Method for processing polymer-containing materials

Abstract

The invention relates to a method for treating a material comprising a polymer, said method comprising the following steps:-providing a raw material comprising a polymer, said polymer being a polyester derived from an aliphatic polyol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms, the invention relates to a method for producing a polyester, comprising the steps of:-in a step of depolymerizing an aliphatic polyol comprising at least 70 wt.% of a polyol having at least 3 hydroxyl groups, an aliphatic polycarboxylic acid comprising at least 70 wt.% of a tricarboxylic acid, said polyester having a degree of polymerization of at least 0.7, said degree of polymerization being the ratio of the fraction of reacted functional groups to the maximum value of reactive functional groups,-in a step of depolymerizing the aliphatic polyol, the aliphatic polycarboxylic acid comprising at least 70 wt.% of a polyol having at least 3 hydroxyl groups, the aliphatic polycarboxylic acid comprising at least 70 wt.% of a tricarboxylic acid; contacting the raw material at a temperature of at least 80 DEG C with a nucleophilic agent comprising at least one of water, a liquid polymer, and at least one of water and a liquid polymer for at most 24 hours to effect depolymerization of the polymer, resulting in a polymer having a degree of polymerization reduced by at least 0.1 and in the range of 0.1-0.8, to obtain a polymer having a degree of polymerization reduced by at least 0.1 and in the range of 0.1-0.8. The liquid polymer is a polymerization product of an aliphatic polyol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms. It has been found that the method according to the invention makes it possible to reduce the molecular weight of the polymer in an effective and cost-effective manner, while providing materials that can be applied in various manners in the industry.

Description

[0001] The present invention relates to a method for processing polymer-containing materials, in particular materials containing renewable and degradable polyester polymers based on polyols and polycarboxylic acids, more particularly polyester polymers based on aliphatic polyols having 2 to 15 carbon atoms and aliphatic polycarboxylic acids having 2 to 15 carbon atoms.

[0002] Such polymers have been described in the art for a large number of widely varying applications.

[0003] WO2012140237 describes a composite material comprising 10-98 wt.% of a bio-based particulate or fibrous filler and at least 2 wt.% of a polyester derived from an aliphatic polyol having 2-15 carbon atoms and a polycarboxylic acid, wherein the polycarboxylic acid comprises at least 10 wt.% of a tricarboxylic acid. In particular, the filler may be selected from wood chips, wood chips, sawdust, pulp (e.g., (recycled) paper pulp or other fiber pulp), and plant-derived fibers (e.g., cotton, hemp, flax, and hemp).

[0004] WO2012140239 describes a composite material comprising the same polymer material as the composite material of WO2012140237, but in this case using a synthetic filler, preferably selected from one or more of ceramic (including glass, in particular glass fibers), polymer (in particular polymer fibers) and carbon (in particular carbon fibers).

[0005] WO2012052385 describes the same polymer in foam form.

[0006] The references cited above describe polyesters obtained by polymerizing a polyol having at least three hydroxyl groups (particularly glycerol) with a polycarboxylic acid having at least three carboxylic acid groups (particularly glycerol). The use of these monomers, particularly at high degrees of polymerization, results in the formation of thermosetting materials with high strength and durability, making them suitable for use in products such as furniture, building and construction materials (for both indoor and outdoor use), and other applications requiring elasticity. Examples of compositions of this type are described in WO20220106724 and the non-prepublished WO2022214552.

[0007] As the renewability and recyclability of materials become increasingly important, there is a need in the art for a method for recycling polymer-containing materials. It would be particularly advantageous if the material could be converted into something that can be reused in the manufacture of high-value materials in an efficient manner. The present invention provides such a method.

[0008] The present invention relates to a method for treating a polymer-containing material, said method comprising the following steps:

[0009] - providing a starting material comprising a polymer, said polymer being a polyester derived from an aliphatic polyol having 2 to 15 carbon atoms, said aliphatic polyol comprising at least 70 wt.% of a polyol having at least 3 hydroxyl groups, and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms, said aliphatic polyol comprising at least 70 wt.% of a tricarboxylic acid, said polyester having a degree of polymerization of at least 0.7, said degree of polymerization being the ratio of the fraction of reacted functional groups to the maximum number of reactable functional groups,

[0010] - in the depolymerization step, the raw material is contacted with a nucleophilic reagent at a temperature of at least 80° C. for up to 24 hours to achieve depolymerization of the polymer to obtain a polymer having a degree of polymerization that is at least 0.1 lower than the degree of polymerization of the polymer in the raw material and within the range of 0.1-0.8, wherein the nucleophilic reagent comprises at least one of water and a liquid polymer, wherein the liquid polymer is a polymerization product of an aliphatic polyol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms.

[0011] It has been found that the process according to the invention makes it possible to reduce the molecular weight of polymers in an efficient and cost-effective manner, while providing materials that can be used in various ways in industry. In particular, the polymers recovered from the process can be reused in the manufacture of new polymeric materials while maintaining good product quality.

[0012] The present invention enables cradle-to-cradle processing of thermosetting polymers used with a high degree of polymerization of at least 0.7, but particularly at least 0.8, or at least 0.9, or at least 0.95. The method according to the present invention enables the conversion of thermosetting polymers into materials with a lower degree of polymerization, which can be used as raw materials for the production of new materials, including new thermosetting materials. This is in contrast to conventionally used thermosetting polymer materials, which cannot be readily converted into repolymerizable products with high efficiency while maintaining product quality.

[0013] A particular advantage of the process of the present invention is that the nucleophile used therein is a compound that does not interfere with the repolymerization step. If water is used, it is removed in the repolymerization step along with the water produced in the esterification step. If a specific liquid polyester or its monomer is used, it is incorporated into the newly formed polymer. If the composition of the polymer or monomer used as the nucleophile matches that of the polymer being depolymerized, the composition of the final product is not altered at all. This is in contrast to the nucleophiles used in many prior art depolymerization methods.

[0014] The present invention, its specific embodiments and its associated advantages are discussed in more detail below.

[0015] raw materials

[0016] The first step of the method according to the present invention is to provide a raw material comprising a polymer which is a polymerization product of an aliphatic polyol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms, the polymer in the raw material having a degree of polymerization of at least 0.55.

[0017] In the context of the present invention, the degree of polymerization of a polymer is defined as the ratio of the fraction of functional groups that have reacted to the maximum number of functional groups that can react. The degree of polymerization can be determined by the acid number method (particularly for values of degree of polymerization below 0.5) or by gravimetric analysis (particularly for values of degree of polymerization above 0.5).

[0018] It is obvious that in order to determine the degree of polymerization of a polymer derived from an aliphatic polyol and an aliphatic polycarboxylic acid with an unknown degree of polymerization using gravimetric analysis, a sample of the polymer with an unknown degree of polymerization is cured at a temperature of 100 to 220° C. until no more water is lost. The degree of polymerization of the polymer is then 1, allowing the degree of polymerization of the sampled polymer to be back-calculated using the water lost during curing.

[0019] The polymer

[0020] The polymer is a polyester derived from an aliphatic polyol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms.

[0021] Suitable polyol monomers for use in the present invention include aliphatic polyols having 2-15 carbon atoms. The aliphatic polyol does not contain any aromatic moieties, nitrogen atoms, or sulfur atoms. In some embodiments, the aliphatic polyol is composed of carbon, oxygen, and hydrogen atoms. The aliphatic polyol contains at least two hydroxyl groups, preferably at least three hydroxyl groups. Typically, the number of hydroxyl groups will be 10 or less, preferably 8 or less, more preferably 6 or less. The aliphatic polyol has 2 to 15 carbon atoms, preferably 3 to 10 carbon atoms. Examples of suitable aliphatic polyols are 1,2-propylene glycol, 1,3-propylene glycol, 1,2-ethylene glycol, 1,4-butylene glycol, glycerol, sorbitol, xylitol, and mannitol. Glycerol, sorbitol, xylitol, and mannitol are preferred examples of suitable aliphatic polyols. Glycerol is the most preferred example of suitable aliphatic polyols. One reason for this is that glycerol has a melting point of 20°C, which makes processing easier (compared to, for example, xylitol, sorbitol, and mannitol, which all have melting points above 90°C). Furthermore, glycerol is readily available and produces polymers with desirable properties. Thus, in some embodiments, the aliphatic polyol consists essentially of glycerol. As used herein, "consisting essentially of" means that other components (here: other aliphatic polyols) may be present in amounts that do not adversely affect the properties of the material.

[0022] The aliphatic polyol comprises at least 70 wt.% of a polyol with at least 3 hydroxyls, particularly at least 80 wt.%, more preferably at least 90 wt.%, most preferably 95 wt.%, calculated based on the total amount of the aliphatic polyol. In some embodiments, the aliphatic polyol is essentially composed of a polyol with at least 3 hydroxyls. Preferably, the polyol with at least 3 hydroxyls is composed of at least 70 wt.% of glycerol, particularly at least 80 wt.%, more particularly at least 90 wt.% or at least 95 wt.%. A mixture of different aliphatic polyols can also be used. The aliphatic polyol can comprise at least 50 mol% of glycerol, sorbitol, xylitol or mannitol, preferably at least 70 mol%, preferably at least 90 mol%. Preferably, the remainder is an aliphatic polyol with 3 to 10 carbon atoms. The polyol preferably comprises at least 70 mol% of glycerol, preferably at least 90 mol%, more preferably at least 95 mol%.

[0023] In some embodiments, the ratio of the number of hydroxyl groups to the number of carbon atoms of the aliphatic polyol is from 1:4 (i.e., one hydroxyl group for every four carbon atoms) to 1:1 (i.e., one hydroxyl group for every carbon atom). The ratio of the number of hydroxyl groups to the number of carbon atoms is preferably from 1:3 to 1:1, more preferably from 1:2 to 1:1, and even more preferably from 1:1.5 to 1:1. Compounds wherein the ratio of hydroxyl groups to carbon atoms is 1:1 are considered particularly preferred.

[0024] Suitable polycarboxylic acid monomers for use in the present invention include aliphatic polycarboxylic acids having 2 to 15 carbon atoms, preferably 3 to 10 carbon atoms, in some embodiments 3 to 6 carbon atoms. The aliphatic polycarboxylic acid does not comprise an aromatic moiety or any nitrogen or sulphur atom. In some embodiments, the aliphatic polycarboxylic acid is made up of carbon, oxygen and hydrogen atoms. The aliphatic polycarboxylic acid comprises at least two carboxylic acid groups, preferably three carboxylic acid groups. Typically, the number of the carboxylic acid groups will be 10 or still less, preferably 8 or still less, more preferably 6 or still less.

[0025] The aliphatic polycarboxylic acid comprises at least 70 wt.% tricarboxylic acid calculated based on the total amount of the aliphatic polycarboxylic acid. The aliphatic polycarboxylic acid may comprise at least 80 wt.% tricarboxylic acid, more preferably at least 90 wt.%, most preferably 95 wt.%. In some embodiments, the aliphatic polycarboxylic acid consists essentially of tricarboxylic acids, preferably consists essentially of citric acid.

[0026] The aliphatic polycarboxylic acid can be a mixture of acids, such as a mixture of tricarboxylic acids and dicarboxylic acids. In some embodiments, the aliphatic polycarboxylic acid comprises a combination of 2-30 wt.%, preferably 5-30 wt.%, in some embodiments 10-30 wt.% of a dicarboxylic acid and at least 70 wt.%, more preferably at least 80 wt.% of a tricarboxylic acid, calculated based on the total amount of the aliphatic polycarboxylic acid.

[0027] If a dicarboxylic acid is used, it can be any dicarboxylic acid having two carboxylic acid groups and typically having up to 15 carbon atoms. Examples of suitable dicarboxylic acids include itaconic acid, malic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, oxalic acid, maleic acid, fumaric acid, muconic acid, suberic acid, and azelaic acid. Itaconic acid, succinic acid, maleic acid, and fumaric acid may be preferred.

[0028] The tricarboxylic acid can be any tricarboxylic acid having three carboxylic acid groups and typically up to 15 carbon atoms. Examples include citric acid, isocitric acid, aconitic acid (cis and trans), and 3-carboxy-cis, cis-muconic acid. For reasons of cost and availability, the use of citric acid is considered preferred. Where applicable, the acid can also be provided in the form of its anhydride, such as citric anhydride. In one embodiment, the tricarboxylic acid is composed of at least 70 wt.% citric acid, particularly at least 80 wt.%, more particularly at least 90 wt.%, and even more particularly at least 95 wt.%.

[0029] In one embodiment, the polymer is a polyester derived from an aliphatic polyol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms, wherein the aliphatic polyol comprises at least 70 wt.% of a polyol having at least 3 hydroxyl groups, more preferably at least 80 wt.%, still more preferably at least 90 wt.%, most preferably 95 wt.%, the aliphatic polyol having at least 3 hydroxyl groups is preferably glycerol, and the aliphatic polycarboxylic acid comprises at least 70 wt.% of a tricarboxylic acid, calculated based on the total amount of acid, preferably at least 80 wt.%, more preferably at least 90 wt.%, most preferably 95 wt.%, the tricarboxylic acid is preferably citric acid.

[0030] In one embodiment of the present invention, the polymer is derived from a combination of polyol monomers and polycarboxylic acid monomers.

[0031] The polyol monomer is preferably selected from aliphatic polyols having 2 to 15 carbon atoms and at least three hydroxyl groups, such as glycerol, sorbitol, xylitol and mannitol, especially glycerol.

[0032] The polycarboxylic acid monomer is selected from aliphatic polycarboxylic acids having 3 to 15 carbon atoms and having at least three carboxylic acid groups, such as citric acid, isocitric acid, aconitic acid (cis and trans), and 3-carboxy-cis, cis-muconic acid, in particular citric acid.

[0033] In the present invention, it is preferred that the ratio between the total number of hydroxyl groups and the total number of carboxyl groups in the system is in the range of 2:1 to 0.5:1, in particular 1.5:1 to 0.6:1, more particularly 1.25:1 to 0.8:1, and even more particularly 1.1:1 to 0.9:1. If the polyol and polycarboxylic acid are composed entirely of triols and triacids, respectively, this translates into a molar ratio of these compounds in the range of 2:1 to 0.5:1, in particular 1.5:1 to 0.6:1, more particularly 1.25:1 to 0.8:1, and even more particularly 1.1:1 to 0.9:1. If polyols or polyacids having different numbers of hydroxyl and carboxyl groups are used, this should be taken into account when determining the relative amounts of the compounds to be used.

[0034] It is considered advantageous to have the ratio between the total number of hydroxyl groups and the total number of carboxyl groups in the system within a specified range, as this allows for the highest possible conversion to be achieved. Achieving high conversion is considered advantageous because a limited number of hydroxyl or acid functional groups will remain. These groups are hygroscopic in nature and may have a negative impact on the suitability of the product for demanding applications requiring product durability.

[0035] As mentioned above, the starting polymer has a degree of polymerization of at least 0.7. Polymers with a degree of polymerization within this range can be obtained by polymerization of a combination of polyol monomers and polycarboxylic acid monomers. Typically, in the first step, a mixture of monomers in a liquid phase can be prepared. Depending on the nature of the compound, this can be accomplished, for example, by heating the mixture of components to a temperature at which the acid will dissolve in the alcohol, particularly glycerol. Depending on the nature of the compound, this can be accomplished, for example, at a temperature of 20-250°C, such as 40-200°C, such as 60-200°C or 90-200°C. In one embodiment, the mixture can be heated and mixed at a temperature of 80-200°C, particularly 100-200°C, in some embodiments 120-180°C, for a period of 1 minute to 2 hours, more specifically 5 minutes to 45 minutes. If desired, a suitable solvent, such as water, can be present.

[0036] Preferably, the amount of water will be kept limited, since its evaporation is energy consuming. It may be preferred to add up to 30 wt.% of water, in particular up to 20 wt.% of water.

[0037] Optionally, a suitable catalyst can be used to prepare the polyester. Suitable catalysts for making polyesters are known in the art. Preferred catalysts are those that do not contain heavy metals. Both basic catalysts and acidic catalysts can be used. Both homogeneous catalysts and heterogeneous catalysts (e.g., based on zeolites, modified hydrotalcites, or based on resins (e.g., ion exchange resins or Nafion)) can be used. Useful acidic catalysts include, but are not limited to, hydrochloric acid, hydroiodic acid (also expressed as hydroiodic acid) and hydrobromic acid, sulfuric acid (H2SO4), nitric acid (HNO3), chloric acid (HClO3), boric acid, sodium hypophosphite, perchloric acid (HClO4), trifluoroacetic acid, p-toluenesulfonic acid, sulfonic acid, and trifluoromethanesulfonic acid. Catalysts such as tetrabutyl titanate, tin octoate, zinc acetate, and manganese acetate can also be used, but they may be less preferred.

[0038] The monomer mixture is subjected to a heating step to obtain a degree of polymerization of at least 0.55, in particular at least 0.6. Typically, the mixture will be cured at an internal temperature of 80 to 250° C., in particular 220° C., for example for 5 seconds to 24 hours. The curing step is generally carried out at an internal temperature of at least 80° C., in particular at least 100° C., more in particular at least 120° C., even more in particular at least 130° C. Very high internal temperatures lead to increased side reactions. Therefore, it is preferred that the internal temperature does not exceed 250° C. The internal temperature may preferably be in the range of 130-220° C., in particular 130-200° C. The internal temperature is measured during curing or immediately after removing the article from the device for curing, such as an oven or a press.

[0039] Curing can be carried out using heating techniques known in the art, for example in an oven at an oven temperature of 80°C to 450°C. Different types of ovens can be used, including but not limited to belt ovens, convection ovens, microwave ovens, infrared ovens, hot air ovens, conventional baking ovens and combinations thereof. Vacuum ovens are also considered attractive. Curing can also be carried out by high-frequency heating. Curing can be completed in a single step or in multiple steps. The curing time is 5 seconds to 24 hours, depending on the size and shape of the object, the target internal temperature and the heating system applied. When microwave heating or high-frequency heating is applied, a curing time of 10 seconds to 30 minutes is generally sufficient. When a conventional oven is used, the total curing time is preferably at least 10 minutes, particularly at least 20 minutes, and at most 12 hours, particularly at most 6 hours.

[0040] Although a long curing time is not disadvantageous in itself, it may be less attractive from an economic point of view. It is within the scope of those skilled in the art to select suitable curing conditions. If necessary, curing can be carried out in one step or in multiple steps. When applying more than one step, the curing temperature of the second step will usually be higher than the curing temperature used in the first step.

[0041] filler

[0042] The raw materials in the process of the present invention may or may not contain fillers.

[0043] Various types of fillers are contemplated. In general, particulate, fibrous, and / or lamellar fillers of natural or synthetic origin may be used. Combinations of various filler materials may be used. The filler may be present in an amount of 10-95 wt.%, particularly 20-80 wt.%, and more particularly 40-70 wt.%, based on the total weight of the composite object.

[0044] An example of a suitable filler is a particulate material. In the context of this specification, a particulate material is a material having an aspect ratio in the range of 10:1 to 1:1, preferably in the range of 8:1 to 1:1, more preferably in the range of 6:1 to 1:1. As used herein, "aspect ratio" is defined as the ratio of the length of the particle determined along its longest axis to the maximum diameter of the particle determined along an axis perpendicular to the longest axis.

[0045] The granular material may have a maximum length, determined along the longest axis of the particles in the material, of less than 20 mm, more preferably at most 15 mm, more preferably at most 10 mm, particularly at most 5 mm, and particularly at most 2 mm. As a minimum, an average length of the particles of 0.001 mm may be mentioned. In some embodiments, the average length of the particles is at least 0.05 mm, particularly at least 0.1 mm, and more particularly at least 0.5 mm. In some embodiments, the average length of the particles is in the range of 0.5-5 mm, particularly 0.5-2 mm.

[0046] Suitable particulate material can be the form of for example powder, dust, slurry, chopped fiber, thin slice or fragment.Example comprises wood chips, wood chips, sawdust, hemp bits, (dry) grass and slurry, for example the slurry of (regeneration) paper or other fiber slurries from beet, fruit and vegetables etc.The example of the material of plant origin that can be used as particulate material is cotton, flax, hemp, grass, reed, bamboo, coconut, Miscanthus, coffee grounds, seed shell (for example from rice), hessian, kenaf, ramie, sisal etc. and the material derived therefrom.Usually, can use the plant material that has been crushed into suitable particle size and dried to suitable water content when necessary.

[0047] Particulate material can comprise natural material, for example, material derived from plant or animal.The example of plant-based material comprises cellulose-based material, for example fresh or used paper, fresh or used cardboard, any form of wood or other plant material and its combination.Cellulose-based material can be derived from the so-called raw pulp obtained directly from the wood pulping process.This pulp can be from any plant material, but mainly obtains from wood.Wood pulp comes from softwood trees, for example spruce, pine, fir, larch and hemlock, and hardwood trees, for example eucalyptus, poplar, aspen and birch.Additionally or alternatively, cellulose-based material can comprise cellulose material derived from recycled paper, for example cellulose pulp obtained from recycled books, paper, newspapers and periodicals, egg trays and other recycled paper or cardboard products.Also can use the combination of cellulose sources.Other attractive sources of cellulose-based material are waste paper fibers, which are paper fibers that are too short to be suitable for making paper, and any (mechanical and / or chemical) regeneration materials from any (composite) material, for example, recycled furniture made of cellulose-based material.Especially, (composite) materials made with the polymers mentioned herein as adhesives are attractive sources of cellulose-based material. The use of these (recycled) materials is highly sustainable and low-cost, allowing for widespread use in, for example, furniture manufacturing.

[0048] Examples of materials of animal origin include feathers, down, hair and its derivatives such as wool, and also bone meal.

[0049] Other examples of suitable particulate materials include ceramic materials, including oxides, such as aluminum oxide, beryllium oxide, cerium oxide, zirconium oxide, silicon dioxide, titanium dioxide and mixtures and combinations thereof, and non-oxides, such as carbides, borides, nitrides, silicides and mixtures and combinations thereof, such as silicon carbide. For the purposes of this specification, glass is considered to be a ceramic material. Glass can, for example, be used in the form of short fibers, glass beads (whether solid or hollow) and ground glass particles. Suitable particulate materials also include materials such as mica fillers, calcium carbonate and minerals (such as layered silicates). Clay, sand, talc, gypsum etc. can also be used.

[0050] Suitable particulate materials also include polymer fillers, such as particles or short fibers of polyethylene, polypropylene, polystyrene, polyesters (e.g., polyethylene terephthalate), polyvinyl chloride, polyamides (e.g., nylon-6, nylon 6.6, etc.), polyacrylamide, and aramid polymers (e.g., aromatic polyamide). Suitable particulate materials also include carbon fibers and carbon particulate materials. Crushed cured polyester resins, such as those used in the present invention, can also be used as particulate materials. Crushed cured polyester resins containing fillers can also be used.

[0051] In some embodiments, a particulate material comprising one or more organic particulate materials is used, for example selected from wood chips, sawdust, wood chips and recycled paper. In other embodiments, the particulate material (also) comprises one or more inorganic particulate materials, for example selected from (recycled) glass, stone, ceramic, minerals and metals.

[0052] Suitable fillers also include fibrous materials. In the context of this specification, a fibrous material is a material having an aspect ratio greater than 10:1.

[0053] In the context of this specification, the word "fiber" refers to monofilaments, multifilament yarns, threads, tapes, strips and other elongated objects having a regular or irregular cross-section and a length that is much greater than the width and thickness.

[0054] Suitable fibrous materials can, for example, have a fiber length measured on its longest axis of at least 1 cm, preferably at least 3 cm, preferably at least 4 cm. For example, the fibrous material can have a fiber length measured on its longest axis of 1-20 cm. Preferably, the fibrous material has a fiber length of 1-10 cm. Longer fibers are preferred because these fibers provide strength to the composition.

[0055] The fibrous material may comprise fibers having a diameter of 0.001 to 10 mm, preferably 0.01 to 1 mm, and more preferably 10 to 500 μm. Thinner fibers are advantageous for many applications because their use results in a smooth surface. The fibers may, for example, have an aspect ratio of 20:1 to 200,000:1, preferably 200:1 to 20,000:1, and more preferably 250:1 to 5000:1. Using fibers with a relatively large aspect ratio facilitates a combination of high strength and a smooth surface.

[0056] The fibers useful as fillers of the present invention can be oriented in a random (eg, nonwoven sheet) or non-random manner. The fibrous material is preferably a nonwoven sheet.

[0057] In the context of this specification, "oriented in a non-random manner" refers to all structures in which the fibers are oriented in a substantially regular manner relative to each other. Examples of layers containing fibers oriented in a non-random manner include woven layers, knitted layers, layers in which the fibers are oriented in parallel, and any other layer in which the fibers are connected to each other in a repeating pattern.

[0058] The orientation of fibers in a fibrous material can, for example, affect the strength of the final product. Thus, in some cases, it may be preferable to orient the fibers in a manner that maximizes the strength of the article. In some embodiments, at least 50% of the fibers are oriented parallel, preferably at least 60% of the fibers are oriented parallel, and more preferably at least 70% of the fibers are oriented parallel. In other cases, greater anisotropic properties or biaxial resistance may be desired.

[0059] The fibrous material that can be used for the present invention can comprise the fiber of plant origin, preferably cellulose and / or lignocellulosic fiber.The fibrous material can also be basically composed of the fiber of plant origin.The example of the fiber based on plant origin fiber includes flax, hemp, kenaf, jute, ramie, sisal, coconut, bamboo and cotton.The fibrous material can also comprise the fiber of animal origin.The fiber of animal origin can be wool, hair, silk and the fiber derived from feather (for example chicken feather).Also can use other parts of internal organs.The fibrous material can comprise synthetic fiber.The example of suitable synthetic fiber is the fiber derived from viscose, glass, polyester, carbon, aramid, nylon, acrylic, polyolefin etc.The fibrous material can also be the mixture of the fiber of different sources, for example the mixture of the fiber of plant origin and synthetic fiber.

[0060] In the context of this specification, the composition of filler and polymer also includes a composition in which the filler is provided in the form of a thin layer alternately stacked with polymer layers. Suitable layered materials generally comprise at least 2, particularly at least 4, up to 50, particularly up to 20 filler layers. The thickness of a single filler layer is generally 0.1-10mm, particularly 0.1-5mm, more particularly 0.2-2mm. The total thickness of the object can be, for example, 0.5-200mm. The thickness of the polymer layer can be, for example, 10-4000 micron, particularly 10-2000 micron, more particularly 10-500 micron. Suitable filler can be, for example, timber (also referred to as wood facing). Plywood is an example of this embodiment. Other layered fillers, for example paper or cardboard, can also be applied.

[0061] As will be appreciated by those skilled in the art, combinations of different types and materials may also be used as fillers.

[0062] The raw material used in the present invention may also be filler-free. In this case, in one embodiment, it is a polymer foam.

[0063] In the raw materials, the degree of polymerization of the polymer is at least 0.7. Typically, the raw materials are solid at room temperature. The specific feature of the inventive method is that it allows processing of solid raw materials. The degree of polymerization of the polymer in the raw materials can be higher, for example, at least 0.8, at least 0.9 or at least 0.95. The present invention is characterized in that the method of the present invention is also applicable to raw materials with a high degree of polymerization. This is surprising because these materials are stable and resistant to degradation.

[0064] Disaggregation step

[0065] In the process of the present invention, a depolymerization step is carried out wherein the raw material is contacted with a nucleophile comprising at least one of water, a liquid polymer and a monomer of said polymer at a temperature of at least 60° C., the liquid polymer being a polymerization product of an aliphatic polyol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms, to effect depolymerization of the polymer and reduce the degree of polymerization of the polymer in the raw material by at least 0.1 to a value in the range of 0.1-0.8.

[0066] During the depolymerization step, a nucleophile is used, which is chosen from water, a liquid polymer, and a monomer of said polymer, said liquid polymer being the polymerization product of an aliphatic polyol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms. The choice of this particular group of nucleophiles ensures that no "new" compounds have to be added to the system.

[0067] The liquid polymer is of the same type as the polymer in the raw material, and the monomers used are of the same type as the monomers of the polymer in the raw material. Preferably, the liquid polymer has the same chemical composition as the polymer in the raw material, and similarly, preferably, the monomer mixture applied in the depolymerization step has the same composition as the monomers constituting the polymer in the raw material. In the context of this specification, the term "same chemical composition" is defined as follows: two polymers have the same chemical composition if they consist of at least 75% of the same monomers, in particular at least 80%, and more in particular at least 90%.

[0068] The depolymerization step is carried out at a temperature of at least 80°C. Higher temperatures will increase the reaction rate, but if the temperature becomes too high, side reactions may begin to occur. It may be preferred that the depolymerization step be carried out at a temperature of at least 90°C, and in some embodiments at least 100°C. As a maximum temperature, a value of 220°C may be mentioned. In the case of using a temperature of 100°C, a pressure above atmospheric pressure may be applied. The preferred temperature range may also depend on the nucleophile used, the desired reduction in the degree of polymerization, and other conditions. These parameters will be discussed in more detail below.

[0069] If desired, a catalyst may be present during the depolymerization reaction. Suitable catalysts include those described above as suitable for use in polyester production.

[0070] The depolymerization step is typically carried out for a period of time ranging from 1 minute to 24 hours, depending on the temperature, pressure, the nature and amount of the nucleophile, and the desired reduction in the degree of polymerization. For example, at elevated temperatures and superatmospheric pressure, a time range of the order of minutes may be sufficient, whereas these conditions may require longer processing times. Depolymerization times exceeding 24 hours are less attractive from an economic point of view and may also be associated with product degradation. It may be preferred that the depolymerization step be carried out for a period of up to 12 hours, in particular for a period of up to 8 hours, and more in particular for a period of up to 6 hours.

[0071] During the depolymerization step, the degree of polymerization of the polymer is reduced by at least 0.1. In certain cases, the desired degree of polymerization reduction depends on the degree of polymerization of the starting polymer and the desired further processing of the polymer. Depending on the degree of polymerization of the starting material and the desired product, the degree of polymerization of the polymer may be reduced by at least 0.2, in particular by at least 0.3, and more in particular by at least 0.4. The maximum reduction is 0.9.

[0072] After the depolymerization step, the degree of polymerization of the polymer is in the range of 0.1-0.8.

[0073] It has been found that carrying out the depolymerization reaction to a degree of polymerization below 0.1 is unattractive. This not only requires an additional investment in time and energy, but also means that, when the polymer is repolymerized to form a new product, additional water must be removed, as water is produced during the reaction of the alcohol groups with the carboxylic acid groups. At the other end of the spectrum, if the reduction in degree of polymerization is limited so that the final product still has a degree of polymerization of 0.8, the effectiveness of the process is generally insufficient to make the process commercially relevant. Preferably, the degree of polymerization of the polymer after the depolymerization step is in the range of 0.2-0.8.

[0074] In one embodiment, the degree of polymerization after the reaction is in the range of 0.1-0.6, particularly in the range of 0.2-0.5. This is the range in which the polymer is generally in the liquid phase (depending on the temperature) and allows for its separation from other components (e.g., filler materials), its combination with other materials, for example as an adhesive or binder, or for the reshaping of materials containing the polymer. These various aspects are discussed below. In another embodiment, the degree of polymerization of the product is in the range of 0.6-0.8. This range is particularly attractive for reshaping when it is desired to reshape existing filler-containing materials.

[0075] Water as a nucleophile

[0076] In one embodiment, the nucleophilic reagent used in the present invention comprises water. In this embodiment, a liquid polymer or a monomer of said polymer is used as the nucleophilic reagent. This embodiment will be discussed under the next heading. This paragraph relates to the use of nucleophilic reagents comprising water.

[0077] In the process of this embodiment, the raw materials are treated with water at a temperature of at least 60°C. Higher temperatures are preferred in order to increase the rate of depolymerization. Therefore, it is preferred that the process be carried out at a temperature of at least 80°C, in particular at least 100°C. It has been found that treatment with water at a temperature of at least 100°C leads to rapid depolymerization, to a controlled extent. As a maximum, a value of 220°C may be mentioned. Above this value, side reactions may increase. Moreover, temperatures above this range are less attractive from an energetic point of view. Preferred reaction temperatures are at least 110°C, in particular at least 120°C. Also preferred are temperatures of at most 200°C, in particular at most 180°C. In some embodiments, temperatures of at most 160°C are preferred.

[0078] When temperatures above 100° C. are used, the pressure during the treatment with water is preferably above 1 bar. A value of 25 bar can be given as a maximum. Above this value, the process becomes less attractive from an economic point of view. A pressure in the range of 1.5 to 15 bar, in particular in the range of 2 to 10 bar, and more particularly in the range of 3 to 8 bar, is particularly preferred.

[0079] In one embodiment, the reaction is carried out under autogenous pressure, ie, the pressure is determined by the temperature and the amount of water in the reaction vessel.

[0080] Depending on the temperature and pressure selected, water will be present in the gaseous phase. Furthermore, depending on the amount of water, temperature, and pressure, liquid water may also be present. It has been found that the presence of liquid water can increase the rate of depolymerization. On the other hand, the presence of too much water can lead to an undesirable degree of depolymerization. Furthermore, if the depolymerization product is intended to be repolymerized, it may be desirable to limit the degree of depolymerization by limiting the water content. The presence of excess water may also affect product homogeneity. Therefore, it may be preferable to have an upper limit on the total amount of water present during the depolymerization reaction. On the other hand, since the presence of water is required for an efficient depolymerization reaction, a minimum amount is also preferred.

[0081] Thus, in one embodiment, the amount of water provided for the depolymerization reaction is in the range of 5 to 60 wt.%, specifically 5 to 40 wt.%, in some embodiments 10-30 wt.%, calculated based on the amount of polymer provided to the depolymerization reaction.

[0082] As a general comment, while it is possible to control the degree of polymerization of the final product by the amount of water, it may be more attractive to control the degree of polymerization of the final product by the duration of the depolymerization reaction.

[0083] In case the raw material comprises a water absorbing material (e.g. a porous hydrophilic filler), it may be necessary to add additional water to compensate for water that may be absorbed by the filler. An example would be where the raw material comprises wood chips as a filler.

[0084] Liquid polymer or monomer of said polymer as nucleophile

[0085] In one embodiment of the invention, the raw material is contacted with a nucleophile comprising a liquid polymer, the liquid polymer being a polymerized product of an aliphatic polyol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms. Additionally or alternatively, the raw material is contacted with a nucleophile comprising a monomer of the polymer, i.e., a monomer selected from the group consisting of an aliphatic polyol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms and combinations thereof. The above-mentioned preferences for the composition of the raw material also apply here, with the difference that the amount of the polyol having at least three hydroxy groups and the amount of the tricarboxylic acid are not required for the nucleating agent.

[0086] When a nucleophile comprising one or more polymers or monomers is used, the nucleophile will be a liquid medium. The temperature of the liquid medium is typically in the range of 80-220°C, preferably in the range of 80-160°C.

[0087] The degree of polymerisation of the product obtained by this process is generally between 0.1 and 0.7, in particular between 0.2 and 0.6, more particularly between 0.2 and 0.5.

[0088] When a liquid polymer or its monomers are used as the nucleophile, some water may be present. In this embodiment, the polymer to be depolymerized is substantially dissolved in the liquid polymer / monomer. The amount of water in the liquid mixture is typically at most 40 wt.%, particularly at most 30 wt.%, and more particularly at most 20 wt.%, of the total amount of the liquid mixture. The presence of a small amount of water is preferred, as any water will be removed further in the process.

[0089] In this embodiment, the amount of liquid medium should be sufficient to decompose the polymer into the liquid medium. Thus, in one embodiment, the volume of the liquid medium is at least 50% by volume of the volume of the polymer to be depolymerized therein. Because excess volume is undesirable, it is preferred that the volume of the liquid medium is at most 500% by volume of the volume of the polymer to be depolymerized therein.

[0090] This embodiment is particularly attractive for the depolymerization of raw materials which consist in large part, for example, of at least 90 wt.% of a specific polyester polymer, in particular at least 95 wt.%, more in particular at least 98 wt.% or at least 99 wt.%.

[0091] Selection of raw materials and methods

[0092] The method for treating polymer-containing materials according to the present invention can be applied to raw materials containing fillers, but also to raw materials without fillers. Examples of various types of raw materials will be discussed below.

[0093] In one embodiment, the raw material used in the process according to the invention is a polymer-containing material, the majority of which consists, for example, of at least 90 wt.% of a specific polyester polymer, in particular at least 95 wt.%, more particularly at least 98 wt.% or at least 99 wt.%. In this case, the process according to the invention can be used, for example, to convert the polymer into a liquid phase, which typically has a degree of polymerization in the range of 0.1 to 0.6, in particular 0.2-0.5. Higher degrees of polymerization are also possible.

[0094] In the case where the raw materials contain solid components (further indicated as fillers), there will be various options, depending on the nature of the filler, the relative amounts of polymer and filler, and the intended further use of the various compounds, etc. In one embodiment, the polymer will be converted into a liquid phase, which typically has a degree of polymerization in the range of 0.1 to 0.6, preferably 0.2 to 0.5, and a separation step is performed to separate the liquid product polymer from the filler. The liquid product and the filler (which will typically still contain some polymer) are then processed separately.

[0095] In another embodiment, the filler and polymer are not separated after the depolymerization step. In this case, the product of the depolymerization step comprises a polymer with a reduced degree of polymerization and filler, and the product can be directly processed in this form to form new objects. In this case, the desired degree of polymerization after the depolymerization step can be higher, for example, at least 0.2, or at least 0.3, or at least 0.4. The general ranges provided above will still apply to this embodiment.

[0096] Depending on the nature of the raw material and the intended further processing, the raw material may be subjected to a size reduction step before being supplied to the depolymerization step. When the supplied material has a smaller size, the contact surface with water or water vapor will be greater, thereby increasing the reaction rate. On the other hand, particularly when the filler has a relatively large particle size or is fibrous in nature and its properties are to be reused, it is important not to affect the filler's properties by reducing the particle size to an excessive degree. In other embodiments, size reduction will be performed only to a limited extent, or not at all, for example, when the depolymerization step is followed by a reshaping step. Size reduction after the depolymerization step may also be attractive, as the depolymerization of the polymer will soften the material, making size reduction easier to perform. Of course, size reduction can also be performed between the two depolymerization steps.

[0097] In some embodiments, a shaping step may be performed. In the context of this specification, a shaping step is any step in which a material comprising depolymerized polymer and filler is subjected to a step in which its shape is altered. This can be done, for example, by bending, folding, flattening, or in any other way changing the shape of the object as a whole, but it can also be achieved by combining materials and forming a new shape. Changing the shape of an existing object after depolymerization may also be referred to herein as reshaping.

[0098] In some embodiments, the object comprising the depolymerized polymer undergoes a curing step to increase the degree of polymerization, for example, to a value of at least 0.7, at least 0.8, or at least 0.9. Immediately after curing, the object typically has a water content of less than 10 wt.% (calculated based on the total weight of the layered structure), preferably less than 5 wt.%, more preferably less than 2 wt.%, and most preferably less than 1 wt.%. Depending on storage conditions, the water content of the object may increase after curing. For further information on the curing step, reference is made to the description of curing in the context of the raw materials.

[0099] Hereinafter, various specific embodiments of the method according to the present invention will be described, but the present invention is not limited thereto or thereby. Aspects of different embodiments can be combined, and further embodiments will be apparent to the skilled person.

[0100] Processing of polymer-containing materials without fillers

[0101] In one embodiment, the polymer-containing material contains no filler. In this embodiment, the polymer-containing material is typically a solid polymer material, the majority of which consists, for example, of at least 90 wt.% polymer, particularly at least 95 wt.% polymer, for example in the form of a foam. In this case, the process of the present invention is typically used to convert the polymer into a liquid phase, which typically has a degree of polymerization in the range of 0.2 to 0.6, particularly 0.2 to 0.5.

[0102] It may be preferred to provide the filler-free solid polymer material to the process according to the invention in granular form, for example in the form of granules having a maximum particle diameter of 10 cm (i.e., 90% of the particles have a diameter below this value). Compared to larger granular materials, the reduction in size leads to an increased reaction rate because the contact area between water and / or water vapor and the solid polymer material increases. Furthermore, the distance required for water vapor to reach the core of the polymer-containing material is reduced. It may be preferred that the material be in granular form with a maximum particle diameter of 6 cm, particularly 4 cm, more particularly 2 cm, and in some embodiments, up to 5 mm. Grinding may also be employed.

[0103] If the polymer-containing material does not contain fillers, it may be preferred to carry out the process in such a way that the product of the depolymerization reaction is a liquid product, to allow for efficient removal from the depolymerization reactor. In one embodiment, if it is desired to produce a liquid product, the degree of polymerization after the depolymerization step is in the range of 0.1 to 0.6, particularly 0.2 to 0.5. More general ranges also apply to this embodiment. It may be particularly preferred to use a nucleophile comprising a liquid polymer.

[0104] If a liquid polymer is used as nucleophile, it may be preferred to incorporate at least 40 wt. % of the starting material into the nucleophile to ensure optimal use of the reactor volume.

[0105] The product from the depolymerization reaction can be treated as desired. It can optionally be subjected to one or more purification steps, such as a filtration step to remove residual solid particles, or a purification step using activated carbon to remove contaminants that cause color or odor. Excess water can also be removed if desired.

[0106] Processing and reshaping of filled and polymeric materials

[0107] In one embodiment, the method is intended to reshape an existing product. In this case, the raw material is a polymer-containing material containing a polymer and a filler. The polymer-containing material typically contains 10-70 wt.% polymer and 30-90 wt.% filler.

[0108] In this embodiment, the shaped object of the polymer-containing material is subjected to a depolymerization step, followed by a shaping step and a curing step.

[0109] In this case, the degree of polymerization after the depolymerization reaction is generally higher than 0.2, in particular higher than 0.3, more in particular higher than 0.5.

[0110] After the depolymerization reaction, the resulting product is flexible. A force is applied to the product to change its shape, followed by a curing step. The curing step is typically performed while maintaining the product in its new shape (e.g., by using a mold or press).

[0111] In this embodiment, it is preferred that the nucleophile employed in the depolymerization step is water vapor.

[0112] Processing of filler-containing polymer-containing materials - Separation of polymers

[0113] In one embodiment, the method of the present invention is intended to reclaim polymers from a polymer-containing material containing a filler. When the polymer-containing material has a high polymer content and / or when the polymer does not strongly adhere to the filler, the method may be particularly attractive. For example, non-porous fillers such as glass particles or fibers, carbon particles or fibers, or polymer fillers (such as fillers based on aramid) are generally easier to separate from polymers than porous natural fibers (such as hemp). Separability will also depend on other properties of the filler.

[0114] In this embodiment, the process according to the invention comprises the step of subjecting the filler-containing polymer-containing material to a depolymerization step, followed by the step of separating the depolymerized polymer from the filler.

[0115] In one embodiment, the degree of polymerization after the reaction is generally 0.2 to 0.6, particularly 0.2-0.5. At this point, the polymer is generally in the liquid phase (depending on the temperature) and allows it to be separated from the filler. The presence of liquid water will help reduce the viscosity of the polymer medium, and this can improve the separation process.

[0116] The separation step can be carried out by methods known to those skilled in the art, such as by filtration or decantation. If necessary, squeezing and / or washing can be applied to remove additional material from the filler. The polymer thus recovered can be used to manufacture new polymer-containing products. The filler from which the polymer has been separated can also be processed as desired.

[0117] Producing new granular raw materials

[0118] In one embodiment, the method according to the invention is used to produce new particulate raw materials from existing products. In this embodiment, the method according to the invention comprises the steps of providing a filler-containing polymer-containing material in particulate form and subjecting the material to a deagglomeration step, resulting in the formation of filler-containing polymer-containing particles.

[0119] In this embodiment, the degree of polymerization after the depolymerization reaction is typically greater than 0.3, particularly greater than 0.5. The polymer-containing material typically contains 10-70 wt.% polymer and 30-90 wt.% filler. In this embodiment, the use of water / water vapor as the nucleophile is considered preferred. The particles can be reused to manufacture new products, for example by combining them with one or more additional polymers or additional filler materials and subjecting the mixture to a forming step or a curing step, for example, as described in WO2022106724.

[0120] Reuse of obtained products

[0121] The method of the present invention produces a polymer that is a polymerization product of an aliphatic polyol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms, the polymer having a degree of polymerization of 0.1 to 0.8. The resulting product may or may not contain a filler and, depending on the degree of polymerization and the presence or absence of a filler, may be in a liquid phase. The product of the method of the present invention can be used as a raw material for manufacturing new products. They can, for example, be mixed with a filler. Suitable fillers are described above in the context of the raw materials. Suitable manufacturing and curing conditions are also described above in the context of the raw materials.

[0122] In addition, reference may be made to the products and methods described in WO2012052385, WO2012140238, WO2012140239, WO2012140237, WO2013121033, WO2020152082, WO2020212427, WO2021023495, WO2021105143, WO2022043330, and WO2022106724.

[0123] Unless otherwise indicated, all percentages used herein are by weight.

[0124] As will be apparent to those skilled in the art, different embodiments of the present invention can be combined unless they are mutually exclusive. The headings used in this specification are intended only to improve readability and have no legal consequences. Therefore, unless embodiments discussed under different headings are mutually exclusive, they can be combined.

[0125] When amounts, concentrations, sizes and other parameters are expressed in the form of ranges, preferred ranges, upper limits, lower limits or preferred upper and lower limits, it is to be understood that any range obtained by combining any upper limit or preferred value with any lower limit or preferred value is also specifically disclosed, regardless of whether the obtained range is explicitly mentioned in the context.

[0126] The following examples illustrate the practice of the present invention in some preferred embodiments. The present invention is not limited thereto or thereby. Example

[0127] Example 1: Depolymerization and Recycling of Foam

[0128] A glycerol / citric acid (1:1 molar ratio) foam having a degree of polymerization (DP) of 0.9 or greater and a density of approximately 250 g / l is provided. The foam is provided in the form of blocks having a maximum diameter of 2 cm. The blocks are placed in an autoclave, where they are contacted with water vapor at a temperature of 150° C. (approximately 5 bar) for a period of 2 hours. During the depolymerization reaction, the foam depolymerizes to form a liquid polymer having a DP of approximately 0.2. Upon completion of the depolymerization reaction, the liquid polymer composition is removed from the reactor.

[0129] The liquid polymer (resin) can be used to prepare new foams or used as a binder in the same way as fresh resin without loss of functionality (see Example 6).

[0130] Example 2: Granular material board from depolymerized hemp fiber compressed board

[0131] A compressed sheet comprising a non-woven hemp fiber mat and 50 wt.% of a citric acid / glycerol polymer having a degree of polymerization greater than 0.8 (molar ratio 1:1) was subjected to a size reduction step resulting in the formation of particles having an average diameter of less than 4 mm. The particles were placed in a depolymerization reactor where they were contacted with water vapor at a temperature of 120° C. (about 2 bar) for 2 hours.

[0132] The product of the depolymerization step is a particulate material which still contains polymer. The degree of polymerisation of the polymer is about 0.3.

[0133] The resulting granules were dried at 85°C for 2 hours and then compressed at 15 bar pressure and 145°C for 10 minutes to form a compressed board containing hemp particles with a thickness of 8 mm. The board was then cured at 160°C for 2 hours. The degree of polymerization of the polymer in the compressed board was at least 0.8. The resulting board was smooth and had good physical properties, including a flexural strength of 25 MPa, which is much higher than the value of commercially available particleboard.

[0134] Example 3: Reuse of depolymerized hemp fiber-curved boards as flat hemp fiber boards

[0135] A compression bend (90°) board comprising hemp fiber and 50 wt.% of a citric acid / glycerol polymer (molar ratio 1:1) having a degree of polymerization greater than 0.8 is provided. The board was previously a chair and had a density of 1.1 g / ml.

[0136] The sheet is fed to a depolymerization reactor where it is exposed to water vapor at a temperature of approximately 120°C (approximately 2 bar) for 4 hours. After the depolymerization reaction is complete, the previously rigid sheet is now flexible. The degree of polymerization of the polymer is approximately 0.4. The sheet is dried at 80°C for 3 hours. It is then processed by flattening it in a press and curing it at 145°C and a pressure of 15 bar for 2 hours to form a smooth, rigid, flat sheet of polymer with a degree of polymerization greater than 0.8 and good mechanical properties.

[0137] Example 4: Recycling of fiberglass panels

[0138] A composite panel is provided comprising a stack of five woven glass fiber mats and a citric acid / glycerol polymer (molar ratio 1:1) having a degree of polymerization greater than 0.9.

[0139] The panel was provided to a depolymerization reactor where it was contacted with water at a temperature of 150° C. for 1 hour (about 6 bar). After the depolymerization reaction was complete, the degree of polymerization of the polymer was about 0.3.

[0140] The liquid polymer was separated from the glass fiber mat by filtration to recover the liquid polymer and the glass fibers. The recycled glass fiber mats (which were tactilely and visually identical to new mats) were reused in the manufacture of new glass fiber composite panels by combining them with recycled resin (in an amount of 40-60 wt.%) and subjecting the composite to a curing step at 160°C. The cured polymer had a degree of polymerization higher than 0.8. Although the values of the mechanical properties were slightly reduced compared to the original panels, good mechanical properties were obtained, with tensile strength, flexural strength and flexural elongation being of the order of 70% of the original values. Without wishing to be bound by theory, it is believed that this may be due to the removal of the sizing agent during the depolymerization process. In any case, this example shows that panels with good properties can be manufactured from depolymerized resin and recycled glass fibers.

[0141] Example 5: Depolymerization of foam in liquid resin and reuse as binder in hemp fiberboard

[0142] A glycerol / citric acid (molar ratio 1:1) foam having a degree of polymerization greater than 0.9 and a density of about 250 g / l is provided. The foam is provided in the form of blocks with a maximum diameter of 2 cm.

[0143] The lumps were fed to a depolymerization reactor where they were contacted with a liquid glycerol / citric acid (1:1 molar ratio) polymer resin having a degree of polymerization of about 0.5 and a water content of 10 wt.%. A mixture was prepared using 50 / 50 wt.% foam particles / liquid polymer resin and some additional water (equal to the amount of water in the liquid resin). The mixture was reacted for 4 hours at reflux and a reaction temperature of about 130°C. At the end of the reaction, a liquid polymer medium was obtained with an estimated degree of polymerization of about 0.5. It was found that further resin foam could be readily dissolved / depolymerized in the liquid medium obtained.

[0144] The resin thus obtained was used to manufacture panels by impregnating hemp mats with the resin and then curing under pressure, according to WO 2022106724. The properties of the panels were found to be the same as those of panels based on fresh resin.

[0145] Example 6: Recycled particleboard panels

[0146] Panels made from wood particles and a citric acid / glycerol polymer (1:1 molar ratio) with a degree of polymerization greater than 0.8 were provided (a typical particleboard composition with small particles on the outside and larger particles on the inside, about 15 wt.% polymer in total).

[0147] The panels were fed to a depolymerization reactor where they were contacted with water vapor at a temperature of about 120° C. (about 2 bar) for 6 hours.

[0148] The panel was soft, swollen, and the particles with the resin were loose. The particles were further loosened with a kitchen blender and dried in an oven at 85°C for 2 hours.

[0149] The particles were separated into smaller and larger particles using a sieve. A new board was made from the recycled particles by providing a layer of larger particles sandwiched between two layers of smaller particles and curing the composite material under pressure at 145°C and 15 bar for two hours. This resulted in a new board made entirely from recycled material. The new board had a thickness of 2 mm and exhibited a smooth surface and good mechanical properties, as evidenced by a flexural strength of 11 MPa.

[0150] The experiment was repeated, adding a small amount of additional polymer (5-20 wt.%, calculated based on the amount of polymer present in the board before recycling). This produced a board with a flexural strength of 14 MPa, which is the same as the flexural strength of the original board. Without wishing to be bound by theory, it is believed that during the depolymerization process, some of the resin may have been absorbed by the wood particles, leaving less resin available to bond the particles together. Adding a limited amount of additional resin helps provide additional bonding.

Claims

1. A method for treating a polymer-containing material, comprising the steps of: - providing a starting material comprising a polymer, said polymer being a polyester derived from an aliphatic polyol having 2 to 15 carbon atoms, said aliphatic polyol comprising at least 70 wt.% of a polyol having at least 3 hydroxyl groups, and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms, said aliphatic polyol comprising at least 70 wt.% of a tricarboxylic acid, said polyester having a degree of polymerization of at least 0.7, said degree of polymerization being the ratio of the fraction of reacted functional groups to the maximum number of reactable functional groups, - in the depolymerization step, the raw material is contacted with a nucleophilic agent at a temperature of at least 80° C. for up to 24 hours to achieve depolymerization of the polymer to obtain a polymer having a degree of polymerization that is at least 0.1 lower than the degree of polymerization of the polymer in the raw material and is in the range of 0.1-0.8, the nucleophilic agent comprising at least one of water, a liquid polymer that is a polymerization product of an aliphatic polyol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms, and a liquid monomer for the polymer.

2. The method of claim 1, wherein the raw material comprises a polymer that is a polyester derived from glycerol and citric acid.

3. The method according to any one of the preceding claims, wherein the degree of polymerization of the polyester in the raw material is at least 0.8, or at least 0.9, or at least 0.

95.

4. The method according to any one of the preceding claims, wherein when the nucleophile applied in the depolymerization step comprises a liquid polymer, the liquid polymer has the same chemical composition as the polymer in the starting material, and when the nucleophile applied in the depolymerization step comprises a monomer, the monomer mixture has the same composition as the monomers that build up the polymer in the starting material.

5. The process according to any one of the preceding claims, wherein the depolymerization step is carried out at a temperature of at least 90°C, in particular at least 100°C and / or at most 220°C.

6. The process according to any one of the preceding claims, wherein after the depolymerization step, the degree of polymerization of the polymer is in the range of 0.1 to 0.7, in particular in the range of 0.2-0.6 or 0.2-0.

5.

7. A method according to any one of the preceding claims, wherein the raw material comprises a filler.

8. The process according to any one of the preceding claims, wherein a size reduction step is performed before or after the deagglomeration step.

9. The method according to claim 7 or 8, wherein the depolymerization step is followed by a separation step in which the liquid polymer produced in the depolymerization step is separated from the filler.

10. The method of claim 7, wherein after the depolymerization step, a combination of filler and polymer having a reduced degree of polymerization is processed together.

11. A method according to any one of the preceding claims, wherein the object comprising the depolymerised polymer is subjected to a curing step to increase the degree of polymerisation to a value of, for example, at least 0.7, at least 0.8 or at least 0.

9.

12. The process according to any one of claims 1 to 6, wherein the polymer-containing raw material is free of fillers and the depolymerization step is carried out to a degree of polymerization of 0.1 to 0.7, in particular 0.2 to 0.6, more particularly 0.2-0.5, in particular using a nucleophile comprising a liquid polymer.

13. The method according to claim 7, wherein the shaped object of the filler-containing polymer-containing material is subjected to a depolymerization step and subsequently to a shaping step and a curing step.