Manufacturing method of fibroin molding body

Abstract

To provide manufacturing method of molded parts that improves the flowability of fibroin during molding while maintaining appropriate crystallinity.SOLUTION: This invention relates to manufacturing method for producing a compact with improved moldability of fibroin, the process consists of placing a powder containing fibroin and a compound having two or more functional groups of guanidyl or amino groups with three to six carbon chains between the functional groups in a mold, and compressing the powder in the mold with a piston.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] [Technical Field]

[0002] The present invention relates to a method for manufacturing a molded body.

Background Art

[0003] [Background Art]

[0004] Efforts have been made to process various products using hydrophilic fibroin. Since fibroin has high hydrophilicity and strong intermolecular bonding strength due to hydrogen bonding, intermolecular bonding may occur when heat or pressure is applied during the molding process, and the fluidity of fibroin may decrease, and therefore relatively high pressure is required.

[0005] US2020 / 0102424 provides a molding method for molding fibroin at a relatively low pressure by adding an additive such as urea to fibroin to improve fluidity.

[0006] However, when a large amount of the additive that will remain in the fibroin molded body is used, the crystallinity of the molded part decreases and the flexural modulus decreases. On the other hand, when the amount of the additive is small, the effect of improving fluidity is insufficient, so it is difficult to achieve both improvement in fluidity and suppression of a decrease in flexural modulus.

[0007] Therefore, when obtaining a molded part containing fibroin, it is required to improve the fluidity of fibroin during molding while making the crystallinity of the molded part (article) appropriate.

Summary of the Invention

[0008] [Summary of the Invention]

[0009] The present invention relates to improving the fluidity of fibroin during molding while making the crystallinity of the molded part appropriate.

[0010] Therefore, in one aspect, the present disclosure provides a method for manufacturing a molded part, including putting a powder containing fibroin and a compound having two or more functional groups of guanidyl groups or amino groups and having a carbon chain with 3 to 6 carbon atoms between the functional groups into a mold, and compressing the powder in the mold with a piston.

[0011] These and other embodiments, objects, features, and advantages of the present disclosure will become apparent upon reading the following detailed description of the exemplary embodiments of the present disclosure when taken in conjunction with the accompanying drawings and the claims provided.

Brief Description of the Drawings

[0012] [Brief Description of the Drawings]

[0013] The accompanying drawings incorporated herein and forming a part of the specification illustrate various embodiments, objects, features, and advantages of the present disclosure.

[0014]

Figure 1

[0015]

Figure 2

[0016]

Figure 3

[0017] Throughout the figures, unless otherwise specified, the same reference numerals and characters are used to represent features, elements, components, or parts of the illustrated embodiments. Further, here, the disclosure of the subject matter is described in detail with reference to the figures, which is done in relation to the exemplary embodiments. It is intended that changes and modifications can be made to the described exemplary embodiments without departing from the true scope and spirit of the subject matter disclosure defined by the appended claims.

Embodiments for Carrying Out the Invention

[0018] [Mode for Carrying Out the Invention]

[0019] The present disclosure has several embodiments and relies on patents, patent applications, and other references known in the art. Accordingly, when a patent, patent application, or other reference is cited or repeated in this specification, it should be understood that it is incorporated by reference in its entirety for all purposes as if the described proposition were set forth in full.

[0020] [Power Source for Molding]

[0021] An exemplary process for obtaining the powder for molding is described in FIG. 2. In step S11, the aqueous fibroin solution is prepared as otherwise described in the present disclosure. In step S12, an additive is added to the aqueous fibroin solution described herein. In step S13, water is removed from the aqueous solution of fibroin and the additive described herein. Subsequently, the dry sheet of fibroin obtained from step S13 can be pulverized into a powder.

[0022] The powder for molding of the present disclosure contains a compound having two or more functional groups of a guanyl group or an amino group and having a carbon chain between the functional groups consisting of 3 to 6 carbons (hereinafter also referred to as an additive) and fibroin.

[0023] The mechanism by which the additive in the present disclosure improves the fluidity of fibroin with a small amount can be considered as follows. The guanidyl group and amino group of the additive of the present disclosure easily interact with the polypeptide sequence forming fibroin. Therefore, these groups naturally associate at the positions where fibroin molecules form hydrogen bonds, preventing fibroin molecules from forming hydrogen bonds with each other. As a result, the fluidity of fibroin is improved. In addition, the additive of the present disclosure has two or more guanidyl groups or amino groups, and the carbon chain between the functional groups consists of three or more carbons, so the fluidity of fibroin can be improved by the steric hindrance effect. Moreover, since the number of carbon chains between the functional groups is 6 or less, the effect of disturbing the hydrogen bonds between fibroin molecules does not become too large, and it is possible to suppress a significant decrease in the flexural modulus of the molded part.

[0024] Arginine or polylysine can be used as the additive according to the present disclosure. This is because they are industrially available and because of their biocompatibility often required for fibroin molded parts. These substances can be used alone or in any combination as the additive.

[0025] The amount of the additive for improving the fluidity of fibroin can be 1% by weight or more and 10% by weight or less based on the molding powder. If it is less than 1% by weight, it is difficult to ensure the fluidity of fibroin because the amount of the additive is small. Also, when an amount exceeding 10% by weight is added, the decrease in the flexural modulus of the molded part becomes large.

[0026] Hereinafter, specific examples of methods for verifying the additive content for improving the fluidity of fibroin are given, but these are not limited to those described and can be verified by known methods.

[0027] For example, as a method for verifying the additive content, a method using a colorimetric quantification kit can be considered. When the molding powder is sufficiently dissolved in an aqueous LiBr solution prepared in advance at a concentration of 1 M, the concentration in the aqueous solution is detected using a colorimetric quantification kit. The actual additive concentration can be determined from the detection sensitivity of the sample by examining in advance the detection intensity with respect to the additive concentration and using it as a calibration curve in advance. Based on the additive concentration used when preparing the aqueous solution and the amount of the aqueous LiBr solution, the weight of the dissolved additive that actually improves the fluidity can be confirmed. Therefore, the weight of the molding powder to be used can be divided to determine the weight concentration of the additive.

[0028] Similarly, there is also a method of calculating the additive concentration in the solution based on the detection sensitivity of the sample by preliminarily confirming the detection sensitivity of a gas chromatograph or a liquid chromatograph with respect to the additive concentration dissolved in the aqueous LiBr solution and obtaining a calibration curve. In the subsequent steps, the weight concentration of the additive can be determined in the same manner as when using a colorimetric quantification kit.

[0029] There is another method using ultrafiltration. After sufficiently dissolving the molding powder in a preliminarily concentrated aqueous LiBr solution, fibroin is removed from the solution, and ultrafiltration is performed to obtain a filtrate composed of an additive (for example, arginine), LiBr, and water. Since the dry weight of the filtrate - LiBr is the weight of arginine, it is possible to determine the total weight of arginine in the aqueous solution. The weight concentration can also be the total weight of arginine with respect to the added weight of the molding powder. When using this method, the molecular weight cut-off value of the ultrafiltration membrane can be made sufficiently smaller than the molecular weight of fibroin and sufficiently larger than the molecular weight of the additive.

[0030] Any fibroin can be used without particular limitation, but silk fibroin purified from silkworm cocoons, hornet silk produced by wasp larvae, and spider silk produced from spider webs may be used. Since these biopolymeric materials composed of these amino acids have strong hydrophilicity, the effects of the present disclosure can be particularly exhibited. Among these, one type or a mixture of multiple types may be used.

[0031] The molecular weight of fibroin can be 30 kDa or more and 300 kDa or less. If the molecular weight of fibroin is less than 30 kDa, the mechanical strength of the molded part may decrease, which is not preferable. Also, if the molecular weight of fibroin is greater than 300 kDa, the viscosity of the material itself becomes too high, so the fluidizing effect by the additive becomes small, which is not desirable.

[0032] [Method for producing powder for molding]

[0033] In the present disclosure, the powder for molding includes a step of preparing an aqueous fibroin solution, a step of mixing an additive into the aqueous fibroin solution, and a step of removing moisture from the mixed aqueous solution. Also, after removing the moisture, the powder for molding may include a step of processing it as the powder for molding. Figure 3 and the following sections explain each process. In an exemplary method for molding the powder as provided in Figure 3, in step S21, the powder prepared as described in this specification is placed in a mold. In step S22, this powder is compressed with a piston during heating.

[0034] [Method for producing aqueous fibroin solution]

[0035] For example, an aqueous fibroin solution can be prepared using the method for producing an aqueous solution of silkworm silk described in International Publication No. 2006 / 101223 or the method for producing an aqueous solution of spider silk described in U.S. Patent Application Publication No. 5245012. By using these, an aqueous solution in which fibroin is uniformly dissolved can be obtained.

[0036] When the viscosity of the aqueous solution is high, it becomes difficult to uniformly mix the additives to be mixed in the next process. Thus, in one aspect, the concentration of fibroin in the aqueous solution before addition can be 1 part by weight or more and 30 parts by weight or less. The weight concentration of fibroin can be measured by TGA. Specifically, 20 to 100 mg of a well-stirred aqueous fibroin solution is heated from 30 °C to 120 °C at a heating rate of 10 °C / min, then held at 120 °C for 30 minutes to evaporate the water. Subsequently, the weight concentration of fibroin can be measured by taking the ratio of the weight after evaporation of water to the weight at the start of measurement as the weight concentration of fibroin.

[0037] [Process of mixing additives]

[0038] Next, additives are mixed into the aqueous fibroin solution prepared by the above method. In this process, both fibroin and the additives are dissolved in water. This is because in the next process, a molding powder in which fibroin and the additives are uniformly dispersed is obtained by removing water from the aqueous solution obtained in this process.

[0039] [Dehydration treatment]

[0040] In this process, a dried body of the mixture is produced by removing water from the aqueous solution prepared in the previous process. As the method for removing water, methods such as freeze-drying, spray-drying, vacuum-drying, vibration-drying, drum-drying, air-drying, etc. can be used, and these can be combined. Among these, freeze-drying, which has little thermal impact on the mixture dissolved in the aqueous solution, or spray-drying, in which the aqueous solution is heated for a short time, may be used.

[0041] When using the freeze-drying method, the freezing temperature is not particularly limited as long as the aqueous solution freezes. However, since the freezing point of the aqueous solution in which the solute (fibroin and additive) is dissolved is lower than the freezing point of water, the freezing temperature can be -10°C or lower, or -20°C or lower. On the other hand, since the lower the drying temperature, the more time it takes for dehydration, it can be dried at -20°C or higher, or -15°C or higher. In a sufficiently frozen sample, there is no problem as long as the pressure is 600 Pa or lower, which is the triple point pressure of water. However, when a part of the sample is liquefied due to temperature unevenness, since the aqueous solution foams, a pressure of 100 Pa or lower can be used, and a pressure of 50 Pa or lower can also be used. In one aspect, the vacuum can be released when the temperature of the dried material after removing moisture reaches 10°C or higher. If the temperature of the dried material after removing moisture is lower than this, condensation may occur inside the sample, and the dried material may absorb moisture. In this case, fibroin may gel, which is not desirable.

[0042] When using spray drying, the concentration of fibroin in the aqueous solution may be adjusted in advance to facilitate spraying.

[0043] [Processing method as molding powder]

[0044] If it is in powder form, the fibroin and additive-containing composition (fibroin composition) with moisture removed as it is can be used. Also, when the obtained fibroin composition is not in powder form (in bulk form), for example, a molding powder can be obtained by pulverizing the dried body after freeze-drying using a jet mill, hammer mill, ball mill, pin mill, etc. Further, by classifying the pulverized powder, a molding powder with a certain uniform particle size can be obtained.

[0045] [Molding method of molding powder]

[0046] The molding of the powder according to the present disclosure can be performed at a temperature lower than the decomposition start temperature of fibroin. Also, in order to promote the integration of the molded parts, the molding time can be appropriately selected so that the crystallization rate of fibroin in the molded body is 50% or more.

[0047] Using a general method for forming, it is possible to use any forming method without detailed description, but it is possible to start from injection molding, extrusion molding, and compression molding.

[0048] This forming pressure can be 300 MPa or less, or 100 MPa or less, which is the pressure used in conventional thermoplastic resin molding. A pressure of 300 MPa or more is not desirable because the equipment load increases in proportion to the size of the formed part and the equipment investment cost becomes high. Also, in order to perform shape transfer, molding can be carried out at 10 MPa or more.

[0049] Before the forming process to obtain the final formed shape, a process of compressing the molding powder without heating to obtain a powder compact may be provided. By providing this process, even complex shapes may become easier to mold.

[0050] [Method for measuring the crystallization rate of a formed part]

[0051] Regarding the crystallization rate of the formed part, refer to the method described in Nature Materials 19, 102 - 108 (2020) and determine it in the following explanation. Specifically, first, in the range of 1580 cm-1 to 1720 cm-1, measure the Fourier transform infrared (FTIR) spectrum of the surface of the formed part every 1 cm-1. Calculate a linear function passing through the values at 1580 cm-1 and 1720 cm-1 of the obtained spectrum, set it as the baseline, and subtract it from the measured values. The obtained spectrum is taken as the sum of four spectra obtained from a random coil, beta sheet I, beta sheet II, and beta turn, and this is called the effective spectrum.

[0052] On the one hand, the spectrum obtained from the random coil can be approximated by a variable having a peak center between 1645 cm-1 and 1655 cm-1, and the spectra obtained from beta-sheet I, beta-sheet II, and beta-turn can be approximated by the sum of Gaussian functions having peak centers with fixed values of 1620, 1698, and 1685 cm-1, respectively. Among the four Gaussian functions, the sum of the peak intensity and deviation of the Gaussian function is obtained as a variable, and this is used as a composite spectrum having nine variables.

[0053] In the range of 1580 cm-1 to 1720 cm-1, the absolute value of the difference between the effective spectrum and the composite spectrum is obtained every 1 cm-1, and the sum is obtained, which is defined as the spectrum error. The spectrum error with respect to the integral value of the effective spectrum is defined as the error rate, and the nine variables of the composite spectrum are fitted so that the error rate becomes small. When the error rate after fitting is 3% or less, it is assumed that the spectrum converges, and the four spectra constituting the composite spectrum are regarded as the spectra of each actual component. Finally, as the crystallization rate in the present disclosure, the sum of the integral values of the three spectra derived from beta-sheet I, beta-sheet II, and beta-turn with respect to the integral value of the effective spectrum in the range of 1580 cm-1 to 1720 cm-1 is calculated. Since the crystallization rate (total of beta-sheet I, beta-sheet II, and beta-turn) in the case of silk fibroin is less than 20% in the dry state before heat molding and is considered to be 50% or more after heat molding, it can be determined that the molded part has strength when the crystallization rate in the present disclosure exceeds 50%.

[0054] The fitting can be performed using software attached to the infrared absorption spectrum measuring device, graph analysis software, a solver add-in in Microsoft Excel software, etc.

[0055] [Shape Transferability Evaluation Method]

[0056] Based on the Ra (arithmetic mean roughness) of the surface of the molded part, the shape transferability obtained when molding by pressing resin against a flat surface with a surface roughness Ra of 4 μm can be evaluated. When the Ra of the surface of the molded part is greater than 3 μm, it can be said that the shape transferability is high and the fluidity of fibroin is also high. If Ra is 3 μm or less, it can be determined that the transfer rate is low. Note that Ra can be measured by a contact measurement method using a tactile needle or a non-contact measurement method using a laser or light.

[0057] The present disclosure will be described using the following examples.

[0058] [Example 1]

[0059] [Step 1: Preparation of fibroin aqueous solution]

[0060] In this step, an aqueous fibroin solution obtained from silk fibroin was prepared.

[0061] First, the silkworm cocoons were washed with water, then boiled in a 0.02 mol / L aqueous sodium carbonate solution for 30 minutes to degum. The degummed silk was poured into a 9.3 mol / L aqueous LiBr solution, stirred at 60 °C for 4 hours to dissolve, and dialysis was performed using a cellulose tube 30 / 32 manufactured by Sekisui Chemical Co., Ltd. (fractionation molecular weight 12,000 - 14,000). After further dilution with pure water, it was confirmed by visual inspection that the aqueous solution was uniform without precipitation. This aqueous solution was used as the fibroin aqueous solution, and thermal analysis of 73.157 mg of the aqueous solution was performed using TGA (TGA 8000 manufactured by PerkinElmer). After heating from 30 °C to 120 °C at a heating rate of 10 °C / min, continuous heating at 120 °C for 30 minutes, it became 4.511 mg. From this, it was found that the weight concentration of fibroin was 6.17%. Then, it was further heated to 400 °C at a heating rate of 1 °C / min, and the decomposition start temperature was determined from the weight loss curve. The decomposition start temperature was 185 °C. Also, when the molecular weight of this fibroin was measured by SDS-PAGE, it was 155 kDa. For the detailed procedure of SDS-PAGE, the procedure disclosed by L S Wray et al., "J Biomed Mater Res B Appl Biomater", October 2011, 99(1), pages 89 - 101 was used.

[0062] [Step 2: Mixing Additive]

[0063] In this step, arginine was selected as the additive, and a mixture of the fibroin aqueous solution and arginine was prepared. Specifically, mixing and stirring were performed so that the amount of arginine was 1 part by weight with respect to the fibroin whose weight concentration was measured in the previous step. One hour after mixing, the liquid mixture was visually checked, and no precipitation was confirmed and it was homogeneous.

[0064] [Step 3: Dehydration]

[0065] In this step, water was removed from the aqueous solution.

[0066] After spreading the solution mixed with arginine in Step 2 on separate trays to a thickness of 5 mm, the trays were placed on the shelves of a freeze dryer (manufactured by Tokyo Rika Kikai Co., Ltd., model number FD-550P) and cooled to -30°C. After 3 hours, after visually confirming freezing, decompression was started at -6°C and 30 Pa, and dehydration was started. After 24 hours, the sample temperature was raised to 15°C, then the decompression was released, and the sheet-like dried body was taken out. After one week of aging, the two types of sheets remained under the same visual conditions, and no gelation or the like occurred.

[0067] [Step 4: Obtaining powder]

[0068] The powder for molding was obtained by pulverizing the fibroin composition obtained in Step 3 with a milling machine (manufactured by Iwaki Sangyo Co., Ltd., Crash Mill Ser. IFM-C20G) for 30 seconds.

[0069] [Step 5: Molding]

[0070] The fibroin powder for molding containing the additive obtained in Step 4 was used to obtain a molded part for evaluating the shape transferability using a mold with a rough surface on one hand, and separately molded using a mold of a size for evaluating the flexural modulus on the other hand to obtain a molded part for evaluating the flexural modulus.

[0071] First, in order to obtain a sample for evaluating the shape transferability, a 1 cm2 lower piston 1 with a rough surface 2 was prepared. When the surface roughness was measured non-contact using a 10×LT objective lens set on OPTELICS HYBRID+ manufactured by Lasertec Corporation, Ra was 4.0 μm. This lower piston 1 was used as the lower mold, and a piston guide 4 with a 1 cm2 prismatic through-hole as shown in FIG. 1 and a 1 cm2 upper piston 3 without surface roughening were assembled as the upper mold. Then, the powder for molding a compressed body 5 composed of an additive and fibroin was attached to the mold.

[0072] The mold was set in a mold compression molding machine (VN02 - 2020C manufactured by Mikado Technos Co., Ltd.) with the press plate preheated to 120°C in advance, and heated and compressed to a molding pressure of 100 MPa. After 5 minutes, the load was released and air-cooled. When it was cooled to 40°C, the mold was disassembled, the molded parts were taken out, and the shape transferability was evaluated.

[0073] To obtain a sample for evaluating the flexural modulus, 4.7 g of powder was filled into a mold of 85 mm×10 mm, set in a mold compression molding machine preheated to 140°C, and heated and compressed to a molding pressure of 100 MPa. After 10 minutes, the load was released and air-cooled. When it was cooled to 40°C, the mold was disassembled, the molded parts were taken out, and the flexural modulus was evaluated.

[0074] [Shape Transferability Evaluation]

[0075] Table 1 shows the results of measuring the surface roughness of the molded parts for shape transferability evaluation. Also, when the surface roughness was 3.5 μm or more, it was designated as A; when it was 3.0 or more and less than 3.5, it was designated as B; and when it was less than 3.0, it was designated as C, and these were described in Table 1.

Table 1

[0076] [Flexural Modulus Evaluation]

[0077] The flexural modulus of the molded parts for evaluating the flexural modulus was measured using a universal material tester (5582 manufactured by Instron Japan Co., Ltd.) at a pressing speed of 2 mm / min. The results of the flexural modulus are shown in Table 1. Also, when the flexural modulus was 90 MPa or more, it was designated as A; when it was 20 MPa or more and less than 90 MPa, it was designated as B; and when it was less than 20 MPa, it was designated as C, and these were described in Table 1.

[0078] [Examples 2 - 3]

[0079] In step 2 of Example 1, the same process as in Example 1 was carried out, except that an aqueous solution was prepared such that the amount of arginine added to fibroin was the additive amount listed in Table 1.

[0080] The results of the surface roughness and flexural modulus of the obtained molded parts are shown in Table 1.

[0081] [Examples 4 to 6]

[0082] In Step 2 of Example 1, a process similar to that of Example 1 was carried out, except that an aqueous solution was prepared using polylysine as an additive for the fibroin listed in Table 1.

[0083] The results of the surface roughness and flexural modulus of the obtained molded parts are shown in Table 1.

[0084] [Comparative Examples 1 to 3]

[0085] In Step 2 of Example 1, a process similar to that of Example 1 was carried out, except that an aqueous solution was prepared using urea as an additive for the fibroin listed in Table 1.

[0086] The results of the surface roughness and flexural modulus of the obtained molded parts are shown in Table 1.

[0087] [Example 7]

[0088] In this example, an aqueous protein solution composed of hornet silk was prepared.

[0089] In Step 1, first, the cocoons collected from the honeybee nest were cut into pieces about 5 mm in size, and impurities were removed to the extent that they could be visually confirmed. The cocoon pieces were placed in a 9 mol / L aqueous LiBr solution and stirred at 40 °C for 1 hour to dissolve the cocoon pieces. The stirred aqueous LiBr solution was centrifuged to separate and remove the impurities, which were insoluble components.

[0090] Next, the aqueous LiBr solution from which impurities had been removed was placed in a 30 / 32 cellulose tube (fractionation molecular weight 12,000 to 14,000) manufactured by Sekisui Chemical Co., Ltd. and dialyzed in distilled water at room temperature for 4 days to remove LiBr. When the obtained protein concentration and fractionation molecular weight were confirmed, they were 6.51 parts by weight and 45 kDa, respectively.

[0091] From Process 2 onward, the treatment was carried out in the same manner as in Example 1, and the results of the surface roughness and flexural modulus of the obtained molded parts are shown in Table 1.

[0092] [Evaluation of Crystallization Rate]

[0093] To calculate the crystallization rate of the molded body from the infrared absorption spectrum, the infrared absorption spectrum of the surface of the molded part was measured by the ATR method using a Frontier FT-IR / NIR spectrometer manufactured by PerkinElmer. When the crystallization rate of the spectrum was measured by the crystallization rate measurement method, it was confirmed that sufficient crystallization had progressed since all the samples of Examples 1 to 7 exceeded 50%.

[0094] [Definitions]

[0095] In this description, specific details are set forth in order to provide a thorough understanding of the disclosed examples. In other instances, well-known methods, procedures, components, and circuits are not described in detail so as not to unnecessarily extend the present disclosure.

[0096] When an element or portion is referred to in this specification as being "on," "to," "connected to," or "coupled to" another element or portion, it is to be understood that it may be directly on, directly to, directly connected to, or directly coupled to the other element or portion, or intervening elements or portions may be present. In contrast, when an element is referred to as being "directly on," "directly connected to," or "directly coupled to" another element or component, no intervening elements or components are present. As used, the term "and / or" includes any and all combinations of one or more of the associated listed items, as so provided.

[0097] Spatially relative terms such as "lower", "upper", "above", "proximal", and "distal" may be used herein to facilitate descriptions of the relationship of one element or feature to another element or feature as shown in the various figures. However, it should be understood that spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation shown in the figures. For example, if the device in the figures is turned over, an element described as "lower" or "beneath" another element or feature will be oriented "above" the other element or feature. Thus, relative spatial terms such as "beneath" can encompass both an orientation above and below. The device may be in other orientations (90 degree rotations or other orientations), and the spatially relative descriptors used herein should be interpreted accordingly. Similarly, the relative spatial terms "proximal" and "distal" may also be interchangeable where applicable.

[0098] As used herein, the term "about" means, for example, within 10%, within 5%, or less. In some embodiments, the term "about" may mean within the measurement error.

[0099] Terms such as first, second, third, etc. may be used herein to describe various elements, components, regions, parts, and / or sections. It should be understood that these elements, components, regions, parts, and / or sections are not to be limited by these terms. These terms are only used to distinguish one element, component, region, part, or section from another region, part, or section. Thus, a first element, component, region, part, or section discussed below could be termed a second element, component, region, part, or section without departing from the teachings of the present specification.

[0100] The terms used in this specification are for the purpose of describing particular embodiments only and are not intended to be limiting. The use of the terms "a," "an," and "the," and similar referents in the context of describing the present disclosure (especially in the context of the following claims), unless otherwise indicated herein or clearly contradicted by the context, should be construed to cover both the singular and the plural forms. The terms "comprising," "having," "includes," "including," and "containing" are to be construed as open-ended terms (i.e., meaning "including, but not limited to") unless otherwise specified. Specifically, when these terms are used in this specification, they specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof that are not explicitly stated. The recitation of numerical ranges herein is merely intended to serve as a shorthand for referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. For example, if the range 10-15 is disclosed, then 11, 12, 13, and 14 are also disclosed. All methods described herein can be performed in any suitable order unless otherwise indicated herein or clearly contradicted by the context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein is merely intended to better illuminate the disclosure and does not impose a limitation on the scope of the disclosure unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the disclosure.

[0101] The methods and compositions of the present disclosure can be incorporated in various embodiments, and it will be understood that only a few of these can be disclosed herein. Variations of these embodiments may become apparent to those skilled in the art upon reading the above description. It is expected that those skilled in the art can appropriately adopt such variations, and the present disclosure is intended to be practiced in ways other than those specifically described herein. Accordingly, the present disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Further, any combination of the above elements in all possible variations thereof is included in the disclosure unless specifically indicated otherwise or clearly contradicted by context.

Claims

1. Putting a powder containing fibroin and a compound having two or more functional groups, which are guanidyl groups or amino groups, and having a carbon chain having 3 to 6 carbon atoms between the functional groups, into a mold; compressing the powder in the die with a piston; A method for producing a molded body, comprising the steps of:

2. The method for producing a molded body according to claim 1 , wherein the compressing is performed while heating the powder.

3. The method for producing a molded body according to claim 2 , wherein the compressing while heating is performed after compressing the powder in the die with the piston without heating the powder.

4. The method for producing a molded article according to claim 1 , wherein the molded article has a fibroin crystallization rate of 50% or more.

5. The method for producing a molded body according to claim 1 , wherein the compressing is performed at a pressure of 30 MPa or more and 300 MPa or less.

6. The method for producing a molded article according to claim 1 , wherein the compound comprises at least one of arginine and polylysine.

7. The method for producing a molded body according to claim 1 , wherein the amount of the compound in the powder is 1% by weight or more and 10% by weight or less with respect to the powder.

8. Obtaining an aqueous solution in which the fibroin is dissolved; mixing the compound with the aqueous solution; removing water as a solvent from the aqueous solution obtained by the mixing; The method for producing a molded body according to claim 1 , wherein the powder is obtained by a method comprising the steps of:

9. The method for producing a molded body according to claim 8, wherein the concentration of the fibroin in the aqueous solution obtained by the above process is 2 parts by weight or more and 30 parts by weight or less relative to the water.

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