pants including discrete side panels are disclosed in, for example, US 6,645,190; US 8,747,379; US 8,372,052; US 8,361,048; US 6,761,711; US 6,817,994; US 8,007,485; US 7,862,550; US 6,969,377; US 7,497,851; US 6,849,067; US 6,893,426; US 6,953,452; US 6,840,928; US 8,579,876; US 7,682,349; US 7,156,833; and US 7,201,744.

[0156] Bonding area

[0157] The absorbent article comprises at least a bonding area between a first substrate and a second substrate provided by the hot melt composition disclosed herein. The hot melt composition according to the present application is disposed within the bonding area. The bonding area can be continuous or discontinuous. The bonding area can be between a) a first nonwoven and a second nonwoven (nonwoven-nonwoven bonding) or b) a nonwoven and a plastic film (nonwoven-film bonding). The hot melt composition of the present application is particularly suitable for nonwoven-film bonds, but can also be used for nonwoven-nonwoven bonds.

[0158] The hot melt composition is applied in the molten state to either the first substrate or the second substrate and then the hot melt composition is brought into contact with the other substrate, preferably at least some pressure is applied between the two substrates before the hot melt composition cures to ensure that bonding occurs. The hot melt composition can be applied to the nonwoven for nonwoven-film applications, or to the film, or to both substrates.

[0159] The hot melt composition of the present application is particularly suitable for bonding films and nonwovens. A typical absorbent article comprises a backsheet film. Thus, the hot melt adhesive of the present application can be used to bond the backsheet film to any adjacent nonwoven in the article, for example to bond the backsheet film to the front ear panel 40 in the taped diaper 20, and / or to bond the backsheet film to the backsheet nonwoven outer cover, and / or to bond the backsheet film to the bottom layer 16' of the core wrap of the absorbent core, and / or to bond the backsheet film to the top sheet nonwoven on the side edges of the article. Other film-nonwoven applications can be, for example, the film component of the landing zone laminate 44 to the backsheet nonwoven outer cover 25.

[0160] The hot melt composition can be applied by any known method, which can be contact (such as slot, bead, adhesive coating as disclosed in WO2014 / 085,063A1, etc.) or non-contact (spray in spiral or random pattern, including intermittent spray application, etc.). The hot melt composition can be applied by any commercial applicator, such as Nordson’s (spiral), or applicator system. The hot melt composition can be applied on the first substrate or the second substrate or both substrates in a contact method (e.g. slot coating) or non-contact method preferably at a line speed greater than 2 m / s, in particular greater than 3 m / s, or even greater than 4 m / s.

[0161] The hot melt composition can typically be applied between the two substrates in the area to be bonded in a basis weight ranging from about 5 gsm to about 30 gsm, or from about 8 gsm to about 25 gsm. The hot melt composition can also be used to make nonwoven-nonwoven bonds, such as channel bonds 27 between the top side and the bottom side of an absorbent core, topsheet to acquisition layer bonds, or acquisition layer to core wrap bonds, or any other bond not explicitly mentioned herein.

[0162] The hot melt adhesive composition can keep the first and second substrates bonded together within its own bonding area. Alternatively, the hot melt composition can be supplemented by another bonding means such as mechanical bonding or fusion bonding.

[0163] Test methods

[0164] Peak molecular weight (Mp) measurement method

[0165] Gel permeation chromatography (GPC) method is used to determine peak molecular weight. GPC is a well-known method in which polymers are separated according to molecular size, with the largest molecules eluting first. Peak molecular weight referred to herein can be determined using gel permeation chromatography (GPC) using polystyrene calibration standards, such as according to ASTM D5296. The molecular weight of any polymer or unknown polymer measured using a GPC so calibrated is the styrene equivalent molecular weight, which is defined herein as the “peak molecular weight”. Suitable solvents and temperatures are used with the GPC in order to achieve sufficient molecular weight separation and resolution.

[0166] Weight average molecular weight (Mw)

[0167] Weight average molecular weight is measured according to DIN 55672.

[0168] Crystallization enthalpy test method

[0169] The crystallization enthalpy parameter of the hot melt adhesive composition is determined using the Crystallization Enthalpy Test Method, which consists of: performing ASTM D3418-15 following the additional guidance below. One or more samples are extracted from the as-molded or as- pelletized raw material adhesive composition. If no raw material is available, one or more adhesive samples are extracted from the bond of interest in an absorbent article using techniques known to those skilled in the art. Dry nitrogen gas is used as the purge gas in the differential scanning calorimeter (DSC). The rate of temperature increase in the DSC is 10 °C / min, and the rate of temperature decrease in the DSC is 1 °C / min. The mass-normalized crystallization enthalpy is calculated based on the curve corresponding to the decreasing temperature (at 1 °C / min) as specified in Section 11.4, and reported as the “crystallization enthalpy” in Joules per gram (J / g) to the nearest 0.1 J / g.

[0170] Viscosity test method

[0171] The Viscosity Test Method includes performing a shear flow ramp on a rotational rheometer (e.g., ARES-G2, TA Instruments, Newark, DE, USA, or equivalent). The rheometer is operated in a cone-and-plate configuration with a stainless steel cone having a diameter of 40 mm and a cone angle of 0.04 rad as the upper tool and a stainless steel plate having a diameter of 40 mm as the lower tool. In addition, the rheometer needs to be capable of controlling the sample temperature with an accuracy equal to or better than 0.5 °C in the range of at least 20 °C to 200 °C.

[0172] The method uses a measurement gap of 49 pm. To compensate for thermal expansion of the tools, the actual gap is mapped. For any temperature setpoint of interest, the following procedure is used (typical temperature setpoints of interest in this method include, but are not limited to, 150 °C, 170 °C, and 190 °C). The rheometer is heated to the desired measurement temperature. After a 10 minute equilibration time, the actual gap is determined by the “zero gap” procedure. Zeroing the sample gap requires lowering the upper tool until it contacts the lower tool, and at least a greater than 2 N axial force is detected by the rheometer. At this point, the gap value is set to zero.

[0173] For viscosity measurements at any temperature setpoint of interest, the compensation for thermal expansion is first determined as described above. The polymer composition is introduced into the rheometer, the gap is set to 74 pm, the excess protruding sample is trimmed, and then the gap is set to 49 pm. The sample is preheated at the temperature setpoint of interest for 2 minutes. The shear stress is then recorded at 11 different shear rates that span a decade from 1 s -1 to 10 s -1 in a logarithmic manner, i.e., at 1.00 s -1 , 1.26 s -1 , 1.58 s -12.00s -1 2.51s -1 3.16s -1 3.98s -1 5.01s -1 6.31s -1 7.94s -1 and 10.00s -1 At the shear rate.

[0174] Analysis

[0175] The data are plotted log-log, with shear rate on the x-axis and shear stress on the y-axis (logarithmic scale). A linear fit is then performed. Starting from the high shear rate end of the range, at least six, and as many as possible, consecutive points are included to obtain an R² value of 0.9 or greater. If an R² value of 0.9 cannot be achieved with only six points, a fit corresponding to the six points at the highest shear rate is accepted. The slope value is defined as a viscosity parameter and reported in millipascal-seconds (mPa·s), accurate to hundreds of mPa·s.

[0176] Oscillatory rheometry test method

[0177] Oscillatory rheological testing methods are used to measure the storage modulus G' and loss modulus G' of polymer compositions. Controlled strain rotational rheometers (such as the Discovery HR-3, TA Instruments, Newcastle, Delaware, USA, or equivalents) are capable of controlling the sample temperature within a range of at least -10°C to 150°C with an accuracy equal to or greater than 0.5°C (using a combination of a Peltier cooler and a resistance heater). The rheometer operates in a parallel plate configuration with a 20mm stainless steel parallel plate tool.

[0178] The method initially used a parallel plate gap of 1000 μm. To compensate for the thermal expansion of the tool, the gap was set to 1000 μm, and a mapping was performed on the actual plate gap (measured using a suitable standard test fluid) as a function of temperature in the range of -10 °C to 150 °C. This mapping was then used throughout the determination of the storage modulus and loss modulus parameters.

[0179] The rheometer is heated to 150 °C, the polymer composition is introduced into the rheometer, the gap is set to 1050 pm, the excess protruding sample is trimmed and then the gap is set to 1000 pm. The axial force control of the rheometer is set to 0 N and kept within a force of ±0.1 N during the experiment, whereby the thermal expansion / contraction of the sample itself is compensated by adjusting the gap in addition to the compensation of the tool described above, in order to avoid overfilling or underfilling. Then the rheometer is cooled to 130 °C, at which point the temperature is decreased from 130 °C to -10 °C at a constant rate of 2 °C / min (hot to cold temperature ramp), the measurement is started. The strain amplitude applied is 0.1 % and the oscillation frequency is 1 Hz (i.e. one cycle per second). The resulting oscillatory stress is recorded.

[0180] After this step, the sample temperature is set to 23 °C (the temperature is increased to this set value at a rate of 10 °C / min) and the sample is left to stand at 23 °C for 4.0 hours. At the end of this phase, the temperature is set to -10 °C (the temperature is decreased to this set point at a rate of 10 °C / min), the sample is equilibrated at -10 °C for 300 seconds and a second oscillatory rheological measurement (0.1 % strain, oscillation frequency of 1 Hz) is performed while the temperature is increased to 130 °C at a constant rate of 2 °C / min (cold to hot temperature ramp). The strain amplitude applied is 0.1 % and the oscillation frequency is 1 Hz (i.e. one cycle per second). The resulting oscillatory stress is recorded.

[0181] From the beginning of the first temperature decrease ramp (hot to cold), the storage modulus G' and the loss modulus G" are calculated and recorded from 130 °C to -10 °C in steps of 0.5 °C or smaller steps. These values are reported in Pascals (Pa) to the nearest 1 Pa. Both the storage modulus G' and the loss modulus G" are plotted on a logarithmic scale y-axis against a linear scale temperature x-axis. The individual values of the temperature steps are connected to obtain the storage modulus curve G' and the loss modulus curve G' versus temperature. The cross-over temperature is the temperature at which the loss modulus G" [Pa] and the storage modulus G' [Pa] become equal and thus the curves cross. In case more than one cross-over temperature can be determined in the descending temperature ramp (hot to cold), only the highest cross-over temperature is reported. The cross-over is reported to the nearest 1 °C.

[0182] From the beginning of the second temperature increase ramp (cold to hot), the storage modulus G' is calculated and recorded at 37 °C and these values are reported as "storage modulus at 37 °C" in Mega Pascals (MPa) to the nearest 0.1 MPa.

[0183] Tensile test method

[0184] The tensile test method is used to determine the yield stress and tenacity of a sample of a polymer composition. A thin film sample formed from the polymer composition is analyzed with a rotational rheometer equipped with a specialized fixture with counter-rotating cylinders. The stress associated with the applied tensile strain is measured and recorded.

[0185] Instrument settings

[0186] A rotational rheometer (ARES G2, TA Instruments, New Castle, DE, USA, or equivalent) is equipped with a fixture having counter-rotating cylindrical rollers specifically designed to interrogate the tensile deformation of a film. An example of a suitable fixture is a tensile viscosity fixture or EVF (EVF, TA Instruments, or equivalent). The rheometer is also equipped with a forced convection oven FCO (FCO, TA Instruments, or equivalent) and a cooling system (ACS 2, TA Instruments, or equivalent) capable of controlling the temperature from at least -50 °C to 250 °C within a tolerance of 0.5 °C.

[0187] Sample preparation

[0188] Approximately 6 g ± 2 g of the polymer composition is placed in a circular polytetrafluoroethylene (PTFE) bowl with a flat bottom (60 mm ± 2 mm diameter) and introduced into a vacuum oven held at 170 °C. After 15 minutes at ambient pressure, the pressure is reduced to 10 mbar and the polymer composition is then held at 170 °C and 10 mbar for 45 minutes to remove air bubbles in the polymer composition. If 170 °C is insufficient to melt the polymer composition, a temperature of 30 °C ± 10 °C above the melting temperature of the polymer material composition is used. The polymer composition is removed from the vacuum oven and allowed to cool to ambient laboratory conditions (23 °C ± 2 °C) for 90 minutes ± 30 minutes, at which time the polymer composition is removed from the PTFE bowl and placed between 2 sheets of siliconized paper (such as product number 114918, Mondi Group, Hilm, Austria, or equivalent). A metal shim with a thickness of 500 μm ± 30 μm is used as a spacer in a hot press, and a film thickness of 500 μm is obtained when pressing with the hot press at 90 °C for 60 seconds at a pressure sufficient to form a polymer film. If 90 °C is insufficient to press a uniform flat film, a temperature of approximately 10 °C ± 5 °C below the melting point of the sample material composition is used such that the sample material composition is in a semi-solid state. The film is stored in a laboratory at 23 °C ± 2 °C for at least 120 hours prior to testing. Individual measurement samples are punched from the film with a sample cutter, resulting in a final sample size of 20.0 mm x 10.0 mm x 500 μm.

[0189] Measurement

[0190] To fix the sample membrane to the cylinder of the EVF, the cylinder was heated to 50°C for 90 s ± 30 s in the forced convection oven of the rheometer. After opening the oven, the sample of the polymer composition was briefly pressed onto the cylinder of the EVF to fix it to the cylinder surface. The sample was positioned with its length perpendicular to the axis of rotation of the cylinder. For very rigid polymer compositions that do not adhere to the cylinder surface, the EVF was heated to 80°C for 90 s ± 30 s in the forced convection oven of the rheometer. Then, small droplets (0.03 g ± 0.01 g) of auxiliary hot melt adhesive were applied to each cylinder. The auxiliary adhesive used should exhibit high stiffness (G' greater than 10 MPa at 23°C and 1 Hz) to avoid interfering with the measurement. The sample of the polymer composition was rapidly pressed onto the auxiliary adhesive on the EVF cylinder to fix it to the cylinder surface. The sample was positioned perpendicular to the axis of rotation of the cylinder.

[0191] The sample mounted on the EVF was then placed in the forced convection oven of the rheometer for thermal conditioning and held at 37℃±0.5℃ for 300s±10s. After this period, the sample underwent mechanical conditioning. For mechanical conditioning, the torque transducer was zeroed, and the sample was moved at a speed of 0.001s... –1 The pre-stretch rate is set at 0.30 s, and then relaxed for 60 s (in this method, all strains are expressed as Hencky strain (also known as "true strain" or "logarithmic strain").

[0192] Measurements were taken in an FCO oven at 37℃ ± 0.5℃. The strain rate was measured over a tensile period of 1 s. –1 The strain at maximum tensile strength is 4.0. After measurement, the sample is checked for breakage. If it breaks, the location of the break is recorded. If the breakage is approximately between the two cylinders of the EVF, the collected data is considered acceptable. Otherwise, if the polymer film breaks at or near the rotating cylinder, the results are discarded, and the measurement is repeated on a duplicate sample.

[0193] Analysis

[0194] For tensile stress calculations, a constant volume is assumed. Tensile stress (in megapascals or MPa) is calculated against Henki strain data based on raw torque-to-angular displacement data recorded by a rheometer. The data is plotted in a semi-logarithmic manner, with the x-axis representing Henki strain (linear scale) and the y-axis representing tensile stress (logarithmic scale). The linear range is sought within this plot. If a linear range for strain above 0.3 can be identified, and this range can be correlated with R... 2If a positive slope fit with a value of 0.98 or greater, then the value of the fit line at a Hencky strain of zero (i.e., the y-intercept) is defined as the yield stress, reported in MPa to the nearest tenth of an MPa. Otherwise, the maximum value of tensile stress recorded during the measurement is reported as the yield stress, again reported in MPa to the nearest tenth of an MPa.

[0195] The tensile stress (MPa) versus Hencky strain data calculated above is again plotted, but this time linearly, with the abscissa (linear axis) as Hencky strain and the ordinate (linear axis) as tensile stress. The integral of the tensile stress with respect to strain (i.e., the area under the tensile stress curve as a function of strain) is calculated from zero strain to the strain at which the sample ruptures (or, in the case of no rupture during the measurement, to a strain of 4.0), and is reported as the "toughness" in mega Joules per cubic meter or MJ / m 3

[0196] The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For instance, a dimension disclosed as "40 mm" is intended to mean "about 40 mm."​

Claims

1. A hot-melt composition, said hot-melt composition comprising: -30% to 60% of low molecular weight metallocene-catalyzed propylene-based polymers with peak molecular weights below 130,000 g / mol, wherein the peak molecular weight is measured according to the peak molecular weight (Mp) measurement method disclosed herein; -2% to 15% of high molecular weight metallocene-catalyzed propylene-based polyolefins with peak molecular weights of 130,000 g / mol to 700,000 g / mol; -5% to 25% of amorphous polyolefins with a crystallization enthalpy of less than 5 J / g, wherein the crystallization enthalpy is measured according to the crystallization enthalpy test method described herein; and -30% to 60% tackifier.

2. The hot-melt composition according to claim 1, wherein the low molecular weight metallocene-catalyzed propylene-based polymer is any one of a propylene-ethylene copolymer or a propylene homopolymer or a mixture thereof.

3. The hot-melt composition according to claim 1 or claim 2, wherein the low molecular weight metallocene-catalyzed propylene-based polymer comprises: - A first low molecular weight metallocene-catalyzed propylene-ethylene copolymer with a crystallization enthalpy below 20 J / g; and - A second low molecular weight metallocene-catalyzed propylene-ethylene copolymer with a crystallization enthalpy higher than 20 J / g.

4. The hot-melt composition of claim 3, wherein the low molecular weight metallocene-catalyzed propylene-based polymer comprises: - A first low molecular weight metallocene-catalyzed propylene-ethylene copolymer with a crystallization enthalpy in the range of 5 J / g to 15 J / g; and - A second low molecular weight metallocene-catalyzed propylene-ethylene copolymer with a crystallization enthalpy in the range of 25 J / g to 45 J / g.

5. The hot-melt composition according to claim 1 or claim 2, wherein the hot-melt composition comprises a low molecular weight metallocene-catalyzed propylene-based polymer with a crystallization enthalpy in the range of 20 J / g to 30 J / g and a peak molecular weight between 25,000 g / mol and 35,000 g / mol.

6. The hot melt composition of claim 5, wherein the hot melt composition does not contain another low molecular weight metallocene-catalyzed propylene-based polymer.

7. The hot-melt composition according to claim 1 or claim 2, wherein the high molecular weight metallocene-catalyzed propylene-based polyolefin is a propylene-ethylene copolymer containing more than 80% by weight of polypropylene units.

8. The hot-melt composition according to claim 1 or claim 2, wherein the high molecular weight metallocene-catalyzed propylene-based polyolefin has a peak molecular weight in the range of 130,000 g / mol to 410,000 g / mol.

9. The hot-melt composition of claim 8, wherein the high molecular weight metallocene-catalyzed propylene-based polyolefin has a peak molecular weight in the range of 150,000 g / mol to 360,000 g / mol.

10. The hot-melt composition according to claim 1 or claim 2, wherein the amorphous polyolefin is a metallocene-catalyzed propylene-based polymer; wherein the amorphous polyolefin has a weight-average molecular weight Mw of less than 10,000 g / mol as measured by DIN 55672.

11. The hot-melt composition according to claim 10, wherein the amorphous polyolefin has a weight-average molecular weight Mw of 1,000 g / mol to 9,000 g / mol as measured by DIN 55672, and optionally has a viscosity of less than 500 mPa·s at 170°C as measured by the viscosity test method described herein, and has no melting point detectable by DSC.

12. The hot melt composition according to claim 1 or claim 2, wherein the hot melt composition comprises less than 10% by weight of mineral oil.

13. The hot melt composition according to claim 1 or claim 2, wherein the viscosity of the hot melt composition at 150°C, as measured by the viscosity testing method described herein, is in the range of 2,000 mPa·s to 15,000 mPa·s.

14. The hot-melt composition according to claim 1 or claim 2, wherein the composition has all of the following properties: - The storage modulus (G') is less than 9.5 MPa at 37 °C, measured in a cold-to-hot temperature ramp using the oscillatory rheological testing method disclosed herein; and - Yield stress less than 1.7 MPa at 37°C, measured by the tensile testing method disclosed herein; and -Measured using the tensile testing method disclosed in this paper, values ​​higher than 2 MJ / m 3 Its resilience; and -Measured at cross temperatures below 70°C in a hot-to-cold temperature ramp using the oscillatory rheological testing method disclosed herein.

15. An absorbent article comprising a first substrate and a second substrate, wherein the first substrate and the second substrate are at least partially bonded by a hot melt composition according to any one of claims 1-14, and wherein a) the first substrate is a first nonwoven fabric and the second substrate is a second nonwoven fabric, or b) the first substrate is a nonwoven fabric and the second substrate is a plastic film.

16. A method for bonding a first substrate to a second substrate, the method comprising the steps of: The hot melt composition according to any one of claims 1 to 14 is applied at least to the first substrate or the second substrate using a contact applicator or a spray applicator, and then the two substrates are optionally joined together under additional pressure before the hot melt composition solidifies to form an adhesive portion between the two substrates.

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