Nonwoven fabric and method for manufacturing a nonwoven fabric

Abstract

A nonwoven fabric includes continuous filaments, wherein the filaments are multi-component filaments and include at least one first polypropylene component containing a base-polypropylene and at least one second polypropylene component containing a base-polypropylene. The melting point difference between the base-polypropylene of the first polypropylene component and the base-polypropylene of the second polypropylene component is less than 5° C. The base-polypropylene of the first polypropylene component and the base-polypropylene of the second polypropylene component were polymerized with a catalyst of the same catalyst class.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] Applicant claims priority under 35 U.S.C. § 119 of German Application No. 10 2024 133 513.0 filed Nov. 15, 2024, the disclosure of which is incorporated by reference.BACKGROUND OF THE INVENTION1. Field of the Invention

[0002] The invention relates to a nonwoven fabric comprising continuous filaments, wherein the filaments are multi-component filaments, in particular bicomponent filaments, and comprise at least one first polypropylene component containing a base-polypropylene and at least one second polypropylene component containing a base-polypropylene. The invention also relates to a method for manufacturing such a nonwoven fabric. According to the invention, the filaments are continuous filaments. Continuous filaments differ as a result of their quasi-continuous length from short fibres which have significantly smaller lengths of, for example, 1 mm to 60 mm. It lies within the scope of the invention that the nonwoven fabric consists or substantially consists of continuous filaments. Instead of the expression continuous filaments, here and subsequently in particular the expression filaments is simply used.2. Description of the Related Art

[0003] Nonwoven fabrics of the type described above and methods for manufacturing such nonwoven fabrics are fundamentally known in practice in various embodiments. For some applications, high strengths, in particular high tensile strengths of the nonwoven fabrics are required or desired. This relates in particular to the tensile strength in the machine direction (MD) and / or transverse to the machine direction (CD). Machine direction (MD) means within the scope of the invention in particular the conveying direction F of the nonwoven fabric on the depositing device. In contrast, CD or CD direction means the direction transverse to the machine direction. In the nonwoven fabrics known from practice, it has been shown that the strength properties frequently do not meet all the requirements. This applies both to nonwoven fabrics of monocomponent filaments and also to nonwoven fabrics of multi-component filaments.

[0004] The strength or tensile strength of the nonwoven fabrics can be influenced by the strength of the individual filaments themselves (single filament strength) and furthermore also by the bonding sites present between the filaments of the finished, consolidated or finally consolidated nonwoven fabric. These factors can in turn be influenced by the choice of raw materials for the filaments. Multi-component filaments and nonwoven fabrics of multi-component filaments can be produced with relatively little expenditure and it is nevertheless possible to influence the strength of the resulting filaments and nonwoven fabrics by the choice of raw material used. Furthermore, it is known from practice that the properties of nonwoven fabrics using multi-component filaments, for example bicomponent filaments, can be adjusted in a more targeted manner than the properties of nonwoven fabrics based on monocomponent filaments. The individual components of multi-component filaments can be optimized separately from one another with a view to specific desired properties of the resulting nonwoven fabric. In this way, the bonding sites between the filaments of the finished nonwoven fabric and the strength of the individual filaments can be influenced in a somewhat targeted manner.

[0005] However, it has been shown that with the measures known from practice, the high strengths required for some applications of nonwoven fabrics, in particular tensile strengths, cannot be achieved to a satisfactory extent. In many nonwoven fabrics known from practice, the strengths or tensile strengths leave something to be desired. This is where the invention begins.SUMMARY OF THE INVENTION

[0006] In view of this, the invention is based on the technical problem of providing a nonwoven fabric of the type mentioned initially which is characterized by a high strength, in particular by a high tensile strength and which nevertheless can be manufactured simply and reliably as well as economically. Furthermore, the invention is based on the technical problem of manufacturing such a nonwoven fabric.

[0007] In order to solve the technical problem, the invention teaches a nonwoven fabric comprising continuous filaments, wherein the filaments are multi-component filaments, in particular bicomponent filaments, and comprise at least one first polypropylene component containing a base-polypropylene and at least one second polypropylene component containing a base-polypropylene,

[0008] wherein the melting point difference between the base-polypropylene of the first polypropylene component and the base-polypropylene of the second polypropylene component is less than 5° C., preferably less than 4° C., more preferably less than 3° C., particularly preferably less than 2° C. and quite particularly preferably less than 1° C.

[0009] and wherein the base-polypropylene of the first polypropylene component and the base-polypropylene of the second polypropylene component were polymerized with a catalyst of the same catalyst class and preferably were each polymerized with a metallocene catalyst or were each polymerized with a Ziegler-Natta catalyst.

[0010] It is preferred that the nonwoven fabric is finally consolidated, preferably thermally finally consolidated or thermobonded and preferably has an embossing pattern of bonding sites, in particular of bonding points. Very preferably the nonwoven fabric is finally consolidated or thermally finally consolidated with a calender, wherein the calender preferably comprises a first calender roller with embossing elements on the outer surface (engraving roller) and / or a second calender roller with a smooth outer surface (S roller).

[0011] According to the invention, the melting point difference between the base-polypropylene of the first polypropylene component and the base-polypropylene of the second polypropylene component is less than 5° C. Melting point means in this connection in particular also melting temperature. The melting point or melting temperature of the base-polypropylene is measured within the scope of the invention in particular by means of differential scanning calorimetry (DSC) according to ISO 11357-3:2011.

[0012] According to the invention, the base-polypropylene of the first polypropylene component and the base-polypropylene of the second polypropylene component were polymerized with a catalyst of the same catalyst class and preferably were each polymerized with a metallocene catalyst or were each polymerized with a Ziegler-Natta catalyst. The expression “the same catalyst class” means in particular within the scope of the invention that a polymerization catalyst of the same genre was used, for example a homogeneous catalyst in each case or a heterogeneous catalyst in each case or a mixed catalyst in each case. According to a preferred embodiment, the base-polypropylene of the first and second polypropylene component were each polymerized with a Ziegler-Natta catalyst or with a metallocene catalyst. Then catalyst class means in particular metallocene catalyst or Ziegler-Natta catalyst. Polypropylenes which have been polymerized with metallocene catalysts are characterized by a narrow molecular weight distribution and / or high stereo regularity in particular compared with polypropylenes which were catalyzed with Ziegler-Natta catalysts. Within the scope of the invention, the molecular weight distribution of a polymer or a polypropylene can be measured in particular according to ASTM D1238-13. When measuring the molecular weight distributions of the polypropylenes or base-polypropylenes according to ASTM D1238-13, expediently trichlorobenzene is used as solvent for the polypropylene plastic and the measurement on the solution is made in particular at a temperature of 160° C., wherein the concentration is in particular 1.5 g / l and an IR sensor is used as sensor. The columns used in the measurement are calibrated with polystyrene standards, wherein the measurement results are converted to “polypropylene” and specifically using the Mark Houwink equation. Expediently the following set of parameters is used: polystyrene: α=0.7; K=0.0138 mL / g polypropylene: α=0.707; K=0.0242 mL / g.

[0013] It lies within the scope of the invention that the second polypropylene component is arranged on the outer surface of the multi-component filaments. It is particularly preferred that the filaments are multi-component filaments or bicomponent filaments having a core-sheath configuration, in particular having a centric or symmetrical core-sheath configuration, and wherein preferably the first polypropylene component forms the core and the second polypropylene component forms the sheath of the filaments. The expression configuration of filaments means within the scope of the invention in particular the cross-sectional configuration of the filaments. In principle, other cross-sectional configurations of the filaments of the nonwoven fabric lie within the scope of the invention, for example a side-by-side configuration or an eccentric core-sheath configuration or a trilobal configuration or the like.

[0014] In connection with the embodiment in which multi-component filaments or bicomponent filaments having a core-sheath configuration, in particular having a centric or symmetrical core-sheath configuration, are used, the invention is based on the finding that the properties of the filament core and the properties of the filament sheath can be specifically influenced by the configuration of the first and the second polypropylene components, wherein as a result of the very small melting point difference between the base-polypropylenes used, which is provided according to the invention and as a result of the polymerization of the base-polypropylene with a catalyst of the same catalyst class, overall filaments can be produced which can be used to provide a nonwoven fabric characterized by a surprisingly high strength, in particular by a surprisingly high tensile strength. The base-polypropylenes are very similar at least with regard to some of their properties—in particular with regard to their melting point or their melting temperature and with regard to their polymerization catalyst—so that as it were multi-component filaments or bicomponent filaments are obtained which—at least with regard to specific properties—simulate a monocomponent filament, wherein however the strength values of the resulting nonwoven fabric are surprisingly significantly higher than for comparable monocomponent filaments. This will be explained in further detail hereinafter. A similar finding is based on the configuration in which the multi-component filaments or bicomponent filaments are configured with different cross-sectional configurations, for example with a side-by-side configuration.

[0015] According to the invention, the first polypropylene component contains a base-polypropylene (first base-polypropylene) and the second polypropylene component contains a base-polypropylene (second base-polypropylene). The expression “base-polypropylene” means within the scope of the invention in particular that the first polypropylene component and the second polypropylene component comprise the respective base-polypropylene in a proportion of at least 55 wt. %, preferably of at least 60 wt. %, more preferably at of least 65 wt. %. It is particularly preferred that the first polypropylene component and / or the second polypropylene component comprises / comprise the respective base-polypropylene in a proportion of at least 70 wt. %, preferably of at least 80 wt. %, more preferably of at least 85 wt. %, particularly preferably of at least 90 wt. % and quite particularly preferably of at least 92 wt. %. It is further preferred that the first polypropylene component and / or the second polypropylene component comprises / comprise the respective base-polypropylene in a proportion of at least 94 wt. %.

[0016] One embodiment of the nonwoven fabric according to the invention which has quite particular importance within the scope of the invention is characterized in that the first polypropylene component and / or the second polypropylene component consists / consist or substantially consists / consist of the respective base-polypropylene. When it is mentioned within the scope of the invention that a component consists or substantially consists of a plastic—for example that the first polypropylene component substantially consists of the (first) base-polypropylene and / or that the second polypropylene component substantially consists of the (second) base-polypropylene—“substantially consists of” means in particular that the component consists of at least 95 wt. %, preferably of at least 98 wt. % and particularly preferably of at least 99 wt. % of the plastic. This in particular takes account of the circumstance that in addition to the said plastic, additives such as softeners, fillers, dyes, lubricants, accessory agents and the like can be present in small quantities.

[0017] It lies within the scope of the invention that the first polypropylene component and / or the second polypropylene component is / are a mixture or a blend of the respective base-polypropylene and at least one additive. According to a preferred embodiment, the additive can comprise a substance which increases the melt flow rate (MFR) of the first polypropylene component and / or the second polypropylene component. A particularly preferred embodiment of the invention is characterized in that the second polypropylene component forms the sheath of the multi-component filaments or bicomponent filaments having a core-sheath configuration and that this second polypropylene component is a mixture or a blend of the base-polypropylene of the second polypropylene component and at least one additive. In principle, the additive can also comprise substances with which other properties of the respective polypropylene component can be set. For example additives with a peroxidic fraction can be used by means of which a molecular weight reduction of the base-polypropylene can be achieved.

[0018] It is quite particularly preferred within the scope of the invention that different polypropylenes are used as the base-polypropylene of the first polypropylene component and as the base-polypropylene of the second polypropylene component. The expression “different polypropylenes” means in particular that the two base-polypropylenes differ with regard to at least one property, for example with regard to their melting point and / or with regard to their molecular weight distribution and / or with regard to their tacticity and / or with regard to their melt flow rate (MFR) and the like. This embodiment in which different polypropylenes are used as the base-polypropylene of the first polypropylene component and as the base-polypropylene of the second polypropylene component has quite particular importance within the scope of the invention. Here and subsequently, in particular the expression “first base-polypropylene” is used for the base-polypropylene of the first polypropylene component and in particular also the expression “second base-polypropylene” is used for the base-polypropylene of the second polypropylene component.

[0019] According to an alternative embodiment of the invention, the same polypropylene is used as the base-polypropylene of the first polypropylene component and as the base-polypropylene of the second polypropylene component and in this case at least one polypropylene component, preferably at least the second polypropylene component, is a mixture or a blend of the base-polypropylene and of at least one additive. Further preferably the second polypropylene component, which according to one embodiment is a mixture or a blend of the base-polypropylene and of at least one additive, forms the sheath component of multi-component filaments or bicomponent filaments having a core-sheath configuration, provided according to a preferred embodiment.

[0020] It lies within the scope of the invention that the proportion of the at least one additive in the first polypropylene component and / or in the second polypropylene component is 0.1 to 30.0 wt. %, preferably 0.2 to 20.0 wt. %, preferably 0.5 to 15.0 wt. %, particularly preferably 1.0 to 10.0 wt. %, quite particularly preferably 1.5 to 9.0 wt. %, further preferably 2.0 to 8.0 wt. %, for example 3.0 to 6.0 wt. %. Further preferably the at least one additive is an additive-polypropylene. According to a very preferred embodiment, this additive polypropylene is a polypropylene that has a higher melt flow rate (MFR) than the base-polypropylene to which the additive or the additive polypropylene is added. As a result, the melt flow rate (MFR) of the resulting polypropylene component can be expediently increased. According to one embodiment, at least the second polypropylene component has an additive in the form of an additive-polypropylene, preferably in the proportions specified above and further preferably this second polypropylene component forms the sheath component of multi-component filaments provided according to a preferred embodiment or bicomponent filaments having a core-sheath configuration.

[0021] According to the invention, the melting point difference between the base-polypropylene of the first polypropylene component and the base-polypropylene of the second polypropylene component is less than 5° C., preferably less than 4° C., more preferably less than 3° C., particularly preferably less than 2° C. and quite particularly preferably less than 1° C. It lies within the scope of the invention that the melting point difference between the base-polypropylene of the first polypropylene component and the base-polypropylene of the second polypropylene component is 0.5° C. to 5° C., preferably 1° C. to 4° C. One embodiment which is of quite particular importance within the scope of the invention is characterized in that the base-polypropylene of the first polypropylene component and the base-polypropylene of the second polypropylene component have the same or substantially the same melting point wherein this particularly preferably comprises different polypropylenes or base-polypropylenes. The fact that the base-polypropylene of the first polypropylene component and the base-polypropylene of the second polypropylene component have the same or substantially the same melting point means within the scope of the invention in particular that the melting point difference between the two base-polypropylenes is 0 ° C. or about 0 ° C..

[0022] A preferred embodiment of the invention is characterized in that the melt flow rate (MFR) of the second polypropylene component is greater than the melt flow rate (MFR) of the first polypropylene component and wherein the ratio of the melt flow rate (MFR) of the second polypropylene component to the melt flow rate (MFR) of the first polypropylene component is in particular 1.02 to 10, preferably 1.05 to 8, more preferably 1.1 to 6, particularly preferably 1.2 to 3, quite particularly preferably 1.3 to 2.2, for example 1.35 to 2.0. This embodiment is based on the finding that the resulting nonwoven fabric - in particular after final consolidation measures - is characterized by an advantageous connection between two individual filaments so that the strength or tensile strength of the nonwoven fabric can be further improved. This applies particularly when the second polypropylene component according to a preferred embodiment is arranged on the outer surface of the filaments and preferably forms the sheath component of the multi-component filaments or bicomponent filaments having a core-sheath configuration. Within the scope of the invention the melt flow rate is preferably measured according to ASTM D 1238-13 under the condition 230° C. and 2.16 kg (condition B) in grams of polymer per 10 minutes (g / 10 min). The melt flow rate (MFR) of mixtures or blends is determined by measuring the melt flow rate (MFR) of the polypropylene or base-polypropylene and by using a logarithmic calculation to calculate the melt flow rate of the blend or mixture.

[0023] Preferably the first polypropylene component has a melt flow rate (MFR) of at least 10 g / 10 min, preferably of at least 12 g / 10 min and / or preferably the second polypropylene component has a melt flow rate (MFR) of at least 15 g / 10 min, preferably of at least 20 g / 10 min. In principle, it also lies within the scope of the invention that the melt flow rate (MFR) of the first polypropylene component is greater than the melt flow rate (MFR) of the second polypropylene component.

[0024] It lies within the scope of the invention that the ratio of the mass of the first polypropylene component to the mass of the second polypropylene component is 95:5 to 50:50, preferably 90:10 to 55:45, preferably 85:15 to 60:40, particularly preferably 85:15 to 65:35, quite particularly preferably 85:15 to 70:30, for example 80:20 to 75:25. This embodiment is based on the finding that by this choice of mass proportions of the polypropylene components, an optimal compromise can be achieved from the influencing of the strength or tensile strength of the nonwoven fabric by the resulting bonding sites between the filaments of the nonwoven fabric—in particular after final consolidation measures—and by the individual filament strength. This applies particularly when the second polypropylene component according to a preferred embodiment is arranged on the outer surface of the filaments and preferably forms the sheath component of the multi-component filaments or bicomponent filaments having a core-sheath configuration.

[0025] A particularly preferred embodiment of the nonwoven fabric according to the invention is characterized by the fact that the base-polypropylene of the first polypropylene component and / or the base-polypropylene of the second polypropylene component and / or the at least one additive-polypropylene is / are a homopolypropylene or a polypropylene copolymer.

[0026] It lies within the scope of the invention that the nonwoven fabric only comprises a nonwoven fabric layer of continuous filaments. However, it also lies within the scope of the invention that the nonwoven fabric comprises a plurality of nonwoven fabric layers arranged one above the other, which in particular are combined to form a nonwoven laminate. According to a preferred embodiment, the nonwoven fabric thus comprises a single nonwoven fabric layer of continuous filaments. Then the mass per unit area of the nonwoven fabric is preferably 20 g / m2 to 110 g / m2, more preferably 25 g / m2 to 85 g / m2, very preferably of 30 g / m2 to 75 g / m2. According to an alternative preferred embodiment, the nonwoven fabric comprises at least two, preferably at least three, in particular three nonwoven fabric layers of continuous filaments. Then the mass per unit area of the nonwoven fabric is preferably between 1 g / m2 and 20 g / m2, more preferably of 2 g / m2 to 19 g / m2, very preferably of 5 g / m2 to 18 g / m2. Expediently these at least two nonwoven fabric layers are combined to form a nonwoven laminate. It lies within the scope of the invention that in the embodiment with at least two, preferably with at least three, in particular with three nonwoven fabric layers, the properties of the nonwoven fabric layers or the filaments of the nonwoven fabric layers are identical or substantially identical. Fundamentally however, it is also possible that the nonwoven fabric layers or the filaments of the nonwoven fabric layers differ from one another in terms of their properties. Preferred however is an embodiment in which at least two, in particular at least three, preferably three identical or substantially identical nonwoven fabric layers are deposited one above the other and further preferably are combined to form a nonwoven laminate.

[0027] It lies within the scope of the invention that the nonwoven fabric has a mass per unit area of 20 g / m2 to 110 g / m2, preferably of 25 g / m2 to 85 g / m2, more preferably of 30 g / m2 to 75 g / m2. According to a further preferred embodiment, the nonwoven fabric has a mass per unit area between 1 g / m2 and 20 g / m2, preferably of 2 g / m2 to 19 g / m2, more preferably of 5 g / m2 to 18 g / m2.

[0028] It is particularly preferred if the nonwoven fabric is finally consolidated, in particular thermally finally consolidated, and preferably has an embossing pattern of bonding sites, in particular of bonding points. This very preferably comprises a nonwoven fabric that has been thermally finally consolidated with a calender or thermobonded. The preferred properties of the nonwoven fabric listed hereinafter preferably refer to such a finally consolidated or thermally finally consolidated nonwoven fabric.

[0029] A preferred embodiment of the invention is characterized in that the nonwoven fabric has a mass per unit area of 20 g / m2 to 110 g / m2, preferably of 25 g / m2 to 85 g / m2, more preferably of 30 g / m2 to 75 g / m2 and wherein preferably the specific tensile strength of the nonwoven fabric in the MD direction is 2.5 to 7.2 N / 5 cm per g / m2, preferably 3.0 to 7.0 N / 5 cm per g / m2, more preferably 3.2 to 6.8 N / 5 cm per g / m2, particularly preferably 3.4 to 6.7 N / 5 cm per g / m2 and quite particularly preferably 3.5 to 6.5 N / 5 cm per g / m2 and / or wherein preferably the specific tensile strength of the nonwoven fabric in the CD direction is 2.0 to 4.0 N / 5 cm per g / m2, preferably 2.1 to 3.8 N / 5 cm per g / m2, more preferably 2.2 to 3.7 N / 5 cm per g / m2, particularly preferably 2.3 to 3.6 N / 5 cm per g / m2. It lies within the scope of the invention that the nonwoven fabric has a mass per unit area of 20 g / m2 to 110 g / m2, preferably of 25 g / m2 to 85 g / m2, more preferably of 30 g / m2 to 75 g / m2 and wherein expediently the tensile strength of the nonwoven fabric in the MD direction is 100 N / 5 cm to 500 N / 5 cm, preferably 120 N / 5 cm to 480 N / 5 cm and / or wherein the tensile strength of the nonwoven fabric in the CD direction is 70 N / 5 cm to 350 N / 5 cm, preferably 90 N / 5 cm to 320 N / 5 cm. The nonwoven fabric having the previously specified mass per unit area and the previously specified tensile strength values or specific tensile strength values preferably comprises a single-layer nonwoven fabric with a single nonwoven fabric layer. The previously described properties of the nonwoven fabric with regard to the tensile strength apply in particular to a nonwoven fabric which has been finally consolidated, preferably thermally finally consolidated and preferably has an embossing pattern of bonding sites, in particular of bonding points.

[0030] A further or alternative preferred embodiment of the invention is characterized in that the nonwoven fabric has a mass per unit area between 1 g / m2 and 20 g / m2, preferably of 2 g / m2 to 19 g / m2, more preferably of 5 g / m2 to 18 g / m2 and wherein preferably the specific tensile strength of the nonwoven fabric in the MD direction is 1.5 to 4.5 N / 5 cm per g / m2, preferably 1.7 to 4.0 N / 5 cm per g / m2, more preferably 1.8 to 3.8 N / 5 cm per g / m2, particularly preferably 2.0 to 3.5 N / 5 cm per g / m2 and quite particularly preferably 2.0 to 3.0 N / 5 cm per g / m2 and / or wherein preferably the specific tensile strength of the nonwoven fabric in the CD direction is 1.0 to 2.5 N / 5 cm per g / m2, preferably 1.1 to 2.0 N / 5 cm per g / m2, more preferably 1.2 to 1.9 N / 5 cm per g / m2, particularly preferably 1.2 to 1.8 N / 5 cm per g / m2. It is further preferred that the nonwoven fabric has a mass per unit area between 1 g / m2 and 20 g / m2, preferably of 2 g / m2 to 19 g / m2, more preferably of 5 g / m2 to 18 g / m2 and wherein expediently the tensile strength of the nonwoven fabric in the MD direction is 20 N / 5 cm to 40 N / 5 cm, preferably 22 N / 5 cm to 38 N / 5 cm and / or wherein the tensile strength of the nonwoven fabric in the CD direction is 8 N / 5 cm to 22 N / 5 cm, preferably 10 N / 5 cm to 21 N / 5 cm. The nonwoven fabric having the previously specified mass per unit area and the previously specified tensile strength values or specific tensile strength values in particular comprises a nonwoven fabric having at least two, preferably having at least three, in particular three, nonwoven fabric layers which are further preferably combined to form a laminate. The previously described properties of the nonwoven fabric with regard to the tensile strength apply in particular to a nonwoven fabric which has been finally consolidated, preferably thermally finally consolidated and preferably has an embossing pattern of bonding sites, in particular of bonding points.

[0031] The tensile strength of the nonwoven fabric according to the invention is determined within the scope of the invention in particularly the following method: “Determination of Tensile Strength (based on EDANA 20.2−89)”: in N / 5 cm; with 50 mm sample width; 100 mm clamping length; 200 mm / min test speed.

[0032] It has already been mentioned previously that the nonwoven fabric is preferably finally consolidated, in particular thermally finally consolidated and preferably has an embossing pattern of bonding sites, in particular of bonding points. Within the framework of a final consolidation measure the nonwoven fabric is expediently finally consolidated, preferably by a calender and to this end is preferably released from the depositing device which guides the nonwoven fabric. In contrast, pre-consolidation measures serve in particular to pre-consolidate or compact the nonwoven fabric for problem-free further transport on the depositing device. An embossing pattern is preferably introduced into the nonwoven fabric within the framework of a final consolidation measure. Expediently the embossing pattern is introduced into the nonwoven fabric within the framework of a final consolidation measure by at least one calender roller with a complementary embossing pattern of embossing elements.

[0033] It lies within the scope of the invention that the nonwoven fabric has an embossing pattern of bonding sites, in particular of bonding points and wherein the proportion of the pore volume in the region of a bonding site is 1.0% to 12.0%, preferably 1.5% to 10.0%, more preferably 2.0% to 7.0%, particularly preferably 2.5% to 6.5%. Proportion of the pore volume means within the scope of the invention in particular the proportion of the volume of pores to the total volume of the bonding site. The proportion of the pore volume in the region of a bonding site is preferably determined within the scope of the invention by micro-computer tomography (μCT). Additionally or alternatively the proportion of the pore volume in the region of a bonding site can be determined by means of porometry using a porosimeter or autoporosimeter. The embodiment of the nonwoven fabric according to the invention with an embossing pattern of bonding sites, wherein the proportion of the pore volume in the region of a bonding site lies in the previously specified region is based on the finding that with such a low porosity in the region of the bonding sites, the strength or tensile strength of the nonwoven fabric can be further increased. Preferably the nonwoven fabric which has a pore volume in the region of a bonding site in the ranges specified above has a mass per unit area of 20 g / m2 to 110 g / m2, preferably of 25 g / m2 to 85 g / m2, further preferably of 30 g / m2 to 75 g / m2.

[0034] A quite particularly preferred embodiment of the nonwoven fabric according to the invention is characterized in that the tensile strength and / or the specific tensile strength of the nonwoven fabric in the MD direction and / or in the CD direction is more than 4%, in particular more than 6%, preferably more than 10%, more preferably more than 15%, particularly preferably more than 20% greater than the corresponding tensile strength and / or the corresponding specific tensile strength of a reference nonwoven fabric which is manufactured from monocomponent filaments of the first polypropylene component or the second polypropylene component and otherwise under the same conditions. It is further preferred that the tensile strength and / or the specific tensile strength of the nonwoven fabric in the MD direction and / or in the CD direction is more than 25%, in particular more than 30%, preferably more than 40%, more preferably more than 50%, further preferably more than 60%, particularly preferably more than 70%, quite particularly preferably more than 80%, for example more than 90%, greater than the corresponding tensile strength and / or the corresponding specific tensile strength of a reference nonwoven fabric that is manufactured from multi-component filaments of the first polypropylene component or the second polypropylene component and otherwise under the same conditions. The previously described properties apply in particular to a nonwoven fabric that is finally consolidated, preferably thermally finally consolidated and which preferably has an embossing pattern of bonding sites, in particular of bonding points.

[0035] The fact that the reference nonwoven fabric is manufactured under the same conditions means within the scope of the invention in particular that the reference nonwoven fabric is manufactured using the same device as the nonwoven fabric according to the invention as well as under the same conditions as the nonwoven fabric according to the invention. In this case, the reference nonwoven fabric has the same number of nonwoven fabric layers as the nonwoven fabric according to the invention and all the nonwoven fabric layers of the reference nonwoven fabric are produced under the same conditions as the nonwoven fabric layers of the nonwoven fabric according to the invention. In particular, pre-consolidation and consolidation or final consolidation measures and the introduction of an embossing pattern of bonding sites in the reference nonwoven fabric are carried out in the same way as in the nonwoven fabric according to the invention. The measurement of the tensile strength or specific tensile strength of the reference nonwoven fabric and the nonwoven fabric according to the invention takes place as already specified hereinbefore. The invention has identified that the nonwoven fabric according to the invention composed of multi-component filaments, in particular of bicomponent filaments has considerable advantages with regard to the tensile strength or the specific tensile strength in the MD direction and / or in the CD direction compared to a nonwoven fabric of monocomponent filaments of the first polypropylene component or the second polypropylene component which is otherwise manufactured under the same conditions. As a result of the similarity according to the invention of the polypropylene components or the base-polypropylenes at least with regard to their properties, bicomponent filaments are obtained as it were which simulate a monocomponent filament—at least with regard to specific properties—wherein however the strength values or the specific strength values of the resulting nonwoven fabric are surprisingly significantly higher than those of a reference nonwoven fabric of monocomponent filaments.

[0036] It lies within the scope of the invention that the TEA sum value (MD-TEA+CD-TEA) of the nonwoven fabric is at least 200 J / m2, preferably at least 300 J / m2, more preferably at least 400 J / m2, particularly preferably at least 500 J / m2. The TEA values and TEA sum values specified here and subsequently apply in particular to a finally consolidated, preferably thermally finally consolidated nonwoven fabric which preferably has an embossing pattern of bonding sites, in particular of bonding points.

[0037] It is very preferred that the nonwoven fabric has a mass per unit area of 20 g / m2 to 110 g / m2, preferably of 25 g / m2 to 85 g / m2, further preferably of 30 g / m2 to 75 g / m2 and wherein the TEA sum value (MD-TEA+CD-TEA) of the nonwoven fabric is at least 1500 J / m2, in particular at least 2500 J / m2, preferably at least 4000 J / m2, preferably at least 5000 J / m2, particularly preferably at least 6000 J / m2, quite particularly preferably at least 8000 J / m2, for example at least 10000 J / m2.

[0038] A further or alternative preferred embodiment of the nonwoven fabric according to the invention is characterized in that the nonwoven fabric has a mass per unit area between 1 g / m2 and 20 g / m2, preferably of 2 g / m2 to 19 g / m2, further preferably of 5 g / m2 to 18 g / m2 and wherein the TEA sum value (MD-TEA+CD-TEA) of the nonwoven fabric is at least 200 J / m2, in particular at least 300 J / m2, preferably at least 500 J / m2.

[0039] TEA value means within the scope of the invention in particular the energy absorption of the nonwoven fabric under tensile loading (Tensile Energy Absorption, TEA). The TEA value in the MD direction or in the CD direction is determined within the scope of the invention in particular from the area below the force-strain curve in each case at maximum force (y value) and maximum strain (x value), wherein the recording of the force-strain curve in the MD direction or in the CD direction is preferably made on dry, non-pretreated nonwoven fabric samples (measurement samples) similar to the test standard DIN EN ISO 9073-3:2023-09. It lies within the scope of the invention that to this end, preferably in each case at least five sufficiently long nonwoven fabric samples having a width of 50 mm in each case are taken equidistantly over the roll width or material section width in the MD direction and CD direction. These samples are clamped between two clamping devices at a distance of 100 mm so that the investigated / measured length of the samples is 100 mm. Then these nonwoven fabric samples are tensioned by means of a tension machine with a feed of 100 mm / min up to a pre-force of 0.5 N. In this state, in particular the measurement is reset to zero and the actual measurement begins. The tension machine operates in particular with a feed or with a tension rate of 200 mm / min. In the MD and CD direction the TEA value is determined in each case in particular as an arithmetic average over the measured samples. The TEA sum value is obtained in particular from the sum of the MD-TEA value in J / m2 and the CD TEA value in J / m2.

[0040] It lies within the scope of the invention that the nonwoven fabric has a mass per unit area of 20 g / m2 to 110 g / m2, preferably of 25 g / m2 to 85 g / m2, more preferably of 30 g / m2 to 75 g / m2 and wherein the TEA sum value (MD-TEA+CD-TEA) of the nonwoven fabric is 1500 to 15000 J / m2, preferably 2500 to 13000 J / m2, and / or wherein the MD-TEA value of the nonwoven fabric is 950 to 8500 J / m2, preferably 1500 to 8000 J / m2 and / or wherein the CD-TEA value of the nonwoven fabric is 500 to 6000 J / m2, preferably 1500 to 5500 J / m2.

[0041] According to a further preferred or alternative embodiment, the nonwoven fabric has a mass per unit area between 1 g / m2 and 20 g / m2, preferably of 2 g / m2 to 19 g / m2, more preferably of 5 g / m2 to 18 g / m2 and wherein the TEA sum value (MD-TEA+CD-TEA) of the nonwoven fabric is 200 to 600 J / m2, preferably 250 to 550 J / m2, and / or wherein the MD-TEA value of the nonwoven fabric is 125 to 400 J / m2, preferably 140 to 350 J / m2 and / or wherein the CD-TEA value of the nonwoven fabric is 80 to 250 J / m2, preferably 90 to 240 J / m2.

[0042] A particularly preferred embodiment of the invention is characterized in that the TEA sum value (MD-TEA+CD-TEA) of the nonwoven fabric is more than 5%, preferably more than 10%, more preferably more than 15%, particularly preferably more than 20%, quite particularly preferably more than 25%, greater than the corresponding TEA sum value (MD-TEA+CD-TEA) of a reference nonwoven fabric which is manufactured from monocomponent filaments of the first polypropylene component or the second polypropylene component and otherwise under the same conditions. Within the scope of this embodiment, the same stipulations apply for the reference nonwoven fabric as has already been described above and specifically in particular with regard to the device for producing the reference nonwoven fabric and the conditions for producing the reference nonwoven fabric. It is further preferred that the TEA sum value (MD-TEA+CD-TEA) of the nonwoven fabric is more than 30%, preferably more than 40%, more preferably more than 50%, particularly preferably more than 60%, quite particularly preferably more than 70%, for example more than 80%, greater than the corresponding TEA sum value (MD-TEA+CD-TEA) of a reference nonwoven fabric which is manufactured from monocomponent filaments of the first polypropylene component or the second polypropylene component and otherwise under the same conditions.

[0043] It is preferred that the nonwoven fabric has a mass per unit area of 20 g / m2 to 110 g / m2, preferably of 25 g / m2 to 85 g / m2, more preferably of 30 g / m2 to 75 g / m2 and wherein the TEA sum value (MD-TEA+CD-TEA) of the nonwoven fabric is more than 40%, preferably more than 80%, particularly preferably more than 100%, further preferably more than 200%, quite particularly preferably more than 300%, greater than the corresponding TEA sum value (MD-TEA+CD-TEA) of a reference nonwoven fabric which is manufactured from monocomponent filaments of the first polypropylene component or the second polypropylene component and otherwise under the same conditions.

[0044] According to a further or alternative embodiment of the nonwoven fabric according to the invention, the nonwoven fabric has a mass per unit area between 1 g / m2 and 20 g / m2, preferably of 2 g / m2 to 19 g / m2, more preferably of 5 g / m2 to 18 g / m2 and wherein the TEA sum value (MD-TEA+CD-TEA) of the nonwoven fabric is more than 15%, preferably more than 25%, more preferably more than 30%, particularly preferably more than 50%, greater than the corresponding TEA sum value (MD-TEA+CD-TEA) of a reference nonwoven fabric which is manufactured from monocomponent filaments of the first polypropylene component or the second polypropylene component and otherwise under the same conditions.

[0045] It lies within the scope of the invention that the filaments have a titre of less than 2.3 den, preferably less than 2.1 den, more preferably less than 1.9 den and particularly preferably have a titre of 1.0 to 2.2 den, quite particularly preferably of 1.2 to 2.0 den, for example of 1.4 to 1.8 den.

[0046] In order to solve the technical problem the invention furthermore teaches a method for manufacturing a nonwoven fabric described hereinbefore, wherein filaments are produced by means of at least one spinning device, in particular by means of at least one spinneret and are deposited on at least one depositing device, in particular on at least one depositing foraminous belt, to form the nonwoven fabric.

[0047] It lies within the scope of the invention that the nonwoven fabric according to the invention or the nonwoven fabric layers of the nonwoven fabric according to the invention is / are manufactured by a spunbond method. A preferred spunbond method for the nonwoven fabric according to the invention or for the nonwoven fabric layers is described hereinafter. The filaments or continuous filaments of the nonwoven fabric or the nonwoven fabric layers are spun by means of a spinning device configured as a spinneret and then cooled in a cooling device with a cooling chamber. It lies within the scope of the invention that a monomer extraction device is arranged between the spinneret and the cooling device by means of which perturbing gases produced during the spinning process can be removed from the device. After running through the cooling device the filaments are expediently guided through a stretching device for stretching the continuous filaments. It is recommended that the stretching device has an intermediate channel that connects the cooling device to a stretching shaft of the stretching device. According to a preferred embodiment of the invention, the unit comprising the cooling device and the stretching device or the unit comprising the cooling device, the intermediate channel and the stretching shaft is configured as a closed unit and apart from the supply of cooling air in the cooling device, no further air is supplied from outside into this unit.

[0048] Preferably at least one diffuser through which the continuous filaments are guided adjoins the stretching device in the filament flow direction. Expediently after passing through the at least one diffuser, the continuous filaments are deposited on a depositing device which is preferably configured as a depositing foraminous belt. It is recommended that the depositing foraminous belt is a continuously circulating depositing foraminous belt. Expediently the depositing foraminous belt is configured to be permeable to air so that process air can be extracted from below through the depositing foraminous belt. Preferably at least one extraction device is provided under the depositing foraminous belt for extracting the process air. If the nonwoven fabric according to one embodiment of the invention comprises at least two, preferably at least three, nonwoven fabric layers, then the device for manufacturing the corresponding nonwoven fabric within the framework of the method according to the invention preferably accordingly has at least two, preferably at least three spinnerets or spinning beams having the previously described components each arranged within the region or inside the spinneret and the devices for producing the nonwoven fabric layers are preferably arranged above a single depositing device, in particular above a single depositing foraminous belt on which the nonwoven fabric layers of the nonwoven fabric are deposited one above the other and then preferably combined to form a nonwoven laminate.

[0049] It lies within the scope of the method according to the invention that the nonwoven fabric is finally consolidated using at least one consolidating device, in particular using at least one calender roller and wherein preferably the temperature, in particular the surface temperature of the at least one consolidating device, in particular of the at least one calender roller, is 120° C. to 180° C., preferably 130° C. to 175° C., preferably 140° C. to 170° C., very preferably 145° C. to 165° C. According to a particularly preferred embodiment of the method according to the invention, the nonwoven fabric is finally consolidated using a consolidating device configured as a calender with at least two calender rollers and expediently the surface temperature of at least one calender roller of the calender, preferably of both calender rollers of the calender is 120° C. to 180° C., preferably 130° C. to 175° C., preferably 140° C. to 170° C., very preferably 145° C. to 165° C. According to a very preferred embodiment, the consolidating device, in particular the calender, comprises at least one calender roller (engraving roller) for introducing an embossing pattern of bonding sites, in particular of bonding points, wherein to this end the calender roller preferably has a complementary embossing pattern of embossing element on the outer surface. Further preferably the consolidating device, in particular the calender, comprises at least one calender roller (S roller) with a smooth outer surface.

[0050] It lies within the scope of the invention that the complementary embossing pattern of the at least one calender roller for introducing an embossing pattern of bonding sites or bonding points into the nonwoven fabric has an embossing area of 5% to 35%, preferably of 10% to 25% and / or a figure density of 10 Fig / cm2 to 100 Fig / cm2, preferably of 25 Fig / cm2 to 75 Fig / cm2.

[0051] It lies within the scope of the invention that the temperature, in particular the surface temperature of the at least one consolidating device, is particular of the at least one calender roller, is at least 1° C., preferably at least 2° C., more preferably at least 3° C., particularly preferably at least 4° C., quite particularly preferably at least 5° C. lower than the melting point of the base-polypropylene of the second polypropylene component and / or the melting point of the base-polypropylene of the first polypropylene component. Preferably these details relate to the two calender rollers of a consolidating device configured as a calender.

[0052] It lies within the scope of the method according to the invention that the speed of the depositing device, in particular the speed of the depositing foraminous belt, is 30 m / min to 1100 m / min, preferably 40 m / min to 1000 m / min, It lies within the scope of the invention that the nonwoven fabric has a mass per unit area of 20 g / m2 to 110 g / m2, preferably of 25 g / m2 to 85 g / m2, more preferably of 30 g / m2 to 75 g / m2 and wherein the speed of the depositing device, in particular the speed of the depositing foraminous belt, is 30 m / min to 120 m / min, preferably 40 m / min to 110 m / min. It lies furthermore or alternatively within the scope of the invention that the nonwoven fabric has a mass per unit area between 1 g / m2 and 20 g / m2, preferably of 2 g / m2 to 19 g / m2, preferably of 5 g / m2 to 18 g / m2 and wherein the speed of the depositing device, in particular the speed of the depositing foraminous belt, is 250 to 1200 m / min, preferably 500 to 1100 m / min.EXEMPLARY EMBODIMENT 1 ACCORDING TO THE INVENTION

[0053] In a first exemplary embodiment according to the invention, a single-layer nonwoven fabric of bicomponent filaments having a centric or symmetrical core-sheath configuration was produced. The core component of the bicomponent filaments was formed by a first polypropylene component which consisted or substantially consisted of a first base-polypropylene. A second polypropylene component was used for the sheath component which consisted or substantially consisted of a second base-polypropylene. The bicomponent filaments were produced as continuous filaments by the spunbond method in a device described hereinbefore or according to the method for producing nonwoven fabrics or spunbond nonwoven fabric described hereinbefore. The bicomponent filaments were produced with a filament fineness of 1.6 den. The nonwoven fabric was finally consolidated using a calender with a surface temperature of the engraving roller of the calender of 155° C. and the S roller of 150° C. and specifically with an embossing area of 18.1% with oval consolidation elevations in a density of 49.9 Fig / cm2. A homopolypropylene with a melt flow rate of 15 g / 10 min was used as the first polypropylene component or as the first base-polypropylene. The first polypropylene component or the first base-polypropylene formed the core of the bicomponent filaments of the continuous filaments of the first exemplary example according to the invention. The homopolypropylene “Total MR 2002” was used here for the first polypropylene component or for the first base-polypropylene. This is a metallocene polypropylene that is polymerized with a metallocene catalyst. A homopolypropylene with a melt flow rate (MFR) of 25 g / 10 min was used as the second polypropylene component or as the second base-polypropylene. The second polypropylene component or the second base-polypropylene formed the sheath of the bicomponent filaments having a core-sheath configuration. The homopolypropylene “Total MR 2001” was used here for the second polypropylene component or for the second base-polypropylene. This is a metallocene polypropylene that is polymerized with a metallocene catalyst.

[0054] The ratio of the mass of the first polypropylene component to the mass of the second polypropylene component was 80:20. The speed of the depositing device or the speed of the depositing foraminous belt was 62 m / min. The mass per unit area of the resulting nonwoven fabric was 66 g / m2. The melting point difference between the base-polypropylene of the first polypropylene component and the base-polypropylene of the second polypropylene component was 0 ° C. or approximately 0 ° C. Both polypropylenes have a melting point of 151° C. The specific tensile strength of the nonwoven fabric in the MD direction was 4.9 N / 5 cm per g / m2 and the specific tensile strength of the nonwoven fabric in the CD direction was 3.3 N / 5 cm per g / m2. The TEA sum value (MD-TEA+CD-TEA) of the nonwoven fabric was 6247 J / m2. The MD-TEA value of the nonwoven fabric was 3824 J / m2 and the CD-TEA value of the nonwoven fabric was 2423 J / m2.Reference Nonwoven Fabric 1

[0055] A reference nonwoven fabric 1 was produced from monocomponent filaments of the first polypropylene component described above for the first exemplary embodiment according to the invention and otherwise under the same conditions as in the first exemplary embodiment according to the invention. The resulting reference nonwoven fabric was identical to the nonwoven fabric according to the invention and described hereinbefore of the first exemplary embodiment according to the invention with regard to its filament titre and with regard to its mass per unit area. The reference nonwoven fabric 1 had a specific tensile strength in the MD direction of 2.6 N / 5 cm per g / cm2 and in the CD direction of 1.8 N / 5 cm per g / m2. The reference nonwoven fabric 1 had a TEA sum value of 1639 J / m2, wherein the MD-TEA value was 901 J / m2 and the CD TEA value was 738 J / m2. Thus the specific tensile strength of the nonwoven fabric according to the invention according to the first exemplary embodiment according to the invention in the MD direction and in the CD direction is more than 80% greater than the corresponding tensile strength of the reference nonwoven fabric which was produced from monocomponent filaments of the first polypropylene component and otherwise under the same conditions. In addition, the TEA sum value of the nonwoven fabric according to the invention is more than 280% greater than the corresponding TEA sum value of the reference nonwoven fabric which was produced from monocomponent filaments of the first polypropylene component and under otherwise the same conditions.EXEMPLARY EMBODIMENT 2 ACCORDING TO THE INVENTION

[0056] In a second exemplary embodiment according to the invention, a nonwoven fabric of bicomponent filaments having a centric or symmetrical core-sheath configuration was produced. The nonwoven fabric was produced as a three-layer nonwoven fabric with three identical nonwoven fabric layers. The bicomponent filaments were produced as continuous filaments by the spunbond method in a device described hereinbefore or according to the method for producing nonwoven fabrics or spunbond nonwoven fabric described hereinbefore, wherein three consecutively connected spinnerets or spinning beams with the components arranged thereunder in each case above a single depositing foraminous belt. The core component of the bicomponent filaments was formed by a first polypropylene component which consisted or substantially consisted of a first base-polypropylene. A second polypropylene component which consisted or substantially consisted of the second base-polypropylene was used for the sheath component. The bicomponent filaments were produced with a filament fineness of 1.4 to 1.5 den. The nonwoven fabric was finally consolidated using a calender with a surface temperature of the engraving roller of the calender of 160° C. and the S roller of 150° C. and specifically with an embossing area of 18.1% with round consolidation elevations in a density of 49.9 Fig / cm2. A homopolypropylene with a melt flow rate of 25 g / 10 min was used as the first polypropylene component or as the first base-polypropylene. The first polypropylene component or the first base-polypropylene formed the core of the bicomponent filaments of the continuous filaments of the second exemplary example according to the invention. The homopolypropylene “Borealis HG 475FB” was used here for the first polypropylene component or for the first base-polypropylene. This is a Ziegler-Natta polypropylene that is polymerized with a Ziegler-Natta catalyst. A homopolypropylene with a melt flow rate (MFR) of 35 g / 10 min was used as the second polypropylene component or as the second base-polypropylene. The second polypropylene component or the second base-polypropylene formed the sheath of the bicomponent filaments having a core-sheath configuration. The homopolypropylene “Exxon 3155” was used here for the second polypropylene component or for the second base-polypropylene. This is a Ziegler-Natta polypropylene that is polymerized with a Ziegler-Natta catalyst. The ratio of the mass of the first polypropylene component to the mass of the second polypropylene component was 70:30. The speed of the depositing device or the speed of the depositing foraminous belt was 620 m / min. The mass per unit area of the resulting nonwoven fabric was 13 g / m2. The melting point difference between the base-polypropylene of the first polypropylene component and the base-polypropylene of the second polypropylene component was 0 ° C. or approximately 0° C. Both polypropylenes have a melting point of 161° C. The specific tensile strength of the nonwoven fabric in the MD direction was 2.8 N / 5 cm per g / m2 and the specific tensile strength of the nonwoven fabric in the CD direction was 1.5 N / 5 cm per g / m2. The TEA sum value (MD-TEA +CD-TEA) of the nonwoven fabric was 513 J / m2. The MD-TEA value of the nonwoven fabric was 311 J / m2 and the CD-TEA value of the nonwoven fabric was 202 J / m2.Reference Nonwoven Fabric 2

[0057] A reference nonwoven fabric 1 was produced from monocomponent filaments of the first polypropylene component described above for the second exemplary embodiment according to the invention and otherwise under the same conditions as in the second exemplary embodiment according to the invention. The resulting reference nonwoven fabric 2 was identical to the nonwoven fabric according to the invention and described hereinbefore of the second exemplary embodiment according to the invention with regard to its filament titre and with regard to its mass per unit area. The reference nonwoven fabric 2 had a specific tensile strength in the MD direction of 2.6 N / 5 cm per g / cm2 and in the CD direction of 1.3 N / 5 cm per g / m2. The reference nonwoven fabric 2 had a TEA sum value of 393 J / m2, wherein the MD-TEA value was 246 J / m2 and the CD TEA value was 147 J / m2. Thus the specific tensile strength of the nonwoven fabric according to the invention according to the second exemplary embodiment according to the invention in the MD direction is more than 7% and in the CD direction more than 15% greater than the corresponding tensile strength of the reference nonwoven fabric which was produced from monocomponent filaments of the first polypropylene component and otherwise under the same conditions. In addition, the TEA sum value of the nonwoven fabric according to the invention (second exemplary embodiment according to the invention) is more than 30% greater than the corresponding TEA sum value of the reference nonwoven fabric which was produced from monocomponent filaments of the first polypropylene component and under otherwise the same conditions.

[0058] The invention is based on the finding that the nonwoven fabric according to the invention comprising multi-component filaments, in particular bicomponent filaments, is characterized by a surprisingly high strength or tensile strength compared to the measures known from practice. As a result of the similarity of the base-polypropylene of the first polypropylene component and the base-polypropylene of the second polypropylene component, at least with regard to some properties—in particular with regard to the melting point and the polymerization catalyst—as well as the properties resulting therefrom, multi-component filaments or bicomponent filaments are prepared which as it were simulate a monocomponent filament—at least with regard to specific properties—wherein the properties of the filaments can be specifically set compared to monocomponent filaments. This results in nonwoven fabrics having very high tensile strength values in the MD direction and / or in the CD direction which reliably fulfil all the requirements for the strength, in particular for the tensile strength. It should also be stressed that the measures according to the invention are not very expensive and that the nonwoven fabric according to the invention and the method according to the invention are very economical.BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Other objects and features of the invention will become apparent from the following detailed description considered in connection with the accompanying drawings. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the invention.

[0060] In the drawings,

[0061] FIG. 1 shows a vertical section through a device for producing a nonwoven fabric according to the invention or a nonwoven fabric layer of a nonwoven fabric according to the invention; and

[0062] FIG. 2 shows cross-section through a filament of a nonwoven fabric according to the invention having a centric or symmetrical core-sheath configuration.DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0063] FIG. 1 shows a device for producing a nonwoven fabric 8 according to the invention or a nonwoven fabric layer of a nonwoven fabric 8 according to the invention. If the nonwoven fabric according to a preferred embodiment comprises at least two, preferably at least three, in particular three nonwoven fabric layers, at least two, preferably at least three or three spinnerets 6 or spinning beams each with the components arranged thereunder in the conveying direction F of the depositing foraminous belt 7 or in the machine direction (MD) are connected consecutively and the three nonwoven fabric layers are preferably deposited one above the other on a single depositing foraminous belt 7 and preferably combined to form a laminate.

[0064] The device preferably and in the exemplary embodiment comprises a spinning device in the form of a spinneret 6 or a spinning beam for spinning filaments or continuous filaments 1 for a nonwoven fabric 8 or a nonwoven fabric layer of a nonwoven fabric 8. Preferably and in the exemplary embodiment, the continuous filaments 1 spun by the spinneret 6 are introduced into a cooling device 12 with a cooling chamber 13. Preferably and in the exemplary embodiment, air supply cabins 14, 15 arranged one above the other are arranged on two opposite sides of the cooling chamber 13. From the air supply cabins 14, 15 arranged one above the other air at different temperatures is expediently introduced into the cooling chamber 13. Preferably and in the exemplary embodiment a monomer extraction device 16 is arranged between the spinneret 6 and the cooling device 12. Perturbing gases which occur during the spinning process can be removed from the device by means of this monomer extraction device.

[0065] It is recommended that and in the exemplary embodiment, a stretching device 17 for stretching the continuous filaments 1 is located downstream of the cooling device 12 in the filament flow direction. Expediently and in the exemplary embodiment, the stretching device 17 has an intermediate channel which connects the cooling device 12 with the stretching shaft 19 of the stretching device 17. Preferably and in the exemplary embodiment, the unit comprising the cooling device 12 and the stretching device 17 or the unit comprising the cooling device 12, the intermediate channel 18 and the stretching shaft 19 is configured as a closed unit and apart from the supply of cooling air in the cooling device 12, no further air is supplied from outside into this unit.

[0066] Expediently and in the exemplary embodiment, a diffuser 20 through which the continuous filaments 1 are guided adjoins the stretching device 17 in the filament flow direction. After running through the diffuser 20, the continuous filaments 1 are preferably and in the exemplary embodiment deposited in a deposition region on a depositing device configured as a depositing foraminous belt 7. The depositing foraminous belt 7 is expediently and in the exemplary embodiment designed as a continuously circulating depositing foraminous belt 7. It lies within the scope of the invention that the depositing foraminous belt 7 is permeable to air so that it is possible to extract process air from below through the depositing foraminous belt 7. Preferably and in the exemplary embodiment, in the conveying direction F of the nonwoven fabric or in the machine direction MD downstream of the depositing region of the continuous filaments 1 the device has a consolidating device configured as a calender 11 for final consolidation of the nonwoven fabric 8. Preferably and in the exemplary embodiment the calender 11 comprises two calender rollers 9, 10. It is possible that one of the calender rollers 9, 10, in particular also called engraving roller has a complementary embossing pattern of embossing elements on the outer surface with which an embossing pattern of bonding sites, in particular of bonding points can be introduced into the nonwoven fabric 8. According to a preferred embodiment, the second calender roller, in particular also called S roller, can have a smooth outer surface. This is not shown in detail in FIG. 1.

[0067] FIG. 2 shows a section through a continuous filament 1 having a centric or symmetrical core-sheath configuration. This is a bicomponent filament 1 with a first polypropylene component 2 which preferably and in the exemplary embodiment consists or substantially consists of a first base-polypropylene and which forms the core 4 of the bicomponent filament 1. The bicomponent filament 1 further comprises a second polypropylene component 3 which preferably and in the exemplary embodiment consists or substantially consists of a second base-polypropylene and forms the sheath 5 of the bicomponent filament 1. The base-polypropylene of the first polypropylene component 2 and the base-polypropylene of the second polypropylene component 3 may preferably and in the exemplary embodiment have each been polymerized with a metallocene catalyst and have the same or substantially the same melting point, wherein expediently and in the exemplary embodiment the base-polypropylene of the first polypropylene component 2 and the base-polypropylene of the second polypropylene component 3 are different polypropylenes. The ratio of the mass of the first polypropylene component 2 which forms the core 4 of the bicomponent filament 1 to the mass of the second bicomponent filaments component 3 which forms the sheath 5 of the bicomponent filament 1 may expediently and in the exemplary embodiment be about 75:25.

[0068] Although only a few embodiments of the present invention have been shown and described, it is to be understood that many changes and modifications may be made thereunto without departing from the spirit and scope of the invention.

Claims

1. A nonwoven fabric comprising continuous filaments, wherein the filaments are multi-component filaments, and comprise at least one first polypropylene component containing a base-polypropylene and at least one second polypropylene component containing a base-polypropylene,wherein a melting point difference between the base-polypropylene of the first polypropylene component and the base-polypropylene of the second polypropylene component is less than 5° C.,and wherein the base-polypropylene of the first polypropylene component and the base-polypropylene of the second polypropylene component were polymerized with a catalyst of the same catalyst class.

2. The nonwoven fabric according to claim 1, wherein the filaments are multi-component filaments or bicomponent filaments having a core-sheath configuration.

3. The nonwoven fabric according to claim 1, wherein the first polypropylene component and / or the second polypropylene component comprises / comprise the respective base-polypropylene in a proportion of at least 70 wt. %.

4. The nonwoven fabric according to claim 1, wherein the first polypropylene component and / or the second polypropylene component consists / consist or substantially consists / consist of the respective base-polypropylene.

5. The nonwoven fabric according to claim 1, wherein the first polypropylene component and / or the second polypropylene component is / are a mixture or a blend of the respective base-polypropylene and at least one additive.

6. The nonwoven fabric according to claim 1, wherein the base-polypropylene of the first polypropylene component is different from the base-polypropylene of the second polypropylene component.

7. The nonwoven fabric according to claim 1, wherein base-polypropylene of the first polypropylene component and the base-polypropylene of the second polypropylene component are the same, and wherein at least one of the polypropylene components is a mixture or a blend of the base-polypropylene and of at least one additive.

8. The nonwoven fabric according to claim 5, wherein the proportion of the at least one additive in the first polypropylene component and / or in the second polypropylene component is 0.1 to 30.0 wt. %, and wherein the at least one additive is an additive-polypropylene.

9. The nonwoven fabric according to claim 1, wherein the base-polypropylene of the first polypropylene component and the base-polypropylene of the second polypropylene component have the same or substantially the same melting point.

10. The nonwoven fabric according to claim 1, wherein a melt flow rate (MFR) of the second polypropylene component is greater than a melt flow rate (MFR) of the first polypropylene component and wherein a ratio of the melt flow rate (MFR) of the second polypropylene component to the melt flow rate (MFR) of the first polypropylene component is 1.02 to 10.

11. The nonwoven fabric according to claim 1, wherein a ratio of a mass of the first polypropylene component to a mass of the second polypropylene component is 95:5 to 50:50.

12. The nonwoven fabric according to claim 8, wherein the base-polypropylene of the first polypropylene component and / or the base-polypropylene of the second polypropylene component and / or the at least one additive-polypropylene is / are a homopolypropylene or a polypropylene copolymer.

13. The nonwoven fabric according to claim 1, wherein the nonwoven fabric is finally consolidated.

14. The nonwoven fabric according to claim 1, wherein the nonwoven fabric has a mass per unit area of 20 g / m2 to 110 g / m2, wherein the specific tensile strength of the nonwoven fabric in an MD direction is 2.5 to 7.2 N / 5 cm per g / m2, and / or wherein the specific tensile strength of the nonwoven fabric in a CD direction is 2.0 to 4.0 N / 5 cm per g / m2.

15. The nonwoven fabric according to claim 1, wherein the nonwoven fabric has a mass per unit area between 1 g / m2 and 20 g / m2, wherein a specific tensile strength of the nonwoven fabric in an MD direction is 1.5 to 4.5 N / 5 cm per g / m2, and / or wherein the specific tensile strength of the nonwoven fabric in a CD direction is 1.0 to 2.5 N / 5 cm per g / m2.

16. The nonwoven fabric according to claim 1, wherein the nonwoven fabric has an embossing pattern of bonding sites and wherein a proportion of pore volume in a region of a bonding site is 1.0% to 12.0%.

17. The nonwoven fabric according to claim 1, wherein a tensile strength and / or a specific tensile strength of the nonwoven fabric in an MD direction and / or in a CD direction is more than 4% greater than the corresponding tensile strength and / or the corresponding specific tensile strength of a reference nonwoven fabric which is manufactured from monocomponent filaments of the first polypropylene component or the second polypropylene component and otherwise under the same conditions.

18. The nonwoven fabric according to claim 1, wherein a TEA sum value (MD-TEA+CD-TEA) of the nonwoven fabric is at least 200 J / m2.

19. The nonwoven fabric according to claim 1, wherein a TEA sum value (MD-TEA+CD-TEA) of the nonwoven fabric is more than 5% greater than the corresponding TEA sum value (MD-TEA+CD-TEA) of a reference nonwoven fabric which is manufactured from monocomponent filaments of the first polypropylene component or the second polypropylene component and otherwise under the same conditions.

20. The nonwoven fabric according to claim 1, wherein the filaments have a titre of less than 2.3 den.

21. A method for manufacturing the nonwoven fabric according to claim 1, comprising the step of producing the filaments by means of at least one spinneret, and depositing the filaments on at least one depositing foraminous belt, to form the nonwoven fabric.

22. The method according to claim 21, wherein the nonwoven fabric is finally consolidated using at least one consolidating device and wherein the temperature of the at least one consolidating device is 120° C. to 180° C.

23. The method according to claim 22, wherein the temperature of the at least one consolidating device is at least 1° C. lower than a melting point of the base-polypropylene of the second polypropylene component and / or the melting point of the base-polypropylene of the first polypropylene component.

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