Method for producing synthetic leather

Abstract

[Problem] To provide a method for producing a synthetic leather having a lower burden on the environment. [Solution] Provided is a method for producing a synthetic leather, the method including preparing a base fabric layer on which is disposed either a resin film A formed by heating and pressing a polymer compound that includes a polypeptide structure or a powder of a polymer compound that includes a polypeptide structure, heating the powder or the resin film A while pressing same against the base fabric layer, tightly bonding the base fabric layer to the resin film A or a resin film B formed by pressing the powder, thereby forming a skin layer from the resin film A or the resin film B, and integrally layering the skin layer on the base fabric layer. The polymer compound that includes a polypeptide structure includes a block copolymer having a first segment that includes a polypeptide skeleton and one or more second segments bonded to the first segment. The second segment includes a molecular group having the function of plasticizing the polypeptide skeleton.

Description

Synthetic leather manufacturing method

[0001] The present disclosure relates to a method for producing synthetic leather.

[0002] Synthetic leather has been used as a substitute for natural leather. One type of synthetic leather known is one in which a surface layer is integrally laminated onto a base layer. In many cases, the base layer of such synthetic leather is made of a fabric layer such as a woven or knitted fabric or a nonwoven fabric, and the surface layer is formed by thinly coating a flexible polyurethane resin or the like onto the base fabric layer.

[0003] Unlike natural leather, which has limitations in productivity and standardization of quality, synthetic leather can be mass-produced with stable quality artificially, and has therefore come to be used in a wider range of applications in recent years, including clothing, shoes, decorative items such as bags, various covers, furniture, etc. Furthermore, by selecting the material, various functions such as stretchability and waterproofness can be imparted to synthetic leather, and it is expected that synthetic leather will find industrial application in a variety of fields.

[0004] For example, Patent Document 1 describes a synthetic leather having a substrate layer containing a fiber substrate, wherein at least a portion of the synthetic leather contains a polypeptide derivative, the polypeptide derivative comprising a block copolymer having a first segment containing a polypeptide backbone and one or more second segments bound to the first segment, the polypeptide backbone being a recombinant polypeptide backbone, and the second segment comprising a molecular group having a plasticizing function for the polypeptide backbone. Patent Document 2 describes a method for producing a biofabrication material, including the steps of: preparing a collagen concentrate; preparing a substrate; placing the collagen concentrate on the substrate; placing the substrate together with the collagen concentrate in a heat press; pressing and heating the substrate together with the collagen concentrate, and cooling the substrate together with the collagen concentrate to produce a biofabrication material.

[0005] International Publication No. 2023 / 013638 International Publication No. 2020 / 018516

[0006] Conventional synthetic leathers have been made to exhibit flexibility similar to that of natural leather by, for example, thinly coating a base fabric layer with a polyurethane resin, as described above. However, the use of petroleum-derived materials has a significant environmental impact. Therefore, in Patent Document 1, the present applicant proposed a synthetic leather comprising a base fabric layer and a skin layer containing a polypeptide derivative laminated thereon. This synthetic leather has a skin layer composed of a biodegradable polypeptide derivative, and the polypeptide derivative includes a block copolymer having a first segment containing a polypeptide backbone and one or more second segments bonded to the first segment, and the second segment includes a molecular group capable of plasticizing the polypeptide backbone. This ensures sufficient flexibility while reducing the environmental impact. However, the synthetic leather manufacturing method described in Patent Document 1 uses an organic solvent, which is being increasingly used as an alternative due to environmental pollution concerns, as the solvent for the polypeptide derivative solution coated on the base fabric layer, leaving room for improvement in this regard.

[0007] An object of the present invention is to provide a method for producing synthetic leather that reduces the burden on the environment.

[0008] Representative embodiments of the present invention are described below. <1> A method for producing synthetic leather comprising a fabric layer and a skin layer integrally laminated on the fabric layer, the method comprising: preparing a fabric layer on which a resin film A formed by heating and pressurizing a polymer compound having a polypeptide structure or a powder of a polymer compound having a polypeptide structure is placed; and pressing the resin film A or the powder against the fabric layer while heating it to adhere the resin film A or the resin film B formed from the powder by pressing it to the fabric layer, thereby forming the skin layer from the resin film A or the resin film B, and integrally laminating the skin layer to the fabric layer, wherein the polymer compound having a polypeptide structure comprises a block copolymer having a first segment including a polypeptide backbone and one or more second segments bonded to the first segment, and the second segment comprises a molecular group having a plasticizing function for the polypeptide backbone. <2> The method according to <1>, wherein the polypeptide backbone is a recombinant polypeptide backbone. <3> The method according to <1> or <2>, wherein the polypeptide backbone is a hydrophobic polypeptide backbone. <4> The method according to any one of <1> to <3>, wherein the molecular group having a plasticizing function for the polypeptide backbone is polyether, polyester, or polycarbonate. <5> The method according to any one of <1> to <4>, wherein the block copolymer is obtained by mechanochemically treating a mixture containing a compound having the polypeptide backbone and a compound having a molecular group capable of plasticizing the polypeptide backbone. <6> The method according to any one of <1> to <5>, wherein the fabric layer and the resin film A or the powder are heated and pressed using a hot roll press.

[0009] According to the present invention, a method for producing synthetic leather that reduces the burden on the environment is provided.

[0010] FIG. 1 is a cross-sectional view showing an outline of synthetic leather according to one embodiment; FIG. 2 is a cross-sectional view showing an outline of an example of a base fabric layer on which a resin film A is placed; FIG. 3 is a cross-sectional view showing an outline of an example of a base fabric layer on which powder of a polymer compound containing a polypeptide structure is placed; FIG. 4 is a scanning electron microscope (SEM) image of a cross section of the synthetic leather obtained in Example 1; and FIG. 5 is a photograph of the synthetic leathers obtained in Examples 2 to 4.

[0011] The main embodiments of the present invention will be described below. However, the present invention is not limited to the explicitly described embodiments. In this specification, a numerical range expressed using the symbol "to" means a range including the numerical values ​​before and after "to" as the lower and upper limits, respectively. In this specification, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended effect of the process is achieved. In this specification, unless otherwise specified, the temperature is 23°C, the pressure is 101,325 Pa (1 atmosphere), and the humidity (relative humidity) is 50% RH. In this specification, a combination of preferred aspects is a more preferred aspect.

[0012] (Method for Producing Synthetic Leather) A method for producing synthetic leather according to this embodiment is a method for producing synthetic leather comprising a base fabric layer and a skin layer integrally laminated on the base fabric layer, and includes the steps of: preparing a base fabric layer on which a resin film A formed by heating and pressurizing a polymer compound having a polypeptide structure, or a powder of a polymer compound having a polypeptide structure is placed; and pressing the resin film A or the powder against the base fabric layer while heating it, thereby adhering the resin film A or the resin film B formed from the powder by the pressing to the base fabric layer, thereby forming the skin layer from the resin film A or the resin film B, and integrally laminating the skin layer on the base fabric layer, wherein the polymer compound having a polypeptide structure comprises a block copolymer having a first segment including a polypeptide backbone and one or more second segments bonded to the first segment, and the second segment comprises a molecular group having a plasticizing function for the polypeptide backbone.

[0013] The method for producing synthetic leather according to the present embodiment does not use a solution of a polymer dissolved in an organic solvent as in the conventional method, but rather applies pressure to a fabric layer by placing a polymer containing a polypeptide structure in powder form or in the form of a resin film. Thus, the method for producing synthetic leather according to the present embodiment does not require the use of environmentally hazardous organic solvents, thereby reducing the environmental impact of the synthetic leather. Furthermore, the method for producing synthetic leather according to the present embodiment uses a polymer containing a block copolymer having a first segment containing a polypeptide backbone and one or more second segments bonded to the first segment, the second segment containing a molecular group capable of plasticizing the polypeptide backbone. The use of such a polymer allows the surface layer to be integrally laminated to the fabric layer, even when used in powder or resin film form. This is believed to be due to the following reason: When a powder is used, the powder is resinified (hardened) by heating and pressure application, and a portion of the resinified surface layer penetrates into the fabric layer, and this portion of the powder penetrates into the fabric layer, exerting an anchoring effect on the fabric layer, thereby allowing the surface layer to be integrally laminated to the fabric layer. Furthermore, when a resin film is used, the resin film softens upon heating and pressing (applying pressure), and a portion of the softened resin film penetrates into the fabric layer, where it exerts an anchoring effect on the fabric layer, thereby forming an integral layer of the skin layer on the fabric layer. Furthermore, by being able to integrally form the skin layer on the fabric layer, the physical properties such as modulus of elasticity, stress at break, and depth at break can be set to values ​​sufficient for synthetic leather.

[0014] Hereinafter, embodiments of the present disclosure will be described in detail, with reference to the drawings as needed. However, the following embodiments are merely examples for explaining the present disclosure, and are not intended to limit the present disclosure to the following contents.

[0015] <Synthetic Leather> The method for producing a synthetic leather according to this embodiment is a method for producing a synthetic leather comprising a base fabric layer and a skin layer integrally laminated on the base fabric layer. The synthetic leather according to this embodiment may further comprise layers (other layers) other than the base fabric layer and the skin layer. A preferred embodiment of the synthetic leather according to this embodiment is a synthetic leather comprising a base fabric layer and a skin layer. The skin layer comprises a polymeric compound containing a polypeptide structure, and in particular, the polymeric compound comprises a block copolymer having a first segment containing a polypeptide backbone and one or more second segments bonded to the first segment, and the second segment comprises a molecular group capable of plasticizing the polypeptide backbone. Therefore, the synthetic leather according to this embodiment has excellent flexibility and softness.

[0016] Synthetic leather, also known as artificial leather, has the appearance and functionality of natural leather. Synthetic leather can be obtained, for example, by using a layer containing woven fabric, knitted fabric, nonwoven fabric, etc. as a base fabric layer and integrally laminating a surface layer onto the base fabric layer. In this specification, synthetic leather also includes so-called artificial leather, which uses a special nonwoven fabric as the base fabric layer. The special nonwoven fabric used in artificial leather includes a substrate mainly composed of a fiber layer with a random three-dimensional structure, impregnated with a flexible synthetic polymer substance such as polyurethane, or a polymer compound containing a polypeptide skeleton, which is used in the surface layer in this embodiment.

[0017] FIG. 1 is a cross-sectional view showing an outline of synthetic leather according to one embodiment. The synthetic leather 10 shown in FIG. 1 includes a base fabric layer 2 and a skin layer 1 bonded to the base fabric layer 2. In the synthetic leather 10 shown in FIG. 1, the skin layer 1 also functions as a shape-retaining layer for maintaining the shape of the synthetic leather. The skin layer 1 is integrally laminated with the base fabric layer 2. For example, the skin layer 1 may penetrate into the fibers of the base fabric layer 2. As a result, the interface between these layers may not be clearly defined. In the embodiment shown in FIG. 1, the skin layer 1 is formed on one side of the base fabric layer 2, but there may also be embodiments in which skin layers are formed on both sides of the base fabric layer.

[0018] [Fabric Layer] The fabric layer is not particularly limited, but is preferably a layer containing a fibrous substrate. The fibrous substrate may be, for example, a knitted or woven fabric or a nonwoven fabric. The knitted or nonwoven fabric as the fibrous substrate may be composed of synthetic fibers such as polyester, polyamide, polyacrylonitrile, polyolefin, and polyvinyl alcohol; natural fibers such as cotton, linen, and silk; regenerated fibers such as rayon, staple fiber, acetate, and collagen; artificial protein fibers such as artificial casein, collagen, and fibroin; or artificial structural protein fibers, either alone or in combination. Alternatively, it may be composed of multicomponent fibers modified into ultrafine fibers by dissolving at least one component or splitting two-component fibers, or fibers of a polymer compound containing a polypeptide structure. Such a substrate layer or the polymer compound fibers containing a polypeptide structure contained therein may contain known additives as necessary. Examples of additives include colorants, smoothing agents, antioxidants, UV absorbers, dyes, fillers, crosslinking agents, matting agents, and leveling agents.

[0019] The knitted or woven fabric is a general term for knitted fabrics and woven fabrics. The knitted fabric may be either a knitted fabric having a weft knitting structure such as flat knitting or circular knitting (also simply referred to as a "weft knitting fabric"), or a knitted fabric having a warp knitting structure such as tricot or raschel (also simply referred to as a "warp knitting fabric"). The woven fabric may be a woven fabric having any of plain weave, twill weave, or satin weave. The knitted or woven fabric may be an unprocessed knitted or woven fabric obtained by knitting or weaving, or may be a knitted or woven fabric that has been treated with a water-repellent finish or the like after knitting or weaving.

[0020] The knitted or woven body can be obtained by knitting or weaving raw yarn. Known methods can be used for the knitting and weaving methods. Examples of knitting machines that can be used include circular knitting machines, warp knitting machines, and flat knitting machines, with circular knitting machines being preferred from the viewpoint of productivity. Flat knitting machines include molding knitting machines and seamless knitting machines, but seamless knitting machines are more preferred, particularly because they allow the production of knitted fabrics in the form of final products. Examples of looms that can be used include shuttle looms and shuttleless looms such as gripper looms, rapier looms, and air jet looms.

[0021] The raw material yarn may be a single yarn or a composite yarn (e.g., blended yarn, mixed yarn, covered yarn, etc.), or a combination of these may be used. The single yarn and composite yarn may be a spun yarn made by twisting together short fibers, or a filament yarn made by twisting together long fibers. Examples of fibers contained in the raw material yarn include synthetic fibers such as nylon, polyester, polyamide, polyacrylonitrile, polyolefin, polyvinyl alcohol, polyethylene terephthalate, and polytetrafluoroethylene; regenerated fibers such as cupra, rayon, and lyocell; natural fibers such as cotton, hemp, and silk; protein fibers; and fibers of polymer compounds containing a polypeptide structure.

[0022] The nonwoven fabric can be produced by a known production method using the above-mentioned fibers, for example. Specifically, for example, a web (including a single-layer web and a laminated web) is formed from the above-mentioned fibers by a dry method, a wet method, an air-laid method, or the like, and then the fibers of the web are bonded by a chemical bonding method (a dipping method, a spray method, or the like) or a needle punch method, to obtain a nonwoven fabric. The nonwoven fabric can also be formed by spinning using an electrospinning method.

[0023] The numerical ranges of the fiber density (basis weight), porosity, bulk density, etc. of the nonwoven fabric are appropriately set so that they are within ranges that can sufficiently ensure waterproofness and moisture permeability. The basis weight, porosity, bulk density, etc. can be adjusted, for example, by increasing or decreasing the amount of fiber that constitutes the web, or, in the case of a laminated web, by increasing or decreasing the number of layers.

[0024] The substrate layer may further contain a polymeric substance. When the substrate layer further contains a polymeric substance, the substrate layer can be said to be a layer in which a fibrous substrate and an impregnated body made of a polymeric substance impregnated into the fibrous substrate are integrated together, or a layer in which the fibrous substrate is embedded in a layer formed of a polymeric substance.

[0025] Generally, polymeric substances are impregnated into a fiber substrate in solution, coagulate (solidify) by removing the solvent, and remain attached to the fibers in the gaps between the fibers of the fiber substrate. That is, the polymeric substance is integrated with the fiber substrate as a so-called impregnated body, and together with the fiber substrate, it forms a base layer of a synthetic leather, interconnecting the fibers of the fiber substrate, maintaining the shape of the base layer, and imparting a predetermined strength to the base layer. Examples of such polymeric substances include synthetic resins such as polyvinyl chloride, polyolefins, polystyrene, polyurethane, polyester resins, epoxy resins, acrylic polymers, and acrylonitrile polymers, as well as proteins. Examples of polyurethanes include polyether-based polyurethanes, polyester-based polyurethanes, and polycarbonate-based polyurethanes, which may be used alone or in combination. Polyurethanes can be synthesized, for example, by reacting a diisocyanate with a polyol to synthesize a prepolymer, and then reacting the prepolymer with a chain extender. The diisocyanate may be an aromatic or aliphatic compound. The polyol may be, for example, polyester, polyether, polycarbonate, silicone, fluororesin, etc. Using a polyether as the polyol provides excellent hydrolysis resistance, mildew resistance, and cold resistance, while using a polycarbonate as the polyol provides excellent hydrolysis resistance and mildew resistance. The chain extender may be, for example, a glycol, a diamine, a reaction terminator, etc. The polymeric substance may contain a polymeric compound having a polypeptide structure. When the polymeric substance contains a polymeric compound having a polypeptide structure, it can impart greater flexibility to the synthetic leather. Such a polymeric substance may contain known additives as needed. Examples of additives include colorants, smoothing agents, antioxidants, UV absorbers, dyes, fillers, crosslinking agents, matting agents, leveling agents, etc.

[0026] The fabric layer may include a porous layer. That is, the fabric layer may be porous, or the fabric layer may include a fabric layer made of a knitted or nonwoven fabric, etc., and a porous layer laminated on the fabric layer. The fabric layer including a porous layer can provide a more voluminous feel and higher flexibility.

[0027] The thickness of the substrate layer may be, for example, 100 to 2000 μm, 100 to 1000 μm, 500 to 1000 μm, or 500 to 750 μm.

[0028] [Epidermal Layer] The epidermal layer is a layer formed mainly from a polymer compound containing a polypeptide structure. The polymer compound containing a polypeptide structure will be described in detail later.

[0029] The surface layer may contain known additives as needed, such as colorants, smoothing agents, antioxidants, ultraviolet absorbers, dyes, fillers, crosslinking agents, matting agents, and leveling agents.

[0030] Furthermore, from the viewpoint of improving the mechanical properties of the synthetic leather, such as elastic modulus, stress at break, and elongation at break, the skin layer may contain a plasticizer. The plasticizer may be any compound known in this field as a plasticizer for resins or protein structures, without particular limitation. Examples of suitable plasticizers include polyhydric alcohols such as glycerol, diglycerin, and diethylene glycol; alkylene oxide adducts of these polyhydric alcohols; polyethers such as polyethylene glycol and polypropylene glycol; phenolic compounds such as bisphenol A and bisphenol S; and amide compounds such as N-methylpyrrolidone. Among these, polyhydric alcohols are preferred, and glycerol is more preferred.

[0031] When a plasticizer is contained, the content of the plasticizer relative to the total mass of the surface layer is not particularly limited, but is preferably 0.1 to 15.0 mass%, more preferably 0.5 to 10.0 mass%, and even more preferably 0.5 to 8.0 mass%.

[0032] The thickness of the skin layer is not particularly limited, and may be, for example, 1 to 1000 μm, 1 to 700 μm, 1 to 500 μm, 1 to 400 μm, 5 to 300 μm, 5 to 200 μm, or 10 to 100 μm.

[0033] The surface of the skin layer (the surface opposite to the surface bonded to the base layer) may be subjected to a surface treatment. A known method can be used for the surface treatment. Examples of surface treatments include embossing, buff suede treatment, film lamination, and gravure treatment (gravure printing).

[0034] [Adhesive Layer] The synthetic leather according to this embodiment may have an adhesive layer. However, since the surface layer is integrally laminated to the base fabric layer in this embodiment, an adhesive layer is not necessarily required, and an embodiment without an adhesive layer is also a preferred embodiment. The adhesive layer is formed using an adhesive. Examples of resins (polymers) used as adhesives include polymeric compounds containing polypeptide structures, proteins, and synthetic resins. Examples of synthetic resins include polyolefins, polystyrene, polyurethanes, acrylics, and EVA (ethylene vinyl acetate copolymer). The resin (polymer) forming the adhesive layer may also be a composite material containing at least two of a polymeric compound containing a polypeptide structure, a protein, and a synthetic resin. The adhesive layer may contain known additives as needed. Examples of additives include colorants, smoothing agents, antioxidants, UV absorbers, dyes, fillers, crosslinking agents, matting agents, and leveling agents.

[0035] When an adhesive layer is formed, the thickness of the adhesive layer is not particularly limited, but may be, for example, 1 to 500 μm, 5 to 400 μm, 10 to 300 μm, 10 to 200 μm, or 10 to 100 μm.

[0036] <Preparation Step> The method for producing synthetic leather according to this embodiment includes preparing a resin film A formed by heating and pressurizing a polymer compound having a polypeptide structure, or a base fabric layer on which powder of a polymer compound having a polypeptide structure is placed (also referred to as the "preparation step" in this specification).

[0037] [When Resin Film A is Used] In the preparation step, for example, resin film A can be placed on a fabric layer to obtain a fabric layer having resin film A thereon. The placement method is not particularly limited, and known methods can be used. FIG. 2 is a cross-sectional view showing an example of a fabric layer having resin film A placed thereon. In FIG. 2, a resin film A4 is placed on fabric layer 2. While FIG. 2 shows one resin film A4 placed on one side of fabric layer 2, it is also possible to have one or more resin films A4 placed on each side of fabric layer 2, or two or more resin films A4 placed on one side of fabric layer 2. Resin film A4 is produced by a known heating and pressurizing method without any particular limitations. For example, it can be produced by a method of heating and pressurizing a powder of a polymer compound containing a polypeptide structure. Other known methods, such as extrusion and casting, may also be used; the production method is not particularly limited as long as a resin film can be obtained. The powder can be obtained, for example, by the method for producing a polymer compound containing a polypeptide structure described below. Alternatively, the polymer compound obtained by the method for producing a polymer compound containing a polypeptide structure described below can be pulverized by a known method. The heating temperature is preferably 80 to 300°C, more preferably 90 to 180°C, and even more preferably 100 to 130°C. The pressure is preferably 20 MPa or less, more preferably 15 MPa or less, and even more preferably 10 MPa or less. Furthermore, after reaching the specified heating and pressurizing conditions, the time for continuing treatment under those conditions (warming conditions) is preferably 60 minutes or less, more preferably 30 minutes or less, and even more preferably 15 minutes or less. However, these heating and pressurizing conditions may be appropriately changed taking into account the thickness, mechanical properties, chemical properties, etc. of the resulting resin film A4. For example, when producing using a hot roll press, the heating temperature is preferably 80 to 300°C, more preferably 90 to 180°C, and even more preferably 100 to 130°C. The load may be 0.5 to 10 kN, and may be 1.0 to 8.0 kN. The roll gap may be 0.1 to 2.0 mm, and may be 0.2 to 1.0 mm. The roll feed speed may be 0.1 to 1.0 m / min, and may be 0.1 to 0.6 m / min.However, these conditions may be changed as appropriate in consideration of the thickness, mechanical properties, chemical properties, etc. of the resin film A4 to be obtained.

[0038] 2, the fabric layer 2 and the resin film A4 are shown as being in contact with each other, but other layers, such as an adhesive layer, may be present between the fabric layer 2 and the resin film A4. Another preferred embodiment of this invention is one in which the fabric layer 2 and the resin film A4 are placed on the fabric layer 2 so that they are in contact with each other, without any other layers present between them.

[0039] In FIG. 2 , the resin film A4 is shown as being placed on the entire surface of the fabric layer 2, but the resin film A4 may be placed on only a part of the fabric layer 2 rather than the entire surface, or conversely, the resin film A4 may be larger than the fabric layer 2.

[0040] The resin film A4 may contain known additives as needed, such as colorants, smoothing agents, antioxidants, ultraviolet absorbers, dyes, fillers, crosslinking agents, matting agents, and leveling agents.

[0041] Furthermore, from the viewpoint of improving the mechanical properties of the synthetic leather, such as elastic modulus, breaking stress, and breaking depth, the resin film A4 may contain a plasticizer. Examples of the plasticizer include those described above for the skin layer, and the preferred embodiments and preferred contents are also the same.

[0042] The thickness of the resin film A4 is not particularly limited, but may be, for example, 1 to 1000 μm, 1 to 700 μm, 1 to 500 μm, 1 to 400 μm, 5 to 300 μm, 5 to 200 μm, or 10 to 100 μm.

[0043] As mentioned above, when the skin layer contains an organic solvent as a plasticizer, or when an organic solvent is used in the production of the polymer compound (block copolymer) containing a polypeptide skeleton that constitutes the resin film A4 as described below, it is desirable to minimize the amount of organic solvent used. From this perspective, it is desirable to minimize the content of organic solvent in the resin film A4. Specifically, the content of organic solvent relative to the total mass of the resin film A4 is preferably 10% by mass or less, more preferably 5% by mass or less, and most preferably 3% by mass or less, and most preferably 0% by mass (i.e., no organic solvent is used as a plasticizer or no organic solvent is used in the production of the block copolymer).

[0044] [When using powder] In the preparation step, a fabric layer having the powder thereon can be obtained by applying a powder of a polymer compound having a polypeptide structure to the fabric layer, for example, by spreading the powder on the fabric layer. The application method is not particularly limited, and known methods can be used. FIG. 3 is a cross-sectional view showing an example of a fabric layer having a powder of a polymer compound having a polypeptide structure applied thereto. In FIG. 3, a powder 6 of a polymer compound having a polypeptide structure is applied to the fabric layer 2. The powder 6 can be obtained by the method for producing a polymer compound having a polypeptide structure described below, or by pulverizing the polymer compound obtained by the method for producing a polymer compound having a polypeptide structure described below using a known method.

[0045] 3, the fabric layer 2 and the powder 6 are shown as being in contact with each other, but another layer, such as an adhesive layer, may be present between the fabric layer 2 and the powder 6. Another preferred embodiment of this invention is one in which there is no other layer between the fabric layer 2 and the powder 6, and the powder 6 is placed on the fabric layer 2 so that the fabric layer 2 and the powder 6 are in contact with each other.

[0046] In FIG. 3, the powder 6 is shown to be applied to the entire surface of the fabric layer 2, but the powder 6 may be applied to only a part of the fabric layer 2, not the entire surface.

[0047] The powder 6 may contain known additives as needed, such as colorants, smoothing agents, antioxidants, ultraviolet absorbers, dyes, fillers, crosslinking agents, matting agents, and leveling agents.

[0048] In order to improve the mechanical properties of the synthetic leather, such as the elastic modulus, breaking stress, and breaking depth, the powder 6 may contain a plasticizer. Examples of the plasticizer include those described above for the skin layer, and the same applies to preferred embodiments.

[0049] In powder 6, the known additives, plasticizers, and other components may be present within powder 6, or may be present, for example, in the form of coating powder 6, or may be present, for example, as a separate powder outside powder 6. For example, powder 6 containing the known additives, plasticizers, and other components can be obtained by adding the known additives, plasticizers, and other components to a powder of a polymer compound containing a polypeptide structure, and then mixing the resulting mixture while grinding it in a mortar.

[0050] The particle size of the powder 6 is not particularly limited, but may be 1 to 500 μm, 10 to 400 μm, or 20 to 300 μm. The particle size can be determined, for example, by the following method. The powder is uniformly dispersed on a glass plate by suction in a vacuum chamber, and then measured five times using a wet / dry image analysis particle size distribution meter (product name: DW-200 nano, manufactured by Jasco International Co., Ltd.). Projected images are taken with a 10-megapixel camera, and the resulting projected images are analyzed using image analysis software. The amount of powder 6 to be applied is not particularly limited, but may be 5 to 200 mg / cm as the amount per unit area of ​​the fabric layer 1. ２ and may be 10 to 150 mg / cm ２ and may be 20 to 100 mg / cm ２ It may be.

[0051] As in the case of using the resin film A4 described above, when the skin layer contains an organic solvent as a plasticizer or when an organic solvent is used in the production of the polymer compound (block copolymer) containing a polypeptide skeleton that constitutes powder 6, it is desirable to minimize the amount of organic solvent used. From this perspective, it is desirable to minimize the content of organic solvent in powder 6. Specifically, the content of organic solvent relative to the total mass of powder 6 is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and most preferably 0% by mass.

[0052] [Laminating Step] The method for producing a synthetic leather according to this embodiment includes the steps of heating the resin film A or the powder and pressing it against the fabric layer to adhere the resin film A or the resin film B formed from the powder by the pressing to the fabric layer, thereby forming the surface skin layer from the resin film A or the resin film B, and laminating the surface skin layer integrally with the fabric layer (also referred to as the "laminating step" in this specification).

[0053] In the lamination process, resin film A or resin film B is softened by heating and pressing, forming a surface layer integrated with the fabric layer. In one preferred embodiment of this invention, a portion of the softened resin film A or resin film B penetrates into the fabric layer. The heating temperature is preferably 80 to 300°C, more preferably 90 to 180°C, and even more preferably 100 to 130°C. The applied pressure is preferably 5 MPa or higher, more preferably 10 MPa or higher, and even more preferably 20 MPa or higher. The application of pressure is preferably in the thickness direction of the fabric layer.

[0054] The heating and pressure bonding can be performed using known methods such as a hot press, a hot roll press, or mold pressing. From the viewpoint of productivity, however, it is preferable to use a hot roll press, which is capable of continuous production. That is, the lamination step preferably includes heating and pressurizing the fabric layer and the resin film A or the powder using a hot roll press. Any known device can be used as the hot roll press without any particular limitations. When producing using a hot roll press, the heating temperature is preferably 80 to 300°C, more preferably 90 to 180°C, and even more preferably 100 to 130°C. The roll gap and load of the hot roll press can be set in consideration of the thickness of the resin film A or B and the substrate, etc., so that the applied pressure falls within the above-mentioned range. For example, the roll gap may be 0.1 to 2 mm or 0.2 to 1 mm. The load may be 0.5 to 10.0 kN or 1.0 to 8.0 kN. The roll feed speed may be 0.1 to 1.0 m / min, or 0.1 to 0.6 m / min, although these conditions may be changed appropriately in consideration of the thickness, mechanical properties, chemical properties, etc. of the resulting resin film A or resin film B and the substrate.

[0055] [Other Steps] The synthetic leather manufacturing method according to this embodiment may further include steps other than the preparation step and the lamination step. Examples of such steps include, after the preparation step, adding water to the resin film A or powder placed on the fabric layer. This promotes softening of the resin film A and the resin film B formed by resinifying the powder when the resin film A or powder is heated and pressurized in the subsequent lamination step, thereby improving the formability of the surface layer and its adhesion to the fabric layer. The amount of water added to the resin film A or powder is not particularly limited as long as it promotes softening of the resin film A or resin film B. However, it is preferable that the amount be an amount that can evaporate during the heating and pressurizing operation in the lamination step. For example, the amount of water added to the resin film A or powder is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on the resin film A or powder. Other steps include, after the lamination step, surface-treating the surface of the surface layer opposite the fabric layer and cutting the resulting synthetic leather. These steps can be carried out by methods known in the art.

[0056] [Uses of Synthetic Leather] The synthetic leather according to the present embodiment can be used in applications that have been used for conventional synthetic leather (for example, synthetic leather made of synthetic resin). The synthetic leather according to the present embodiment can be used for applications such as clothing, decorative items such as shoes and bags, various covers and furniture, and automotive interior materials.

[0057] <Polymer Compound Containing a Polypeptide Structure> The polymer compound containing a polypeptide structure comprises a block copolymer having a first segment containing a polypeptide backbone and one or more second segments bound to the first segment. The second segment comprises a molecular group having a plasticizing function for the polypeptide backbone. The number of second segments per first segment is one or more, preferably 2 or more, more preferably 2 to 10, even more preferably 2 to 8, particularly preferably 2 to 6, and most preferably 2 to 4.

[0058] The block copolymer contained in the polymer compound containing a polypeptide structure may be any block copolymer having a first segment and a second segment. For example, it may be a block copolymer having one or more second segments bonded to one first segment, or a block copolymer having multiple blocks each including a first segment and a second segment bonded to the first segment. The block copolymer contained in the polymer compound containing a polypeptide structure may be a polymer (e.g., a graft polymer) having a first segment containing a polypeptide backbone as the main chain and a second segment as a side chain. The block copolymer may have, for example, multiple first segments, with the first segments and the second segments bonded alternately. The alternating bonding of the first segments and the second segments may further improve the toughness of synthetic leather, for example.

[0059] The block copolymer contained in the polymer compound having a polypeptide structure may have a plurality of the first segments, and a portion of the second segments may be bonded to two or more of the first segments to form a network structure. The network structure can further improve the toughness of the synthetic leather.

[0060] The bond between the first segment and the second segment may be a direct bond, or may be a bond via a structure that allows bonding between the first segment and the second segment. In any of these bonding forms, the bond between the first segment and the second segment may be a coordinate bond, a bond due to ionic interaction, or a covalent bond. Among these, a covalent bond is preferred.

[0061] [First Segment] The first segment includes a polypeptide backbone and may, for example, consist solely of a polypeptide backbone. The first segment may be bound to the second segment via a functional group (e.g., a thiol group of cysteine) in the amino acid sequence constituting the polypeptide backbone. In other words, any recombinant polypeptide or hydrophobic polypeptide having a functional group capable of binding to the second segment can be used as the polypeptide backbone. In this case, the number of functional groups possessed by the polypeptide may be, for example, one or more, two or more, or four or more. The number of functional groups possessed by the polypeptide may be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 8 or less. The number of functional groups possessed by the polypeptide can be adjusted within the above-mentioned ranges and may be, for example, 1 to 30, 1 to 25, 1 to 20, 1 to 15, 1 to 10, 1 to 8, or 2 to 8. The first segment may be bound to the second segment via a functional group introduced into a functional group in the amino acid sequence constituting the polypeptide backbone.

[0062] The functional group as described above may be, for example, at least one selected from the group consisting of a thiol group, an amino group, a hydroxy group, a guanidino group, a carboxy group, a phenoxy group, an indole group, an amide group, an azide group, and an alkynyl group, preferably at least one selected from the group consisting of a thiol group, an amino group, a hydroxy group, a guanidino group, a carboxy group, a phenoxy group, an indole group, and an amide group, more preferably at least one selected from the group consisting of a thiol group, an amino group, a hydroxy group, a guanidino group, a carboxy group, a phenoxy group, and an indole group, and even more preferably at least one selected from the group consisting of a thiol group, an amino group, a hydroxy group, a guanidino group, a carboxy group, a phenoxy group, and an indole group. The amino group may be at least one selected from the group consisting of an anidino group, a carboxy group, and a phenoxy group, more preferably at least one selected from the group consisting of a thiol group, an amino group, a hydroxy group, a guanidino group, and a carboxy group, even more preferably at least one selected from the group consisting of a thiol group, an amino group, a hydroxy group, and a guanidino group, particularly preferably at least one selected from the group consisting of a thiol group, an amino group, and a hydroxy group, particularly preferably at least one selected from the group consisting of a thiol group and an amino group, and most preferably a thiol group. The amino group may be, for example, the amino group contained in lysine. The hydroxy group may be, for example, the hydroxy group contained in serine, the hydroxy group contained in threonine, etc. The guanidino group may be, for example, the guanidino group contained in arginine. The carboxy group may be, for example, the carboxy group contained in glutamic acid, the carboxy group contained in aspartic acid, etc. The phenoxy group may be, for example, the phenoxy group possessed by tyrosine. The indole group may be, for example, the indole group possessed by tryptophan. The amide group may be, for example, the amide group possessed by glutamine, the amide group possessed by asparagine, etc. The alkynyl group may be an alkynyl group introduced by reacting a thiol group possessed by cysteine ​​with an acetylene halide.

[0063] The molecular weight of the first segment is, for example, preferably 200 to 1,000,000, more preferably 300 to 900,000, even more preferably 400 to 800,000, still more preferably 500 to 700,000, even more preferably 600 to 600,000, particularly preferably 1,000 to 600,000, even more preferably 3,000 to 600,000, even more preferably 5,000 to 600,000, even more preferably 10,000 to 600,000, and even more preferably 10,000 to 100,000.

[0064] When the molecular weight of the first segment is 200 or more, the first segment that functions as a hard segment relative to the second segment (soft segment) containing a molecular group with plasticizing function becomes sufficiently large. In this case, the rigidity of the synthetic leather formed using the polymer compound containing the polypeptide structure becomes sufficiently high, making it easier to use as a synthetic leather material. When the molecular weight of the first segment is 1,000,000 or less, the decrease in reactivity of the linking reaction is suppressed, making it easier to complete the reaction within a time that allows commercial production of the material from a chemical engineering perspective. As a result, it becomes easier to suppress the localization of unreacted second segments remaining in the synthetic leather material.

[0065] The molecular weight of the first segment and the molecular weight of the polypeptide backbone included in the first segment may be, for example, 1,000 or more, 2,000 or more, 3,000 or more, 4,000 or more, 5,000 or more, 6,000 or more, 7,000 or more, 8,000 or more, 9,000 or more, 10,000 or more, 20,000 or more, 30,000 or more, 40,000 or more, 50,000 or more, 60,000 or more, 70,000 or more, 80,000 or more, 90,000 or more, or 100,000 or more. The molecular weight of the first segment and the molecular weight of the polypeptide backbone included in the first segment may be 400,000 or less, 360,000 or less, 300,000 or less, or 200,000 or less.

[0066] The smaller the molecular weight of the first segment and polypeptide backbone, the greater their solubility in solvents. Therefore, when the molecular weight of the polypeptide backbone and / or the first segment is, for example, 200,000 or less or 100,000 or less, improving the efficiency of producing a polymer compound containing a target polypeptide structure is desirable when dissolving a compound containing a polypeptide backbone in a solvent and reacting it with a compound containing a molecular group capable of plasticizing the polypeptide backbone to obtain a polymer compound containing a polypeptide structure. Synthetic leather molded using the polymer compound containing a polypeptide structure thus obtained can be expected to have improved flexibility while maintaining a certain level of strength. When the molecular weight of the polypeptide backbone and / or the first segment is, for example, 200,000 or less or 100,000 or less, it is expected that the amount of the second segment used can be minimized to increase the flexibility of the polymer compound containing a polypeptide structure. The molecular weights of the first segment and the polypeptide backbone mentioned above are weight-average molecular weights.

[0067] The molecular weights referred to herein are values ​​measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Such electrophoresis is performed as follows: First, 200 μL of 2 M lithium chloride DMSO (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is added to 2 mg of powder sample, and the sample is dissolved by stirring at 80°C for 60 minutes and then at 95°C for 10 minutes. The sample is then diluted 50-fold with 10 M (mol / L) urea solution, further diluted 2-fold with sample buffer (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and heated at 95°C for 5 minutes to denature the protein. Next, an SDS-PAGE gel (manufactured by Bio-lad) is attached to an electrophoresis apparatus (manufactured by Bio-lad), the apparatus is filled with SDS buffer, and the electrophoresis apparatus is connected to a power supply (manufactured by Biocraft). Ten microliters of the denatured sample was added to each well of an SDS-PAGE gel, and a current of 30 mA was applied for 30 minutes. After electrophoresis, the SDS-PAGE gel was removed from the apparatus, immersed in Oriole fluorescent gel stain (Bio-lad), and shaken for 1 hour. The gel was then placed on a UV sample tray (Bio-lad), and a stained image was captured using a Gel Doc EZ gel imager (Bio-lad).

[0068] The number of amino acid residues constituting the polypeptide backbone may be 50 or more. The number of amino acid residues may be, for example, 100 or more, 150 or more, 200 or more, 250 or more, 300 or more, 350 or more, 400 or more, 450 or more, or 500 or more. The number of amino acid residues may be, for example, 5000 or less, 4500 or less, 4000 or less, 3500 or less, 3000 or less, 2500 or less, 2000 or less, 1500 or less, or 1000 or less. The fewer the number of amino acid residues, the higher the solubility in a solvent tends to be. Therefore, when the number of amino acid residues of the polypeptide according to this embodiment is, for example, 5000 or less or 2500 or less, when a compound containing a polypeptide backbone is dissolved in a solvent and reacted with a compound containing a molecular group having a plasticizing function for the polypeptide backbone to obtain a polymer compound containing a polypeptide structure, it may be desirable to improve the efficiency of producing a polymer compound containing a desired polypeptide structure. Synthetic leather made using the polymer compound containing a polypeptide structure obtained in this way is expected to have improved flexibility while maintaining a certain level of strength.

[0069] The polypeptide backbone is a recombinant polypeptide backbone or a hydrophobic polypeptide backbone, and may be a hydrophobic recombinant polypeptide backbone.

[0070] A recombinant polypeptide refers to a polypeptide produced using genetic recombination technology. When the polypeptide backbone is a recombinant polypeptide backbone, the amino acid sequence can be easily modified, making it easy to control the characteristics and physical properties of polymeric compounds containing the polypeptide structure. When the polypeptide backbone is a recombinant polypeptide backbone, uniform molecular design is always possible, making it possible to stably obtain polypeptide backbones tailored to the intended purpose. This advantageously stabilizes the quality of polymeric compounds and synthetic leathers containing the desired polypeptide structure.

[0071] When the polypeptide backbone is a hydrophobic polypeptide backbone, the affinity of the molecular group having plasticizing function with the first segment is improved, allowing for the production of synthetic leather with greater flexibility. In addition, the water resistance of such synthetic leather is improved, which can advantageously extend the service life of synthetic leather, for example, when used as a general-purpose industrial material. The hydrophobicity or hydrophilicity of the entire polymer compound containing a polypeptide structure can be adjusted arbitrarily, for example, by controlling the hydrophobicity or hydrophilicity of the molecular group having plasticizing function with respect to the polypeptide backbone, which is contained in the second segment. When the polypeptide backbone is a hydrophobic polypeptide backbone, the entire polymer compound containing a polypeptide structure can be shifted toward the hydrophobic side compared to when the polypeptide backbone is a hydrophilic polypeptide backbone, thereby allowing the hydrophobicity or hydrophilicity of the entire polymer compound containing a polypeptide structure to be controlled over a wider range.

[0072] The hydrophobicity of a hydrophobic polypeptide backbone can be estimated using the average hydropathy index (hydrophobicity index) value described below as an index. The average hydropathy index value of a hydrophobic polypeptide backbone may be, for example, 0.00 or more, 0.10 or more, 0.20 or more, 0.22 or more, 0.25 or more, 0.30 or more, 0.35 or more, 0.40 or more, 0.45 or more, 0.50 or more, 0.55 or more, 0.60 or more, 0.65 or more, or 0.70 or more. The upper limit is not particularly limited, but may be, for example, 1.00 or less or 0.70 or less.

[0073] The hydrophobic polypeptide backbone preferably has low solubility in an aqueous lithium bromide solution (concentration: 9 M) at 60°C. This solubility can be evaluated using a polypeptide obtained by decomposing a compound (polypeptide) corresponding to the hydrophobic polypeptide backbone or a polymer compound containing a polypeptide structure and isolating only the hydrophobic polypeptide backbone. When the polypeptide is dissolved in an aqueous lithium bromide solution (concentration: 9 M) at 60°C, the maximum concentration may be, for example, less than 30% by mass, less than 25% by mass, less than 20% by mass, less than 15% by mass, less than 10% by mass, less than 5% by mass, or less than 1% by mass. The hydrophobic polypeptide backbone may also be completely insoluble in an aqueous lithium bromide solution (concentration: 9 M) at 60°C.

[0074] The hydrophobic polypeptide backbone preferably has a large water contact angle. The water contact angle can be evaluated by forming a film on a substrate, the film being composed of a polypeptide obtained by decomposing a compound (polypeptide) corresponding to the hydrophobic polypeptide backbone or a polymer compound containing a polypeptide structure and isolating only the hydrophobic polypeptide backbone. A polypeptide that forms a film such that the contact angle after 5 seconds of water being dropped onto the film is 55° or greater is preferred as the hydrophobic polypeptide backbone. The contact angle may be, for example, 60° or greater, 65° or greater, or 70° or greater.

[0075] The hydrophobic polypeptide backbone preferably has excellent hot water resistance. Hot water resistance can be evaluated using a polypeptide obtained by decomposing a compound (polypeptide) corresponding to the hydrophobic polypeptide backbone or a polymer compound containing a polypeptide structure and isolating only the hydrophobic polypeptide backbone. A preferred hydrophobic polypeptide backbone is a polypeptide that does not decompose even when a dispersion containing the polypeptide and water is prepared, the dispersion containing the polypeptide at 5% by mass, and is heated at 100°C for 5 hours.

[0076] The polypeptide backbone may include a protein-derived backbone or may consist solely of a protein-derived backbone. Preferably, the protein is an artificial protein. Artificial proteins include recombinant proteins and synthetic proteins. In other words, as used herein, "artificial protein" refers to a protein artificially produced. An artificial protein may have a domain sequence that is different from or identical to the amino acid sequence of a naturally occurring protein. Furthermore, an "artificial protein" may directly use the amino acid sequence of a naturally occurring protein, or may be a protein whose amino acid sequence has been modified based on the amino acid sequence of a naturally occurring protein (e.g., a protein whose amino acid sequence has been modified by modifying the gene sequence of a cloned naturally occurring protein), or may be a protein artificially designed and synthesized without relying on a naturally occurring protein (e.g., a protein having a desired amino acid sequence obtained by chemically synthesizing a nucleic acid encoding a designed amino acid sequence).

[0077] Furthermore, examples of artificial proteins include proteins that can be used for industrial purposes. "Usable for industrial purposes" means that the proteins can be used, for example, in various general-purpose materials for indoor and outdoor use. Specific examples of artificial proteins that can be used for industrial purposes include artificial structural proteins.

[0078] <Artificial structural proteins> Structural proteins refer to proteins involved in the structure of living organisms, proteins that constitute structures produced by living organisms, or proteins derived therefrom. Structural proteins also refer to proteins that self-aggregate under certain conditions to form structures such as fibers, films, resins, gels, micelles, and nanoparticles. Furthermore, structural proteins can also be said to be proteins that contain repeated motifs consisting of a characteristic amino acid sequence or a specific number of amino acid residues and form the skeleton of an organism or material. Artificial structural proteins are artificially produced versions of these structural proteins. Examples of such artificial structural proteins include artificial fibroin, artificial keratin, artificial collagen, artificial elastin, and artificial resilin.

[0079] When forming artificial structural proteins, amino acids with relatively small side chains are more likely to form hydrogen bonds and thus produce stronger molded products. Furthermore, alanine and glycine residues are amino acids with nonpolar side chains, and therefore are arranged so that they face inward during the folding process in polypeptide production, making them more likely to form α-helix or β-sheet structures. Therefore, a high proportion of amino acids such as glycine and alanine residues is desirable. From the viewpoint of obtaining molded products with superior strength, the alanine residue content may be, for example, 10-40%, and may be 12-40%, 15-40%, 18-40%, 20-40%, or 22-40%. From the viewpoint of obtaining molded products with superior strength, the glycine residue content may be, for example, 10-55%, and may be 11-55%, 13-55%, 15-55%, 18-55%, 20-55%, 22-55%, or 25-55%.

[0080] As used herein, the term "alanine residue content" refers to the number of alanine residues relative to the total number of amino acid residues constituting a protein, and is a value expressed by the following formula:

[0081] Alanine residue content = (number of alanine residues contained in protein / total number of amino acid residues in protein) x 100 (%)

[0082] Furthermore, the glycine residue content, serine residue content, threonine residue content, proline residue content, and tyrosine residue content have the same meaning as those obtained by replacing the alanine residue in the above formula with glycine residue, serine residue, threonine residue, proline residue, and tyrosine residue, respectively.

[0083] It is preferable that the artificial structural protein contains amino acids with relatively large side chains or flexible amino acids uniformly throughout its entire sequence to a certain extent. Specifically, the structural protein may contain a motif containing tyrosine, threonine, and proline residues in a repeated cycle. Such a structural protein is likely to inhibit the formation of strong intermolecular hydrogen bonds during processing of the molded article obtained by molding, thereby improving processability. For example, the total content of proline, threonine, and tyrosine residues in any 20 consecutive amino acid residues may be 5% or more, more than 5.5%, 6.0% or more, more than 6.5%, 7.0% or more, more than 7.5%, 8.0% or more, more than 8.5%, 9.0% or more, 10.0% or more, or 15.0% or more. Furthermore, for example, the total content of proline, threonine, and tyrosine residues in any 20 consecutive amino acid residues may be 50% or less, 40% or less, 30% or less, or 20% or less.

[0084] The artificial structural protein may have an amino acid sequence that includes a repeat sequence. That is, the artificial structural protein according to this embodiment may have multiple amino acid sequences (repeat sequence units) with high sequence identity within the artificial structural protein. The number of amino acid residues in the repeat sequence unit is preferably 6 to 200. Furthermore, the sequence identity between the repeat sequence units may be, for example, 85% or more, 90% or more, 95% or more, 96% or more, 97% or more, 98% or more, or 99% or more. The hydrophobicity index (hydropathy index) of the repeating sequence unit may be, for example, -0.80 or more, -0.70 or more, -0.60 or more, -0.50 or more, -0.40 or more, -0.30 or more, -0.20 or more, -0.10 or more, 0.00 or more, 0.22 or more, 0.25 or more, 0.30 or more, 0.35 or more, 0.40 or more, 0.45 or more, 0.50 or more, 0.55 or more, 0.60 or more, 0.65 or more, or 0.70 or more. The upper limit of the hydrophobicity index of the repeating sequence unit is not particularly limited, but may be, for example, 1.0 or less or 0.7 or less.

[0085] The artificial structural protein is (A) ｎ In the present specification, (A) ｎ The motif refers to an amino acid sequence that is mainly composed of alanine residues. (A) ｎ The number of amino acid residues in the motif may be 2 to 27, or may be an integer of 2 to 20, 2 to 16, or 2 to 12. ｎ The ratio of the number of alanine residues to the total number of amino acid residues in the motif may be 40% or more, 60% or more, 70% or more, 80% or more, 83% or more, 85% or more, 86% or more, 90% or more, 95% or more, or 100% (meaning that the motif is composed only of alanine residues).

[0086] The artificial structural protein may be artificial fibroin. Examples of fibroin include naturally occurring fibroin. Examples of naturally occurring fibroin include fibroin produced by insects or spiders. Natural fibroin is a fibrous protein with a molecular weight of approximately 370,000, composed of two subunits, and has a high content of glycine, alanine, serine, and tyrosine residues, with these amino acid residues accounting for nearly 90% of the total number of amino acid residues. Natural fibroin has a crystalline region rich in amino acid residues with relatively small side chains such as glycine, alanine, and serine, and an amorphous region containing amino acid residues with relatively large side chains such as tyrosine.

[0087] More specific examples of naturally occurring fibroins include fibroins whose sequence information is registered in NCBI GenBank. For example, among the sequences registered in NCBI GenBank that contain INV as a division, the sequence can be confirmed by extracting sequences in which spidroin, ampullate, fibroin, "silk and polypeptide," or "silk and protein" are described as keywords in the DEFINITION, a specific product character string from the CDS, or a specific character string in the TISSUE TYPE from the SOURCE.

[0088] As used herein, "artificial fibroin" refers to artificially produced fibroin (artificial fibroin). The artificial fibroin may be a fibroin having an amino acid sequence different from that of naturally occurring fibroin, or may be a fibroin having an amino acid sequence identical to that of naturally occurring fibroin. The artificial fibroin can be produced by known methods, for example, by the method described in WO 2019 / 194263.

[0089] Artificial fibroin may be a fibrous protein having a structure similar to that of naturally occurring fibroin, or may be a fibroin having a sequence similar to the repetitive sequence of naturally occurring fibroin. The "similar sequence to the repetitive sequence of fibroin" may be a sequence actually found in naturally occurring fibroin, or a sequence similar thereto.

[0090] "Artificial fibroin" may be a naturally occurring fibroin whose amino acid sequence has been modified (e.g., an amino acid sequence modified by modifying the gene sequence of a cloned naturally occurring fibroin), as long as it has the amino acid sequence specified in this disclosure. Alternatively, it may be an artificially designed amino acid sequence independent of naturally occurring fibroin (e.g., an artificial fibroin having a desired amino acid sequence obtained by chemically synthesizing a nucleic acid encoding a designed amino acid sequence). Artificial fibroins whose amino acid sequence has been modified are also included in the category of artificial fibroin, provided that the amino acid sequence differs from that of naturally occurring fibroin. Examples of artificial fibroins include artificial silk fibroin (a silk protein produced by silkworms) and artificial spider silk fibroin (a spider silk protein produced by spiders) whose amino acid sequence has been modified. Because artificial fibroin is relatively easy to fibrillate and has high fiber-forming ability, it is preferable for the molding material to contain, and more preferably consist of, artificial spider silk fibroin.

[0091] Artificial fibroin has the formula 1: [(A) ｎ motif-REP] ｍ , or Formula 2: [(A) ｎ motif-REP] ｍ -(A) ｎThe artificial fibroin may be a protein containing a domain sequence represented by a motif. The artificial fibroin may have further amino acid sequences (N-terminal sequence and C-terminal sequence) added to either or both of the N-terminal and C-terminal sides of the domain sequence. The N-terminal sequence and C-terminal sequence are typically, but are not limited to, regions that do not have repeats of the amino acid motif characteristic of fibroin and consist of about 100 amino acid residues.

[0092] As used herein, a "domain sequence" refers to a sequence of a molecule having the formula 1: [(A) ｎ motif-REP] ｍ , or Formula 2: [(A) ｎ motif-REP] ｍ -(A) ｎ The amino acid sequence represented by the motif (A) ｎ The motif shows an amino acid sequence mainly consisting of alanine residues, and the number of amino acid residues is 2 to 27. (A) ｎ The number of amino acid residues in the motif may be an integer of 2 to 20, 4 to 27, 4 to 20, 8 to 20, 10 to 20, 4 to 16, 8 to 16, or 10 to 16. ｎ The ratio of the number of alanine residues to the total number of amino acid residues in the motif may be 40% or more, and may be 60% or more, 70% or more, 80% or more, 83% or more, 85% or more, 86% or more, 90% or more, 95% or more, or 100% (meaning that the motif is composed of only alanine residues). ｎ At least seven of the motifs may be composed of only alanine residues. REP represents an amino acid sequence composed of 2 to 200 amino acid residues. REP may also be an amino acid sequence composed of 10 to 200 amino acid residues. m represents an integer of 2 to 300, and may be an integer of 10 to 300. (A) ｎ The motifs may have the same or different amino acid sequences, and the multiple REPs may have the same or different amino acid sequences.

[0093] Specific examples of artificial fibroins include, for example, an artificial fibroin derived from a major spinal dragline silk protein produced in the major ampullate gland of spiders (first artificial fibroin) as described in WO 2019 / 194263, an artificial fibroin having a domain sequence with a reduced content of glycine residues (second artificial fibroin), (A) ｎ An artificial fibroin having a domain sequence with a reduced motif content (third artificial fibroin), a glycine residue content, and (A) ｎ These include an artificial fibroin with a reduced motif content (fourth artificial fibroin), an artificial fibroin with a domain sequence containing a region with a locally high hydrophobic index (fifth artificial fibroin), and an artificial fibroin with a domain sequence with a reduced content of glutamine residues (sixth artificial fibroin). The definitions of the first to sixth artificial fibroins are set forth in WO 2019 / 194263, the contents of which are incorporated herein by reference.

[0094] The artificial fibroin may contain a tag sequence at either or both of the N-terminus and C-terminus, which allows the artificial fibroin to be isolated, immobilized, detected, visualized, and the like.

[0095] An example of a tag sequence is an affinity tag that utilizes specific affinity (binding property, affinity) with other molecules. A specific example of an affinity tag is a histidine tag (His tag). A His tag is a short peptide consisting of approximately 4 to 10 histidine residues, and has the property of specifically binding to metal ions such as nickel, so it can be used to isolate artificial fibroin by chelating metal chromatography. A specific example of a tag sequence is the amino acid sequence shown in SEQ ID NO: 8 (an amino acid sequence including a His tag sequence and a hinge sequence).

[0096] Furthermore, tag sequences such as glutathione-S-transferase (GST) that specifically binds to glutathione, and maltose-binding protein (MBP) that specifically binds to maltose can also be used.

[0097] Furthermore, an "epitope tag" that utilizes an antigen-antibody reaction can also be used. By adding an antigenic peptide (epitope) as a tag sequence, an antibody specific to the epitope can be bound. Examples of epitope tags include HA (peptide sequence of influenza virus hemagglutinin) tag, myc tag, and FLAG tag. By using an epitope tag, artificial fibroin can be easily purified with high specificity.

[0098] Furthermore, a tag sequence that can be cleaved with a specific protease can also be used. By treating the protein adsorbed via the tag sequence with the protease, the artificial fibroin from which the tag sequence has been cleaved can be recovered.

[0099] Specific examples of artificial fibroins include those represented by SEQ ID NOS: 1 to 7. The artificial fibroin may be an artificial fibroin represented by SEQ ID NOS: 1 to 7 or an artificial fibroin containing an amino acid sequence having 90% or more sequence identity with these amino acid sequences. The respective contents of alanine residues, glycine residues, serine residues, threonine residues, tyrosine residues, glutamine residues, and lysine residues in the artificial fibroins represented by SEQ ID NOS: 1 to 7 are shown in Table 1 below. The artificial fibroins represented by SEQ ID NOS: 1 and 7 correspond to the aforementioned fourth artificial fibroin, the artificial fibroins represented by SEQ ID NOS: 2, 3, 5, and 6 correspond to the aforementioned sixth artificial fibroin, and the artificial fibroin represented by SEQ ID NOS: 4 corresponds to the aforementioned first artificial fibroin.

[0100] (Table 1)

[0101] The artificial fibroin may be an artificial fibroin having at least two or more characteristics of the first artificial fibroin, the second artificial fibroin, the third artificial fibroin, the fourth artificial fibroin, the fifth artificial fibroin, and the sixth artificial fibroin.

[0102] The molecular weight of the artificial fibroin according to this embodiment is not particularly limited, and may be, for example, 2 kDa or more and 700 kDa or less. The molecular weight of the artificial fibroin according to this embodiment may be, for example, 2 kDa or more, 3 kDa or more, 4 kDa or more, 5 kDa or more, 6 kDa or more, 7 kDa or more, 8 kDa or more, 9 kDa or more, 10 kDa or more, 20 kDa or more, 30 kDa or more, 40 kDa or more, 50 kDa or more, 60 kDa or more, 70 kDa or more, 80 kDa or more, 90 kDa or more, or 100 kDa or more, or 700 kDa or less, 600 kDa or less, 500 kDa or less, 400 kDa or less, less than 360 kDa, 300 kDa or less, or 200 kDa or less.

[0103] [Second Segment] The second segment includes a molecular group having a plasticizing function for the polypeptide backbone. A molecular group having a plasticizing function for the polypeptide backbone refers to a molecular group in which the intermolecular force between the molecular groups is weaker than the intermolecular force between the polypeptide backbones, and when the two are mixed, the flexibility of the material can be improved compared to the polypeptide backbone alone. A molecular group having a plasticizing function for the polypeptide backbone can also be a molecular group having a lower melting point or glass transition temperature than the polypeptide backbone. The molecular group having a plasticizing function for the polypeptide backbone may be, for example, a polyether, polyester, or polycarbonate. The polyether as the molecular group may be, for example, polyethylene glycol (PEG) or polytetramethylene glycol (PTMG). The plasticizing function can also be referred to as a function of improving flexibility or a function of increasing breaking elongation in bending and / or tension. The molecular group having a plasticizing function for the polypeptide backbone is preferably biodegradable or derived from biomass. This is expected to further increase the biodegradability and biovalue of the synthetic leather as a whole, and may also lead to further reductions in the energy required to produce the synthetic leather.

[0104] The second segment may contain a plurality of the molecular groups. The second segment may contain a plurality of the molecular groups, and the plurality of molecular groups may be connected to each other. The connections between the molecular groups may be partially branched. By partially branching the connections, the second segment can have a branched structure consisting of a plurality of the molecular groups, and each branch can form multiple bonds with the first segment. In other words, by introducing a branch into some of the connections, a network structure between the first segment and the second segment can be formed. In this way, when the second segment contains a plurality of the molecular groups and these molecular groups are connected to each other, the design options for the second segment can be broadened, and, for example, the flexibility of the synthetic leather can be more easily adjusted. When the second segment contains only one of the molecular groups, multiple second segments may be connected to each other, and at least one of the multiple second segments may be bonded to the first segment. Alternatively, multiple second segments may be bonded to one first segment. When multiple second segments are connected to each other, a branch may be introduced into some of the connections between the multiple second segments to form a network of second segments.

[0105] The second segment may include, for example, a skeleton derived from at least one selected from the group consisting of polyether, polyester, polycarbonate, polyamide, polyol (such as polyvinyl alcohol), polyolefin, polyacetal, polyketal, poly(meth)acrylate, silicone, polyurethane, polyalkyleneimine, phenol resin, urea resin, melamine resin, and polysaccharide, and may preferably include at least one functional group selected from the group consisting of a polyether group, a polyester group, a polycarbonate group, a polyamide group, a polyol group (such as a polyvinyl alcohol group), and a modified polysaccharide group, or may include at least one functional group selected from the group consisting of an ether group, an ester group, a carbonate group, an amide group, and a modified polysaccharide group. The second segment may include, for example, at least one structural unit selected from the group consisting of structural units having an ether bond, an ester bond, a carbonate ester bond (carbonate bond), an amide group, a siloxane bond, a urethane bond, or a urea bond, and can also be said to include at least one structural unit selected from the group consisting of structural units having an alkylene group, a substituted alkylene group, an oxymethylene group, an alkyleneimine group, or a modified polysaccharide group.

[0106] Examples of polyether groups include functional groups derived from polyalkylene glycols such as polyethylene glycol, polypropylene glycol, ethylene oxide / propylene oxide copolymer, and polybutylene glycol (polytetramethylene glycol (PTMG)). When these polyether groups are contained in the second segment, the polyether group may be directly bonded to a heteroatom (O, N, S) in an ester group, thioester group, or amide group of a linker (described below) contained in the second segment, if necessary. Alternatively, the polyether group may be directly bonded to a heteroatom (O, N, S) in an ester group, thioester group, or amide group of a polypeptide backbone contained in the first segment. In this case, the entire polyether group is more likely to separate from the linker and / or the first segment, thereby increasing the biodegradation rate of the polyether group.

[0107] Examples of the polyester group include functional groups derived from polyesters such as polylactic acid, poly(3-hydroxybutanoic acid), polyhydroxybutanoic acid / hydroxyvaleric acid copolymer, polyhydroxybutanoic acid / 4-hydroxybutanoic acid copolymer, polyhydroxybutanoic acid / hydroxyhexanoic acid copolymer, polytrimethylene terephthalate, butanediol / long-chain dicarboxylic acid copolymer, polyethylene terephthalate, polybutylene succinate, polybutylene succinate-adipate copolymer, polybutylene adipate-terephthalate copolymer, polycaprolactone, and polytrimethylene furandicarboxylate (PTF). Of the above polyesters, the polyester group is preferably a functional group derived from a material classified as a biomass plastic or biodegradable plastic, such as polycaprolactone.

[0108] Examples of the polycarbonate group include functional groups derived from polycarbonates having an aliphatic hydrocarbon chain as the main skeleton, such as 1,6-hexanediol polycarbonate, 1,5-pentanediol polycarbonate, and 1,10-decanediol carbonate.

[0109] Examples of the polyamide group include functional groups derived from polyamides such as nylon 3, nylon 4, nylon 5, nylon 6, nylon 11, and nylon 610. Of the above-mentioned polyamides, the polyamide group is preferably a functional group derived from a polyamide classified as a biomass plastic or a biodegradable plastic.

[0110] Examples of the polyol group (such as a polyvinyl alcohol group) include functional groups derived from polyols (such as polyvinyl alcohols) such as polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Of the above-mentioned polyols, the polyol group is preferably a functional group derived from a polyol classified as a biomass plastic or a biodegradable plastic.

[0111] The modified polysaccharide group may be, for example, a functional group derived from a compound obtained by chemically modifying cellulose, starch, chitin, chitosan, etc. Examples of the chemically modified compound include cellulose acetate, ethyl cellulose, starch acetate, hydroxypropylated starch, carboxymethyl chitin, and carboxymethyl chitosan.

[0112] The second segment may further include a linker in addition to the molecular group having a plasticizing function for the polypeptide backbone. In this case, the molecular group and the polypeptide backbone may be bonded via the linker. Examples of the linker include a group formed by bonding an electrophilic functional group represented by any of the formulas (1) to (20) described below with a nucleophilic functional group contained in Compound A described below.

[0113] The molecular weight of the second segment (a group of molecules having a plasticizing function on the polypeptide backbone) may be, for example, 200 to 500,000, 300 to 400,000, 350 to 350,000, 400 to 300,000, 500 to 200,000, 600 to 100,000, 700 to 50,000, 800 to 10,000, 900 to 7,500, or 1,000 to 5,000.

[0114] When the molecular weight of the second segment is 200 or more, localization of the molecular group having a plasticizing function within the three-dimensional structure of the molecule is easily suppressed, and the mass ratio of the molecular group having a plasticizing function that must be introduced to exert a certain level of function can be sufficiently reduced, which may result in shorter reaction times and lower reaction temperatures in the production of polymer compounds containing a polypeptide structure.

[0115] When the molecular weight of the second segment is 500,000 or less, the molecular weight falls within an appropriate range, and a decrease in the binding reactivity of the second segment with the first segment is more easily suppressed.

[0116] The molecular weight of the second segment is a weight average molecular weight, which is generally determined by a known method using GPC.

[0117] The molecular weight of the second segment (a molecular group having a plasticizing function for the polypeptide backbone) relative to the molecular weight of the first segment (polypeptide backbone) can be adjusted appropriately depending on the application of the polymer compound containing a polypeptide structure, etc. The molecular weight of the second segment (the total molecular weight when two or more second segments are bound to one first segment) is, for example, preferably 1 to 10,000, more preferably 1.5 to 9,000, even more preferably 2 to 8,000, still more preferably 3 to 7,000, even more preferably 5 to 5,000, still more preferably 7 to 3,000, and even more preferably 10 to 2,000, based on the molecular weight of the first segment (100).

[0118] When the ratio of the molecular weight of the second segment to the molecular weight of the first segment is 1 or more, the flexibility of the synthetic leather obtained using the polymer compound containing a polypeptide structure can be further increased. When the ratio of the molecular weight of the second segment to the molecular weight of the first segment is 10,000 or less, the synthetic leather has sufficient plasticity (flexibility) and the rigidity of the synthetic leather material can be further improved. When the ratio of the molecular weight of the second segment to the molecular weight of the first segment is within the above-mentioned range, it is possible to produce synthetic leather with excellent flexibility.

[0119] The molecular weight of the second segment and the molecular weight of the molecular group having a plasticizing function for the polypeptide backbone may be, for example, 1.4 or more, 1.5 or more, 1.6 or more, 1.7 or more, 1.8 or more, 1.9 or more, 2.0 or more, 5.0 or more, 10 or more, 20 or more, 30 or more, or 40 or more, when the molecular weight of the first segment or the molecular weight of the polypeptide backbone contained in the first segment is defined as 100 (preferably when the molecular weight of the polypeptide backbone contained in the first segment is defined as 100). The upper limit is not particularly limited, and may be, for example, 1,000 or less, 800 or less, 600 or less, 400 or less, 200 or less, 100 or less, 80 or less, 70 or less, 60 or less, or 50 or less. The molecular weight of the second segment, when the molecular weight of the first segment is taken as 100, is preferably in the range of 1 to 1,000, more preferably in the range of 1 to 800, even more preferably in the range of 1 to 600, even more preferably in the range of 1 to 400, even more preferably in the range of 1 to 200, even more preferably in the range of 1 to 100, preferably in the range of 1 to 70, more preferably in the range of 1.5 to 60, even more preferably in the range of 1.5 to 50, and particularly preferably in the range of 2.0 to 50. When the ratio of the molecular weight of the first segment (polypeptide backbone) to the molecular weight of the second segment (molecular group having a plasticizing function for the polypeptide backbone) is a value within the above range, for example, in synthetic leather obtained using a polymer compound containing a polypeptide structure, it can be expected that the properties of the first segment due to the presence of the polypeptide backbone (e.g., high mechanical strength) will be sufficiently maintained while improving flexibility, extensibility, etc. The ratio of the molecular weight of the second segment to the molecular weight of the first segment taken as 100 is determined in terms of weight average molecular weight.

[0120] The content ratio of the first segment (polypeptide backbone) to the second segment (molecular group having plasticizing function) in the polymer compound containing a polypeptide structure can be adjusted as appropriate depending on the intended use of the synthetic leather. This content ratio, in mass ratio, when the second segment is taken as 100, may be, for example, 50 or more, 60 or more, 70 or more, 80 or more, 90 or more, 100 or more, 110 or more, 150 or more, 200 or more, 250 or more, 300 or more, 350 or more, 400 or more, 450 or more, 500 or more, 550 or more, or 600 or more of the first segment. The upper limit of this value is not particularly limited, but may be 1000 or less, 900 or less, 800 or less, or 700 or less. By ensuring that the content ratio of the first segment to the second segment in the polymer compound containing a polypeptide structure falls within the above range, wasteful use of the second segment is suppressed, thereby reducing the production cost of the polymer compound containing a polypeptide structure. In a polymer compound containing a polypeptide structure, the content ratio of the second segment to the first segment can be advantageously reduced by, for example, reducing the molecular weight of the second segment.

[0121] In the above description of the embodiment, the linker has been described as a component of the second segment, but it may be treated separately from the second segment. The linker can also be treated as a component of the first segment. Although the molecular weight of the linker portion is smaller than that of the polypeptide backbone and the molecular group, when the linker is treated separately from the second segment, the range obtained by subtracting the molecular weight of the linker portion from the molecular weight of the second segment is treated as the preferred molecular weight range of the second segment. Similarly, when the linker portion is treated as a component of the first segment, the range obtained by adding the molecular weight of the linker portion to the molecular weight of the first segment is treated as the preferred molecular weight range of the first segment.

[0122] [Method for Producing Block Copolymers] -First Aspect of the Method for Producing Block Copolymers- A block copolymer in a polymer compound containing a polypeptide structure is preferably obtained by a production method including a step of mechanochemically treating a mixture containing a compound having a polypeptide backbone (hereinafter also referred to as "compound A") and a compound having a molecular group capable of plasticizing the polypeptide backbone (hereinafter also referred to as "compound B"). Compound A forms the first segment, and compound B forms the second segment. In other words, the block copolymer contained in the polymer compound containing a polypeptide structure is preferably obtained by mechanochemically treating a mixture containing the compound having the polypeptide backbone and a compound having a molecular group capable of plasticizing the polypeptide backbone. Such a method utilizing a solid-state reaction allows the amount of organic solvent used to be zero or reduced as much as possible during the production of the block copolymer.

[0123] Preferred embodiments of the polypeptide backbone in Compound A are as described above. Compound A is preferably a protein. The definition of protein used in the method according to this embodiment can be referenced to the definition of protein described above. The protein preferably includes a hydrophobic protein. Furthermore, the hydrophobic protein preferably has a hydropathic index greater than 0. The protein may be an artificial protein, and preferably includes an artificial structural protein.

[0124] In certain embodiments, for example, compound A has two or more nucleophilic functional groups and compound B has two or more electrophilic functional groups. In this embodiment, the nucleophilic functional groups and the electrophilic functional groups are bonded to each other to form a block copolymer comprising compound A and compound B as monomer units. In a preferred embodiment, compound A has two or more hydroxyl, amino, or thiol groups, and compound B has two or more hydroxy-, amine-, or thiol-reactive groups.

[0125] The electrophilic functional group is, for example, a group represented by any one of formulas (1) to (20), and preferred electrophilic functional groups are groups represented by formulas (1), (2), (6) to (8), (16), or (19), and more preferred electrophilic functional groups are groups represented by formulas (1), (2), or (6). Preferred combinations of nucleophilic functional groups and electrophilic functional groups include a hydroxyl group and a hydroxy-reactive group represented by any one of formulas (2) to (9), (13) to (17), and (19), an amino group and an amine-reactive group represented by any one of formulas (2) to (9), (13) to (17), and (19), and a thiol group and a thiol-reactive group represented by any one of formulas (1) to (6), (8), (10) to (15), and (18). In formulas (1) to (20), R ２ In formulae (2) to (8) and (13) to (15), Y represents, independently of each other, an oxygen atom, a sulfur atom, or NR １ indicates R １ represents a hydrogen atom, a hydrocarbon group, an aromatic group, a carbonyl group, or a sulfonyl group. In formulas (2) to (6) and (10) to (15), R each independently represents a hydrogen atom, a hydrocarbon group, or an aromatic group. In formulas (8) and (16), Z represents a halogen atom, a sulfonate ester group, or a fluorine-containing carboxylate ester group. In formula (19), X represents a halogen atom.

[0126] The amount of compound B used may be 1.5 to 7 equivalents per nucleophilic functional group contained in compound A. The amount of compound B used may preferably be 1.5 to 6.5 equivalents, 1.5 to 6 equivalents, 1.5 to 5.5 equivalents, 1.5 to 5 equivalents, 1.5 to 4 equivalents, 2 to 7 equivalents, 2 to 6.5 equivalents, 2 to 6 equivalents, 2 to 5.5 equivalents, 2 to 5 equivalents, 2 to 4.5 equivalents, 2.5 to 7 equivalents, 2.5 to 6.5 equivalents, 2.5 to 6 equivalents, 2.5 to 5.5 equivalents, 2.5 to 5 equivalents, or 2.5 to 4.5 equivalents per nucleophilic functional group. "Equivalent per nucleophilic functional group" means the molar equivalent of compound B per nucleophilic functional group contained in compound A. By setting the amount of compound B used to a value within the above range, the reactivity or reaction efficiency between compound A and compound B in the mechanochemical treatment is enhanced, and the target block copolymer can be obtained more efficiently.

[0127] Mechanochemical processing is a process in which a chemical reaction is induced by the direct absorption of mechanical energy. Such mechanical energy may be exerted, for example, by impact force or shear force. Specifically, such mechanochemical processing is carried out using a tumbling ball mill, a media-agitated mill, a planetary mill, a jet mill, a mixer mill, an extruder (twin-screw extruder), or the like. Specifically, compound A and compound B are placed in a grinding jar, and media balls, etc., are added depending on the type of mill used. The grinding jar is then placed in a mixer mill device and vibrated at a predetermined frequency and reaction time. At this time, a solvent, a base, a reaction accelerator, etc. may be further added to the grinding jar. Alternatively, compound A and compound B are placed in a mixer mill, and the milling procedure is initiated, followed by continuous kneading of the reactants. At this time, a solvent, a base, a reaction accelerator, etc. may be further added to the mixer mill. Alternatively, compound A and compound B are placed in an extruder and kneaded. At this time, a solvent, a base, a reaction accelerator, etc. may be further added to the extruder. Furthermore, if mechanochemical treatment is carried out using an extruder, it becomes possible to continuously produce the desired block copolymer.

[0128] The frequency can be adjusted appropriately by those skilled in the art depending on the reaction, and may be, for example, 10 to 50 Hz, 10 to 45 Hz, 10 to 40 Hz, 10 to 35 Hz, 15 to 50 Hz, 15 to 45 Hz, 15 to 40 Hz, 15 to 35 Hz, 20 to 50 Hz, 20 to 45 Hz, 20 to 40 Hz, or 20 to 35 Hz.

[0129] The reaction time can be set to the point where the raw material compound A disappears or a certain level of the block copolymer is detected by infrared (IR) absorption spectroscopy, gel filtration chromatography (GPC), etc. The reaction time may be any time, for example, 30 to 240 minutes, 30 to 210 minutes, 30 to 180 minutes, 30 to 150 minutes, 30 to 120 minutes, 30 to 110 minutes, 30 to 100 minutes, 30 to 95 minutes, 60 to 240 minutes, 60 to 210 minutes, 60 to 180 minutes, 60 to 150 minutes, 60 to 120 minutes, 60 to 110 minutes, 60 to 100 minutes, 6 ... The time may be up to 95 minutes, 70 to 240 minutes, 70 to 210 minutes, 70 to 180 minutes, 70 to 150 minutes, minutes, 70 to 120 minutes, 70 to 110 minutes, 70 to 100 minutes, 70 to 95 minutes, 80 to 240 minutes, 80 to 210 minutes, 80 to 180 minutes, 80 to 150 minutes, minutes, 80 to 120 minutes, 80 to 110 minutes, 80 to 100 minutes, or 80 to 95 minutes.

[0130] The solvent may be any solvent capable of swelling compound A or capable of dissolving at least one of compound A and compound B. However, it must be a compound that is liquid at room temperature and normal pressure and does not chemically react with compound A. Mechanochemical treatment using such a solvent is known as liquid-assisted grinding (LAG), and is a method in which the desired reaction proceeds more efficiently by adding a small amount of solvent to a grinding jar. Examples of such solvents include alcoholic solvents such as methanol and ethanol, and aprotic polar solvents such as dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methylpiperidone (NMP), and dihydrolevoglucosenone. The amount of solvent used may be, for example, 0.01 g to 1 g, or may be 0.01 g to 0.8 g, 0.01 g to 0.6 g, 0.01 g to 0.4 g, or 0.01 g to 0.2 g per 1 g of compound A. In other words, the amount of solvent used may be, for example, 1 to 100% by mass, or may be 1 to 80% by mass, 1 to 60% by mass, 1 to 40% by mass, or 1 to 20% by mass, relative to compound A. It is believed that a trace amount of solvent forms a microscopic reaction field by swelling compound A or locally dissolving compound A. Note that the addition of a solvent is not always necessary; for example, when compound B is a liquid at room temperature and normal pressure and has the above-mentioned function as a solvent, the addition of a solvent may not be necessary.

[0131] After the reaction is complete, the mixture may be removed from the grinding jar and washed with a solvent. Washing can remove unreacted substances and excess by-products produced by the reaction. Examples of solvents used for washing include water, methanol, ethanol, acetonitrile, acetone, tetrahydrofuran, ethyl acetate, and hexane. After washing, the product may be dried to distill off the solvent used for washing. Drying may be performed under reduced pressure.

[0132] The average particle size of the block copolymer according to this embodiment is preferably 1 to 80 μm, 1 to 50 μm, 2 to 50 μm, 2 to 40 μm, 4 to 25 μm, 5 to 25 μm, 8 to 25 μm, or 8 to 16 μm. When the average particle size is within the above range, the copolymer has excellent handleability. The average particle size is measured, for example, by the same method as used to measure the particle size of powder 6 described above.

[0133] The block copolymer according to this embodiment is obtained as a powder with a smaller average particle size and a more uniform particle size by mechanochemically treating a mixture containing compound A and compound B and then freeze-drying it. The average particle size of the block copolymer powder obtained by freeze-drying is, for example, about 1 to 30 μm, 1 to 20 μm, 1 to 10 μm, or 2 to 8 μm. Such powdered block copolymers are easier to handle and allow for fine adjustment of the amount used. Moreover, the freeze-dried block copolymer not only has a small average particle size, but also is expected to loosen the tertiary structure of compound A, thereby improving its dispersibility in aqueous media (aqueous liquids) such as water, basic aqueous solutions, acidic aqueous solutions, and neutral aqueous solutions containing inorganic salts, as well as its solubility in solvents. In particular, when the block copolymer powder obtained by mechanochemical treatment or an aqueous dispersion obtained by dispersing the block copolymer powder obtained by further freeze-drying it in an aqueous medium is applied to a substrate surface, it can be applied more uniformly and without unevenness. This allows for the formation of a more uniform coating film with as little unevenness as possible. That is, the aqueous dispersion of the block copolymer powder can also be useful as a coating liquid for forming a coating film. Furthermore, the aqueous dispersion of the block copolymer powder can be applied to the surface of a substrate, followed by laminating another substrate thereon, and then curing the block copolymer to bond the two substrates. In other words, the aqueous dispersion of the block copolymer according to this embodiment can also be useful as a water-dispersible adhesive. When the aqueous dispersion of the block copolymer is used as a coating liquid, for example, a predetermined colorant or an additive commonly used in coating liquids or the like may be added, blended, or mixed with the aqueous dispersion of the block copolymer. When the aqueous dispersion of the block copolymer is used as a water-dispersible adhesive, an additive commonly used in adhesives or the like may be added, blended, or mixed with the aqueous dispersion of the block copolymer. Since the coating liquid and water-dispersible adhesive made from the aqueous dispersion of the block copolymer according to this embodiment use an aqueous medium such as water as a solvent, they are suitable for application to or adhesion of materials with low organic solvent resistance, and the odor characteristic of organic solvents can also be reduced.

[0134] Block copolymers produced by mechanochemical methods use no organic solvents or only a very small amount of organic solvent (an amount sufficient to swell molecules capable of plasticizing compound A or compound B) in the production process, so that organic solvents are less likely to remain and the copolymers can be easily purified into powders.

[0135] The block copolymer powder thus obtained, or a powder obtained by pulverizing the block copolymer by a known method as necessary, can be used as the powder of the polymer compound containing a polypeptide structure to be placed on the above-mentioned base fabric layer in the method for producing synthetic leather of this embodiment, or as the polymer compound containing a polypeptide structure for forming the above-mentioned resin film A.

[0136] - Second Aspect of Method for Producing Block Copolymer - Furthermore, a block copolymer in a polymer compound containing a polypeptide structure is also preferably produced by a method comprising reacting, by heating, in an organic solvent, a polypeptide having at least one mercapto group (hereinafter also referred to as "compound C") and a compound containing at least one structure selected from the group consisting of polyethers, polyesters, and polycarbonates, which has two structures represented by the following formula (M-1) or formula (M-2) (hereinafter also referred to as "compound D"). In formula (M-1), M is H, Na, K, or NHEt ３ , or NHEtiPr ２ In this specification, Et represents an ethyl group, and iPr represents an isopropyl group. １ represents a hydrogen atom or a methyl group.

[0137] The compound C forms the first segment, and the compound D forms the second segment.

[0138] <<Compound C>> Compound C is preferably a compound containing the above-described first segment. Here, the mercapto group in Compound C is preferably a mercapto group contained in a cysteine ​​residue in a polypeptide structure. Other preferred aspects of the first segment in Compound C are as described above.

[0139] In the above production method, the amount of compound C may be, for example, more than 1 part by mass, 2 parts by mass or more, 5 parts by mass or more, more than 5 parts by mass, 6 parts by mass or more, 7 parts by mass or more, or 8 parts by mass or more, relative to 100 parts by mass of the organic solvent. In the production method according to the present disclosure, the amount of compound C may be, for example, 50 parts by mass or less, 30 parts by mass or less, 20 parts by mass or less, or 15 parts by mass or less, relative to 100 parts by mass of dimethyl sulfoxide. When the upper limit of the amount of compound C is within the above range, the reaction can proceed while more sufficiently suppressing the generation of by-products and gelation.

[0140] <<Compound D>> Preferred embodiments of the polyether, polyester, and polycarbonate in Compound D are the same as those preferred embodiments in the second segment described above.

[0141] In the above production method, the ratio of the number of moles of the structure represented by formula (M-1) or formula (M-2) in compound D to the number of moles of mercapto groups in compound C may be, for example, 0.1 times or more, 0.2 times or more, 0.5 times or more, or 0.7 times or more. By setting this ratio within the above range, the reaction can proceed while further suppressing a decrease in reactivity. Furthermore, in the above production method, the ratio of the number of moles may be, for example, 5.0 times or less, 3.0 times or less, 1.5 times or less, or 0.8 times or less. By setting this ratio within the above range, the reaction can proceed while further suppressing the generation of by-products and gelation. By adjusting the above molar ratio, the number of polyether structures, etc. in the obtained polymer compound can be adjusted.

[0142] <<Organic Solvent>> The organic solvent is not particularly limited as long as it can dissolve Compound C and Compound D, but dimethyl sulfoxide is preferred.

[0143] <<Base>> Here, during the heating reaction, it is preferable to further contain a base in addition to Compound C and Compound D. By containing a base, the mercapto group in Compound C can be activated, and the Michael addition reaction between the functional group represented by Formula (M-1) and the mercapto group can be promoted. Examples of the base include primary amines, secondary amines, tertiary amines, nitrogen-containing ring compounds, nitrogen-containing aromatic compounds, and inorganic bases. Examples of primary amines include ethanolamine and hexamethylenediamine. Examples of secondary amines include diethylamine, methylethylamine, and N-methylbutylamine. Examples of tertiary amines include triethylamine, diethylmethylamine, and DIPEA (N,N-diisopropylethylamine). Examples of nitrogen-containing ring compounds include quinuclidine, DABCO (1,4-diazabicyclo[2.2.2]octane), DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), and DBN (1,5-diazabicyclo[4.3.0]non-5-ene). Examples of nitrogen-containing aromatic compounds include pyridine and imidazole. Examples of inorganic bases include sodium hydroxide, potassium hydroxide, sodium bicarbonate, potassium bicarbonate, sodium carbonate, potassium carbonate, cesium carbonate, tripotassium phosphate, sodium acetate, and potassium acetate.

[0144] The lower limit of the amount of the base may be, for example, 0.01 parts by mass or more, 0.05 parts by mass or more, 0.1 parts by mass or more, or 0.5 parts by mass or more, based on the mass of compound C. By setting the lower limit of the amount of the base within the above range, the reaction between the mercapto group of compound C and the unsaturated bond represented by formula (M-1) or general formula (M-2) of compound D can be further promoted. The upper limit of the amount of the base may be, for example, 50 parts by mass or less, 20 parts by mass or less, 10 parts by mass or less, or 5 parts by mass or less, based on the mass of the polypeptide. By setting the upper limit of the amount of the base within the above range, molecular decomposition due to the influence of remaining base can be further suppressed, allowing the synthesis of the desired polymer compound. The amount of the base may be adjusted within the above range, and may be, for example, 0.05 to 50 parts by mass or 0.1 to 10 parts by mass, based on the mass of the polypeptide.

[0145] <<Reducing Agent>> Here, during the heating reaction, it is also preferable to further contain a reducing agent in addition to Compound C and Compound D. The reducing agent itself is stable in dimethyl sulfoxide, is unlikely to undergo a Michael addition reaction with the functional group represented by Formula (M-1) or Formula (M-2), and can inhibit the formation of disulfide bonds between mercapto groups in the polypeptide. The reducing agent may, for example, include at least one selected from the group consisting of thiol, dithiol, sodium carbonate, sodium sulfite, sodium hyposulfite, sodium sulfate, and sodium dithionite. The reducing agent may include at least one selected from the group consisting of dithiol, sodium carbonate, and sodium sulfite, and may be dithiol or sodium sulfite. The reducing agent is preferably a compound having a mercapto group.

[0146] The compound having a mercapto group is preferably a compound represented by the following general formula (Y). Such a compound forms a chemically stable six-membered ring structure in its oxidized form after the reduction reaction, suppressing the reaction between the reducing agent and the Michael addition acceptor in the reaction system. Furthermore, by forming a cyclic structure between the reducing agent and the mercapto group of the polypeptide, the formation of disulfide bonds between polypeptides is suppressed, making the reaction between the mercapto group of the polypeptide and the Michael addition acceptor more significant, thereby enabling the production of a target polymer compound in accordance with the reaction design more efficiently. Examples of dithiols include dithiothreitol and 1,4-butanedithiol. The compound (dithiol) represented by general formula (Y) is specifically dithiothreitol or 1,4-butanedithiol.

[0147]

[0148] Other compounds having a mercapto group include, for example, 3-mercaptopropionic acid, 3-mercapto-1,2-propanediol, and pentaerythritol tetra(3-mercaptopropionate). In addition to the above compounds, the reducing agent may also be, for example, tris(2-carboxyethyl)phosphine (TCEP).

[0149] The lower limit of the amount of the reducing agent may be, for example, 0.5 equivalents or more, 0.8 equivalents or more, or 1.0 equivalents or more relative to the mercapto groups of compound C. By setting the lower limit of the amount of the reducing agent within the above range, the formation of disulfide bonds due to the reaction between the mercapto groups of compound C can be more sufficiently inhibited. This can further improve the production efficiency of the target synthetic polymer compound. The upper limit of the amount of the reducing agent may be, for example, 2.4 equivalents or less, 2.0 equivalents or less, 1.6 equivalents or less, 1.2 equivalents or less, or 1.1 equivalents or less relative to the mercapto groups of compound C. By setting the upper limit of the amount of the reducing agent within the above range, the reaction between compound D and the reducing agent and the generation of by-products can be further suppressed while the reaction proceeds.

[0150] <<Polymerization Inhibitor>> Here, during the heating reaction, it is also preferable to further contain a polymerization inhibitor in addition to compound C and compound D. The polymerization inhibitor is a compound that inhibits self-polymerization of compound D. Examples of the polymerization inhibitor include hydroquinone, methoquinone, 4-tert-butylpyrocatechol, tert-butylhydroquinone, 1,4-benzoquinone, dibutylhydroxytoluene, methoquinol, phenothiazine, and 1,1-diphenyl-2-picrylhydrazyl.

[0151] The content of the polymerization inhibitor may be, for example, 0.01 parts by mass or more, 0.05 parts by mass or more, 0.1 parts by mass or more, or 0.2 parts by mass or more, relative to 100 parts by mass of compound D. By setting the content of the polymerization inhibitor within the above range, for example, the initiation of radical polymerization of the structure represented by formula (M-2) is suppressed, and it may be possible to make the reaction between the structure represented by formula (M-2) and the mercapto group of compound C more dominant. The content of the polymerization inhibitor may be, for example, 25 parts by mass or less, 10 parts by mass or less, 5 parts by mass or less, or 1 part by mass or less, relative to 100 parts by mass of compound D. By setting the content of the polymerization inhibitor within the above range, it is possible to further suppress the polymerization inhibitor from inhibiting the reaction in the system.

[0152] When a compound having a structure represented by the above formula (M-1) is used as compound D, it is preferable to add a reducing agent during the heating reaction, and it is preferable to add a reducing agent and a base during the heating reaction. When a compound having a structure represented by the above formula (M-2) is used as compound D, it is preferable to add a polymerization inhibitor and a reducing agent during the heating reaction, and it is preferable to add a polymerization inhibitor, a reducing agent, and a base during the heating reaction.

[0153] <<Reaction Conditions>> In the above production method, the reaction temperature in the heating reaction may be, for example, 50°C or higher, 53°C or higher, 55°C or higher, 57°C or higher, or 60°C or higher. When the lower limit of the reaction temperature is within the above range, the reaction between compound C and compound D can be further promoted. In the above production method, the upper limit of the reaction temperature for the reaction between compound C and compound D may be, for example, 90°C or lower, 85°C or lower, 80°C or lower, 75°C or lower, or 70°C or lower. When the upper limit of the reaction temperature is within the above range, the formation of bonds between mercapto groups in the polypeptide as a side reaction can be further suppressed, allowing the desired polymer compound to be efficiently synthesized. The reaction temperature for the reaction between compound C and compound D may be adjusted within the above range, and may be, for example, 50 to 90°C, 53 to 80°C, 55 to 75°C, or 55 to 70°C.

[0154] The timing of heating is not limited to after mixing of compounds C and D, and further components such as a base, a reducing agent, and a polymerization inhibitor that are added as needed. For example, these components may be added to a preheated organic solvent (e.g., dimethyl sulfoxide); necessary components out of the base, reducing agent, and polymerization inhibitor may be added to dimethyl sulfoxide, heating may be initiated, and after a predetermined temperature has been reached, compounds C and D may be added and reacted; or one of compounds C and D and necessary components out of the base, reducing agent, and polymerization inhibitor may be added, heating may be initiated, and after a predetermined temperature has been reached, the remaining one of compounds C and D may be added and reacted.

[0155] According to such a method, the block copolymer is obtained in the form of a solution dissolved in an organic solvent. The block copolymer is recovered from this solution by known methods such as drying, reprecipitation, dialysis, etc., and then pulverized as necessary to obtain a powder of a polymer compound containing a polypeptide structure.

[0156] Alternatively, the block copolymer can be obtained by, for example, the method described in WO 2023 / 013638.

[0157] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

[0158] Example 1: Synthesis and Powdering of BCP Synthesis of BCP: 381.3 g of dimethyl sulfoxide (DMSO) was weighed into a three-neck flask, and 573 mg of dithiothreitol (DTT) was added as a reducing agent and stirred to dissolve. Then, 40.0 g of artificial fibroin (polypeptide, 10 kDa) having the amino acid sequence shown in SEQ ID NO: 9 (PRT3177) was added, and the mixture was heated and stirred at 70°C for 30 minutes to dissolve. 40.0 g of polyethylene glycol bismaleate was then added, and the mixture was heated and stirred at 85°C for 60 minutes to obtain a DMSO solution containing a polymer compound in which a polypeptide moiety and a polyethylene glycol moiety were linked. The DMSO solution of the polymer compound prepared as described above was reprecipitated in acetone and centrifuged five times, after which the supernatant was removed by decantation to separate the precipitate. The resulting precipitate was spread on a tray and dried in a fume hood for several hours, followed by drying in a vacuum oven at 40°C for 15 hours to obtain a powder of the polymer compound. The obtained polymer compound powder was placed in a mortar together with liquid nitrogen and finely pulverized with a pestle. The pulverized powder was sieved (mesh opening: 250 μm) to obtain a powder with a particle size of 250 μm or less (hereinafter referred to as "powder A").

[0159] <Method for producing synthetic leather> [Example 1] 3.0 g of powder A prepared as described above was spread evenly on a cotton knitted fabric (base fabric layer, thickness 0.6 mm, fiber diameter approximately 20 μm) cut to a size of 15 cm length x 8 cm width, and the fabric was sandwiched between release papers from above and below and passed through a hot roll press under conditions of a roll temperature of 100°C, a roll gap of 0.3 mm, a load of 5 kN, and a feed rate of 0.1 m / min. The polymer compound powder was resinified into a film-like resin on the knitted fabric and pressed, yielding a soft synthetic leather 0.66 mm thick.

[0160] <Evaluation of Physical Properties> The synthetic leather obtained in Example 1 was punched out into dumbbell shapes 105 mm long and 5 mm wide, and aged for 24 hours or more in an environment at a temperature of 20°C and a humidity (relative humidity) of 65%. A tensile test was then carried out using a universal testing machine at a tensile speed of 10 mm / min, and the results are shown in Table 2. All values ​​in the table are arithmetic averages for n=4.

[0161] [Rule 26 amendment 04.04.2025]

[0162] The cross section of the synthetic leather obtained in Example 1 was also observed with a scanning electron microscope (SEM). The SEM image is shown in Figure 4. From Figure 4, it was confirmed that a 250 μm-thick skin layer 110 was formed on the fabric layer 100 from a resin film formed from Powder A, and that a synthetic leather was produced comprising the fabric layer 100 and the skin layer 110 integrally formed on the fabric layer.

[0163] As described above, synthetic leather exhibiting excellent physical properties could be produced without using an organic solvent when applying a polymer compound containing a polypeptide structure to the base fabric layer.

[0164] Comparative Example 1: In place of the powder A prepared as described above, artificial fibroin (polypeptide, 10 kDa) powder having the amino acid sequence (PRT3177) was used. The powder was applied to a cotton knitted fabric and passed through a hot roll press in the same manner as in Example 1. However, the powder did not resinify, and synthetic leather could not be produced.

[0165] Example 2: 0.7 g of the powder A prepared as described above was spread evenly onto a piece of release paper cut to a length of 15 cm and a width of 8 cm. Another piece of release paper was placed on top of it, and the resulting mixture was passed through a hot roll press under conditions of a roll temperature of 100°C, a roll gap of 0.3 mm, a load of 5 kN, and a feed rate of 0.1 m / min. The polymer compound powder was resinified into a film on the release paper. The release paper was peeled off, and a cotton knit fabric cut to a length of 9 cm and a width of 7 cm was placed on top of the polymer compound film. Another piece of release paper was then placed on top of it, and the resulting mixture was passed through a hot roll press under conditions of a roll temperature of 100°C, a roll gap of 0.3 mm, a load of 5 kN, and a feed rate of 0.1 m / min. The polymer compound film was pressed onto the cotton knit fabric, yielding a soft synthetic leather with a thickness of 0.37 mm.

[0166] [Example 3] Synthetic leather was produced using 1.0 g of the powder A prepared as described above in the same manner as in Example 2, except that the roll gap of the hot roll press was set to 0.35 mm. A soft synthetic leather with a thickness of 0.41 mm was obtained.

[0167] [Example 4] Synthetic leather was produced using 1.0 g of the powder A prepared as described above in the same manner as in Example 2, except that the roll gap of the hot roll press was set to 0.40 mm. A soft synthetic leather with a thickness of 0.48 mm was obtained.

[0168] Figure 5 is a photograph of the synthetic leathers obtained in Examples 2 to 4. Examples 2 to 4 show that even when a resin film, rather than a powder, is placed on a fabric layer and then heated and pressurized, a skin layer formed from a resin sheet can be laminated integrally with the fabric layer.

[0169] According to the present disclosure, a method for producing synthetic leather that reduces the burden on the environment is provided.

[0170] REFERENCE SIGNS LIST 1 Skin layer 2 Base fabric layer 4 Resin film A 6 Powder of polymer compound containing polypeptide structure 10 Synthetic leather 100 Base fabric layer 110 Skin layer

Claims

1. A method for producing synthetic leather comprising a base fabric layer and a skin layer integrally laminated on the base fabric layer, the method comprising: preparing a base fabric layer on which a resin film A formed by heating and pressurizing a polymer compound containing a polypeptide structure, or a powder of a polymer compound containing a polypeptide structure, is placed; and pressing the resin film A or the powder against the base fabric layer while heating it, thereby adhering the resin film A or the resin film B formed from the powder by pressing it to the base fabric layer, thereby forming the skin layer from the resin film A or the resin film B, and laminating the skin layer integrally with the base fabric layer, wherein the polymer compound containing a polypeptide structure comprises a block copolymer having a first segment containing a polypeptide skeleton and one or more second segments bonded to the first segment, and the second segment comprises a molecular group having a plasticizing function for the polypeptide skeleton.

2. The method of claim 1, wherein the polypeptide backbone is a recombinant polypeptide backbone.

3. The method of claim 1 or 2, wherein the polypeptide backbone is a hydrophobic polypeptide backbone.

4. The method according to any one of claims 1 to 3, wherein the molecular group having a plasticizing function for the polypeptide backbone is a polyether, polyester, or polycarbonate.

5. The method according to any one of claims 1 to 4, wherein the block copolymer is obtained by mechanochemically treating a mixture containing a compound having the polypeptide backbone and a compound having a molecular group capable of plasticizing the polypeptide backbone.

6. The method according to any one of claims 1 to 5, wherein the fabric layer and the resin film A or the powder are heated and pressed using a hot roll press.

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