High-concentration dispersion of nanosized chitin

Abstract

To provide a high-concentration dispersion of nanosized chitin having a uniform and fine fiber width.SOLUTION: A dispersion of nanosized chitin contains nanosized chitin with a fiber width of 20 nm or less in a concentration of 10 wt.%-30 wt.%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a high-concentration dispersion of nano-chitin, and more particularly to a dispersion containing a high concentration of nano-chitin having a uniform fiber width. [Background technology]

[0002] Chitin nanofibers, obtained by defibrating chitin, which is abundant in the shells of crustaceans such as shrimp and crabs, are transparent and highly water-swellable, and their use in various fields is being investigated. Proposed methods for producing chitin nanofibers include, for example, a method in which purified β-chitin with a crystallinity of 90% or less is immersed in an acidic liquid with a pH of 5 or less, and then the immersed β-chitin is defibrated (Patent Document 1), and a method in which purified α-chitin is partially deacetylated, immersed in an acidic liquid with a pH of 5 or less, and then defibrated (Patent Document 2). In the methods for producing chitin nanofibers described in Patent Documents 1 and 2, it is proposed to impart a positive charge to glucosamine residues that are thought to be distributed on the surface of chitin nanofibrils, thereby generating charge repulsion between the microfibrils of the chitin nanofibrils and facilitating the defibration of the microfibrils.

[0003] In the chitin nanofiber manufacturing methods described in Patent Documents 1 and 2, the defibration process of purified β-chitin or partially deacetylated purified α-chitin is carried out using defibration and grinding equipment such as a propeller mixer, cutter mixer, ultrasonic homogenizer, high-pressure homogenizer, or twin-screw kneader. Furthermore, a method for defibrating chitin microfibrils using water jet technology has also been proposed (Patent Document 3).

[0004] As described in Patent Documents 1 to 3, chitin nanofibers are generally obtained by mechanically or physically defibrating purified chitin. However, with such methods, it is difficult to easily obtain chitin nanofibers with a uniform fiber width, and repeated defibration processes are required to achieve a uniform fiber width for the chitin nanofibers. Furthermore, in the manufacturing methods disclosed in Patent Documents 1 to 3, etc., an aqueous dispersion of chitin is subjected to a defibration treatment, so the chitin nanofibers are obtained in a dispersed state in water, and it is difficult to obtain chitin nanofibers as a highly concentrated dispersion. This means that the manufacturing methods cannot be said to be economically superior for use as a raw material for N-acetylglucosamine and oligosaccharides, or in medical materials, functional foods, cosmetics, feed, etc.

[0005] Therefore, there is a demand for a dispersion containing a high concentration of nano-chitin with uniform fiber width, which is highly usable in a variety of fields. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-102782 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-180309 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-056456 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above, an object of the present invention is to provide a dispersion containing a high concentration of nano-sized chitin having a uniform fiber width. [Means for solving the problem]

[0008] As a result of extensive research to solve the above problems, the inventors discovered that the chitin precipitate obtained by treating chitin with a high concentration of alkali or acid at low temperature, followed by dilution and neutralization, is nano-sized chitin.Further research led to the discovery of a dispersion containing nano-sized chitin with a fiber width of 20 nm or less at a concentration of 10% to 30% by weight, thereby completing the present invention.

[0009] That is, the present invention relates to the following. [1] A dispersion of nano-chitin containing nano-chitin having a fiber width of 20 nm or less at a concentration of 10% by weight to 30% by weight. [2] The dispersion according to [1], wherein the concentration of nano-chitin is 15% by weight to 25% by weight. [3] The dispersion according to [1] or [2], wherein the fiber width of the nano-sized chitin is 10 nm or less. [4] The dispersion according to any one of [1] to [3], wherein the degree of deacetylation of the nano-chitin is 8% or less. [5] The dispersion according to any one of [1] to [4], which is a wet cake dispersion. [6] Dispersion of deacetylated nano-chitin. [7] The dispersion according to [6], wherein the degree of deacetylation is 10% to 50%. [8] A gel containing the dispersion according to [6] or [7]. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a dispersion containing a high concentration of nano-chitin having a uniform fiber width. The nano-chitin contained in the dispersion of the present invention can be deacetylated while maintaining the nano-chitin form. The dispersion of the deacetylated nano-chitin can form a gel at a low concentration by making the liquid acidic or by dispersing it in an acidic aqueous solution. The dispersion is useful as a raw material for N-acetylglucosamine and oligosaccharides, a medical material, a plastic material, etc., and also as an ingredient for functional foods, cosmetics, feed, etc. [Brief explanation of the drawings]

[0011] [Figure 1] Fig. 1 shows an image of the nano-chitin dispersion of Example 1 observed with a transmission electron microscope. The bar in the figure indicates 100 nm. [Figure 2] FIG. 2 is a diagram showing the appearance of the gel formed when the dispersion of deacetylated nano-chitin in Example 2 was acidified. [Figure 3] FIG. 3 is a diagram showing the appearance of the gel formed when the dispersion of the deacetylated nano-chitin of Example 3 was acidified. [Figure 4] FIG. 4 is a diagram showing the appearance of the gel formed when the dispersion of the deacetylated nano-chitin of Example 4 was acidified. [Figure 5] 5 shows an image, observed by a transmission electron microscope, of the gel formed when the dispersion of the deacetylated nano-chitin of Example 4 was acidified. The bar in the figure indicates 100 nm. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention provides a dispersion containing a high concentration of nano-chitin having a uniform fiber width (hereinafter also referred to as "the dispersion of the present invention" in this specification). The dispersion of the present invention contains nano-chitin having a fiber width of 20 nm or less at a concentration of 10 wt % to 30 wt %.

[0013] Here, "nano-chitin" refers to chitin whose fiber width is on the order of nanometers, i.e., less than 1 μm. This refers to chitin. The nano-chitin contained in the dispersion of the present invention has a fiber width of 20 nm or less, preferably 10 nm or less, and an average fiber width of 3 nm to 10 nm, preferably 3 nm to 5 nm. The fiber width of the nano-chitin contained in the dispersion of the present invention is measured from an image obtained by appropriately diluting the dispersion of the present invention with water or the like and observing it under a transmission electron microscope. On the other hand, when the nano-chitin contained in the dispersion of the present invention was observed under a transmission electron microscope, it was found to be spirally twisted in the longitudinal direction, making it impossible to clearly measure the fiber length. However, as will be described later, when the dispersion of the present invention was prepared, the molecular weight of the nano-chitin contained in the dispersion was reduced compared to the chitin used as the starting material, but the degree of this reduction was similar to that when prepared by a conventional physical defibration method, and it is presumed that the fiber length would be almost the same as that of chitin nanofibers prepared by a physical defibration method.

[0014] The nano-chitin contained in the dispersion of the present invention may be obtained from either α-chitin present in crustaceans such as crabs and shrimp, or β-chitin present in the backbone of squid and tube worms.

[0015] The dispersion of the present invention contains the above-mentioned nano-chitin at a concentration of usually 10% by weight to 30% by weight, and preferably 15% by weight to 25% by weight. Here, the concentration of nano-chitin contained in the dispersion of the present invention is calculated by quantifying the chitin content in the dispersion of the present invention as solid content using a normal pressure heating drying method, and then calculating the quantitative value obtained from the weight of the dispersion of the present invention before drying.

[0016] The degree of deacetylation of the nano-chitin contained in the dispersion of the present invention is preferably 8% or less, more preferably 5% or less. In addition, taking into account the degree of deacetylation of the chitin used as a raw material, the degree of deacetylation of the nano-chitin contained in the dispersion of the present invention is usually about 1% to 5%. The degree of deacetylation of nano-chitin can be measured by colloid titration with a 1 / 400N aqueous solution of potassium polyvinyl sulfate using toluidine blue as an indicator.

[0017] In the dispersion of the present invention, as described above, nano-chitin having a fine and uniform fiber width is dispersed in a solvent such as water at a high concentration of 10% to 30% by weight, and has a wet cake-like appearance.

[0018] The dispersion of the present invention can be prepared, for example, by crushing chitin to the extent that it can pass through a 42-mesh sieve, immersing the chitin powder in a highly concentrated alkaline aqueous solution, leaving it to stand at a temperature below room temperature, diluting it with ice, neutralizing it with a highly concentrated acid to precipitate chitin, washing the chitin dispersion with water to desalt it, and dehydrating it as necessary. The dispersion of the present invention can also be prepared by immersing pulverized chitin powder in a highly concentrated aqueous solution of acid and then neutralizing with a highly concentrated alkali. However, taking into consideration the desired reduction in molecular weight of the nano-sized chitin, it is preferable to immerse the powder in an aqueous alkali solution and then neutralize with an acid.

[0019] Chitin can be pulverized using a conventional pulverizer, such as a cutter mill pulverizer, a hammer mill pulverizer, a rolling ball mill pulverizer, a dry airflow pulverizer, or a counter-airflow dry pulverizer.

[0020] As the high-concentration alkaline aqueous solution, a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, etc., with a concentration of about 40% by weight to 48% by weight can be used. The high-concentration alkaline aqueous solution is used in an amount sufficient to fully immerse the chitin powder. The chitin powder is immersed in a high-concentration alkaline aqueous solution preferably at a temperature below room temperature (25°C), more preferably below 20°C, and even more preferably below 15°C, for 10 to 24 hours, and more preferably for 15 to 20 hours.

[0021] After the soaking process, adding ice causes the chitin to dissolve in a viscous state, so the solution is stirred until it becomes transparent. The dilution process by adding ice is carried out at 25°C or below, preferably 0°C or below, and more preferably -10°C or below, until the chitin powder soaked in the solution becomes homogeneous (until the alkali concentration reaches about 10 (w / v)%). The chitin solution obtained by the above dilution treatment is neutralized by adding approximately 30% to 40% by weight of an acid, such as concentrated hydrochloric acid, at a temperature of 25°C or below, preferably 0°C or below, so that the pH of the solution is approximately 7 to 8.5. The immersion treatment in the alkaline aqueous solution is preferably carried out at a low temperature of 25°C or below, more preferably 20°C or below, and the dilution and neutralization are carried out at a low temperature of 25°C or below, preferably 0°C or below, thereby suppressing the deacetylation of chitin.

[0022] Washing with water is carried out using 250 to 500 times the weight of the precipitated chitin dispersion, and this washing procedure is usually repeated 10 to 20 times. This washing procedure can sufficiently desalt the precipitated chitin dispersion. In the present invention, washing with water is usually carried out until the salt concentration of the precipitated chitin dispersion becomes 0.01% by weight or less. The degree of desalination can be confirmed by measuring the salinity using a digital salinity meter.

[0023] The precipitated chitin dispersion can be dehydrated by any conventional dehydration method, preferably by centrifugal filtration, pressure filtration, or the like.

[0024] The nano-chitin contained in the dispersion of the present invention has the properties of being easily degradable by enzymes such as chitinase, and also easily chemically modified by deacetylation and the like. Furthermore, the dispersion of the present invention contains nano-chitin, which has a fine and uniform fiber width, at a higher concentration than ever before, and can therefore be efficiently used as a raw material for N-acetylglucosamine and oligosaccharides, as a filler for medical materials and plastic materials, and as an ingredient in functional foods, cosmetics, feed, etc.

[0025] Furthermore, the present invention provides a dispersion of deacetylated nano-chitin (hereinafter also referred to in this specification as "dispersion of deacetylated nano-chitin of the present invention") as one embodiment of the chemical modification of nano-chitin contained in the dispersion of the present invention. In the present invention, the degree of deacetylation of the deacetylated nano-chitin is preferably 10% to 50%, and more preferably 15% to 40%.

[0026] When the dispersion of deacetylated nano-chitin of the present invention is acidified by adding a small amount of acid or dispersed in an acidic aqueous solution, the dispersibility of the deacetylated nano-chitin is improved, and a uniform gel can be formed at a low concentration of deacetylated nano-chitin of 1% to 2% by weight. When the deacetylation degree of nano-chitin exceeds 18%, the transparency of the gel formed increases, and when the deacetylation degree of nano-chitin reaches about 40%, a viscous gel exhibiting almost transparent thixotropy is obtained. The acid added to improve the dispersibility of the dispersion of the deacetylated nano-chitin of the present invention or to form a gel is not particularly limited as long as it can make the dispersion acidic. However, from the viewpoint of suppressing the deacetylated nano-chitin from being degraded into smaller molecules, a weak acid is preferable, and an organic acid is more preferable. Furthermore, for use as a food ingredient, an edible acid is preferable. Examples of edible organic acids include lactic acid and citric acid. etc. Furthermore, the amount of acid added to the dispersion of deacetylated nanochitin of the present invention may be small, and may be an amount that results in an acid concentration in the dispersion of about 0.5% by weight to 1% by weight. When dispersing the deacetylated nano-chitin of the present invention in an acidic aqueous solution, the above-mentioned aqueous acid solution can be used as the acidic aqueous solution, and the concentration can be as low as about 0.5% to 1% by weight.

[0027] The dispersion of deacetylated nano-chitin of the present invention can be obtained by warming or heating the above-mentioned dispersion of nano-chitin of the present invention in an alkaline aqueous solution and then washing with water. As the alkaline aqueous solution, an aqueous solution of sodium hydroxide, potassium hydroxide, etc. is preferably used. The concentration of the alkaline aqueous solution is appropriately set depending on the desired degree of deacetylation as long as the crystalline structure of chitin is not swollen. An alkaline aqueous solution with a concentration of 10 (w / v)% to 55 (w / v)%, preferably 10 (w / v)% to 40 (w / v)%, and more preferably 30 (w / v)% to 36 (w / v)% is usually used. The temperature for heating in the alkaline aqueous solution is appropriately set depending on the desired degree of deacetylation, and is usually 45°C to 80°C, and preferably 45°C to 60°C. The warming or heating time in the alkaline aqueous solution is also appropriately set depending on the desired degree of deacetylation, and is usually 5 to 72 hours, preferably 5 to 17 hours, and more preferably 5 to 6 hours. The degree of deacetylation of nano-chitin can be adjusted by adjusting the concentration of the alkaline solution, the heating or heating temperature, and the heating or heating time. For example, when the deacetylation reaction is carried out in a 30 (w / v)% to 36 (w / v)% aqueous sodium hydroxide solution at 60°C for 5 hours, the degree of deacetylation is 15% to 16%, when the deacetylation reaction is carried out at 80°C for 5 hours, the degree of deacetylation is 18% to 19%, and when the deacetylation reaction is carried out at 45°C for 72 hours, the degree of deacetylation is 25% to 26%.

[0028] After warming or heating in an alkaline aqueous solution, neutralization treatment with acid may be carried out. However, as mentioned above, the deacetylated nano-chitin of the present invention forms a gel with low concentrations of acid. Therefore, to remove the alkali from the dispersion of deacetylated nano-chitin, it is preferable to repeatedly wash the dispersion with approximately 250 to 500 times the weight of water 10 to 20 times. Furthermore, if the dispersion of the deacetylated nano-chitin of the present invention becomes weakly acidic, it may swell and gel, making it impossible to recover by filtration. Therefore, it is preferable to stop washing with water when the pH of the filtrate after filtration reaches a level of 8.5 to 9.

[0029] As described above, when the dispersion of the deacetylated nano-chitin of the present invention is made acidic or dispersed in an acidic aqueous solution, the dispersibility of the deacetylated nano-chitin is improved, and a uniform gel can be formed at a low concentration.By adjusting the degree of deacetylation, it is possible to obtain a highly transparent gel or a gel that exhibits thixotropy. The dispersion of deacetylated nano-chitin of the present invention can be further subjected to chemical modification. [Example]

[0030] The present invention will be described in detail below with reference to examples.

[0031] [Example 1] Dispersion containing high concentration of nano-chitin (wet cake nano-chitin) A dispersion containing a high concentration of nano-chitin was prepared as follows. Crab shell-derived α-chitin powder (42 mesh sieved product, deacetylation degree = 1.0% - 2.0%) To 0% chitin powder ("Chitin L-PC", manufactured by Koyo Chemical Co., Ltd.), 10 times the weight of a 48% sodium hydroxide aqueous solution was added, and the sodium hydroxide aqueous solution was thoroughly permeated into the chitin powder, after which it was left to stand overnight at 20°C. Next, crushed ice was added until the concentration of sodium hydroxide reached about 10% (w / v), and the mixture was stirred at -10°C or below until it became a homogeneous liquid. Next, concentrated hydrochloric acid was added while adding ice to neutralize the solution until the pH reached about 8.0 to 8.5, thereby precipitating chitin. The precipitated chitin dispersion was repeatedly washed with large amounts of water and desalted until the salt content measured with a digital salinity meter (ES-421, manufactured by Atago Co., Ltd.) was 0.01% by weight or less. The desalted chitin dispersion was dehydrated by pressure filtration (filter press) (manufactured by Yabuta Kikai Co., Ltd.) to obtain a wet cake-like dispersion.

[0032] The wet cake-like dispersion obtained above was observed with a transmission electron microscope (TEM). Specifically, the dispersion obtained above was diluted with purified water to a chitin concentration of approximately 2.5% by weight, and a sample for TEM observation was prepared. The sample was then observed at a magnification of 50,000 times using a JEM-2100 (manufactured by JEOL Ltd.). The TEM image is shown in Figure 1.

[0033] As shown in Figure 1, the obtained dispersion was confirmed to be a dispersion of nano-chitin in which chitin was defibrated down to elementary microfibril units. The fiber width of nano-chitin was measured from the observation image of nano-chitin shown in Figure 1, and was found to be less than 10 nm, making it impossible to accurately measure the fiber length. Furthermore, the average fiber width calculated from the fiber width measurement was 3 nm to 5 nm. On the other hand, the nano-chitin observed was twisted in a spiral shape in the longitudinal direction, and as mentioned above, it was not possible to accurately measure the fiber length.

[0034] [Test Example 1] Measurement of nano-chitin content and deacetylation degree of nano-chitin in the nano-chitin dispersion of Example 1 The nano-chitin content concentration and the degree of deacetylation of the nano-chitin of the dispersion of Example 1 were measured as follows.

[0035] (1) Measurement of nano-chitin concentration The solid content of the nano-chitin dispersion of Example 1 was determined by the normal pressure heat drying method, and the nano-chitin content concentration was calculated from the weight of the dispersion before drying.

[0036] (2) Measurement of the degree of deacetylation 1380 g of N,N-dimethylacetamide was weighed into a 2 L glass beaker that had previously contained a stirrer, and stirred with the stirrer. 120 g of lithium chloride was added and dissolved to prepare a chitin solution. The nano-chitin dispersion from Example 1 was dried by heating under normal pressure, and 2.5 g of the resulting solids were weighed out and the chitin solution was added to make a total of 500 g. After stirring overnight to dissolve, 1.0 g of the resulting nano-chitin solution was weighed out and made up to 50 mL with deionized water. Three drops of 0.1 (w / v)% toluidine blue were added and mixed, and the solution was titrated with a 1 / 400 N aqueous solution of potassium polyvinyl sulfate (PVSK). (The end point was when the liquid color changed from blue to reddish purple and remained reddish purple for at least 3 seconds.) The molar masses of the glucosamine unit and acetylglucosamine unit in nano-chitin were set to 161 and 203, respectively, and the degree of deacetylation was calculated from the titration value.

[0037] The measurement results of (1) and (2) above are shown in Table 1.

[0038] [Table 1]

[0039] As shown in Table 1, the nano-chitin dispersion of Example 1 contained nano-chitin at a high concentration of 20% by weight. Furthermore, as shown in Table 1, the degree of deacetylation of the nano-chitin in the dispersion of nano-chitin in Example 1 was 5%, and it was found that deacetylation had progressed less than in the chitin powder used as the starting material.

[0040] [Example 2] Dispersion of deacetylated nano-chitin The nano-chitin dispersion of Example 1 was diluted, and 9.0 g of the diluted solution (nanochitin content = 7 wt%) was dispersed in water to a total volume of 30 mL, and 30 mL of 48 wt% sodium hydroxide was added and stirred, and the mixture was heated to 60°C and deacetylated for 5 hours. The sodium hydroxide concentration during the reaction was approximately 36 (w / v)%. After the reaction, the dispersion of deacetylated nanochitin was repeatedly washed with a large amount of water until the pH of the washing liquid (filtrate) reached 8.5 to 9.0. The degree of deacetylation of the deacetylated nanochitin in the obtained dispersion was measured in the same manner as in Test Example 1 above, and was found to be 15.7% to 16.2%. When the resulting dispersion of deacetylated chitin was acidified by adding a few drops of acetic acid, it was found to gel at low concentrations (1.0% to 2.0% by weight) of nano-chitin. The appearance of the resulting deacetylated chitin gel is shown in Figure 2. As shown in FIG. 2, when the dispersion of the deacetylated nano-chitin of Example 2 was acidified, the dispersion exhibited a uniform and viscous gel-like state.

[0041] [Example 3] Dispersion of deacetylated nano-chitin A dispersion of deacetylated nano-chitin was prepared in the same manner as in Example 2, except that the deacetylation reaction was carried out at 80°C for 5 hours. The degree of deacetylation of the deacetylated nano-chitin in the obtained dispersion was measured using the same method as in Test Example 1, and was found to be 18.8%. The reason why deacetylation did not proceed significantly under the above deacetylation conditions is thought to be that the interior of the crystalline structure of the nano-chitin did not swell, and the acetamide on the fiber surface or in the amorphous portion was deacetylated. When a few drops of acetic acid were added to the dispersion of deacetylated nano-chitin in Example 3 to make it acidic, a highly transparent gel was formed at a nano-chitin concentration of 1.6 wt % (Figure 3).

[0042] [Example 4] Dispersion of deacetylated nano-chitin A dispersion of deacetylated nano-chitin was prepared in the same manner as in Example 2, except that the deacetylation reaction was carried out in a 52.7 (w / v)% aqueous sodium hydroxide solution at 60°C for 5 hours. The degree of deacetylation of the deacetylated nanochitin in the obtained dispersion was measured in the same manner as in Test Example 1 above, and was found to be 40%. When a few drops of acetic acid were added to the dispersion of deacetylated nano-chitin in Example 4 to make it acidic, a nearly transparent gel was formed at a nano-chitin concentration of 1.2 wt % (Figure 4). As shown in FIG. 4, the gel formed by the deacetylated nano-chitin of Example 4 exhibits thixotropy, and the gel does not fall even when the bottle filled with the gel is turned upside down. It showed a strong viscosity that was not too strong. Furthermore, the gel formed by the deacetylated nano-chitin of Example 4 was observed by TEM in the same manner as the nano-chitin dispersion of Example 1. The results are shown in FIG. As shown in Figure 5, the TEM image showed uniform dispersion of nano-chitin, but many crystals that were short in the axial direction were observed.

[0043] [Example 5] Dispersion of deacetylated nano-chitin A dispersion of deacetylated nano-chitin was prepared in the same manner as in Example 2, except that the deacetylation reaction was carried out in a 30 (w / v)% aqueous sodium hydroxide solution at 45°C for 72 hours. The degree of deacetylation of the deacetylated nano-chitin in the obtained dispersion was measured in the same manner as in Test Example 1 above, and was found to be 26.4%. When the dispersion of deacetylated nano-chitin from Example 5 was acidified by adding a few drops of acetic acid, a gel was formed at a nano-chitin concentration of 1.8 wt %.

[0044] [Test Example 2] Measurement of molecular weight of nano-chitin and deacetylated nano-chitin The molecular weights of the nano-chitin and deacetylated nano-chitin contained in the dispersion of nano-chitin in Example 1 and the dispersion of deacetylated nano-chitin in Example 5 were measured as follows. The dispersion of nano-chitin from Example 1 and the dispersion of deacetylated nano-chitin from Example 5 were each immersed in a 48 wt% aqueous solution of sodium hydroxide, and a deacetylation reaction was carried out at 85°C for 17 hours.After neutralization, the deacetylated product (deacetylation degree ≧85%) was recovered, dissolved in a 0.5 wt% aqueous solution of acetic acid, and subjected to gel permeation chromatography (GPC) analysis under the following conditions. For comparison, the chitin used as the starting material ("Chitin L-PC", manufactured by Koyo Chemical Co., Ltd.) and purified chitin ("Chitin TC-L", manufactured by Koyo Chemical Co., Ltd.) were also treated in the same manner and their molecular weights were measured. <Molecular weight measurement conditions> (i) Column: TSK Gel G6000PWXL-CP and TSK Gel G3000PWXL-CP (Tosoh Corporation) (ii) Eluent: 0.25 M acetic acid-0.25 M sodium acetate buffer (iii) Flow rate: 0.5mL / min (iv) Sample injection volume: 200 μL (v) Oven temperature: 40°C (vi) Detector: RI (differential refractive index) detector (vii) Standard sample: pullulan (viii) Analysis time: 60min The measurement results are shown in Table 2.

[0045] [Table 2]

[0046] As mentioned above, the TEM image shown in Figure 1 did not confirm the presence of fibers with sufficient length for the nano-chitin in the dispersion of Example 1. However, the molecular structure shown in Table 2 The quantitative measurement results indicated that no significant decrease in the average molecular weight (lowering of molecular weight) was observed in the nano-chitin, suggesting that fiber breakage did not occur significantly. Furthermore, no significant decrease in average molecular weight (lowering of molecular weight) was observed in the deacetylated nano-chitin present in the dispersion of Example 5, suggesting that the nano-chitin was deacetylated while maintaining its form.

[0047] As described above, the dispersion of Example 1 was a dispersion in which nano-sized chitin, which had a uniform fiber width of 10 nm or less and was defibrated almost to elementary microfibril units, was dispersed at an unprecedentedly high concentration of 20% by weight. Because such dispersions contain uniform nano-chitin at high concentrations, they can be used as raw materials or starting materials to deacetylate nano-chitin while maintaining its morphology, as shown in Examples 2 to 5. The deacetylated nano-chitin can form a gel at low concentrations when the dispersion is acidified or dispersed in an acidic aqueous solution. Depending on the degree of deacetylation of the nano-chitin, a highly transparent gel or a gel with high viscosity and thixotropy can be obtained. It is also possible to consider further derivatization of the deacetylated nano-chitin. The dispersion of the present invention is also useful as a source of N-acetylglucosamine and oligosaccharides. Furthermore, the dispersion of the present invention is useful as a medical material, a filler in resin, a paper quality improver, etc., and can also be used as an ingredient in functional foods (particularly as prebiotics), cosmetics, feed, etc. [Industrial Applicability]

[0048] As described above in detail, the present invention can provide a nano-chitin dispersion containing a high concentration of nano-chitin having a uniform fiber width. The nano-chitin contained in the dispersion of the present invention can be deacetylated while maintaining the nano-chitin form. The dispersion of the deacetylated nano-chitin can form a gel at a low concentration by making the liquid acidic or by dispersing it in an acidic aqueous solution. The dispersion of the present invention can be suitably used as a raw material for N-acetylglucosamine or oligosaccharides, a medical material, a plastic material, etc., and also as an ingredient for functional foods, cosmetics, feed, etc.

Claims

1. A method for producing a dispersion of deacetylated nano-chitin, which comprises warming or heating a wet cake-like dispersion containing nano-chitin having a fiber width of 20 nm or less at a concentration of 10% by weight to 30% by weight in an alkaline aqueous solution, and then washing with water.

2. The method according to claim 1, wherein the concentration of nano-chitin in the wet cake dispersion is 15% by weight to 25% by weight.

3. The method according to claim 1 or 2, wherein the fiber width of the nano-chitin contained in the wet cake-like dispersion is 10 nm or less.

4. The method according to any one of claims 1 to 3, wherein the concentration of the alkaline aqueous solution is 10 (w / v) % to 40 (w / v) %.

5. The method according to any one of claims 1 to 4, wherein the temperature for heating in the alkaline aqueous solution is 45°C to 80°C.

6. The method according to any one of claims 1 to 5, wherein the warming or heating time in the alkaline aqueous solution is 5 to 72 hours.

7. The method according to any one of claims 1 to 6, wherein the deacetylation degree of the deacetylated nanochitin is 10% to 50%.

8. A method for producing a gel containing a dispersion of deacetylated nano-chitin, which comprises acidifying the liquid of the dispersion of deacetylated nano-chitin produced by the method according to any one of claims 1 to 7, or dispersing the dispersion in an acidic aqueous solution.

Images