TECHNICAL FIELD

The present disclosure relates to a method for hydrolysis of a polyester. The present disclosure relates more particularly, but not necessarily exclusively, to a method for the recycling of polyester- containing materials, such as textiles, fabrics and articles of clothing/garments.

BACKGROUND

Recycling polyester-containing materials, such as textiles, fabrics and articles of clothing/garments, is not only important for sustainability and the environment, but is essential as part of the transition to a circular economy. For example, increased use of recycled polyester reduces the demand for hydrocarbons (which are typically used in the synthesis of polyesters), lowers the quantity of waste material requiring landfill and reduces emissions from the incineration of waste material, etc.

Polyester-containing materials in the form of textiles and fabrics etc. are composed of long chains of repeating units which can be intertwined to form fibres. Existing techniques for polyester recycling include mechanical and chemical methods, which can be distinguished by their effect on these fibres.

Mechanical methods involve shredding and melting the polyester-containing material, breaking apart the fibres but keeping the individual polyester chains intact. The resulting molten material can then be spun into new fibres. However, this typically results in recycled fibres which are more brittle than in the original polyester, and therefore the recycled fibres are typically mixed with new fibres to maintain the required quality.

Chemical methods of polyester recycling can produce recycled material of a suitable high quality enabling the remanufacture of like-for-like materials and products as part of a circular economy. However, current methods typically employ high temperatures to breakdown the polyester into its constituent monomers and so require a large net input of energy. These temperatures can also cause degradation of valuable fillers and colourants (e.g. glass reflective microspheres) preventing their recovery from the depolymerised mixture.

It would be desirable to provide a method for hydrolysis of a polyester that has improved efficiency (e.g. that requires less energy) and/or allows for the recovery of valuable fillers and colourants, and/or to obviate, mitigate and/or ameliorate one or more deficiencies in existing methods, whether identified herein or otherwise. It is desirable that recycling processes can produce high quality materials and/or products to be re manufactured into the same or equivalent products with lower in-process impacts such as energy and consumption of other materials, and/or significant reductions in process and product waste. SUMMARY

According to a first aspect of the present disclosure, there is provided a method for hydrolysis of a polyester, the method comprising mixing the polyester with pentanol to form a hydrolysis mixture; and hydrolysing the polyester, wherein said hydrolysing the polyester is at a temperature up to 100°C.

According to a second aspect there is provided a use of pentanol in the hydrolysis of a polyester at a temperature up to 100°C.

DEFINITIONS

The following definitions apply for terms used herein. In the event that any term is not specifically defined here or otherwise, the standard meaning in the present technical field prevails. This standard meaning may bear in mind definitions provided in common general knowledge (e.g. standard textbooks) in the present technical field. Usefully, for example, chemical terms may be interpreted in accordance with the IUPAC Gold Book Version 3.0.1 .

The terms “about”, “around”, or “substantially” generally encompass or refer to a range of values that one skilled in the art would consider equivalent to the recited values (e.g. having substantially the same function or result, and/or achieved in substantially the same way). Suitably, where such a term is used in relation to a numerical value, it can represent (in increasing order of preference) a 10%, 5%, 2%, 1% or 0% deviation from that value.

The term “monomer” is one of the art. For the avoidance of any doubt, monomers are molecules that can be bonded to other molecules to form a polymer or a copolymer comprising units of the monomer. Here, it will be appreciated that a monomer used to form the polymer changes chemically as it becomes subsumed within the polymer: the skilled person will understand that a residue of the monomer is what remains, subsumed within the polymer. For example, ethylene glycol can be copolymerised with terephthalic acid to produce polyethylene terephthalate (PET). Here, ethylene glycol is subsumed within the polyethylene terephthalate (PET) polymer as ethylene residues. For convenience of nomenclature herein, various substituent units in a polymer are referred to by the names of their substituent/origin monomer names, rather than the resulting residues. The skilled person will understand how these substituent/origin monomer names relate to the resulting residues.

The term “polymer” as used herein may refer to a molecule comprising two or more (such as three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, or ten or more) monomer units. A polymer may comprise many monomer units, such as 100 or more monomer units. As used herein, the term “polyethylene terephthalate”, abbreviated to “PET”, refers to a specific polymer having the chemical structure: wherein “y” is an integer of one or more (such as three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, or ten or more), representing the number of monomer units in the polymer. PET may comprise many monomer units, such as 100 or more monomer units.

A typical molecular weight for PET may be:

(a) at least around 1 kDa, optionally at least around 10 kDa, optionally at least around 20 kDa, optionally at least around 30 kDa, optionally at least around 40 kDa; and/or

(b) at most around 1000 kDa, optionally at most around 500 kDa, optionally at most around 400 kDa, optionally at most around 300 kDa, optionally at most around 200 kDa; and/or

(c) around 1 to 1000 kDa, optionally around 10 to 500 kDa, optionally around 20 to 400 kDa, optionally around 30 to 300 kDa, optionally around 40 to 200 kDa.

It can also be assumed that the ends of polymers and/or co-polymers referred to herein have filled valences, e.g. through bonding to atoms, such as hydrogen, or groups of atoms.

Where the amount of a particular component is expressed as a wt% being the weight of the particular ingredient “in the total weight of the hydrolysis mixture” (or other mixed component, such as the textile, fabric and/or article of clothing/garment), this may be calculated as follows: weiqht of particular inqredient wt% = - ■ , - , : - x 100 total weight of hydrolysis mixture

The term “at least one” is synonymous with “one or more”, e.g. one, two, three, four, five, six, or more.

The term "aliphatic", as used herein, means a straight-chain, branched or cyclic hydrocarbon, which is completely saturated, or which contains one or more units of unsaturation (e.g. alkenyl or alkynyl), but which is not aromatic. Where the aliphatic group refers to a range, such as Ci to Cw, it is to be understood that it includes each member of the range, i.e. Ci, C2, C3, C4, C5, Ce, etc. The term “Ci to Ce” aliphatic as used herein means an aliphatic group having 1 to 6 carbon atoms, which may be branched or unbranched, saturated or unsaturated and optionally contains a ring.

The term “alkyl” refers to a saturated (no double or triple bonds) aliphatic hydrocarbon radical, including straight-chain, and, where possible, branched-chain and cyclic groups and hybrids thereof, such as (cycloalkyl)alkyl. Where the alkyl group refers to a range, such as Ci to C10, it is to be understood that it includes each member of the range, i.e. Ci, C2, C3, C4, C5, Ce, etc. The term “Ci to Ce alkyl” as used herein means an alkyl group having 1-6 carbon atoms, which may be branched or unbranched and optionally contains a ring.

As used herein, “alkenyl” refers to an alkyl group that contains in the straight or branched hydrocarbon chain one or more double bonds. Examples of alkenyl groups include allenyl, vinylmethyl and ethenyl.

As used herein, the term “pentanol” refers to an alcohol of formula C5H12O and isomers thereof. Pentan-1 -ol (CH3CH2CH2CH2CH2OH) is a preferred implementation throughout. The solubility of pentan-1 -ol in water as used herein is about 22 g/L at 22°C. The pentan-1 -ol as used herein may be obtained from ThermoFisher Scientific (New Jersey, United States), CAS 71-41-0 and used without further purification.

As used herein, the term “textile” is intended to refer to a material formed from interlocking fibres or threads. Textiles may be produced by various methods known to persons of skill in the art, such as by weaving, bonding, felting, knitting, braiding and the like. The term encompasses clothing and garments, such as durable garments (e.g. for hard-wearing purposes) e.g. waterproof garments.

The term “density separation” as used herein is intended to refer to the separation of two or more substantially immiscible liquids, which comprises their mixing of the two liquids and generation of two or more phases. The phases are formed in order of the relative density of the liquids, allowing the liquids to be selectively decanted and separated. For example, as used herein, a solution comprising a mixture of water and pentanol can be separated due to the higher density of water (about 1000 kg/m ³ ) compared to pentanol (about 810 kg/m ³ ).

The term “vacuum filter” as used herein is a technique for separating a solid product from a liquid, wherein the solid and liquid mixture are poured or passed over a filter (optionally a paper filter), the filter trapping the solid material and the liquid being drawn into a receptacle through the use of reduced pressure/vacuum.

As used herein, the “size” of an item piece (e.g. of textile or fabric) refers to the two-dimensional surface area of a major face (largest sized face) of an item. For a substantially rectangular item is calculated by x * y, wherein x is the width and y is the length, where the width and length are the two longest dimensions of said item piece. LIST OF TABLES AND FIGURES

The disclosure will now be described with reference to the following Tables and Figures:

Fig. 1 : Process flow diagram for Example 1 .

Fig. 2: HPLC method and chromatogram for the terephthalic acid produced by the method in

Example 1 .

Fig. 3: TGA/DSC curves for terephthalic acid product from the method in Example 1 .

Fig. 4: ¹ H NMR spectrum of terephthalic acid produced by the method in Example 1 .

Fig. 5: ¹³ C NMR spectrum of terephthalic acid produced by the method in Example 1.

Fig. 6: Process flow diagram for an implementation of the present disclosure.

Table 1 : Optimisation table indicating signal-to-noise ratio for various conditions as indicated

(Example 2).

DETAILED DESCRIPTION

According to a first aspect of the present disclosure, there is provided a method for hydrolysis of a polyester, the method comprising mixing the polyester with pentanol to form a hydrolysis mixture; and hydrolysing the polyester, wherein said hydrolysing the polyester is at a temperature up to 100°C.

According to a second aspect there is provided a use of pentanol in the hydrolysis of a polyester at a temperature up to 100°C.

The method and use of the present disclosure provide a convenient and/or efficient technique for recycling polyester materials. Polyester such as PET is a typical major (structural) component of many fabrics, garments and textiles (particularly high-performance items, such as workwear).

Hydrolysis is a suitable technique for the recycling of polyester material. This breaks ester linkages between monomer units in the polyester material, yielding a de-polymerised mixture of constituent monomer units. In the context of PET, for example, the constituent monomer units are terephthalic acid (TPA) and ethylene glycol (EG). Hydrolysis and depolymerisation in this way allows said monomer units to be isolated and recovered. It will be appreciated that this enables a reduction in the demand for natural resources (e.g. hydrocarbons derived from oil or natural gas). Moreover, this lowers the quantity of waste material requiring landfill, reduces emissions from the incineration of waste material, etc.

Pentanol provides a suitable media for the hydrolysis reaction. It is compatible with the polyester material (e.g. it readily dissolves polyester materials) and other hydrolysis reagents (e.g. bases) and thereby enables the hydrolysis reaction to take place.

Pentanol provides a suitable media for the hydrolysis reaction. The alkaline hydrolysis of esters described here is a reaction between an uncharged ester molecule and a hydroxyl ion. The pentanol does not formally participate in chemical reactions however it serves as the reaction medium to enable the chemical reaction to occur more rapidly and with lower input energy.

It has been found that the use of pentanol for the hydrolysis of a polyester has particular advantages and a notably-reduced overall environmental impact (e.g. as compared with other methodologies including other liquid media). Pentanol is substantially insoluble in water. This means that a simple washing step (with an aqueous solvent such as water) can be used to separate various components from the pentanol, such as excess/un reacted base (in the context of basic hydrolysis).

Once washed/separated, the pentanol may be substantially pure (e.g. at least about 75% pure, optionally at least about 85% pure, optionally at least about 95% pure, referring to the weight of pentanol in the total weight of a liquid sample resulting from the washing/separating step) and can therefore be recovered and reused (e.g. in subsequent hydrolysis reactions/cycles). There is therefore a lower demand for the pentanol and the lack of further purification steps reduces the energy consumed by the method.

Other processes, employing different liquid media, may not benefit from the above features. For example, methanol and/or water are typically-used liquid media in ester hydrolysis. However, methanol is soluble/miscible with water and hence cannot be separated in the manner outlined above. Water clearly suffers from similar issues.

It has also been found that the present methods and use, involving pentanol, allow the hydrolysis of said polyester to be carried out at a relatively low temperature (e.g. up to 100°C), and hence in a more energy efficient manner.

The temperatures employed in this method/use (100°C or below) are relatively mild and allow hydrolysis to take place primarily with respect to the polyester components, whereas other, nonpolyester, polymer components (e.g. Nylon, Elastane, PTFE) may remain substantially intact. This permits recovery of such other polymeric components, further improving environmental impact as noted above. Moreover, this means that end-products produced by the method and use of the present disclosure (e.g. the constituent monomer units TPA and EG) remain relatively uncontaminated by the other polymeric components (or breakdown products thereof).

Similarly, the relatively mild temperatures used mean that valuable other components (e.g. glass reflective microspheres; fluorescent, soil phase fillers optionally metallic fluorescent soil phase fillers such as dialuminium and dysprosium compounds) are remain substantially intact (are substantially not degraded) and thus can also be recovered untransformed by the hydrolysis method. Such components are regularly present in fabrics, garments and textiles (particularly high-performance items, such as workwear). For example, glass reflective microspheres may commonly be found in reflective workwear.

Overall, the method and use of the present disclosure thereby represent a convenient all-in-one methodology for recycling an array of polyester-containing materials, such as fabrics, garments and textiles. Moreover, since these are chemical methods, these do not suffer from some of the drawbacks of mechanical methods as described above.

In some implementations, said hydrolysis is basic hydrolysis and the hydrolysis mixture further comprises a base. This is a preferred implementation throughout the present disclosure. Basic hydrolysis of polyester produces a carboxylic acid salt which may be insoluble in pentanol. For example, if the polyester to be hydrolysed is PET, and the hydrolysis mixture comprises potassium hydroxide as a base, one of the products will be potassium terephthalate, which forms a precipitate. This therefore facilitates recovery of this product by filtration.

The base may be an alkali metal hydroxide or an alkaline earth metal hydroxide; optionally selected from sodium hydroxide, potassium hydroxide, or the like, or a combination thereof; preferably wherein said base is potassium hydroxide. Many salts formed from such bases are insoluble in the pentanol solvent, and hence form a precipitate which can be removed by simple filtration as discussed above.

The base may be provided at a wt% of at least around 7.5%, optionally at least around 8%, optionally at least around 8.5%, optionally at least around 9%, optionally at least around 9.5%; and/or at most around 11 .5%, optionally at most around 11%, optionally at most around 10.5%; and/or around 7.5% to 11 .5%, optionally around 8% to 11%, optionally around 8.5% to 11%, optionally around 9.5% to 10.5%, preferably around 10%, the wt% being the weight of base in the total weight of the hydrolysis mixture.

The base may be provided at a wt% of at least around 7.5%, optionally at least around 8%, optionally at least around 8.5%, optionally at least around 9%, optionally at least around 9.5%; and/or at most around 12%, optionally at most around 11 .5%, optionally at most around 11%, optionally at most around 10.5%; and/or around 7.5% to 12%, optionally around 7.5% to 11 .5%, optionally around 8% to 11%, optionally around 8.5% to 11%, optionally around 9.5% to 10.5%, preferably around 10%, the wt% being the weight of base in the total weight of the hydrolysis mixture.

The pentanol and base may be provided at a weight ratio of: at least around 15:3 pentanol to base, optionally at least around 17:3, optionally at least around 18:3, optionally at least around 19:3; and/or at most around 25:3 pentanol to base, optionally at most around 23:3, optionally at most around 22:3, optionally at most around 21 :3; and/or around 15:3 to 25:3 pentanol to base, optionally around 17:3 to 23:3, optionally around 18:3 to 22:3, optionally around 19:3 to 21 :3, optionally around 20:3; based on the weights of pentanol and base in the hydrolysis mixture.

The hydrolysis mixture may further comprise a base (basic hydrolysis) or an acid (acidic hydrolysis) . All implementations are envisaged in the present disclosure.

In some implementations, the hydrolysis mixture comprises an acid. The acid may be hydrochloric or sulphuric acid.

The acid may be provided at a wt% of: at least around 60%and/or at most around 85%; and/or around 60% to 85%, the wt% being the weight of acid in the total weight of the hydrolysis mixture.

The pentanol may suitably be pentan-1 -ol.

In some implementations (preferably wherein the hydrolysis is basic hydrolysis) the pentanol may be provided at a wt% of at least around 60%, optionally at least around 62%, optionally at least around 64%, optionally at least around 66%, optionally at least around 68%; and/or at most around 80%, optionally at most around 78%, optionally at most around 76%, optionally at most around 74%, optionally at most around 72%; and/or around 60% to 80%, optionally around 62% to 78%, optionally around 64% to 76%, optionally around 66% to 74%, optionally around 68% to 72%, preferably around 70%, the wt% being the weight of pentanol in the total weight of the hydrolysis mixture.

The polyester may comprise aromatic dicarboxylic acid monomer units, optionally benzene dicarboxylic acid monomer units, optionally terephthalic acid monomer units. Examples of suitable polyester materials include, but are not limited to, polyethylene terephthalate (PET). In some implementations, the polyester may comprise aliphatic units, optionally alkylene, optionally straight chain alkylene, optionally Ci-Ce alkylene, optionally C2-C6 alkylene, optionally C2-C4 alkylene, optionally C2-C3 alkylene, optionally C2 alkylene/ethylene. In some implementations the polyester is a copolymer, comprising aliphatic units as described herein. In some implementations, the polyester is polyethylene terephthalic acid - these are preferred implementation throughout.

It will be appreciated that polyethylene terephthalic acid may comprise a copolymer wherein a number of terephthalic acid (diacid) or ethylene glycol (diol) monomer units (residues) may be substituted with other diols or diacids. The method and use of the present disclosure may equally be applied to the hydrolysis of such substituted copolymers.

The polyester may be provided at a wt% of at least around 10%, and/or at most around 30%, and/or around 10% to 30%, optionally around 20% the wt% being based on the weight of polyester in the total weight of the hydrolysis mixture.

The polyester may be provided at a wt% of at least around 10%, optionally at least around 15% and/or at most around 30%, optionally at most around 25% and/or around 10% to 30%, optionally around 15% to 25%, optionally around 20% the wt% being based on the weight of polyester in the total weight of the hydrolysis mixture.

In some implementations (preferably wherein the hydrolysis is basic hydrolysis) the hydrolysing the polyester is at a temperature of at least around 50°C, optionally at least around 60°C, optionally at least around 65°C; and/or at most around 95°C, optionally at most around 90°C, optionally at most around 85°C, optionally at most around 80°C, optionally at most around 79°C, optionally at most around 75°C, optionally at most around 70°C; and/or around 50°C to 100°C, optionally around 60°C to 90°C, optionally around 60°C to 80°C; optionally around 60°C to 79°C, optionally around 65°C to 75°C .

In some implementations (preferably wherein the hydrolysis is basic hydrolysis) said mixing is for at least around 10 minutes, optionally at least around 20 minutes, optionally at least around 30 minutes, optionally at least around 45 minutes; and/or at most around 5 hours, optionally at most around 3 hours, optionally at most around

1 .5 hours; and/or around 10 minutes to 5 hours, optionally around 30 minutes to 3 hours, optionally around 45 minutes to 1 .5 hours, optionally around 1 hour. It has been found that the method and use of the disclosure described herein may allow for shorter reaction times than comparable methods and uses known in the art. This is a result of the increased chemical activity of pentanol as compared to other solvents such as methanol, which results in an efficient hydrolysis process.

In some implementations (preferably wherein the hydrolysis is basic hydrolysis) the mixing is performed by use of a mechanical stirrer, optionally stirring at a speed of at least around 30 rpm; and/or at most around 600 rpm, and/or optionally around 30 rpm to 600 rpm.

In some implementations, mixing may comprise agitation with a fluid (e.g. a fluid which is not substantially reactive with the hydrolysis mixture, e.g. not reactive with the polyester and/or base). It has been found that agitation with a fluid avoids clogging of the polyester by increasing movement and flow within the hydrolysis mixture. This has been found to increase the overall efficiency of hydrolysis.

The fluid may be or have been heated, e.g. to a temperature which does not substantially alter the hydrolysis mixture, optionally wherein the temperature is up to 100°C. The method may comprise heating the fluid prior to adding to the hydrolysis mixture. This may aid with keeping the hydrolysis mixture at a substantially constant temperature.

The fluid may be a gas, optionally air. The fluid/gas/air may be delivered to a vessel containing the hydrolysis mixture (e.g. at the bottom thereof). Delivery may be at a rate sufficient to increase the volume of the hydrolysis mixture, e.g. by around 25% to 50%, optionally around 30% to 40%, optionally around 30 to 35%, optionally around 33%.

The gas may be bubbled through the hydrolysis mixture via one or more jets and/or propellers (preferably one or more jets).

The gas may be bubbled through the hydrolysis mixture (e.g. via the one or more jets and/or propellers) at a flow rate of around 5 to 10 L min ¹ (for a representative 2 L reaction vessel), optionally around 6 to 9 L min ¹ , optionally around 6.5 to 8.5 L min ¹ , optionally around 7 to 8 L min ¹ , optionally around 7.5 L min ¹ .

The vessel may be larger than 2 L, in which case the flow rate would scale accordingly. For example, in a 10 L vessel, the gas may also be bubbled through the hydrolysis mixture via one or more jets and/or propellers (preferably one or more jets) at a flow rate of around 25 to 50 L min ¹ , optionally around 30 to 45 L min ¹ , optionally around 32.5 to 42.5 L min ¹ , optionally around 35 to 40 L min ¹ , optionally around 37.5 L min ¹ . The gas may be bubbled through the hydrolysis mixture (e.g. via the one or more jets and/or propellers) at a flow rate giving rise to an <2 value of around 1 to 6.5 min ¹ , optionally around 1 .75 to

5.75 min ¹ , optionally around 2.5 to 5 min ¹ , optionally around 3 to 4.5 min ¹ , optionally around

3.75 min ¹ , wherein <2 is defined as:

For example, the flow rate for a 2 L vessel may be around 7.5 L min ¹ and the <2 value in this instance would be around 3.75 min ¹ .

In some implementations, the fluid may be a diluting agent, optionally water or ethylene glycol, preferably water (e.g. the method may further comprise diluting the hydrolysis mixture using a diluting agent). The diluting agent may be provided at a wt% of: at least around 5%, optionally at least around 10%, optionally at least around 15%, optionally at least around 20%, optionally at least around 25%, optionally at least around 30%; and/or at most around 65%, optionally at most around 60%, optionally at most around 55%, optionally at most around 50%, optionally at most around 45%, optionally at most around 40%; and/or around 5% to 65%, optionally around 10% to 60%, optionally around 15% to 55%, optionally around 20% to 50%, optionally around 25% to 45%, optionally around 30% to 40%; the wt% being the weight of diluting agent in the total weight of the hydrolysis mixture.

Including a diluting agent in the hydrolysis mixture increases the overall volume of the hydrolysis mixture. This allows more polyester to be added for a given amount of pentanol, thereby increasing the efficiency of the hydrolysis.

Said hydrolysing the polyester may be at ambient or standard atmospheric pressure (around 100 kPa, e.g. around 101 kPa). It has been found that carrying out the hydrolysis of the polyester at such pressures avoids the degradation of fillers (e.g. glass microspheres/bubbles) in the reaction mixture and therefore facilitates their recovery.

The polyester may be a component of a textile and/or a fabric and/or an article of clothing/garment. Examples include durable garments, including but not limited to, safety garments, jackets and waterproofs. All such examples are suitable sources of polyester for use in the present disclosure.

The textile, fabric and/or article of clothing/garment may further comprise cotton, polyethylene, polyvinyl chloride, polytetrafluoroethylene or other fluorinated coatings (e.g. Gortex), nylon, elastane, and/or a combination thereof. Suitable examples include flame-resistant fabric, reflective striping, antistatic fabric, fabrics approved for use in ATEX environments, retro-reflective tapes, GORE-TEX (or other fluorinated coatings), waterproofing strips, chemical splash coatings, and wear resistant coatings. Such materials typically include valuable other components (e.g. glass reflective microspheres) as discussed above. It is particularly desirable to recover such components when the method and use of the present disclosure is applied to such textiles, fabrics and/or articles of clothing/garment. The lower temperature and pressure of the method and use of the present disclosure as, compared to other processes known in the art, may allow these valuable other components to be removed by filtration after hydrolysis of the polyester, without contamination of the desired hydrolysis products.

The textile, fabric and/or article of clothing/garment may further comprise one or more dyes (optionally a disperse dye). The one or more dyes may optionally be selected from:

(a) coumarin dyes, optionally selected from Colour Index Disperse Yellow 82 (2a), 184 (2d), 186 (3), 232 (2d) and Colour Index Disperse Reds 277 (5a) and 374 (5b); and/or

(b) aminonaphthalimide dyes, optionally selected from Colour Index Disperse Yellow 11 (6a) and Orange 32 (9); and/or

(c) benzothioxanthone dyes, optionally selected from Colour Index Disperse Red 303; and/or

(d) heterocyclic dyes, optionally Colour Index Disperse Yellow 139 (17); and/or

(e) fluorescent dyes, optionally a dye meeting the standard EN 471 :1997.

The hydrolysis method and use of the present disclosure may allow the recovery of said dyes without their degradation.

In some implementations, the method further comprises recovery of one or more molecular components (optionally one or more dyes), optionally wherein said recovery is with a molecular sieve (e.g. a microporous molecular sieve), optionally a zeolite or organically modified silanes molecular sieve, e.g. including silicoaluminophosphate and/or sulfonated organic-functionalized silica. Molecular sieves may, for example, be useful for recovery of the dyes noted above.

The molecular sieve may have pores with a size up to around 15 angstroms, optionally up to around 12 angstroms, optionally up to around 10 angstroms It has been found that molecular sieves with pores of a size in this range are suitable for use in recovery of molecular components from the hydrolysis mixture of the present disclosure (e.g. the dyes noted above). It will be appreciated by one skilled in the art that the micropores for use in the present disclosure may have uniform size, however this size can be varied in order to influence the shape selectivity of the micropores.

The textile, fabric and/or article of clothing/garment may further comprise a filler such as glass microspheres/bubbles, optionally wherein the glass is borosilicate such as soda lime borosilicate. In some implementations the method further comprises recovery of said filler (e.g. glass microspheres/bubbles), e.g. by filtration. Said textile, fabric and/or article of clothing/garment may comprise at least around 60 wt% polyester, based on the weight of the polyester in the total weight of the textile, fabric and/or article of clothing/garment.

In some implementations the method further comprises size reduction of the polyester (e.g. of said textile, fabric and/or article of clothing/garment), optionally by cutting into smaller pieces before mixing to form the hydrolysis mixture, optionally wherein the pieces have a size of less than about 2.5 cm ² , optionally less than around 1 cm ² ; optionally around 0.25 to 0.75 cm ² ; optionally around 0.5 cm ² .

It has been found that size reduction of the polyester improves the efficiency of the mixing of the polyester and pentanol, which reduces the reaction time. Without wishing to be bound by theory, this is because of the increased surface area provided by smaller pieces of polyester which increase the rate of the hydrolysis reaction.

Optimisation has highlighted the importance of surface area and the level of contamination present in the polyester to be hydrolysed. As opposed to the other depolymerisation processes known in the art, the higher surface area of the shredded polyester increases conversion efficiency. Furthermore, the lower crystallinity seen in polyesters derived from garments and fabrics (as opposed to that derived from bottles and hard plastics) has also been found to increase conversion efficiency. The limiting factor on conversion efficiency is the effective concentration of polyester per unit of fabric or textile to be hydrolysed (known as the loading %). This is influenced by factors such as the garment purity with respect to polyester and capacity of the reaction vessel in which the hydrolysis is conducted.

In some implementations the method may further comprise, after hydrolysing the polyester, cooling the hydrolysis mixture to up to around 30°C, optionally up to around 25°C, optionally between around 20°C and around 25°C; to form a cooled mixture, optionally wherein the cooled mixture comprises solid material, optionally wherein the solid material is selected from polyethylene, polyvinyl chloride, polytetrafluoroethylene or other fluorinated coatings (e.g. Gortex), nylon, elastane, and/or a combination thereof.

The hydrolysis mixture is optionally cooled after hydrolysis of the polyester. It has been found that cooling the hydrolysis mixture facilitates further filtration and/or separation steps. For example, this reduces the solubility of the products of the hydrolysis in the pentanol, therefore increasing the yield of recovered product. In other implementations, the method does not require cooling the hydrolysis mixture and said aqueous solvent is simply added to the hydrolysis mixture without cooling. In some implementations, the cooling the hydrolysis mixture is performed by means of an ice-bath.

In some implementations the method may further comprise removing the solid material from the cooled mixture, (optionally by filtration, optionally with a paper filter), optionally wherein said solid material comprises an organic component, optionally wherein said organic component is polyethylene, polyvinyl chloride, polytetrafluoroethylene or other fluorinated coatings (e.g. Gortex), nylon, elastane, and/or a combination thereof.

As mentioned above, certain hydrolysis techniques (e.g. basic hydrolysis) involve the formation of insoluble (salt) precipitates. Removal (e.g. by filtration) provides a convenient mechanism for recovery of such precipitates.

In some implementations, filtration may comprise one or more filtration steps, optionally wherein the filter is/are:

(i) a coarse filter; optionally having a pore size at most around 12 mm, optionally at most around 10 mm, optionally at most around 8 mm; and/or

(ii) a fine filter; optionally having a pore size at most around 6 mm, optionally at most around 4 mm, optionally at most around 2 mm; and/or

(iii) a fabric (e.g. cotton) filter; optionally having a pore size at most around 200 pm, optionally at most around 150 pm, optionally at most around 100 pm; and/or

(iv) a soil phase filter; optionally having a pore size at most around 30 pm, optionally at most around 20 pm, optionally at most around 10 pm; and/or

(v) an activated filter, optionally an activated carbon filter; optionally wherein filtration comprises more than one filtration steps, with filters having progressively smaller pore sizes and wherein the method comprises a plurality of progressive filtration steps (i) to (iv), optionally four filtration steps having corresponding filters (i), then (ii), then (iii) and then (iv), optionally further comprising filter (v).

Filtration (e.g. progressive filtration) in this way can be useful for separation and recovery of various items within an item (e.g. textile). For example, a coarse filter may be suitable for removing large insoluble materials, such as cotton badges; a fine filter may be suitable for removing cotton and glass microfibres; and an activated filter, such as an activated carbon filter, may be suitable for removing organic components from the (cooled) mixture; etc.

An activated filter, such as an activated carbon filter may also be suitable for removing metallic impurities (e.g. iron-, titanium- and/or zinc-containing impurities) from the mixture (e.g. the cooled mixture). Said metallic impurities may be substantially dissolved in the (cooled) mixture.

In some implementations the method further comprises adding an aqueous solvent (e.g. water, such as deionised water) to the cooled mixture to form a biphasic mixture comprising an organic phase (comprising pentanol) and liquid aqueous phase, optionally wherein the method further comprises separation of the biphasic mixture into separated organic and liquid phases, optionally by density separation. As mentioned above, pentanol is substantially insoluble in water. Adding an aqueous solvent can be used as a simple washing step to separate various components from the pentanol, such as excess/un reacted base (in the context of basic hydrolysis).

In some implementations the biphasic mixture comprises pentanol at a wt% of at least around 60%, optionally at least around 65%, optionally at least around 70%; and/or at most around 80%, optionally at most around 78%, optionally at most around 76%, optionally at most around 74%; and/or around 60% to 80%, optionally around 62% to 78%, optionally around 64% to 76%, optionally around 66% to 74%, optionally around 68% to 72%, preferably around 70%, the wt% being based on the weight of pentanol in the total weight of the biphasic mixture.

The method may further comprise recycling the separated organic phase (e.g. into another cycle of the method described above). This recycling of the organic phase (comprising pentanol) reduces the quantity of pentanol required to carry out the hydrolysis method as described herein.

The method may further comprise removing metallic impurities (e.g. iron-, titanium- and/or zinc- containing impurities), optionally by filtration, e.g. filtering with an activated filter (such as an activated carbon filter). Preferably, the activated filter is used to remove metallic impurities from the aqueous phase after separation.

Said activated filter may be granular (e.g. granules of activated carbon), optionally wherein said granules are around 2 to 6 mm in diameter. It has been found that activated granules contain pores which are suitable fortrapping metallic impurities. Granules that are around 2 to 6 mm in diameter are large enough to be easily recovered from the aqueous phase after removal of metallic impurities and small enough so that substantially all of the pores are capable of trapping metallic impurities.

Said removing metallic impurities may comprise mixing (optionally stirring) with the activated filter, e.g. with the aqueous phase, for: at least around 1 hour, optionally at least around 2 hours, optionally at least around 3 hours, optionally at least around 4 hours; and/or at most around 36 hours, optionally at most around 24 hours, optionally at most around 12 hours, optionally at most around 6 hours, optionally at most around 5 hours, optionally at most around 4 hours; and/or around 1 to 36 hours, optionally around 1 to 24 hours, optionally around 1 to 12 hours, optionally around 2 to 6 hours, optionally around 3 to 5 hours, optionally around 4 hours.

Said activated filter may be held within a container (e.g. a reticulated container such as a mesh bag). Said container may be permeable to the aqueous phase and substantially impermeable to the activated filter (e.g. granules thereof), optionally wherein said container comprises a polyolefin, optionally polyethylene or polypropylene (e.g. a polyolefin mesh bag).

The method may further comprise, after removing metallic impurities using the activated filter (optionally the activated carbon filter), regenerating the activated filter, optionally wherein said regenerating comprises:

(a) treating the activated filter with an aqueous base; optionally an alkali metal hydroxide or an alkaline earth metal hydroxide; optionally selected from sodium hydroxide, potassium hydroxide, or the like, or a combination thereof; preferably wherein said base is potassium hydroxide; and/or

(b) calcining the activated filter (e.g. at around 400 to 650°C, optionally around 450 to 630°C, optionally around 500 to 620°C, optionally around 550 to 610°C, optionally around 600°C).

Regenerating the activated filter allows it to be used again, thereby reducing waste.

The method may further comprise generating a precipitate (e.g. terephthalic acid (PTA)). Said precipitate may be generated after separation of the biphasic mixture.

The method may further comprise generating a precipitate (e.g. terephthalic acid (PTA)), optionally wherein said precipitate is generated after separation of the biphasic mixture, optionally wherein said precipitate is generated by decreasing the pH of the aqueous phase, optionally to pH around 6 to 8, optionally around 6.5 to 7.5, optionally around 7.

In some implementations the decreasing the pH of the aqueous phase is with hydrochloric acid, optionally wherein said hydrochloric acid is at a concentration of at least around 1 M, optionally at least around 2 M, optionally at least around 3 M; and/or at most around 10 M, optionally at most around 9 M, optionally at most around 8 M; and/or around 1 M to 10 M, optionally around 1 M to 8 M, optionally around 1 M to 6 M, optionally around 1 M to 4 M, optionally around 1 M to 3 M.

The method may further comprise filtration (optionally vacuum filtration) of said precipitate from the aqueous phase (optionally the separated aqueous phase), to generate a filtered aqueous phase and a residue.

In some implementations the residue is washed with an organic solvent, optionally a ketone solvent such as acetone (such as chilled acetone).

The method may further comprise distillation of the aqueous phase (optionally the separated aqueous phase and/or optionally the filtered aqueous phase) into one or more distillates, optionally wherein at least one of said distillates comprises a glycol, optionally an aliphatic glycol (optionally an aliphatic group), optionally an alkyl glycol, optionally ethylene glycol. Distillation of the aqueous phase has been found to be suitable for the purification of the aqueous phase. Advantageously, the method of the current disclosure allows for the recovery of the glycol reaction product, which reduces the organic waste produced by the method of the present disclosure.

EXAMPLES

Example 1: Depolymerisation of polyester garments

A general protocol for the depolymerisation of polyester-containing garments is set out below and illustrated in Fig. 1.

1 . Shred the Polyester garments to <10mm ²

2. Prepare the following hydrolysis mixture in a round bottom flask or reactor vessel; a. Pentan-1 -ol 70 wt% b. KOH 10 wt% c. Polyester 20 wt% wt% being the weight in the total weight of the hydrolysis mixture.

3. Stir and heat the mixture @80°C and reflux for up to 1 h or until solid phase is fully taken into solution.

4. Cool the hydrolysis mixture to room temperature.

5. Initial filter to remove solid contaminants using progressively graded filters (sieves 10 mm, 4 mm, 150 pm).

6. Once cool, add DI water at a volume identical to the volume of pentan-1 -ol used to dissolve the white salt phase.

7. Density separate the organic and aqueous layer. Recover the organic layer.

8. The potassium carboxylate salt is now in suspension in the aqueous layer (pH 11-12).

9. Acidify (pH 3-5) the aqueous layer with dilute HCI, to precipitate the salt.

10. Vacuum filtrate the precipitated salt and remaining aqueous layer to recover the precipitate.

HPLC (Fig. 2; Method - C18 Raptor 2.7um 100x2.1 mm Column at 0.4ml/min with 30% MeOH/70% H2O(0.1 % Formic Acid) at 240nm), TGA/DSC (Fig. 3), 1 H NMR (Fig. 4) and 13C NMR (Fig. 5) analyses were conducted.

Example 2

Optimisation studies (Taguchi Method) were conducted in accordance with the protocol outlined in Table 1 , below.

Four variables are controlled in the optimisation process using the Taguchi Method which were:

A. Loading %

Level 1 = 20%

Level 2 = 30%

B. Fibre Density (shred size, function of surface area)

Level 1 = 20 kg/m ³

Level 2 = 40 kg/m ³

C. Reaction Temperature

Level 1 = 70°C

Level 2 = 80°C

D. Mixing time in minutes

Level 1 = 10 minutes.

Level 2 = 20 minutes.

Signal

= -lO log(- x

Noise Larger the better n

Equation (1)

Table 1

Optimisation matrix

Mix Variables A B C D Signal/

Noise

1 1 1 1 1 31.1

2 2 1 1 1 34.2

3 1 2 1 1 31.2

4 1 1 2 1 47.6

5 1 1 1 2 40.1

6 2 2 1 1 36.4

7 1 1 2 2 41.2

8 2 2 2 2 40.2

Example 3: Purification of a terephthalic acid (PT A) product

The protocol of Example 1 was followed. The aqueous phase obtained in steps 7 and 8 was purified using an activated carbon filter to remove metallic impurities from the aqueous phase.

2 kg activated carbon (granules, 2 to 6 mm in diameter) in a polyester mesh bag was added to 20 L aqueous phase. The aqueous phase was then stirred for 4 hours, after which the bag was removed and the activated carbon regenerated (see Example 4 below).

Inductively coupled plasma optical emission spectroscopy (ICP-OES) is an analytical technique useful for detecting chemical elements in a sample. The technique is particularly useful for detecting metallic impurities and measuring their concentration.

Following this purification, the aqueous phase was acidified and filtered according to steps 9 and 10 in the protocol to obtain PTA product.

Example 4: Regeneration of an activated carbon filter

The activated carbon filter used in Example 3 was regenerated into a substantially pure form by calcination.

The activated carbon was removed from the mesh bag, treated with excess potassium hydroxide (aq) and calcined at 600°C to remove any metallic impurities. Following calcination, the activated carbon was dried so that it may be reused for the purification method of Example 3. The disclosure also comprises the following clauses, which may be claimed:

1 . A method for hydrolysis of a polyester, the method comprising: mixing the polyester with pentanol to form a hydrolysis mixture; and hydrolysing the polyester; wherein said hydrolysing the polyester is at a temperature up to around 100°C; in preferred implementations, the hydrolysis is basic hydrolysis.

2. The method of clause 1 , wherein said hydrolysis is basic hydrolysis and the hydrolysis mixture further comprises a base.

3. The method of clause 1 , wherein the hydrolysis mixture further comprises a base (basic hydrolysis) or an acid (acidic hydrolysis).

4. The method of clause 2 or 3, wherein the base is an alkali metal hydroxide or an alkali earth metal hydroxide; optionally selected from sodium hydroxide, potassium hydroxide, or the like, or a combination thereof; preferably wherein said base is potassium hydroxide.

5. The method of any one of clauses 2 to 4, wherein the base is provided at a wt% of: at least around 7.5%, optionally at least around 8%, optionally at least around 8.5%, optionally at least around 9%, optionally at least around 9.5%; and/or at most around 11 .5%, optionally at most around 11%, optionally at most around 10.5%; and/or around 7.5% to 11 .5%, optionally around 8% to 11%, optionally around 8.5% to 11%, optionally around 9.5% to 10.5%, preferably around 10%, the wt% being the weight of base in the total weight of the hydrolysis mixture.

6. The method of any one of clauses 2 to 4, wherein the base is provided at a wt% of: at least around 7.5%, optionally at least around 8%, optionally at least around 8.5%, optionally at least around 9%, optionally at least around 9.5%; and/or at most around 12%, optionally at most around 11 .5%, optionally at most around 11%, optionally at most around 10.5%; and/or around 7.5% to 12%, optionally around 7.5% to 11 .5%, optionally around 8% to 11%, optionally around 8.5% to 11%, optionally around 9.5% to 10.5%, preferably around 10%, the wt% being the weight of base in the total weight of the hydrolysis mixture.

7. The method of any one of clauses 2 to 6, wherein the pentanol and base are provided at a weight ratio of: at least around 15:3 pentanol to base, optionally at least around 17:3, optionally at least around 18:3, optionally at least around 19:3; and/or at most around 25:3 pentanol to base, optionally at most around 23:3, optionally at most around 22:3, optionally at most around 21 :3; and/or around 15:3 to 25:3 pentanol to base, optionally around 17:3 to 23:3, optionally around 18:3 to 22:3, optionally around 19:3 to 21 :3, optionally around 20:3; based on the weights of pentanol and base in the hydrolysis mixture. The method of clause 3, wherein the acid is hydrochloric or sulphuric acid. The method of clause 3 or 8, wherein the acid is provided at a wt% of: at least around 60%; and/or at most around 85%; and/or around 60% to 85%, the wt% being the weight of acid in the total weight of the hydrolysis mixture. The method of any preceding clause, wherein the pentanol is pentan-1 -ol. The method of any preceding clause (preferably including clause 2) wherein the pentanol is provided at a wt% of: at least around 60%, optionally at least around 62%, optionally at least around 64%, optionally at least around 66%, optionally at least around 68%; and/or at most around 80%, optionally at most around 78%, optionally at most around 76%, optionally at most around 74%, optionally at most around 72%; and/or around 60% to 80%, optionally around 62% to 78%, optionally around 64% to 76%, optionally around 66% to 74%, optionally around 68% to 72%, preferably around 70%, the wt% being the weight of pentanol in the total weight of the hydrolysis mixture. The method of any preceding clause (preferably including clause 2), wherein the polyester comprises aromatic dicarboxylic acid monomer units, optionally benzene dicarboxylic acid monomer units, optionally terephthalic acid monomer units. The method of any preceding clause (preferably including clause 2), wherein the polyester comprises aliphatic units, optionally alkylene, optionally straight chain alkylene, optionally Ci-Ce alkylene, optionally C2-C6 alkylene, optionally C2-C4 alkylene, optionally C2-C3 alkylene, optionally C2 alkylene/ethylene. The method of any preceding clause (preferably including clause 2), wherein the polyester is a copolymer, comprising units of clauses 14 and 15, optionally wherein the polyester is polyethylene terephthalic acid. The method of any preceding clause, wherein the polyester is provided at a wt% of: at least around 10%, and/or at most around 30%, and/or around 10% to 30%, optionally around 20% the wt% being based on the weight of polyester in the total weight of the hydrolysis mixture. The method of any preceding clause (preferably including clause 2) wherein said hydrolysing the polyester is at a temperature of at least around 50°C, optionally at least around 60°C, optionally at least around 65°C; and/or at most around 95°C, optionally at most around 90°C, optionally at most around 85°C, optionally at most around 80°C, optionally at most around 79°C, optionally at most around

75°C, optionally at most around 70°C; and/or around 50°C to 100°C, optionally around 60°C to 90°C, optionally around 60°C to 80°C; optionally around 60°C to 79°C, optionally around 65°C to 75°C. The method of any preceding clause, wherein said mixing is for: at least around 10 minutes, optionally at least around 20 minutes, optionally at least around 30 minutes, optionally at least around 45 minutes; and/or at most around 5 hours, optionally at most around 3 hours, optionally at most around

1 .5 hours; and/or around 10 minutes to 5 hours, optionally around 30 minutes to 3 hours, optionally around 45 minutes to 1 .5 hours, optionally around 1 hour. The method of any preceding clause, wherein the mixing is performed by use of a mechanical stirrer, optionally stirring at a speed of at least around 30 rpm; and/or at most around 600 rpm, and/or optionally around 30 rpm to 600 rpm. The method of any preceding clause, wherein said hydrolysing the polyester is at ambient or standard atmospheric pressure (around 100 kPa, e.g. around 101 kPa). The method of any preceding clause, wherein said mixing comprises agitation with a fluid (e.g. which is not substantially reactive with the hydrolysis mixture). The method of clause 20, wherein the fluid is or has been heated, optionally wherein the temperature is up to 100°C. The method of clause 20 or 21 , wherein the fluid is a gas (optionally air), optionally wherein the gas is delivered (e.g. at the bottom of a vessel containing the hydrolysis mixture) at a rate sufficient to increase the volume of the hydrolysis mixture by around 25% to 50%, optionally around 30% to 40%, optionally around 30 to 35%, optionally around 33%. The method of any one of clauses 20 to 22, wherein the gas is bubbled through the hydrolysis mixture (e.g. via one or more jets and/or propellers), optionally at a flow rate giving rise to an G value of around 1 to 6.5 min ¹ , optionally around 1 .75 to 5.75 min ¹ , optionally around 2.5 to 5 min- ¹ , optionally around 3 to 4.5 min ¹ , optionally around 3.75 min ¹ , wherein G is defined as: The method of any one of clauses 20 to 23, wherein the fluid is a diluting agent, optionally water or ethylene glycol, preferably water (e.g. the method further comprises diluting the hydrolysis mixture using a diluting agent). The method of clause 24, wherein the diluting agent is provided at a wt% of: at least around 5%, optionally at least around 10%, optionally at least around 15%, optionally at least around 20%, optionally at least around 25%, optionally at least around 30%; and/or at most around 65%, optionally at most around 60%, optionally at most around 55%, optionally at most around 50%, optionally at most around 45%, optionally at most around 40%; and/or around 5% to 65%, optionally around 10% to 60%, optionally around 15% to 55%, optionally around 20% to 50%, optionally around 25% to 45%, optionally around 30% to 40%; the wt% being the weight of diluting agent in the total weight of the hydrolysis mixture. The method of any preceding clause (preferably including clause 2), wherein the polyester is a component of a textile and/or a fabric and/or an article of clothing/garment. The method of clause 26, wherein said textile, fabric and/or article of clothing/garment further comprises cotton, polyethylene, polyvinyl chloride, polytetrafluoroethylene or other fluorinated coatings (e.g. Gortex), nylon, elastane, and/or a combination thereof. The method of clause 26 or 27, wherein said textile, fabric and/or article of clothing/garment further comprises one or more dyes (optionally a disperse dye), optionally selected from:

(a) coumarin dyes, optionally selected from Colour Index Disperse Yellow 82 (2a), 184 (2d), 186 (3), 232 (2d) and Colour Index Disperse Reds 277 (5a) and 374 (5b); and/or

(b) aminonaphthalimide dyes, optionally selected from Colour Index Disperse Yellow 11 (6a) and Orange 32 (9); and/or

(c) benzothioxanthone dyes, optionally selected from Colour Index Disperse Red 303; and/or

(d) heterocyclic dyes, optionally Colour Index Disperse Yellow 139 (17); and/or

(e) fluorescent dyes, optionally a dye meeting the standard EN 471 :1997. The method according any preceding clause, wherein the method further comprises recovery of one or more molecular components (optionally one or more dyes according to clause 28), optionally wherein said recovery is with a molecular sieve (e.g. a microporous molecular sieve), optionally a zeolite or organically modified silanes molecular sieve, e.g. including silicoaluminophosphate and/or sulfonated organic-functionalized silica. The method according to clause 29, wherein the molecular sieve has pores with a size up to around 15 angstroms, optionally up to around 12 angstroms, optionally up to around

10 angstroms. The method of any one of clauses 26 to 30, wherein the textile, fabric and/or article of clothing/garment further comprises a filler such as glass microspheres/bubbles, optionally wherein the glass is borosilicate such as soda lime borosilicate. The method according to clause 31 , wherein the method further comprises recovery of said filler (e.g. glass microspheres/bubbles), e.g. by filtration. The method of any one of clauses 26 to 32, wherein the textile, fabric and/or an article of clothing/garment comprises at least around 60 wt% polyester, based on the weight of the polyester in the total weight of the textile, fabric and/or article of clothing/garment. The method of any preceding clause (preferably including clause 2), further comprising size reduction of the polyester (e.g. of said textile, fabric and/or article of clothing/garment according to any one of clauses 26 to 33), optionally by cutting into smaller pieces before mixing to form the hydrolysis mixture, optionally wherein the pieces have a size of less than about 2.5 cm ² , optionally less than around 1 cm ² ; optionally around 0.25 to 0.75 cm ² ; optionally around 0.5 cm ² . The method of any preceding clause, further comprising, after hydrolysing the polyester, cooling the hydrolysis mixture to up to around 30°C, optionally up to around 25°C, optionally between around 20°C and around 25°C; to form a cooled mixture, optionally wherein the cooled mixture comprises solid material, optionally wherein the solid material is selected from polyethylene, polyvinyl chloride, polytetrafluoroethylene or other fluorinated coatings (e.g. Gortex), nylon, elastane, and/or a combination thereof. The method of clause 35, further comprising removing the solid material from the cooled mixture, (optionally by filtration, optionally with a paper filter), optionally wherein said solid material comprises an organic component, optionally wherein said organic component is polyethylene, polyvinyl chloride, polytetrafluoroethylene or other fluorinated coatings (e.g. Gortex), nylon, elastane, and/or a combination thereof as defined in clause 27. The method of clause 36, wherein filtration comprises one or more filtration steps, optionally wherein the filter is/are:

(i) a coarse filter; optionally having a pore size at most around 12 mm, optionally at most around 10 mm, optionally at most around 8 mm; and/or

(ii) a fine filter; optionally having a pore size at most around 6 mm, optionally at most around 4 mm, optionally at most around 2 mm; and/or

(iii) a fabric (e.g. cotton) filter; optionally having a pore size at most around 200 pm, optionally at most around 150 pm, optionally at most around 100 pm; and/or

(iv) a soil phase filter; optionally having a pore size at most around 30 pm, optionally at most around 20 pm, optionally at most around 10 pm; and/or

(v) an activated filter, optionally an activated carbon filter; optionally wherein filtration comprises more than one filtration steps, with filters having progressively smaller pore sizes and wherein the method comprises a plurality of progressive filtration steps (i) to (iv), optionally four filtration steps having corresponding filters (i), then (ii), then (iii) and then (iv), optionally further comprising filter (v). The method of any one of clauses 35 to 37, further comprising adding an aqueous solvent (e.g. water, such as deionised water) to the cooled mixture to form a biphasic mixture comprising an organic phase (comprising pentanol) and liquid aqueous phase, optionally wherein the method further comprises separation of the biphasic mixture into separated organic and liquid phases, optionally by density separation. The method of clause 38, wherein said biphasic mixture comprises pentanol at a wt% of: at least around 60%, optionally at least around 65%, optionally at least around 70%; and/or at most around 80%, optionally at most around 78%, optionally at most around 76%, optionally at most around 74%; and/or around 60% to 80%, optionally around 62% to 78%, optionally around 64% to 76%, optionally around 66% to 74%, optionally around 68% to 72%, preferably around 70%, the wt% being based on the weight of pentanol in the total weight of the biphasic mixture. The method of clause 38 or 39, further comprising recycling the separated organic phase (e.g. into another cycle of the method according to any preceding clause). The method of any preceding clause, further comprising removing metallic impurities (e.g. iron-, titanium- and/or zinc-containing impurities), optionally by filtering with an activated filter (such as an activated carbon filter), preferably wherein the activated filter is used to remove metallic impurities from an aqueous phase (e.g. according to clause 38) after separation of the biphasic mixture. The method of clause 41 , wherein said removing metallic impurities comprises filtering with an activated filter and wherein said activated filter is present as granules (e.g. granules of activated carbon), optionally wherein said granules are around 2 to 6 mm in diameter. The method of clause 42, wherein said removing metallic impurities comprises mixing (optionally stirring) the activated filter with the aqueous phase for: at least around 1 hour, optionally at least around 2 hours, optionally at least around 3 hours, optionally at least around 4 hours; and/or at most around 36 hours, optionally at most around 24 hours, optionally at most around 12 hours, optionally at most around 6 hours, optionally at most around 5 hours, optionally at most around 4 hours; and/or around 1 to 36 hours, optionally around 1 to 24 hours, optionally around 1 to 12 hours, optionally around 2 to 6 hours, optionally around 3 to 5 hours, optionally around 4 hours. The method of any one of clauses 41 to 43, wherein said removing metallic impurities comprises filtering with an activated filter held within a container (e.g. a reticulated container such as a mesh bag, e.g. wherein said container is permeable to the aqueous phase and substantially impermeable to the activated filter), optionally wherein said container comprises a polyolefin, optionally polyethylene or polypropylene (e.g. a polyolefin mesh bag). The method of any one of clauses 41 to 44, wherein said removing metallic impurities comprises filtering with an activated filter (optionally an activated carbon filter) and wherein the method further comprises, after removing metallic impurities, regenerating the activated filter, optionally wherein said regenerating comprises:

(a) treating the activated filter with an aqueous base; optionally an alkali metal hydroxide or an alkaline earth metal hydroxide; optionally selected from sodium hydroxide, potassium hydroxide, or the like, or a combination thereof; preferably wherein said base is potassium hydroxide; and/or

(b) calcining the activated filter (e.g. at around 400 to 650°C, optionally around 450 to 630°C, optionally around 500 to 620°C, optionally around 550 to 610°C, optionally around 600°C). The method of any one of clause 38 to 45, further comprising generating a precipitate (e.g. terephthalic acid (PT A)), optionally wherein said precipitate is generated after separation of the biphasic mixture. The method of clause 46 wherein the precipitate is generated by decreasing the pH of the aqueous phase, optionally to pH around 6 to 8, optionally around 6.5 to 7.5, optionally around 7. The method of clause 47, wherein decreasing the pH of the aqueous phase is with hydrochloric acid, optionally wherein said hydrochloric acid is at a concentration of: at least around 1 M, optionally at least around 2 M, optionally at least around 3 M; and/or at most around 10 M, optionally at most around 9 M, optionally at most around 8 M; and/or around 1 M to 10 M, optionally around 1 M to 8 M, optionally around 1 M to 6 M, optionally around 1 M to 4 M, optionally around 1 M to 3 M.

49. The method of any one of clauses 46 to 48, further comprising filtration (optionally vacuum filtration) of said precipitate from the aqueous phase (optionally the separated aqueous phase), to generate a filtered aqueous phase and a residue.

50. The method of clause 49, wherein the residue is washed with an organic solvent, optionally a ketone solvent such as acetone (such as chilled acetone).

51. The method of any one of clauses 38 to 50, further comprising distillation of the aqueous phase (optionally the separated aqueous phase and/or optionally the filtered aqueous phase) into one or more distillates, optionally wherein at least one of said distillates comprises a glycol, optionally an aliphatic glycol (optionally an aliphatic group according to clause 13 above), optionally an alkyl glycol, optionally ethylene glycol.

52. Use of pentanol in the hydrolysis of a polyester at a temperature up to 100°C.

53. The use according to clause 52, wherein the hydrolysis is basic or acidic hydrolysis (preferably basic).

54. The use according to clause 52 or 53, comprising the features of any one of clauses 1 to 51 (mutatis mutandis).

55. A method, use or system substantially as hereinbefore described with reference to the associated description and drawings.

Any listing or discussion of an apparently prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or common general knowledge. All references disclosed herein are to be considered to be incorporated herein by reference.

All features discussed herein in respect of any of the uses, methods or products relate to all other uses, methods or products mutatis mutandis.

Those skilled in the art will recognise or be able to ascertain using no more than routine experimentation many equivalents to the specific embodiments described herein. The scope of the present disclosure herein is not intended to be limited to the above description, but rather is as set forth in the appended claims. Those of ordinary skill in the art will appreciate that various changes and modifications to this description may be made without departing from the spirit or scope of the present disclosure.