Method for degrading a plastic product

Abstract

The present invention relates to a method for degrading a plastic product comprising at least one polymer, the method comprising the steps of: foaming the plastic product at least partially; and depolymerizing at least one target polymer of the at least partially foamed plastic product, wherein the foaming step is performed at a temperature in which the plastic product is in a partially or completely molten state.

Description

Technical Field

[0001] This invention relates to a method for degrading plastic products. The method specifically includes the step of foaming the plastic product before depolymerizing at least one polymer of the plastic product. The method is particularly suitable for degrading plastic products comprising polyesters and / or polyamides, preferably polyethylene terephthalate and / or polylactic acid. The invention also relates to a method for producing monomers and / or oligomers from at least partially foamed plastic products. Background Technology

[0002] Plastics are inexpensive and durable materials used in a wide range of products (food packaging, textiles, etc.). As a result, plastic production has increased dramatically over the past few decades. Furthermore, most plastics are used for single-use, disposable applications, such as packaging, agricultural films, disposable consumer goods, or short-lived products intended to be discarded within a year of manufacture. Due to the durability of the polymers involved, large quantities of plastics accumulate in landfills and natural habitats around the world, creating increasing environmental problems. For example, in recent years, polyethylene terephthalate (PET)—an aromatic polyester derived from terephthalic acid and ethylene glycol—has been widely used in the manufacture of several products intended for human consumption, such as food and beverage packaging (e.g., bottles, convenience soft drink packets, food bags) or textiles, fabrics, blankets, carpets, etc.

[0003] Various solutions, ranging from plastic degradation to plastic recycling, have been investigated to reduce the environmental and economic impacts associated with plastic waste accumulation, including recycling technologies and the use of such plastics to produce energy. Mechanical recycling technology remains the most commonly used, but it faces several drawbacks. In practice, it requires extensive and costly sorting due to molecular weight loss during the process and the uncontrolled presence of additives in the recycled products, leading to downgraded applications. Actual recycling technologies are also expensive, thus recycled plastic products are generally not competitive compared to virgin plastics.

[0004] Recently, innovative processes for the enzymatic recycling of plastic products have been developed and described (e.g., WO 2014 / 079844, WO 2015 / 097104, WO 2015 / 173265, and WO 2017 / 198786). In contrast to traditional recycling technologies, these enzymatic depolymerization processes allow the recovery of the polymer's chemical components (i.e., monomers and / or oligomers). The resulting monomers / oligomers can be recycled and used to remanufacture plastic articles, thus leading to an unlimited recycling of plastics. These processes are particularly suitable for recovering terephthalic acid and ethylene glycol from plastic products containing PET.

[0005] However, a process with improved degradation rates is always needed. Summary of the Invention

[0006] By improving the process for degrading plastic products, the inventors have demonstrated that the degradation step can be improved by increasing the contact area between the plastic product and the degradation agent. The inventors have therefore developed a method in which the surface area of ​​the plastic product is increased before subjecting it to the degradation step. More specifically, the inventors propose subjecting the plastic product to a foaming step before the depolymerization step. Advantageously, the foaming step allows for an increase in the porosity of the plastic product, thereby increasing the surface area of ​​the plastic product that can contact the degradation agent, and facilitating the subsequent depolymerization of one or more polymers constituting the plastic product. The method of the present invention is particularly suitable for degrading plastic products containing polyethylene terephthalate.

[0007] In this regard, one object of the present invention is to provide a method for degrading a plastic product comprising at least one polymer, the method comprising the steps of: foaming the plastic product at least partially; and depolymerizing at least one target polymer of the at least partially foamed plastic product, wherein the foaming step is carried out at a temperature in which the plastic product is in a partially or completely molten state.

[0008] Preferably, the foaming step is carried out at a temperature above the crystallization temperature (Tc) of the target polymer, preferably at or above the melting temperature (Tm) of the polymer, and is implemented using physical foaming agents and / or chemical foaming agents.

[0009] Another object of the present invention is to provide a method further comprising, less than 30 seconds after the foaming step, cooling the at least partially foamed plastic product by subjecting it to a temperature below the crystallization temperature (Tc) of the polymer, preferably below the glass transition temperature (Tg) of the polymer.

[0010] Advantageously, the method of the present invention is carried out at least in part in an extruder.

[0011] In one embodiment, the depolymerization step includes contacting the plastic product with a depolymerizing agent selected from chemical and / or biological depolymerizing agents.

[0012] Another object of the present invention is to provide a method for degrading plastic products containing PET, the method comprising the following steps:

[0013] a. The plastic product is at least partially foamed with a foaming agent preferably selected from chemical foaming agents, wherein the foaming step is performed at a temperature above 170°C, preferably above 185°C, more preferably above 200°C, and even more preferably above 220°C, 240°C, 245°C, 250°C, 255°C, 260°C, or 265°C.

[0014] b. Less than 30 seconds after the foaming stage, the at least partially foamed plastic product is cooled at a temperature below 100°C, preferably below 90°C;

[0015] c. Depolymerizing PET plastic products by contacting them with depolymerizing enzymes, particularly esterases, preferably keratinases or lipases, more preferably keratinases.

[0016] According to one embodiment of the invention, the plastic product is contacted with a depolymerization enzyme prior to the depolymerization step (e.g., during the cooling step), and the depolymerization step includes contacting the plastic product in a liquid that does not contain the depolymerization enzyme.

[0017] According to another implementation, the depolymerization step includes subjecting the plastic product to composting conditions.

[0018] Another object of the present invention is to provide a method for producing monomers and / or oligomers and / or degradation products from a plastic product comprising at least one polymer, preferably PET, the method comprising subjecting the plastic product sequentially to a foaming step and a depolymerization step, preferably including exposing the plastic product to a depolymerizing enzyme, preferably a keratinase.

[0019] Another object of the present invention is to provide a method for degrading at least partially foamed plastic products comprising at least one polymer, wherein the at least partially foamed plastic product is contacted with a depolymerizing agent capable of degrading at least one target polymer, and optionally wherein the polymer has undergone an amorphization step and the at least partially foamed plastic product is contacted with a depolymerizing enzyme to degrade the polymer. Detailed Implementation

[0020] definition

[0021] This disclosure will be better understood by referring to the following definitions.

[0022] In the context of this invention, the terms "plastic article" or "plastic product" are used interchangeably and refer to any article or product comprising at least one polymer, such as plastic sheets, trays, tubes, rods, profiles, shapes, 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, carpet waste, fabrics, textiles, etc. More preferably, the plastic article refers to plastic or textile waste. Preferably, the plastic article comprises a mixture of semi-crystalline and / or amorphous polymers. The plastic article may also contain additional substances or additives, such as plasticizers, minerals, organic fillers, dyes, etc.

[0023] "Polymer" refers to a compound or mixture of compounds whose structure consists of multiple repeating units (i.e., "monomers") linked by covalent chemical bonds. In the context of this invention, the term "polymer" refers to such compounds used in plastic product compositions. For example, synthetic polymers include petroleum-derived polymers such as polyolefins, aliphatic or aromatic polyesters, polyamides, polyurethanes, and polyvinyl chloride. In the context of this invention, polymer refers to a thermoplastic polymer, i.e., a polymer that becomes moldable above a certain temperature and solidifies upon cooling.

[0024] The term “depolymerization” in relation to polymers or plastic articles containing polymers refers to the process of depolymerizing and / or degrading at least one polymer of a polymer or plastic article into smaller molecules, such as monomers and / or oligomers and / or any degradation products.

[0025] According to the present invention, "oligomer" refers to a molecule containing 2 to about 20 monomer units. For 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.

[0026] In the context of this invention, the term "polyester" refers to a polymer containing ester functional groups in its main chain. The ester functional group is characterized by carbon atoms bonded to three other atoms: a single bond to carbon, a double bond to oxygen, and a single bond to oxygen. The single-bonded oxygen atom is bonded to another carbon atom. Depending on the composition of its main chain, a polyester can be aliphatic, aromatic, or semi-aromatic. Polyesters can be homopolymers or copolymers. For example, polyethylene terephthalate is a semi-aromatic copolymer composed of two monomers: terephthalic acid and ethylene glycol.

[0027] In the context of this invention, "crystalline polymer" or "semi-crystalline polymer" refers to a partially crystalline polymer in which crystalline and amorphous regions coexist. The crystallinity of a semi-crystalline polymer can be estimated by various analytical methods, typically ranging from 10% to 90%. For example, differential scanning calorimetry (DSC) or X-ray diffraction can be used to determine the crystallinity of a polymer. Other techniques are also suitable for estimating the crystallinity of polymers with lower reliability, such as X-ray scattering (XS) (including small-angle and wide-angle XS) and infrared spectroscopy. In this disclosure, crystallinity has been measured using DSC. More specifically, DSC measurements are performed as follows: a small sample (a few milligrams) is heated at a constant heating rate from ambient temperature or below to a high temperature above the melt temperature (Tm) of the polyester. Heat flow data are collected and the temperature is plotted. The crystallinity Xc (%) is calculated as follows:

[0028]

[0029] in

[0030] -ΔH f It is the enthalpy of fusion, which can be determined by integrating the endothermic melting peak.

[0031] -ΔH cc It is the enthalpy of cold crystallization, determined by integrating the exothermic cold crystallization peak.

[0032] -w t It is the weight fraction of polyester in the plastic, and

[0033] -ΔH f,100％ This refers to the enthalpy of melting of a fully crystalline polymer, which can be found in the literature. For example, the ΔH of PET... f,100％ Taken from the literature, it is 125.5 J / g (Polymer Data Handbook, 2nd Edition, edited by James E. Mark, Oxford, 2009). According to the literature, PLA's ΔH f,100％ Equal to 93J / g (Fisher EW, Sterzel HJ, Wegner G., Investigation of the structure of solution grown crystals of lactide copolymers by means of chemical reactions, Kolloid Zeitschrift&Zeitschrift fur Polymere, 1973, 251, p980-990).

[0034] The tolerance for crystallinity is approximately 10%. Therefore, approximately 25% crystallinity corresponds to a crystallinity between 22.5% and 27.5%.

[0035] In the context of this 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 using 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 this disclosure, the disclosed Tg, Tc, and Tm of the polymer correspond to temperatures measured using DSC.

[0036] Foaming steps

[0037] The inventors have demonstrated that the depolymerization rate of polymers (particularly polyesters and / or polyamides and / or polyolefins) contained in a plastic product can be increased by subjecting the plastic product to a foaming step prior to subjecting one or more polymers to a depolymerization step. The foaming step allows for an increase in the contact surface (i.e., contact area) between the polymer and the depolymerizing agent. In other words, compared to the same plastic product without foaming, by increasing the contact surface between the plastic product and the degrading agent, the depolymerization rate can be increased and / or the amount of degrading agent can be reduced and / or the time required to degrade the plastic product can be reduced. This invention particularly relates to plastic products comprising at least one thermoplastic polymer.

[0038] According to the invention, the foaming step is carried out at a temperature in which the plastic product is in a partially or completely molten state. Specifically, the foaming step is carried out at a temperature higher than the crystallization temperature (Tc) of the target polymer (i.e., the polymer intended for degradation or depolymerization) of the plastic product. Preferably, the plastic product is subjected to a temperature at or above the melting temperature (Tm) of the target polymer. Even more preferably, the plastic product is subjected to a temperature between Tm+5°C and Tm+25°C of the target polymer, preferably between Tm+10°C and Tm+25°C, more preferably between Tm+15°C and Tm+25°C, such as Tm+20°C of the target polymer. In another embodiment, the plastic product is subjected to a temperature between Tm+25°C and Tm+50°C of the target polymer. In yet another embodiment, the plastic product is subjected to a temperature corresponding to Tm+50°C or higher of the target polymer.

[0039] According to one embodiment of the invention, the plastic product comprises several different polymers. Specifically, the plastic product contains at least 51% by weight of the target polymer. In this case, the plastic product advantageously undergoes a temperature at or above Tc, or a temperature at or above Tm of the target polymer. Alternatively, the plastic product undergoes a temperature at or above the highest Tc or Tm of the polymer contained in the plastic product.

[0040] In one embodiment, the plastic product comprises PET, and the foaming step includes subjecting the plastic product to a temperature above 170°C, preferably at or above 230°C, more preferably between 250°C and 300°C. Even more preferably, the PET-containing plastic product is subjected to a temperature between 260°C and 280°C. In another embodiment, the PET-containing plastic product is subjected to a temperature at or above 300°C, preferably between 300°C and 320°C.

[0041] In another embodiment, the plastic product comprises PLA, and the foaming step includes subjecting the plastic product to a temperature above 110°C, more preferably at or above 145°C. In one embodiment, the plastic product comprises PLLA, and the foaming step includes subjecting the plastic product to a temperature at or above 170°C. In another embodiment, the plastic product comprises a stereocomplex PLA, and the foaming step includes subjecting the plastic product to a temperature at or above 230°C.

[0042] As used herein, the "foaming step" refers to the step of creating cells (also called bubbles) in the structure of a plastic product by using a foaming agent (also known as a blowing agent). The gas generated by the foaming agent creates bubbles within the molten or partially molten plastic material, forming closed and / or open cells in the plastic product. The resulting foamed plastic product exhibits a porous structure and has a lower density than the plastic product before the foaming step.

[0043] Based on the method of bubble formation, foaming agents can be classified as "physical foaming agents" or "chemical foaming agents." According to the present invention, the foaming step is carried out using one or more foaming agents selected from physical foaming agents, chemical foaming agents, and mixtures thereof. In one specific embodiment, the foaming step is carried out using one or more physical foaming agents. Alternatively, the foaming step is carried out using one or more chemical foaming agents. In another embodiment, the foaming step is carried out using both one or more physical foaming agents and one or more chemical foaming agents.

[0044] In the context of this invention, "physical blowing agent" refers to a compound that undergoes a physical state change during processing. Physical blowing agents include pressurized gases (such as nitrogen, carbon dioxide, methane, helium, neon, argon, xenon, and hydrogen or mixtures thereof) and low-boiling liquids (such as pentane, isopentane, hexane, dichloromethane, and dichlorotetrafluoroethane) that expand upon returning to atmospheric pressure during the foaming process, and which expand upon heating from a liquid to a gaseous state, thereby producing a larger volume of vapor.

[0045] In one specific embodiment, the physical blowing agent is a gas. Preferably, the physical blowing agent is selected from nitrogen, carbon dioxide, argon, helium, methane, neon, argon, xenon, hydrogen, or mixtures thereof. More preferably, the physical blowing agent is selected from carbon dioxide and nitrogen. In another embodiment, the physical blowing agent is selected from saturated aliphatic hydrocarbons, such as methane, ethane, propane, butane, pentane, and hexane; saturated alicyclic hydrocarbons, such as cyclopentane, cyclohexane, and ethylcyclopentane; aromatic hydrocarbons, such as benzene, toluene, and xylene; halogenated saturated hydrocarbons, such as dichloromethane and carbon tetrachloride; ethers, such as methyl acetal, acetal, 1,4-dioxane, and ketones, such as acetone, methyl ethyl ketone, and acetyl ketone, or mixtures thereof. Alternatively, the physical blowing agent is selected from low-boiling-point liquids, selected from pentane, isopentane, hexane, dichloromethane, and dichlorotetrafluoroethane. In particular, the boiling point of the low-boiling-point liquid is lower than the temperature at which the plastic product is in a partially or completely molten state. In one embodiment, one or more of the listed physical foaming agents may be used to carry out the foaming step. In a specific embodiment, the polymer of the plastic article undergoing the foaming step using a physical foaming agent has an intrinsic viscosity index greater than 0.5, preferably greater than 0.6.

[0046] In one specific implementation, a physical foaming agent is injected into a partially or fully molten plastic product. In other words, the plastic product is first heated, and as it melts, the physical foaming agent is injected into the molten material.

[0047] In the context of this invention, "chemical blowing agent" refers to a blowing agent that, during the heating of a polymer at a given temperature, undergoes a decomposition reaction, resulting in the release of gases such as nitrogen, carbon dioxide, carbon monoxide, nitrogen oxides, NOx compounds, ammonia, and / or water vapor. Such chemical blowing agents can be selected from azides, acylhydrazides such as p,p'-hydroxybis-(benzenesulfonylhydrazide), aminoureas such as p-toluenesulfonamide, azo compounds such as azodicarbonamide, triazoles such as nitrotriazolone, tetraazoles such as 5-phenyltetraazole, bicarbonates such as zinc bicarbonate or alkali metal bicarbonates such as sodium bicarbonate, acid anhydrides, peroxides, nitro compounds, and perchlorates. Alternatively, the chemical blowing agent can be selected from citric acid, carbonates, bicarbonates, mixtures thereof, or any commercial chemical blowing agent, such as those from Clariant. Or from Adeka Preferably, the chemical blowing agent comprises a mixture of citric acid and carbonates and / or a mixture of citric acid and bicarbonates. Alternatively, the chemical blowing agent comprises hydrogen peroxide. In one embodiment, one or more of the listed chemical blowing agents may be used to carry out the foaming step.

[0048] In one specific implementation, the foaming step includes mixing one or more chemical foaming agents with a plastic product at ambient temperature, and then subjecting the mixture to a temperature at which the plastic product is in a partially or completely molten state.

[0049] In another embodiment, a chemical foaming agent is added to at least partially molten plastic products. In other words, the plastic product is first heated, and as it melts, the chemical foaming agent is mixed into the molten material.

[0050] In one implementation, the foaming step is carried out using both one or more chemical foaming agents and one or more physical foaming agents.

[0051] In one embodiment, the method of the present invention comprises: contacting 0.1 to 10% by weight, preferably 0.1 to 5% by weight, of one or more foaming agents with 90% to 99.9% by weight, preferably 95% to 99.9% by weight, of a plastic product, based on the total weight of the mixed foaming agent / plastic product. Specifically, the method of the present invention comprises: contacting 0.1 to 10% by weight of a chemical foaming agent with 90% to 99.9% by weight, of a plastic product, based on the total weight of the mixed foaming agent / plastic product. Preferably, the method of the present invention comprises: contacting 1 to 5% by weight of a chemical foaming agent with 95% to 99% by weight of a plastic product. Alternatively, the method of the present invention comprises: contacting 0.1 to 5% by weight, preferably 0.1 to 3%, preferably 0.1% to 1% by weight of a chemical foaming agent with 95% to 99.9% by weight, preferably 97% to 99.9%, more preferably 99% to 99.9% by weight of a plastic product. In another embodiment, the method of the present invention includes contacting 0.1 to 5% by weight of a physical foaming agent with 95% to 99.9% by weight of the plastic product, based on the total weight of the mixed foaming agent / plastic product. Preferably, the method of the present invention includes contacting 0.1 to 3.5% by weight of a physical foaming agent with 96.5% to 99.9% by weight of the plastic product.

[0052] In one embodiment, the foaming step is carried out using one or more foaming agents and processing aids, such as waxes, nucleating agents, chain extenders, foaming agents, or water, preferably water. Specifically, the foaming step is carried out using one or more foaming agents and 0.01 to 10% by weight of processing aids, preferably 0.01 to 1% by weight, based on the total weight of the mixed foaming agent / plastic product / processing aids. Preferably, the foaming step is carried out using one or more chemical foaming agents and water, more preferably using a mixture of citric acid and water.

[0053] In one embodiment, the foaming step is carried out using an extruder, wherein the plastic product is subjected to temperatures in which the plastic product is in a partially or fully molten state. The foaming agent may be introduced into the extruder before heating, during heating, and / or when the material has already been heated and is in a molten state.

[0054] In another embodiment, the foaming step is carried out in batches using an autoclave, wherein the plastic product is saturated with a foaming agent, then subjected to sudden decompression and optionally placed in a hot oil bath. For example, pressure-induced or temperature-induced methods can be used. Batch foaming is particularly suitable for plastic products containing at least one polymer and additional components (e.g., composites containing glass or carbon fibers) that can be degraded in an extruder.

[0055] Alternatively, the foaming and / or cooling steps can be performed using any technique known to those skilled in the art.

[0056] Advantageously, the plastic product prior to the foaming step exhibits a porosity of less than 10%, preferably less than 5%, and more preferably less than 3%. In one embodiment, the at least partially foamed plastic product exhibits a porosity of 20% to 90%, preferably 25% to 50%. In particular, the porosity is between 30% and 40%. Alternatively, the plastic product exhibits a porosity of more than 20%, preferably more than 30%, and more preferably more than 40%. As used herein, the term "porosity" refers to the fraction of voids in a plastic product and corresponds to the ratio of the volume of voids (i.e., pores) within the plastic product to the total volume of the plastic product.

[0057] Porosity can be estimated by any method known to those skilled in the art. Preferably, the "porosity" (ε) of a plastic product is... T Estimate using the following equation:

[0058] in:

[0059] - It is the apparent density of foamed plastic products measured using a water hydrometer.

[0060] - It is the true density of a plastic product, measured based on its composition or on an unfoamed plastic composition. In particular, the plastic composition is in granular form.

[0061] A water hydrometer measures the mass of a specific volume of water as well as the mass of the same volume containing the water and a foamed plastic product whose density must be determined. This allows the apparent density of a sample to be determined, thereby obtaining the porosity of the material, provided that the density (i.e., true density) of the original (i.e., unfoamed) plastic product is known. For example, the literature states that the true density of a plastic product containing 100% PET is 1380 kg·m³. -3This corresponds to the density of PET. The water hydrometer method is particularly suitable for calculating the density of products with irregular shapes. For products with regular shapes (e.g., cylinders), the volume of the product can be directly calculated, thus assessing its apparent density. When the plastic product is a textile, the true density... Textile compositions based on extrusion rather than foaming (particulate form).

[0062] In one specific implementation, the at least partially foamed plastic product contains at least 95% PET and exhibits a weight of less than 1000 kg·m³. -3 Preferred weight is below 900 kg / m. -3 apparent density In one embodiment, the at least partially foamed plastic product exhibits a porosity between 40% and 70% and a porosity of less than 1000 kg·m³. -3 apparent density In one specific implementation, the plastic product contains at least 95% PET, and at least partially foamed plastic products exhibit a weight of less than 1000 kg·m³. -3 apparent density And a porosity greater than 30%. Preferably, the plastic product contains at least 95% PET, and at least partially foamed plastic products exhibit a porosity of less than 900 kg·m³. -3 apparent density Porosity should be above 30%, preferably above 40%.

[0063] In one embodiment, the at least partially foamed plastic product is at least partially foamed textile containing at least 85% PET and exhibiting a porosity of 10% to 70%.

[0064] In one embodiment, the plastic product undergoes a pretreatment step prior to the foaming step. The pretreatment step may include sorting and / or washing and / or disinfecting and / or sterilizing and / or biological cleaning of the plastic product prior to foaming. Alternatively or additionally, the pretreatment step may include physically transforming the plastic product into a film, flake, powder, pellet, or fiber prior to foaming.

[0065] The method of the present invention is particularly applicable to plastic products containing PET. Therefore, one object of the present invention is to provide a method for degrading a plastic product containing at least PET, and the method includes a step of at least partially foaming the plastic product and a step of depolymerizing the PET in the at least partially foamed plastic product, wherein the foaming step is preferably carried out using a chemical foaming agent, more preferably using citric acid, carbonates, bicarbonates, and mixtures thereof, and even more preferably using a mixture of citric acid and carbonates or a mixture of citric acid and bicarbonates.

[0066] As described above, the present invention is particularly applicable to plastic products containing thermoplastic polymers. The present invention can also be implemented with plastic products containing thermosetting polymers by adapting the foaming step.

[0067] Cooling steps

[0068] In one specific embodiment, the method of the present invention further includes a step of cooling at least partially foamed plastic products after the foaming step. In fact, as described above, the foaming step is carried out with plastic products heated to a molten state. According to one embodiment, after the foaming step, the foamed plastic product is subjected to a temperature cooler than the temperature of the foamed plastic product to rapidly reduce the temperature of the foamed plastic product and accelerate the curing of the foamed plastic product. The cooling step includes contacting the plastic product with any cooling fluid, including air and / or liquid.

[0069] In one specific implementation, the plastic product undergoes a cooling step less than 30 seconds, more preferably less than 20 seconds, and even more preferably less than 10 seconds after the foaming step. In particular, the plastic product undergoes a cooling step immediately after the foaming (i.e., heating) step ends.

[0070] This rapid cooling following the heating stage allows for at least partial amorphization of one or more polymers in the plastic product. Amorphization occurs during the foaming step (i.e., the heating step) by allowing at least partial disruption of the crystalline structure of one or more polymers in the plastic product, and rapid cooling allows the heated polymer to be fixed in an amorphous state. Therefore, polymer amorphization can be carried out during the foaming step by subjecting the plastic product to a temperature above Tc, preferably above the polymer's Tm, and then rapidly cooling the plastic product at a temperature below the polymer's Tc and / or Tg.

[0071] As used herein, the polymer-related terms “amorphization” and “performing amorphization” refer to a reduction in the crystallinity of a given polymer compared to its crystallinity before amorphization. Preferably, amorphization allows for a reduction in the crystallinity of the target polymer by at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, 70%, 80%, or 90% compared to its state before amorphization. Advantageously, amorphization results in a polymer having a crystallinity of up to 30%, preferably up to 25%, more preferably up to 20%, and even more preferably up to 15%. Alternatively, amorphization allows for maintaining the crystallinity of the polymer below 30%, preferably below 25%, more preferably below 20%, and even more preferably below 15%. Amorphization can be carried out by any method known to those skilled in the art to at least partially disrupt the crystalline structure of the polymer, particularly any method described in WO 2017 / 198786. Amorphization thereby enhances the polymer's ability to be depolymerized by biological agents.

[0072] Those skilled in the art can adjust the foaming and cooling temperatures according to the target polymer. Similarly, those skilled in the art know when and / or how to perform degassing during the foaming step, before and / or after the introduction of the foaming agent. Generally, the plastic product can be subjected to heat treatment and optional shear stress for a period of time sufficient to achieve amorphization of the target polymer. For example, depending on the temperature and / or the plastic product, such a period of time can include between 10 seconds and several minutes. In a preferred embodiment, the foaming step comprises subjecting the plastic product to shear stress and a temperature above the Tc of the target polymer in the plastic product, preferably at or above the Tm of said polymer. It is preferable to perform heating and shear stress simultaneously to increase amorphization during the foaming step.

[0073] According to the invention, the cooling step comprises subjecting the foamed plastic product to a temperature lower than the Tc of the target polymer of the plastic product, preferably lower than the Tg of the polymer. Subjecting the product to a temperature lower than the Tc of the target polymer is particularly suitable for polymers such as PBAT or any polymer with a Tg below 20°C. In another embodiment, cooling is performed by subjecting the heated plastic product to a temperature at least 20°C, preferably at least 30°C, 40°C, or 50°C lower than the Tc of the target polymer. In one embodiment, cooling is performed by subjecting the plastic product to room temperature (i.e., 25°C + / - 5°C). In another embodiment, cooling is performed by subjecting the plastic product to a temperature of about 20°C or about 10°C.

[0074] Generally, plastic products are subjected to cooling temperatures sufficient to lower the temperature at the very center of the product for a period of time. For example, depending on the initial temperature of the foamed plastic product (i.e., before the cooling step), and / or the cooling temperature and / or the properties / form of the plastic product, such a time period can range from 1 second to several minutes. In one embodiment, the plastic product is in extrusion form with a diameter less than 1 cm, preferably between 0.5 and 5 mm, and is subjected to cooling temperatures for less than 1 minute, preferably less than 30 seconds, more preferably less than 20 seconds, and even more preferably less than 10 seconds. Alternatively, the foamed plastic material exiting the extruder is formed into tubular or sheet shapes.

[0075] For example, the plastic product can be cooled by immersing it in a liquid at a cooling temperature after the foaming step. For example, the at least partially foamed plastic product can be immersed in a liquid at room temperature, more preferably at a temperature below room temperature at the end of the foaming step. For example, the plastic product can be immersed in a cold liquid with a temperature below 14°C, preferably below 10°C or below 5°C. In one specific embodiment, the plastic product is immersed in cold water, such as water at or below 5°C. Alternatively, the plastic product can be immersed in a liquid whose temperature is below the Tc of the target polymer. More generally, any method suitable for rapidly lowering the temperature of the plastic product (e.g., cold air) can be used.

[0076] In a preferred embodiment, the foaming step is carried out in an extruder. The extruder allows the plastic product to be subjected to both a given temperature and shear stress simultaneously or sequentially. Advantageously, the foamed plastic product exiting the extruder is directly cooled by immersion and / or by water pulverization. Advantageously, the extruder is selected from single-screw extruders, multi-screw extruders with co-rotating or counter-rotating designs, planetary roll extruders, dispersive kneaders, reciprocating single-screw extruders (co-kneaders), small extruders, or internal mixers.

[0077] In one embodiment, an underwater granulator or underwater strip granulator, allowing direct cutting of plastic material in cold water, is fixed to the head of an extruder, resulting in an immediate cooling stage in the production of plastic pellets. In such an embodiment, the plastic product is in pellet form, with a size less than 1 cm, preferably between 0.5 and 5 mm, and is cooled to a temperature of less than 1 minute, preferably less than 30 seconds, more preferably less than 20 seconds, and even more preferably less than 10 seconds. In particular, a micro-granulation underwater granulator for producing micro-particles smaller than 1 mm is fixed to the die head of the extruder.

[0078] Alternatively, the foaming step can be carried out in an autoclave, and the foamed plastic product can be cooled by contact with ambient air or cooling air or by immersion in a liquid at room temperature or below room temperature. Alternatively, the foaming and cooling steps can be performed using any technique known to those skilled in the art.

[0079] Therefore, one object of the present invention is to provide a method for degrading a plastic product comprising at least one polymer, the method comprising the following steps:

[0080] a. To foam a plastic product at least partially, wherein the foaming step is carried out at a temperature higher than the crystallization temperature (Tc) of the target polymer of the plastic product, preferably higher than the melting temperature (Tm) of said polymer; and

[0081] b. Cooling the at least partially foamed plastic product at a temperature below the polymer's Tc, preferably below the polymer's glass transition temperature (Tg), and

[0082] c. Depolymerize the target polymer.

[0083] Advantageously, the foaming agent is selected from chemical foaming agents. Preferably, the plastic product undergoes a cooling step less than 30 seconds after the foaming step, more preferably immediately thereafter.

[0084] Advantageously, at least partially foamed plastic products undergo a granulation step between the cooling step (b) and the depolymerization step (c) to obtain the granules disclosed above.

[0085] In one specific embodiment, the target polymer, which is at least partially amorphized and foamed, exhibits a crystallinity of up to 30%, preferably up to 25%, more preferably up to 20%. Preferably, the depolymerization step is carried out using a biodepolymerizing agent.

[0086] In another embodiment, the extruder further includes a spinneret for melt spinning of nonwoven products or for melt spinning of monofilaments or multifilaments, and preferably a cooling step is performed by using cooling air.

[0087] Therefore, another object of the present invention is to provide a method for degrading plastic products containing at least one polymer, the method comprising the following steps:

[0088] a. Foaming and melt spinning of the plastic product, wherein the foaming and melt spinning steps are carried out at a temperature higher than the Tc of the polymer, preferably higher than the Tm of the target polymer; and

[0089] b. Cool the at least partially foamed and spun plastic product at a temperature below the Tc of the target polymer, preferably below the Tg of the polymer;

[0090] c. Depolymerize the target polymer.

[0091] The foaming and melt spinning steps are carried out using an extruder containing a spinneret.

[0092] Advantageously, the foaming agent is selected from chemical foaming agents and / or the plastic product undergoes a cooling step less than 30 seconds after the spinning step, preferably immediately after the spinning step, and / or is depolymerized using enzymes.

[0093] A specific object of the present invention is to provide a method for degrading the above-disclosed plastic product, wherein the plastic product comprises PET. Advantageously, the foaming step is carried out in an extruder, and the cooling step is performed by subjecting the heated and partially foamed plastic product to a temperature below 100°C for less than 30 seconds after the foaming step, preferably below 90°C and preferably immediately after the foaming step. Alternatively, the cooling step is performed by subjecting the heated plastic product to a temperature below 50°C. In particular, the polymer is PET, and at least partially amorphous PET exhibits a crystallinity of up to 30%, preferably up to 25%, more preferably up to 20%.

[0094] In particular, an object of the present invention is to provide a method for degrading plastic products containing at least PET, the method comprising the following steps:

[0095] a. Using a foaming agent to at least partially foam a plastic product, wherein the foaming step is carried out at a temperature above 170°C, preferably above 185°C, more preferably above 200°C, and even more preferably above 220°C, 230°C, 240°C, 245°C, 250°C, 255°C, 260°C, or 265°C.

[0096] b. After the foaming step, preferably within 30 seconds, cool the at least partially foamed plastic product at a temperature below 100°C, preferably below 90°C; and

[0097] c. Depolymerize the PET.

[0098] Advantageously, the foaming agent is selected from chemical foaming agents, preferably citric acid, carbonates, bicarbonates, or mixtures thereof, and / or the plastic product undergoes a cooling step less than 30 seconds after the foaming stage. Advantageously, the PET in the foamed product exhibits a crystallinity of less than 20%, more preferably less than 5%, after the cooling stage, and the depolymerizing agent is an esterase, preferably a keratinase or lipase, more preferably a keratinase.

[0099] Depolymerization steps

[0100] According to the invention, following the foaming step and optionally the cooling step, the degradation process includes a depolymerization step of at least one polymer of the plastic product. According to a preferred embodiment, the depolymerization step targets at least one polymer that has previously been amorphized.

[0101] In one specific implementation, the depolymerization step includes contacting the plastic product with a depolymerizing agent, i.e., a chemical and / or biological reagent.

[0102] Advantageously, the depolymerization step is carried out in a liquid medium containing a depolymerizing agent.

[0103] In another specific embodiment, the plastic product is contacted with a depolymerizing agent prior to the depolymerization step. For example, after the foaming step, the plastic product is immersed in a liquid containing a depolymerizing agent. Specifically, the plastic product may be contacted with the depolymerizing agent during a cooling step (i.e., immersed in a coolant containing the depolymerizing agent). In one embodiment, the depolymerization step is subsequently carried out by immersing the plastic product in a liquid. In a preferred embodiment, this liquid does not contain a depolymerizing agent. In another embodiment, the depolymerization step is carried out by subjecting the plastic product to composting conditions. Specifically, the plastic product is subjected to industrial composting conditions at temperatures above 50°C, and / or domestic composting conditions at temperatures between 15°C and 35°C. In one embodiment, the foamed plastic product is contacted with a depolymerizing agent during a cooling step, and the depolymerization step is subsequently carried out by subjecting the plastic product to a stimulant capable of activating the depolymerizing agent. For example, the depolymerizing agent is a degrading enzyme, and the stimulant is at a specific temperature and / or humidity rate.

[0104] In one specific embodiment, the depolymerizing agent is a biological agent or contains a biological agent. In particular, the biological agent is a depolymerizing enzyme (i.e., an enzyme). Preferably, the depolymerizing enzyme is capable of degrading at least one polymer of the plastic product, preferably at least a polymer that has been previously amorphized.

[0105] The depolymerizing enzyme is advantageously selected from keratinase, lipase, protease, carboxylesterase, p-nitrobenzylesterase, esterase, scl-PHA depolymerizing enzyme, mcl-PHA depolymerizing enzyme, PHB depolymerizing enzyme, amidase, aryl-acylaminasase (EC 3.5.1.13), oligomer hydrolases, such as 6-aminohexanoic acid cyclic dimer hydrolases (EC 3.5.2.12), 6-aminohexanoic acid dimer hydrolases (EC 3.5.1.46), 6-aminohexanoic acid-oligomer hydrolases (EC 3.5.1.B17), oxidases, peroxidases, laccase (EC 1.10.3.2), oxygenases, lipoxygenases, monooxygenases, or lignin-degrading enzymes. In one specific embodiment, the plastic product is contacted with at least two different depolymerizing enzymes.

[0106] In one specific embodiment, the plastic product comprises PET, and the depolymerization enzyme is an esterase. Specifically, the depolymerization enzyme is a keratinase, preferably produced by a microorganism selected from *Bifidobacterium humicum*, *Schizosporium halophilum*, *Schizosporium spp.*, *Bifidobacterium*, *Bacillus subtilis*, *Fusarium solani*, *Pseudomonas*, *Rhodococcus*, *Pseudomonas mendoza*, and *Clostridium terrestris*, or any functional variant thereof. In another embodiment, the keratinase is selected from metagenomic libraries, such as LC-keratinase described in *Sulaimanet al., 2012* or esterase described in EP3517608, or any functional variant thereof, including depolymerization enzymes listed in WO 2018 / 011284 or WO 2018 / 011281. In yet another specific embodiment, the depolymerization enzyme is a lipase, preferably produced by *Inulinus spp.* In another specific embodiment, the depolymerase is a cutinase produced by a specific humic fungus, such as A0A075B5G4 mentioned in Uniprot or any functional variant thereof. In another embodiment, the depolymerase is selected from commercial enzymes, such as Novozym 51032 or any functional variant thereof.

[0107] In one specific embodiment, the plastic product comprises PLA, and the depolymerization enzyme is a protease, preferably produced by a microorganism selected from *Pseudomonas aeruginosa*, *Pseudomonas orientalis*, *Candida albicans* (proteinase K), *Dura mater*, *Resiliencea* LP175, *Thermophyton yunnanense* bacteria, or any known commercial enzymes for degrading PLA, such as... Or any functional variant thereof, including the depolymerases listed in WO 2016 / 062695, WO 2018 / 109183 or WO 2019 / 122308.

[0108] In another specific embodiment, the plastic product contains PDLA, and the depolymerase is an esterase, preferably a keratinase or lipase, more preferably selected from Cryptococcus spp. CLE, Burkholderia cepacia lipase PS, Bacillus amyloliquefaciens TB-13, Candida antarctica, Rhizopus, Saccharomyces viride, Cryptococcus cryptococcus or any functional variant thereof.

[0109] In another specific embodiment, the plastic product contains PA and the depolymerization enzyme is selected from amidases, aryl-acylaminases (EC 3.5.1.13), oligomer hydrolases, such as 6-aminohexanoic acid cyclic dimer hydrolases (EC 3.5.2.12), 6-aminohexanoic acid dimer hydrolases (EC 3.5.1.46), and 6-aminohexanoic acid oligomer hydrolases (EC 3.5.1.B17).

[0110] In another specific embodiment, the plastic product contains a polyolefin and the depolymerization enzyme is an oxidase, preferably selected from laccase, peroxidase, oxygenase, lipoxygenase, monooxygenase or lignin-degrading enzyme.

[0111] In another embodiment, the depolymerizing agent is a microorganism that expresses and excretes a depolymerizing enzyme. The microorganism may synthesize the depolymerizing enzyme naturally, or it may be a recombinant microorganism in which a recombinant nucleotide sequence encoding the depolymerizing enzyme is inserted, for example, using a vector. Specific embodiments of the depolymerization stage can be found in WO 2017 / 198786.

[0112] According to the present invention, several microorganisms and / or purified enzymes and / or synthetic enzymes may be used together or sequentially to depolymerize different kinds of polymers contained in the same or different plastic articles simultaneously undergoing the degradation process of the present invention.

[0113] The time required to depolymerize at least one polymer in a plastic article can vary depending on the plastic article and the target polymer (i.e., the properties and source of the plastic article, its composition, shape, molecular weight, etc.), the type and quantity of microorganisms / enzymes used, and various process parameters (i.e., temperature, pH, additional reagents, etc.). Those skilled in the art can readily adapt the process parameters to the plastic article and / or the depolymerizing enzyme.

[0114] In one specific embodiment, the plastic product comprises PET, and the depolymerization step is carried out by contacting the plastic product with a biodepolymerizing agent at temperatures including: between 20°C and 90°C, preferably between 30°C and 80°C, more preferably between 40°C and 75°C, even more preferably between 50°C and 75°C, and even more preferably between 60°C and 75°C. Furthermore, the depolymerization step is preferably carried out at a pH of 5-11, preferably 7-9, more preferably 7-8.5, and even more preferably 7-8. Alternatively, the depolymerization step can be carried out under industrial and / or composting conditions.

[0115] In one specific embodiment, the plastic product comprises PLA, and the depolymerization step is carried out by contacting the plastic product with a biodepolymerizing agent at temperatures including: between 20°C and 90°C, preferably between 20°C and 60°C, more preferably between 30°C and 55°C, more preferably between 40°C and 50°C, and even more preferably between 45°C. Furthermore, the depolymerization step is preferably carried out at a pH between 5 and 11, preferably between 7 and 10, more preferably between 8.5 and 9.5, and even more preferably between 8 and 9. In another specific embodiment, the depolymerization step may be carried out at a pH between 7 and 8. Alternatively, the depolymerization step may be carried out under industrial and / or composting conditions.

[0116] In another specific embodiment, the depolymerizing agent is a chemical reagent or contains a chemical reagent. Specifically, the chemical reagent is a catalyst selected from metal catalysts or stabilizers and non-toxic hydrosilanes (PMHS, TMDS), such as commercially available B(C6F5)3 and [Ph3C+,B(C6F5)4-] catalysts. Specifically, 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, and zeolites. In some embodiments, the catalyst used in the depolymerization process of the present invention includes at least one of the following: 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. Specifically, the catalyst comprises at least one of the following: germanium dioxide, cobalt acetate, titanium tetrachloride, titanium phosphate, titanium tetrabutoxide, titanium tetraisopropoxide, titanium tetran-n-propoxide, titanium tetraethanol, titanium tetramethanol, tetra(acetylacetone) titanium complex, tetra(2,4-hexanedione) titanium complex, tetra(3,5-heptadecane) titanium complex, dimethoxybis(acetylacetone) titanium complex, diethoxybis(acetylacetone) titanium complex, diisopropoxybis(acetylacetone) titanium complex, di-n-propoxybis(acetylacetone) titanium complex, dibutoxybis(acetylacetone) titanium complex, titanium dihydroxydiglycolate, titanium dihydroxydiglycolate, titanium dihydroxydilactate, and titanium dihydroxydihydroxydiglycolate. Titanium bis(2-hydroxypropionic acid), titanium lactate, titanium octanediol, titanium dimethoxybistriethanolamine, titanium diethoxybistriethanolamine, titanium dibutoxybistriethanolamine, hexamethyl disitiamate, hexaethyl disitiamate, hexapropyl disitiamate, hexabutyl disitiamate, hexaphenyl disitiamate, octamethyl tritiate, octaethyl tritiate, octapropyl tritiate, octabutyl tritiate, octaphenyl tritiate, hexaalkoxy disitiamate, 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 reagent can be selected from any catalyst known to those skilled in the art that has the ability to degrade and / or depolymerize the target polymer.

[0117] Alternatively, the chemical reagent is an acid or base catalyst capable of breaking polymer bonds, particularly ester bonds. Specifically, the chemical reagent involved in ester bond cleavage is a mixture of a hydroxide and an alcohol that can dissolve the hydroxide. The hydroxide is selected from alkali metal hydroxides, alkaline earth metal hydroxides, and ammonium hydroxide, preferably from sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide, magnesium hydroxide, ammonium hydroxide, and tetraalkylammonium hydroxide; the alcohol is selected from straight-chain, branched, cyclic alcohols, or combinations thereof, preferably from straight-chain C1-C4 alcohols such as methanol, ethanol, propanol, and butanol.

[0118] In one embodiment, the chemical reagent is a mixture of a nonpolar solvent capable of swelling the polymer (i.e., a swelling agent) and a reagent capable of breaking or hydrolyzing ester bonds, wherein the swelling agent is preferably a chlorinated solvent selected from dichloromethane, dichloroethane, tetrachloroethane, chloroform, tetrachloromethane, and trichloroethane. In another embodiment, the chemical reagent is an acid selected from ethylene glycol, hydrochloric acid, sulfuric acid, or Lewis acids.

[0119] In one specific embodiment, prior to the depolymerization step, the at least partially foamed and optionally amorphous plastic product may be subjected to cryogenic grinding, cryogenic milling, cryogenic grinding, or cryogenic ball milling. In one embodiment, the plastic product is crushed or ground prior to the depolymerization step. Advantageously, the plastic product is not subjected to a micronization step prior to the depolymerization step.

[0120] plastic products

[0121] The inventors have developed a method for degrading 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 articles from plastic waste collection and / or post-industrial waste. More specifically, the method of the present invention can be used to degrade household plastic waste, including plastic bottles, plastic trays, plastic bags and plastic packaging, soft and / or hard plastics, even those contaminated with food scraps, surfactants, etc. Alternatively, or additionally, the method of the present invention can be used to degrade used plastic fibers, such as fibers provided by fabrics, textiles and / or industrial waste. More specifically, the method of the present invention can be used for PET plastic and / or PET fiber waste, such as PET fibers provided by fabrics, textiles or tires. Interestingly, the method of the present invention allows for the production of monomers and / or oligomers and / or any degradation products that can be further recycled and / or reprocessed.

[0122] In one specific embodiment, the plastic product is selected from unfoamed plastic waste, including plastic bottles, plastic bags and plastic packaging, soft and / or hard plastics, fibers, textiles, and / or selected from foamed plastic products with a crystallinity greater than 30%, comprising thermoplastic polymers. This foamed plastic product undergoes a new foaming step during heating and a cooling step before depolymerization to achieve amorphization.

[0123] In one specific embodiment, the method of the present invention is used to degrade plastic products comprising at least one thermoplastic polymer, particularly a semi-crystalline thermoplastic polymer.

[0124] Advantageously, the method of the present invention is used to degrade plastic products comprising at least one polyester selected from: polyethylene terephthalate (PET); polypropylene terephthalate (PTT); polybutylene terephthalate (PBT); polyisosorbate terephthalate (PEIT); polylactic acid (PLA); polyhydroxyalkanoate (PHA); polybutylene succinate (PBS), polybutylene adipate succinate (PBSA), and polybutylene adipate terephthalate (PBA). Poly(T), polyethylene furanoate (PEF), polycaprolactone (PCL), polyethylene adipate (PEA), polyethylene naphthalate (PEN), polycyclohexyl terephthalate (PCT), polyethylene succinate (PES), poly(butylene succinate-co-butylene terephthalate) (PBST), poly(butylene succinate / terephthalate / butylene isophthalate)-co-(lactic acid ester) (PBSTIL), and blends / mixtures of these polymers. In particular, the method of the present invention is used to degrade plastic products comprising at least one of the following aromatic polyesters: polyethylene terephthalate (PET); polypropylene terephthalate (PTT); polybutylene terephthalate (PBT); polyisosorbate terephthalate (PEIT); polybutylene adipate terephthalate (PBAT), polyethylene furanate (PEF), and blends / mixtures of these polymers.

[0125] In one specific embodiment, the method of the present invention is used to degrade plastic products comprising at least one polyester, preferably at least PET or PLA.

[0126] Alternatively, the method of the present invention is used to degrade plastic products containing at least one polyamide selected from polyamide-6 or poly(β-caprolactam) or polyhexamethylene (PA6), polyamide-6,6 or poly(hexamethylene adipamide) (PA6,6), poly(11-aminoundecanoamide) (PA11), polydodecanoamide (PA12), poly(tetramethylene adipamide) (PA4,6), poly(pentamethylene decanamide) (PA5,10), poly(hexamethylene nonadiamide) (PA6,9), poly(hexamethylene decanamide) (PA6,10), poly(hexamethylene dodecanoamide) (PA6,12), poly(adipamide) (PAMXD6), polyhexamethylene adipamide / polyhexamethylene terephthalamide copolymer (PA66 / 6T), polyhexamethylene adipamide / polyhexamethylene terephthalamide copolymer (PA66 / 6I), and mixtures / mixtures of these materials.

[0127] Alternatively, the method of the present invention can be used to degrade plastic products containing at least one polyolefin selected from polyethylene, polypropylene, polymethylpentene, polybutene-1, polyisobutylene, ethylene propylene diene monomer rubber, ethylene vinyl alcohol, ethylene-carbon monoxide copolymers, and copolymers and their modifications.

[0128] In one specific embodiment, the plastic product comprises at least two different polymers. More generally, the plastic product to which the method of the present invention is intended may comprise different kinds of polymers, including synthetic polymers derived from petrochemicals such as polyamides, polyolefins, or vinyl polymers, or bio-based sources such as rubber, wood, or wood compounds such as lignin, cellulose, or hemicellulose, as well as starch and its derivatives. Alternatively, the plastic product may 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 their derivatives as defined in WO 2015 / 173265.

[0129] Interestingly, the method of the present invention allows for the production of monomers and / or oligomers and / or degradation products that can be further recycled and / or reprocessed.

[0130] Production of monomers / oligomers / degradation products

[0131] Another object of the present invention is to provide a method for producing monomers and / or oligomers and / or degradation products from a plastic product comprising at least one polymer, the method comprising subjecting the plastic product sequentially to a foaming step to at least partially foam the plastic product, optionally subjecting it to a cooling step to amorphize at least partially the polymer in the plastic product, and then subjecting it to a depolymerization step of the at least polymer in the plastic product.

[0132] Another object of the present invention is to provide a method for degrading a plastic product comprising at least one polymer, wherein the plastic product has been pre-foamed, the polymer of the plastic product has optionally been at least partially amorphized, and wherein the plastic product is contacted with a depolymerizing agent capable of degrading the polymer, preferably a biological agent, more preferably a depolymerizing enzyme. In one specific embodiment, the plastic product is depolymerized under composting conditions or under ambient conditions. In particular, the plastic product is subjected to industrial composting conditions at temperatures above 50°C, and / or home composting conditions at temperatures between 15°C and 35°C. In this case, the polymer of the plastic product may be degraded by microorganisms in the compost and / or environment into water and / or carbon dioxide and / or methane.

[0133] Another object of the present invention is to provide a method for degrading plastic products, the method further comprising the step of purifying monomers and / or oligomers and / or degradation products generated by the depolymerization step. The monomers and / or oligomers and / or degradation products generated by depolymerization 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 several different types of monomers and / or oligomers can be recovered. All suitable purification methods can be used to purify the recovered monomers and / or oligomers and / or degradation products in a form adjustable for repolymerization. In a preferred embodiment, the repolymerizable monomers and / or oligomers can then be reused to synthesize polymers. Those skilled in the art can readily adapt the process parameters to the monomers / oligomers and polymers for synthesis.

[0134] Another object of the present invention is to provide a method for recycling a plastic product comprising at least one polymer, the method comprising sequentially subjecting the at least one plastic product to a foaming step and a depolymerization step, and recovering monomers and / or oligomers of such polymer.

[0135] Another object of the present invention is to provide a method for degrading at least partially foamed plastic products comprising at least one polymer, wherein the at least partially foamed plastic product is generated from plastic waste and / or fiber waste and is contacted with a depolymerizing agent, preferably a biological agent, more preferably a depolymerizing enzyme, capable of degrading the at least one polymer. Specifically, the at least partially foamed plastic product is obtained from plastic waste and / or fiber waste that has previously undergone a foaming step. Specifically, the plastic waste and / or fiber waste has undergone a foaming step using a chemical foaming agent or a physical foaming agent, or both chemical and physical foaming agents. In one specific embodiment, the polymer in the at least partially foamed plastic product has been amorphized, and the at least partially foamed plastic product is contacted with a depolymerizing biological agent, preferably a depolymerizing enzyme, to degrade the amorphized polymer. The foaming and amorphization steps can be performed according to the specific embodiments disclosed above.

[0136] In particular, one object of the present invention is to provide a method for recycling plastic products selected from plastic waste and / or fiber waste and comprising at least one polymer, wherein the plastic waste and / or fiber waste has been pre-foamed, the method comprising the step of depolymerizing the at least partially foamed plastic product by contacting the product with a depolymerizing agent, preferably a biological agent, more preferably a depolymerizing enzyme capable of degrading the at least one polymer. In one embodiment, the plastic product selected from plastic waste and / or fiber waste has been pre-foamed according to a specific embodiment disclosed above. In particular, the plastic product has previously been pre-foamed using one or more chemical foaming agents or one or more physical foaming agents or both chemical and physical foaming agents. In a specific embodiment, the polymer of the plastic product has been pre-amorphized and then contacted with a depolymerizing agent, preferably with a biological agent, more preferably with a depolymerizing enzyme capable of degrading the amorphized polymer. In one embodiment, the plastic product selected from plastic waste and / or fiber waste has been pre-amorphized according to a specific embodiment disclosed above.

[0137] Therefore, one object of the present invention is to use a foamed plastic product comprising at least one polymer, and to subject such a foamed plastic product to a depolymerization step to produce monomers and / or oligomers of such polymer. Preferably, the foamed plastic product comprises plastic waste and / or fiber waste that has been pre-foamed and whose polymer has optionally been pre-amorphized.

[0138] All specific embodiments disclosed above relating to methods for degrading plastic products also apply to methods for producing monomers and / or oligomers, as well as recycling methods.

[0139] Production of biodegradable plastics

[0140] Another object of the present invention is to provide a plastic product comprising at least one target polymer and incorporating at least one enzyme capable of degrading said target polymer, wherein said enzyme has been incorporated into the plastic product according to the following method:

[0141] a. The plastic product is at least partially foamed with a foaming agent preferably selected from chemical foaming agents, wherein the foaming step is carried out at a temperature higher than the Tc of the target polymer, preferably higher than the Tm of the target polymer;

[0142] b. Less than 30 seconds after the foaming step, the at least partially foamed plastic product is cooled by subjecting it to a liquid containing a depolymerizing agent (i.e., an enzyme capable of degrading the target polymer) at a temperature below the Tc and / or Tg of the target polymer.

[0143] Other aspects and advantages of the invention will be disclosed in the following embodiments, which are to be considered illustrative and not limiting of the scope of this application. These embodiments provide experimental data supporting the invention and methods for carrying out the invention.

[0144] Example

[0145] Example 1 – A method for degrading plastic products containing PET, including a foaming step using a chemical foaming agent.

[0146] A) The foaming step using a chemical foaming agent (CFA) and the subsequent cooling step

[0147] a. Use Clariant's HYDROCEROL PEX 5048 as the CFA.

[0148] The Leistritz ZSE 18MAXX twin-screw extruder is used to foam washed and colored flakes of bottle waste containing 98% PET with an average crystallinity of 34.5%. The extruder includes nine consecutive heating zones (Z1-Z9) and one heating head (Z10), where the temperature can be independently controlled and regulated in each zone.

[0149] The sheet is introduced into the main hopper (before Z1). HYDROCEROL PEX5048, a chemical foaming agent from Clariant, is introduced into Z4 using a weight feeder. A total flow rate of 3 kg / h is achieved, resulting in an extruded composition (S1) containing 4% CFA based on the total weight of the composition. The screw speed is set to 200 rpm.

[0150] b. Using citric acid as CFA

[0151] A milled and washed colored sheet containing 98% PET with an average crystallinity of 34.5% was dry-blended with 1% by weight of citric acid in powder form (Orgater exp 141 / 183 from Adeka). Based on the total weight of the composition, an extruded foamed composition (S1 BIS) was obtained. The screw speed was set to 110 rpm and the total flow rate was set to 4 kg / h.

[0152] The screw temperature distribution used to prepare samples S1 and S1 BIS is shown in Table 1.

[0153] Table 1: Temperature distribution of the extruder used for samples named S1 and S1 BIS

[0154]

[0155] The molten polymer reaches the screw head (Z10), which includes a die plate with a 3.5 mm orifice, and is immediately immersed in a 2 m long cold water bath (10 °C). The resulting extrudate is granulated into 2-3 mm solid granules with crystallinity levels of 0% and 1% (samples S1 and S1 BIS).

[0156] Porosity ε of each sample T Calculate using the following equation:

[0157] in:

[0158] - It is the apparent density measured using a water hydrometer.

[0159] - It is the true density measured on an unfoamed polymer.

[0160] The porosity ε of S1 T The figure was 33.6%, and the S1 BIS figure was 54.6%.

[0161] The water hydrometer is determined using 4 to 5 extrusions of 1 to 2 cm in length, as defined in the instruction manual, corresponding to 1 to 2 grams of material.

[0162] Under the same conditions as S1, without using a foaming agent, the control sample "Control-1" was extruded and granulated. The porosity ε of Control-1... T The crystallinity level is 0. The control group (-1) has a crystallinity level of 15%.

[0163] A second control sample, "Control-2" (in fine powder form), with a crystallinity level of 15% was prepared by immersing the granules of Control-1 in liquid nitrogen and micronizing the granules using a RETSCH ZM200 Ultra-Centrifugal Mill equipped with a 500 μm grid. Only powders with a size smaller than 500 μm obtained by sieving were used in the depolymerization step.

[0164] B) Depolymerization steps of foamed plastic products

[0165] The depolymerization process was carried out in a 500 ml microbioreactor (Global Process Concept, France) using a variant of LC-keratinase (Sulaiman et al., Appl Environ Microbiol. March 2012). This variant of the enzyme (LCC-ICCIG), corresponding to SEQ ID N°1 with the following mutations F208I+D203C+S248C+V170I+Y92G, was expressed as a recombinant protein in Trichoderma reesei.

[0166] 100 mg of LC-keratinase variant, prepared in 224 ml of 100 mM potassium phosphate buffer (pH 8), was combined with 56 g of PET sample. The temperature was adjusted to 60 °C, and constant stirring at 250 rpm was constrained using a marine turbine. The pH was adjusted to 8 using 6 NNaOH, and C-BIO was applied via a GX controller. TM The software (Global Process Concept, France) controls the process and records the amount of NaOH consumed during the process.

[0167] The depolymerization rate of PET was determined by periodic sampling. Samples were analyzed by ultra-high performance liquid chromatography (UHPLC) to measure the amount of terephthalic acid equivalent produced according to the methods described herein.

[0168] AT equivalent concentrations were determined by unified high-performance liquid chromatography (UHPLC). If necessary, the sample was diluted in 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, autosampler, column maintained at 25 °C, and UV detector at 240 nm. Terephthalic acid (AT) and the resulting molecules (MHET and BHET) were separated using a methanol gradient (30% to 90%) in 1 mM H₂SO₄ at 1 m / min through an HPLC Discovery HS C18 column (150 mm x 4.6 mm, 5 μm) equipped with a pre-column (Supelco, Bellefonte, PA). AT, MHET, and BHET were measured using standard curves prepared from commercially available AT and BHET and internally synthesized MHET. The AT equivalent was the sum of the measured TA equivalents in MHET and BHET. The hydrolysis percentages of sample S2 and control 2 were calculated based on the total TA equivalents (TA + MHET + BHET) at a given time and the total TA measured in the initial sample. The depolymerization percentage results are shown in Table 2 below.

[0169] sample Percentage of disintegration at 12 hours (%) Control-1 2 Control-2 48 S1 60 S1 BIS 65

[0170] Table 2 : PET depolymerization rate of foamed plastic products containing PET (S1 and S1 BIS) compared with unfoamed extruded plastic products (Control-1) and unfoamed, extruded and micronized plastic products (Control-2).

[0171] The results first show that the foaming step can increase the depolymerization percentage of PET by 30 times compared to unfoamed plastic products. Furthermore, the results also show that the method of the present invention can suppress the micronization step, because foamed plastic products depolymerize faster than unfoamed, extruded, and micronized plastic compositions (Control-2).

[0172] Example 2 – A method for degrading plastic products containing PET, including a foaming step using a physical foaming agent.

[0173] A) The foaming step using carbon dioxide (CO2) and the subsequent cooling step

[0174] A single-screw extruder is used to foam washed and colored flakes from bottle waste containing 98% PET using supercritical CO2. This extruder (30mm diameter - SCAMEX, France) includes six heating zones (T), each with an independently controllable and regulated temperature.

[0175] -T1 and T2: Regions before CO2 injection

[0176] -T3 and T4: Regions after CO2 injection

[0177] -T5: Mixing zone, including the static mixer, and

[0178] -T6: Mold, which includes a mold plate. The opening of the mold plate can be adjusted according to the outlet pressure, with a maximum opening of 3mm.

[0179] The temperatures for T1 to T3 are fixed at 180℃, 280℃, and 260℃ respectively, and the temperatures for T4 to T6 are listed in Table 3 below. The screw speed is fixed at 40 rpm.

[0180] The pressure in the final section of the mixing zone (T5) was measured by a pressure sensor and is shown in Table 3 (P4). CO2 was pressurized and injected at a constant flow rate using an injection pump (Isco 260D, USA) between T2 and T3. The pressure, temperature, and volume input of CO2 (Q) were recorded. CO2 The measurements were taken in the pump and are shown in Table 3.

[0181] The obtained extrudate was immediately immersed in fresh water at approximately 15°C, and then cut into small pieces of 2-3 mm using a grinder. The obtained samples were then dried under ambient conditions for 48 hours before analysis.

[0182] Other experimental conditions used for sample preparation, as well as porosity and crystallinity results, are shown in Table 3 below. Qp is the polymer flow rate determined by weighing the sample. CO2 This is the volumetric flow rate of injected CO2. CO2 is relative to the total flow rate (w / v). CO2The mass flow rate was calculated using the density obtained through the Span and Wagner equation of state (R. Span et W. Wagner, A new equation of state for carbon dioxide covering the fluid region from the triple-point temperature to 1100 K at pressures up to 800 MPa. Journal of Physical and Chemical Reference Data, vol. 25(6), pp. 1509–1596, 1996). Tmat was the material temperature measured at the extruder outlet.

[0183]

[0184] Table 3 Experimental conditions and porosity and crystallinity results for preparing foamed plastic products using physical foaming agents.

[0185] B) Foaming step using nitrogen (N2) and subsequent cooling step

[0186] The extrusion foaming step was performed using a single-screw extruder (45 mm diameter, FAIREX), which included a melt cooler, a static mixer, and a vertical die with a nominal diameter of 2 mm. Supercritical N2 was introduced using a PROMIX injection gas system. The extrudate was cooled using a 2 m long cold water bath (9°C) and then granulated using a rotary cutter to obtain 1.5 mm long pellets. The distance between the die exit and the water surface was approximately 5.5 cm.

[0187] Washed and colored flakes from bottle waste containing 95% PET (43% crystallinity) were dried at 80°C. The set temperatures and recorded material parameters are shown in Tables 4 and 5, respectively.

[0188] The screw speed was set to 25 rpm. The total material flow rate was 6 kg / h, and the injected nitrogen flow rate was 15 g / h. The obtained granules S6 were then dried at ambient temperature for 48 hours prior to analysis.

[0189]

[0190] Table 4 A set of temperatures in the extruder

[0191]

[0192] Table 5 Material parameters recorded at the screw tip and the outlet of the static mixer.

[0193] The obtained sample S6 The assessed value was 461.7 kg / m³. 3 This gives a porosity of 66%. Its crystallinity level was assessed as 14%.

[0194] C) Depolymerization steps

[0195] The same secretory recombinant LCC-ICCIG enzyme as in Example 1 was used for the depolymerization of subsequent samples S2 to S6 and Control-1 (as produced in Example 1). For each sample from S2 to S6 and Control-1, 100 mg was weighed and introduced into a 250 mL glass vial containing 49 mL of 0.1 M potassium phosphate buffer (pH 8). Depolymerization was initiated by incubating each sample in Multitron pro (InforsHT, Switzerland) at 60 °C and 150 rpm, followed by the addition of 1 mL of 0.1 mg / mL enzyme solution to 0.1 M potassium phosphate (pH 8).

[0196] The depolymerization rate of PET was determined by periodic sampling, and the amount of terephthalic acid equivalent produced according to the method described in Example 1 was measured by ultra-high performance liquid chromatography (UHPLC). The hydrolysis percentages of samples S2 to S6 and Control-1 were calculated based on the total amount of TA equivalent (TA + MHET + BHET) at a given time and the total amount of TA determined in the initial sample. The results of the depolymerization percentages are shown in Table 6 below.

[0197] sample Percentage of depolymerization at 28h (%) Control-1 6.0 S2 32.9 S3 46.5 S4 39.8 S5 20.5 S6 49.1

[0198] Table 6 : Depolymerization rate of PET in foamed plastic products containing PET (S2 ​​to S6) compared to unfoamed plastic products (control-1).

[0199] Plastic products containing PET that are pre-foamed using physical foaming agents (carbon dioxide or nitrogen (azote)) have a degradation process that is 3 to 8 times faster than unfoamed plastic products.

[0200] Example 3 – A method for degrading plastic products containing PET, comprising a foaming step using a physical foaming agent and a cooling step in a bath containing an enzyme solution.

[0201] A) The foaming process using supercritical CO2 and the subsequent cooling process

[0202] According to Example 2-A, supercritical CO2 was used to foam washed and colored flakes from bottle waste containing 98% PET.

[0203] Prepare two samples, S7 and S8, according to the instructions detailed in Table 7. Immerse the extrudate in water (S7) or in an enzyme bath containing approximately 4.3 g / L of the same secretory recombinant LCC-ICCIG enzyme as in Example 1 (S8). Rinse the obtained extrudate with water, dry it under ambient conditions, and then slice it into 2-3 mm pieces using a knife grinder.

[0204] The experimental conditions used for sample preparation and the porosity and crystallinity results are shown in Table 7 below:

[0205]

[0206] Table 7 Experimental conditions used to prepare foamed plastic products, and results on porosity and crystallinity.

[0207] B) Depolymerization steps

[0208] As detailed in Example 2-B, depolymerization was performed on S7 and S8 in glass vials, the difference being that S8 was tested without the addition of enzymes in the buffer solution. The depolymerization results are shown in Table 8.

[0209] sample Percentage of depolymerization at 30 hours (%) S7 75 S8 85

[0210] Table 8 The PET depolymerization rate of the foamed plastic product containing PET that undergoes keratinase during the depolymerization step (S7) is compared with that of the foamed plastic product containing PET that undergoes keratinase during the cooling step, without the addition of keratinase during the depolymerization step (S8).

[0211] Compared to plastic products that are only in contact with depolymerase during the depolymerization step, PET-containing plastic products that have already undergone depolymerization during the cooling step show a slightly increased degradation process.

[0212] Example 4 – A method for degrading PLA-containing plastic products, comprising a foaming step using a chemical foaming agent and a cooling step in a bath containing an enzyme solution.

[0213] A) Use Foaming steps of chemical foaming agents

[0214] Polylactic acid (PLA) 4043D (granular form - 35% crystallinity supplied by NatureWorks) was foamed using a Leistritz ZSE 18 MAXX twin-screw extruder. It comprises nine consecutive heating zones (Z1-Z9) and one heating head (Z10), with the temperature of each zone independently controllable and adjustable. HYDROCEROL BIH 40 masterbatch, a chemical foaming agent (CFA) supplied by Clariant, was used.

[0215] PLA and CFA were dried in dryers at 60°C and 45°C for 14 hours, respectively. 95% by weight of PLA pellets and 5% by weight of CFA masterbatch were dry-mixed and added to the hopper of the weight feeder for introduction into the extruder. The resulting total flow rate was 2 kg / h. The temperature distribution along the entire screw is described in Table 9. The screw speed was set to 100 rpm.

[0216]

[0217] Table 9: Temperature distribution of the extruder used for sample S9

[0218] The molten polymer reaches the screw head (Z10), which includes a die plate with a 3.5 mm orifice. The resulting extrudate is immediately immersed in 1 L of a commercially available enzyme solution from Novozymes. The sample was placed in a 16L container (known to degrade PLA) at 15°C, then manually pulled and wound. After 24 hours, the sample was washed with water and dried under ambient conditions (20°C and 40% humidity) for 48 hours. The sample was then granulated into 2-3 mm solid granules with a crystallinity of 2% using a rotary cutter (S9). As a control, another sample (S10) was foamed in the same manner, except that the resulting extrudate was immersed in enzyme-free water. Both S9 and S10 exhibited a crystallinity of 2% and porosities of 30% and 40%, respectively.

[0219] B) Depolymerization steps

[0220] Each alloy was weighed in doses of 100 mg and introduced into a cellulose dialysis tube. The latter was then introduced into a glass vial containing 50 mL of Tris 100 mM buffer at pH 9.5 and incubated at 45 °C and 150 rpm.

[0221] The percentage degradation of the alloy was determined by UHPLC according to the following protocol. 1 mL samples were collected periodically. After filtration through a 0.22 μm filter, the samples were loaded into a UHPLC system (Ultimate 3000 UHPLC system (Thermo Fisher Scientific, Inc., Waltham, MA, USA), including a pump module, autosampler, column oven at 50 °C, and UV detector at 210 nm) to monitor the release of lactic acid and lactic acid dimer. Lactic acid and lactic acid dimer were separated using an Aminex HPX-87H column and a mobile phase of 5 mM H₂SO₄ at a flow rate of 0.5 mL / min. Sample injection was 20 μL. Lactic acid (LA) and lactic acid dimer (DP₂) were measured according to a standard curve prepared from commercial lactic acid (Sigma-Aldrich L1750-10G) and an internally synthesized lactic acid dimer under the same conditions as the sample.

[0222] The percentage of degradation is calculated based on the following molar ratio: LA plus the LA contained in DP2 at a given time and the theoretical LA initially contained in PLA.

[0223] After 24 hours, the degradation rate of S9 was 76%, while S10 showed no significant degradation. The results indicate that some enzymes were immobilized in the cell structure of the PLA-containing foamed plastic material during the cooling phase.

[0224] Example 5 – A method for degrading textile products containing PET, including a foaming step using a chemical foaming agent.

[0225] A) Foaming steps for textile products containing PET

[0226] Textile waste (old clothes) containing PET is sorted, shredded, cleaned to remove metal and hard contaminants (such as zippers or buttons) and compacted to obtain textile particles of 2-4 mm in size, containing 85% PET by weight.

[0227] Foam granules were prepared from the PET textile particles using the same extruder, cooling, and granulation equipment as in Example 1.

[0228] The compacted textile particles are introduced into the main hopper (before Z1). Citric acid (Orgater exp141 / 183 from Adeka) is used as the CFA and introduced into Z4 using a weight feeder. The screw speed is set to 110 rpm. A total flow rate of 4 kg / h is obtained, resulting in the extruded composition (S11) containing 1% by weight of citric acid based on the total weight of the composition.

[0229] The control sample from the used clothing composition "Control-3" was extruded, cooled, and granulated without the use of a foaming agent, and then micronized after immersion in liquid nitrogen to obtain a powder with a crystallinity level of 13%. The set temperature distribution for extrusion is given in Table 10. The screw speed was set to 200 rpm, and the total flow rate was set to 4 kg / h.

[0230] A woven fabric containing 100% PET was shredded and compacted, then dry-mixed with 1 wt% citric acid and 0.5 wt% water based on the total weight of the mixture before extrusion foaming. The same extruder as samples S11 and Control-3 was used. The dry mix was introduced through a gravimeter in the main hopper (before Z1). A total flow rate of 2.5 kg / h was achieved, resulting in the extruded composition (S12) containing 1 wt% citric acid based on the total weight of the composition. The screw speed was set to 150 rpm.

[0231] The temperature distribution along the screw for samples S11, S12, and control-3 is shown in Table 10 below.

[0232]

[0233] Table 10 Temperature distribution of the extruders used for samples S11, S12 and control-3

[0234] The crystallinity levels of S11 and S12 were 13% and 0%, respectively, and the porosities were 25% and 36%, respectively (true density was measured on extruded but unfoamed textile compositions).

[0235] B) Depolymerization steps of foamed textile products

[0236] The depolymerization step was performed under the same conditions as in Example 1-B.

[0237] The obtained depolymerization percentages are summarized in Table 11 below.

[0238] sample Percentage of depolymerization at 44 hours (%) S11 89 S12 90 Control-3 85

[0239] Table 11: PET depolymerization rate of foamed textile products containing PET (S11 and S12) compared with unfoamed, extruded and micronized textiles (control-3).

[0240] The results show that the method of the present invention allows for the omission of the micronization step, because the foamed textile product depolymerizes as much as the unfoamed, extruded and micronized textile composition (Control-3).

[0241] Example 6 – A method for degrading plastic products containing PET, comprising a foaming step using a chemical foaming agent and a depolymerization step using a chemical depolymerizing agent.

[0242] A) Preparation of foamed plastic products

[0243] In the above embodiment, the following materials were used

[0244] • Sample S1 BIS, which corresponds to a milled, washed, and colored sheet foamed with citric acid, as described in Example 1-A)b).

[0245] • Sample Control-1, corresponding to extruded and granulated but unfoamed flakes (see Example 1)

[0246] • Control-2 was obtained by micronizing the thin film of Control-1 (see Example 1).

[0247] • Control-4 corresponds to Control-1 and has undergone annealing in an oven at 120°C for 48 hours to allow the granules to recrystallize. The crystallinity level of Control-4 is approximately 32.2%.

[0248] • Control-5 was obtained by micronizing the granules of Control-4 (using the method described in Example 1).

[0249] B) Chemical depolymerization of foamed plastic products

[0250] Chemical depolymerization was performed in a 15 mL glass tube (Supelco, 27162) with a screw cap. ~40–50 mg of PET sample was placed in the glass tube, and a total of 800 μL of DCM and 400 μL of methanol / KOH (3M) were added. The mixture was stirred magnetically for 5 minutes at room temperature (RT–25 °C). The solvent was evaporated under a nitrogen stream for 10 minutes. The PET monomer was dissolved in 14 mL of milliQ water. The solution was stirred at room temperature for 5 minutes. The amount of monoethylene glycol (MEG) produced was determined by ultra-high performance liquid chromatography (UHPLC) according to the method described herein.

[0251] MEG concentration was determined by mixing 1.5 mL of sample with 0.5 mL of H₂SO₄. 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, autosampler, column maintained at 55 °C, and RI detector. MEG molecules were separated by an HPLC Aminex HPX-87H ion exclusion column (300 mm x 7.8 mm, 9 μm) equipped with a pre-column (Supelco, Bellefonte, PA). MEG was eluted with 5 mM H₂SO₄ at a flow rate of 0.8 mL / min. -1MEG was measured using a standard curve prepared from commercially available MEG. The reaction rate was calculated based on the total amount of MEG at a given time and the total amount of MEG determined in the initial sample. The results of the reaction rates and the crystallinity level for each sample are shown in Table 12 below.

[0252]

[0253] Table 12: Chemical depolymerization rates of PET in foamed plastic products containing PET (S1-BIS) compared to the following: unfoamed and extruded products (Control-1), unfoamed, extruded and micronized products (Control-2), recrystallized granules (Control-4), and recrystallized and micronized products (Control-5). Chemical reaction rates are expressed in mg / min.

[0254] The results show that foamed plastic products depolymerize faster than unfoamed plastic products, and faster than annealed (recrystallized) granules with or without micronization. The results also indicate that the method of the present invention allows for the omission of the micronization step, since the foamed product depolymerizes as much as the unfoamed, extruded, and micronized products.

Claims

1. A method for degrading a plastic product comprising at least one polymer, the method comprising the following steps: a. Foaming the plastic product at least partially, wherein the foaming step is carried out using a chemical foaming agent; and b. Depolymerizing at least one target polymer of the at least partially foamed plastic product by contacting the plastic product with a biodepolymerizing agent; The foaming step is carried out at a temperature when the plastic product is in a partially or completely molten state, and The method further includes the step of cooling the at least partially foamed plastic product less than 30 seconds after the foaming step.

2. The method of claim 1, wherein the foaming step is performed at a temperature higher than the crystallization temperature (Tc) of the target polymer.

3. The method according to claim 1, wherein the chemical foaming agent is selected from citric acid, carbonate, bicarbonate or a mixture thereof, or a mixture of citric acid and bicarbonate.

4. The method of claim 1, wherein the at least partially foamed plastic product exhibits a porosity of more than 20%.

5. The method of claim 1, wherein the step of cooling the at least partially foamed plastic product is carried out by subjecting the plastic product to a temperature below the crystallization temperature (Tc) of the target polymer.

6. The method of claim 1, wherein the polymer exhibits a crystallinity of up to 30% after the cooling step.

7. The method of claim 1, wherein the at least partially foamed plastic product undergoes a granulation step between the cooling step and the depolymerization step.

8. The method of claim 1, wherein the foaming step is performed in an extruder or in an autoclave.

9. The method of claim 1, wherein the biodepolymerizing agent is selected from depolymerizing enzymes, depolymerizing enzymes capable of degrading at least one polymer of the plastic product, and depolymerizing enzymes capable of degrading at least the target polymer of the plastic product.

10. The method of claim 1, wherein the foaming step is carried out with a chemical foaming agent, and the biodepolymerizing agent is a depolymerizing enzyme capable of degrading at least the target polymer of the plastic product.

11. The method of claim 1, wherein the plastic product comprises at least one thermoplastic polymer selected from polyesters and / or polyamides and / or polyolefins, and wherein the polyester is selected from polyethylene terephthalate (PET), polypropylene terephthalate (PTT), polybutylene terephthalate (PBT), polyisosorbate terephthalate (PEIT), polylactic acid (PLA), polyhydroxyalkanoate (PHA), polybutylene succinate (PBS), and polybutylene adipate. Poly(butylene adipate) (PBSA), poly(butylene terephthalate) (PBAT), polyethylene furanate (PEF), polycaprolactone (PCL), poly(ethylene adipate) (PEA), poly(butylene terephthalate) (PBST), poly(ethylene succinate) (PES), poly(butylene succinate / terephthalate / butylene isophthalate)-co-(lactic acid ester) (PBSTIL) and blends / mixtures of these materials; wherein the polyamide is selected from polyamide-6 or poly(β-caprolactone) Poly(hexamethylene adipamide) or poly(PA6), polyamide-6,6 or poly(hexamethylene adipamide) (PA6,6), poly(11-aminoundecylamide) (PA11), polydodecanolactam (PA12), poly(tetramethylene adipamide) (PA4,6), poly(pentamethylene decanamide) (PA5,10), poly(hexamethylene nonadiamide) (PA6,9), poly(hexamethylene decanamide) (PA6,10), poly(hexamethylene dodecylamide) (PA6,12), poly(hexamethylene adipamide) (PA6,12), poly(hexamethylene adipamide) (PA6,9), poly(hexamethylene decanamide) (PA6,10), poly(hexamethylene dodecylamide) (PA6,12), poly(hexamethylene adipamide) (PA6,12), poly(hexamethylene adipamide) (PA6,6 ... The polyolefin is selected from polyethylene, polypropylene, polymethylpentene, polybutene-1, polyisobutylene, ethylene propylene diene monomer rubber, ethylene vinyl alcohol, ethylene-carbon monoxide copolymer, and copolymers thereof.

12. A method for degrading plastic products containing at least PET, the method comprising the steps of: a. The plastic product is at least partially foamed using a chemical foaming agent, wherein the foaming step is performed at a temperature above 170°C; b. Cool the at least partially foamed plastic product at a temperature below 100°C for less than 30 seconds after the foaming step; c. Depolymerizing the cooled plastic product (PET) by contacting it with a biodepolymerizing agent; and optionally... The oligomers and / or monomers resulting from the depolymerization of the PET are recovered and optionally purified.

13. The method of claim 12, wherein the chemical foaming agent is selected from citrates, carbonates, bicarbonates and mixtures thereof.

14. The method of claim 12, wherein the at least partially foamed plastic product undergoes a granulation step between the cooling step and the depolymerization step.

15. The method of claim 12, wherein the biodepolymerizing agent is a depolymerase or an esterase.

16. A method for producing monomers and / or oligomers and / or degradation products from a plastic product comprising at least one polymer, the method comprising subjecting the plastic product sequentially to a foaming step, a cooling step for less than 30 seconds after the foaming step, and a depolymerization step, wherein the foaming step is carried out using a chemical foaming agent, and the depolymerization step is performed by exposing the foamed plastic product to a depolymerizing enzyme.

17. A method for degrading at least partially foamed plastic products comprising at least one polymer, wherein the at least partially foamed plastic product is contacted with a biodepolymerizing agent capable of degrading at least one polymer of the plastic product, and wherein the at least partially foamed plastic product is obtained from plastic waste and / or fiber waste that has previously undergone a foaming step and a cooling step of less than 30 seconds after the foaming step, wherein the foaming step is carried out using a chemical foaming agent.

18. The method of claim 17, wherein the polymer of the at least partially foamed plastic product has been pre-amorphized before contact with the depolymerizing agent.

19. A method for recycling a plastic product comprising at least one polymer selected from plastic waste and / or fiber waste, the method comprising the step of depolymerizing at least one target polymer of the plastic product by contacting the plastic product with a biodepolymerizing agent, wherein the plastic product has previously been at least partially foamed and is cooled in less than 30 seconds after the foaming step, wherein the foaming step is carried out using a chemical foaming agent.

20. The method of claim 19, wherein the polymer of the plastic product has been pre-amorphized.

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