Chitosan-derived sponge, chitosan-derived sheet, and method for producing the same

Abstract

To provide a chitosan-derived sponge and a chitosan-derived sheet, which have chitosan that has a cost merit compared with amorphous chitin as a main component, in particular, the chitosan-derived sponge and the chitosan-derived sheet which have a rapid water absorption speed and maintain breakage strength after water absorption as well as a method for manufacturing these.SOLUTION: In a manufacturing process of chitosan-derived sponges and chitosan-derived sheets, mass production is easily possible by optimizing a type of an organic solvent added to a chitosan suspension and improving the heat treatment conditions after freeze-drying. The present invention has been completed by successfully developing chitosan-derived sponges and sheets that have a rapid water absorption speed, do not dissolve or crumble after water absorption, and maintain breaking strength.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a chitosan-derived sponge, a chitosan-derived sheet, and methods for producing them.

Background Art

[0002] (Chitosan) Chitosan is widely used in the fields of cosmetics, medicine, food, etc., and as a natural material, it is preferably used in the same way as collagen materials and the like.

[0003] The use of chitin and chitosan as medical bands has been attempted for more than 20 years, and their organic acid salts have also been published (Patent Document 1). In addition, attempts have been made to make chitosan into a sponge form (Patent Document 2). And attempts have been made to commercialize organic acid salts of chitin or chitin derivatives (Patent Document 3) (Patent Document 4) (Patent Document 5).

[0004] The present inventors have disclosed a novel hemostatic material obtained by improving chitosan itself, adjusting its degree of deacetylation and further making it amorphous (Patent Documents 6) (Patent Document 7), an improved preparation of chitosan sponge (Patent Documents 8) (Patent Document 9), a sponge-like hemostatic material derived from chitin (Patent Document 10), and a sponge-like hemostatic material mainly composed of amorphous partially deacetylated chitin salt (Patent Document 11).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Patent Document 9

Patent Document 10

Patent Document 11

Summary of the Invention

Problems to be Solved by the Invention

[0006] Amorphous chitin has a very complicated amorphization process and is more costly than chitin and chitosan. Therefore, it is an issue to be solved to provide a chitosan-derived sponge and a chitosan-derived sheet mainly composed of chitosan, which have a cost advantage compared to amorphous chitin, particularly a chitosan-derived sponge and a chitosan-derived sheet with a high water absorption rate and maintaining the breaking strength after water absorption, and a method for producing them.

Means for Solving the Problems

[0007] The inventors of the present invention have succeeded in developing a chitosan-derived sponge and a chitosan-derived sheet that can be easily mass-produced, have a high water absorption rate, do not dissolve or decompose into a mess after water absorption, and maintain the breaking strength, by optimizing the type of organic solvent added to the chitosan suspension and improving the heat treatment conditions after freeze-drying in the production process of the chitosan-derived sponge and the chitosan-derived sheet, and completed the present invention.

[0008] That is, the present invention is as follows. 1. A method for producing a sponge mainly composed of chitosan, including the following steps; (1) A step of suspending chitosan with a degree of deacetylation of 70 to 100%, (2) A step of adding 0.7 mol or more of acetic acid per 1 mol of the amino group of the chitosan to the suspension in (1) above. (3) A step of obtaining sherbet frozen ice from the filtrate obtained from the solution in (2) above. (4) A step of performing freeze-drying on the sherbet frozen ice in (3) above to obtain a freeze-dried product, and (5) A step of performing heat treatment on the freeze-dried product in (4) above at 80 to 100 °C for 18 to 48 hours to obtain a heat-treated product. 2. A method for producing a sponge mainly composed of chitosan according to item 1 above, characterized in that the amount of eluted acetic acid is made 9% or less by the heat treatment in (5) above. 3. A sponge mainly composed of chitosan obtained by the production method according to item 1 or 2 above. 4. The sponge according to item 3 above, having the following characteristics. (1) Water absorption amount (g / g): 20 to 120 (2) Breaking strength (N): 5 to 100 (3) Water absorption time (sec): 30 or less 5. A method for producing a sheet mainly composed of chitosan, including the following steps; (1) A step of suspending chitosan having a deacetylation degree of 70 to 100%. (2) A step of adding 0.7 mol or more of acetic acid per 1 mol of the amino group of the chitosan to the suspension in (1) above. (3) A step of obtaining sherbet frozen ice from the filtrate obtained from the solution in (2) above. (4) A step of performing freeze-drying on the sherbet frozen ice in (3) above to obtain a freeze-dried product. (5) A step of performing heat treatment on the freeze-dried product in (4) above at 80 to 100 °C for 18 to 48 hours to obtain a heat-treated product, and (6) A pressing step. 6. A method for producing a sheet mainly composed of chitosan according to item 5 above, characterized in that the amount of eluted acetic acid is made 9% or less by the heat treatment in (5) above. 7. A sheet mainly composed of chitosan obtained by the production method according to item 5 or 6 above. 8. The sheet according to item 7 above, having the following characteristics. (1) Water absorption amount (g / g): 20 to 120 (2) Breaking strength (N): 5 - 100 (3) Water absorption time (sec): 30 or less

Advantages of the Invention

[0009] The sponge mainly composed of chitosan and the sheet mainly composed of chitosan obtained by the production method of the present invention have a high water absorption rate, do not dissolve or decompose into a flaky state after water absorption, and maintain the breaking strength.

Brief Description of the Drawings

[0010]

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[0011] (Subject of the Present Invention) The present invention relates to a sponge mainly composed of chitosan (hereinafter sometimes referred to as "the sponge of the present invention"), a sheet mainly composed of chitosan (hereinafter sometimes referred to as "the sheet of the present invention"), a method for producing a sponge mainly composed of chitosan (hereinafter sometimes referred to as "the method for producing the sponge of the present invention"), and a method for producing a sheet mainly composed of chitosan (hereinafter sometimes referred to as "the method for producing the sheet of the present invention").

[0012] (Chitosan) The "chitosan" used in the method for producing the sponge and the sheet of the present invention is defined as a deacetylated product of chitin, has a deacetylation degree (also referred to as DAC degree) of 70 to 100%, and is insoluble in water. The molecular weight of the "chitosan" used in the present invention is generally such that the weight average molecular weight (calculated by GPC molecular weight measurement using pullulan as a standard product) is about 10,000 to 4,000,000, preferably 50,000 to 3,000,000, more preferably 100,000 to 2,000,000. The viscosity of the "chitosan" used in the present invention is such that the viscosity of a 0.5% W / W solution at 20°C is 1 to 400 mPa·s, more preferably 5 to 350 mPa·s, and even more preferably 10 to 300 mPa·s.

[0013] (Method for producing chitosan) As the method for producing the "chitosan" used in the present invention, chitosan known per se can be used. For example, those having a deacetylation rate (DAC degree) of about 50 to 100% are used, preferably 70 to 100%. Also, those having a weight average molecular weight (calculated by GPC molecular weight measurement using pullulan as a standard product) of about 10,000 to 4,000,000 are used, preferably 50,000 to 3,000,000, more preferably 100,000 to 2,000,000. The viscosity is such that the viscosity of a 0.5% W / W solution at 20°C is 1 to 400 mPa·s, more preferably 5 to 350 mPa·s, and even more preferably 10 to 300 mPa·s. In addition, the method for removing alkali after producing chitosan by subjecting chitin to an alkali deacetylation reaction includes neutralization by adding an acid, followed by washing with water and dehydration, desalting using a desalting apparatus, or washing with water and dehydration, washing and dehydration with alcohols, removing alkali using an ion exchange resin, etc., without acid neutralization.

[0014] Production examples of the chitosan sponge and chitosan sheet of the present invention are shown below (see Fig. 1). (1) Step of suspending chitosan having a deacetylation degree of 70 to 100% In this step, chitosan having a deacetylation degree of 70 to 100% is added to a solvent (for example, water, pure, etc.) at 0.1 to 5.0% W / W and suspended. The suspension method can, for example, exemplify stirring known per se. The concentration of chitosan in the suspension containing chitosan is 0.1 to 5.0% W / W, and particularly preferably 0.5 to 3.0% W / W is used. In addition, in this step, it may be carried out simultaneously with the following step (2).

[0015] (2) Step of adding acetic acid in an amount of 0.7 mol or more per 1 mol of the amino group of chitosan to the suspension of (1) above The amount of acetic acid added is 0.7 mol or more (preferably 1.0 or more to 1.5 or less) of acetic acid per 1 mol of the amino group of chitosan. The calculation formula for the amount of acetic acid added can, for example, be as follows. Amount of acetic acid added (g) = Amount of chitosan (g) / Molecular weight of chitosan monosaccharide (161) × Molecular weight of acetic acid (60) Amount of acetic acid added (%) = Amount of acetic acid added (g) / Solution weight (g) × 100 The concentration of acetic acid is 0.03 to 4.0% W / W, and particularly preferably 0.05 to 2.5% W / W is used. Preferably, stirring is carried out until the chitosan in the suspension is almost completely dissolved after the addition of acetic acid. As the stirring method, a method known per se can be used, and for example, stirring with a stirrer known per se can be exemplified.

[0016] Preferably, the step of adding ethanol to the solution of (2) above may be included. In this project, ethanol (99%) accounting for 0.01 to 1.0% of the total solution weight is added to the solution in (2) above. After the above addition, if necessary, filtration is carried out using a stainless-steel mesh (e.g., 60 mesh).

[0017] (3) Step of obtaining sherbet frozen ice from the solution in (2) above (particularly, the filtrate obtained from (2) above, the filtrate after ethanol addition) By subjecting the solution in (2) above to the "sherbet freezing process", sherbet-like frozen ice is produced. Here, the "sherbet freezing process" of the present invention does not produce frozen ice by rapid freezing or gradually freezing as in the prior art. Instead, the frozen ice once frozen is crushed, filled into a mold, and frozen again to obtain sherbet-like frozen ice. Also, when the solution in (2) above is crushed together with dry ice, it becomes sherbet-like. Similarly, it is filled into a mold and frozen again to obtain sherbet-like frozen ice. The detailed manufacturing method is as follows. To about 1000 g of the solution in (2) above, 500 g to 700 g of dry ice is added and crushed with a blender or the like to make it sherbet-like. The sherbet temperature is adjusted to -5°C to +5°C. In the production of the sponge-like hemostatic material of the present invention, the freezing method is not particularly limited as long as it can be made sherbet-like as described above. In addition, if the sherbet temperature is low, keep the blender running and bring the sherbet temperature to around 0°C.

[0018] The sherbet-like chitosan is poured into a container such as a tray assuming the thickness of the finished sponge or sheet as needed, and preferably frozen at -10 to -50°C, more preferably at -20 to -40°C, and most preferably at about -30°C. Note that the chitosan, which is the above sherbet frozen ice, can be stored for dozens of days if frozen. When needed, the frozen ice can be subjected to the next step of freeze-vacuum drying treatment.

[0019] (4) Perform lyophilization on the sherbet frozen ice of (3) above to obtain a lyophilized product. Perform lyophilization under vacuum on the frozen chitosan. Note that it can be performed using a lyophilizer known per se. For example, lyophilization under vacuum can be performed under the condition of heating from -30°C to 50°C under vacuum conditions.

[0020] (5) Perform a heat treatment on the lyophilized product of (4) above at 80 to 100°C for 18 to 48 hours to obtain a heat-treated product. In this step, as shown in the following examples, preferably, a heat treatment is performed at 80 to 100°C, preferably about 85 to 95°C, for 18 to 48 hours using a vacuum dryer (under a vacuum drying state). Through this step, a sponge mainly composed of chitosan is produced.

[0021] (6) Pressing step In this step, a chitosan sheet of the present invention is obtained by performing a pressing known per se on the sponge of the present invention. Pressing can use a method known per se. For example, a chitosan sheet of the present invention with a thickness of 0.05 to 3 mm is produced by pressing the sponge of the present invention.

[0022] (γ-ray sterilization treatment) Since acetic acid is added to the sponge and sheet of the present invention in the manufacturing process, as is clear from the following examples, they have antibacterial properties. However, when the sponge and sheet of the present invention are used for surgery or the like, it is necessary to be sterilized. Therefore, the sponge and sheet of the present invention are preferably subjected to γ-ray sterilization treatment. For example, irradiate the sponge and sheet of the present invention with γ-rays of 25 kGy, preferably 50 kGy. Note that, as shown in the following examples, the hemostatic material of the present invention has the required breaking strength (2 N or more) even after irradiation with 50 kGy of γ-rays.

[0023] (Measurement methods for each property of the sponge and sheet) The measurement methods for the respective properties of the sponge and sheet of the present invention are as follows. These were also used in the following examples.

[0024] 〇Degree of deacetylation The degree of deacetylation was calculated from the DAC degree per dry matter by colloidal titration with an aqueous potassium polyvinyl sulfate solution using a toluidine blue solution as an indicator after dissolving the chitosan sample in a 0.5% (w / w) acetic acid solution to a concentration of 0.5% (w / w).

[0025] 〇Clay The viscosity was measured as the rotational viscosity (mPa·s) with a B-type viscometer while maintaining the solution after stirring at 20 °C in a thermostatic bath. The chitosan sample was dissolved in a 0.5% (w / w) acetic acid solution to a concentration of 0.5% (w / w), stirred at room temperature for a certain time, and further stirred with a homogenizer for 2 minutes.

[0026] 〇Water absorption amount For the water absorption in the measurement of the water absorption amount, after measuring the weight (A) of the sample, the sample in a container containing sufficient pure water was immersed for 5 minutes. Then the sample was lifted onto a strainer and drained for 5 minutes, and the weight (B) of the sample was measured. The water absorption amount is represented by (B - A) / A. More specifically, approximately 0.1 g was weighed (A), immersed in pure water for 5 minutes, lifted onto a strainer, drained for 5 minutes, and weighed (B), and obtained by the following formula. Water absorption amount = (B - A) / A

[0027] 〇Water absorption time The JIS L1907 dropping method can be used. For example, 1 drop of 20 °C pure water is dropped onto the specimen, and the time required for complete water absorption is measured.

[0028] 〇Loss on drying The loss on drying was measured by weighing approximately 0.1 g of the specimen (A, with a minimum scale of 0.001 g or less), drying it with hot air at 110 °C for 1 hour, allowing it to cool in a desiccator for 1 hour, and then weighing it (B). The moisture content (%) was calculated as (B - A) / A.

[0029] 〇Breaking strength The breaking strength (breaking strength after water absorption) is measured by cutting the sample into 20 mm squares, immersing it in pure water for 5 minutes, lifting it out with a sieve, and draining the water for 5 minutes. Set it in a dedicated container (diameter φ40 mm, height h15 mm), and use a creep meter (RHEONERII manufactured by Yamaden) to measure the breaking strength by crushing under the following measurement conditions: measurement speed 1 mm / sec, contact diameter 20 mm, measurement strain rate 99.99%, storage pitch 0.04 sec.

[0030] 〇Measurement of the eluted acetic acid concentration In the measurement of the eluted acetic acid concentration, for the measurement of acetic acid, weigh approximately 50 mg of finely chopped sponge, add ultrapure water, stir overnight with a stirrer, and then make up to 50 ml with ultrapure water. Filter with a 0.45 μm filter to obtain a sample solution. Use HPLC (organic acid analysis system, manufactured by Shimadzu Corporation) to measure the eluted acetic acid by post-column pH buffering conductivity detection method under the following conditions. Note that the retention time of acetic acid is around 26.1 minutes. Measure the acetic acid standard solution and the sample solution respectively, and calculate the acetic acid concentration of the sample from the ratio of the peak area values of the standard solution and the sample solution. [Analysis conditions] Apparatus: Carboxylic acid analyzer (manufactured by Shimadzu Corporation) <Separation conditions > Column: Two Shim Pak SCR 102H columns connected in series Mobile phase: 5 mM p-toluenesulfonic acid aqueous solution Mobile phase flow rate: 0.8 ml / min Temperature: 40 °C <Detection conditions > Buffer solution: 5 mM p-toluenesulfonic acid aqueous solution 20 mM Bis-tris aqueous solution containing 100 μM EDTA Buffer solution flow rate: 0.8 ml / min Detector: CDD-6A conductivity detector Injection volume: 10 μL

[0031] (Molar ratio of eluted acetic acid / amino group) The molar ratio of eluted acetic acid / amino group can be calculated from the following formula. Degree of deacetylation less than 100%: Molecular weight of chitosan monomer = Molecular weight of chitosan monomer with 100% degree of deacetylation (161) × Degree of deacetylation (%) / 100 + Molecular weight of chitin monomer (203) × (100 - Degree of deacetylation) / 100 Example) Molecular weight of chitosan monomer with 85% degree of deacetylation = 161 × 85 / 100 + 203 × (100 - 85) / 100 = 167.3 Molar ratio of eluted acetate ion / amino group = {(% of eluted acetic acid in 10 g of chitosan) / 100 / 60} / {((10 g of chitosan - % of eluted acetic acid in 10 g of chitosan) / 167.3 (molecular weight of chitosan monomer with 85% degree of deacetylation))}

[0032] (Chitosan sponge of the present invention) The chitosan sponge of the present invention has the following characteristics according to this example. Weight per volume (mg / cm 3 ): 3 - 30, preferably 5 - 20 pH: 4 - 6 % of eluted acetic acid: 15 or less, 12 or less, 10 or less Molar ratio of eluted acetic acid / amino group: less than 0.3 Water absorption time (sec): 30 or less, 25 or less, 20 or less Water absorption amount (g / g): 20 - 120, preferably 20 - 100 Breaking strength (N): 2 - 100, preferably 3 - 80, more preferably 5 - 70 Pore volume (mL / g): 15 - 45 Pore surface area (m 2 / g): 0.5 - 2.0 Median diameter (μm): 10 - 400 Mode diameter (μm): 10 - 400 Porosity (%): 75 - 95

[0033] (Chitosan sheet of the present invention) The chitosan sheet of the present invention has the following characteristics according to this example. Weight per volume (mg / cm 3 ): 30 - 600, preferably 50 - 400 pH: 4 - 6 Dissolved acetic acid (%): 15 or less, 12 or less, 10 or less Molar ratio of dissolved acetic acid to amino group: less than 0.3 Water absorption time (sec): 30 or less, 25 or less, 20 or less Water absorption amount (g / g): 20 - 120, preferably 20 - 100 Breaking strength (N): 5 - 100, preferably 6 - 80, more preferably 7 - 70 Pore volume (mL / g): 1 - 12 Pore surface area (m 2 / g): 0.5 - 2.0 Median diameter (μm): 10 - 100 Mode diameter (μm): 10 - 100 Porosity (%): 80 - 99

[0034] (Uses of chitosan sponge and chitosan sheet) The uses of the chitosan sponge and chitosan sheet of the present invention are not particularly limited. Since they are natural - derived materials and considering the breaking strength and water absorption amount, hemostatic agents, wound - covering and protecting materials, cosmetics (cosmetic pads), culture substrates (cell culture substrates), food substrates (substrates for cultured meat, cultured shrimp, crab, fish meat, etc.), three - dimensional carriers (biomaterials, bone, implants), etc. can be exemplified.

[0035] Hereinafter, the present invention will be described in detail with reference to examples, but the scope of the present invention is not limited by these examples. It is not limited by these.

Example 1

[0036] (Manufacture of chitosan sponge and chitosan sheet (Lot.No.200518)) (1) 300 g (1%) of chitosan (Lot.No.190427S1 (deacetylation degree = 83.7%): product of Koyo Chemical Co., Ltd.) as the raw material was used. 29.59 kg of pure water was added to the above - mentioned raw material to obtain a chitosan suspension. (2) 112 g of acetic acid (special grade, manufactured by Kanto Chemical Co., Inc.) {acetic acid addition amount = amount of chitosan (300 g) / molecular weight of chitosan monomer (161) × molecular weight of acetic acid (60) = 112 g} was added to the above chitosan suspension. Further, the chitosan suspension after the addition of acetic acid was stirred overnight until the chitosan was almost completely dissolved to obtain a chitosan solution. In addition, 0.5 w / w% ethanol was added to the above chitosan solution. The chitosan solution after the addition of ethanol was filtered through a stainless steel mesh (60 mesh) to obtain a filtrate. The filtrate was a 1.0 w / w% chitosan / 0.37 w / w% acetic acid solution. (3) 500 g of dry ice was added to about 1000 g of the above filtrate and pulverized with a blender to make it into a sherbet shape. The sherbet temperature was adjusted to -5°C to +5°C. The sherbet-shaped chitosan was filled into a tray. (4) The frozen sherbet-shaped chitosan was subjected to freeze-vacuum drying treatment (stored in a freezer at -30°C for 5 hours) (B220209FNP, B220224FNP, B220302FNP). (5) The freeze-dried product was heat-treated under the following conditions to obtain a chitosan sponge. B200518NP: 90°C for 24 h, 92°C for 24 h, 95°C for 24 h, 100°C for 24 h (6) The above chitosan sponge was press-processed to obtain a chitosan sheet. B200518: 90°C for 24 h B220323: 90°C for 24 h, 85°C for 24 h, 90°C for 24 h The physical properties of the obtained chitosan sponge and chitosan sheet are shown in FIGS. 2 to 5.

Example 2

[0037] (Production of chitosan sponge and chitosan sheet (Lot. No. 200714)) In the same manner as in Example 1, a chitosan sponge and a chitosan sheet of Lot. No. 200714 (heat treatment: 90°C for 24 h) were produced. The physical properties of the chitosan sheet are shown in FIG. 4. When the results of Example 1 and this example were combined, pressing reduced the thickness of chitosan and increased the weight per volume. However, even after pressing, the chitosan sheet, like the chitosan sponge, had a short water absorption time, did not dissolve or break down into pieces after water absorption, and maintained its breaking strength.

Example 3

[0038] (SEM Observation and Pore Distribution Measurement) SEM observation and pore distribution measurement were performed on the chitosan sheets and chitosan sponges obtained in Examples 1 and 2 above. Each condition is as follows. · Chitosan sheet Lot No. 200714, non-sterilized product Specimen dimensions: 20×20 mm, t = 1.67 mm · Chitosan sponge Lot No. 200518, non-sterilized product, before pressing Specimen dimensions: 20×20 mm, t = 13.6 mm

[0039] 〇SEM Observation Each specimen was cut in half, and SEM images were taken with a scanning electron microscope. The photographed figures are shown in Fig. 6. It was confirmed that the chitosan sponge before pressing had a similar shape on the surface and cross-section and was a sponge structure that was nearly homogeneous as a whole. It was confirmed that the cross-sectional shape of the chitosan sheet was compressed by pressing.

[0040] Each specimen was cut in half, and pore distribution measurement was performed by mercury intrusion porosimetry using a pore distribution measurement device (AutoPore V9620, manufactured by Micromeritics). Approximately 0.003 - 0.022 g of the sample was collected in a standard 5 cc powder cell, and measurement was performed under the condition of an initial pressure of 4 kPa (equivalent to about 0.6 psia and a pore diameter of about 320 μm). The mercury parameters were set to a mercury contact angle of 130 degrees and a mercury surface tension of 485 dynes / cm, which are the default values of the device. The measurement results are shown in Figs. 7 and 8. It was confirmed that the pore volume, median diameter, mode diameter, and pore distribution decreased due to the pressing process of the chitosan sponge, but the pore surface area and porosity were maintained.

Example 4

[0041] The bacterial content in the following two types of samples was measured by commissioning an external inspection agency. 〇Sample Unsterilized chitosan sheet 1 (Lot No. 190717) Unsterilized chitosan sheet 2 (Lot No. 2003031-1) <Inspection items> Total viable count (standard agar medium) Coliform group (desoxycholate medium)

[0042] The measurement results are shown in Table 1 below. Since the water absorption of the chitosan sheet was high, dilution was performed not at 10-fold but at 100-fold and 1000-fold. No colonies were observed in the samples diluted 100-fold and 1000-fold for the total viable count (less than 30 CFU / g at each dilution stage). Therefore, the total viable count was 3.0×10 3 CFU / g or less. In addition, the coliform group (fermentation tube method using BGLB medium) was also tested, but no gas generation was observed. From the above, it was confirmed that the chitosan sheet, which is the final processed product of the present invention, has antibacterial properties.

[0043]

Table 1

[0044] (General evaluation) From the results of the above examples, due to the pressing process of the chitosan sponge, the pore size and the like of the chitosan sheet changed compared to the chitosan sponge. However, the chitosan sponge and chitosan sheet of the present invention have a high water absorption rate and maintain the breaking strength after water absorption.

Industrial applicability

[0045] The present invention can provide a chitosan sponge and a chitosan sheet that have a high water absorption rate, do not dissolve or disintegrate into pieces after water absorption, and maintain the breaking strength.

Claims

1. A method for manufacturing a sponge mainly composed of chitosan, comprising the following steps: (1) A step of suspending chitosan having a deacetylation degree of 70 to 100%; (2) A step of adding 0.7 mol or more of acetic acid per 1 mol of the amino group of the chitosan to the suspension in (1); (3) A step of obtaining sherbet frozen ice from the filtrate obtained from the solution in (2); (4) A step of performing freeze-drying on the sherbet frozen ice in (3) to obtain a freeze-dried product; and (5) A step of performing heat treatment on the freeze-dried product in (4) at 80 to 100 °C for 18 to 48 hours to obtain a heat-treated product, wherein, between the step (2) and the step (3), the method includes a step of adding ethanol to the solution. A manufacturing method.

2. The method for manufacturing a sponge mainly composed of chitosan according to Claim 1, wherein the amount of eluted acetic acid is 9% or less by the heat treatment in (5).

3. The method for manufacturing a sponge according to Claim 1 or 2, wherein the sponge has the following characteristics: (1) Water absorption amount (g / g): 20 to 120 (2) Breaking strength (N): 5 to 100 (3) Water absorption time (sec): 30 or less

4. A method for manufacturing a sheet mainly composed of chitosan, comprising the following steps: (1) A step of suspending chitosan having a deacetylation degree of 70 to 100%; (2) A step of adding 0.7 mol or more of acetic acid per 1 mol of the amino group of the chitosan to the suspension in (1); (3) A step of obtaining sherbet frozen ice from the filtrate obtained from the solution in (2); (4) A step of performing freeze-drying on the sherbet frozen ice in (3) to obtain a freeze-dried product; (5) A step of performing heat treatment on the freeze-dried product in (4) at 80 to 100 °C for 18 to 48 hours to obtain a heat-treated product; and (6) A pressing step, wherein, between the step (2) and the step (3), the method includes a step of adding ethanol to the solution. A manufacturing method.

5. The method for manufacturing a sheet mainly composed of chitosan according to Claim 4, wherein the amount of eluted acetic acid is 9% or less by the heat treatment in (5).

6. The method for manufacturing a sheet according to Claim 4 or 5, wherein the sheet has the following characteristics: (1) Water absorption amount (g / g): 20 to 120 (2) Breaking strength (N): 5 to 100 (3) Water absorption time (sec): 30 or less

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