Method for decomposing plastic products

Abstract

The present invention relates to a method for degrading a plastic product comprising at least one polymer, the method comprising subjecting the plastic product to a spinning process to obtain fibers of said plastic product and depolymerizing at least one polymer of said fibers.

Description

Technical Field

[0001] The present invention relates to a method for decomposing plastic products. The method of the present invention particularly includes a step of spinning a plastic product before depolymerizing at least one polymer of the spun plastic product. The method of the present invention is particularly useful for decomposing plastic products containing polyester and / or polyamide, preferably polyethylene terephthalate and / or polylactic acid. The present invention also relates to a method for producing monomers and / or oligomers from spun plastic products.

[0002] Background Plastics are inexpensive and durable materials that can be used to manufacture a variety of products for a wide range of applications (such as food packaging, textiles, etc.). As a result, the production of plastics has increased dramatically over the past few decades. Moreover, most of them are used for disposable applications, such as packaging, agricultural films, disposable consumer goods or short-lived products that are discarded within one year of manufacture. Due to the durability of the polymers contained, a significant amount of plastics is deposited in landfills and natural habitats around the world, increasing environmental problems. For example, in recent years, polyethylene terephthalate (PET), an aromatic polyester produced from terephthalic acid and ethylene glycol, has been widely used in the manufacture of several products for human consumption, such as food and beverage packaging (e.g., bottles, convenience-sized soft drinks, pouches for nutritional products) or textiles, fabrics, rugs, carpets, etc.

[0003] To reduce the environmental and economic impacts associated with the accumulation of plastic waste, from plastic decomposition to plastic recycling, various solutions have been studied, including recycling technologies and energy production from such plastics. Mechanical recycling technology is still the most used technology, but it faces several drawbacks. In fact, mechanical recycling technology requires extensive and costly sorting, which leads to a downgrading of the applications due to the loss of molecular weight during processing and the uncontrolled presence of additives in the recycled product. As actual recycling technologies are also expensive, recycled plastic products are generally not competitive compared to virgin plastics.

[0004] In recent years, innovative methods for the enzymatic recycling of plastic products have been developed and described (for example, WO 2014 / 079844, 2015 / 097104, 2015 / 173265 and 2017 / 198786). In contrast to traditional recycling technologies, such enzymatic depolymerization methods make it possible to recover the chemical components of the polymer (i.e., monomers and / or oligomers). The resulting monomers / oligomers can be recovered and used to remanufacture plastic items, and as a result, such methods lead to the infinite recycling of plastics. These methods are particularly useful for recovering terephthalic acid and ethylene glycol from plastic products containing PET.

[0005] However, there is always a need for methods with improved degradation rates.

[0006] Summary of the Invention By working on improving the method for decomposing plastic products, the inventors have shown that the decomposition process can be improved by increasing the contact area between the plastic product and the decomposing agent. Thus, the inventors have developed a method of increasing the surface area of the plastic by converting the plastic product into fibers before subjecting the fibers to the decomposition process. In particular, the inventors propose spinning the plastic product before subjecting the spun plastic product (i.e., the fiber) to depolymerization. The method of the present invention is particularly useful for decomposing plastic products containing polyethylene terephthalate.

[0007] In this regard, an object of the present invention is a method for decomposing a plastic product containing at least one polymer, comprising: subjecting the plastic product to a spinning process to obtain fibers of the plastic product; and depolymerizing at least one polymer of the fibers. Preferably, the spinning process is carried out on a plastic product in a partially or fully molten state, and is a melt spinning process carried out at a temperature above the crystallization temperature (Tc) of at least one polymer of the plastic product, preferably above the melting temperature (Tm) of the polymer.

[0008] Advantageously, the cooling of the obtained fibers is carried out at a temperature below the crystallization temperature (Tc) of at least one target polymer of the plastic product, preferably below the glass transition temperature (Tg) of the polymer.

[0009] In an embodiment, this method is carried out on plastic bottles, plastic trays, plastic bags and plastic packaging, rigid or flexible plastic waste including soft and / or hard plastics and / or crystalline plastic fibers, in particular plastic fibers containing thermoplastic polymers.

[0010] Also, an object of the present invention is a method for decomposing a plastic product containing PET, comprising: a. A step of subjecting the plastic product to melt spinning at a temperature exceeding 170°C, preferably 230°C or higher, to obtain fibers from the plastic product, and cooling the obtained fibers at a temperature below 100°C, preferably below 90°C; b. A step of depolymerizing preferably PET in the fiber by contacting the fiber with a depolymerase, such as cutinase; and optionally, c. A method is also provided that includes a step of recovering and optionally purifying the oligomers and / or monomers generated by the depolymerization of the PET.

[0011] The object of the present invention is also to provide a method for producing monomers and / or oligomers and / or degradation products from a plastic product containing at least one polymer, preferably PET, which includes continuously subjecting the plastic product to a spinning process and preferably a depolymerization process including exposing the plastic product to a depolymerase, preferably cutinase.

[0012] Detailed Description of the Invention Definitions The present disclosure will be best understood by reference to the following definitions.

[0013] In the context of the present invention, the terms "plastic article" or "plastic product" are used interchangeably and refer to any item or product including at least one polymer, such as plastic sheets, trays, tubes, rods, profiles, shapes, bulk blocks, fibers, etc. Preferably, the plastic article is a manufactured product, such as rigid or flexible packaging (bottles, trays, cups, etc.), agricultural films, bags and sacks, disposable items, etc., carpet scraps, fabrics, textiles, etc. More preferably, the plastic article refers to plastic or textile waste. Preferably, the plastic article includes a mixture of semi-crystalline and / or amorphous polymers. The plastic article may further contain additional substances or additives, such as plasticizers, minerals, organic fillers, dyes, etc.

[0014] "Polymer" refers to a compound or mixture of compounds whose structure is composed of a plurality of repeating units (i.e., "monomers") linked by covalent chemical bonds. In the context of the present invention, the term "polymer" refers to such a chemical used in the composition of plastic products. As an example, synthetic polymers include polymers obtained from petroleum, such as polyolefins, aliphatic or aromatic polyesters, polyamides, polyurethanes, and polyvinyl chloride. In the context of the present invention, a polymer refers to a thermoplastic polymer, i.e., a polymer that can be molded above a specific temperature and solidifies when cooled.

[0015] Regarding a polymer or a plastic article containing a polymer, the term "depolymerization" refers to a process in which at least one polymer of the polymer or the plastic article is depolymerized and / or decomposed into smaller molecules, such as monomers and / or oligomers and / or any decomposition products.

[0016] According to the present invention, "oligomer" refers to a molecule containing 2 to about 20 monomer units. As an example, oligomers recovered from PET include methyl-2-hydroxyethyl terephthalate (MHET) and / or bis(2-hydroxyethyl) terephthalate (BHET) and / or 1-(2-hydroxyethyl) 4-methyl terephthalate (HEMT) and / or dimethyl terephthalate (DMT). As another example, oligomers of lactic acid can be recovered from PLA.

[0017] In the context of the present invention, the term "polyester" refers to a polymer containing ester functional groups in its main chain. The ester functional group is characterized by a carbon: carbon single bond, a double bond to oxygen, and a single bond to oxygen, bonded to three other atoms. The single-bonded oxygen is bonded to another carbon. Depending on the composition of its main chain, the polyester can be aliphatic, aromatic or semi-aromatic. The polyester can be a homopolymer or a copolymer. By way of example, polyethylene terephthalate is a semi-aromatic copolymer composed of two monomers: terephthalic acid and ethylene glycol.

[0018] In the context of the present invention, the term "crystalline polymer" or "semi-crystalline polymer" refers to a semi-crystalline polymer in which crystalline regions and amorphous regions coexist. The degree of crystallinity of a semi-crystalline polymer can be estimated by various analytical methods and is typically in the range of 10 to 90%. For example, differential scanning calorimetry (DSC) or X-ray diffraction can be used to determine the degree of crystallinity of a polymer. Other techniques, such as X-ray scattering (XS) (including small-angle and wide-angle XS) and infrared spectroscopy, are also suitable for estimating the less reliable degree of crystallinity of a polymer. In the present disclosure, the degree of crystallinity was measured by DSC. In particular, the DSC measurement was performed as follows. A small amount of sample (a few mg) is heated from ambient temperature or a temperature below ambient temperature to a high temperature above the melting temperature (Tm) of the polyester at a constant heating rate. Heat flow data is collected and plotted against temperature. The degree of crystallinity Xc (%) is given by:

Equation

[0019] where ΔH f is the enthalpy of melting that can be determined by integrating the endothermic melting peak, ΔH cc is the enthalpy of cold crystallization, which is determined by integrating the exothermic cold crystallization peak, w t is the weight fraction of polyester in the plastic, and ΔH f,100%is the enthalpy of fusion for a fully crystalline polymer and can be found in the literature. As an example, the ΔH of PET f,100% is obtained as 125.5 J / g from the literature (Polymer Data Handbook, Second Edition, Edited by James E. Mark, OXFORD, 2009). According to the literature, the ΔH of PLA f,100% is equal to 93 J / g (Fisher E. W., Sterzel H. J., Wegner G., Investigation of structure of solution grown crystals of lactide copolymers by means of chemical reactions, Kolloid Zeitschrift & Zeitschrift fur Polymere,1973, 251, p 980-990).

[0020] The error margin of crystallinity is about 10%. Therefore, a crystallinity of about 25% corresponds to a crystallinity of 22.5% - 27.5%.

[0021] In the context of the present invention, "Tg", "Tc" and "Tm" refer to the glass transition temperature, crystallization temperature and melting temperature of the polymer, respectively. Such temperatures can be estimated by various analytical methods. For example, differential scanning calorimetry (DSC) or differential thermal analysis (DTA) can be used to determine the Tg, Tc and Tm of the polymer. In the present disclosure, the Tg, Tc and Tm of the disclosed polymers correspond to the temperatures measured by DSC.

[0022] Spinning process The inventors have shown that by converting plastic products into fibers before subjecting the polymers to depolymerization, it is possible to improve the depolymerization rate of the polymers contained in plastic products, in particular polyesters and / or polyamides and / or polyolefins. Conversion of the plastic products into fibers (solid and / or hollow fibers including filaments and / or nonwovens) allows increasing the contact surface (i.e., the contact area) between the plastic product (and thus the polymer) and the depolymerizing agent. That is, by increasing the contact surface between the plastic product and the depolymerizing agent, it is possible to improve the depolymerization rate and / or reduce the amount of depolymerizing agent and / or shorten the time required to decompose the plastic product as compared to the same non-spun plastic product.

[0023] As used herein, "spinning" refers to a shaping process for manufacturing polymer fibers. There are many types of spinning, including wet spinning, dry spinning (by solvent dissolution), dry-jet wet spinning, melt spinning, gel spinning, and electrospinning. The spinning process requires a spinneret.

[0024] As used herein, the term "spinneret" refers to a specific type of die mainly used in fiber manufacturing. It is usually a small metal plate with fine holes through which a spinning solution (a viscous or syrupy polymer stream prepared by melting or chemically dissolving the raw material) is loaded and / or pulled, for example, by pump transport, to form fibers. They emerge from the spinneret as long fibers and then solidify by coagulation, evaporation, or cooling. The cross-sectional shape of the fiber is determined by the size and shape of the spinneret holes. The holes of the spinneret can be of various shapes: circular, flat, trilobal, Y-shaped, octahedral, etc. Depending on the type of spinneret used, either solid or hollow fibers can be formed. As an example, nonwovens or filaments can be formed.

[0025] The present invention relates in particular to a method for decomposing plastic products containing at least one thermoplastic polymer.

[0026] In certain embodiments, the spinning process is a melt spinning process performed on plastics that are partially or fully in a molten state. "Melt spinning" is classically used for polymers that can be melted (thermoplastic polymers such as polyamides, polyesters and / or polyolefins). Generally, a molten plastic product is extruded through the orifice of a spinneret, and the resulting molten fibers solidify and harden when cooled by the surrounding flow of a cooling fluid, such as relatively cold air or other inert gas. In certain embodiments, the plastic product is heated in an extruder to a partially or fully molten state.

[0027] In certain embodiments, the molten plastic is extruded through a spinneret at a temperature above the crystallization temperature (Tc) of the target polymer of the plastic product (i.e., the polymer intended to be degraded or depolymerized) to form fibers. Preferably, the plastic product is subjected to a temperature above the melting temperature (Tm) of the target polymer of the plastic product. Even more preferably, the plastic product is subjected to a temperature of Tm + 5°C to Tm + 25°C, preferably Tm + 10°C to Tm + 25°C, more preferably Tm + 15°C to Tm + 25°C, for example, Tm + 20°C of the target polymer. In another embodiment, the plastic product is subjected to a temperature of Tm + 25°C to Tm + 50°C of the target polymer. In another embodiment, the plastic product is subjected to a temperature corresponding to Tm + 50°C or higher of the target polymer.

[0028] According to embodiments of the present invention, the plastic product contains several types of polymers. In particular, the plastic product contains at least 51% by weight of the target polymer. In such a case, the plastic product is advantageously subjected to a temperature above Tc or above Tm of the target polymer. Alternatively, the plastic product is subjected to a temperature above the highest Tc or Tm of the polymers contained in the plastic product.

[0029] In certain embodiments, the plastic product contains PET, and the melt spinning process includes subjecting the plastic product to a temperature above 170°C, preferably 230°C or higher, more preferably 250°C to 300°C. Even more preferably, the plastic product containing PET is subjected to a temperature of 260°C to 280°C. In another embodiment, the plastic product containing PET is subjected to a temperature of 300°C or higher, preferably 300°C to 320°C.

[0030] In another specific embodiment, the plastic product contains PLA, and the melt spinning process includes subjecting the plastic product to a temperature above 110°C, more preferably 145°C or higher. In certain embodiments, the plastic product contains PLLA, and the melt spinning process includes subjecting the plastic product to a temperature of 170°C or higher. In another embodiment, the plastic product contains stereocomplex PLA, and the melt spinning process includes subjecting the plastic product to a temperature of 230°C or higher.

[0031] According to the present invention, the melt spinning process is preferably carried out using an extruder and a spinneret. Advantageously, the extruder is selected from a single - screw extruder, a multi - screw extruder of either co - rotating or counter - rotating design, a planetary roller extruder, a dispersion kneader, a reciprocating single - screw extruder (co - kneader), a mini - extruder or a co - extruder. Preferably, the melt spinning process further includes the use of a melt pump, a filter and a distribution system. In certain embodiments, the molten or partially molten plastic product is filtered before the spinning process.

[0032] Advantageously, the spinneret is selected from a spinneret for non - woven products or filaments. In certain embodiments, the melt spinning process is carried out using a spunbond spinneret or a melt - blown spinneret to produce spunbond or melt - blown non - woven fibers.

[0033] In certain embodiments, the spun plastic product is formed into non - woven fibers having a porosity of more than 30%, preferably more than 40%. In the context of the present invention, the porosity of the non - woven fibers is determined by the following equation:

Number

[0034] In another specific embodiment, the melt spinning process is carried out in an extruder equipped with a spinneret for filaments. In particular, such filaments are selected from monofilaments or multifilaments. In a preferred embodiment, filaments with a diameter of less than 800 μm are produced by the spinneret.

[0035] In a specific embodiment, melt spinning is carried out by a co-extruder. The use of a co-extruder can be useful for producing bicomponent fibers, i.e., fibers produced by spinning two types of plastic products.

[0036] Cooling process According to an embodiment, the fibers (i.e., the spun plastic products) are cooled as they exit the spinneret. In fact, as represented above, melt spinning is advantageously carried out for at least partially molten plastic extruded through the spinneret. The resulting fibers are then subjected to a temperature low enough to solidify the fibers. Classically, the cooling of the fibers can be carried out with cooling air and cooling liquid, preferably any cooling fluid including cooling air.

[0037] In a specific embodiment, the fibers are cooled in less than 30 seconds, more preferably less than 20 seconds, even more preferably less than 10 seconds after exiting the spinneret. Preferably, the fibers are cooled immediately after exiting the spinneret (e.g., for filament production). For meltblown production, the resulting fibers are passed through a high-speed hot air stream and then collected on a rotating drum or forming belt at ambient temperature to cool the fibers and produce a nonwoven web.

[0038] Advantageously, cooling is effected by subjecting the fiber to a temperature below the Tc of the target polymer, preferably below the glass transition temperature (Tg) of said polymer.

[0039] Such rapid cooling after the heating step enables at least one polymer in the fiber to be amorphized. Amorphization occurs during heating of the plastic product and enables the heated polymer to be fixed in an amorphous state by rapid cooling at a temperature below Tc and / or Tg. By amorphization, advantageously, the depolymerization ability of said polymer is improved.

[0040] In certain embodiments, the target polymer of the plastic product is amorphized during the melt spinning process by heating the plastic product to a temperature above the Tc of the polymer, preferably above the Tm, when forming the fiber and rapidly cooling the resulting fiber at a temperature below the Tc and / or Tg of said polymer.

[0041] As used herein, the terms “amorphization” and “amorphizing” in relation to a polymer refer to a decrease in the crystallinity of a given polymer as compared to its crystallinity prior to amorphization. Preferably, amorphization enables the crystallinity of the target polymer to be decreased by at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, 70%, 80% or 90% as compared to prior to amorphization. Advantageously, amorphization results in a polymer having a crystallinity of at most 30%, preferably at most 25%, more preferably at most 20%, even more preferably at most 15%. Alternatively, amorphization enables the crystallinity of the polymer to be maintained below 30%, preferably below 25%, more preferably below 20%, even more preferably below 15%. Thereby, amorphization improves the depolymerization ability of said polymer by a biological agent.

[0042] The heating and cooling temperatures can be adapted by those skilled in the art according to the target polymer. Generally, the plastic product can be subjected to heat treatment and optionally shear stress for a period sufficient to obtain the amorphization of the target polymer. For example, such a period may be included in the range of 1 second to several minutes depending on the temperature and / or the plastic product. In a preferred embodiment, the melt spinning process is carried out on a plastic product that is subjected to both shear stress and a temperature above the Tc of the target polymer of the plastic product, preferably above the Tm of said polymer. Subjecting to heating and shear stress is preferably carried out simultaneously to improve the amorphization.

[0043] In a particular embodiment, cooling is carried out by subjecting the fiber to a temperature below the Tc of the target polymer of the plastic product, preferably below the Tg of said polymer. Subjecting to a temperature below the Tc of the target polymer of the plastic product is particularly suitable for, for example, PBAT or any polymer with a Tg below 20°C. In another embodiment, cooling is carried out by subjecting the fiber to a temperature at least 20°C lower than the Tc of the target polymer, preferably at least 30°C, 40°C, 50°C lower. In an embodiment, cooling is carried out by subjecting the fiber to room temperature (i.e., 25°C ± 5°C). In another embodiment, cooling is carried out by subjecting the fiber to a temperature of about 20°C or about 10°C.

[0044] Advantageously, cooling can be carried out by subjecting the fiber to the ambient air. For example, the fiber is subjected to ambient air with a temperature of 15°C to 30°C, preferably 20°C to 25°C. Alternatively, the fiber is subjected to cooling air with a temperature below 14°C, preferably below 10°C or below 5°C. In particular, this method implements an air cooler. Alternatively, the fiber is subjected to air with a temperature below the Tc of the target polymer. More generally, any method suitable for rapidly reducing the temperature of the fiber (e.g., cooling liquid) can be used. Alternatively, cooling can be carried out immediately after shaping by immersing the fiber in a liquid at the cooling temperature.

[0045] Generally, the fiber is subjected to a cooling temperature for a period sufficient to lower its temperature. For example, such a period may be included in less than 1 second to several minutes, depending on the throughput, the temperature of the fiber discharged from the spinneret, and / or the cooling temperature and / or diameter of the fiber. In particular, the fiber is subjected to the cooling temperature for less than 1 minute, preferably less than 30 seconds, more preferably less than 20 seconds, even more preferably less than 10 seconds, less than 7 seconds, less than 5 seconds, and about 1 second. The cooling period and the air flow rate will be readily adaptable by those skilled in the art to obtain solid filaments and / or nonwoven fabrics.

[0046] Accordingly, an object of the present invention is a method for decomposing a plastic product containing at least one polymer, a. a step of subjecting the plastic product to melt spinning for forming a fiber by heating the plastic product at a temperature above the crystallization temperature (Tc) of the target polymer of the plastic product, preferably above the melting temperature (Tm) of the target polymer, and cooling the obtained fiber at a temperature lower than Tc of the target polymer, preferably lower than the Tg of the polymer; b. a step of depolymerizing at least the target polymer.

[0047] Advantageously, the melt spinning is carried out by operating an extruder and a spinneret, and the obtained fiber is subjected to ambient air and / or cooling air.

[0048] In a specific embodiment, the plastic product contains PET, and the melt spinning step is carried out by operating the extruder at a temperature above 170°C, preferably above 230°C, where the cooling of the obtained fiber is carried out at a temperature lower than 100°C, preferably lower than 90°C. Alternatively, the cooling of the fiber is carried out by subjecting the fiber to a temperature lower than 50°C.

[0049] In certain embodiments, after the melt spinning step, the target polymer in the fiber is at least partially amorphous and, after cooling, exhibits a crystallinity of at most 30%, preferably at most 25%, more preferably at most 20%. In particular, the polymer is PET and the PET in the fiber exhibits a crystallinity of at most 30%, preferably at most 25%, more preferably at most 20%.

[0050] In particular, an object of the present invention is a method for decomposing a plastic product containing at least PET, a. subjecting the plastic product to melt spinning at a temperature above 170°C, preferably above 185°C, more preferably above 200°C, even more preferably 230°C or higher, and cooling the resulting fibers at a temperature below 100°C, preferably below 90°C; b. depolymerizing the PET in the fibers.

[0051] Advantageously, the melt spinning step is carried out at a temperature above 240°C, 245°C, 250°C, 255°C, 260°C, 265°C and the cooling is carried out in less than 30 seconds, preferably immediately, after melt spinning.

[0052] Preferably, the depolymerization step is carried out using an esterase, more preferably cutinase.

[0053] In certain embodiments, the plastic product is foamed before being formed into fibers. For example, the plastic product is foamed in an extruder before being extruded through a spinneret. The foaming is preferably carried out with a physical blowing agent selected from gases, more preferably selected from the group consisting of nitrogen, carbon dioxide, methane, helium, neon, argon, xenon, hydrogen or mixtures thereof and / or preferably with a chemical blowing agent selected from the group consisting of citric acid, carbonates or mixtures thereof.

[0054] Accordingly, another object of the present invention is a method for decomposing a plastic product containing at least one polymer, a. A step of foaming the plastic product and melt-spinning it to form foamed fibers by using an extruder equipped with a spinneret, wherein the extrusion is carried out at a temperature above the crystallization temperature (Tc) of the target polymer of the plastic product, preferably above the melting temperature (Tm) of the polymer, and the cooling of the foamed fibers is carried out at a temperature below Tc of the target polymer, preferably below the glass transition temperature (Tg) of the polymer; b. providing a method including a step of depolymerizing the target polymer of the fiber.

[0055] Advantageously, the foaming is carried out by subjecting the plastic product to a chemical blowing agent and / or the fibers are cooled by subjecting them to ambient air and / or cooling air immediately after melt-spinning.

[0056] Depolymerization step According to the present invention, the decomposition method includes a step of depolymerizing at least one polymer of the spun plastic product (i.e., fiber). According to a preferred embodiment, the depolymerization step targets at least one polymer that has been pre-amorphized.

[0057] In a specific embodiment, the spun plastic product is cut into smaller pieces before the depolymerization step.

[0058] In a specific embodiment, the depolymerization step includes contacting the spun plastic product with a depolymerizing agent, i.e., a chemical and / or biological agent. In a specific embodiment, the depolymerization step is carried out in a liquid medium containing the depolymerizing agent.

[0059] In another specific embodiment, the plastic product is brought into contact with a depolymerizing agent before the depolymerization step. For example, after the fiber is subjected to the foaming step and / or the cooling step, it is immersed in a liquid containing a depolymerizing agent. In particular, the fiber can be brought into contact with the depolymerizing agent during the cooling step (for example, the fiber is immersed in a cooling liquid containing a depolymerizing agent and / or the depolymerizing agent is sprayed onto the fiber during cooling by cold air and / or ambient air). Alternatively, the fiber can be brought into contact with the depolymerizing agent by immersing the cooled fiber in a liquid containing a depolymerizing agent after the cooling step by air. If necessary, the fiber can be dried before the depolymerization step. The depolymerization step can preferably be carried out after immersing the fiber in a liquid from which the depolymerizing agent has been removed. Alternatively, the depolymerization step is carried out later by subjecting the spun plastic product to composting conditions. In particular, the spun plastic product is subjected to industrial composting conditions at a temperature above 50 °C and / or to home composting conditions at a temperature of 15 °C to 35 °C. Alternatively, the depolymerization step is carried out later by subjecting the spun plastic product to a stimulus capable of activating the depolymerizing agent. For example, the depolymerizing agent is a degrading enzyme and the stimulus consists of a specific temperature and / or humidity.

[0060] Accordingly, an object of the present invention is a method for decomposing a plastic product containing at least one polymer, a. a step of melt-spinning the plastic product to produce fibers of the plastic, the melt-spinning step being carried out at a temperature above the crystallization temperature (Tc) of the target polymer of the plastic product, preferably above the melting temperature (Tm) of the polymer, and cooling the spun plastic product by bringing the fibers into contact with air at a temperature below Tc of the target polymer, preferably below the glass transition temperature (Tg) of the polymer; b. a step of bringing the cooled fibers into contact with a liquid containing a depolymerizing agent; c. a step of at least partially depolymerizing the target polymer by bringing the fibers into contact with a liquid from which the depolymerizing agent has been removed, preferably.

[0061] In certain embodiments, the depolymerizing agent is a biological agent or comprises a biological agent. In particular, the biological agent is a depolymerase (i.e., an enzyme). Preferably, the depolymerase is capable of degrading at least one polymer of the plastic product, preferably at least the polymer that has been pre-amorphized.

[0062] The depolymerase is more preferably selected from the group consisting of cutinase, lipase, protease, carboxylesterase, p-nitrobenzyl esterase, esterase, scl-PHA depolymerase, mcl-PHA depolymerase, PHB depolymerase, amidase, aryl acylamidase (EC 3.5.1.13), oligomer hydrolase, such as 6-aminohexanoate cyclic dimer hydrolase (EC 3.5.2.12), 6-aminohexanoate dimer hydrolase (EC 3.5.1.46), 6-aminohexanoate oligomer hydrolase (EC 3.5.1.B17), oxidase, peroxidase, laccase (EC 1.10.3.2), oxygenase, lipoxygenase, monooxygenase or lignin-degrading enzyme. In certain embodiments, the plastic product is contacted with at least two types of depolymerase.

[0063] In certain embodiments, the plastic product comprises PET and the depolymerase is an esterase. In particular, the depolymerase is a cutinase produced by a microorganism selected from cutinase, preferably Thermobifida cellulosityca, Thermobifida halotolerans, Thermobifida fusca, Thermobifida alba, Bacillus subtilis, Fusarium solani pisi, Humicola insolens, Sirococcus conigenus, Pseudomonas mendocina, and Thielavia terrestris or any functional variant thereof. In another embodiment, the cutinase is selected from a metagenomic library, for example, the LC-cutinase described in Sulaiman et al., 2012, or the esterase described in EP 3517608, or any functional variant thereof including the depolymerases listed in WO 2018 / 011284 or WO 2018 / 011281. In another particular embodiment, the depolymerase is preferably a lipase produced by Ideonella sakaiensis. In another particular embodiment, the depolymerase is a cutinase produced by Humicola insolens, for example, the one called A0A075B5G4 in Uniprot or any functional variant thereof. In another embodiment, the depolymerase is selected from commercially available enzymes, for example, Novozym 51032 or any functional variant thereof.

[0064] In certain embodiments, the plastic product contains PLLA, and the depolymerase is preferably a protease produced by a microorganism selected from Amycolatopsis sp, Amycolatopsis orientalis, Tritirachium album (proteinase K), Actinomadura keratinilytica, Laceyella sacchari LP175, Thermus sp or any commercially available enzyme known to degrade PLA, for example, Savinase®, Esperase®, Everlase® or any functional variant thereof including the depolymerases listed in WO 2016 / 062695, 2018 / 109183 or 2019 / 122308.

[0065] In another particular embodiment, the plastic product contains PDLA, and the depolymerase is an esterase, preferably cutinase or lipase, more preferably CLE from Cryptococcus sp., lipase PS from Burkholderia cepacia, Paenibacillus amylolyticus TB-13, Candida Antarctica, Rhiromucor miehei, Saccharomonospora viridis, Cryptococcus magnus or any functional variant thereof.

[0066] In another particular embodiment, the plastic product contains PA, and the depolymerase is selected from the group consisting of amidase, aryl acylamidase (EC 3.5.1.13), oligomer hydrolase, for example, 6-aminohexanoate cyclic dimer hydrolase (EC 3.5.2.12), 6-aminohexanoate dimer hydrolase (EC 3.5.1.46), 6-aminohexanoate oligomer hydrolase (EC 3.5.1.B17).

[0067] In another specific embodiment, the plastic product comprises a polyolefin, and the depolymerase is preferably an oxidase selected from the group consisting of laccase, peroxidase, oxygenase, lipoxygenase, monooxygenase or lignin-degrading enzyme.

[0068] In another embodiment, the depolymerizing agent is a microorganism that expresses and secretes a depolymerase. The microorganism may naturally synthesize the depolymerase or may be a recombinant microorganism into which a recombinant nucleotide sequence encoding the depolymerase is inserted, for example, using a vector. Specific embodiments of the depolymerization process can be found in WO 2017 / 198786.

[0069] According to the present invention, different polymers contained in the same plastic article or different plastic articles simultaneously subjected to the decomposition method of the present invention can be depolymerized by using several microorganisms and / or purified enzymes and / or synthetic enzymes together or sequentially.

[0070] The time required for the depolymerization of at least one polymer of the plastic article may vary depending on the plastic article and the target polymer (for example, the nature and origin of the plastic article, its composition, shape, molecular weight, etc.), the type and amount of the microorganism / enzyme used, and various process parameters (i.e., temperature, pH, additional agents, etc.). A person skilled in the art can easily adapt the process parameters to the plastic article and / or the depolymerase.

[0071] In certain embodiments, the plastic product comprises PET, and the depolymerization step is carried out by contacting the plastic product with a biological depolymerizing agent at a temperature included in the range of 20°C to 90°C, preferably 30°C to 80°C, more preferably 40°C to 75°C, more preferably 50°C to 75°C, even more preferably 60°C to 75°C. Further, the depolymerization step is preferably carried out at a pH of 5 to 11, preferably 7 to 9, more preferably 7 to 8.5, even more preferably 7 to 8. Alternatively, the depolymerization step can be carried out under industrial and / or composting conditions.

[0072] In certain embodiments, the plastic product comprises PLA, and the depolymerization step is carried out by contacting the plastic product with a biological depolymerizing agent at a temperature included in the range of 20°C to 90°C, preferably 20°C to 60°C, more preferably 30°C to 55°C, more preferably 40°C to 50°C, even more preferably 45°C. Further, the depolymerization step is preferably carried out at a pH of 5 to 11, preferably 7 to 10, more preferably 8.5 to 9.5, even more preferably 8 to 9. In another particular embodiment, the depolymerization step can be carried out at a pH of 7 to 8. Alternatively, the depolymerization step can be carried out under industrial and / or composting conditions.

[0073] In another specific embodiment, the depolymerizing agent is a chemical agent or contains a chemical agent. In particular, the chemical agent is a catalyst selected from metal catalysts or a stable and non-toxic hydrosilane (PMHS, TMDS), for example, commercially available B(C6F5)3 and [Ph3C+, B(C6F5)4-] catalysts. In particular, the catalyst is selected from alkoxides, carbonates, acetates, hydroxides, alkali metal oxides, alkaline earth metals, calcium oxide, calcium hydroxide, calcium carbonate, sodium carbonate, iron oxide, zinc acetate, zeolites. In some embodiments, the catalyst used in the depolymerization process of the present invention comprises at least one of germanium compounds, titanium compounds, antimony compounds, zinc compounds, cadmium compounds, manganese compounds, magnesium compounds, cobalt compounds, silicon compounds, tin compounds, lead compounds, and aluminum compounds.In particular, the catalyst contains at least one of germanium dioxide, cobalt acetate, titanium tetrachloride, titanium phosphate, titanium tetrabutoxide, titanium tetraisopropoxide, titanium tetra-n-propoxide, titanium tetraethoxide, titanium tetramethoxide, tetrakis(acetylacetonato)titanium complex, tetrakis(2,4-hexanedionato)titanium complex, tetrakis(3,5-heptanedionato)titanium complex, dimethoxybis(acetylacetonato)titanium complex, diethoxybis(acetylacetonato)titanium complex, diisopropoxybis(acetylacetonato)titanium complex, di-n-propoxybis(acetylacetonato)titanium complex, dibutoxybis(acetylacetonato)titanium complex, titanium dihydroxybisglycolate, titanium dihydroxybisglycolate, titanium dihydroxybislactate, titanium dihydroxybis(2-hydroxypropionate), titanium lactate, titanium octanedioate, titanium dimethoxybistriethanolamineate, titanium diethoxybistriethanolamineate, titanium dibutoxybistriethanolamineate, hexamethyldititanate, hexaethyldititanate, hexapropyldititanate, hexabutyldititanate, hexaphenyldititanate, octamethytrititanate, octaethyltrititanate, octapropytrititanate, octabutyltrititanate, octaphenyltrititanate, hexaalkoxydititanate, zinc acetate, manganese acetate, methyl silicate, zinc chloride, lead acetate, sodium carbonate, sodium bicarbonate, acetic acid, sodium sulfate, potassium sulfate, zeolite, lithium chloride, magnesium chloride, ferric chloride, zinc oxide, magnesium oxide, calcium oxide, barium oxide, antimony trioxide and antimony triacetate. Alternatively, the catalyst is selected from nanoparticles. The chemical agent can be selected from any catalyst known to those skilled in the art having the ability to decompose and / or depolymerize the target polymer.

[0074] Alternatively, the chemical agent is an acid catalyst or a base catalyst capable of breaking polymer bonds, particularly ester bonds. In particular, the chemical agent involved in breaking ester bonds is a mixture of a hydroxide and an alcohol capable of dissolving the hydroxide. The hydroxide is selected from alkali metal hydroxides, alkaline earth metal hydroxides, and ammonium hydroxide, preferably selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide, magnesium hydroxide, ammonium hydroxide, tetra-alkylammonium hydroxide, and the alcohol is selected from straight-chain, branched-chain, cyclic alcohols, or combinations thereof, preferably a straight-chain C1-C4 alcohol selected from methanol, ethanol, propanol, and butanol.

[0075] In certain embodiments, the chemical agent is a mixture of a non-polar solvent capable of swelling the polymer (i.e., a swelling agent) and an agent capable of breaking or hydrolyzing the ester bond, where the swelling agent is preferably a chlorinated solvent selected from dichloromethane, dichloroethane, tetrachloroethane, chloroform, carbon tetrachloride, and trichloroethane. In another particular embodiment, the chemical agent is an acid selected from ethylene glycol, hydrochloric acid, sulfuric acid, or a Lewis acid.

[0076] Target plastic article The inventors of the present invention have developed a decomposition method for decomposing plastic products containing polymers, preferably thermoplastic polymers such as polyesters and / or polyamides and / or polyolefins. The method of the present invention can be advantageously used for plastic waste collection and / or plastic articles from industrial waste. In particular, the method of the present invention can be used to decompose household plastic waste including plastic bottles, plastic trays, plastic bags and plastic packaging, soft and / or hard plastics, which may be contaminated with food residues, surfactants, etc. Alternatively or additionally, the method of the present invention can be used to decompose used plastic fibers, such as fibers provided from fabrics, textiles and / or industrial waste. In particular, the method of the present invention can be used for PET plastics and / or PET fiber waste, such as PET fibers provided from fabrics, textiles or tires. Interestingly, the method of the present invention enables the production of monomers and / or oligomers and / or any decomposition products that can be further recovered and / or reprocessed.

[0077] In certain embodiments, the plastic product is selected from plastic bottles, plastic trays, plastic bags and plastic packaging, rigid or flexible plastic waste including soft and / or hard plastics, i.e., plastic waste not formed as fibers and / or crystalline plastic fibers, particularly crystalline plastic fibers containing a thermoplastic polymer (e.g., yarns, filaments, cords, ropes, fabrics and non-woven fabrics).

[0078] In certain embodiments, the method of the present invention is used to decompose plastic products containing at least one thermoplastic polymer, particularly one semi-crystalline thermoplastic polymer.

[0079] Advantageously, the method of the present invention is used to decompose plastic products containing at least one polyester selected from polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene isosorbide terephthalate (PEIT), polylactic acid (PLA), polyhydroxyalkanoate (PHA), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polybutylene adipate terephthalate (PBAT), polyethylene furanoate (PEF), polycaprolactone (PCL), poly(ethylene adipate) (PEA), polyethylene naphthalate (PEN), polycyclohexylene dimethylene terephthalate (PCT), polyethylene succinate (PES), poly(butylene succinate - co - terephthalate) (PBST), poly(butylene succinate / terephthalate / isophthalate) - co - (lactate) (PBSTIL), and blends / mixtures of these polymers. In particular, the method of the present invention is used to decompose plastic products containing at least one aromatic polyester selected from polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene isosorbide terephthalate (PEIT), polybutylene adipate terephthalate (PBAT), polyethylene furanoate (PEF), and blends / mixtures of these polymers.

[0080] In certain embodiments, the method of the present invention is used to decompose plastic products containing at least one polyester, preferably at least PET or PLA.

[0081] Alternatively, the method of the present invention is used to decompose a plastic product containing at least one polyamide selected from polyamide-6 or poly(β-caprolactam) or polycaproamide (PA6), polyamide-6,6 or poly(hexamethylene adipamide) (PA6,6), poly(11-aminoundecanoamide) (PA11), polydodecanolactam (PA12), poly(tetramethylene adipamide) (PA4,6), poly(pentamethylene sebacamide) (PA5,10), poly(hexamethylene azelaamide) (PA6,9), poly(hexamethylene sebacamide) (PA6,10), poly(hexamethylene dodecanoamide) (PA6,12), poly(m-xylylene adipamide) (PAMXD6), polyhexamethylene adipamide / polyhexamethylene terephthalamide copolymer (PA66 / 6T), polyhexamethylene adipamide / polyhexamethylene isophthalamide copolymer (PA66 / 6I), and blends / mixtures of these materials.

[0082] Alternatively, the method of the present invention is used to decompose a plastic product containing at least one polyolefin selected from polyethylene, polypropylene, polymethylpentene, polybutene-1, polyisobutylene, ethylene propylene rubber, ethylene propylene diene monomer rubber, ethylene vinyl alcohol, one or more ethylene-carbon monoxide copolymers, and modified products thereof.

[0083] In certain embodiments, the plastic product comprises at least two types of polymers. More generally, the plastic products targeted by the methods of the present invention can include different types of polymers derived from petrochemicals, such as polyamides, polyolefins or vinyl polymers, or from biological sources, such as rubber, wood or wood compounds, such as lignin, cellulose or hemicellulose and starch and their derivatives. Alternatively, the plastic product can comprise at least one polymer and additional components, such as metal compounds, mineral compounds, glass compounds, natural or synthetic fibers (such as glass fibers or carbon fibers), paper and these derivatives as defined in WO 2015 / 173265.

[0084] Interestingly, the methods of the present invention enable the production of monomers and / or oligomers and / or further recoverable and / or reprocessable degradation products.

[0085] Production of Monomers / Oligomers / Degradation Products Another object of the present invention is a method for producing monomers and / or oligomers and / or degradation products from a plastic product comprising at least one polymer, the method comprising continuously subjecting the plastic product to melt spinning, cooling the resulting fibers, and then depolymerizing at least one target polymer in the fibers.

[0086] Another object of the present invention is a method for decomposing a plastic article containing at least one polymer, wherein the plastic product has been pre-spun, the polymer of the plastic product is optionally at least partially amorphous, and the plastic product is contacted with a depolymerizing agent capable of decomposing the polymer, preferably a biological agent, more preferably a depolymerase. In certain embodiments, the plastic product is depolymerized under composting conditions or environmental conditions. In particular, the plastic product is subjected to industrial composting conditions at a temperature above 50 °C and / or to home composting conditions at a temperature of 15 °C to 35 °C. In such cases, the polymer of the plastic product can be decomposed by microorganisms in the compost and / or in the environment into water and / or carbon dioxide and / or methane.

[0087] A further object of the present invention is a method for decomposing a plastic product selected from rigid or flexible plastic waste and / or crystalline plastic fibers containing at least one polymer, the plastic product being pre-spun, the method comprising a depolymerization step of contacting the plastic product with a depolymerizing agent capable of decomposing the polymer, preferably a biological agent, more preferably a depolymerase. In an embodiment, the polymer of the plastic product is subjected to an amorphization step prior to the depolymerization step. In certain embodiments, the method of decomposing the plastic product and / or the method of producing monomers / oligomers further comprises a step of purifying the monomers and / or oligomers and / or decomposition products resulting from the depolymerization step. The monomers and / or oligomers and / or decomposition products can be recovered sequentially or continuously. Depending on the polymer and / or the starting plastic article, a single type of monomer and / or oligomer or multiple different types of monomers and / or oligomers can be recovered. The recovered monomers and / or oligomers and / or decomposition products can be purified using all suitable purification methods and adjusted to a repolymerizable form. In a preferred embodiment, the repolymerizable monomers and / or oligomers can then be reused to synthesize a polymer. One skilled in the art can readily adapt the process parameters to the monomers / oligomers and the polymer to be synthesized.

[0088] A further object of the present invention is a method for recycling a plastic product selected from rigid or flexible plastic waste and / or crystalline plastic fibers containing at least one polymer, the method comprising continuously subjecting the plastic product to a melt spinning step and a depolymerization step, and recovering monomers and / or oligomers of such polymers. Preferably, the depolymerizing agent is a biological agent, more preferably a depolymerase suitable for decomposing the polymer of the plastic product.

[0089] For this reason, an object of the present invention is to use a spun plastic product containing at least one polymer and subject the spun plastic product to a depolymerization step, preferably by using a depolymerizing agent selected from biological agents, more preferably depolymerases, to produce monomers and / or oligomers of such polymers.

[0090] Also, the embodiments described above in connection with the decomposition method are also applicable to methods for producing monomers / oligomers, methods for recycling plastic products, and recycling methods.

[0091] Production of biodegradable plastics Another object of the present invention is to provide a plastic product containing at least one polymer and incorporating at least one enzyme capable of decomposing the polymer, where the enzyme is used in the following process: a. A process of melt-spinning the plastic product, where the melt-spinning step is carried out at a temperature above the Tc of the polymer, preferably above the Tm, and where the cooling of the obtained fibers is carried out in less than 30 seconds after the melt-spinning step, preferably immediately after the melt-spinning step, by subjecting the fibers to cooling air at a temperature below the Tc and / or Tg of the polymer. b. The obtained cooled fibers are incorporated into the plastic product according to a process of subjecting them to a liquid containing a depolymerizing agent preferably selected from depolymerases.

[0092] Further aspects and advantages of the present invention will be disclosed in the following examples. The following examples should be considered illustrative and not limiting of the scope of this application. These examples provide experimental data supporting the present invention and means for implementing the present invention.

[0093] Examples Example 1 - A method for decomposing a plastic product containing PET, including a melt-blown spinning process Melt-blown spinning process Colored and washed flakes from PET bottles containing 98% PET were extruded using an Intarema 1108TE extruder equipped with a melt filter SC_4_134_RTF having a filter area of 564 cm 2 to obtain pellets. Pelletization was carried out using an ECON UWP EUP 150 underwater pelletizer having a die containing 8 holes each with a diameter of 2.9 mm. The extrusion temperature was in the range of 265 °C to 285 °C, and a screw speed of 155 rpm was used.

[0094] Some of the pellets were used as a control (C1), and the other pellets were dried at 80 °C for 6 hours and used in the melt spinning process (nonwoven fabric manufacturing).

[0095] The melt blown spinning machine is manufactured by Hills Inc (FL, USA) and is described in Table 1.

[0096]

Table 1

[0097] The parameters used in the production of nonwoven fabrics by melt spinning and their main characteristics are summarized in Table 2.

[0098]

Table 2

[0099] The fibers coming out of the spinning machine are cooled by ambient air (20 - 25 °C). The crystallinity levels of S1 and S2 are approximately 13% and 12% respectively.

[0100] The porosity level of the nonwoven fabric product is given by the following equation:

Equation

[0101] A second control (C2) was produced by finely pulverizing a part of the C1 pellets using a disk mill equipped with a 500 μm screen, to obtain a fine powder having the following particle size distribution: D(10) = 138 μm; D(50): 326 μm; D(90): 651 μm.

[0102] A) Depolymerization in glass bottles The depolymerization process was carried out using a mutant of LC-chitinase (Sulaiman et al., Appl Environ Microbiol. 2012 Mar). Such a mutant (LCC-ICCIG) corresponding to the enzyme of SEQ ID NO: 1 having the following mutations F208I + D203C + S248C + V170I + Y92G was expressed as a recombinant protein in Trichoderma reesei.

[0103] For the depolymerization test, the spinning samples S1 and S2 were cut into small pieces of about 2 × 2 cm with scissors.

[0104] For each sample (S1, S2, C1, and C2), 100 mg was weighed and introduced into a 250 ml glass bottle containing 49 mL of 0.1 M potassium phosphate buffer (pH 8). Depolymerization was initiated by adding 1 mL of a 0.1 mg / mL enzyme solution into 0.1 M potassium phosphate (pH 8) and then incubating each sample at 60 °C and 150 rpm in a Multitron pro (Infors HT, Switzerland).

[0105] The depolymerization rate of PET was measured by periodic sampling. The samples were analyzed by ultra-high performance liquid chromatography (UHPLC) to measure the amount of terephthalic acid equivalents produced according to the method described herein.

[0106] The TA equivalent concentration was measured by chromatography (UHPLC). If necessary, the samples were diluted with 100 mM potassium phosphate buffer (pH 8). 1 mL of the sample or diluted sample was mixed with 1 mL of methanol and 100 μL of 6N HCl. After homogenization and filtration through a 0.45 μm syringe filter, 20 μL of the sample was injected into a UHPLC, Ultimate 3000 UHPLC system (Thermo Fisher Scientific, Waltham, MA) including a pump module, an autosampler, a column temperature-controlled at 25 °C, and a UV detector at 240 nm. Terephthalic acid (TA) and the oligomers produced (MHET and BHET) were separated at 1 mL / min using a methanol gradient (30% - 90%) in 1 mM H2SO4 through an HPLC Discovery HS C18 column (150 mm × 4.6 mm, 5 μm) equipped with a precolumn (Supelco, Bellefonte, PA). TA, MHET, and BHET were measured according to a calibration curve prepared from commercially available TA and BHET and in-house synthesized MHET. The TA equivalent is the sum of the measured TA and the TA equivalents in the measured MHET and BHET. The hydrolysis rate of the sample was calculated based on the total amount of TA equivalents (TA + MHET + BHET) at a given time versus the total amount of TA determined in the initial sample. The results of the depolymerization rate after 6 hours and 9 hours are shown in Table 3 below.

[0107]

Table 3

[0108] The results show that the melt spinning process can significantly improve the depolymerization rate of PET in the spun plastic product compared to the extruded (unspun) plastic product (C1). Further, the results also show that the melt spinning process can improve the depolymerization rate of PET in the spun plastic product by at least 50% compared to the extruded (unspun) and micronized plastic product (C2).

[0109] Example 2 - Method for decomposing a plastic product containing PET, including a multifilament manufacturing process A) Multifilament manufacturing process Colored and washed flakes from a PET bottle containing 95% PET were extruded with the same extruder as in Example 1 - A. Some of the pellets from this process with a crystallization level of 16% were used as a control (referred to as C3). The other pellets were dried at 140°C for 4 hours and then extruded and spun.

[0110] The spinning machine used for multifilament production was a Hills Inc (FL, USA) machine equipped with a 19 mm (3 / 4 inch) single - screw extruder with an L / D ratio of 30:1 composed of three zones. The melt spinning process includes a melt pump, a multifilament spinneret with 36 holes each having a diameter of 0.6 mm, a winding roll (R1), a drawing roll (R2), a relaxation roll (R3), and a winder.

[0111] The temperatures used for extrusion from the first extruder zone to the spinneret were 265°C - 270°C - 280°C - 280°C - 280°C. The temperatures at rolls R1 - R2 - R3 were set at 95°C - 100°C - 50°C. The other parameters are listed in Table 4 below.

[0112]

Table 4

[0113] The multifilament was cooled with ambient air, wound around a spool, and cut into staple fibers 12 mm in length (Sample S3). Its crystallinity level was 9%.

[0114] B) Depolymerization in a glass bottle The depolymerization of Samples S3 and C3 was carried out under the same conditions as in Example 1-B. After 23 hours, S3 showed 80% depolymerization. On the other hand, the control C3 showed less than 2% depolymerization.

[0115] The results show that the melt spinning process can improve the depolymerization rate of PET in the spun plastic product compared to the unspun extruded plastic product.

Claims

**Claim 1** A method for decomposing a plastic product comprising at least one thermoplastic polymer, a. subjecting the plastic product to a melt spinning process to obtain fibers of the plastic product, wherein the melt spinning process is carried out on a plastic product in a partially or fully molten state, the molten plastic product is extruded through a spinneret for a non-woven product, and the obtained fibers exhibit a porosity of more than 30%, and b. depolymerizing at least one thermoplastic polymer of the fibers by contacting the fibers with a chemical depolymerizing agent and / or a biological depolymerizing agent. A method. **Claim 2** The method according to claim 1, wherein the melt spinning process is carried out at a temperature above the crystallization temperature (Tc) of at least one thermoplastic polymer of the plastic product. **Claim 3** The method according to claim 1 or 2, wherein the molten plastic product is extruded through a spinneret for filaments comprising monofilaments or multi-component filaments. **Claim 4** The method according to claim 3, wherein the plastic product is selected from plastic bottles, plastic trays, plastic bags and plastic packaging, rigid or flexible plastic waste including soft and / or hard plastics and / or crystalline plastic fibers. **Claim 5** The method according to any one of claims 1 to 4, wherein the fibers are cooled by subjecting the fibers to a temperature below the crystallization temperature (Tc) of at least one target thermoplastic polymer of the plastic product. **Claim 6** The method according to claim 5, wherein the target thermoplastic polymer in the fibers exhibits a crystallization rate of at most 30% after cooling. **Claim 7** The method according to any one of claims 1 to 6, wherein the depolymerization step comprises contacting the fibers with a biological depolymerizing agent. **Claim 8** The method according to claim 7, wherein the biological depolymerizing agent is a depolymerase. **Claim 9** The method according to claim 7, wherein the biological depolymerizing agent is a depolymerase capable of decomposing at least one thermoplastic polymer of the plastic product. **Claim 10** The method according to any one of claims 1 to 9, further comprising a step of recovering the oligomers and / or monomers generated by the depolymerization step and optionally a step of purifying them. **Claim 11** The method according to any one of claims 1 to 10, wherein at least one thermoplastic polymer is a polyester selected from polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene isosorbide terephthalate (PEIT), polylactic acid (PLA), polyhydroxyalkanoate (PHA), polybutylene succinate (PBS), polybutylene succinate adipate (PBSA), polybutylene adipate terephthalate (PBAT), polyethylene furanoate (PEF), polycaprolactone (PCL), poly(ethylene adipate) (PEA), polybutylene succinate terephthalate (PBST), polyethylene succinate (PES), poly(butylene succinate / terephthalate / isophthalate)-co-(lactate) (PBSTIL), and blends / mixtures of these materials.

12. A method for decomposing a plastic product containing at least PET, comprising: a. subjecting the plastic product to melt spinning at a temperature above 170 °C to obtain fibers from the plastic product, cooling the obtained fibers at a temperature below 100 °C, wherein the melt spinning process is carried out on a plastic product in a partially or wholly molten state, the molten plastic product is extruded through a spinneret for a non-woven product, and the obtained fibers exhibit a porosity of more than 30%; b. depolymerizing the PET in the fibers; and optionally, c. recovering and optionally purifying the oligomers and / or monomers resulting from the depolymerization of the PET. Method.

13. The method according to claim 12, wherein the depolymerizing step is carried out by contacting the fibers with a depolymerase or cutinase.

14. A method for producing monomers and / or oligomers and / or degradation products from a plastic product containing at least one thermoplastic polymer, the method comprising continuously subjecting the plastic product to a melt spinning process (wherein the melt spinning process is carried out on the plastic product in a partially or fully molten state, the molten plastic product is extruded through a spinneret for non-woven products, and the resulting fibers exhibit a porosity of more than 30%) and a depolymerization process comprising exposing the plastic product to a depolymerase. Method.

15. A method for decomposing a spun plastic product containing at least one thermoplastic polymer, The spun plastic product is contacted with a depolymerizing agent capable of decomposing at least one thermoplastic polymer of the plastic product, wherein the spun plastic product is obtained from rigid or flexible plastic waste and / or crystalline plastic fibers subjected to a melt spinning process to obtain the fibers of the plastic product, and wherein the melt spinning process is carried out on the plastic product in a partially or fully molten state, the molten plastic product is extruded through a spinneret for non-woven products, and the resulting fibers exhibit a porosity of more than 30%. Method.

16. The method according to claim 15, wherein the thermoplastic polymer of the plastic product is pre-amorphized before the depolymerization step.

17. A method for recycling a plastic product selected from rigid or flexible plastic waste and / or crystalline plastic fibers and containing at least one thermoplastic polymer, The method includes a step of depolymerizing at least one target thermoplastic polymer of the plastic product, wherein the plastic product has been pre-melt spun, and wherein the melt spinning process is carried out on the plastic product in a partially or fully molten state, the molten plastic product is extruded through a spinneret for non-woven products, and the resulting fibers exhibit a porosity of more than 30%. Method.

18. The method according to claim 17, further comprising a step of recovering the monomers and / or oligomers of the thermoplastic polymer.

19. The method according to any one of claims 15 to 18, wherein the depolymerization step is carried out by subjecting the spun plastic product to a biological depolymerizing agent.

20. The method according to any one of claims 15 to 18, wherein the depolymerization step is carried out by subjecting the spun plastic product to a biological depolymerizing agent which is a depolymerase.

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