Biologically Degradable MULTI-COMPONENT POLYMER FIBRES

Abstract

The invention relates to a biologically degradable multi-component polymer fibre, in particular bi-component fibres, with advantageous physical properties, to a process for its production, as well as to its use.

Claims

1. A multi-component polymer fibre containing (i) at least one component A and at least one component B, (ii) the component A comprising a thermoplastic polymer A, (iii) the component B comprising a thermoplastic polymer B, characterized in that (iv) the component A additionally has at least one additive A which increases the biological degradability of the multi-component fibre and the component B does not have an additive B which increases the biological degradability of the multi-component fibre, or (v) the component B additionally has at least one additive B which increases the biological degradability of the multi-component fibre and the component A does not have an additive A which increases the biological degradability of the multi-component fibre, or (vi) the component A additionally has at least one additive A and the component B additionally has at least one additive B which together increase the biological degradability of the multi-component fibre, with the proviso that when (i) the thermoplastic polymer A and the thermoplastic polymer B are identical, the additives A and B are different, or (ii) when the additives A and B are identical, thermoplastic polymer A and thermoplastic polymer B are different, said multi-component polymer fibre has an increased biological degradability compared with a multi-component fibre without the additives A and/or B, and the biological degradability is determined in accordance with at least one method selected from the group: (i) ASTM D5338-15 (2021) Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials Under Controlled Composting Conditions, Incorporating Thermophilic Temperatures (DOI: 10.1520/D5338-15R21) ASTM International, West Conshohocken, PA, 2015, www.astm.org), (ii) ASTM D6400-12 (Standard Specification for Labeling of Plastics Designed to be Aerobically Composted in Municipal or Industrial Facilities) (DOI: 10.1520/D6400-12), iii) ASTM D5511 (ASTM D5511-11 Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under High-Solids Anaerobic-digestion Conditions (DOI: 10.1520/D5511-11) and ASTM D5511-18 Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under High-Solids Anaerobic-digestion Conditions; (DOI: 10.1520/D5511-18)), (iv) ASTM D6691 (ASTM D6691-09 Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials in the Marine Environment by a Defined Microbial Consortium or Natural Sea Water Inoculum) (DOI: 10.1520/D6691-09) and ASTM D6691-17, Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials in the Marine Environment by a Defined Microbial Consortium or Natural Sea Water Inoculum (DOI: 10.1520/D6691-17)), (v) ASTM D5210-92 (Anaerobic Degradation in the Presence of Sewage Sludge) (DOI: 10.1520/D5210-92), (vi) PAS 9017:2020 (PlasticsBiodegradation of polyolefins in an open-air terrestrial environmentSpecification), ISBN 978 0 539 17478 6; 2021 Oct. 31, (vii) ASTM D5988 (ASTM D5988-12 Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials in Soil) (DOI: 10.1520/D5988-12), ASTM D5988-18 Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials in Soil (DOI: 10.1520/D5988-18), ASTM D5988-03 Standard Test Method for Determining Aerobic Biodegradation in Soil of Plastic Materials or Residual Plastic Materials After Composting (DOI: 10.1520/D5988-03)), (viii) EN 13432:2000-12 PackagingRequirements for packaging recoverable through composting and biodegradationTest scheme and evaluation criteria for the final acceptance of packaging; German version EN 13432:2000 (DOI: 10.31030/9010637), (ix) ISO 14855-1:2013-04 (DOI: 10.31030/1939267) and ISO 14855-2:2018-07 (ICS 83.080.01) Determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions (Method by analysis of evolved carbon dioxide), (x) EN 14995:2007-03PlasticsEvaluation of compostability (DOI: 10.31030/9730527) or (xii) ISO 17088:2021-04 (Specifications for compostable plastics) (ICS 83.080.01).

2. The multi-component polymer fibre as claimed in claim 1, characterized in that the thermoplastic polymer A and/or the thermoplastic polymer B is/are selected from the group: (i) acrylonitrile-ethylene-propylene-(diene)-styrene copolymer, acrylonitrile-methacrylate copolymer, acrylonitrile-methylmethacrylate copolymer, chlorinated acrylonitrile, polyethylene-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-ethylene-propylene-styrene copolymer, cellulose acetobutyrate, cellulose acetopropionate, hydrated cellulose, carboxymethylcellulose, cellulose nitrate, cellulose propionate, cellulose triacetate, polyvinyl chloride, ethylene-acrylic acid copolymer, ethylene-butylacrylate copolymer, ethylene-chlorotrifluoroethylene copolymer, ethylene-ethlyacrylate copolymer, ethylene-methacrylate copolymer, ethylene-methacrylic acid copolymer, ethylene-tetrafluoroethylene copolymer, ethylene-vinyl alcohol copolymer, ethylene-butene copolymer, ethylcellulose, polystyrene, polyfluoroethylene-propylene, methylmethacrylate-acrylonitrile-butadiene styrene copolymer, methylmethacrylate-butadiene-styrene copolymer, methylcellulose, polyamide 11, polyamide 12, polyamide 46, polyamide 6, polyamide 6-3-T, polyamide 6-terephthalic acid copolymer, polyamide 66, polyamide 69, polyamide 610. polyamide 612, polyamide 61, polyamide MXD 6, polyamide PDA-T, polyamide, polyarylether, polyaryletherketone, polyamideimide, polyarylamide, polyamino-bis-maleimide, polyarylate, polybutene-1, polybutylacrylate, polybenzimidazole, poly-bis-maleimide, polyoxadiazobenzimidazole, polybutylterephthalate, polycarbonate, polychlorotrifluoroethylene, polyethylene, polyestercarbonate, polyaryletherketone, polyetheretherketone, polyetherimide, polyetherketone, polyethylene oxide, polyarylether sulphone, polyethylene terephthalate, polyimide, polyisobutylene, polyisocyanurate, polyimide sulphone, polymethacrylimide, polymethacrylate, poly-4-methylpentene, polyacetal, polypropylene, polyphenyl oxide, polypropylene oxide, polyphenylene sulphide, polyphenylene sulphone, polystyrene, polysulphone, polytetrafluoroethylene, polyurethane, polyvinyl acetate, polyvinyl alcohol, polyvinylbutyral, polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polyvinyl fluoride, polyvinyl methyl ether, polyvinylpyrrolidone, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid anhydride copolymer, styrene-maleic acid anhydride-butadiene copolymer, styrene methyl methacrylate copolymer, styrene-methyl styrene copolymer, styrene-acrylonitrile copolymer, vinyl chloride-ethylene copolymer, vinyl chloride-methacrylate copolymer, vinyl chloride-maleic acid anhydride copolymer, vinyl chloride-maleimide copolymer, vinyl chloride-methylmethacrylate copolymer, vinyl chloride-octyl acrylate copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-vinylidene chloride-acrylonitrile copolymer and/or (ii) synthetic biopolymer.

3. The multi-component polymer fibre as claimed in claim 2, characterized in that the synthetic biopolymers may be one or more aliphatic, araliphatic polyesters or copolyesters which are produced from polyols, and aliphatic and/or aromatic dicarboxylic acids or their derivatives (anhydrides, esters) by polycondensation, wherein the polyols may be substituted or unsubstituted, and the polyols may be linear or branched polyols.

4. The multi-component polymer fibre as claimed in claim 3, characterized in that (i) the polyols contain 2 to 8 carbon atoms, (ii) the aliphatic dicarboxylic acids comprise substituted or unsubstituted, linear or branched, non-aromatic dicarboxylic acids selected from the group formed by aliphatic dicarboxylic acids containing 2 to 12 carbon atoms and cycloaliphatic dicarboxylic acids containing 5 to 10 carbon atoms, wherein the cycloaliphatic dicarboxylic acids may also contain heteroatoms in the ring, (iii) the aromatic dicarboxylic acids comprise substituted or unsubstituted, aromatic dicarboxylic acids selected from the group formed by aromatic dicarboxylic acids containing 6 to 12 carbon atoms, wherein these carboxylic acids may also comprise heteroatoms in the aromatic ring and/or in the substituents, (iv) the substituted aromatic dicarboxylic acids contain 1 to 4 substituents selected from halogens, C6-C10 aryl and C1-C4 alkoxy.

5. The multi-component polymer fibre as claimed in claim 1, characterized in that the synthetic biopolymer is selected from the group formed by aliphatic polyesters with repeat units of at least 4 carbon atoms, for example polyhydroxyalkanoates such as polyhydroxyvalerate and polyhydroxybutyrate-hydroxyvalerate copolymer, polycaprolactone, furan dicarboxylic acid, and succinate-based aliphatic polymers (for example polybutylene succinate, polybutylene succinate adipate and polyethylene succinate). Special examples may be selected from polyethylene oxalate, polyethylene malonate, polyethylene succinate, polypropylene oxalate, polypropylene malonate, polypropylene succinate, polybutylene oxalate, polybutylene malonate, polybutylene succinate and blends and copolymers of these compounds.

6. The multi-component polymer fibre as claimed in claim 1, characterized in that the synthetic biopolymer is an aliphatic polyester comprising repeat units of lactic acid (PLA), hydroxy fatty acid (PHF) (also known as polyhydroxyalkanoate PHA), in particular hydroxybutanoic acid (PHB) and succinate-based aliphatic polymers, for example polybutylene succinate, polybutylene succinate adipate and polyethylene succinate).

7. The multi-component polymer fibre as claimed in claim 1, characterized in that the thermoplastic polymer A and/or B has a glass transition temperature in the range 125 C. to 200 C., in particular in the range 125 C. to 100 C.

8. The multi-component polymer fibre as claimed in claim 1, characterized in that the thermoplastic polymer A and/or B has a melting temperature in the range 120 C. to 285 C., in particular in the range 150 C. to 270 C., particularly preferably in the range 175 C. to 270 C.

9. The multi-component polymer fibre as claimed in claim 1, characterized in that the thermoplastic polymer A and/or B is/are selected from the group formed by polylactic acids (PLA) as well as their copolymers, polyhydroxy fatty acid esters (PHF) as well as their copolymers, as well as blends of said polymers.

10. The multi-component polymer fibre as claimed in claim 1, characterized in that at least the thermoplastic polymer A and/or the thermoplastic polymer B is/are selected from the group formed by melt spinnable synthetic biopolymers, wherein polycondensates and polymerisates from bio-based starting materials are particularly preferred.

11. The multi-component polymer fibre as claimed in claim 1. characterized in that the multi-component polymer fibre is a bi-component fibre in which the component A forms the core and the component B forms the shell and the melting point of the thermoplastic polymer in component A is at least 5 C., preferably at least 10 C., higher than the melting point of the thermoplastic polymer in component B.

12. The multi-component polymer fibre as claimed in claim 1, characterized in that the fibre has (i) at least one additive A in the component A or (ii) at least one additive B in the component B or (iii) at least one additive A in the component A and at least one additive B in the component B, with the proviso that the additive A and the additive B are different or insofar as at least one additive A is present in the component A and at least one additive B is present in the component B, the additive A and the additive B may also be identical, when the thermoplastic polymer A and thermoplastic polymer B are different.

13. The multi-component polymer fibre as claimed in claim 1, characterized in that the additives A and B are selected from the group: (i) basic alkali and/or alkaline earth compounds (pH>7 dissolved in water), in particular carbonates, hydrogen carbonates, sulphates, particularly preferably CaCO.sub.3, and alkaline additives, particularly preferably CaO, (ii) aliphatic polyesters, (iii) fatty acid ester, preferably C1-C40-alkyl stearate, more preferred C2-C20-alkyl stearate, most preferred ethyl stearate (iv) sugars, in particular monosaccharides, disaccharides and oligosaccharides, (v) catalysts for transesterification, in particular under basic conditions, (vi) metal compounds, in particular transition metal compounds, as well as their salts, (vii) unsaturated carboxylic acids or their anhydrides/esters/amides, (viii) synthetic rubber, natural rubber, (ix) carbohydrates, in particular starch and/or cellulose, as well as mixtures of the aforementioned substances.

14. The multi-component polymer fibre as claimed in claim 1, characterized in that the additive A has a proportion of the component A which is preferably between 0.005% by weight and 20% by weight, particularly preferably between 0.01% by weight and 5% by weight, with respect to the total weight of the component A and the additive B has a proportion of the component B which is preferably between 0.005% by weight and 20% by weight, particularly preferably between 0.01% by weight and 5% by weight, with respect to the total weight of the component B.

15. The multi-component polymer fibre as claimed in claim 1, characterized in that the fibre is a continuous fibre, preferably a staple fibre, or is a continuous filament, and is preferably a bi-component fibre.

16. A bi-component fibre with a core/shell structure, wherein (i) the component A forms the core and the component B forms the shell of the fibre, (ii) the component A in the core comprises thermoplastic polymer A, (iii) the component B comprises a thermoplastic polymer B, (iv) the melting point of the thermoplastic polymer in the component A in the core is at least 5 C. higher than the melting point of the thermoplastic polymer in the component B in the shell, and preferably the melting point is at least 10 C. higher, characterized in that (v) the component A has a higher biological degradability than the component B; preferably, the component A has at least one additive A, or (vi) the component B has a higher biological degradability than the component A; preferably, the component B has at least one additive B, said biological degradability is determined in accordance with at least one method selected from the group: (i) ASTM D5338-15 (2021) Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials Under Controlled Composting Conditions, Incorporating Thermophilic Temperatures (DOI: 10.1520/D5338-15R21) ASTM International, West Conshohocken, PA, 2015, www.astm.org), (ii) ASTM D6400-12 (Standard Specification for Labeling of Plastics Designed to be Aerobically Composted in Municipal or Industrial Facilities) (DOI: 10.1520/D6400-12), (iii) ASTM D5511 (ASTM D5511-11 Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under High-Solids Anaerobic-digestion Conditions (DOI: 10.1520/D5511-11) and ASTM D5511-18 Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under High-Solids Anaerobic-digestion Conditions; (DOI: 10.1520/D5511-18)), (iv) ASTM D6691 (ASTM D6691-09 Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials in the Marine Environment by a Defined Microbial Consortium or Natural Sea Water Inoculum) (DOI: 10.1520/D6691-09) and ASTM D6691-17, Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials in the Marine Environment by a Defined Microbial Consortium or Natural Sea Water Inoculum (DOI: 10.1520/D6691-17)), (v) ASTM D5210-92 (Anaerobic Degradation in the Presence of Sewage Sludge) (DOI: 10.1520/D5210-92), (vi) PAS 9017:2020 (PlasticsBiodegradation of polyolefins in an open-air terrestrial environmentSpecification), ISBN 978 0 539 17478 6; 2021 Oct. 31, (vii) ASTM D5988 (ASTM D5988-12 Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials in Soil) (DOI: 10.1520/D5988-12), ASTM D5988-18 Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials in Soil (DOI: 10.1520/D5988-18), ASTM D5988-03 Standard Test Method for Determining Aerobic Biodegradation in Soil of Plastic Materials or Residual Plastic Materials After Composting (DOI: 10.1520/D5988-03)), (viii) EN 13432:2000-12 PackagingRequirements for packaging recoverable through composting and biodegradationTest scheme and evaluation criteria for the final acceptance of packaging; German version EN 13432:2000 (DOI: 10.31030/9010637), (ix) ISO 14855-1:2013-04 (DOI: 10.31030/1939267) and ISO 14855-2:2018-07 (ICS 83.080.01) Determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions (Method by analysis of evolved carbon dioxide), (x) EN 14995:2007-03PlasticsEvaluation of compostability (DOI: 10.31030/9730527) or (xi) ISO 17088:2021-04 (Specifications for compostable plastics) (ICS 83.080.01).

17. (canceled)

18. (canceled)

19. The bi-component fibre as claimed in claim 16, characterized in that the additive A and/or additive B is selected from the group formed by (i) basic alkali and/or alkaline earth compounds (pH>7 dissolved in water), in particular carbonates, hydrogen carbonates, sulphates, particularly preferably CaCO.sub.3, and alkaline additives, particularly preferably CaO, (ii) aliphatic polyesters, (iii) fatty acid ester, preferably C1-C40-alkyl stearate, more preferred C2-C20-alkyl stearate, most preferred ethyl stearate, (iv) sugars, in particular mono-saccharides, di-saccharides and oligo-saccharides, (v) catalysts for transesterifications, in particular under basic conditions, (vi) carbohydrates, in particular starch and/or cellulose, as well as mixtures thereof.

20. The bi-component fibre as claimed in claim 16, characterized in that the thermoplastic polymer A and/or the thermoplastic polymer B comprises at least one polyester, with the proviso that the polyester is an araliphatic polyester or copolyester in the case in which the additive A and/or B is an aliphatic polyester.

21. The bi-component fibre as claimed in claim 16, characterized in that the additive A and/or additive B is selected from the group formed by A) basic alkali and/or alkaline earth compounds (pH>7 dissolved in water), in particular carbonates, hydrogen carbonates, sulphates, particularly preferably CaCO.sub.3, and alkaline additives, particularly preferably CaO in combination with catalysts for transesterifications, in particular under basic conditions; B) sugars, in particular mono-saccharides, di-saccharides and oligo-saccharides, in combination with carbohydrates, in particular starch and/or cellulose, as well as mixtures thereof; C) aliphatic polyesters in combination with sugars, in particular mono-saccharides, di-saccharides and oligo-saccharides, or carbohydrates, in particular starch and/or cellulose, D) fatty acid ester, preferably C1-C40-alkyl stearate, more preferred C2-C20-alkyl stearate, most preferred ethyl stearate, as well as mixtures thereof.

22. Use of the multi-component polymer fibre as claimed in claim 1, for the production of a textile fabric.

23. A textile fabric containing the multi-component polymer fibres as claimed in claim 1.

24. A textile fabric as claimed in claim 21, characterized in that the textile fabric is a nonwoven, in particular a wet laid nonwoven or a dry laid nonwoven, preferably based on staple fibres, wherein the nonwoven is preferably consolidated by thermobonding.

25. The textile fabric as claimed in claim 21, characterized in that the textile fabric, in particular the nonwoven, has a basis weight between 10 and 500 g/m.sup.2, preferably 25 to 450 g/m.sup.2, in particular 30 to 300 g/m.sup.2.

Description

EXAMPLE 1

[0340] A polyethylene terephthalate (PET) fibre is spun from a polyethylene terephthalate (PET) resin having the following properties:

[0341] The melt extrusion is done by an extruder having one or more screws at a temperature of 280-290 C. for PET

[0342] Additive A is added at the extruder feed-throat at a level of 2 wt.-% masterbatch dosage. This masterbatch consists of a PET polyester as carrier and the additive, which comprises an aliphatic polyester and CaCO.sub.3.

[0343] The fibre quench occurs by crossflow and air temperature of 40 C.; fibre drawdown speed is 1400 m/min. Spun fiber fineness is 5.4 dtex.

[0344] The fibre drawing is done by single or duo-stage drawing with draw ratio up to 4 and the final dtex is 2.5 dtex. Heat setting is done at 110-130 C.

[0345] The fibre produced is cut into staple fibre having a length of 38 mm.

[0346] The fibre produced is tested in accordance with ASTM D5511 and results are obtained after 208 days:

TABLE-US-00001 3066 - PET Staple Fibre with biodegrative Inculum Negative Positive additive Cumulative Gas 1366.6 1229.3 9867.0 6356.4 Volume (mL) Percent CH.sub.4 (%) 40.7 31.7 37.4 45.5 Volume CH.sub.4 (mL) 556.0 390.1 3693.0 2890.6 Mass CH.sub.4 (g) 0.40 0.28 2.64 2.06 Percent CO.sub.2 (%) 41.0 40.5 43.6 38.0 Volume CO.sub.2 (mL) 560.7 498.1 4306.2 2414.8 Mass CO.sub.2 (g) 1.10 0.98 8.46 4.74 Sample Mass (g) 10 10 10 20.0 Theoretical Sample 0.0 8.6 4.2 12.5 Mass (g) Biodegraded Mass 0.60 0.48 4.29 2.84 (g) Percent Biode- 1.4 87.4 18.0 graded (%) * Adjusted Percent 1.6 100.0 20.6 Biodegraded (%)

[0347] The biodegradation is shown in FIG. 1 versus the control.

EXAMPLE 2

[0348] A bi-component fibre with polyethylene terephthalate (PET) as core (thermoplastic polymer A) and polypropylene (PP) as shell (sheath) (thermoplastic polymer B) is spun from a polyethylene terephthalate (PET) resin and a polypropylene (PP) resin having the following properties:

[0349] The melt extrusion is done by an extruder having one or more screws at a temperature of 270 C. for PET and by another extruder having one or more screws at a temperature at a temperature of 250 C. for PP.

[0350] Additive A is added to the PET at the extruder feed-throat at a level of 2 wt.-% masterbatch dosage. This masterbatch consists of a PET polyester as carrier and the additive, which comprises an aliphatic polyester and CaCO.sub.3.

[0351] Additive B is added to the PP at the extruder feed-throat at a level of 2 wt.-% masterbatch dosage. This masterbatch consists of PP as carrier and the additive, which comprises transition metal compounds and unsaturated carboxylic acids.

[0352] The fibre quench occurs by crossflow and air temperature of 20 C.; fibre drawdown speed is 1000 m/min. Spun fiber fineness is 5.4 dtex.

[0353] The fibre drawing is done by can be single or duo-stage drawing with draw ratio up to 4 and the final dtex is 2.5 dtex. Heat setting is done at 110-130 C.

[0354] The fibre produced is cut into staple fibre having a length of 38 mm and a nonwoven is produced by thermo-bonding.

[0355] A nonwoven thus produced is kept as control in a sealed, evacuated bag and another nonwoven thus produced is tested over a one year period (365 days) at 60 C. and 60% relative humidity.

[0356] The degradation is shown in FIG. 2 a-e versus the control. The degradation of the PP sheath becomes clearly visible. FIG. 2e illustrates the degradation of the PET core as the shape of the fraction changes clearly from the mushroom-shape, which is typical for PET, to a shape indicating that the material has become brittle. In this test the fibers have been axially stressed in a reproducible way (defined speed) by a mechanical testing machine.

[0357] The core of this bico fiber has the same material composition (polymer and additive) as the fiber described in Example 1, where degradation has been proven according to ASTM D5511.

EXAMPLE 3

[0358] A bi-component fibre with polyethylene terephthalate (PET) as core (thermoplastic polymer A) and co-polyethlyene terephthalate (coPET) as shell (sheath) (thermoplastic polymer B) is spun from a polyethylene terephthalate (PET) resin and a co-polyethlyene terephthalate (coPET) resin having the following properties:

[0359] The melt extrusion is done by an extruder having one or more screws at a temperature of 290 C. for PET and by another extruder having one or more screws at a temperature at a temperature of 280 C. for coPET.

[0360] Additive A is added to the PET at the extruder feed-throat at a level of 2 wt.-% masterbatch dosage. This masterbatch consists of a PET polyester as carrier and the additive, which comprises an aliphatic polyester and CaCO.sub.3.

[0361] Additive B is added to the coPET at the extruder feed-throat at a level of 2 wt.-% masterbatch dosage. This additive B is identical to additive A.

[0362] The fibre quench occurs by crossflow and air temperature of 35 C.; fibre drawdown speed is 1200 m/min. Spun fiber fineness is 5.4 dtex.

[0363] The fibre drawing is done by single or duo-stage drawing with draw ratio up to 4.5 and the final dtex is 2.5 dtex. Heat setting is done at 80 C.

[0364] The fibre produced is cut into staple fibre having a length of 38 mm and a nonwoven is produced by thermo-bonding.

[0365] The resulting fiber meets all requirements imposed. The core of this bico fiber has the same material composition (polymer and additive) as the fiber described in Example 1, where degradation has been proven according to ASTM D5511. The sheath differs in that the melting point of the copolyester is lower than the polyester of the core, which renders possible to use the fiber for thermobonded nonwovens.