Method for selectively dissolving polyurethane from a textile

Abstract

The invention relates to a method for selectively dissolving polyurethane from a textile. The method comprises the steps of - providing a textile comprising polyurethane and / or polyurethane-based fibers and / or comprising a polyurethane and / or a polyurethane-based coating; - contacting the textile with a solvent to dissolve the polyurethane fibers and / or polyurethane- based fibers and / or to dissolve the polyurethane coating and / or the polyurethane-based coating thereby forming a solution, the solvent comprising a urea-based compound and / or a thiourea-based compound. Furthermore, the invention relates to a solvent mixture suitable for selectively dissolving polyurethane from a textile comprising polyurethane and / or polyurethane-based fibers or from a textile comprising a polyurethane and / or a polyurethane-based coating.

Description

Method for selectively dissolving polyurethane from a textileField of the invention

[0001] The present invention relates to a method for selectively dissolving polyurethane from a textile, in particular from a textile comprising polyurethane or polyurethane-based fibers. The invention further relates to a solvent mixture suitable for selectively dissolving polyurethane from a textile, in particular suitable for selectively dissolving polyurethane or polyurethane-based fibers from a textile.Background art

[0002] Polyurethane (PU) is a highly versatile material with numerous applications. PU is widely used in textile applications due to its unique combination of flexibility, durability, elasticity and resistance to abrasion and solvents. In particular, PU is used in fabrics to add stretch properties or to create waterproof layers.

[0003] Elastane, also known as Spandex or Lycra, is a polyurethane-based elastomeric fiber, commonly used in garments that require elasticity, such as underwear, leggings, sportswear, cycling apparel, tights and socks. Elastane is composed of block co-polymers consisting of strong, rigid polymer segments alternated with weaker flexible segments. Elastane is often blended with other fibers such as polyethylene terephthalate (PET), polyamide (PA) and cotton. The elastane content of these blends is typically between 5 and 15 wt% but can be higher, for example 49 wt%. Some typical elastane containing blends are polyamide / elastane : 88 / 12 (panties); PET / elastane : 84 / 15 (sport shirts) and polyamide / elastane : 51 / 49 (swimsuits).

[0004] While the incorporation of elastane significantly expands the applications of textiles, it poses challenges for textile recycling as the presence of elastane hinders the recyclability of primary components in blends. Additionally, elastane can cause clumping, clogs and soiling in the machinery during (re)processing. Removing elastane from textiles such as yarns or fabrics enables the production of cleaner, higher quality recycled materials, facilitating the recycling of fibers. Efficient removal of elastane is therefore essential to improve the recyclability of textiles, thereby promoting a more sustainable, circular textile industry.

[0005] Various strategies have been explored to remove elastane from textiles, including thermal degradation, depolymerization and solvent-based techniques.

[0006] At thermal degradation process is described in WO2013032408. According to this process elastane fibers are removed by controlled thermal degradation in either an argon or air atmosphere, followed by washing with a polar solvent such as ethanol.

[0007] W02020 / 0130825 describes a method for the removal of polyurethane fibers from a yarn or fabric comprising polyurethane fibers and cellulose-based fibers by depolymerization (aminolysis). According to this method, the fabric or yarn is subjected to a mixture of a strong dipolarsolvent such as dimethyl formamide (DMF) and dimethyl acetamide (DMAc), an amine and / or a glycol.

[0008] These two techniques indeed promote the removal of elastane through degradation of the material along with the formation of unwanted, toxic by-products. Furthermore, the risk of degradation of the textile material using these techniques is high.

[0009] Known solvent-based techniques for selectively dissolving polyurethane such as elastane from a textile typically use strong polar solvents such as dimethylacetamide (DMAc) or dimethylformamide (DMF). Despite their effectiveness, these solvents have drawbacks, including environmental and health concerns, the large volumes required and the high operation costs.

[0010] WO2024 / 068912 describes a method for selectively dissolving polyurethane from a textile by immersing the textile in a solvent mixture comprising dimethyl sulfoxide (DMSO) as a first solvent and at least one other solvent selected from the group of tetra hydrofuran (THF), 2- methyltetrahydrofuran (2-MeTHF), cyclopentyl methyl ether (CPME) and cycohexanone. These solvents offer a less toxic alternative to DMP and DMAc. However, due to the relatively low solubility of the polymer, such methods require substantial solvent quantities.

[0011] US2024 / 0092991 describes methods for removing elastane from elastane blends using cyclohexanone or ethyl lactate. Also these methods require substantial solvent quantities.Summary of the invention

[0012] It is an object of the present invention to provide a method for selectively dissolving polyurethane from a textile, for example from a textile comprising polyurethane fibers or polyurethane-based fibers.

[0013] It is another object of the present invention to provide a method for selectively dissolving elastane from a textile.

[0014] It is another object of the present invention to provide a method for selectively dissolving polyurethane from a textile comprising polyurethane fibers or polyurethane-based fibers and at least one other type of fibers.

[0015] It is another object of the present invention to provide a method for selectively dissolving polyurethane from a textile creating minimal impact on the textile materials other than polyurethane thus enabling high-value recycling of the textile materials. In particular it is an object to selectively dissolve elastane from a textile without causing dissolution and / or degradation of the other fibers present in the textile.

[0016] It is another object of the present invention to provide a solvent for the selective dissolution of polyurethane from a textile having a high solubility capacity, in particular a solubility capacity of at least 10 mg polyurethane per gram solvent (>1 wt%), at least 20 mg polyurethane per gram solvent (>2 wt%), at least 30 mg polyurethane per gram solvent (>3 wt%), at least 40 mgpolyurethane per gram solvent (>4 wt%), at least 50 mg polyurethane per gram solvent (>5 wt%) or a higher solubility capacity.

[0017] It is another object of the present invention to provide a method for selectively dissolving polyurethane from a textile using a high elastane:solvent weight ratio, i.e. a method allowing to dissolve a high amount of elastane for a limited amount of solvent.

[0018] It is another further object of the present invention to provide a method for selectively dissolving polyurethane from a textile using a limited amount of solvents.

[0019] It is a further object of the present invention to provide a method for selectively dissolving polyurethane from a textile at room temperature.

[0020] It is still a further object of the present invention to provide a method for selectively dissolving polyurethane from a textile using a solvent further comprising surfactants, in particular nonionic surfactants, allowing to reduce the consumption of solvents.

[0021] It is a further object of the present to provide a solvent mixture suitable for selectively dissolving polyurethane from a textile, in particular suitable for selectively dissolving polyurethane or polyurethane-based fibers or a polyurethane coating or polyurethane-based coating from a textile.

[0022] According to a first aspect of the invention a method for selectively dissolving polyurethane from a textile is provided. The method comprises the steps of providing a textile comprising polyurethane fibers and / or polyurethane-based fibers and / or comprising a polyurethane coating and / or a polyurethane-based coating; contacting the textile with a solvent to dissolve the polyurethane fibers or polyurethane-based fibers and / or the polyurethane coating or the polyurethane-based coating thereby forming a solution, the solvent comprising a urea-based compound and / or a thiourea-based compound.

[0023] The method according to the present invention may further comprise the step of removing the remaining textile from the solution while polyurethane remains dissolved in the solution.

[0024] Furthermore, the method according to the present invention may comprise the step of recovering polyurethane from the solution.

[0025] Preferred textiles comprise a content of polyurethane or polyurethane-based material ranging between 5 and 20 wt%, for example between 5 and 15 wt%, although higher contents such as 25 wt%, 30 wt%, 40 wt% or 50 wt% are also possible, The polyurethane or polyurethane-base coating may comprise polyurethane fibers and / or polyurethane based fibers or a polyurethane coating and / or a polyurethane based coating.

[0026] For the purpose of this invention, a textile is defined as a flexible material comprising fibers, either natural fibers, man-made fibers or combinations thereof. Textiles include fibers, yarns, filaments, threads, fabrics and end-products comprising a fabric. Textiles include consumer textilesfor domestic purposes as well as technical textiles. Examples of consumer textiles comprise apparel textiles (for example T-shirts, sweaters, trousers, underwear, socks), home textiles (for examples bed linens, towels, curtains, upholstery fabrics). Examples of technical textiles comprise geotextiles, industrial textiles and medical textiles.

[0027] For the purpose of the present invention a fiber is defined as the basis entity, either natural or manufactured, that can be used to produce various types of textiles or fabrics. Fibers can be twisted or spun into yarn.

[0028] A yarn is defined as a thin, long strand of fibers for example formed by spinning and suitable to make a fabric.

[0029] A fabric is meant to mean any material made by weaving, knitting, crocheting, knotting, felting, braiding, or bonding fibers or yarns.

[0030] An end-product of a textile is defined as a (final) manufactured item formed by processing one or more fabrics through techniques such as cutting, shaping, stitching, sewing, bonding, adhering, printing, dyeing, laminating, coating or otherwise finishing.

[0031] Textiles used in the method according to the present invention comprise polyurethane fibers and / or polyurethane-based fibers and / or comprise a polyurethane coating and / or a polyurethane based coating. Preferred textiles used in the method according to the present invention comprise polyurethane fibers and / or polyurethane-based fibers.

[0032] Polyurethane is defined as a polymer composed of organic units joined by carbamate (urethane) links. Polyurethane polymers are traditionally and most commonly formed by reacting a polyisocyanate (for example diisocyanate) with a polyol (for example diol).

[0033] A polyurethane-based material is defined as any material primarily composed of polyurethane or containing polyurethane as a key component within a composite or blend.

[0034] The method according to the present invention is suitable for textiles comprising polyurethane fibers or polyurethane based fibers. Such method comprises the steps of providing a textile comprising polyurethane fibers and / or polyurethane-based fibers, contacting the textile with a solvent to dissolve the polyurethane fibers and / or the polyurethane-based fibers thereby forming a solution, the solvent comprising a urea-based and / or a thiourea-based compound.

[0035] . Preferably, textiles comprise polyurethane and / or polyurethane-based fibers and at least one other type of fibers. Such other type of fibers may comprise natural fibers such as cotton, wool,linen or may comprise man-made fibers such as polyester, polyamide (nylon), acrylic, polypropylene, polyethylene terephthalate (PET), viscose, lyocell or aramid fibers.

[0036] A preferred polyurethane-based fiber comprises elastane. Elastane, also known as Spandex or Lycra, is a synthetic fiber comprising segmented polyurethane. Elastane is a polyurethane elastomeric fiber comprising block copolymers of rigid and flexible polymer segments. The synthesis of elastane typically consists of an initial step of reacting a macroglycol with a diisocyanate monomer to give a prepolymer. Then the formed prepolymer is further reacted with an equal amount of diamine.

[0037] Preferred textiles comprising elastane further comprise PET, polyamide, cotton or combinations thereof. The elastane content typically ranges between 5 and 20 wt%, for example between 5 and 15 wt%, although higher elastane contents such as content of 25 wt%, a content of 30 wt%, a content of 40 wt% and contents up to 50 wt% are also possible.

[0038] The method according to the present invention is also suitable for textiles comprising a polyurethane coating or a polyurethane-based coating. Such method comprises the steps of providing a textile comprising a polyurethane coating or a polyurethane-based coating, contacting the textile with a solvent to dissolve the polyurethane coating or the polyurethane- based coating thereby forming a solution, the solvent comprising a urea-based and / or a thiourea-based compound.

[0039] The polyurethane or polyurethane-based coating is for example applied on fibers, yarns and / or on a fabric.

[0040] Preferred examples of textiles comprising a polyurethane or polyurethane-based coating comprise textiles comprising fibers or yarns provided with a polyurethane or polyurethane-based coating, for example a fabric comprising fibers or yarns provided with a polyurethane or polyurethane-based coating. Preferred fibers or yarns coated with a polyurethane or polyurethane- based coating comprise polyester, polyamide (nylon), acrylic, polypropylene, polyethylene terephthalate (PET), viscose, lyocell or aramid fibers.

[0041] The content of the polyurethane and / or polyurethane-based coating ranges preferably between 5 and 20 wt%, for example between 5 and 15 wt%, although higher contents of poyluretane and / or polyurethane-based coating such as content of 25 wt%, a content of 30 wt%, a content of 40 wt% and contents up to 50 wt% are also possible.

[0042] It is clear that the method according to the present invention is also suitable for textiles comprising a combination of polyurethane fibers or polyurethane-based fibers and a polyurethane coating or a polyurethane-based coating. Such method comprises the steps of providing a textile comprising polyurethane fibers and / or polyurethane-based fibers and a polyurethane coating and / or a polyurethane-based coating,contacting the textile with a solvent to dissolve the polyurethane fibers or the polyurethane- based fibers and the polyurethane coating or the polyurethane-based coating thereby forming a solution, the solvent comprising a urea-based compound and / or a thiourea-based compound.

[0043] The solvent used in the method according to the present invention comprises a urea-based compound, a thiourea-based compound or a combination of a urea-based compound and a thiourea-based compound. The solvent may comprise one compound or a mixture comprising multiple compounds. For the purpose of this invention the terms solvent and solvent mixture can be used interchangeably. It is clear that the solvent may comprise additional compounds known in the art.

[0044] A urea-based compound is defined as a compound having a urea functional group, i.e. a functional group comprising a carbonyl group (-C(=O)-) bonded to two nitrogen atoms. A urea- based compound thus comprises a functional group of the type -NH-C(=O)-NH-), -N-C(=O)-N- or -N-C(=O)-NH-.

[0045] It is clear that a urea-based compound includes urea, also called carbamide. Urea is a compound having two amino groups (-NH2) joined by a carbonyl functional group (-C(=O)-) having the chemical formula CO(NH2)2.

[0046] Urea-based compounds may further comprise substituents as for example one or more (linear) alkyl substituents or one or more cycloalkyl substituents. Alkyl substituents preferably comprise C1 - C15 alkyls, either substituted or non-substituted. More preferably, alkyl substituents comprise C5 - C15 alkyls, either substituted or non-substituted. Cycloalkyl substituents preferably comprise C5 - C8 cycloalkyls or C5-C8 aromatic groups, either substituted or non- substituted. Examples of cycloalkyls substituents comprise cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl. Examples of aromatic groups comprise phenyl or xylene.

[0047] Particular examples of urea-based compounds comprise dimethyl urea (DMU), trimethyl urea, tetramethyl urea (TMU), tetraethyl urea, N-cyclohexylurea, (2-methylcyclohexyl)urea and 1- cyclohexyl-3-(4-methylcyclohexyl)urea.

[0048] Other urea-based compounds comprise cyclic urea-based compounds. Cyclic urea-based compounds are compounds in which the urea functional group (-NH-C(=O)-NH-), -N-C(=O)-N- or - N-C(=O)-NH-) is incorporated into a ring structure. These rings typically consist of carbon atoms, nitrogen atoms and optionally one or more oxygen atoms. The carbonyl group (C=O) is part of the ring. Examples of cyclic urea-based compounds comprise propylene urea such as N,N- dimethylpropylene urea (DMPU) or tetramethylpropylene urea (TMPU) and imidazolidinones such as dimethyl imidazolidinone (1 ,3-dimethyl-2-imidazolidinone).

[0049] Tetramethylurea is a particularly preferred urea-based compound because of its superior solubility capacity promoting faster solubility of polyurethane, for example of 4 wt% at room temperature.

[0050] Dimethyl urea is another preferred urea-based compound. Although this compound has its maximum solubility capacity at the melting point of the compound, the compound has the advantage to be cheap, to be widely available and to be reported as non-toxic.

[0051] A thiourea-based compound is defined as a compound having a thiourea functional group, i.e. a functional group comprising a -C(=S)- group bonded to two nitrogen atoms. A thiourea-based compound thus comprises a functional group of the type -NH-C(=S)-NH-), -N-C(=S)-N- or -N-C(=S)-NH-.

[0052] It is clear that a thiourea-based compound includes thiourea. Thiourea is a compound having two amino groups (-NH2) joined by a (-C(=S)-) group having the chemical formula SC(NH2)2.

[0053] Thiourea-based compounds may further comprise substituents as for example one or more alkyl substituents or one or more cycloalkyl substituents. Alkyl substituents preferably comprise C1- C15 alkyls, either substituted or non-substituted. More preferably, alkyl substituents comprise C5- C15 alkyls, either substituted or non-substituted. Cycloalkyl substituents preferably comprise C5- C8 cycloalkyls or C5-C8 aromatic groups, either substituted or non- substituted. Examples of cycloalkyls substituents comprise cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl. Examples of aromatic groups comprise phenyl or xylene.

[0054] Other thiourea-based compounds comprise cyclic thiourea-based compounds. Cyclic thiourea-based compounds are compounds in which the thiourea functional group (-NH-C(=S)-NH-), -N-C(=S)-N- or -N-C(=S)-NH-) is incorporated into a ring structure. These rings typically consist of carbon atoms, nitrogen atoms and optionally one or more oxygen atoms. The -(C=S)- group is part of the ring.

[0055] For an efficient dissolving process, it is of importance that the textile is in mutual contact with the solvent. Therefore, in the method according to the present invention, the textile is contacted with the solvent to form a mixture. The mixture comprises the dissolved polyurethane and the solvent. While the contacting proceeds, the at least partially dissolved polyurethane will be present in the mixture. Possibly, other compounds such as ink, additives, glue and / or other components present in or on the textile material will be present in the mixture as well.

[0056] The contacting step may be carried out e.g. by immersing the textile in the solvent. For example, the textile may be introduced in a container and the solvent may be added, or the textile may be introduced in a container wherein the solvent was previously introduced.

[0057] The concentration of the textile in the solvent is for example 1 wt%, 2 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 30 wt% or 50 wt%.

[0058] The textile and the solvent are preferably contacted at a temperature ranging between 20 °C and 150 °C. Good results are obtained when working at room temperature. In some methods the selective dissolution is improved when working at higher temperatures, for example at 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, 100 °C, 120 °C or 150 °C. It is clear that the temperature is limited by the boiling point of the solvent. Furthermore, the temperature is preferably kept below 100 °C, i.e. between 20 °C and 100 °C, in order to minimize the energy consumption and to avoid unwanted dissolution of the remaining textile, for example unwanted dissolution of target fibers to be recycled.

[0059] In particular embodiments of the present invention, the method further comprises mechanically agitating the mixture while the plastic material is contacted with the solvent. By such mechanically agitation the efficiency of the dissolution process may increase and / or the contact time needed may decrease considerably. In certain embodiments, the mechanical agitation such as the stirring, is continued as long as the textile is contacted with the solvent. Mechanical agitation can be applied by any method known in the art. For example, the mixture may be stirred (e.g. magnetic stirring, stirring in a continuous stirred tank reactor (CSTR) using a rotating agitator), mixed, or (high-intensity) sonication may be applied. In particular embodiments, the textile is contacted with the solvent under stirring, preferably the textile is contacted with the solvent under stirring at 300 rpm or more, more preferably at 500 rpm or more.

[0060] As noted above, temperature, mechanical agitation of the mixture, volume ratio of the solvent, etc. may influence the efficiency of the process and as such determine the contact time needed to achieve dissolution.

[0061] Dissolution may also be faster and more efficient by using smaller sizes of textile due to higher diffusion rates. Therefore, in certain embodiments, the method may comprise an additional step of reducing the size of the textile before the contacting step. Too small sizes on the other hand may become unpractical. In particular embodiments, the textile may be reduced in size to obtain plastic material having a sieve diameter between 0.01 cm and 20.00 cm, for example between 0.01 cm and 10.00 cm, between 0.10 cm and 10.0 cm or between 0.10 cm and 4.00 cm, preferably between 0.50 cm and 4.00 cm. The term ‘sieve diameter’ refers to the size of a sieve opening (the width of a square aperture) through which a particle will pass. Techniques for reducing the size of a textile are well-known to the skilled person and may include, for example, cutting, shredding, milling and / or grinding.

[0062] The textile may also or further be subjected to one or more other pre-treatment steps before the contacting step. Such pretreatment step may comprise the washing of the textile, for examplewith a water-based medium to remove impurities like organic matter, possibly followed by a drying step.

[0063] For the method according to the present invention, the solubility capacity of the solvent is typically higher than 10 mg per g solvent, higher than 15 mg per g solvent, higher than 20 mg per g solvent, higher than 25 mg per g solvent, higher than 30 mg per g solvent, higher than 40 mg per g solvent or higher than 50 m per g solvent. The solubility capacity of a solvent generally refers to the maximum amount of a substance (solute) that can dissolve in a given quantity of the solvent at specific temperature and pressure. The solubility capacity is thus a measure of how much solute the solvent can hold in solution before the solute starts precipitating out or no longer dissolves, reaching saturation.

[0064] The solubility capacity reached with the method according to the present invention is an important advantage over methods known in the art. The method described in WO2024068912 reaches for example a solubility capacity of maximum 15 mg per g solvent, the methods described in US2024 / 0092991 reach a solubility capacity of maximum 0.8 mg per g solvent.

[0065] In preferred embodiments of the present invention, the solvent further comprises one or more surfactants. This surfactant preferably comprises a non-ionic surfactant. Non-ionic surfactants have covalently bonded oxygen-containing hydrophilic groups, which are bonded to hydrophobic structures. The oxygen-containing group comprises for example an alcohol, phenol, ether, ester or amide. Preferred examples comprise a compound having and ethoxylated alcohol unit. The hydrophobic structures comprise for example a carbon chain having 4 to 15 carbon atoms.

[0066] Examples of non-ionic surfactants comprise C4-C15 alcohol ethoxylates.

[0067] Particular examples of non-ionic surfactants comprise Tergitol 15-S-5, Triton X-100, diethylene glycol monobutyl ether (DGMBE) and ethylene glycol monobutyl ether (EGMBE).

[0068] The surfactant is preferably present in the solvent mixture in a concentration ranging between 0 and 50 vol%, for example in a concentration of 5 vol%, 10 vol%, 20 vol%, 30 vol% or 40 vol%. More preferably, the surfactant is present in the solvent mixture in a concentration ranging between 20 and 50 vol%, for example between 25 and 50 vol% or between 30 and 50 vol%.

[0069] By adding one or more surfactants to the solvent the solubility capacity of the solvent is increased. In particular examples, the solubility capacity of the solvent is typically higher than 15 mg per g solvent, higher than 20 mg per g solvent, higher than 25 mg per g solvent, higher than 30 mg per g solvent, higher than 40 mg per g solvent or higher than 50 m per g solvent.

[0070] The amount of water in the solvent mixture is preferably limited to less than 5 vol%, preferably, less than 2 vol% or less than 1 vol%. Preferably, the solvent mixture does not containwater (0 vol% water). The presence of water has a significant impact on polyurethane dissolution as water acts as an antisolvent. Water reduces the solubility of polyurethane in the solvent mixture, causing the polyurethane to precipitate.

[0071] The method according to the present invention may further comprise the step of recovering the polyurethane from the solution. The polyurethane can be recovered from the solution by any technique known in the art, for example by precipitation or evaporation. A preferred method comprises precipitation by adding an anti-solvent, for example water. Subsequently, the precipitated polymer material can be recovered from the solvent / anti-solvent solution by filtration.

[0072] The method according to the present invention may further comprise the step of removing the remaining textile from the solution while polyurethane remains dissolved in the solution.

[0073] Furthermore, the method according to the present invention may comprise the step of recovering polyurethane from the solution.

[0074] According to a second aspect of the present invention a solvent mixture suitable for selectively dissolving polyurethane from a textile, in particular from a textile comprising polyurethane fibers or polyurethane-based fibers. The solvent mixture is also suitable for selectively dissolving polyurethane form a textile comprising a polyurethane coating of a polyurethane-based coating and for textiles comprising a combination of polyurethane fibers or polyurethane-based fibers and a polyurethane or polyurethane-based coating.

[0075] The solvent mixture preferably comprises at least 50 vol% urea-based compound or a thiourea-based compound or at least 50 vol% urea-based and thiourea-based compound;20 - 50 vol% non-ionic surfactant.

[0076] A preferred solvent mixture comprises a compound having an ethoxylated alcohol unit as non-ionic surfactant. The hydrophobic structure of the non-ionic surfactant comprises for example a carbon chain having 4 to 15 carbon atoms.

[0077] Particular examples of non-ionic surfactants comprise Tergitol 15-S-5, Triton X-100, diethylene glycol monobutyl ether (DGMBE) and ethylene glycol monobutyl ether (EGMBE).

[0078] Particularly preferred solvent mixtures comprise 70 vol% of a urea-based compound and 30 vol% of a non-ionic surfactant as for example dimethyl urea (DMU) and 70 vol % diethylene glycol monobutyl ether (DGMBE); 70 vol% tetramethyl urea (TMU) and 30 vol% diethylene glycol monobutylether (DGMBE). Alternative embodiments comprise 50 vol% of an urea-based compoundand 50 vol% of a non-ionic surfactant as for example 50 vol% TMU and 50 vol% ethylene glycol monobutyl ether (EGMBE).

[0079] The amount of water in the solvent mixture is preferably limited to less than 5 vol%, preferably, less than 2 vol% or less than 1 vol%. Preferably, the solvent mixture does not contain water (0 vol% water). The presence of water has a significant impact on polyurethane dissolution as water acts as an antisolvent. Water reduces the solubility of polyurethane in the solvent mixture, causing the polyurethane to precipitate.

[0080] These and further aspects and preferred embodiments of the invention are described in the following sections and in the appended claims. The subject-matter of the appended claims is hereby specifically incorporated in this specification.Brief description of the drawings

[0081] The present invention will be discussed in more detail below, with reference to the attached drawings, in which:Figure 1 shows the Thermogravimetric - Fourier Transform Infrared Spectroscopy analysis (TGA-FTIR) of a polyamide / elastane sample treated with a mixture of dimethyl urea (DMU) and diethylene glycol monobutylether (DGMBE) as described in example 2. The upper spectrum in Figure 1 shows the spectrum before the treatment while the lower spectrum in Figure 1 shows the spectrum after the treatment;Figure 2 shows the Thermogravimetric - Fourier Transform Infrared Spectroscopy analysis (TGA-FTIR) of a polyester / elastane sample treated with a mixture of tetramethyl urea (TMU) and ethylene glycol monobutyl ether 2-butowyyethanol (EGMBE) as described in example 6. The upper spectrum in Figure 2 shows the spectrum before the treatment while the lower spectrum in Figure 2 shows the spectrum after the treatment;Description of embodiments

[0082] The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings are only schematic and are non-limiting. The size of some of the elements in the drawing may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.

[0083] When describing the invention, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise.

[0084] As used in the specification and the appended claims, the singular forms "a", "an," and "the" include plural referents unless the context clearly dictates otherwise. By way of example, "a step" means one step or more than one step.

[0085] The term ‘and / or’ when listing two or more items, means that any one of the listed items can by employed by itself or that any combination of two or more of the listed items can be employed.

[0086] The terms ‘first’, ‘second’ and the like used in the description as well as in the claims, are used to distinguish between similar elements and not necessarily describe a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

[0087] When referring to the endpoints of a range, the endpoints values of the range are included. The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g. 1 to 5 can include 1 , 2, 3, 4 when referring to, for example, a number of elements, and can also include 1 .5, 2, 2.75 and 3.80, when referring to, for example, measurements). The recitation of endpoints also includes the end point values themselves (e.g. from 1.0 to 5.0 includes both 1.0 and 5.0). Any numerical range recited herein is intended to include all sub-ranges subsumed therein.

[0088] As mentioned above, the term ‘solubility capacity’ is the maximum amount of a substance (solute) that can dissolve in a given quantity of solvent at a specific temperature and pressure (for example at 25 °C (298.15 K) and 1 atm (101 .325 kPa)). For the purpose of the present invention the solubility capacity is expressed as mass of the substance (solute) (in mg) (solute) divided by the mass of the solvent or solvent mixture solvent (in g) or expressed in wt%.

[0089] The term ‘textile-to-solvent ratio’ refers to the amount of textile material relative to the amount of solvent or solvent mixture used to dissolve the textile material. For the purpose of the present invention the textile-to-solvent ratio is defined as the mass of the textile divided by the mass of the solvent or the mass of the textile divided by the mass of the solvent mixture and is expressed in wt%.ExamplesExample 1

[0090] Pure elastane filaments composed of thermoplastic elastomeric polyurea urethane were brought into contact with 100 vol% tetramethyl urea (TMU) at 25°C for 15 minutes. After the treatment, the solution was cooled down to room temperature and then centrifugated for 30 minutes in order to remove insolubilized yarns and additives released from the dissolved filaments. The amount of polymer dissolved in the clear supernatant was quantified by using thermogravimetric analysis (TGA) connected to a Fourier-Transform Infrared Spectroscopy (FTIR). Based on the results, 40 mg of elastane was dissolved per g of TMU used. This solubility capacity of elastane is 4 wt%. Disappearance of the elastane filaments was also confirmed visually.Example 2

[0091] A textile blend composed of 80 wt% polyamide and 20 wt% elastane was brought into contact with a solvent mixture comprising 30 vol% dimethyl urea (DMU) and 70 vol % diethylene glycol monobutyl ether (DGMBE) at 100 °C for 2 hours at 1 :20 textile-to-solvent mixture ratio. Afterwards, the sample was removed from the solution, washed two times with water, dried at 60 °C to determine the mass loss during the treatment. TGA-FTIR analysis was also performed on the recovered solution, which proved that 20% elastane in the textile blend was removed successfully. The solubility capacity of elastane is 1 wt%. The FTIR data obtained from the TGA-FTIR analysis before and after the treatment is given in Figure 1 .Example 3

[0092] A swimsuit textile sample composed of 80 wt% of polyamide and 20 wt% of elastane was treated with a solvent mixture comprising 30 vol% diethylene glycol monobutylether (DGMBE) and 70 vol% tetramethyl urea (TMU) at 100°C for 1 hour at 1 :10 textile-to-solvent mixture ratio. After the treatment, the solution was cooled down to room temperature and then centrifugated for 30 minutes in order to remove insolubilized yarns and additives released from the dissolved filaments. The amount of polymer dissolved in the clear supernatant was quantified by using TGA-FTIR, which proved that 20 wt% of elastane was removed from the textile blend successfully. The solubility capacity of elastane is 2 wt%.Example 4

[0093] A textile blend composed of 90 wt% polyamide and 10 wt% elastane was brought into contact with a solvent mixture comprising 50 vol% TMU and 50 vol% ethylene glycol monobutyl ether (EGMBE) solution at 100 °C for 1 hour at 1 :10 textile-to-solvent mixture ratio. After the treatment, the solution was cooled down to room temperature and then centrifugated for 30 minutes in order to remove insolubilized yarns and additives released from the dissolved filaments. The amount of polymer dissolved in the clear supernatant was quantified by using TGA-FTIR, which proved that 10 wt% of elastane was removed from the textile blend successfully.Example 5

[0094] Pure elastane filaments were brought into contact with a solvent mixture comprising 50 vol% TMU and 50 vol% Tergitol 15-S-5 mixture at 100°C for 2 hours. After the treatment, the solution was cooled down to room temperature and then centrifugated for 30 minutes in order to remove insolubilized yarns. The amount of polymer dissolved in the clear supernatant was quantified by TGA-FTIR. Based on the results, 50 mg of elastane was dissolved per g of solvent mixture (5 wt%). Disappearance of the elastane filaments was also confirmed visually.Example 6

[0095] A fabric sample having a density of 0.046 g / cm3comprising 92 wt% polyester and 8 wt% elastane, was treated with a solvent mixture comprising 50 vol% TMU and 50 vol% EGMBE at 100 °C for 1 hour using a 1 :10 textile-to-solvent mixture ratio. After the treatment, the fabric was separated from the hot solvent mixture by filtration, rinsed sequentially with water and ethanol, and dried at 80 °C until a constant weight was reached. Once cooled, the solvent blend was centrifuged to remove undissolved material, and the supernatant was analyzed by TGA-FTIR to quantify the dissolved elastane. The analysis confirmed that the elastane originally present in the textile was effectively removed. Furthermore, the absence of polyurethane-specific markers in the recovered textile was verified by TG-FTIR, providing additional confirmation of elastane removal (Figure 2).Example 7

[0096] A textile blend composed of 47.5 wt% PET, 47.5 wt% cotton and 5 wt% elastane was brought into contact with a solvent mixture comprising 50 vol% TMU and 50 vol% ethylene glycol monobutyl ether (EGMBE) solution at 100 °C for 1 hour at 1 :20 textile-to-solvent mixture ratio. After the treatment, the solution was cooled down to room temperature and then centrifugated for 30 minutes in order to remove insolubilized yarns and additives released from the dissolved filaments. The amount of polymer dissolved in the clear supernatant was quantified by using TGA-FTIR, which proved that 5 wt% of elastane was removed from the textile blend successfully.Example 8

[0097] A textile blend composed of 65 wt% PET, 34 wt% cotton and 1 wt% elastane was brought into contact with a solvent mixture comprising 50 vol% TMU and 50 vol% diethylene glycol monobutyl ether (DEGMBE) solution at 100 °C for 1 hour at 1 :20 textile-to-solvent mixture ratio. After the treatment, the solution was cooled down to room temperature and then centrifugated for 30 minutes in order to remove insolubilized yarns and additives released from the dissolved filaments. The amount of polymer dissolved in the clear supernatant was quantified by using TGA- FTIR, which proved that 1 wt% of elastane was removed from the textile blend successfully.

Claims

P2024 / 066-15-Claims1. A method for selectively dissolving polyurethane from a textile, the method comprising the steps of providing a textile comprising polyurethane fibers and / or polyurethane-based fibers and / or comprising a polyurethane coating and / or a polyurethane based coating; contacting the textile with a solvent to dissolve the polyurethane fibers and / or polyurethane- based fibers and / or to dissolve the polyurethane coating and / or the polyurethane based coating thereby forming a solution, the solvent comprising a urea-based compound and / or a thiourea-based compound.

2. The method according to claim 1 , wherein the textile comprises polyurethane fibers and / or polyurethane-based fibers and at least one other type of fibers.

3. The method according to claim 1 or claim 2, further comprising the step of removing the remaining textile from the solution while polyurethane remains dissolved in the solution.

4. The method according to any one of the preceding claims, further comprising the step of recovering polyurethane from the solution.

5. The method according to any one of the preceding claims, wherein the urea-based compound comprises a carbonyl group bonded to two nitrogen atoms and further provided with one or more substituted or non-substituted alkyl or cycloalkyl substituent(s) or wherein the urea-based compound comprises a carbonyl group bonded to two nitrogen atoms whereby the carbonyl group and the two nitrogen atoms are incorporated in a ring structure.

6. The method according to any one of the preceding claims, wherein the thiourea-based compound comprises a -(C=S)- group bonded to two nitrogen atoms and further provided with one or more substituted or non-substituted alkyl or cycloalkyl substituent(s) or wherein the thiourea-based compound comprises a -(C=S)- group bonded to two nitrogen atoms whereby the carbonyl group and the two nitrogen atoms are incorporated in a ring structure.

7. The method according to any one of the preceding claims, wherein the urea-based compound is selected from the group consisting of dimethylurea, trimethylurea or tetramethylurea.

8. The method according to any one of the preceding claims, wherein the textile and the solvent are contacted under mechanical agitation.P2024 / 066-16-9. The method according to anyone of the preceding claims, wherein the solvent further comprises a surfactant, preferably a non-ionic surfactant, in a concentration ranging between 0 and 50 vol %.

10. The method according to claim 9, wherein the non-ionic surfactant comprises a compound having an ethoxylated alcohol unit.

11. The method according to any one of the preceding claims, wherein the at least one other type of fibers comprises natural fibers or man-made fibers.

12. The method according to any one of the preceding claims, wherein the textile comprises a fiber, a yarn, a fabric or an end-product comprising a fabric.

13. A solvent mixture suitable for selectively dissolving polyurethane from a textile comprising polyurethane or polyurethane-based fibers and / or a polyurethane or polyurethane-based coating, the solvent mixture comprising at least 50 vol% urea-based compound or a thiourea-based compound or at least 50 vol% urea-based and thiourea-based compound;20 - 50 vol% non-ionic surfactant.

14. The solvent mixture according to claim 13, wherein the mixture does not contain water.

15. The solvent mixture according to claim 14, wherein the non-ionic surfactant comprises a compound having an ethoxylated alcohol unit.

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