EP2943607B1

EP2943607B1 - Batt comprising crimped bi- or multi-component fibres

Info

Publication number: EP2943607B1
Application number: EP14705962.0A
Authority: EP
Inventors: Jaroslav KOHUT; Zdenek Mecl; Frantisek Klaska; Pavlina Kasparkova
Original assignee: Pegas Nonwovens sro
Current assignee: Pegas Nonwovens sro
Priority date: 2013-01-14
Filing date: 2014-01-14
Publication date: 2017-03-15
Anticipated expiration: 2034-01-14
Also published as: WO2014108106A8; SA515360784B1; RU2649264C2; WO2014108106A1; JP2016507012A; CZ201324A3; JP6508654B2; RU2015132469A; ES2628416T3; EP2943607A1; MY171876A; DK2943607T3; ZA201504970B; US20150354112A1; BR112015016685A2; PL2943607T3; CN105051280A; HUE034578T2

Description

Technical Field

The invention relates to a batt comprising crimped bi- or multicomponent fibres consisting of at least two materials, which comprise a polymer as a predominant component and which are arranged across the cross-section of the fiber in a way suitable to promote crimping of the fibre during the setting process and which predominant polymer components differ in the crystallisation heat (dHc). The here-described batt type is intended especially for the production of nonwoven textiles that are to be used primarily for applications in the hygiene industry.

Background art

The bulkiness of nonwoven textiles may be of significance for a number of reasons. Nonwoven textiles are often used as a part of hygiene products, where the bulkiness of the material may be used both for reasons of functionality (for example as a part of the loop part of the fastening system consisting of hooks and loops or, for example, for the improvement in the distribution of liquids in the core of absorptive products) as well as for sensory reasons - the bulkiness of the material, apart from other things, gives softness and may be positively accepted in contact with the skin. In certain cases, nonwoven textiles may be used as a part of cleaning products such as for example wipes and dusters. The improvement in bulkiness of such nonwoven textiles may also improve their effectiveness as a cleaning element.
In a number of cases, effort was intentionally expended into creating or modifying certain properties of nonwoven textile materials with the objective of their improvement. These efforts consisted of the selection and/or modification of various chemical compositions of fibres, the basis weight, the fibre layering method, the density of fibres, the extrusion of various patterns, the use of various types of bonding.
The bulkiness of a nonwoven textile is directly related to the properties of the fibres that form it. Homogenous continuous fibres are typical for spunmelt nonwoven textiles. Bulkiness can subsequently be increased by the use of bonding methods. One method consists of the use of such thermal bonding methods, which retain the maximum share of loose fibre segments between the individual bonding points that are used to achieve the required strength of the final material. Another method consists of exposing the nonwoven textile, after calender bonding, to a jet of water (hydroenhancing or hydroentanglement) in order to fluff up the fibres and increase their specific thickness.
Another method consists of producing nonwoven textiles from "bicomponent" polymer fibres, includes steps where these fibres are created under the spinneret, laid to create a batt and subsequently bonded using an embossing calender selected for the purpose of achieving a certain patterned effect. Such bicomponent fibres can be produced using spinnerets equipped with two adjacent sections, where the first polymer is delivered through the first one and the second polymer is delivered through the second in order to create a fibre having one part of the cross-section formed by the first polymer and the second part of the cross-section formed by the second polymer (hence the term "bicomponent"). The respective polymers can be selected to have differing characteristic properties, which enable, in the side-by-side or asymmetrical core / sheath geometry combinations, the curling of bicomponent fibres during the spinning process as they are cooled and drawn from under the spinneret. Various documents are known to exist that deal with the application of individual differences for achieving the curling of fibres. For example the European patent EP0685579 from Kimberly Clark describes the combination of polypropylene and polyethylene. Another European patent EP1129247 from the same company describes the combination of different polypropylenes. The key here is the degree of difference of the individual described properties.
The resulting curled fibres can then be laid to create a batt that is subsequently bonded using various methods to create a bulky nonwoven textile.
EP2343406 discloses a nonwoven fabric of crimped fibres as defined in the preamble of claim1.

Summary of the invention

A batt according to the invention comprises crimped bi- or multicomponent fibres consisting of at least two polymeric components, which are mutually arranged across the cross section of the fibers such that they promote crimping of the fibres during the setting process and which differ in the crystallisation heat, where the substance of the invention is that the difference in the crystallisation heat (dHc) is in the range from 30 J/g to 1OJ/g, preferably 30 J/g to 20 J/g and that the described polymeric components differ in at least one of the other parameters selected from the group of melt flow index, degree of polydispersion and the flexural modulus, while the relative difference of the polymer components is:

for the flow index in the range from 100g/10min to 5g/10min and/or
for the degree of polydispersion in the range from 1 to 0.3, and/or
for the flexural modulus in the in the range from 300 MPa to 50 MPa;

Preferred and / or specific embodiments of the invention are defined in the dependent claims. In a further aspect, the invention regards a method of production of such batts.

Brief description of the drawings

Fig. 1A - examples of asymmetrical (crimping promoting) arrangement of the component sections across the cross-section of a multicomponent fibre
Fig. 1B - example of a symmetrical arrangement of the component sections in the cross-section of a multicomponent fibre
Fig. 2 - example of spunmelt production line

Definitions

The term "batt" here refers to materials in the form of fibres that are found in the state prior to bonding that is performed during the calendering process described for example in patent application WO2012130414 . The "batt" consists of individual fibres between which a fixed mutual bond is usually not yet formed even though they may be pre-bonded in certain ways, where this pre-bonding may occur during or shortly after the laying of fibres in the spunlaying process. This pre-bonding, however, still permits a substantial number of the fibres to be freely moveable such that they can be repositioned. The here-mentioned "batt" may consist of several strata created by the deposition of fibres from several spinning beams in the spunlaying process.
The terms "fibre" and "filament" are in this case mutually interchangeable.
The term "monocomponent fibre" refers to a fibre formed of a single polymer or polymer blend, as distinguished from bicomponent or multicomponent fibre.
"Bicomponent" refers to a fibre having a cross-section comprising two discrete polymer sections, two discrete polymer blend sections, or one discrete polymer section and one discrete polymer blend section. The term "bicomponent fibre" is encompassed within the term "multicomponent fibre". A bicomponent fibre may have an overall cross-section divided into two or more sections consisting of differing sections of any shape or arrangement, including for example, a coaxial arrangement, core-and-sheath arrangement, side-by-side arrangement, radial arrangement.
The term "multicomponent" refers to a fibre having a cross-section comprising more than one discrete polymer section, or more than one polymer blend section, or at least one discrete polymer component and at least one polymer blend section. The term "multicomponent fibre" thus includes, but is not limited to, "bicomponent fibre". A multicomponent fibre may have an overall cross-section divided into parts consisting of differing sections of any shape or arrangement, including, for example, a coaxial arrangement, core-and-sheath arrangement, side-by-side arrangement, radial arrangement, islands-in-the-sea arrangement.
As used herein, the term "nonwoven textile" means a structure in the form of a fleece or webbing formed from directed or randomly oriented fibres, from which initially a batt is formed and which is subsequently consolidated and fibres are mutually bonded by friction, effects of cohesive forces, gluing or by similar methods creating a single or multiple bonding patterns consisting of bonding imprints formed by a bounded compression and/or the effect of pressure, heat, ultrasound or heat energy, or a combination of these effects if necessary. The term does not refer to fabrics formed by weaving or knitting or fabrics using yarn or fibres to form bonding stitches. The fibres may be of natural or synthetic origin and may be staple fibres, continuous fibres or fibres produced directly at the processing location. Commonly available fibres have diameters in the range from approximately 0.0001 mm to approximately 0.2 mm and are supplied in several forms: short fibres (known also as staple or chopped fibres), continuous individual fibres (filaments or monofilaments), untwisted bundles of continuous fibres (known also as tow) and twisted bundles of continuous fibres (yarn). A nonwoven textile can be produced using many methods, including technologies such as meltblown, spunbond, spunmelt, spinning from solvents, electrostatic spinning (electrospinning), carding, film fibrillation, melt-film fibrillation, airlaying, dry-laying, wetlaying with staple fibres and various combinations of these processes as known in the art. The basis weight of nonwoven textiles is usually expressed in grams per square metre (gsm).
The term "asymmetry" when used with respect to the perpendicular plane of the fibre cross-section means that the arrangement of the fibre sections is not symmetrical, particularly respective to the central symmetry, where the centre is considered to be the centre of the fibre cross-section. The term may also relate to axial symmetry, where it is necessary to assess at least as many axes passing through the centre of the cross-section of the fibre as there are polymer sections present.
The term "heat" is understood to mean "melting heat" or "crystallisation heat" and is always understood to mean "latent heat".

Description of preferred embodiments

According to this invention a batt may consist of continuous multicomponent fibres produced for example from spunmelt process. Fibres are extruded under a spinneret and subsequently attenuated, cooled and laid down on a belt so as to form a batt of fibres. During the course of the process these fibres will curl automatically. The batt may be converted to the nonwoven fabric.
The individual fibres consist of at least two polymer components A and B, where the polymer components are delivered to the spinneret separately and in the resulting fibre there is a section with a predominance of the A polymer component and a section with a predominance of the B polymer component and wherein the sections in the cross-section of the fibre are arranged in a manner that supports the crimping of the fibres already during the course of the setting process of the fibre. These areas can, for example, be found on the opposite sides of the fibre cross-section and so form an arrangement known in bicomponent fibres under the name side-by-side or, for example, one section may surround the second section and so form an arrangement know as core-sheath, where for the purpose of ensuring the crimping of the fibre, the overall arrangement of both sections with predominant polymeric components A,B is asymmetrical in cross-section. In another arrangement, the fibre may contain three polymer sections with predominant polymer components A, B, C arranged, for example in the arrangement known as "segmented pie" or "islands-in-the-sea", where for the purpose of ensuring the crimping of the fibre, the overall arrangement of both sections with predominant material components A,B is asymmetrical in the cross-section.
Without intent to be bound by theory, it is believed that the mutual arrangement of the sections with predominant polymer components in the cross-section of the fibre modified to support crimping of fibres is already, during the course of the fibre setting, expressed, for example by the degree of asymmetry of the polymer components, which significantly affect the final crimping result, while it is not possible to simply assume that a greater asymmetry of fibre arrangement will result in more pronounced crimping. On the contrary, it is necessary to also take into consideration the properties of the individual components, where arrangement synergies may arise and a fibre with a less pronounced asymmetrical arrangement may foster greater crimping than a fibre with a more pronounced degree of asymmetry. A person skilled in the field will appreciate that the optimal arrangement of sections with predominant polymer compoment in the fibre can be determined in a laboratory test, for example, using a small laboratory spinneret. Examples of the individual asymmetrical arrangements and examples of arrangements supporting fibre crimping, not limited to those presented here, are shown in fig. 1A. The arrangements that - based on the above provided definition - are not asymmetrical or generally do not support fibre crimping are shown in fig. 1B.
The formation of crimped fibres resulting from a significant difference in the properties of the individual polymer components, commonly expressed using the so-called contractibility of individual components is well known in the industry. Fibres produced in this way are known under the name of chemically formed fibres. A person skilled in the art will appreciate that the term component contractibility describes primarily the volume change during the transition from the liquid to the solid state, which is affected by the various properties of the polymers. For example, for a bicomponent fibre it is possible to use the combination of two polymers. For example one polymer together with another polymer (polypropylene + polyethylene), copolymers (polypropylene + polypropylene copolymer) or a blend (polypropylene + polypropylene blend and a polypropylene copolymer). When using two polymers it is always necessary to very carefully consider the used materials and their mutual miscibility. The more they differ from each another, the more probable is a lower level of cohesion of both sections with predominant polymer component in the fibre and splitting of the fibre may occur. Especially in hygiene applications even a small degree of fibre splitting is very undesirable as it may manifest itself as "fuzz balls" on the surface of the textile and so appear on the surface of the product, which the end customers see as a sign of an inferior quality product. It is also known that the same polymer with differing properties (for example a difference in the melt flow index, polydispersion, degree of crystallinity of the material or its elasticity) may be used, where for success it is essential to have a significant difference in at least one of the parameters.
For example, based on the European patent EP1129247 from Kimberly Clark, in the case of polydispersion a difference of at least 0.5 is necessary in the precisely determined area - the document indicates that predominant component of one has a polydispersion of <2.5 and the second >3, for crystallinity it is necessary that predominant component of one section is amorphous and the other is crystalline, while the difference in the melting heat must be at least 40 J/g; while the melt flow index suitable for spunmelt applications is in the range from single digits to thousands of g/10min and for elasticity a combination of elastic and non-elastic material is required.
The subject of this invention is crimped multicomponent fibre where the used polymers predominant in sections are very similar to each other. Preferably the polymers can be chemically the same, just a bit differ in physical properties, e.g. polypropylene-polypropylene combination. A person skilled in the art will appreciate, that for example polypropylene (polymer made from propylene monomer units) have basic characteristics, but for example tacticity of single units, or length of polymer chains or distribution of different polymer chains in polymer can bring variability in physical properties, that is significant for fiber and nonwoven production. A person skilled in the field will appreciate the wide range of commercial types of polymers available on the market and will also appreciate the various amounts and availability of the individual types. Due to the distribution in demand, the offer is also concentrated particularly at polymers in a relatively narrow area of properties. A considerable advantage arising from the use of significantly similar polymers is also that they are relatively readily available on the market.
It is necessary to stress that the mentioned polymer sections may be formed using one polymer or may be formed using a blend of various compounds. It is known in the industry that there also exist fibres consisting of multicomponent fibres based on the same polymer, the components differing only in the addition of an admixture. For example US file 6,203,905 from Kimberly Clark describes the addition of a nucleation additive into one section of the bicomponent fibre.
The principle of our invention may consists of predominant polymeric components only or of predominant components and added additives.
The principle of our invention may also contain the addition of additives (for example dyes), but the addition of such an additive does not affect the crimping of fibres to a significant degree. The additive may, for example, be added to both sections symmetrically.
As is known in the industry, some functional additives may induce a chemical reaction directly in the polymer melt immediately before spinning and their effectiveness may be affected, for example by the temperature of the melt (for example IRGATEC CR76 from BASF). In this way, by effect of the various temperatures of the melt of both polymer component for sections, a significant difference in the resulting properties (for example melt flow index, polydispersion) may arise even when identical mixtures of polymers and additives are used in both sections. The principle of the invention may contain the addition of functional additives, but this addition does not affect the crimping of fibres to a significant degree.
As is evident from the preceding text, it is known in the industry that if the contractibility of the predominant components of sections is sufficiently different then tension arises in the fibre under the spinneret causing crimping. The crimping of fibres based on the invention results from the combination of small differences in at least two, preferably three parameters of the polymer.
The key variable is the latent heat of crystallisation (dHc), which is an indicator of the amount of energy that it is necessary to take from the system in order for the crystallisation of the polymer components to occur. A well-known theory states that if the temperature difference is sufficient then predominant component in one section will start setting first, and as such created tension has no opposing force in the form of still liquid predominant component in the second section, the fibre will curl. It is always necessary to have a sufficient difference between both polymer components otherwise the effect will not take place.
A known document Kimberly-Clark EP0685579 determines the minimum difference in the melting heat, which equates approximately to a crystallisation heat of 40 J/g. In contrast, according to the invention, the crimping of the fibres occurs at smaller differences, when a surprisingly significant synergistic effect of other differences between the predominant component in sections is taken advantage of. The curling or crimping of fibres based on the invention results from the combination of small differences in the crystallisation heat (dHc) and in at least one, preferably two more parameters of the polymer.
The individual predominant components differ in the heat of crystallisation (dHc), where the difference in the values is in the range of 30 J/g to 10 J/g, and preferably 30 J/g to 20 J/g. For lower degree of crimping the heat of crystallisation difference (dHc) can be in the range of 24 J/g to 10 J/g, and preferably 24 J/g to 20 J/g.Furthermore, the individual predominant components may differ in the melt flow index (MFI) level, where the difference between the values is in the range of approximately 100g/10min to 5g/10min, better yet 80g/10min; preferably 60g/10min to 10g/10min.
The individual predominant components may, furthermore, differ in the degree of the material's polydispersion, where the difference in the values is in the range 1 to 0.3, better yet 1 to 0.5 and preferably 1 to 0.75.
The individual predominant components may, furthermore, differ in the flexural modulus of the material, where the difference in the values is in the range 300 MPa to 50 MPa, better yet 250 MPa to 80 MPa and preferably 200 MPa to 80 MPa.

Without need to be bound by theory we assume that the curling of the fibre is caused by the tension in the fibre, when one section is already crystalline, while the other remains in the liquid state or that its degree of crystallisation is lower at that given point in time. In general, during the course of crystallisation the volume of the given section becomes smaller and if at that given time the other section is still malleable, it does not present a very large level of resistance and the fibre curls. From the above mentioned it may appear that apart from the value of the latent heat of crystallisation (dHc) itself, also the temperature at which crystallisation commences and the speed of the crystallisation may also have an effect on the degree of curling. Respecting the fact that the subject of the invention is the combination of two significantly similar polymers, they will probably also have similar crystallisation temperatures. Examples of various commercial types of homopolymers of polypropylene are shown in the table.

Polymer / manufacturer	Crystallisation temperature °C.	Latent heat of crystallisation (dHc) J/g	Crystallisation speed (min)
Mosten NB425 from Unipetrol	124	108	1.36
Tatren HT2511 from Slovnaft	125	106	0.77
MR 2002 from Total Petrochemicals	114	85	5.29
Achieve 3854 from Exxon	113	91	8.19
Moplen HM562S from Basel	121	87	1.55

Without need to be bound by theory we assume that the differences in the crystallisation time in the order of several minutes do not have significant force in themselves to cause curling in the fibres, but also contribute to the degree of curling caused by the above mentioned differences, namely in the latent heat of crystallisation (dHc).
The individual predominant components of sections may differ in the crystallisation temperature, where the difference in the values is in the range of approximately 5-30°C, better yet 5-25°C and preferably 8-25°C.
The individual predominant components of sections may differ in crystallisation speed, where the difference in the values is at least 20 seconds, better yet 50 seconds, better yet 120 seconds and preferably 150 seconds.
The polymer components are dosed (1) into separate extrusion systems (2), where they are melted, heated to a suitable operating temperature and still separated brought to the spinnerets (4) where the multicomponent fibre is formed. A person skilled in the art will understand that the process for preparing polymers for spinning in the form of a multicomponent fibre may, depending on the type of technology encompass further specific steps, as well as the fact that various additives designed for this purpose may be added to the polymer components for the purpose of for example changing the colour of the fibres (dyes) or to change the properties of the fibres (for example hydrophilicity, hydrophobicity, inflammability), where according to the invention it is significant for the material that these additive do not affect the crimping of fibres and/or they are dispersed symmetrically in the resulting fibre. The fibre (5) formed under the spinneret (8) is exposed to a stream of cooling and attenuating air (6,7), so crimps form on the fibres before they fall (8) on to the collecting mat (10). Both cooling and attenuating air (6,7) has approximately the room temperature, preferably 10-30°C, more preferably 15-25°C. The collecting mat (10) may, for example, be a moving belt that carries away the forming fibre batt (11). During the way on collecting mat (10) there is no extra heat or mechanical energy entrance to support the crimping.
In this way, several spinning beams can be arranged in sequence, where they all may produce crimped fibres or may lay different layers (e.g. simple spunmelt fibres - e.g. spunbond or meltblown, nanofibres, a film). For the design according to the invention, it is advantageous if the layer/layers of crimped fibres are laid down on other layers so that undesirable compression of the crimped fibres does not occur. For other applications it might be advantageous to perform combinations where crimped fibres are released from the first and last spinning beams so that the resulting material has the outer surfaces consisting of crimped fibres and the inner layer can have different properties (for example mechanical strength of the resulting nonwoven textile).
The layer or layers of fibres are subsequently strengthened (12), where several known methods may be used (for example thermal bonding, thermal calender bonding, needle punching, hydroentanglement). The individual bonding methods have a significant effect on the resulting properties of the materials and a person skilled in the field will easily determine which method is suitable for their material. Likewise, this skilled person will also understand that the selection of a bonding method with a higher intensity or bonding point density may result even in negating the differences in the overall bulkiness of the resulting nonwoven textile containing fibres based on the invention and standard materials containing non-crimped fibres.
Final nonwoven web, can be used at various applications as for non limited list of following examples: both dusting and hygiene wipes including wet wipes; parts of furniture; parts of household equipment including for example tablecloth, counterplead, covering material; parts of hygiene absorbent articles for all babies, femcare and adult inco as for example it can create or be part of nonwoven landing zone, ADL (Acquisition Distribution Layer), backsheet, topsheet, side panels, core wrap, leg cuffs.

Examples

Example 1: design based on the invention

A batt consist of continuous bicomponent fibres, where one component consists of polypropylene MR 2002 from Total Petrochemicals and the second component consists of polypropylene Mosten NB425 from Unipetrol. Both polypropylene homopolymer materials are readily available on the market, both are inelastic and crystalline.

	MR 2002 from Total Petrochemicals	difference	Mosten NB425 from Unipetrol
Melt flow index (MFI) (g/10 min)	15	10	25
Polydispersion (PDI)	2.6	0.8	3.4
Latent heat of crystallisation (dHc J/g)	85.00 J/g	23.1 J/g	108.1 J/g
Flexural modulus of the material	1300 MPa	100 MPa	1400 MPa

The fibres were produced on a Reicofil 3 production line for spunmelt nonwoven textiles and removed from the lied batt prior to the bonding of the material.

Example 1A:

Continuous bicomponent fibre was of the side-by-side type and the individual sections were formed in the weight ratio 40: 60. First section consists of polypropylene MR 2002 and second section consist of polypropylene Mosten NB425.
The average degree of crimping achieved was 13.4 crimps / 20 mm.

Example 1B:

Continuous bicomponent fibre was of the side-by-side type and the individual sections were formed in the weight ratio 30:70. First section consists of polypropylene MR 2002 and second section consist of polypropylene Mosten NB425.
The average degree of crimping achieved was 15.8 crimps / 20 mm.

Example 1C:

Continuous bicomponent fibre was of the side-by-side type and the individual sections were formed in the weight ratio 65: 35. First section consists of polypropylene MR 2002 and second section consist of polypropylene Mosten NB425.
The average degree of crimping achieved was 8.2 crimps / 20 mm.

Example 1D:

Continuous bicomponent fibre was of the side-by-side type and the individual sections were formed in the weight ratio 50: 50. First section consists of polypropylene MR 2002 and second section consist of polypropylene Mosten NB425.
The average degree of crimping achieved was 11.7 crimps / 20 mm.

Example 2: design based on the invention

A batt consist of continuous bicomponent fibres, where one component consists of polypropylene MR 2002 from Total Petrochemicals and the second component consists of polypropylene Tatren HT2511 from Slovnaft. Both polypropylene homopolymer materials are readily available on the market, both are inelastic and crystalline.

	MR 2002 from Total Petrochemicals	difference	Tatren HT2511 from Slovnaft
Melt flow index (MFI) (g/10 min)	15	10	25
Polydispersion (PDI)	2.6	0.1	2.7
Latent heat of crystallisation (dHc J/g)	85.00 J/g	21 J/g	106.0 J/g
Flexural modulus of the material	1300 MPa	100 MPa	1400 MPa

Example 2A:

Continuous bicomponent fibre was of the side-by-side type and the individual sections were formed in the weight ratio 30: 70. First section consists of polypropylene MR 2002 and second section consist of polypropylene Tatren HT2511.
The average degree of crimping achieved was 15.9 crimps / 20 mm.

Example 2B:

Continuous bicomponent fibre was of the side-by-side type and the individual sections were formed in the weight ratio 40:60. First section consists of polypropylene MR 2002 and second section consist of polypropylene Tatren HT2511.
The average degree of crimping achieved was 12.8 crimps / 20 mm.

Example 2C:

Continuous bicomponent fibre was of the side-by-side type and the individual sections were formed in the weight ratio 50:50. First section consists of polypropylene MR 2002 and second section consist of polypropylene Tatren HT2511.
The average degree of crimping achieved was 12.0 crimps / 20 mm.

Example 2D:

Continuous bicomponent fibre was of the side-by-side type and the individual sections were formed in the weight ratio 70: 30. First section consists of polypropylene MR 2002 and second section consist of polypropylene Tatren HT2511.
The average degree of crimping achieved was 7.3 crimps / 20 mm.

Example 3: design based on the invention - lab line

A batt consists of continuous bicomponent fibres, fibers produced on a laboratory spinning line with compressed air filament attenuating up to 0,9 MPa, spinning die with 12 holes, hole diameter 0,5 mm, hole length 0,8 mm. Extrusion system with two independent extruders (diameter 16 mm). Line throughput 0,5 gram per minute per hole. Line is available for example at Research Institute for Man-Made Fibres "VUCHV a.s. Svit", Slovak Republik.

Example 3A

Continuous bicomponent fibre was of the side-by-side type and the individual sections were formed in the weight ratio 40: 60. First section consists of polypropylene MR 2002 and second section consist of polypropylene Tatren HT2511. Attenuating air pressure was 0,85 MPa.

Example 3B

Continuous bicomponent fibre was of the side-by-side type and the individual sections were formed in the weight ratio 40: 60. First section consists of polypropylene MR 2002 and second section consist of polypropylene Mosten NB425. Attenuating air pressure was 0,85 MPa.

	Predom. polymer in first section	Predom. polymer in first section 3A	Predom. polymer in first section 3B	difference 3A	difference 3B
Material	MR 2002	Mosten NB425	Tatren HT2511	Mosten / MR 2002	Tatren / MR 2002
Melt flow index (MFI) (g/10 min)	25	15	25	10	0
Polydispersion (PDI)	3,4	2,6	2,7	0,8	0,7
Latent heat of crystallisation (dHc J/g)	108,1	85	106	23,1	2,1
Flexural modulus of the material	1400	1300	1400	100	0
Fiber properties				3A	3B
fiber thickness (dtex) STN EN ISO 1973				2,2	2
Tensile (cN/dtex) STN EN ISO 5079				2,7	2,8
Elongation (%) STN EN ISO 5079				393,5	376,3
Degree of crimping (crimps per 20 mm fiber)				14,5	14,5

Example 4: design based on the invention - including calendering

Continuous bicomponent fibre was of the side-by-side type and the individual sections were formed in the weight ratio 40: 60. First section consists of polypropylene MR 2002 and second section consist of polypropylene Tatren HT2511. Both polypropylene homopolymer materials are readily available on the market, both are inelastic and crystalline.

The fibres were produced on a Reicofil 4 SSS production line for spunmelt nonwoven textiles.
Attenuating air temperature 15-25°C °C, cabine pressure in the area 2800-3200 Pa. The batt was thermobonded using pair of smooth-gravure rolls with Ungricht design U2888M (standard oval). Smooth roll temperature 170-180°C, gravure roll temperature 160-170°C, nip 120-125 daN/cm.
The fibers removed from the lied batt prior to the bonding of the material had the average degree of crimping 15.7 crimps / 20 mm.
Final material properties:

Testing methodology

"Degree of crimping" of the fibre is measured using the method described in the norm
SN 80 0202 from 1969. Measurement is performed on individual fibres under standard conditions (an individual fibre is loosely placed on a mat for 24 hours at a temperature of 20°C and at a relative humidity of 65%). The fibre is subsequently hung vertically and subject to a strain of 0.0076g (for a fibre with a fineness of 1-5 den, i.e. 0.111 - 0.555 tex). The number of crimps is counted on a length of 20 mm.
"Polydispersion" of a polymer or also the "coefficient of polydispersion (PDI)" expresses the heterogeneity of a material. It is identified by a calculation of the numerical (Mn) and the weight (Mw) average molar weight of the polymer, where PDI = Mw/Mn, as described for example at Modern Physical Organic Chemistry from Eric V. Anslyn and Dennis A. Dougherty.
"Melt flow index (MFI)" of a polymer is measured using a testing methodology according to the German norm ASTM D1238-95; the specific test conditions (e.g. temperature) vary for the individual polymers - for example the test conditions for polypropylene are 230/2.16 and for polyethylene they are 190/2.16.
"Flexural modulus" of a polymer is measured using the testing methodology described in ISO 178:2010.
"Crystallinity", "latent heat of crystallisation", "temperature of crystallisation" and the "melting temperature" are measured using the testing methodology describe in ASTM D3417 using DSC, where the speed in the temperature is 2°C/min in the measured range of 200 - 80°C and the sample volume is 7-7.4g.
"Speed of crystallisation" of a polymer is measured using the ISO 11357-7-Determination of crystallization kinetics - isothermal crystallisation method, where a sample is first kept at the melt temperature of 210°C for 8 minutes and subsequently cooled to 120°C.

Industrial applicability of the invention

The batt produced according to the invention are applicable namely for the production of nonwoven textiles, where they can form a production step on an online production line. The nonwoven textile produced from the batt made according to the invention is widely applicable in various fields, namely in hygiene products such a baby diapers, feminine absorptive products or incontinence products. Crimped fibres create a fluffiness in the textile meaning that the material can be advantageously used both in applications requiring softness and silkiness (for example parts of absorptive products, which are in direct contact with the user's skin) and in applications requiring bulkiness (wipes, loop side in the "hook and loop" system .).

Claims

A batt comprising crimped bi- or multicomponent fibres consisting of at least two sections, which comprise a polymer or polymer blend as a predominant component and which are arranged across the cross-section of the fiber in a way suitable to promote crimping of the fibre during the setting process and which predominant components differ in the crystallisation heat (dHc), characterised in that the difference in the crystallisation heat dHc is in the range from 30 J/g to 10J/g, preferably 30 J/g to 20 J/g and that the predominant components differ in at least one of the other parameters selected from the group of melt flow index, degree of polydispersion and flexural modulus, while the relative difference of the predominant components is:
for the flow index in the range from 100g/10min to 5g/10min and/or

for the degree of polydispersion less than 1, but above 0.3, and/or

for the flexural modulus in the range from 300 MPa to 50 MPa;
where the relative difference in the melt flow index is not greater than 100g/10min, in the degree of polydispersity is less than 1, in flexural modulus is not greater than 300 MPa; and where said fibres have the degree of crimping at least 5 crimps per 20 mm of fibre.
A batt comprising crimped fibres according to claim 1, wherein the relative differentiation of the predominant components in the melt flow index is in the range of 80g/10min to 5g/10min, preferably 60g/10min to 10g/10min.
A batt comprising crimped fibres according to claim 1 or 2, wherein the relative differentiation of the predominant components in the degree of polydispersion is in the range of 1 to 0.5, preferably 1 to 0.7.
A batt comprising crimped fibres according to any of the preceding claims, wherein the relative differentiation of the predominant components in the flexural modulus is in the range of 250 MPa to 80 MPa, preferably 200 MPa to 80 MPa.
A batt comprising crimped fibres according to any of the preceding claims, wherein the fibres are bicomponent fibres of the side-by-side type.
A batt comprising crimped fibres according to claim 5, wherein both predominant components of the bicomponent fibres are a propylene homopolymer.
A batt comprising crimped fibres according to any of the preceding claims, wherein said predominant components are arranged across the cross-section of the fibres, centrally asymmetrically and/or axially asymmetrically relative to a number of axes passing through the centre of the fibre's cross-section, which evens the number of the polymer sections in the fibre.
A batt according to any of the preceding claims, wherein the fibers comprise an additive, wherein the additive is present in the components such that it does not affect the crimping of the fiber to a significant degree.
A nonwoven textile characterised in that it comprises the batt according to any of the preceding claims.
The nonwoven textile according to claim 9 wherein the nonwoven textile is of a spunmelt type.
A method of producing a batt comprising multicomponent fibres, wherein the method comprises the following steps:
i. preparing at least two materials comprising a polymer or polymer blend as a predominant component the materials being suitable for the formation of fibres;

ii. then forming multicomponent fibres from the prepared materials under a spinneret, namely multicomponent fibres comprising said materials arranged in sections, which are arranged across the cross-section of the fiber in a way suitable to promote crimping of the fibre during the setting process, and cooling and attenuating the fibres by cooling and attenuating air; and

iii. forming a batt from said multicomponent fibres;
characterised in that:
said predominant components in sections are selected such that they differ in the heat of crystallisation dHc in the range from 30 J/g to 10J/g, preferably 30 J/g to 20 J/g and that they differ in at least one other parameter selected from the group of melt flow index, degree of polydispersion and flexural modulus, where the relative differentiation of the polymer components is:
for the flow index in the range from 100g/10min to 5g/10min and/or

for the degree of polydispersion in the range from 1 to 0.3, and/or

for the flexural modulus in the in the range from 300 MPa to 50 MPa;

wherein the relative difference in the melt flow index is no greater than 100g/10min, in the degree of polydispersity is no greater than 1, in the flexural modulus is no greater than 300 MPa; and
wherein said fibres have the degree of crimping at least 5 crimps per 20 mm of fibre.
The method according to claim 11, wherein said sections with predominant components are arranged across the cross-section of the fibre centrally asymmetricaly and/or axially asymmetricaly relative to a number of axes passing through the centre of the cross-section of a fibre, which evens the number of present sections in the fibre.
The method according to claim 11, wherein said multicomponent fibres are bicomponent fibres of the side-by-side type.
The method according to claim 11, wherein said polymer sections contain as their predominant component a polypropylene homopolymer.