Bio leather replacement material comprising bacterial cellulose fibres

Abstract

The invention relates to a bio leather replacement material (10), comprising a flat material on the basis of bacterial nanocellulose (BNC) (14) and sericin, the bacterial nanocellulose (14) having a surface coating on the basis of the protein sericin. The invention also relates to a method for producing same and to its use as a cover material. The invention furthermore relates to a vehicle having an interior covered with a bio leather replacement material (10) of this type.

Description

[0001] Description

[0002] Bio-leather substitute material comprising bacterial cellulose fibers

[0003] The invention relates to a bio-leather substitute material comprising a material based on bacterial nanocellulose (BNC) and sericin, and its use as a cover material.

[0004] In addition, the invention relates to a method for producing the bio-leather substitute material comprising a material based on bacterial nanocellulose (BNC) and sericin.

[0005] Leather is used, among other things, as a covering material for automotive interiors, for example, car seats, and is valued as a durable, visually appealing, and overall high-quality material. However, the production of genuine leather covering material involves complex processing steps, in which the raw leather is processed through a comprehensive sequence of processes (soaking, liming, pickling, tanning, and finishing) until it is ready for use as a leather covering material. This processing is energy-intensive and involves the use of process chemicals, which represent an ecological burden. Furthermore, genuine leather is an animal product.

[0006] Synthetic leather is a type of imitation leather. The basic idea behind the use of synthetic leather is to avoid real leather, an animal product, and to address the environmental problems caused by genuine leather production. However, the plastic polyvinyl chloride (PVC) or polyurethane (PU) used in synthetic leather is petrochemical-based and therefore a non-renewable raw material or a finite resource. Furthermore, the phthalate plasticizers used in synthetic leather are suspected of having adverse effects on human health. Furthermore, synthetic leather, as a composite material, is difficult to reuse.

[0007] Various alternative and sustainable bio-covering materials are known that can be obtained from natural resources such as plants, fungi, and microorganisms. For example, the biocomposite from Malai, which is made from completely organic and sustainable bacterial cellulose grown on agricultural waste from the coconut industry in South India, or nanocellulose, which is a natural, renewable biopolymer made from pure cellulose and biotechnologically obtained from a sugar solution (manufactured, for example, by JeNaCell®, Germany). Materials based on bacterial cellulose (manufactured, for example, by ScobyTec GmbH, Germany) are also suitable as alternative bio-leather substitutes. For example, it is known from KR 10219211 B1 that bio-leather substitutes can be produced using bacterial cellulose fibers.The bio-leather substitute material has a specific content of soy protein fraction and bacterial cellulose fibers modified with a hydroxyl-containing compound to improve durability and flexibility, making the material suitable for the production of clothing, furniture, building materials, or as automotive interior materials.

[0008] WO 2022 / 177528 A1 discloses fabrics coated with bio-leather substitutes. These are obtained by decomposing a cellulose layer produced by microorganisms and adding the necessary active ingredients to obtain a biopolymer filler. This filler is applied to a surface such as paper, fabric, reflective fabric, polyester, or silk fabric by pressing and laminating.

[0009] WO 2022 / 177529 A1 describes a bio-leather substitute that can be used as a replacement for animal hides and synthetic leather. It is physically and visually similar to genuine leather, contains no chemicals, and contains cellulose produced by microorganisms. This bio-leather substitute is produced using a bacterial weaving process and can decompose quickly in the soil, making it highly environmentally friendly and boasting high tensile strength and mechanical strength.

[0010] However, current sustainable leather alternatives often fail to meet the requirements for durability and resilience. Plasticizers used for post-treatment lead to permanently increased odor emissions and are therefore also unsuitable for use in the automotive sector. Cross-linking plasticizers, like textile softeners, do not penetrate deep enough into the compact cellulose layer to improve the material's properties. Furthermore, the plasticizers used can have negative effects on human health.

[0011] The invention is based on the object of providing a resilient, visually appealing and overall high-quality organic leather substitute material which, compared to the prior art, can be produced with reduced energy consumption and is associated with reduced ecological impact and, at the same time, at least partially overcomes the disadvantages of known leather materials and artificial leather materials from an ecological point of view.

[0012] This object is achieved in the present invention by the features of the characterizing part of patent claim 1. It is provided that a bio-leather substitute material comprises a sheet-like material based on bacterial nanocellulose (BNC), wherein the bacterial nanocellulose has a surface coating based on the protein sericin.

[0013] The bio-leather substitute material according to the invention is characterized by improved tensile strength, flexibility, high mechanical stability, a softer surface texture, and water-repellent properties. The bio-leather substitute material according to the invention can also prevent skin irritation in the user. The bio-leather substitute material according to the invention thus represents a sustainable leather alternative that does not contain harmful and odor-emitting plasticizers and is a durable, visually appealing, and overall high-quality material. It reduces the use of non-renewable raw materials by using renewable raw materials. At the same time, the ecological disadvantages of the leather and synthetic leather materials known from the prior art are largely overcome.The invention therefore represents a reduction in the ecological footprint of conventionally used leather or artificial leather and provides a covering material with leather quality.

[0014] According to the invention, the bacterial nanocellulose has a coating of adsorptively bound sericin on its surface. The sericin is thus physically embedded in the bacterial cellulose and can act there on the surface.

[0015] This achieves the mechanical strength of the organic leather substitute material as well as a change in texture and feel. Furthermore, the use of sericin in the inventive organic leather substitute material has the advantage of being available in large quantities as a natural raw material source, as it is currently a by-product of silk cocoon processing, thus offering great potential in the field of circular economy.

[0016] The above-mentioned object is also achieved by a method for producing the bio-leather substitute material according to the invention, wherein bacterial nanocellulose is first subjected to static or dynamic cultivation and a sheet material thus produced is subsequently coated with sericin in a further step.

[0017] The above statements concerning the organic leather substitute material according to the invention also apply accordingly to the process according to the invention.

[0018] The process according to the invention significantly improves the material properties of the bacterial nanocellulose, allowing it to be further processed into a leather-like material. A softer surface texture is obtained, which optimizes the tensile strength, thus making the material according to the invention suitable for use as a user-friendly and durable material in vehicle interiors.

[0019] Further preferred embodiments of the invention emerge from the remaining features mentioned in the subclaims.

[0020] According to the invention, the bacterial nanocellulose has a surface coating based on the protein sericin.

[0021] Sericin is a silk protein and a naturally water-soluble glycoprotein obtained from raw silk. Silk threads consist of two fibroin filaments coated with sericin. The production of silk threads by the silkworm Bombyx mori is widespread. Sericin is extracted from this silkworm's cocoons, for example, by autoclaving at 121°C with distilled water. Sericin is a macromolecule with strong polar groups such as hydroxyl, carboxyl, and amino groups, which promote crosslinking, copolymerization, and polymer reactions. Sericin dissolves in water at temperatures of 50 to 60°C and develops a gel-like consistency upon reaction with other polymers.

[0022] In a first embodiment of the bio-leather substitute material according to the invention, the sheet material can comprise a nonwoven made of bacterial nanocellulose (BNC).

[0023] The BNC fleece can be used as a flat product for the production of organic leather substitute materials.

[0024] Bacterial nanocellulose (BNC) can be obtained through the biochemical polymerization of low-molecular-weight building blocks such as glucose using acetic acid bacteria. BNC differs significantly in its morphology from plant-derived cellulose. It consists of fibers with a diameter in the nanometer range (20 nm to 100 nm), which are 100 times finer than conventional plant cellulose fibers. The natural nanofiber network exhibits a scaffold structure comparable to human tissue. It contains up to 99% water and is capable of intensive interactions with its environment. BNC is mechanically stable even in moist conditions. BNC is a highly pure polymer, free of accompanying plant components such as lignin, pectin, and hemicelluloses. It is characterized by a high molecular weight (degree of polymerization of approximately 4,000 to 10,000) and high crystallinity (80% to 90%).

[0025] BNC fleeces can be produced through static or dynamic cultivation at an ambient temperature of 20°C to 30°C. Static cultivation requires between 12 and 14 days at 30°C until a thickness of 1.5 cm is reached. With longer growth, the layer thickness increases further, reaching a layer thickness of 4 to 5 cm. Dynamic cultivation takes place with a consistent oxygen supply over a period of 4 to 5 days.

[0026] In a further embodiment, the BNC fleece has a residual moisture content of 20% to 50%, preferably 25% to 40%, based on the total weight.

[0027] In a preferred embodiment of the organic leather substitute material according to the invention, the BNC fleece contains at least one plasticizer.

[0028] Suitable plasticizers include polyethylene glycols (PEG), acrylated epoxidized soybean oil (AESO), lecithin or glycerol.

[0029] It was found that the addition of a plasticizer can significantly improve the flexibility and resilience of the BNC fleece.

[0030] In a further preferred embodiment of the bio-leather substitute material according to the invention, the BNC fleece contains one or more cross-linking reagents.

[0031] Suitable cross-linking agents include citric acid, glutaraldehyde, tannic acid, or other vegetable tanning agents such as those from oak bark, mimosa bark, quebracho wood, or sumac leaves. Cross-linking agents can bind the sericin to the fiber surface of the bacterial nanocellulose. This makes it possible to improve textile properties such as softness, elasticity, stability, and durability, as well as surface cleaning.

[0032] In a further preferred embodiment of the organic leather substitute material according to the invention, the BNC fleece contains one or more fillers.

[0033] Suitable fillers include polyvinyl alcohol or chitosan and their mixtures.

[0034] By adding one or more fillers, the material can be further strengthened to ensure improved grip.

[0035] A further aspect of the invention is the use of the bio-leather substitute material according to the invention for the production of covering materials, in particular bio-leather substitute materials for vehicle interiors.

[0036] The various embodiments of the invention mentioned in this application can be advantageously combined with one another, unless otherwise stated in the individual case.

[0037] The invention is explained below in exemplary embodiments with reference to the accompanying drawings. They show:

[0038] Figure 1 is a schematic representation of an embodiment of the method for

[0039] Production of the bio-leather substitute material according to the invention,

[0040] Figure 2 shows a schematic representation of further embodiments for producing the bio-leather substitute material according to the invention and

[0041] Figure 3 shows a further schematic representation of further embodiments for

[0042] Production of the inventive organic leather substitute material.

[0043] Figure 1 shows the production of bacterial nanocellulose (BNC) using acetic acid bacteria, for example, Komagataeibacter xylinus, on the surface of a nutrient medium 12, metabolizing carbon and nitrogen. Cultivation in the nutrient medium 12 is carried out according to a known method, with the nutrient medium 12 consisting of D-glucose as a carbon source (20 g / L), bactopeptone (5 g / L), yeast extract as a nitrogen source (5 g / L), as well as disodium hydrogen phosphate dihydrate (2.7 g / L), and citric acid monohydrate (1.15 g / L) (S. Hestrin et al.: "Biochem. J." 58 [2] (1954), 345-352).

[0044] After static or dynamic cultivation 18, the cultured bacterial nanocellulose 14 can be harvested as a BNC fleece 16 and then purified with a 0.1 M NaOH solution and distilled water, alternating in at least two, preferably three to four, wash steps 20. The bacterial nanocellulose 14 is further processed uncomminuted as a BNC fleece 16. After purification 20, post-treatment 22 with a sericin solution S takes place. In a final step, the BNC fleece 16 is dried.

[0045] Figures 2 and 3 show further embodiments of the post-treatment step 22.

[0046] To produce the surface coating, the BNC fleece 16 is placed in a sericin solution S with a concentration of 1 to 100 mg / mL, preferably 15 to 20 mg / mL, for 1 to 7 days, preferably 3 to 5 days 24 (Figure 2).

[0047] Alternatively, the surface coating with sericin can also be carried out by applying 26 the sericin solution S to the surface of the BNC fleece 16 by spraying, brushing or brush application or immersion for 5 to 100 seconds, preferably 10 to 20 seconds (Figure 2).

[0048] In a further embodiment, the BNC nonwoven 16 is first treated with a plasticizer by soaking 28. A crosslinker can be added for stabilization. Sericin dissolved in distilled water is then applied to the surface 26 by spraying, brushing, or briefly immersing it for 5 to 100 seconds, preferably 10 to 20 seconds (Figure 3).

[0049] In an alternative embodiment, the BNC nonwoven 16 is first treated with a plasticizer by immersion 28. A crosslinker can be added for stabilization. Subsequently, the BNC nonwoven 16 is immersed 24 in a sericin solution for 1 to 7 days, preferably 3 to 5 days (Figure 3).

[0050] In another embodiment, the BNC nonwoven 16 can be immersed in a solution of sericin and plasticizer. The crosslinker can also be added. In a further step, the sericin coating is dried and finally cured in an oven at 90°C to 110°C, preferably 95°C to 105°C, for 12 to 24 hours.

[0051] In a further embodiment, a filler can also be added to the plasticizer and / or crosslinker.

[0052] If necessary, further surface coatings are possible in subsequent steps.

[0053] In an alternative or additional embodiment of the method according to the invention, in step 18 and / or 20, before treatment with sericin 22, the material is stained.

[0054] It was found that increasing the protein content in the finishing solution can increase the color intensity after dyeing.

[0055] List of reference symbols Bio-leather substitute material Culture medium cultivated bacterial nanocellulose BNC fleece static or dynamic cultivation Purification Post-treatment step Immersion in sericin solution Application of the sericin solution Treatment with plasticizer and crosslinker

Claims

Patent claims 1. Bio-leather substitute material (10) comprising a sheet-like material based on bacterial nanocellulose, BNC, (14), characterized in that the bacterial nanocellulose (14) has a surface coating based on the protein sericin.

2. Bio-leather substitute material (10) according to claim 1, characterized in that the sheet material comprises a fleece (16) made of bacterial nanocellulose (14).

3. Organic leather substitute material (10) according to claim 1 or 2, characterized in that the BNC fleece (16) contains at least one plasticizer.

4. Bio-leather substitute material (10) according to one of the preceding claims, characterized in that the BNC fleece (16) contains one or more cross-linking reagents.

5. Organic leather substitute material (10) according to one of the preceding claims, characterized in that the BNC fleece (16) contains one or more fillers.

6. A method for producing a bio-leather substitute material (10) according to claim 1, characterized in that bacterial nanocellulose (14) is first subjected to a static or dynamic cultivation (20) and a sheet material produced in this way is then coated with sericin in a further step (22).

7. Method according to claim 6, characterized in that the flat material is a BNC fleece (16).

8. Method according to claim 7, characterized in that the BNC fleece (16) is coated with a mixture of sericin and plasticizer.

9. The method according to claim 7, characterized in that the BNC nonwoven (16) is treated with a plasticizer before the post-treatment step (22).

10. Process according to claim 8 or 9, characterized in that a crosslinking agent is added to the plasticizer.

11. Process according to claim 8 or 9, characterized in that a filler is added to the plasticizer and / or crosslinker.

12. Use of the organic leather substitute material (10) according to one of the preceding claims for the production of covering materials.

13. Cover material comprising the organic leather substitute material (10) according to the preceding claims.

14. A vehicle comprising an interior covered with a bio-leather substitute material (10) according to claim 1.

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