Biologically Degradable Polymer Fibre Made of Renewable Raw Materials

Abstract

The invention relates to a biologically degradable polymer fibre made of renewable raw materials with good physical properties, as well as a method for its production and its use.

Description

The invention relates to a biologically degradable polymer fibre made of renewable raw materials with good physical properties, as well as a method for its production and its use.

Polymer fibres, i.e. fibres based on synthetic polymers, are produced industrially in large volumes. For this, the underlying synthetic polymer is processed in a fusion spinning process. In this process, thermoplastic, polymer material is melted and led into a spinning beam in the liquid state by means of an extruder. The melted material is then led from this spinning beam into so-called spinning nozzles. The spinning nozzle usually has a spinning nozzle having multiple drill holes from which the individual capillaries (filaments) of the fibres are stretched. Besides the fusion spinning procedure, also the wet or solvent spinning methods are used for the production of spinning fibres. For this, instead of the melted mass, a highly viscous solution of a synthetic polymer is stretched through nozzles having fine drill holes. A person skilled in the art refers to both methods as so-called multi-stage spinning procedure.

The polymer fibres produced this way are used for textile and/or technical applications. It is beneficial here if the polymer fibres have good dispersion properties in aqueous systems, e.g. in the production of wet-laid fleeces. Moreover, it is beneficial for textile applications, if the polymer fibres have good mechanical firmness, for example, to be able to function well in the fibre post-processing, e.g. for stretching on conveyor lines. For textile applications it is also beneficial if the polymer fibres, in particular in the form of fleeces, have a low degree of thermal shrinkage.

For the respective end application or the necessary intermediate treatment steps, e.g. stretching and/or crimping, the polymer fibres usually modified or prepared by application of suitable finish or layers, which are applied on the surface of the finished or to be treated polymer fibres.

Another possibility of chemical modification can be implemented on the polymer base structure itself, for example, by integration of compounds with flame-retardant effect in the polymer main and/or side chain.

Besides this, additives such as antistatic or colour pigments can be introduced to the melted thermoplastic polymer or the polymer fibres during the multi-stage spinning process.

The dispersion behaviour of a polymer fibre is affected, among other, by the nature of the synthetic polymers. In particular, for fibres of thermoplastic polymer, the dispersion properties in aqueous systems is therefore affected by the finish or layers applied on the surface.

Since the recent past, there has been an additional want for fibre systems, which not only meet the aforementioned requirements, besides being manufactured from renewable raw materials, but also require none or only the slightest of adjustments in the subsequent application wherever possible, so that existing processes and machinery can continue to be used.

Therefore, the problem to be solved is providing a polymer fibre of renewable raw materials, which are to have good physical properties so that a good fibre post-processing is possible, for example, in the stretching on conveyor lines, and which additionally are to have a low degree of thermal shrinkage while being biodegradable. It is furthermore beneficial if the polymer fibres of renewable raw materials have good dispersion properties, in particular long-term dispersibility, which will still be available even after a longer period of storage.

The problem just described is solved by the bi-component polymer fibre according to the invention, in which the fibre comprises a component A (core) and a component B (shell), the melting point of the thermoplastic polymer in component A being at least 5° C. higher than the melting point of the thermoplastic polymer in component B and the fibre material comprising component A having a biopolymer A, and the fibre material comprising component B having a biopolymer B.

The bi-component polymer fibre is usually stored as tow after the spinning process and then stretched and postprocessed on a conveyor line by means of a specific process.

The tow can also be directly processed further and depositing the tow in so-called cannisters can be partly or entirely omitted.

The combination of certain biopolymers, i.e. component A (core) and component B (shell) in combination with the specific stretching leads to the bi-component polymer fibre according to the invention, which also has a lower thermal shrinkage.

Polymers

The polymers used according to the invention are thermoplastic polycondensates based on so-called biopolymers.

The “thermoplastic polymers” according to this invention mean a plastic, which can be (thermoplastically) moulded within a certain temperature range, preferably in the range from 25° C. to 350° C. This process is reversible, i.e. it can be repeated optionally many times by cooling and reheating up to the fused state, for as long as no so-called thermal decomposition of the material from overheating occurs. This is where thermoplastic polymers are different from duroplasts and elastomers.

Among the thermoplastic polycondensates based on so-called biopolymers, synthetic biopolymers, especially synthetic biopolymers that are suitable for fusion spinning, are preferable.

The term “synthetic biopolymers” for the present invention refers to a material, which comprises biogenic raw materials (renewable raw materials). This is how they are distinguished from conventional, crude-oil based materials or plastics, e.g. polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC).

The bi-component fibres are manufactured from degradable synthetic biopolymers, where the term biologically degradable is defined, for example, according to ASTM D5338-15 (Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials Under Controlled Composting Conditions, Incorporating Thermophilic Temperatures, ASTM International, West Conshohocken, Pa., 2015, www.astm.org).

Biopolymer A (Core)

The synthetic biopolymer A comprising component A is an aliphatic polyester, in particular, a biopolymer comprising repeat units of lactic acid, hydroxy butyric acid, and/or glycolic acid, preferably lactic acid and/or glycolic acid, in particular lactic acid. Polylactic acids are particularly preferred for this.

Aliphatic polyesters are understood to be such polyesters, which have typically at least about 50 mol-%, in some preferable embodiments at least about 60 mol-% and in more preferable embodiments at least about 70 mol-% aliphatic monomers.

“Polylactic acid” is understood to mean polymers, which comprise lactic acid units. Such polylactic acids are usually created by condensation of lactic acids, but also by the ring-opening polymerisation of lactides under suitable conditions.

According to the invention, especially suitable polylactic acids include poly(glycolide-co-L-lactide), poly(L-lactide), poly(L-lactide-co-c-caprolactone), poly(L-lactide-co-glycolide), poly(L-lactide-co-D,L-lactide), poly(D,L-lactide-co-glycolide), and poly(dioxanone). Such polymers are, for example, available in retail from the company Boehringer Ingelheim Pharma KG (Germany) under the trade names Resomer® GL 903, Resomer® L 206 S, Resomer® L 207 S, Resomer® L 209 S, Resomer® L 210, Resomer® L 210 S, Resomer® LC 703 S, Resomer® LG 824 S, Resomer® LG 855 S, Resomer® LG 857 S, Resomer® LR 704 S, Resomer® LR 706 S, Resomer® LR 708, Resomer® LR 927 S, Resomer® RG 509 S and Resomer® X 206 S.

For the purposes of the present invention, especially beneficial polylactide acids, in particular Poly-D, poly-L or poly-D,L-lactic acids.

The term “polylactic acid” generally refers to homopolymers of lactic acid, such as y (L-lactic acid), poly (D-lactic acid), poly (DL-lactic acid), mixtures thereof, and copolymers containing lactic acid as the predominant component and a small proportion, preferably less than 10 mol %, of a co-polymerisable comonomer.

Other suitable materials for biopolymer A include copolymers or terpolymers based on polylactic acid, polyglycolic acid, polyalkylene carbonates (such as polyethylene carbonate), polyhydroxyalkanoates (PHA), polyhydroxybutyrates (PHB), polyhydroxyvalerates (PHV), and polyhydroxybutyrate-hydroxyvalerate copolymers (PHBV).

In a most preferable embodiment, biopolymer A is exclusively a thermoplastic polymer based on lactic acids.

The polylactide acids used according to the invention have a number average molecular weight (Mn), preferably measured by gel permeation chromatography against narrowly dispersed polystyrene standards or end group iteration, of at least 500 g/mol, preferably min. 1,000 g/mol, most preferably min. 5,000 g/mol, more preferably min.10,000 g/mol, in particular min. 25,000 g/mol. On the other hand, the number average is preferably max. 1,000,000 g/mol, more preferably max. 500,000 g/mol, most preferably max. 100,000 g/mol, in particular max. 50,000 g/mol. A number average of the molecular weight in the range of min 10,000 g/mol up to 500,000 g/mol has also proven to be quite beneficial within the scope of the present invention.

The number average molecular weight (Mw) of preferred lactic-acid polymers, in particular around Poly-D, poly-L or poly-D,L-lactic acids, preferably measured by gel permeation chromatography against narrowly distributed polystyrene standards or end group iteration is preferably within the range between 750 g/mol and 5,000,000 g/mol, more preferably between 5,000 g/mol and 1,000,000 g/mol, most preferably between 10,000 g/mol and 500.000 g/mol, in particular within the range of 30,000 g/mol to 500,000 g/mol, and the polydispersity of these polymers is preferably in the range from 1.5 to 5.

The inherent viscosity of particularly suitable lactic-acid polymers, especially around Poly-D, poly-L or poly-D,L-lactic acids, preferably measured in chloroform at 25° C., 0.1% polymer concentration, is in the range between 0.5 dl/g and 8.0 dl/g, preferably in the range from 0.8 dl/g to 7.0 dl/g, in particular in the range from 1.5 dl/g to 3.2 dl/g.

Within the scope of the present invention, biopolymers, in particular thermoplastic synthetic biopolymers, are moreover extremely beneficial with a glass transition temperature higher than 20° C., preferably higher than 25° C., more preferably higher than 30° C., most preferably 35° C., in particular higher than 40° C. Within the scope of a most preferable embodiment of the present invention, the glass transition temperature of the polymer is in the range between 35° C. and 55° C., in particular in the range between 40° C. and 50° C.

In addition, polymers are particularly suitable, which have a melting temperature higher than 120° C., beneficially at least 130° C., preferably higher than 150° C., and at most 250° C., more preferably at most 210° C., and most preferably in the range between 120° C. and 250° C., in particular in the range from 150° C. to 210° C.

For this, the glass temperature and the melting temperature of the polymer are determined preferably by means of Dynamic Scanning calorimetry (“DSC” for short). Quite particularly, the following procedure has proven beneficial in this context:

Biopolymer B (Shell)

The synthetic biopolymer B comprising the component B is preferably a biopolymer, which has a melting point lower by at least 5° C. than that of the synthetic biopolymer A comprising component A. Preferably, the melting point of biopolymer A is at least by 10° C., more preferably at least 20° C., most preferably at least 30° C., in particular at least 40° C. higher than the melting point of the synthetic biopolymers B.

Biopolymer B is an aliphatic polyester in particular an aliphatic polyester having repeat units, which differ from the repeat units of biopolymer A regarding their chemical structure.

Aliphatic polyesters are understood to be such polyesters, which have typically at least about 50 mol-%, in some preferable embodiments at least about 60 mol-% and in more preferable embodiments at least about 70 mol-% aliphatic monomers.

Biopolymer B commonly has a number average molecular weight (Mn) of at least 10,000 daltons, in particular at least 12,000 daltons, more preferably at least 12,500 daltons and at most up to 120,000 daltons, in particular up to 100,000 daltons, most preferably up to 80,000 daltons.

The number average molecular weight (Mn) is commonly determined by gel permeation chromatography against narrowly distributed polystyrene standards.

Biopolymer B commonly has a mean molecular weight (Mn) of at least 50,000 daltons and at most up to 240,000 daltons, in particular up to 190,000 daltons, most preferably up to 100,000 daltons. The number average molecular weight (Mn) is commonly determined by gel permeation chromatography against narrowly distributed polystyrene standards.

Biopolymer B commonly has a melt flow index of 5 to 200 grams per 10 minutes, in particular 15 to 160 grams per 10 minutes, particular preferred 20 to 120 grams per 10 minutes, measured according to the ASTM test procedure D1238-13 (ASTM D1238-13, Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer, ASTM International, West Conshohocken, Pa., 2013, www.astm.org). The melt flow index is the weight of a polymer (in grams), which can be pressed through an extrusion rheometer opening (0.0825 inch diameter) if it is exposed to a force of 2160 grams in 10 minutes at 190° C.

Biopolymer B preferably has an apparent viscosity of 50 to 215 Pa*s (Pascal seconds), more preferably 70 to 200 Pa*s, measured at a temperature of 160° C. and a shear of 1000s⁻¹ (s=seconds).]

It must be considered here that not only the biopolymers B on the basis of aliphatic polyesters are generally difficult to process with a high apparent viscosity but also that viscosities seemingly too low generally result in astretched fibre, which does not have any tensile strength, and no sufficient binding capacity (thermo-bonding).

Particularly suitable are also biopolymers B, which have a melting temperature higher than 50° C., beneficially at least 100° C., preferably higher than 120° C., and at most 180° C., more preferably at most 160° C., and most preferably in the range between 50° C. and 160° C., in particular in the range from 120° C. to 160° C.

The glass transition temperature of biopolymer B is preferably at least 5° C., more preferably plastic at least 10° C., most preferably at least 15° C. below the glass transition temperature of biopolymer A. The glass transition temperature is measured by means of DSC.

Examples for biopolymers B, which can have a low melting point and a low glass transition temperature, are aliphatic polyesters with repeat units of at least 5 carbon atoms (e.g. polyhydroxyvalerate, polyhydroxybutyrate-hydroxyvalerate copolymer and polycaprolactone) and succinate-based aliphatic polymers (e.g. polybutylene succinate, polybutylene succinate adipate and polyethylene succinate). More specific examples may include polyethylene oxalate, polyethylene malonate, polyethylene succinate, polypropylene oxalate, polypropylene malonate, polypropylene succinate, polybutylene oxalate, polybutylene malonate, polybutylene succinate, and mixtures and copolymers of these compounds. Such aliphatic polyesters are known from the prior art (WO 2007/070064) and are typically synthesised by the condensation polymerisation of a polyol and an aliphatic dicarbon acid or anhydride.

As relates to the present invention, polybutylene succinate and butylene succinate copolymers are particularly preferred.

Especially biopolymers B are suitable for thermo-bonding, which have a high degree of melting and crystallisation enthalpy. Commonly, the biopolymers B are chosen so that they have a crystallinity degree or latent melting heat (Delta Hf) or more than approx. 25 joule per grams (“J/g”), more preferably more than 35 J/g, most preferably more than 50 J/g. The latent melting heat (ΔHf), the latent crystallinity heat (ΔHC) and the crystallinity temperature is measured by means of digital scanning calorimetry (“DSC”) according to ASTM D-3418 (ASTM D3418-15, Standard Test Method for Transition Temperatures and Enthalpies of Fusion and Crystallization of Polymers by Differential Scanning calorimetry, ASTM International, West Conshohocken, Pa., 2015, www.astm.org).

The performance of a specific stretching by means of a parameter set defined according to the invention, besides the biopolymers B, also permits using more affordable variants of the biopolymer B, wherein the bi-component-polymer fibres received this way have a less thermal shrinkage. This way, these specific stretching parameters permit the use of widely available biopolymers B. The specific biopolymer B used in the embodiment according to the present invention has a number average molecular weight (Mn) of at least 10,000 daltons, more preferably of at least 12,000 daltons, most preferably of at least 12,500 daltons and at most up to 30,000 daltons, preferably up to 28,000, more preferably up to 25,000 daltons.

The number average molecular weight (Mn) is commonly determined by gel permeation chromatography against narrowly distributed polystyrene standards.

The specific biopolymer B has a melting temperature higher than 50° C., beneficially at least 100° C., preferably higher than 120° C., and at most 180° C., more preferably at most 160° C., and most preferably in the range between 50° C. and 160° C., in particular in the range from 120° C. to 160° C.

The glass transition temperature of the specific biopolymer B is preferably at least 5° C., more preferably plastic at least 10° C., most preferably at least 15° C. below the glass transition temperature of biopolymer A. The glass transition temperature is measured by means of DSC.

Examples of specific biopolymers B, which can have a low melting point and a low glass transition temperature, are aliphatic polyesters with repeat units of at least 5 carbon atoms (e.g. polyhydroxyvalerate, polyhydroxybutyrate-hydroxyvalerate copolymer and polycaprolactone) and succinate-based aliphatic polymers (e.g. polybutylene succinate, polybutylene succinate adipate and polyethylene succinate). More specific examples may include polyethylene oxalate, polyethylene malonate, polyethylene succinate, polypropylene oxalate, polypropylene malonate, polypropylene succinate, polybutylene oxalate, polybutylene malonate, polybutylene succinate, and mixtures and copolymers of these compounds.

As relates to the present invention, polybutylene succinate and butylene succinate-copolymers as specific biopolymers B are particularly preferable.

Particularly specific biopolymers B are suitable for thermo-bonding, which have a high degree of melting and crystallisation enthalpy. Commonly, the biopolymers B are chosen so that they have a crystallinity degree or latent melting heat (Delta Hf) or more than approx. 25 joule per grams (“J/g”), more preferably more than 35 J/g, most preferably more than 50 J/g. The latent melting heat (ΔHf), the latent crystallinity heat (ΔHC) and the crystallinity temperature is measured by means of digital scanning calorimetry (“DSC”) according to ASTM D-3418 (ASTM D3418-15, Standard Test Method for

Transition Temperatures and Enthalpies of Fusion and Crystallization of Polymers by Differential Scanning calorimetry, ASTM International, West Conshohocken, Pa., 2015, www.astm.org).

The specific biopolymer B has a melting viscosity determined at a temperature of 190° C.

(Göttfert Rheo-Tester 1000) in the range from 250 to 400 Pa*s at 200s⁻¹ (shear) and 125 to 190 Pa*s at 1200s⁻¹ (shear), preferably in the range from 260 to 380 Pa*s at 200s⁻¹ (shear) and 130 to 180 Pa*s at 1200s⁻¹ (shear), more preferably in the range from 275 to 375 Pa*s at 200s⁻¹ (shear) and from 135 to 175 Pa*s at 1200s⁻¹ (shear)

Additives in Polymers A and B

The biopolymers A and B described above contain common additives such as anti-oxidants. It has been proven in this regard that additives of the group of anti-oxidants are unavoidable for the manufacturing and post-processing of the fibres, as the aforementioned biopolymers A and B are sensitive to oxidative decomposition.

Other common additives are pigments, stabilisers, surfactants, waxes, flow promoters, solid solvents, plasticisers and other materials, e.g. nucleating agents, which are added to improve the processability of the thermoplastic composition.

The biopolymers B described above, in particular the specific biopolymers B based on their described properties, can already do with a reduced quantity of additives, especially nucleating agents. Such nucleating agents, which are usually added, simplify the crystallisation during the chilling of the fibres, which simplifies their processing. One type of such a nucleating agent is a multiple carbon acid such as succinic acid, glutaric acid, adipic acid, pimelic acid, morphic acid, azelaic acid, sebacic acid and mixtures of such acids as described in U.S. Pat. No. 6,177,193. The nucleating agents are typically present in biopolymer B in a concentration of less than about 0.5 wt.-% in some embodiments less than about 0.25 wt.-% and in some embodiments less than about 0.1 wt.-%.

At least 90 wt.-% of the bi-component fibres according to the invention comprise the aforementioned aliphatic polyester biopolymers A and B and have typically less than about 10 wt.-%, preferably less than about 8 wt.-%, more preferably less than about 5 wt.-% additives in the biopolymer B forming the shell.

As described above, the biopolymers described above require an addition of anti-oxidant due to their sensitivity to oxidative decomposition, especially of the biopolymer B (shell).

Based on the chosen combination of raw materials and post-processing, the quantity of anti-oxidant can be significantly reduced, i.e. the concentration of the anti-oxidant in the biopolymer B (shell) is between 0.025% and 0.2 wt.-%.

The bi-component fibres according to the invention are combined into tows after spinning and post-processed on a conveyor line using methods known from the prior art, in particular, they are stretched and, if necessary, further crimped or textured. By selection of specific conveyor line parameters in the stretching, particularly the specific biopolymers B that are described above can be used.

Polymer Fibres

The bi-component fibres according to the invention can be provided as finite fibres, e.g. so-called staple fibres or infinite fibres (filament).

For better dispersibility, the fibre is preferably present as a staple fibre. The length of the aforementioned staple fibres is not subject to any fundamental limitation, but it is generally between 2 and 200 mm, preferably 3 to 120 mm, more preferably 4 to 60 mm.

The single yarn count of the bi-component fibres according to the invention, preferably staple fibre, is between 0.5 and 30 dtex, preferably 0.7 to 13 dtex. For some applications, yarn counts between 0.5 and 3 dtex and fibre lengths of <10mm, preferably <8mm, more preferably <6mm, most preferably <5mm are particularly well suited.

The bi-component fibre according to the invention indicates a low hot air thermal shrinkage within the range from 0% to 10%, preferably from >0% to 8%, respectively measured at 110° C.

The combination of certain biopolymers, i.e. of component A (core) and specific biopolymers B as component B (shell) in combination with the specific stretching enables the transmission of the stretching force also to the core material, so that astretching-induced crystallisation is reached. In the bi-component polymer fibres according to the invention, this causes the low thermal shrinkage as described above.

The polymer fibres according to the invention are generally manufactured by common procedures. At first, the polymer is dried, if necessary, and fed into an extruder. Then, the melted material is spun by means of common equipment with corresponding nozzles. The exit speed on the nozzle outlet surface is adjusted to the spinning speed so that a fibre is created with the desired yarn count. Spinning speed is understood to mean the speed at which the rigid filaments are pulled off.

The fibres formed can have round, oval or further suitable cross sections and shapes.

The fibre filaments produced this way are integrated into yarns and these, in turn, are integrated into tows. The tows are initially placed in cannisters for the further processing. The tows intermittently stored in the cannisters are picked up and a large spun fibre tow is created.

Another object of the present invention is the post-treatment of the spun fibre tows, which commonly have 10-600 ktex and are produced by means of the disclosed methods, using conventional conveyor lines with a specific stretching. The feed speed of the spun fibre tow into the stretching or drawframe is preferably 10 to 110 m/min (feed speed). At this point, preparations can still be applied, which promote the stretching but have no negative effects on the following properties.

The stretching can be implemented as a one-step procedure or, optionally, in application of a two-step stretching process (in this regard, for example, see U.S. Pat. No. 3,816,486). Before and during the stretching and in application of conventional methods, one or more finishes can be applied.

The stretching according to the invention takes place at a stretching ratio, especially when using the specific biopolymers B, between 1.2 and 6.0, preferably between 2.0 and 4.0, wherein the temperature during the stretching of the spun tow is between 30° C. and 80° C. The stretching therefore takes place within the range of the glass transition temperature of the spun tow to be stretched. The stretching according to the invention takes place under steam, i.e. in the so-called steam chest, so that the stretching point of the fibre is reached in the steam chest. The steam chest is usually operated at 3 bar pressure.

By stretching under steam in the aforementioned temperature range, the thermal shrinkage of the fibres can be reduced and adjusted in a deliberate and controlled manner.

The preferable conveyor line settings are as follows:

The stretching takes place in a one-step procedure between drawframe S2 and drawframe S1 and in the steam chest, i.e. the stretching point of the fibres is reached in the steam chest. All godets (usually 7) of S1 have a temperature of 30 to 80° C. The entire stretching takes place in the steam chest. The steam chest is preferably operated at 3 bar steam pressure.

All godets (usually 7) of the following drawframe S2 are cold, wherein cold means room temperature (approx. 20 to 35° C.)

This so-called “cold stretching” mode has the effect that the stretching is not fixed at high temperature on S2 under tension. The cold S2 has the benefit that there is no risk that the individual fibres get stuck on the hot godets of S2.

In spite of the “cold stretching,” the fibre is nonetheless insensitive to high temperatures with the tension-free fixation in the oven and can withstand temperatures up to 100° C. without sticking.

The “cold stretching” described above is particularly suitable for polybutylene succinates (FZ71) the melting viscosity of which is determined at a temperature of 190° C. (Göttfert Rheo-Tester 1000) in the range from 250 to 325 Pa*s at 200s⁻¹ (shear) and 125 to 150 Pa*s at 1200s⁻¹ (shear), preferably in the range from 260 to 300 Pa*s at 200s⁻¹ (shear) and 130 to 150 Pa*s at 1200s⁻¹ (shear), more preferably in the range from 270 to 290 Pa*s at 200s⁻¹ (shear) and from 135 to 145 Pa*s at 1200s⁻¹ (shear).

Insofar as the polybutylene succinate (FZ91) has a melting viscosity determined at a temperature of 190° C. (Göttfert Rheo-Tester 1000) in the range from 340 to 400 Pa*s at 200s⁻¹ (shear) and 150 to 190 Pa*s at 1200s⁻¹ (shear), preferably in the range from 350 to 390 Pa*s at 200s⁻¹ (shear) and 160 to 185 Pa*s at 1200s⁻¹ (shear), more preferably in the range from 360 to 385 Pa*s at 200s⁻¹ (shear) and from 165 to 180 Pa*s at 1200s⁻¹ (shear), the drawframe S2 is operated at a temperature within the range between 60° C. and 100° C., i.e. all godets (usually 7) have the aforementioned temperature.

The spun tow preferably has 240 to 360 ktex before the stretching.

Likewise for the crimping/texturing of the stretched fibres, if necessary, conventional methods of mechanical crimping can be applied using generally known crimping machines. A mechanical device for fibre crimping is preferred, which works with the help of steam, e.g. a compression chamber. However, also fibres crimped using other methods can be used, e.g. three-dimensionally crimped fibres. To perform the crimping, the tow is initially brought usually to a temperature in the range from 50° to 100° C., preferably from 70° to 85° C., more preferably to about 78° C., and treated with pressure of the tow infeed rollers between 1.0 and 6.0 bar, more preferably at about 2.0 bar, a pressure in the crimping chamber between 0.5 and 6.0 bar, more preferably between 1.5 and 3.0 bar, with steam between 1.0 and 2.0 kg/min, more preferably 1.5 kg/min.

Insofar as the smooth or, if applicable, crimped fibres are relaxed and/or fixated in the oven or hot air flow, this is also done at temperatures of at most 130° C.

To manufacture staple fibres, the smooth or, if applicable, crimped fibres are taken up followed by cutting and, if applicable, hardening and depositing as flake into pressed rolls. The staple fibres of the present invention are preferably cut on the relaxation of a downstream mechanical cutting unit. To manufacture tow types, cutting can be omitted. These tow types are deposited uncut in the roll and pressed.

Insofar as the fibres according to the invention are presented in a crimped embodiment, the crimping degree is preferably at least 2 crimps (fibre curls) per cm, preferably at least 3 crimps per cm, more preferably between 3 curls per cm and 9.8 curls per cm and most preferably between 3.9 curls per cm and 8.9 curls per cm. For applications to produce textile webs, values between 5 and 5.5 curls per cm are most preferable for the crimping degree. For the production of textile webs by means of wet laying methods, the crimping degree may have to be adjusted in the individual case.

Textile webs can be made from the fibres according to the invention, which are also the object of the invention. Based on the good dispersibility of the fibres according to the invention, such textile webs are made preferably by means of wet laying methods.

The term “textile web” should therefore be understood within the broadest sense in the context of this description. A textile web can be all forms that include the fibres according to the invention and which have been manufactured according to a web-forming technique. Examples of such textile webs are fleeces, in particular wet-laid fleeces, preferably on the basis of staple fibres, which are made by means of thermal bonding.

The fibres according to the invention also have good permanence of dispersibility, i.e. the fibres will continue to have very good dispersion quality even after longer periods of storage, e.g. several weeks or months, in the form of rolls or comparable forms.

Moreover, the fibres according to the invention have good long-term dispersion qualities, i.e. if the fibres are dispersed in liquid media, e.g. in water, the fibres stay dispersed for longer and begin to settle only after a longer period of time.

Test methods:

Unless already indicated in the foregoing description, the following measuring or test methods are used:

Yarn count:

The yarn count was determined according to DIN EN ISO 1973.

Dispersibility:

For the assessment of the dispersibility, the following test method was developed and applied according to the invention:

The fibres according to the invention are cut to a length of 2 to 12 mm. The cut fibres are placed at room temperature (25° C.) into a glass vessel (dimensions: 150 mm length, 200 mm width, 200 mm height), which is filled with DI water (DI=deionised). The quantity of fibres is 0.25g per lite DI water. For better assessment, usually 1 g fibres and 4 litres of DI water are used.

Then, the fibre/DI water mixture is stirred using a normal laboratory magnetic mixer (e.g. IKAMAG RCT) and a [sic magnetic fish] (80mm) for at least three minutes (rotation speed around 750-1500 rpm), after which the mixer is switched off. It is then determined if all fibres have dispersed.

This dispersion behaviour of the fibres is now evaluated as follows:

not dispersed (−)

partly dispersed (∘)

fully dispersed (+)

The evaluation above is made based on defined intervals of time.

Biologically Degradable

The determination is made according to ASTM D5338-15 (Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials Under Controlled Composting Conditions, Incorporating Thermophilic Temperatures, ASTM International, West Conshohocken, Pa., 2015, www.astm.org).

Number Average Molecular Weight (Mn)

Determination by means of gel permeation chromatography against narrowly distributed polystyrene standards of by end group titration.

Weight Average of Molecular Weight (Mw)

Determination by means of gel permeation chromatography against narrowly distributed polystyrene standards of by end group titration.

Inherent Viscosity

Determination measured in chloroform at 25° C., 0.1% polymer concentration via GPC.

Glass Transition Temperature and Melting Temperature

Determination by means of Dynamic Differential Scanning calorimetry (“DSC” for short) according to the following procedure:

Performance of the DSC measurement under nitrogen, calibration against indium.

Nitrogen flow is at 50 ml/min; initial weight of fibres in the range of 2 to 3 mg.

Temperature range between −50° C. to 210° C. @ 10 K/min, then isotherm for 5 min and finally again up to −50° C. @ 10 K/min

The final temperature is generally always about 50° C. above the highest expected melting point.

The DSC measurement is performed by means of a TA/Waters Modell Q100.

Melting Viscosity

The melting viscosity is determined by means of a Göttfert Rheo Tester 1000 at a temperature of 190° C., at 200s⁻¹ (shear) and 1200s⁻¹ (shear).

Apparent Viscosity

The determination is made as explained in WO 200//070064.

Melt Flow Index

The determination is made according to the ASTM test method D1238-13 (ASTM D1238-13, Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer, ASTM International, West Conshohocken, Pa., 2013, www.astm.org). The melt flow index is the weight of a polymer (in grams), which can be pressed through an extrusion rheometer opening (0.0825-inchdiameter) if it is exposed to a force of 2160 grams in 10 minutes at 190° C.

Latent Melting Heat

The latent melting heat (ΔHf), the latent crystallinity heat (ΔHC) and the crystallinity temperature is measured by means of digital scanning calorimetry (“DSC”) according to ASTM D-3418 (ASTM D3418-15, Standard Test Method for Transition Temperatures and Enthalpies of Fusion and Crystallization of Polymers by Differential Scanning calorimetry, ASTM International, West Conshohocken, Pa., 2015, www.astm.org).

Thermal Shrinkage

From the tow sample, 12 fibres (measuring samples) are extracted. By means of tweezers, they are clamped on one end into a multi-clamp and a decrimping weight is fastened on the other end. The measurement is taken from a bi-component fibre of the type PLA/PBS (core/shell) with a yarn count of 2.2 dtex and the decrimping weight is 190 mg.

The multi-clamp loaded with the measuring samples is fastened with stand so that the measuring samples hang freely under prestressing force in the stand. The chosen starting length (normally 150 mm) is marked there on each fibre. This is done by means of marking lines on the stand and marking points that are put on the samples. After the marking, the loaded multi-clamp is taken down and placed onto a velvet sheet. The decrimping weights are taken off there and the free fibre ends are clamped into a second multi-clamp. The measuring samples that are clamped between two multi-clamps are hooked into a wire rack free from tension. This wire rack is inserted centred into the pre-heated shrink oven heated to the correct treatment temperature (regular temperatures are 200° C., 110° C., 80° C.). After a treatment time of 5 minutes, the wire rack is taken out of the oven. After the two multi-clamps have cooled down, they are taken out with the measuring samples and placed onto the velvet sheet. After an acclimatisation time of 30 minutes, the back measurement can be taken. For this, the measuring samples are loaded with the decrimping weights again and hooked into the stand. The adjustable marking line of the stand is positioned for the back measurement so that the upper edge of each marking point can be covered by the marking line. Now, the length between the markings on the counter of the stand is read for each fibre separately precise to 1/10 mm.

$\mathrm{Calculation}\mathrm{of}\mathrm{the}\mathrm{length}\mathrm{change}:\mathrm{Change}\mathrm{in}\mathrm{length}\left[\%\right]=\frac{\mathrm{Initial}\mathrm{length}\left[\mathrm{mm}\right]-\mathrm{measured}\mathrm{length}\left[\mathrm{mm}\right]}{\mathrm{Initial}\mathrm{length}\left[\mathrm{mm}\right]}\times 100\%$

It counts the average value of all 12 measuring samples.

The invention is explained by the following example without limiting its scope to this.

EXAMPLE

The raw materials PLA 6202D of NatureWorks and BioPBS Fz71PM were spun into a corresponding fibre by means of bicomponent spinning technology. The PLA concentration as core material was 70 wt.-%, the shell percentage was 30 wt.-%. The set transport of overall 331 g/min with a nozzle with 827 holes and a haul-off speed of 1000 m/min resulted in a spun yarn count of 4.0 dtex. In addition, an antioxidant with 0.05% active substance concentration was added to the PBS to reach a corresponding good spinning behaviour at the spinning temperature of 240° C. As usual, finish was applied on the spinning material to permit further processing.

Then, the spun product was processed at an unstretched tow length of approx. 42 ktex on a conventional staple fibre line.

Stretched in steam medium of 2.2 dtex and fixated at 90° C. in the circulating air oven, the following textile technology key values of the crimped variant resulted for the further processing in the airlay procedure:

Linear density: 2.3 dtex

Hardness: 28 cN/tec

Stretching: 41%

Shrinkage (110° C.): 1.5%

Crimping: 5 Bg/cm

BioPBS Fz71PM is a polybutylene succinate with a melting viscosity of (190° C.) 279 Pa*s at 200s⁻¹ (shear) and 139 Pa*s at 1200s⁻¹ (shear).

PLA 6202D is a polylactide acid with a relative density of 1.24 g/cm³ (according to ASTM D792) and a melt flow index (g/10min@210° C.) in the range of 15-30. The glass transition temperature is 55-60° C. (according to ASTM D3417) and the crystalline melt temperature is 160-170° C. (according to ASTM D3418).

Claims

1. Bi-component polymer fibre, wherein the fibre comprises a component A (core) and a component B (shell) and

(i) the melting point of the thermoplastic polymer in component A is higher by at least 5° C. than the melting point of the thermoplastic polymer in component B; and

(ii) the fibre material comprising component A comprises a biopolymer A and the fibre material comprising component B comprises a biopolymer B;

(iii) the biopolymer A is an aliphatic polyester, preferably a biopolymer comprising repeat units of the lactic acid and biopolymer B is an alipathic polyester, wherein the biopolymer B and the biopolymer A differ regarding their chemical structure;

characterised in that the bi-component polymer fibres have a hot-air thermal shrink rate in the range from 0% to 10% measured at 110° C.

2. Polymer fibres according to claim 1, characterised in that the biopolymer A and biopolymer B are respectively biologically degradable, synthetic biopolymers according to ASTM D5338-15.

3. Polymer fibres according to claim 1 or claim 2, characterised in that the biopolymer A comprises repeat units of the lactic acid, of the hydroxy butyric acid and/or of the glycol acid, preferably of the lactic acid and/or glycol acid, in particular of the lactic acid.

4. Polymer fibre according to claim 1, 2 or 3, characterised in that the biopolymer A is a polylactide acid with number average of molecular weight (Mn) of min. 500 g/mol, preferably min. 1,000 g/mol, more preferably min. 5,000 g/mol, most preferably min. 10,000 g/mol, in particular min. 25,000 g/mol.

5. Polymer fibres according to one or more of the claims 1 to 4, characterised in that the biopolymer A is a polylactide acid with number average of molecular weight (Mn) of max. 1,000,000 g/mol, preferably max. 500,000 g/mol, in particular max. 100,000 g/mol.

6. Polymer fibres according to claim 1, 2 or 3, characterised in that the biopolymer A is a polylactide acid with numerical mean of molecular weight (Mw) in the range from 750 g/mol to 5,000,000 g/mol, preferably in the range from 5,000 g/mol to 1,000,000 g/mol, more preferably in the range from 10,000 g/mol to 500,000 g/mol, most preferably in the range from 30,000 g/mol to 500,000 g/mol, with the polydispersity of these polymers being in the range between 1.5 and 5.

7. Polymer fibres according to one or more of the claims 1 to 6, characterised in that the biopolymer A is a polylactide acid with an inherent viscosity, measured in chloroform at 25° C., of 0.1% polymer concentration in the range from 0.5 dl/g and

8. 0 dl/g, preferably in the range from 0.8 dl/g and 7.0 dl/g, more preferably in the range from 1.5 dl/g and 3.2 dl/g.

8. Polymer fibres according to one or more of the claims 1 to 7, characterised in that the biopolymer A gas a glass transition temperature higher than 20° C., preferably higher than 25° C., in particular higher than 30° C., more preferably higher than 35° C., in particular higher than 40° C.

9. Polymer fibres according to one or more of the claims 1 to 8, characterised in that the biopolymer B has a number average molecular weight (Mn) of at least 10,000 daltons, in particular at least 12,000 daltons, more preferably at least 12,500 daltons and at most up to 120,000 daltons, in particular up to 100,000 daltons, most preferably up to 80,000 daltons.

10. Polymer fibres according to one or more of the claims 1 to 8, characterised in that the biopolymer B has a mean molecular weight (Mn) of at least 50,000 daltons and at most up to 240,000 daltons, in particular up to 190,000 daltons, most preferably up to 100,000 daltons.

11. Polymer fibres according to one or more of the claims 1 to 10, characterised in that the biopolymer B has a melt flow index of 5 to 200 grams per 10 minutes, in particular 15 to 160 grams per 10 minutes, more preferably 20 to 120 grams per 10 minutes, measured according to the ASTM test method D1238-13.

12. Polymer fibres according to one or more of the claims 1 to 11, characterised in that the biopolymer B has a glass transition temperature of at least 5° C., more preferably at least 10° C., most preferably at least 15° C. below the glass transition temperature of the biopolymer A.

13. Polymer fibres according to one or more of the claims 1 to 12, characterised in that the biopolymer B is an aliphatic polyester, with repeat units of at least 5 carbon atoms, preferred biopolymers B are polyhydroxyvalerate, polyhydroxybutyrate-hydroxyvalerate copolymer and polycaprolactone and succinate-based aliphatic polymers, in particular polybutylene succinate, polybutylene succinate adipate and polyethylene succinate, as well as polyethylene oxalate, polyethylene malonate, polyethylene succinate, polypropylene oxalate, polypropylene malonate, polypropylene succinate, polybutylene oxalate, polybutylene malonate, polybutylene succinate and mixtures of the same and co-polymers of these compounds.

14. Polymer fibres according to claim 13, characterised in that the biopolymer B is a polybutylene succinate and/or a polybutylene succinate co-polymer.

15. Polymer fibres according to one or more of claims 1 to 14, characterised in that they are stretched after spinning in the form of a tow, the temperature during the stretching of the tow is between 30° C. and 80° C., and therefore above the glass transformation temperature of the biopolymers A and B, and the stretching takes place in exposure to steam with the stretching rate preferably being between 1.2 and 6.0.

16. Polymer fibres according to claim 15 characterised in that the spun tow has a yarn count of 240 to 360 ktex before stretching.

17. Polymer fibres according to claim 15 of 16, characterised in that the biopolymer B has a number average molecular weight (Mn) of at least 10,000 daltons, in particular at least 12,000 daltons, more preferably at least 12,500 daltons and at most up to 30,000 daltons, in particular up to 28,000 daltons, most preferably up to 25,000 daltons.

18. Polymer fibres according to claim 17, characterised in that biopolymer B has a melting viscosity determined at a temperature of 190° C. in the range from 250 to 400 Pa*s at 200s−1 (shear) and 125 to 190 Pa*s at 1200s−1 (shear), preferably in the range from 260 to 380 Pa*s at 200s−1 (shear) and 130 to 180 Pa*s at 1200s−1 (shear), more preferably in the range from 275 to 375 Pa*s at 200s−1 (shear) and from 135 to 175 Pa*s at 1200s−1 (shear).

19. Textile web in particular received from a wet-laid procedure, comprising polymer fibres as defined by claims 1 to 18.

20. Use of the polymer fibres as defined by claims 1 to 18 for the production of aqueous suspensions.