Method for treating polymer-containing materials

Abstract

The present invention provides a method for treating a polymer-containing material, comprising: providing a starting material comprising a polymer which is a polyester derived from an aliphatic polyalcohol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms, wherein the aliphatic polyalcohol comprises at least 70% by weight of a polyalcohol having at least three hydroxyl groups, and the aliphatic polycarboxylic acid comprises at least 70% by weight of a tricarboxylic acid, and the polyester has a degree of polymerization of at least 0.7, the degree of polymerization being the ratio of the number of reacted functional groups to the maximum number of reactive functional groups; In the depolymerization step, the starting material is contacted with a nucleophilic agent at a temperature of at least 80°C for not more than 24 hours to depolymerize the polymer, resulting in a polymer having a degree of polymerization that is reduced by at least 0.1 compared to the degree of polymerization of the polymer in the starting material and is in the range of 0.1 to 0.8, wherein the nucleophilic agent is at least one of water, a liquid polymer that is the polymerization product of an aliphatic polyalcohol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms, and a liquid monomer of the polymer. It has been found that the method according to the invention makes it possible to reduce the molecular weight of the polymer in an efficient and cost-effective manner, while providing a material that can be applied in various ways in industry.

Description

[Technical Field]

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

[0002] This polymer has been described in the art for a wide variety of uses.

[0003] International Publication No. WO 2012 / 140237 describes a composite material comprising 10 to 98% by weight of a bio-based particulate or fibrous filler and at least 2% by weight of a polyester derived from an aliphatic polyalcohol having 2 to 15 carbon atoms and a polycarboxylic acid, the polycarboxylic acid comprising at least 10% by weight of a tricarboxylic acid. In particular, the filler can be selected from wood chips, wood flakes, sawdust, pulp, such as pulp from (recycled) paper or other fiber pulps, and plant-derived fibers, such as cotton, linen, flax, and hemp.

[0004] WO 2012 / 140239 describes a composite material comprising the same polymer material as the composite material of WO 2012 / 140237, but in this case a synthetic filler is used which is preferably one or more ceramics, such as preferably selected from glass (especially glass fibres), polymers (especially polymer fibres), and carbon (especially carbon fibres).

[0005] WO2012 / 052385 describes the same polymer in the form of a foam.

[0006] The above-cited documents describe polyesters obtained by polymerizing polyalcohols having at least three hydroxyl groups, particularly glycerol, with polycarboxylic acids having at least three carboxylic acid groups, particularly glycerol.The use of these monomers, particularly at high polymerization degrees, results in thermosetting resins with high strength and durability, which are suitable for use in products such as furniture, building and construction materials (for indoor and outdoor use), and other applications requiring resilience.Examples of this type of composition are described in International Publication No. WO2022 / 0106724 and unpublished International Publication No. WO2022 / 214552. Summary of the Invention [Problem to be solved by the invention]

[0007] As renewable and recyclable materials become increasingly important, there is a need in the art for methods of recycling polymer-containing materials. It would be particularly advantageous if such materials could be converted in an efficient manner into materials that can be reused for the production of high-value materials. The present invention provides such methods. [Means for solving the problem]

[0008] The present invention provides a method for treating a polymer-containing material, comprising: providing a starting material comprising a polymer which is a polyester derived from an aliphatic polyalcohol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms, wherein the aliphatic polyalcohol comprises at least 70% by weight of a polyalcohol having at least three hydroxyl groups, and the aliphatic polycarboxylic acid comprises at least 70% by weight of a tricarboxylic acid, and the polyester has a degree of polymerization of at least 0.7, the degree of polymerization being the ratio of the number of reacted functional groups to the maximum number of reactive functional groups; In the depolymerization step, the starting material is contacted with a nucleophilic agent at a temperature of at least 80°C for not more than 24 hours to depolymerize the polymer, resulting in a polymer having a degree of polymerization that is reduced by at least 0.1 compared to the degree of polymerization of the polymer in the starting material and is in the range of 0.1 to 0.8, wherein the nucleophilic agent is at least one of water, a liquid polymer that is the polymerization product of an aliphatic polyalcohol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms, and a liquid monomer of the polymer. The present invention relates to the above method, which comprises the steps of:

[0009] It has been found that the process according to the invention makes it possible to reduce the molecular weight of the polymer in an efficient and cost-effective manner, while at the same time providing a material that can be applied in various ways in industry, in particular the polymer recovered from the process can be reused in the manufacture of new polymeric materials while maintaining good product quality.

[0010] The present invention allows for 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 allows for the conversion of thermosetting polymers into materials with a lower degree of polymerization, which can then be used as starting materials for producing new materials, such as new thermosetting materials. This distinguishes conventionally used thermosetting polymer materials from those that cannot be easily converted into highly efficient, repolymerizable products while maintaining product quality. [Effects of the Invention]

[0011] A particular advantage of the method according to the present invention is that the nucleophile used in the present invention is a compound that does not affect the repolymerization process. If water is used, it is removed in the repolymerization process along with the water produced in the esterification process. If a specific liquid polyester or its monomers are used, they are incorporated into the newly formed polymer. If the composition of the polymer or monomer used as the nucleophile matches the polymer being depolymerized, the composition of the final product does not change at all. This is different from the nucleophiles used in many prior art depolymerization methods. DETAILED DESCRIPTION OF THE INVENTION

[0012] The invention, its specific embodiments, and its associated advantages will be described in more detail below.

[0013] Starting materials

[0014] The first step of the process according to the present invention is to provide a starting material comprising a polymer that is the polymerization product of an aliphatic polyalcohol having from 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having from 2 to 15 carbon atoms, wherein the polymer in the starting material has a degree of polymerization of at least 0.55.

[0015] In the context of the present invention, the degree of polymerization of a polymer is defined as the ratio of the number of reacted functional groups to the maximum number of reactive functional groups, which can be determined by acid number (especially values ​​less than 0.5) or gravimetrically (especially values ​​greater than 0.5).

[0016] To determine the degree of polymerization of a polymer of unknown degree of polymerization derived from an aliphatic polyalcohol and an aliphatic polycarboxylic acid using gravimetric analysis, it is clear that a sample of the polymer of unknown degree of polymerization must be cured at a temperature of 100-220°C until no more water is lost. As a result, the degree of polymerization of the polymer is 1, and the water lost during the curing can be used to back-calculate the degree of polymerization of the sample polymer.

[0017] polymer

[0018] The polymer is derived from an aliphatic polyalcohol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms.

[0019] Suitable polyalcohol monomers for use in the present invention contain 2 to 15 carbon atoms. The aliphatic polyalcohol does not contain an aromatic moiety, a nitrogen atom, or a sulfur atom. In some embodiments, the aliphatic polyalcohol consists of carbon, oxygen, and hydrogen atoms. The aliphatic polyalcohol contains at least two hydroxyl groups, preferably at least three hydroxyl groups. Generally, the number of hydroxyl groups is 10 or less, preferably 8 or less, and more preferably 6 or less. The aliphatic polyalcohol has 2 to 15 carbon atoms, preferably 3 to 10 carbon atoms. Examples of suitable aliphatic polyalcohols include 1,2-propanediol, 1,3-propanediol, 1,2-ethanediol, 1,4-butanediol, glycerol, sorbitol, xylitol, and mannitol. Glycerol, sorbitol, xylitol, and mannitol are preferred examples of suitable aliphatic polyalcohols. Glycerol is the most preferred example of a suitable aliphatic polyalcohol. One reason is that glycerol has a melting point of 20°C, thereby allowing for easy processing (compared to, for example, xylitol, sorbitol, and mannitol, all of which have melting points above 90°C). Moreover, glycerol is readily available and results in polymers with desirable properties. Thus, in some embodiments, the aliphatic polyalcohol consists essentially of glycerol. As used herein, "consisting essentially of" means that other components (herein, other aliphatic polyalcohols) may be present in amounts that do not adversely affect the properties of the material.

[0020] The aliphatic polyalcohol comprises at least 70% by weight, particularly at least 80% by weight, more preferably at least 90% by weight, and most preferably at least 95% by weight of polyalcohol having at least three hydroxyl groups, calculated from the total amount of aliphatic polyalcohol. In some embodiments, the aliphatic polyalcohol essentially consists of polyalcohol having at least three hydroxyl groups. Preferably, the polyalcohol having at least three hydroxyl groups consists of at least 70% by weight, particularly at least 80% by weight, more particularly at least 90% by weight or at least 95% by weight of glycerol.

[0021] Mixtures of different aliphatic polyalcohols may also be used. The aliphatic polyalcohols may contain at least 50 mol%, preferably at least 70 mol%, and more preferably at least 90 mol% of glycerol, sorbitol, xylitol, or mannitol. Preferably, the remainder is an aliphatic polyalcohol having 3 to 10 carbon atoms. The polyalcohol preferably contains at least 70 mol%, preferably at least 90 mol%, and more preferably at least 95 mol% of glycerol.

[0022] In some embodiments, the aliphatic polyalcohol has a ratio of hydroxyl groups to the number of carbon atoms of 1:4 (i.e., 1 hydroxyl group per 4 carbon atoms) to 1:1 (i.e., 1 hydroxyl group per 1 carbon atom). Preferably, the ratio of hydroxyl groups to the number of carbon atoms is 1:3 to 1:1, more preferably 1:2 to 1:1, and even more preferably 1:1.5 to 1:1. Compounds having a ratio of hydroxyl groups to the number of carbon atoms of 1:1 are considered particularly preferred.

[0023] 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, and in some embodiments, 3 to 6 carbon atoms. The aliphatic polycarboxylic acids do not contain aromatic moieties, any nitrogen atoms, or any sulfur atoms. In some embodiments, the aliphatic polycarboxylic acids consist of carbon atoms, oxygen atoms, and hydrogen atoms. The aliphatic polycarboxylic acids contain at least two carboxylic acid groups, preferably three carboxylic acid groups. Generally, the number of carboxylic acid groups is 10 or less, preferably 8 or less, and more preferably 6 or less.

[0024] The aliphatic polycarboxylic acid comprises at least 70% by weight of tricarboxylic acid, calculated based on the total amount of aliphatic polycarboxylic acid. The aliphatic polycarboxylic acid may comprise at least 80% by weight, more preferably at least 90% by weight, and most preferably 95% by weight of tricarboxylic acid. In some embodiments, the aliphatic polycarboxylic acid consists essentially of tricarboxylic acid, preferably citric acid.

[0025] The aliphatic polycarboxylic acid may be a mixture of acids, such as a mixture of one or more tricarboxylic acids and one or more dicarboxylic acids. In some embodiments, the aliphatic polycarboxylic acid comprises 2 to 30 wt. %, preferably 5 to 30 wt. %, and in some embodiments, 10 to 30 wt. %, of dicarboxylic acids in combination with at least 70 wt. %, more preferably at least 80 wt. %, of tricarboxylic acids, calculated on the total amount of aliphatic polycarboxylic acid.

[0026] When a dicarboxylic acid is used, the dicarboxylic acid may be any carboxylic acid having two carboxylic acid groups and generally 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.

[0027] The tricarboxylic acid can be any tricarboxylic acid having three carboxylic acid groups and generally not more than 15 carbon atoms. Examples include citric acid, isocitric acid, aconitic acid (both cis and trans), and 3-carboxy-cis,cis-muconic acid. The use of citric acid is considered preferable for both cost and availability reasons. Where applicable, acids can also be provided in the form of their anhydrides, such as citric acid anhydride. In one embodiment, the tricarboxylic acid consists of at least 70% by weight, particularly at least 80% by weight, more particularly at least 90% by weight, and even more particularly at least 95% by weight of citric acid.

[0028] In one embodiment, the polymer is a polyester derived from an aliphatic polyalcohol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms, wherein the aliphatic polyalcohol comprises at least 70% by weight, more preferably at least 80% by weight, even more preferably at least 90% by weight, and most preferably 95% by weight, of a polyalcohol having at least three hydroxyl groups; the aliphatic polyalcohol having at least three hydroxyl groups is preferably glycerol; and the aliphatic polycarboxylic acid comprises at least 70% by weight, preferably at least 80% by weight, more preferably at least 90% by weight, and most preferably 95% by weight, calculated from the total amount of acid, of a tricarboxylic acid; the tricarboxylic acid is preferably citric acid.

[0029] In one embodiment of the invention, the polymer is derived from a combination of polyalcohol monomers and polycarboxylic acid monomers, The polyalcohol monomer is preferably selected from aliphatic polyalcohols having at least three hydroxyl groups and having 2 to 15 carbon atoms, such as glycerol, sorbitol, xylitol and mannitol, in particular glycerol; The polycarboxylic acid monomer is selected from aliphatic polycarboxylic acids having at least three carboxylic acid groups and having 3 to 15 carbon atoms, such as citric acid, isocitric acid, aconitic acid (both cis and trans), and 3-carboxy-cis,cis-muconic acid, especially citric acid.

[0030] In the present invention, the ratio of the total number of hydroxyl groups to the total number of carboxyl groups in the system is preferably in the range of 2:1 to 0.5:1, particularly in the range of 1.5:1 to 0.6:1, more particularly in the range of 1.25:1 to 0.8:1, and even more particularly in the range of 1.1:1 to 0.9:1. When the polyalcohol and the polycarboxylic acid are completely composed of a triol and a triacid, respectively, this means that the molar ratio of these compounds is in the range of 2:1 to 0.5:1, particularly in the range of 1.5:1 to 0.6:1, more particularly in the range of 1.25:1 to 0.8:1, and even more particularly in the range of 1.1:1 to 0.9:1. When using polyalcohols or polyacids having different numbers of hydroxyl groups and carboxyl groups, this should be taken into consideration when determining the relative amounts of the compounds to be used.

[0031] It is believed that it is advantageous for the ratio of the total number of hydroxyl groups to the total number of carboxyl groups in the system to be within a specified range in order to achieve the highest possible conversion. Achieving a high conversion is believed to be advantageous because it limits the amount of remaining hydroxyl or acid functional groups. These functional groups are hygroscopic and can have a detrimental effect on the applicability of the product in demanding applications where product durability is required.

[0032] As shown above, the starting polymer has a degree of polymerization of at least 0.7. Polymers with a degree of polymerization in this range can be obtained by polymerizing a combination of polyalcohol monomers and polycarboxylic acid monomers. Generally, in a first step, a mixture of monomers in a liquid phase can be prepared. Depending on the nature of the components, this can be done, for example, by heating the mixture of components to a temperature at which the acid dissolves in the alcohol, particularly glycerol. Depending on the nature of the components, this can be done, for example, at a temperature in the range of 20 to 250°C, e.g., 40 to 200°C, e.g., 60 to 200°C, or 90 to 200°C. In one embodiment, the mixture can be heated and mixed at a temperature of 80 to 200°C, particularly 100 to 200°C, and in some embodiments, 120 to 180°C, for 1 minute to 2 hours, more particularly 5 to 45 minutes. Optionally, a suitable solvent, e.g., water, can be present. Preferably, the amount of water is limited because evaporation of water consumes energy. It may be preferable to add up to 30% by weight of water, especially up to 20% by weight of water.

[0033] Optionally, a suitable catalyst can be used for the preparation of the polyester. Catalysts suitable for polyester production are known in the art. Preferred catalysts are heavy metal-free catalysts. Both basic and acidic catalysts can be used. Both homogeneous and heterogeneous catalysts, such as those based on zeolites, modified hydrotalcites, or resins based on amberlite or Nafion, can be used. Useful acidic catalysts include, but are not limited to, hydrochloric acid, hydroiodic acid (also referred to as hydroiodic acid), hydrobromic acid, sulfuric acid (HSO), nitric acid (HNO), chloric acid (HCIO), boric acid, sodium hypophosphite, perchloric acid (HCIO), trifluoroacetic acid, p-toluenesulfonic acid, sulfonic acid, and trifluoromethanesulfonic acid. Catalysts such as Ti-butoxide, Sn-octanoate, Zn-acetate and Mn-acetate can also be used, although these catalysts may be less preferred.

[0034] The monomer mixture is subjected to a heating step to obtain a degree of polymerization of at least 0.55, particularly at least 0.6. The mixture is typically cured at an internal temperature of 80 to 250°C, particularly 220°C, for example, for 5 seconds to 24 hours. The curing step is typically carried out at an internal temperature of at least 80°C, particularly at least 100°C, more particularly at least 120°C, and even more particularly at least 130°C. Higher internal temperatures result in increased side reactions. Therefore, it is preferred that the internal temperature does not exceed 250°C. It may be preferred that the internal temperature be in the range of 130 to 220°C, particularly 130 to 200°C. The internal temperature is measured during curing or immediately after the molded article is removed from the curing means, such as an oven or press.

[0035] 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. Various types of ovens may 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 attractive. Curing can also be carried out by radio frequency heating. Curing can be carried out in a single step or in multiple steps. Curing times range from 5 seconds to 24 hours, depending on the size and shape of the object, the desired internal temperature, and the heating system used. When microwave or radio frequency heating is applied, curing times of 10 seconds to 30 minutes are generally sufficient. When a conventional oven is used, the total curing time is preferably at least 10 minutes, especially at least 20 minutes, and not more than 12 hours, especially not more than 6 hours. Long curing times, while not disadvantageous in themselves, may be less attractive from an economical standpoint. It is within the skill of the art to select suitable curing conditions. If desired, curing can be carried out in one step or in multiple steps. When multiple steps are applied, the curing temperature of the second step is generally higher than the curing temperature applied in the first step.

[0036] Filler

[0037] The starting materials in the process of the present invention may or may not contain fillers.

[0038] Various types of fillers can be envisaged. Generally, particulate, fibrous and / or lamellar fillers of natural or synthetic origin can be used. Combinations of various fillers can be used. The fillers may be present in an amount of 10 to 95% by weight, in particular in an amount of 20 to 80% by weight, more in particular in an amount of 40 to 70% by weight, calculated on the total weight of the composite object.

[0039] 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 length of a particle determined along its longest axis relative to its maximum diameter determined along an axis perpendicular to the longest axis.

[0040] The particulate material may have a maximum length, determined along the longest axis of the particles in the material, of less than 20 mm, more preferably 15 mm or less, more preferably 10 mm or less, particularly 5 mm or less, and especially 2 mm or less. As a minimum value, an average particle length of 0.001 mm may be mentioned. In some embodiments, the average particle length is at least 0.05 mm, particularly at least 0.1 mm, more particularly at least 0.5 mm. In some embodiments, the average particle length is in the range of 0.5 to 5 mm, especially 0.5 to 2 mm.

[0041] Suitable particulate materials may be in the form of, for example, powder, dust, pulp, shredded fibers, flakes, or chips. Examples include wood chips, wood flakes, sawdust, hemp dust, (dried) grass, and pulp, such as (recycled) paper pulp or other fiber pulps from sugar beets, fruits, and vegetables. Examples of plant-derived materials that can be used as particulate materials are cotton, flax, hemp, grass, reeds, bamboo, coconut, miscanthus, coffee grounds, seed husks, e.g., rice, hemp, kenaf, ramie, sisal, etc., and materials derived therefrom. Generally, plant materials can be used that have been ground to a suitable particle size and, if necessary, dried to a suitable vinegar content.

[0042] The particulate material may include natural materials, such as materials derived from plants or animals. Examples of plant-derived materials include cellulose-based materials, such as fresh or used paper, fresh or used cardboard, wood, or any form of other plant material, and combinations thereof. The cellulose-based material may be derived from so-called virgin pulp, which is obtained directly from the wood pulping process. This pulp can be obtained from any plant material, but most is obtained from wood. Wood pulp is obtained from softwoods, such as spruce, pine, fir, larch, and hemlock, and hardwoods, such as eucalyptus, poplar, aspen, and birch. Additionally or alternatively, the cellulose-based material may include cellulose material derived from recycled paper, for example, from cellulose pulp obtained from recycled books, paper, newspapers and periodicals, egg cartons, and other recycled paper or cardboard products. A combination of cellulose sources may also be used. Other attractive sources of cellulose-based materials are reject paper fibers (paper fibers that are too short to be used in paper production) and materials recycled (mechanically and / or chemically) from any (composite) material, for example, recycled furniture made from cellulose-based materials. In particular, (composite) materials using the polymers mentioned herein as binders are attractive sources of cellulose-based materials. The use of these (recycled) materials is highly sustainable and low-cost, making them widely applicable, for example, in furniture manufacturing.

[0043] Examples of animal-derived materials include feathers, down, hair and derivatives thereof such as wool, but also bone meal.

[0044] Further examples of suitable particulate materials include ceramic materials, such as oxides, such as alumina, beryllia, ceria, zirconia, silica, titania, and mixtures and combinations thereof, and non-oxides, such as carbides, borides, nitrides, silicides, and mixtures and combinations thereof, such as silicon carbide. For purposes of this specification, glass is considered a ceramic material. Glass can be used in the form of, for example, short fibers, glass beads, whether solid or hollow, and crushed glass particles. Suitable particulate materials further include materials such as fine fillers, calcium carbonate, and minerals, such as phyllosilicates. Clay, sand, talcum, gypsum, etc. can also be used.

[0045] Suitable particulate materials also include polymer fillers, such as particles or short fibers of polyethylene, polypropylene, polystyrene, polyesters such as polyethylene terephthalate, polyvinyl chloride, polyamides (e.g., nylon-6, nylon 6.6, etc.), polyacrylamide, and arylamide polymers such as aramid. Suitable particulate materials also include carbon fibers and carbon particulate materials. The ground cured polyester resin used in the present invention can also be used as the particulate material. Ground cured polyester resin containing a filler can also be used.

[0046] In some embodiments, particulate materials are used that include one or more organic particulate materials, such as one or more organic particulate materials selected from the group consisting of shives, wood dust, wood chips, and recycled paper. In other embodiments, the particulate material (also) includes one or more inorganic particulate materials, such as one or more inorganic particulate materials selected from the group consisting of (recycled) glass, stone, ceramic, minerals, and metals.

[0047] Suitable fillers also include fibrous materials, which in the context of this specification are materials having an aspect ratio of greater than 10:1.

[0048] In the context of this specification, the term "fiber" refers to monofilaments, multifilament monofilaments, threads, tapes, strips, and other elongated objects having a regular or irregular cross-section and a length that is substantially greater than its width and thickness.

[0049] Suitable fibrous materials may, for example, have a fiber length, determined across their longest axis, of at least 1 cm, preferably at least 3 cm, and more preferably at least 4 cm. For example, the fibrous materials may have a fiber length, determined across their longest axis, of 1 to 20 cm. Preferably, the fibrous materials have a fiber length of 1 to 10 cm. Longer fibers are preferred because they provide strength to the composition.

[0050] The fibrous material may include 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 in many applications because they result in a smooth surface for the object. The fibers may have an aspect ratio in the range of 20:1 to 200,000:1, preferably 200:1 to 20,000:1, and more preferably 250:1 to 5000:1. The use of fibers with a relatively large aspect ratio allows for a combination of high strength and a smooth surface.

[0051] The fibers that may be used as fillers in the present invention may be oriented randomly (e.g., a nonwoven sheet) or in a non-random manner. The fibrous material is preferably a nonwoven sheet.

[0052] In the context of this specification, "non-randomly oriented" refers to any structure in which the fibers are oriented relative to one another in an essentially regular manner. Examples of layers containing non-randomly oriented fibers include woven layers, knitted layers, layers in which the fibers are oriented parallel, and any other layer in which the fibers are connected to one another in a repeating pattern.

[0053] The orientation of fibers in a fibrous material can affect, for example, the strength of the final product. Therefore, 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, more anisotropic properties or bidirectional resistance may be required.

[0054] The fibrous material that can be used in the present invention can include plant-derived fibers, preferably cellulosic and / or lignocellulosic fibers. The fibrous material can also consist essentially of plant-derived fibers. Examples of plant-based fibers include flax, hemp, kenaf, jute, ramie, sisal, coconut, bamboo, and cotton. The fibrous material can also include animal-derived fibers. Animal-derived fibers can be fibers derived from wool, hair, silk, and feathers (e.g., chicken feathers). Other parts of internal organs can also be used. The fibrous material can include synthetic fibers. Examples of suitable synthetic fibers are fibers obtained from viscose, glass, polyester, carbon, aramid, nylon, acrylic, polyolefin, etc. The fibrous material can also be a mixture of fibers of different origins, for example, a mixture of plant-derived fibers and synthetic fibers.

[0055] In the context of this specification, a composition of a filler and a polymer also includes a composition in which the filler is provided in the form of thin layers, alternating with layers of polymer. Suitable layered materials generally contain at least two, especially at least four, and up to 50, especially up to 20, filler layers. Each filler layer generally has a thickness of 0.1 to 10 mm, especially 0.1 to 5 mm, more especially 0.2 to 2 mm. The total thickness of the object is, for example, 0.5 to 200 mm. The polymer layer may have a thickness of, for example, 10 to 4000 microns, especially 10 to 2000 microns, more especially 10 to 500 microns. A suitable filler is, for example, wood (also referred to as wood veneer). Plywood is an example of this embodiment. Other layered fillers, such as paper or cardboard, may also be applied.

[0056] As will be appreciated by those skilled in the art, different types and combinations of materials may also be used as fillers.

[0057] The starting material used in the present invention may be filler-free, in which case, in one embodiment, it is a polymer foam.

[0058] In the starting material, the polymer has a degree of polymerization of at least 0.7. Generally, the starting material is in a solid state at room temperature. The ability to process solid starting materials is a special feature of the method of the present invention. The degree of polymerization of the polymer in the starting material may be higher, for example, at least 0.8, at least 0.9, or at least 0.95. It is a feature of the present invention that the method of the present invention is also applicable to starting materials with a high degree of polymerization. This is surprising because these materials are stable and resistant to degradation.

[0059] Depolymerization process

[0060] In the method of the present invention, a depolymerization step is carried out in which the starting material is contacted with a nucleophile at a temperature of at least 60°C to cause depolymerization of the polymer and reduce the degree of polymerization of the polymer in the starting material by at least 0.1, to a value in the range of 0.1 to 0.8, wherein the nucleophile comprises at least one of water, a liquid polymer that is the polymerization product of an aliphatic polyalcohol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms, and a plurality of monomers of the polymer.

[0061] In the depolymerization step, a nucleophile selected from water, a liquid polymer that is the polymerization product of an aliphatic polyalcohol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms, and a plurality of monomers of the polymer is used. By selecting this particular group of nucleophiles, no "new" compounds need to be added to the system.

[0062] The liquid polymer is of the same type as the polymer in the starting material, and the monomers used are of the same type as the monomers of the polymer in the starting material. It may be preferable that the liquid polymer has the same chemical composition as the polymer in the starting material, and in the same sense, it may be preferable that the monomer mixture applied in the depolymerization step has the same composition as the monomers constituting the polymer in the starting material. In the context of this specification, the expression "same chemical composition" is defined as follows: two polymers have the same chemical composition if they consist of at least 75%, particularly at least 80%, more particularly at least 90% of the same monomers.

[0063] The depolymerization step is carried out at a temperature of at least 80°C. Higher temperatures increase the reaction rate, but if the temperature is too high, side reactions may begin to occur. It may be preferable to carry out the depolymerization step 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. If a temperature of 100°C is used, pressures above atmospheric pressure may be applied. The preferred temperature range also depends on the nucleophile used, on the desired reduction in the degree of polymerization, and on further conditions. These parameters will be explained in more detail below.

[0064] Optionally, a catalyst may be present during the depolymerization reaction. Suitable catalysts include those catalysts described above as suitable for polyester production.

[0065] The depolymerization step is generally carried out for 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 high temperatures and very high pressures, a time range of the order of a few minutes may be sufficient, although longer treatment times may be required under these conditions. Depolymerization times exceeding 24 hours are less attractive from an economic point of view and may, in addition, be accompanied by degradation of the product. It may be preferable to carry out the depolymerization step for 12 hours or less, particularly 8 hours or less, and more particularly 6 hours or less.

[0066] In the depolymerization step, the degree of polymerization of the polymer is reduced by at least 0.1. The desired reduction in degree of polymerization in a particular case depends on the degree of polymerization of the starting polymer and the intended 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, particularly at least 0.3, and more particularly at least 0.4. The maximum reduction is 0.9.

[0067] The degree of polymerization of the polymer after the depolymerization step is in the range of 0.1 to 0.8.

[0068] It has been found that carrying out the depolymerization reaction to a degree of polymerization of less than 0.1 is unattractive. This not only requires additional investment of time and energy, but also means that additional water must be removed when the polymer is repolymerized to form a new product, due to the water generated in the reaction between the alcohol group and the carboxylic acid group. On the other hand, if the reduction in the degree of polymerization is limited and the degree of polymerization of the final product is still 0.8, the effectiveness of the method is generally insufficient for the method to be commercially viable. It may be preferable for the degree of polymerization of the polymer after the depolymerization step to be in the range of 0.2 to 0.8.

[0069] In one embodiment, the degree of polymerization after the reaction is in the range of 0.1 to 0.6, particularly in the range of 0.2 to 0.5. This is the range in which the polymer is generally in a liquid phase (depending on the temperature), making it possible to separate the polymer from other components, such as filler materials, combine the polymer with other materials, for example as an adhesive or binder, or reformulate a material containing the polymer. These various aspects will be described below. In another embodiment, the degree of polymerization of the product is in the range of 0.6 to 0.8. This range is particularly attractive when reformulation of an existing filler-containing material is desired.

[0070] Water as a nucleophile

[0071] In one embodiment, the nucleophile used in the present invention comprises water. Water may be present when the liquid polymer of the embodiment or multiple monomers of the polymer are used as the nucleophile. The embodiment will be described under the following headings. This section is directed to the use of nucleophiles comprising water.

[0072] In the method of this embodiment, the starting material is treated with water at a temperature of at least 60°C. Higher temperatures are preferred to increase the depolymerization rate. Therefore, the method is preferably carried out at a temperature of at least 80°C, particularly at least 100°C. It has been found that treatment with water at a temperature of at least 100°C results in rapid depolymerization within a controlled range. 220°C may be mentioned as a maximum temperature. At temperatures above that, side reactions may increase. In addition, temperatures above that are less attractive from an energetic point of view. A reaction temperature of at least 110°C, particularly at least 120°C, is preferred. It is also preferred that the temperature be 200°C or less, particularly 180°C or less. In some embodiments, a temperature of 160°C or less may be preferred.

[0073] If temperatures above 100°C are used, it may be preferable for the pressure during the water treatment to be above 1 bar. As a maximum, a value of 25 bar can be given. Above this value, the process becomes unattractive from an economic point of view. It is particularly preferred that the pressure is in the range of 1.5 to 15 bar, in particular in the range of 2 to 10 bar, and even more particularly in the range of 3 to 8 bar.

[0074] In one embodiment, the reaction is carried out under autogenous pressure, i.e., the pressure is governed by the temperature and amount of water in the reaction vessel.

[0075] Depending on the selected temperature and pressure, water is present in the gas phase. In addition, depending on the amount of water, temperature, and pressure, liquid water is also present. It has been found that the presence of liquid water can increase the depolymerization rate. On the other hand, too much water may result in an undesirable degree of depolymerization. In addition, if it is intended to repolymerize the depolymerized product, it may be attractive to limit the degree of depolymerization by limiting the water content. The presence of excess water may also affect the homogeneity of the product. Therefore, it may be preferable to set an upper limit on the total amount of water present during the depolymerization reaction. On the other hand, since the presence of water is necessary for an effective depolymerization reaction, a minimum amount is also preferred.

[0076] Thus, in one embodiment, the amount of water provided for the depolymerization reaction ranges from 5 to 60 wt. %, particularly 5 to 40 wt. %, and in some embodiments, 10 to 30 wt. %, calculated from the amount of polymer provided for the depolymerization reaction.

[0077] In general terms, it is possible to control the degree of polymerization of the final product by the amount of water, but it may be more attractive to control it by the time of the depolymerization reaction.

[0078] If the starting material includes a water-absorbing material, such as a porous hydrophilic filler, it may be desirable to add additional water to compensate for the water that may be absorbed by the filler, as may be the case, for example, if the starting material includes wood chips as a filler.

[0079] A liquid polymer or a plurality of monomers of said polymer as the nucleophile

[0080] In one embodiment of the present invention, the starting material is contacted with a nucleophile comprising a liquid polymer that is the polymerization product of an aliphatic polyalcohol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms. Additionally or alternatively, the starting material is contacted with a nucleophile comprising multiple monomers of the polymer, i.e., monomers selected from an aliphatic polyalcohol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms, and combinations thereof. The preferred embodiments described above for the composition of the starting material also apply here, with the exception that the requirements for the amount of polyalcohol having at least three hydroxy groups and the amount of tricarboxylic acid are not required for the nucleophile.

[0081] When a nucleophilic agent containing one or more polymers or monomers is used, the nucleophilic agent is a liquid medium, the temperature of which is generally in the range of 80 to 220°C, preferably in the range of 80 to 160°C.

[0082] The degree of polymerization of the products obtained by this method is generally from 0.1 to 0.7, in particular from 0.2 to 0.6, more in particular from 0.2 to 0.5.

[0083] When a liquid polymer or its monomers are used as a 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 generally 40% by weight or less, particularly 30% by weight or less, more particularly 20% by weight or less of the total liquid mixture. Since water needs to be removed in a later step, a low water content is preferred.

[0084] In this embodiment, the amount of liquid medium should be sufficient to allow the polymer to disintegrate into the liquid medium. Thus, in one embodiment, the volume of the liquid medium is at least 50% by volume of the polymer to be depolymerized therein. Because excessive volume is undesirable, it is preferred that the volume of the liquid medium be 500% by volume or less of the volume of the polymer to be depolymerized therein.

[0085] This embodiment is particularly attractive for depolymerizing a starting material that consists largely of the particular polyester polymer, e.g., at least 90% by weight, particularly at least 95% by weight, more particularly at least 98% by weight, or at least 99% by weight.

[0086] Selection of the Starting Materials and Methods

[0087] The method for treating polymer-containing materials according to the present invention can be applied to starting materials that contain fillers, but also to starting materials that do not contain fillers. Examples of different types of starting materials will be described below.

[0088] In one embodiment, the starting material used in the process according to the present invention is a polymer-containing material consisting predominantly of, for example, at least 90% by weight, particularly at least 95% by weight, more particularly at least 98% by weight, or at least 99% by weight of a particular polyester polymer. In this case, the process according to the present invention can be used, for example, to convert the polymer into a liquid phase up to a degree of polymerization generally in the range of 0.1 to 0.6, particularly 0.2 to 0.5. Higher degrees of polymerization are also possible.

[0089] When the starting material further contains a solid component, designated as a filler, various options exist, depending, inter alia, on the nature of the filler, the relative amounts of polymer and filler, and the intended further use of the various compounds. In one embodiment, the polymer is converted to a liquid phase and converted to a degree of polymerization generally in the range of 0.1 to 0.6, preferably 0.2 to 0.5, and a separation step is carried out to separate the liquid product polymer from the filler. The liquid product and the filler, which generally still contain some polymer, are then processed separately.

[0090] In another embodiment, the filler and the polymer are not separated after the depolymerization step. In this case, the product of the depolymerization step, which includes the polymer with a reduced degree of polymerization and the filler, can be processed directly to form a new object. 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 above also apply to this embodiment.

[0091] Depending on the nature of the starting material and the intended further processing, the starting material may be subjected to a size reduction step before being submitted to the depolymerization step. If the starting material has a smaller size, the contact surface with water or steam will be larger, and the reaction rate will increase. On the other hand, it is important not to affect the properties of the filler by reducing the particle size too much, especially if the filler has a relatively large particle size or is fibrous and its properties are to be reused. In other embodiments, size reduction is performed only to a limited extent or not at all, for example, when a re-forming step is intended to be performed after the depolymerization step. It is also attractive to perform size reduction after the depolymerization step, because depolymerization of the polymer softens the material, making size reduction easier to perform. Of course, it is also possible to perform size reduction between two depolymerization steps.

[0092] In some embodiments, a molding process may be performed. In the context of this specification, a molding process is any process in which a material comprising a depolymerized polymer and a filler is subjected to a process in which its shape is changed. This can be done, for example, by bending, folding, flattening, or other methods that change the shape of the entire object, but it can also be achieved by combining multiple materials and forming a new shape. Changing the shape of an existing object after depolymerization can also be referred to herein as remolding.

[0093] In some embodiments, the depolymerized polymer-containing object is subjected to a curing process 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 moisture content of the object is generally less than 10% by weight (calculated from the total weight of the layered structure), preferably less than 5% by weight, more preferably less than 2% by weight, and most preferably less than 1% by weight. Depending on storage conditions, the moisture content of the object may increase after curing. For more information regarding the curing process, please refer to the description of curing in the context of the starting material.

[0094] In the following, various specific embodiments of the method according to the invention will be described, without the invention being limited thereto or by them. Aspects of different embodiments can be combined, and further embodiments will be apparent to those skilled in the art.

[0095] Processing of unfilled polymer-containing materials

[0096] In one embodiment, the polymer-containing material does not contain a filler. In this embodiment, the polymer-containing material is generally a solid polymer material, for example, in the form of a foam, consisting mostly of, for example, at least 90% by weight of polymer, particularly at least 95% by weight of polymer. In this case, the method of the present invention is generally used to convert the polymer into a liquid phase up to a degree of polymerization in the range of 0.2 to 0.6, particularly 0.2 to 0.5.

[0097] The filler-free solid polymer material may preferably be provided to the process according to the present invention in particulate form, for example in the form of particles having a maximum particle diameter of 10 cm (i.e., 90% of the particles have a diameter less than this value). Compared to larger particulate materials, the reduction in size leads to an increased reaction rate due to an increased contact area between water and / or steam and the solid polymer material. In addition, the water vapor has to travel a shorter distance to reach the core of the polymer-containing material. The material may preferably be in the form of particles having a maximum particle diameter of 6 cm, particularly 4 cm, more particularly 2 cm, and in some embodiments, 5 mm or less. Grinding may also be applied.

[0098] When the polymer-containing material does not contain a filler, it may be preferable to carry out the process in such a manner that the product of the depolymerization reaction is a liquid product to enable efficient removal from the depolymerization reactor. In one embodiment, when 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. The more general ranges also apply to this embodiment. The use of a nucleophile containing a liquid polymer may be particularly preferred.

[0099] When a liquid polymer is used as the nucleophile, it may be preferable to incorporate at least 40% by weight of the starting material into the nucleophile in order to make optimal use of the reactor volume.

[0100] The product from the depolymerization reaction may be processed as desired. The product may optionally be subjected to one or more purification steps, such as filtration to remove remaining solid particles, or purification using activated carbon to remove color- or odor-causing contaminants. Optionally, excess water may also be removed.

[0101] Processing and reshaping of filled polymer-containing materials

[0102] In one embodiment, the method is intended to reform an existing product. In this case, the starting material is a polymer-containing material containing a polymer and a filler. The polymer-containing material generally contains 10 to 70% by weight of polymer and 30 to 90% by weight of filler.

[0103] In this embodiment, a molded body of polymer-containing material is subjected to a depolymerization step, then a molding step, and then a curing step.

[0104] In this case, the degree of polymerization after the depolymerization reaction is generally greater than 0.2, in particular greater than 0.3, more in particular greater than 0.5.

[0105] After the depolymerization reaction, the resulting product is flexible. It is subjected to a force to change shape, followed by a curing step, which is typically carried out by using, for example, a mold or press while holding the product in its new shape.

[0106] In this embodiment, the nucleophile applied in the depolymerization step is preferably water vapor.

[0107] Processing of materials containing filled polymers - Polymer separation

[0108] In one embodiment, the method of the present invention is intended to recover polymer from a material containing a filler-containing polymer.This method may be particularly attractive when the material containing the polymer has a high polymer content and / or when the polymer does not adhere strongly to the filler.For example, non-porous fillers, such as glass particles or glass fibers, carbon particles or carbon fibers; or polymer fillers, such as aramid-based fillers, are generally easier to separate from the polymer than porous natural fibers, such as hemp fibers.Separability also depends on the additional properties of the filler.

[0109] In this embodiment, the method according to the invention comprises the steps of subjecting a material comprising a filled polymer to a depolymerization step and then separating the depolymerized polymer from the filler.

[0110] In one embodiment, the degree of polymerization after the reaction is generally in the range of 0.2 to 0.6, particularly in the range of 0.2 to 0.5. This is the range in which the polymer is generally in a liquid phase (depending on the temperature) and allows the polymer to be separated from the filler. The presence of liquid water helps to reduce the viscosity of the polymer medium, which can improve the separation process.

[0111] The separation step can be carried out by methods known to those skilled in the art, such as filtration or decantation. If desired, pressing and / or washing may be applied to remove additional materials from the filler. The polymer thus recovered can be used to produce new polymer-containing products. The filler from which the polymer has been separated can also be processed as desired.

[0112] Creating new particle starting materials

[0113] In one embodiment, the method according to the present invention is used to produce new particulate starting material from an existing product. In this embodiment, the method according to the present invention comprises the steps of providing a material comprising a filler-containing polymer in the form of particles and subjecting the material to a depolymerization step, thereby resulting in a polymer comprising filler-containing particles.

[0114] In this embodiment, the degree of polymerization after the depolymerization reaction is generally greater than 0.3, particularly greater than 0.5. The polymer-containing material generally contains 10 to 70% by weight of polymer and 30 to 90% by weight of filler. In this embodiment, it is considered preferable to use water / steam as the nucleophile. The particles can be reused to produce new products, for example, by combining the particles with one or more additional polymers or additional filler materials and subjecting the mixture to a molding or curing process, as described in International Publication No. WO 2022 / 106724.

[0115] Reuse of the resulting product

[0116] The process according to the present invention results in a polymer that is the polymerization product of an aliphatic polyalcohol 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 products of the process of the present invention can be used as starting materials in the manufacture of new products. They can be combined with, for example, a filler. Suitable fillers are described above in the context of the starting materials. Suitable manufacturing and curing conditions are also described above in the context of the starting materials. In addition, reference may be made to the products and methods described in WO2012 / 052385, WO2012 / 140238, WO2012 / 140239, WO2012 / 140237, WO2013 / 121033, WO2020 / 152082, WO2020 / 212427, WO2021 / 023495, WO2021 / 105143, WO2022 / 043330 and WO2022 / 106724.

[0117] All percentages used herein are by weight unless otherwise specified.

[0118] As will be apparent to one skilled in the art, different embodiments of the present invention may be combined as long as they are not mutually exclusive. The headings used herein are for readability purposes only and have no legal effect. Thus, embodiments described under different headings may be combined as long as they are not mutually exclusive.

[0119] When amounts, concentrations, dimensions, 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 that can be obtained by combining any upper limit or preferred value with any lower limit or preferred value is also specifically disclosed, regardless of whether the resulting range is expressly stated in the context.

[0120] The following examples illustrate the practice of the present invention in some of its preferred embodiments, but the invention is not limited thereto or by them.

[0121] Example

[0122] Example 1: Depolymerization and reuse of foam

[0123] A glycerin / citric acid (1:1 molar ratio) foam having a degree of polymerization greater than 0.9 and a density of approximately 250 g / l was provided. The foam was provided in the form of chunks with a maximum diameter of 2 cm. The chunks were provided in an autoclave and contacted with steam (approximately 5 bar) at a temperature of 150°C for 2 hours. During the depolymerization reaction, the foam was depolymerized to form a liquid polymer with a degree of polymerization of approximately 0.2. Upon completion of the depolymerization reaction, the liquid polymer composition was removed from the reactor.

[0124] The liquid polymer (resin) can be used to make new foams or can be used as a binder in the same way as fresh resin without compromising functionality (see Example 6).

[0125] Example 2: Panel of particulate matter from depolymerized hemp fiber compressed panels

[0126] A compressed panel comprising a hemp fiber nonwoven mat and 50% by weight of a citric acid / glycerol polymer (1:1 molar ratio) with a degree of polymerization greater than 0.8 was subjected to a size reduction process, resulting in the formation of particles with an average diameter of less than 4 mm. The particles were placed in a depolymerization reactor and contacted with water vapor (approximately 2 bar) at a temperature of 120°C for 2 hours.

[0127] The product of the depolymerization step was a particulate material that still contained the polymer, which had a degree of polymerization of about 0.3.

[0128] The resulting particles were dried at 85°C for 2 hours and then compressed at 145°C for 10 minutes under 15 bar pressure to form a compressed panel of hemp-containing particles with a thickness of 8 mm. The panel was then cured at 160°C for 2 hours. The polymer in the compressed panel had a degree of polymerization of at least 0.8. The resulting panel was smooth and had good physical properties, including a flexural strength of 25 MPa, far exceeding that of commercially available particle board.

[0129] Example 3: Reuse of depolymerized hemp fiber - curved panels as flat hemp fiber panels

[0130] Compressed surface (90%) containing hemp fiber and 50% by weight of citric acid / glycerol polymer (molar ratio 1:1) having a degree of polymerization greater than 0.8. o The density of this panel, which was formerly a chair, was 1.1 g / ml.

[0131] The panel material was fed into a depolymerization reactor and contacted with steam (about 2 bar) for 4 hours at a temperature of about 120°C. After the depolymerization reaction was completed, the previously rigid plate material became flexible. The polymer had a degree of polymerization of about 0.4. The panel material was dried at 80°C for 3 hours. The panel material was then flattened in a press and cured at 145°C and 15 bar pressure for 2 hours to form a smooth, rigid plate material containing a polymer with a degree of polymerization greater than 0.8 and good mechanical properties.

[0132] Example 4: Recycling of fiberglass panels

[0133] A laminated composite panel was prepared containing five woven glass fiber mats and a citric acid / glycerol polymer (1:1 molar ratio) having a degree of polymerization greater than 0.9.

[0134] The panel was fed into a depolymerization reactor and contacted with water (about 6 bar) at a temperature of 150° C. for 1 hour. After the depolymerization reaction was completed, the polymer had a degree of polymerization of about 0.3.

[0135] The liquid polymer was separated from the glass fiber mat by filtration, and the liquid polymer and glass fibers were recovered. The recovered glass fiber mat (which felt and looked the same as a new mat) was combined with the recovered resin (40-60% by weight) and reused to make a new glass fiber composite panel. The composite was then cured at 160°C. The cured polymer had a degree of polymerization greater than 0.8. Although good mechanical properties were obtained, the tensile strength, flexural strength, and flexural elongation were slightly reduced compared to the original panel, reaching approximately 70% of their original values. Without wishing to be bound by theory, this is believed to be due to the removal of the sizing agent during the depolymerization process. In any case, this example demonstrates that panels with good properties can be produced from depolymerized resin and reused glass fibers.

[0136] Example 5: Depolymerization of foam in liquid resin and reuse as a binder for hemp fiber panels

[0137] A glycerin / citric acid (1:1 molar ratio) foam was provided having a degree of polymerization greater than 0.9 and a density of approximately 250 g / l. The foam was provided in the form of a block with a maximum diameter of 2 cm.

[0138] The mass was fed into a depolymerization reactor and contacted with a liquid glycerin / citric acid (1:1 molar ratio) polymer resin having a degree of polymerization of about 0.5 and a water content of 10% by weight. A 50 / 50% by weight mixture of foamed particles / liquid polymer resin and some additional water (equal to the amount of water in the liquid resin) was prepared. The mixture was reacted under reflux at a reaction temperature of about 130°C for 4 hours. At the end of the reaction, a liquid polymer medium with an estimated degree of polymerization of about 0.5 was obtained. It was found that further resin foam could be easily dissolved / depolymerized in the resulting liquid medium.

[0139] The resin thus obtained was used in the manufacture of panels by impregnating a hemp mat with the resin and then curing under pressure in accordance with WO 2022 / 106724, and the properties of the panels were found to be the same as those of panels based on fresh resin.

[0140] Example 6: Recycling of particle board panels

[0141] Panels were provided consisting of wood particles and a citric acid / glycerol polymer (1:1 molar ratio) with a degree of polymerization greater than 0.8 (a typical chipboard composition with small particles on the outside and large particles on the inside, and an overall polymer content of about 15% by weight).

[0142] The panels were fed into a depolymerization reactor where they were contacted with steam at a temperature of about 120° C. (about 2 bar) for 6 hours.

[0143] The panel was soft, swollen, and the resin-bearing particles were loosened. The particles were further loosened using a kitchen mixer and dried in an oven at 85°C for 2 hours.

[0144] Using a sieve, the particles were separated into small and large particles. New panels were made from the recovered particles by sandwiching a layer of larger particles between two layers of smaller particles and subjecting the composite to curing at 145°C and 15 bar pressure for 2 hours. This resulted in new panels based entirely on recycled material. The panels were 2 mm thick. The panels had a smooth surface and good mechanical properties, as evidenced by a flexural strength of 11 MPa.

[0145] The experiment was repeated with the addition of a small amount of polymer (5-20% by weight, calculated from the amount of polymer contained in the panel before recycling). This resulted in a panel with a flexural strength of 14 MPa, the same as the flexural strength of the original panel. Without wishing to be bound by theory, it is believed that during the depolymerization process, some resin may be absorbed by the wood particles, leaving less resin available for particle-to-particle bonding. Adding a limited amount of additional resin helps to provide additional bonding.

Claims

1. 1. A method for treating a polymer-containing material, comprising: providing a starting material comprising a polymer which is a polyester derived from an aliphatic polyalcohol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms, wherein the aliphatic polyalcohol comprises at least 70% by weight of a polyalcohol having at least three hydroxyl groups, and the aliphatic polycarboxylic acid comprises at least 70% by weight of a tricarboxylic acid, and the polyester has a degree of polymerization of at least 0.7, the degree of polymerization being the ratio of the number of reacted functional groups to the maximum number of reactive functional groups; In the depolymerization step, the starting material is contacted with a nucleophile at a temperature of at least 80°C for not more than 24 hours to depolymerize the polymer, resulting in a polymer having a degree of polymerization that is reduced by at least 0.1 compared to the degree of polymerization of the polymer in the starting material and is in the range of 0.1 to 0.8, wherein the nucleophile comprises at least one of water, a liquid polymer that is the polymerization product of an aliphatic polyalcohol having 2 to 15 carbon atoms and an aliphatic polycarboxylic acid having 2 to 15 carbon atoms, and a liquid monomer of the polymer. The method, comprising the steps of:

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

3. 3. The method of claim 1 or 2, wherein the polyester in the starting material has a degree of polymerization of at least 0.8, at least 0.9, or at least 0.

95.

4. 4. The method according to claim 1, wherein, when the nucleophilic agent 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 nucleophilic agent applied in the depolymerization step comprises a plurality of monomers, a mixture of the plurality of monomers has the same composition as the plurality of monomers constituting the polymer in the starting material.

5. 5. The method according to claim 1, wherein the depolymerization step is carried out at a temperature of at least 90°C, in particular at least 100°C, and / or up to 220°C.

6. 6. The method according to claim 1, wherein the degree of polymerization of the polymer after the depolymerization step is in the range of 0.1 to 0.7, in particular in the range of 0.2 to 0.6 or 0.2 to 0.

5.

7. The method of any one of claims 1 to 6, wherein the starting material comprises a filler.

8. The method according to any one of claims 1 to 7, wherein a size reduction step is carried out before or after the depolymerization step.

9. 9. The method according to claim 7 or 8, wherein after the depolymerization step, a step of separating the liquid polymer produced in the depolymerization step from the filler is carried out.

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

11. 11. The method according to any one of claims 1 to 10, wherein the depolymerized polymer-containing mass is subjected to 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.

12. 7. The method according to any one of claims 1 to 6, wherein the polymer-containing starting material is filler-free and the depolymerization step is carried out to a degree of polymerization in the range of 0.1 to 0.7, in particular 0.2 to 0.6, more in particular 0.2 to 0.5, in particular using a liquid polymer-containing nucleophile.

13. 8. The method of claim 7, wherein the formed body of the filled polymer-containing material is subjected to a depolymerization step, followed by a molding step and a curing step.

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