Biodegradable composite structure for artificial leather

Abstract

The present invention relates to a fully biodegradable composite structure, which is in the form of a sheet in a specific form and can be used for producing artificial leather, said composite structure having a surface layer formed with a biodegradable polymer as a polymer component, a composite layer made of a biodegradable polymer composition, the fabric layer is made of a biodegradable textile base material; and the surface layer is made of a biodegradable polymer which can be dispersed in water. The invention also relates to a method for producing such a composite structure, in which the composite structure can impart a desired surface structure, a method for composting the composite structure, and a method for separating the layers of the composite structure, in which the composite structure is treated by an organic solvent, which can selectively dissolve one or more layers in the composite structure.

Description

Technical Field

[0001] This invention relates to a fully biodegradable composite structure in a sheet-like form for use in the manufacture of artificial leather. The composite structure comprises a surface layer formed from a biodegradable polymer as a polymer component, a composite layer made from a biodegradable polymer composition, and a fabric layer formed from a biodegradable textile substrate. The surface layer is made from a water-dispersible or emulsifiable biodegradable polymer. The invention also relates to methods for manufacturing such composite structures (wherein the composite structure can be endowed with a desired surface structure), methods for composting the composite structure, and methods for separating the layers of the composite structure (wherein the composite structure is treated with an organic solvent that can selectively dissolve one or more layers of the composite structure). Background Technology

[0002] Composite materials are sandwich materials formed by combining different materials, and their chemical, physical, and other properties are superior to those of single components. In addition to textile composites, non-woven fabrics, and laminated products (i.e., materials bonded together in a sandwich structure by adhesives or lamination, such as plywood, composite films, and laminates), artificial leather is also classified as a sandwich material.

[0003] Artificial leather is defined as a multi-layered, flexible composite structure, with a surface layer composed of polymers and a base layer typically made of textiles, nonwovens, or foams (such as polyvinyl chloride (PVC), polyolefins (especially thermoplastic polyolefins in TPO form), or polyurethane). The polymer surface layer provides abrasion resistance and fabric strength, and determines the appearance, while the base layer provides the required strength and tensile properties. Materials such as polyurethane are used as coating polymers, which are available in single-component and two-component coating systems.

[0004] European Patent EP 1 059 379 B1 describes, by example, a method for manufacturing a composite structure with a polyurethane surface, wherein the polyurethane is prepared by reacting diisocyanate and / or diisocyanate prepolymers with difunctional and trifunctional polyols. While the use of trifunctional polyols in European Patent EP 1 059 379 B1 ensures sufficient strength in the composite structure, in some cases this may lead to a lack of required flexibility or even undesirable brittleness.

[0005] Another patent relating to the manufacture of traditional synthetic leather is European Patent EP 1 927 466 B1, which uses a coating composition of aliphatic polyol and polyisocyanate as the surface layer. The polyol used in European Patent EP 1 927 466 B1 has at least two CH2 groups at the hydroxyl (OH) end and is sufficiently reactive to be co-processed with polyisocyanate into a reactive coating.

[0006] Traditional synthetic leather produced by this method has high durability and a long service life. While these characteristics are ideal for the use of synthetic leather, they pose significant problems for its disposal, because in most cases the components cannot be separated, and heat recovery methods such as combustion or gasification often become the only way to dispose of it after use.

[0007] In recent years, there has been a significant increase in demand for materials made from renewable raw materials and materials that can be disposed of more quickly and effectively after use. In response, the industry has intensified its research and development efforts, striving to replace at least some of the non-biodegradable raw materials in synthetic leather with biodegradable ones, and to use renewable raw materials in the manufacturing process of synthetic leather wherever possible. However, the manufacture of such synthetic leather faces significant technical challenges due to a reluctance to compromise on its performance characteristics.

[0008] Examples of non-animal-derived bio-based synthetic leather include pineapple leaf leather (such as products known under the "Piñatex®" brand), cork-based leather, apple leather, wine leather, cactus leather, and mushroom leather. Another small startup, Revoltech, has launched a new type of hemp-based bio-based synthetic leather under the brand name "LOVR". TM However, the product has not yet been launched.

[0009] German patent DE 42 28 779 describes a composite material made of a foam material composed of hardened starch foam and another material, wherein the other material may be (but is not limited to) artificial leather. However, only the starch foam portion of this composite material is biodegradable, and its design as a solid foam structure fails to provide the tactile experience required for artificial leather.

[0010] German patent DE 102020210811 A1 describes an artificial leather in which the plastic layer and / or textile substrate are made of a biodegradable biopolymer. When stored at temperatures above 70°C and humidity not less than 80%, at least 50% of the components of this biopolymer degrade into powder within a maximum of 28 days. According to DE 102020210811 A1, both layers of this artificial leather can be made using this biodegradable biopolymer. DE 102020210811 A1 specifically proposes the use of polylactic acid (PLA) as the surface material, which can be processed into a layered structure through calendering or extrusion processes.

[0011] Against this backdrop, the market demands a planar composite structure with good mechanical properties and high abrasion resistance, which can be biodegraded as much as possible within a reasonable timeframe through specific treatment, especially for use in artificial leather. Ideally, this composite structure should be suitable for composting in industrial composting plants.

[0012] This invention fulfills this need. Summary of the Invention

[0013] The research upon which this application is based unexpectedly revealed that such biodegradable composite structures can be prepared by combining a surface layer formed of a biodegradable polymer as a polymer component, a composite layer formed of a biodegradable polymer composition, and a fabric layer formed of a biodegradable textile substrate, while ensuring that the composite structure possesses excellent mechanical properties and performance characteristics. The surface layer uses a water-dispersible or emulsifiable biodegradable polymer, which can be easily prepared into a polymer dispersion and dried.

[0014] Therefore, according to a first aspect, the present invention relates to a fully biodegradable composite structure having at least three layers, particularly in an artificial leather embodiment, comprising: a surface layer formed of a biodegradable polymer as a polymer component, a composite layer formed of a biodegradable polymer composition, and a fabric layer formed of a biodegradable textile substrate, wherein the surface layer is made of a water-dispersible biodegradable polymer.

[0015] In the context of this invention, the term "biodegradable" refers to organic materials that can decompose into carbon dioxide, water, biomass, and mineral salts under aerobic conditions, or into carbon dioxide, methane, biomass, and mineral salts under anaerobic conditions. According to this invention, when using standardized measurement methods conforming to DIN EN 14046:2016 (also published under the designation DIN EN ISO 14855:2013 "Determination of the final aerobic biodegradability of plastic materials under controlled composting conditions"), a degradation rate of at least 50% (preferably at least 70%, more preferably at least 90%) should be achieved within 6 months. The degradation rate is determined by gravimetric method according to DIN EN ISO 14855-2.

[0016] In the context of the composite structure described in this invention, "biodegradable" means that the composite structure contains only biodegradable or biocompatible components. In the context of this invention, "biocompatibility" means that such substances will not be degraded, will not have any negative impact on the microorganisms that degrade the biodegradable components in the composite structure, and will not adversely affect the final compost quality (ecotoxicity testing according to OECD Guideline 208). "Completely biodegradable" means that all layers of the composite structure should meet the biodegradability requirements defined above, i.e., each layer should consist of biodegradable and / or biocompatible components, and under the conditions specified in DIN EN ISO 14855:2013, the biodegradable components should achieve a degradation rate of at least 50% within 6 months.

[0017] "Water-dispersible" means that the polymer can form a stable aqueous dispersion in water, which is stabilized by ionic functional groups in the polymer or by the addition of dispersion stabilizers. If such additives are used, they can still be detected in the surface layer even after drying and curing. Particle size typically ranges from a few nanometers (2 nm) to a few micrometers (10 µm). In emulsions, the polymer raw material particles can be converted to the desired fineness through processes such as grinding, ranging from 100 nm to several hundred micrometers (500 µm), preferably 250 nm to 100 µm, and more preferably 250 nm to 80 µm. These particles can be suspended in the aqueous medium by an emulsifier, but are not necessarily dissolved in the medium.

[0018] Those skilled in the art know of biodegradable polymers that can be used to manufacture surface coatings, and in principle, any biodegradable polymer that can provide the necessary stability properties (especially high abrasion resistance) can be used to manufacture surface coatings. Polymers selected from the group consisting of: polyester polyurethane, polybutylene terephthalate (PBAT), polybutylene succinate, polybutylene adipate, cellulose, cellulose acetate, polycaprolactone, polyhydroxy fatty acid esters (especially in the form of poly-3-hydroxybutyrate (P3HB), poly-4-hydroxybutyrate (P4HB), polyhydroxyvalerate (PHV), polyhydroxyhexanoate (PHH), or polyhydroxyoctanoate (PHO)), polyhydroxy fatty acid ester copolymers (especially in the form of P3HB4HB, P3HB3HV, P3HB3HV4HV, P3HB3Hx, P3HB3HO, or P3HB3HD), polylactic acid, polyvinyl alcohol, starch, and other natural polymers and mixtures thereof. Anionic aliphatic polyester polyurethanes, such as those commercially sold by Covestro under the trade name Impranil DLN, are particularly suitable as polyester polyurethane materials.

[0019] The preferred surface polymers are polybutylene adipate (PBA), polybutylene succinate (PBS), polybutylene adipate-PBS copolymers, and mixtures thereof. PBA is particularly suitable as a surface polymer because it is stable to isopropanol and can form sterilizable surface areas. PBA also possesses properties comparable to polyethylene terephthalate (PET), and colorants such as pigments or carbon black can be easily and uniformly incorporated into the polymer.

[0020] The polymer is used in the form of an aqueous dispersion, which can be coated onto a suitable substrate and form a surface layer after the water evaporates.

[0021] The surface polymer can be made uncrosslinked or crosslinked by adding suitable additives. For example, during the crosslinking process, crosslinking of the polymer with hydroxyl (OH) functional groups can be achieved by adding polyepoxides that are also biodegradable. Such polyepoxides include epoxidized vegetable oils, such as soybean oil, linseed oil, rapeseed oil, castor oil, or karanja oil. Other available biodegradable polyepoxides are based on vanillin or phloroglucinol. These polyepoxides contain aromatic components.

[0022] Indirect cross-linking can also be achieved through ionic interactions and the introduction of alginate and polyvalent cations. Alginate is a polyalgin, an anionic polysaccharide in which each sugar unit has a carboxyl group. They are composed of monomeric subunits D-mannuronic acid and L-guluronic acid in different proportions, as shown in the schematic diagram below.

[0023]

[0024] Depending on the polymer chain length and pH value, these polymers are soluble in water and, in some cases, significantly increase the viscosity of the system.

[0025] Algates include unfunctionalized alginates and functionalized alginates, particularly those functionalized with ethylene glycol. Ethylene glycol-functionalized alginates can be functionalized using ethylene glycol monomers or polymers (preferably ethylene glycol oligomers), with these groups typically attached as side chains to the alginate molecule.

[0026] To achieve the desired crosslinking effect, alginate needs to form a salt complex with a metal or ammonium cation. This mixture can be blended with, for example, an aqueous polyurethane dispersion, subsequently processed into a film and dried. The metal cation is preferably a multivalent cation (especially a divalent metal cation) or a mixture thereof. Suitable multivalent (especially divalent) metal cations for this system include calcium and magnesium ions. Unlike traditional crosslinking methods, when using a combination of alginate and multivalent cations, the polymer itself does not crosslink; instead, a network structure composed of alginate and multivalent cations is formed, with polymer molecules distributed in the free voids of this network structure.

[0027] The polymer is usually the main component of the surface layer, and in practical applications, its content is at least 60% of the total weight of the surface layer on a dry weight basis, preferably at least 70%, and more preferably about 75% to 98% of the total weight of the surface layer.

[0028] Furthermore, as mentioned above, a colorant can be added to the surface layer to change it to an opaque color. Those skilled in the art are familiar with pigments and other colorants that can be used for this type of coloring, including biodegradable carbon blacks (such as BASF's Xfast® Black 0066 or Living Ink Technologies' Algae Black Pigment).TM Grade J1 and calcium carbonate, which provides a white visual effect, can be used as colorants. Other colorants that can be used for surface coloring include phycocyanin or effect pigments, such as biodegradable glitter powders (such as Sigmund Lindner's SiLiglamNATURE, SiLiglam PURE NATURE, or SiLiglam PURE Bio Sparkle) or biocompatible iron oxide.

[0029] The amount of colorant added should be appropriate to achieve the desired color effect, with a suitable addition range of 0.5% to 20% (by weight), a particularly suitable range of 4% to 10% (by weight), and more preferably 5% to 8% (by weight). All weight specifications mentioned in this specification refer to the dry weight of the surface layer.

[0030] According to the present invention, other additives may be added to the surface layer of the biodegradable composite structure, such as biodegradable defoamers (e.g., BYK-1740) or biodegradable dispersants (e.g., Schwego® wett 6267 and 8319 (Schwegmann), TEGO® Dispers 658 (Evonik), or Emulan® TO 2080 (BASF)). Another class of additives that can be added to the surface layer are softeners, such as cashew nut shells (CD, derived from renewable natural cashew nut shells), triethyl citrate (TEC), acetylated tributyl citrate (ATBC), epoxidized soybean oil (ESO), L-lactide, polyethylene glycol (PEG), glycerin, triacetin, sorbitol, or Roquette's Polysorb® ID46. The selection of softeners can, on the one hand, reduce the glass transition temperature to the range of approximately -40 to +30°C, and on the other hand, inhibit the formation of crystal structures, thereby avoiding the white fracture phenomenon that may occur when the crystalline material is bent. Fillers, such as calcium, magnesium, or other metal-based carbonates and oxides, may also be added to the surface layer. Furthermore, thickeners may be added to the surface layer of the biodegradable composite structure described in this invention, particularly in the form of alginate thickeners combined with monovalent metal cations (such as sodium, potassium, or ammonium ions).

[0031] In the composite structure described in this invention, the thickness design of the surface layer must take into account the mechanical strength requirements against external influences. On the other hand, those skilled in the art will strive to control the surface layer thickness within a necessary range, because an excessively thick, dense surface layer cannot provide a soft, leather-like feel. Therefore, the surface layer's weight per unit area is preferably controlled between 10 and 200 g / m². 2 Within the range, more preferably within the range of 30 to 100 g / m 2 When the surface layer has a dense structure and the dry surface material density is approximately 1-1.3 g / cm³, 3When the thickness of the surface layer is in the range of approximately 10 to 260 µm, the preferred range is 30 to 130 µm.

[0032] As mentioned above, the surface layer is preferably designed as a dense layer (i.e., free from any significant gas inclusions).

[0033] In the composite structure of this invention, the "composite layer" serves to bond the surface layer or other layers coated on the surface layer to a biodegradable textile substrate. Bonding to the biodegradable textile substrate can be achieved by applying a liquid composite compound to the surface of the layer, followed by embedding the textile substrate at least partially into the composite layer. By curing the composite compound (e.g., by evaporating the solvent or dispersion medium (water)), the textile substrate is then anchored by the composite layer to the surface layer or other layers coated on the surface layer. The composite compound does not necessarily need to be an adhesive, as bonding can also be achieved through partial embedding via mechanical action. Adhesive meshes or adhesive felts that melt at a specific temperature and bond the polymer layers to the textile substrate under pressure can also be used. Such materials can also be used as hot melt adhesives. Depending on the polymer chain length, the aforementioned biodegradable polymers can also be used for this purpose.

[0034] In the context of this invention, the composite layer is preferably composed of a biodegradable polymer, which can also be used as a surface layer. Since the composite layer in the composite structure described in this invention typically has an invisible function, it is preferably formulated to be free of colorants. In one embodiment, the composite layer may consist of only a single biodegradable polymer or a mixture of multiple biodegradable polymers.

[0035] In another embodiment, the composite layer contains, in addition to a biodegradable polymer, a biocompatible flame retardant. Such biocompatible flame retardants include, but are not limited to, calcium alginate or metal hydroxides (such as aluminum hydroxide, magnesium hydroxide), zeolite, clay, or silica.

[0036] Additives that promote the growth of bacteria and microorganisms can also be added to the covering film, foam layer, intermediate layer, and composite layer. These additives may contain sugars, proteins, composting accelerators (such as nitrogen compounds, potassium, lime, various trace elements, and horn or bone meal), and cellulose components.

[0037] In principle, all of the above-mentioned biodegradable polymers suitable for the surface layer can be used in the composite layer. In a particularly preferred embodiment, the composite layer uses polybutylene terephthalate (PBAT) as a biodegradable polymer, especially processed in the form of an aqueous dispersion.

[0038] The third component of the composite structure described in this invention is a biodegradable textile substrate. Those skilled in the art are familiar with biodegradable textile substrates, and in principle, any known biodegradable textile substrate can be used to manufacture the composite structure described in this invention. In the context of this invention, preferred biodegradable textile substrates include those made from PBAT, polyvinyl alcohol, polylactic acid (PLA), cotton, cellulose, or other renewable raw materials, wherein the renewable raw materials are particularly selected from flax fibers, hemp fibers, pineapple fibers, or wool. Furthermore, the biodegradable textile substrate may also employ a biodegradable spacer fabric with irregularly arranged fibers.

[0039] In one embodiment, the biodegradable composite structure of the present invention is made of a transparent surface layer and a composite layer through which the biodegradable textile substrate is visible. In this case, additives that affect transparency or generate bubbles should be avoided in the formulation of the composite layer and the surface layer. To enable the composite structure to possess the required resistance to external mechanical stress, the surface layer of such a composite structure may also have a thicker structure than described above, for example, with a basis weight ranging from 100 to 300 g / m². 2 Or 150 to 280 g / m 2 .

[0040] In another preferred embodiment, the composite structure of the present invention incorporates a foam layer between the surface layer and the composite layer, giving the composite structure a softer feel. This foam layer is preferably made of a biodegradable polymer-based foam material, which is mixed with gas and coated in foam form, wherein the foam layer is formed through curing.

[0041] All of the aforementioned polymers suitable for the surface layer can be used as biodegradable polymers for the foam layer. The content of biodegradable polymers in the foam layer is typically lower than that in the surface layer, especially when the foam layer contains flame-retardant components; its content (based on the dry weight of the foam layer) is preferably 30% to 70% (by weight), more preferably 45% to 65% (by weight). Furthermore, the aforementioned optional additives and mixtures used in the preparation of the surface layer can also be used in the foam layer. Preferred fillers for the foam layer include polymer powders, particularly PBAT powder, calcium carbonate, clay, or zeolite. In addition, it is ideal to incorporate a thickener (especially an alginate thickener, most preferably sodium alginate) into the foam layer. Simultaneously, biodegradable soaps or foaming aids can be added to the foam layer. For example, stearate compounds can be used, whose counterions can be sodium, potassium, or nitrogen-containing compounds (such as ammonia). Ammonium stearate, in particular, has excellent biodegradability.

[0042] The density of this foam is typically significantly different from that of the denser layers, such as the surface layer, ensuring that the foam is easily compressible under stress. The lower density also ensures a relatively low weight for the composite structure. Therefore, to provide good tactile properties, the density of the foam layers can be set between 200 and 900 g / m³. 3 Between 300 and 800 g / m 3 In a particularly preferred embodiment, the foam employs an open-cell structure, which not only provides a softer feel but also offers the added advantage of improved biodegradability of the composite structure. This is because degrading bacteria can easily penetrate the foam's interior through the open-cell structure and decompose it from within.

[0043] Of course, the foam layer can also have a dense structure, in which case it can be described as an intermediate layer. Due to different filler ratios, the density difference of the foam layer may reach or exceed that of the surface layer.

[0044] When preparing the foam layer, additives suitable for the foam components can be added, especially biodegradable foam stabilizers, such as Ortegol P1 (Evonik), sodium cocoyl isopropionate (Innospec's Pureact I-78C), or ammonium stearate with the trade name Stokal STA (Bozeto).

[0045] If the composite structure of the present invention includes a foam layer, the thickness of the foam layer is preferably designed to be greater than that of the surface layer and the composite layer. Therefore, it is more advantageous when the basis weight of the foam layer in the finished composite structure is 1.5 to 5 times the basis weight of the surface layer and / or the composite layer. The basis weight of the foam layer is particularly preferably 2.5 to 4 times the basis weight of the surface layer and / or the composite layer. Specifically, the basis weight of the foam layer in the composite structure of the present invention can be set to 20 to 500 g / m³. 3 Within this range, the basis weight of the biodegradable textile substrate may even be higher than that of the foam layer in the composite structure. In one embodiment, it may account for 5% to 80% of the total weight of the composite structure of the present invention, preferably 30% to 70%.

[0046] Because the basis weight may be high, additives that improve flame retardant properties can be incorporated into the foam layer, especially the aforementioned substances related to the composite layer. In addition, other additives conventionally used to optimize and control such foam properties can be incorporated into the foam layer, such as pigments, crosslinking agents, or thickeners. Considerable crosslinking agents include the aforementioned ionic crosslinking systems related to the surface layer, or crosslinking achieved through the reaction of epoxy groups contained in the foam layer polymer with hydroxyl groups (OH).

[0047] The thickness of the existing foam layer can be adjusted within a suitable range, typically set to 0.1 to 1 mm, preferably 0.15 to 0.6 mm, and more preferably 0.2 to 0.4 mm.

[0048] To achieve an aesthetically pleasing visual effect, the surface layer preferably employs an embossed or matte finish. This surface finish can be a regular pattern or other structured regularity. In the context of this invention, "matte" refers to a surface finish that evokes the appearance of the front of animal leather, or a surface finish that evokes the appearance of split leather. Such a structure enables the composite structure to exhibit a high-quality texture similar to leather.

[0049] In addition to the components specifically described in the above descriptions, all of the above layers may also contain additives that promote bacterial decomposition and thus achieve biodegradation. Such substances include, in particular, starch, modified starch, yeast or yeast extract, and salts (especially ammonium salts, phosphates, magnesium salts, calcium salts and iron salts, as well as nitrates or sulfates).

[0050] The aforementioned composite structure is biodegradable and exhibits high wear resistance even without an additional coating layer. Furthermore, the preparation of this type of composite structure is relatively simple, as each layer can be obtained through a simple coating process followed by drying.

[0051] However, to improve and optimize the final properties, the composite structure can still be modified with one or more coating layers. Suitable materials for forming such coatings (note that the coating should also be biodegradable) include: inorganic-organic hybrid polymers, such as materials traded under the name bioORMOCER®; and biopolymer-based coatings, particularly those based on hemicellulose and / or polyvinyl alcohol.

[0052] If the composite structure of the present invention includes a paint layer, the number of paint layers is preferably no more than four; the composite structure of the present invention is particularly preferably having one or two paint layers.

[0053] Furthermore, the composite structure described in this invention preferably not only possesses biodegradability but also meets the compostability requirements specified in DIN EN 14995:2003. This ensures that the composite structure can decompose within a reasonable time in an industrial composting plant. In terms of performance characteristics, especially when the composite structure is synthetic leather, it is even more preferable that its abrasion resistance meets DIN EN 5470-2, achieving at least 50,000 cycles, and more preferably at least 100,000 Martindale abrasion cycles. Furthermore, it is even more ideal if the composite structure described in this invention can meet the flame retardant requirements of FMVSS 302 by adding suitable flame retardants and using flame-retardant fabrics.

[0054] The biodegradable composite structure described in this invention can also be used in conjunction with hook and loop fasteners, which can also be made of biodegradable materials. This design allows for the selective replacement of the attachment layer on the composite structure via hook and loop fasteners; or, the composite structure itself can serve as a replaceable layer and be fixed to the substrate via hook and loop fasteners.

[0055] To further improve biodegradability, the composite structure described in this invention can also be locally weakened by structural treatment methods (such as mechanical punching, laser ablation or water jet cutting) to introduce specific local degradation areas or preset fracture points.

[0056] The composite structure described in this invention can be widely applied to all application scenarios currently using non-biodegradable artificial leather or textured surface covering materials. This composite structure is particularly suitable for automotive passenger compartment interiors, such as car seats, door panels, or dashboards, and is also applicable to the furniture manufacturing industry.

[0057] In another technical solution, the present invention also relates to a method for manufacturing the above-mentioned biodegradable composite structure, the method comprising the following steps:

[0058] (i) A water-based polymer dispersion and any additives that may be contained therein are coated onto the surface of a substrate and dried to form a surface layer;

[0059] (ii) If necessary, polymer foam can be coated onto the surface layer obtained in step (i) and dried or cured to form a foam layer;

[0060] (iii) A composite layer is coated on the surface layer of step (i) or the foam layer of step (ii), and a biodegradable textile substrate is embedded in the composite layer. The preparation is completed by drying or curing.

[0061] (iv) Remove the substrate to obtain a biodegradable composite structure.

[0062] In the above method, all layers of the biodegradable composite structure are preferably prepared using an aqueous dispersion to avoid the release of volatile organic compounds (VOCs).

[0063] The drying process in steps (i) to (iii) can be completed in a dedicated oven. Because this composite structure is prepared through a continuous coating and drying process, this method exhibits excellent performance in terms of material utilization, production efficiency, and energy consumption, significantly reducing the manufacturing cost of the composite structure. The temperature range under typical drying conditions is usually 70-210°C. The exposure time of each layer in the high-temperature environment can be flexibly set from 20 to 120 seconds.

[0064] In step (i), the substrate used for coating the polymer dispersion is preferably paper or film with a negative structure that simulates the desired surface structure of the surface layer. In a particularly preferred embodiment, the substrate has regularly arranged surface structure regions, or is designed with a surface structure that simulates the negative structure of leather texture.

[0065] As an alternative, the desired surface structure can also be formed in the manufacturing process following step (iv): that is, using a planar substrate in step (i), and after completing step (iv), forming regular structural areas or a surface structure simulating a negative leather texture on the surface of the composite structure through an embossing process. Specifically, this can be achieved by embossing with steel or silicone rollers, or by using a mold through a vacuum process—for example, imprinting the leather texture onto the surface under heating conditions of 100-280°C. Press forming of such structures is also feasible.

[0066] In the method, the coating process can be performed before step (i) or after step (iv). Specifically, at least one coating layer can be applied to the composite structure in two ways: the coating layer is applied to the substrate before step (i), followed by the application of a polymer dispersion to the surface of the coating layer; or the coating layer is applied to the surface of the composite structure after step (iv).

[0067] After its intended use, the composite structure can be decomposed through composting, and the scraps or waste generated during its production (such as unusable covering material fragments) can also be composted. Therefore, another technical solution of the present invention relates to a composting method for the above-mentioned biodegradable composite structure, which is implemented in an industrial composting plant. As an alternative, the composite structure described in the present invention can also be used in biogas plants (for anaerobic degradation) or degraded in other environments, such as landfills, home composting, soil, freshwater, and seawater environments.

[0068] If the different layers of the composite structure are composed of polymer materials with different solubility properties, selective dissolution can be used to separate specific layers from other layers, allowing for individual reuse or recycling of the separated materials. Therefore, another technical solution of the present invention relates to a composite structure processing method that uses an organic solvent to treat the composite structure, wherein the solvent can selectively dissolve one or more layers of the composite structure. Typical examples of composite structures suitable for this method include a composite structure composed of a polyester polyurethane (PU) layer and a polybutylene terephthalate (PBAT) layer, wherein PBAT is soluble in ethyl acetate but insoluble in isopropanol, while the polyester polyurethane is soluble in isopropanol but insoluble in ethyl acetate. Since the cellulose fabric layer is insoluble in either of the aforementioned solvents, it can also be selectively separated from other layers of the composite structure. In a particularly preferred embodiment, the composite structure of the present invention comprises the following structure: the surface layer and composite layer are based on polybutylene terephthalate as the polymer component (preferably without other polymer components), and the foam layer is based on polyurethane (especially polyester polyurethane) foam material. Detailed Implementation

[0069] The present invention will be further described below through exemplary embodiments, but these embodiments should not be regarded as any limitation on the scope of protection of the present invention:

[0070] Example 1:

[0071] A composite structure comprising a surface layer, an intermediate coating as a foam layer, a composite coating (as the "composite layer"), and a textile substrate was prepared according to the following method: The surface layer mixture was coated onto a carrier paper and then dried in an oven at 120°C and 200°C for 1 minute each. The intermediate coating was then applied to the surface layer and dried at 80°C and 150°C for 1.5 minutes each. After applying the composite layer, a fabric layer was embedded in the composite layer, and the entire composite structure was then dried at 100°C and 150°C for 2 minutes each.

[0072] The specific composition of each coating is shown in Table 1:

[0073]

[0074] The composite material prepared according to the above process was tested for abrasion resistance according to DIN EN ISO 5470-2 (Martindale method). MD100 and cotton canvas 10 abrasion-resistant fabrics obtained a grade 1 result after 100,000 abrasion cycles.

Claims

1. A fully biodegradable composite structure comprising at least three layers, particularly suitable for the field of artificial leather, the structure comprising: A surface layer formed from biodegradable polymers as polymer components; Composite layer made of biodegradable polymer composition; A fabric layer formed from a biodegradable textile substrate; wherein the surface layer is made of an aqueous dispersible biodegradable polymer.

2. The biodegradable composite structure according to claim 1, characterized in that, It also includes densities ranging from 200-900 kg / m³. 3 (Preferred weight: 300-800 kg / m³) 3 A foam layer, wherein the foam in the foam layer is preferably an open-cell structure foam.

3. The biodegradable composite structure according to claim 2, characterized in that, The foam layer is formed between the surface layer and the composite layer, and / or on the side of the textile substrate away from the composite layer.

4. The biodegradable composite structure according to any one of claims 1-3, characterized in that, The biodegradable polymer in the surface layer is selected from the group consisting of: polyester polyurethane, polybutylene adipate, polybutylene succinate, dibutylene adipate, cellulose, cellulose acetate, polycaprolactone, polyhydroxy fatty acid esters (especially in the form of poly-3-hydroxybutyrate (P3HB), poly-4-hydroxybutyrate (P4HB), polyhydroxyvalerate (PHV), polyhydroxyhexanoate (PHH) or polyhydroxyoctanoate (PHO)), polyhydroxy fatty acid ester copolymers (such as P3HB4HB, P3HB3HV, P3HB3HV4HV, P3HB3Hx, P3HB3HO, P3HB3HD), polylactic acid, polyvinyl alcohol, starch and other natural polymers and mixtures thereof, preferably in the form of polybutylene adipate.

5. The biodegradable composite structure according to at least one of the preceding claims, characterized in that, The surface layer is enhanced by cross-linking treatment. The cross-linking method is preferably achieved by alginate incorporated into the surface layer to form a cross-linked structure through ionic interactions, or by a reaction between biodegradable epoxy resin and hydroxyl (OH) groups contained in the biodegradable polymer in the surface layer.

6. The biodegradable composite structure according to at least one of the preceding claims, characterized in that, The surface layer also contains biodegradable or biocompatible pigments, preferably selected from carbon black, phycocyanin, iron oxide, or effect pigments (such as pearlescent pigments); and / or the foam layer contains a foam stabilizer (preferably ammonium stearate); and / or a flame retardant, preferably selected from a combination of calcium alginate, aluminum hydroxide, or magnesium hydroxide.

7. The biodegradable composite structure according to at least one of the preceding claims, characterized in that, The surface has a structured or frosted surface texture, preferably simulating the texture of leather.

8. The biodegradable composite structure according to at least one of the preceding claims, characterized in that, The textile substrate is made of polylactic acid (PLA), cotton, cellulose or other renewable raw materials, particularly selected from flax, hemp, pineapple or wool.

9. The biodegradable composite structure according to at least one of the preceding claims, characterized in that, It also contains one or more layers of coating film, preferably based on inorganic-organic hybrid polymers (bioORMOCER®) and biopolymers (especially hemicellulose-based) and / or polyvinyl alcohol-based materials.

10. The biodegradable composite structure according to at least one of the preceding claims, characterized in that, It meets the compostability requirements of DIN EN 14995:2003 and / or has an abrasion resistance of at least 100,000 Martindale abrasion cycles according to DIN EN 5470-2.

11. A method for manufacturing a biodegradable composite structure according to any one of claims 1 to 10, comprising the following steps: (i) A water-based polymer dispersion and any additives that may be contained therein are coated onto the surface of a substrate and dried to form a surface layer; (ii) If necessary, polymer foam can be coated onto the surface layer obtained in step (i) and dried or cured to form a foam layer; (iii) A composite layer is coated on the surface layer of step (i) or the foam layer of step (ii), and a biodegradable textile substrate is embedded in the composite layer. The preparation is completed by drying or curing. (iv) Remove the substrate to obtain a biodegradable composite structure. Preferably, a substrate with a flat surface is used in step (i), and the composite structure is embossed after step (iv) to form a structured surface or a surface structure simulating a negative leather texture; or, in step (i), a substrate with the desired negative surface structure (especially a negative structure simulating a leather texture) is surface treated to form a surface structure.

12. The method according to claim 11, characterized in that, At least one lacquer layer can be applied to the composite structure in two ways: before step (i), the lacquer layer is applied to the substrate, and then the polymer dispersion is applied to the surface of the lacquer layer; after step (iv), the lacquer layer is applied to the surface of the artificial leather.

13. Use of the composite structure according to any one of claims 1 to 10, wherein the composite structure can be used as an interior material for an automotive passenger compartment or as a furniture covering material.

14. The composting method for the biodegradable composite structure according to any one of claims 1 to 10, characterized in that, The composting process is carried out in an industrial composting plant.

15. The method for layering a biodegradable composite structure according to at least one of claims 1 to 10, wherein, The composite structure is treated with an organic solvent that can selectively dissolve one or more layers in the composite structure.

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