WO2024245701A1 - Bio leather replacement material comprising bacterial cellulose fibres - Google Patents

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

Description

Organic leather substitute material comprising bacterial cellulose fibers

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

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

Leather is used, among other things, as a covering material for car interiors, for example for 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 in an extensive process sequence (soaking, liming, pickling, tanning, dressing) until it becomes a usable leather covering material. This processing is energy-intensive and involves the use of process chemicals that represent an ecological burden. In addition, genuine leather is an animal product.

Artificial leather is an imitation leather. The basic idea behind the use of artificial leather is to avoid real leather as an animal product and the ecological problems caused by the production of real leather. However, the plastic polyvinyl chloride (PVC) or polyurethane (PU) used in artificial leather has a petrochemical basis and is therefore a non-renewable raw material or a finite resource. In addition, the phthalate plasticizers used in artificial leather are suspected of having a detrimental effect on human health. Furthermore, artificial leather is difficult to reuse as a composite material.

In general, 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 the company Malai, which is made from completely organic and sustainable bacterial cellulose that grows on agricultural waste from the coconut industry in South India or nanocellulose, which is a natural, renewable biopolymer made from pure cellulose and is obtained biotechnologically from a sugar solution (for example manufactured by JeNaCell®, Germany). Also suitable as alternative bio-leather substitute materials are materials based on bacterial cellulose (for example manufactured by ScobyTec GmbH, Germany). For example, it is known from KR 10219211 B1 that bio-leather substitute material can be produced using bacterial cellulose fibers. The bio-leather substitute material has a specific content of soy protein fraction and bacterial cellulose fibers that are modified with a hydroxyl-containing compound so that durability and flexibility are improved, making the material suitable for the production of clothing, furniture, building materials or as automotive interior materials.

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

WO 2022/177529 A1 describes an organic leather substitute that can be used as a substitute for animal hides and artificial leather, is physically and visually similar to real leather, contains no chemicals and has cellulose produced by microorganisms. The organic leather substitute mentioned is produced using a bacterial weaving process and can decompose in the soil in a short time and is therefore very environmentally friendly and has high tear resistance and high mechanical strength.

However, the sustainable leather alternatives known from the state of the art often do not meet the requirements in terms of durability and resilience. Plasticizers used for post-treatment lead to permanently increased odor emissions and are therefore also not suitable for use in the automotive sector. Cross-linking plasticizers, like textile softeners, do not penetrate deep enough into the compact layer of cellulose to achieve an improvement in the material properties. In addition, the plasticizers used can have a negative impact on human health.

The invention is based on the task of providing a resilient, visually appealing and overall high-quality organic leather substitute material, which, in comparison to State of the art technology allows it to be produced with reduced energy consumption and is associated with reduced ecological impact and at the same time at least partially overcomes the ecological disadvantages of known leather materials and artificial leather materials.

This object is initially 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 flat material based on bacterial nanocellulose (BNC), wherein the bacterial nanocellulose has a surface coating based on the protein sericin.

The organic leather substitute material according to the invention is characterized by improved tensile strength, flexibility, high mechanical stability, softer surface texture and water-repellent properties. The organic leather substitute material according to the invention can also prevent skin irritations in the user. The organic leather substitute material according to the invention thus represents a sustainable leather alternative that does not contain any harmful or odor-emitting plasticizers and is a resilient, visually appealing and overall high-quality material and reduces the use of non-renewable raw materials by using renewable raw materials. At the same time, the disadvantages of the leather materials and artificial leather materials known from the prior art are largely overcome in ecological terms. 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.

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.

This achieves the mechanical resilience of the organic leather substitute material as well as a change in texture and feel. In addition, the use of sericin in the organic leather substitute material according to the invention has the advantage that it is available in large quantities as a natural raw material source, since it has previously been a by-product of the processing of silk cocoons and therefore has great potential in the field of circular economy.

The above-mentioned object is also achieved by a process for producing the bio-leather substitute material according to the invention, wherein bacterial nanocellulose is first static or dynamic cultivation and a flat material produced in this way is then coated with sericin in a further step.

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

The process according to the invention can significantly improve the material properties of the bacterial nanocellulose and thus allow it to be further processed into a leather-like material. A softer surface texture of the material is obtained, which optimizes the tensile strength and thus the material according to the invention can be used as a user-friendly and durable material in the vehicle interior.

Further preferred embodiments of the invention result from the remaining features mentioned in the subclaims.

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

Sericin is a silk protein and is a natural water-soluble glycoprotein obtained from raw silk. Silk threads consist of two filaments of fibroin covered with sericin. The production of silk threads by the silkworm Bombyx mori is widespread. The sericin is extracted from the cocoons of this silkworm, 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 cross-linking, copolymerization and polymer reactions. Sericin dissolves in water at temperatures of 50 to 60 °C and takes on a gel-like consistency through reaction with other polymers.

In a first embodiment of the organic leather substitute material according to the invention, the sheet-like material can comprise a fleece made of bacterial nanocellulose (BNC).

The BNC fleece can serve as a flat product for the production of organic leather substitute materials.

Bacterial nanocellulose (BNC) can be produced by the biochemical polymerization of low molecular weight building blocks such as glucose using Acetic acid bacteria. BNC differs significantly in its morphology from cellulose of plant origin. 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 has a framework structure comparable to human tissue. It contains up to 99% water and is able to interact intensively with the environment. BNC is mechanically stable even when wet. 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 approx. 4,000 to 10,000) and high crystallinity (80% to 90%).

BNC fleeces can be produced by static or dynamic cultivation at an ambient temperature of 20°C to 30°C. With static cultivation, the cultivation time is 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 to a layer thickness of 4 to 5 cm. Dynamic cultivation takes place with a uniform oxygen input over a period of 4 to 5 days.

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.

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

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

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

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

Suitable cross-linking reagents include citric acid, glutaraldehyde, tannic acid or other vegetable tanning agents such as those from oak bark, mimosa bark, quebracho wood or sumac leaves. With the help of cross-linking reagents, the sericin can be bound 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.

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

Suitable fillers include polyvinyl alcohol or chitosan and their mixtures.

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

A further aspect of the invention is the use of the organic leather substitute material according to the invention for the production of covering materials, in particular organic leather substitute materials for vehicle interiors.

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

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

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

Production of the organic leather substitute material according to the invention,

Figure 2 shows a schematic representation of further embodiments for producing the organic leather substitute material according to the invention and

Figure 3 is a further schematic representation of further embodiments for

Production of the organic leather substitute material according to the invention.

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 with the metabolism of carbon and nitrogen. The cultivation in Nutrient medium 12 is prepared according to a known method, whereby the nutrient medium 12 consists of D-glucose as carbon source (20 g/L), bactopeptone (5 g/L) and yeast extract as 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).

After the static or dynamic cultivation 18, the cultivated bacterial nanocellulose 14 can be harvested as BNC fleece 16 and then purified with a 0.1 M NaOH solution and distilled water in alternation in several washing processes (at least two, preferably three to four) 20. The bacterial nanocellulose 14 is further processed as BNC fleece 16 without being crushed. After the purification 20, the post-treatment 22 with a sericin solution S takes place. In a final step, the BNC fleece 16 is dried.

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

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).

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 dipping for 5 to 100 seconds, preferably 10 to 20 seconds (Figure 2).

In a further embodiment, the BNC fleece 16 is first treated with a plasticizer by soaking 28. A crosslinking agent can be added for stabilization. Sericin dissolved in distilled water is then applied to the surface 26 by spraying, brushing, or brief immersion for 5 to 100 seconds, preferably 10 to 20 seconds (Figure 3).

In an alternative embodiment, the BNC fleece 16 is first treated with a plasticizer by immersion 28. A crosslinking agent can be added for stabilization. The BNC fleece 16 is then immersed 24 in a sericin solution for 1 to 7 days, preferably 3 to 5 days (Figure 3).

In a further embodiment, the BNC fleece 16 can be placed in a solution of sericin and plasticizer. In addition, the crosslinker can also be added. In a further step, the sericin coating is dried and finally cured at 90°C to 110°C, preferably 95°C to 105°C, for 12 to 24 hours in the oven.

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

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

In an alternative or additional embodiment of the method according to the invention, in steps 18 and/or 20, prior to treatment with sericin 22, the material is stained.

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

List of reference symbols Organic leather substitute material Nutrient medium Cultured bacterial nanocellulose BNC fleece Static or dynamic cultivation Purification Post-treatment step Placing in sericin solution Applying the sericin solution Treatment with softener 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. Organic 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. Organic 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 flat material produced in this way is subsequently coated with sericin in a further step (22). 7. Method according to claim 6, characterized in that the sheet 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 fleece (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. Covering material comprising the organic leather substitute material (10) according to the preceding claims. 14. Vehicle having an interior covered with a bio-leather substitute material (10) according to claim 1.