JP6004331B2 - Processed cellulose airgel and method for producing the same, and method for producing regenerated cellulose hydrogel - Google Patents

Description

  The present invention relates to a processed cellulose aerogel, a method for producing the same, and a method for producing a regenerated cellulose hydrogel.

  Airgels and hydrogels containing cellulose fibers (hereinafter also referred to as “cellulose aerogels” and “cellulose hydrogels”) are attracting attention as industrial materials, medical materials, and edible materials. Cellulose hydrogel is a gel in which water is retained in pores (holes) in a three-dimensional network structure of cellulose fibers, and cellulose airgel is obtained by replacing this water with air. Furthermore, when the air in the airgel is replaced with water again, a cellulose hydrogel is obtained.

  For example, Patent Document 1 discloses a molding material using an airgel obtained by drying a hydrogel of bacterial cellulose made of cellulose produced from bacteria. Patent Document 2 discloses a composite material using bacterial cellulose hydrogel.

JP-A-62-36467 JP 2006-241450 A

  As described above, since the cellulose hydrogel contains water, it is heavy, and the cost for transportation increases. In order to reduce the cost, it has been proposed to dry the cellulose hydrogel, transport it as a cellulose aerogel, and restore it to the cellulose hydrogel where it is used. However, conventional cellulose aerogels are not sufficiently reconstituted into cellulose hydrogel, and there are work problems such as labor and time required for restoration, and appearance problems such as the occurrence of white remaining portions that do not allow water to penetrate. It was happening. In view of the above, it is an object of the present invention to provide a cellulose airgel that is excellent in resilience.

  As a result of repeated studies on solving the problems, the inventors have found that cellulose aerogel has a portion with high fiber density, and that the cause is that water hardly penetrates into the portion. And it discovered that the said subject could be solved by giving a special process to the said location.

That is, the said subject is solved by the following this invention.
[1] (A) A cellulose airgel having a substantially cubic or substantially rectangular parallelepiped shape, comprising a first airgel layer having a low cellulose fiber density and a second airgel layer having a cellulose fiber density higher than that of the first airgel layer,
A step of preparing a cellulose airgel, wherein each layer is laminated so that a main surface of the layer is substantially parallel to a bottom surface of the substantially cubic or substantially rectangular parallelepiped, and one of the outermost layers is the second airgel layer; and (B) Depth x defined by the following formula on the surface of the second airgel layer constituting the outermost layer:
0.02L ≦ x ≦ 0.1L (where L is the average length of the long side and the short side of the surface on which the substantially cubic or rectangular parallelepiped cut is provided)
A plurality of cuts 1 are provided in parallel with either the long side or the short side, or a plurality of cuts 1 with a depth x are provided in parallel with either the long side or the short side, and further on the other side. Providing a plurality of incisions 2 having a depth x in parallel;
A process for producing a processed cellulose aerogel.
[2] (A1) An approximately cubic or substantially cuboid cellulose airgel comprising a first airgel layer having a low cellulose fiber density and a second airgel layer having a cellulose fiber density higher than that of the first airgel layer, Processing the cellulose airgel in which each layer is laminated so that the main surface is substantially parallel to the bottom surface of the substantially cubic or rectangular parallelepiped,
A step of preparing a one-layer cellulose airgel composed of the second airgel layer, or two or more cellulose airgels in which the second airgel layer is an outermost layer; and (B1) a one-layer cellulose airgel surface or two or more layers of cellulose. Depth x defined by the following formula on the surface of the second airgel layer constituting the outermost layer of the airgel:
0.02L ≦ x ≦ 0.1L (where L is the average length of the long side and the short side of the surface on which the substantially cubic or rectangular parallelepiped cut is provided)
A plurality of cuts 1 are provided in parallel with either the long side or the short side, or a plurality of cuts 1 with a depth x are provided in parallel with either the long side or the short side, and further on the other side. Providing a plurality of incisions 2 having a depth x in parallel;
A process for producing a processed cellulose aerogel.
[3] (A2) A substantially cube having a surface that is produced from a cellulose hydrogel obtained by culturing cellulose-producing bacteria in a medium having an air-phase medium portion present in the air phase, and is exposed to air during the culture. Or a step of preparing a substantially rectangular parallelepiped single-layer cellulose airgel, and (B2) depth x defined by the following formula on the surface:
0.02L ≦ x ≦ 0.1L (where L is the average length of the long side and the short side of the surface on which the substantially cubic or rectangular parallelepiped cut is provided)
A plurality of cuts 1 are provided in parallel with either the long side or the short side, or a plurality of cuts 1 with a depth x are provided in parallel with either the long side or the short side, and further on the other side. Providing a plurality of incisions 2 having a depth x in parallel;
A process for producing a processed cellulose aerogel.
[4] (A3) A substantially cubic body produced from a cellulose hydrogel obtained by culturing a cellulose-producing bacterium in a medium comprising an air phase medium part present in the air phase and a liquid phase medium part present in the liquid phase. Or a substantially rectangular parallelepiped cellulose airgel,
A first airgel layer having a low cellulose fiber density derived from an air phase medium part, and a second airgel layer derived from a liquid phase medium part having a cellulose fiber density higher than that of the first airgel layer, the main surface of the layer being the Each layer is laminated so as to be substantially parallel to the bottom surface of a substantially cube or a substantially rectangular parallelepiped, and one of the outermost layers is a cellulose airgel that is the first airgel layer having a surface exposed to air during the culture. A step of preparing, and (B3) depth x defined by the following formula on the surface of the first airgel layer constituting the outermost layer:
0.02L ≦ x ≦ 0.1L (where L is the average length of the long side and the short side of the surface on which the substantially cubic or rectangular parallelepiped cut is provided)
A plurality of cuts 1 are provided in parallel with either the long side or the short side, or a plurality of cuts 1 with a depth x are provided in parallel with either the long side or the short side, and further on the other side. Providing a plurality of incisions 2 having a depth x in parallel;
A process for producing a processed cellulose aerogel.
[5] A processed cellulose aerogel obtained by the method according to any one of [1] to [4].
[6] A method for producing a regenerated cellulose hydrogel, comprising absorbing the cellulose airgel according to [5] at 0 to 100 ° C.

  According to the present invention, an airgel excellent in resilience can be provided.

Overview of cellulose airgel Diagram showing processing method Diagram showing processing method SEM image of cellulose airgel The figure which shows the result of Example 1 and Comparative Example 1 The figure which shows the result of Example 2 and Comparative Example 2 The figure which shows the result of Example 3 and Comparative Example 3 SEM image of the surface of the multilayer cellulose airgel obtained in Example 4 SEM image of cut surface of multilayer cellulose airgel obtained in Example 4

  Hereinafter, the present invention will be described in detail. In the present invention, when the second airgel layer of the cellulose airgel is processed (also referred to as “first method”), the layer derived from the gas phase medium of the cellulose airgel obtained by culturing the cellulose-producing bacteria is processed. There are cases where it is applied (also referred to as “second method”). Hereinafter, the two will be described separately for the sake of simplicity. In the present invention, “to” includes values at both ends thereof.

I. First method 1. Manufacturing method of processed airgel 1-1. Process A
In step A, the cellulose airgel is a substantially cubic or substantially rectangular parallelepiped comprising a first airgel layer having a low cellulose fiber density and a second airgel layer having a cellulose fiber density higher than that of the first airgel layer. Is prepared so as to be substantially parallel to the bottom surface of the substantially cubic or substantially rectangular parallelepiped, and one of the outermost layers is the second airgel layer.

(1) Cellulose aerogel Cellulose aerogel is a gel formed by holding air in pores (holes) in a three-dimensional network structure of cellulose fibers. An example of the cellulose airgel used in the present invention is shown in FIG. FIG. 1A is a two-layer cellulose airgel, and FIG. 1B is a multilayer cellulose airgel. 10 is a first airgel layer, and 20 is a second airgel layer. In the present invention, three or more layers are referred to as a multilayer. As shown in the figure, the main surface of each layer is substantially parallel to the bottom surface of a substantially cubic or rectangular parallelepiped. “Substantially parallel” means a state according to parallel or parallel. The main surface is a main surface of each layer and is a surface on which other layers are laminated.

1) First airgel layer and second airgel layer The first airgel layer is a layer having a lower fiber density than the second airgel layer. The layer can be specified by observing the cellulose airgel with an electron microscope or the like and measuring the pore diameter. A layer having a large pore diameter is a first airgel layer, and a layer having a small pore diameter is a second airgel layer. Alternatively, the layer can be identified by the difference in transparency that occurs when the cellulose aerogel absorbs water to form a cellulose hydrogel. In this case, the layer with high transparency is a layer derived from the first airgel layer, and the layer with low transparency is a layer derived from the second airgel layer.

  The first airgel layer and the second airgel layer may be relatively different in fiber density, and the degree is not particularly limited. However, the combination of the average pore diameter of the first airgel layer: the average pore diameter of the second airgel layer is i) 0.6 to 1.0 μm: 0.1 to 0.6 μm, ii) 0.2 to 0.5 μm : 0.1 to 0.3 μm, iii) 0.9 to 5 μm: 0.3 to 0.9 μm is preferable. Cellulose aerogels such as i) can be obtained from commercially available two-layer cellulose hydrogels, and cellulose aerogels such as ii) can be obtained from commercially available multilayer cellulose hydrogels. Moreover, the cellulose airgel like iii) can be obtained from the cellulose hydrogel obtained by culture | cultivating a cellulose production bacteria in the specific temperature range which is mentioned later. The combination in iii) is more preferably 0.9 to 5 μm: 0.6 to 0.9 μm.

  In the above combination, for example, i) 0.6 to 1.0 μm: 0.1 to 0.6 μm, 0.6 μm overlaps on the notation. However, the average pore diameter of the first airgel layer is always larger than the average pore diameter of the second airgel layer, and the above description does not mean that both values are the same. The same applies to the following average fiber bundle distance.

  The average pore diameter is measured as follows. 1) The diameter of pores (holes) observed when the surface of the cellulose airgel is observed with an electron microscope or the like is measured. When the pore is not a circle, the major axis and the minor axis are measured, and the average is taken as the pore diameter. 2) The pore diameter is measured for a plurality of pores and averaged.

  The fiber density in the airgel layer is also affected by the average distance between fiber bundles measured as follows. Usually, a cellulose hydrogel is produced in the form of a thin sheet-like cellulose hydrogel, and then the sheet-like gel is laminated to form a cellulose hydrogel having a certain size. As described above, when a cellulose hydrogel is produced using cellulose-producing bacteria, the sheet-like gel is usually laminated on the liquid phase side in parallel to the liquid surface. Therefore, in the cellulose hydrogel, fiber bundles in which cellulose fibers are gathered are present in layers. The shortest distance between the fiber bundles is referred to as an inter-fiber bundle distance, and an average of the inter-fiber bundle distances obtained by measuring and averaging the inter-fiber bundle distances for a plurality of fiber bundles. The average fiber bundle distance is an index of fiber density, and the fiber density decreases as the average fiber bundle distance increases. The average distance between fiber bundles in the first airgel layer and the second airgel layer is 5 to 10 μm: 3 to 5 μm in the case of i), and 3.5 to 5 μm: 3 to 4 μm in the case of ii). In this case, 3.5 to 5 μm: 0.1 μm or more and less than 3 μm is preferable. The average fiber bundle distance is measured as follows. 1) A cellulose airgel is cut | disconnected perpendicularly | vertically to a lamination surface using a cutter etc. 2) The cut surface is observed with an electron microscope or the like, and the shortest distance between the fiber bundles existing in layers is measured. 3) The distance is measured and averaged for a plurality of fiber bundles.

  In addition, the fiber density can also be evaluated by a dry mass method in which a dry mass R per unit mass of cellulose hydrogel is calculated. Specifically, R (%) is defined by D / W × 100. D is the mass when the hydrogel is dried, and W is the mass when the hydrogel is saturated with water. The hydrogel drying is a state in which the hydrogel is completely dried to become an airgel. Saturated water absorption is the time when water absorption is saturated when gel is absorbed in a normal state (room temperature and atmospheric pressure). If D is a mass D1 when the first airgel layer is dried and W is a mass W1 obtained by saturated water absorption of the first airgel layer, R of the first airgel layer, that is, R1 is obtained. Similarly, R of the second airgel layer, that is, R2 is also obtained.

A specific method for obtaining W and D will be described by taking the case of obtaining W1 and D1 as an example.
1) The first airgel layer and the second airgel layer are specified by the method described above.
2) A sample is taken from the first airgel layer.
3) After soaking the sample in water at room temperature overnight, the mass is weighed to determine the saturated water absorption mass W1.
4) After drying the sample obtained in 3), the mass is weighed to determine the dry mass D1.

  The weighing is preferably measured to the order of 0.1 mg using a precision balance. Drying may be performed by hot air drying, freeze drying, natural drying, or the like, but hot air drying is preferable in consideration of drying efficiency. When dividing a 1st airgel layer and a 2nd airgel layer, it is preferable to cut | disconnect using a cutter etc. so that a gel may not be crushed.

The larger R is the second airgel layer (high density layer), and the smaller R is the first airgel layer (low density layer).
Preferred R1: R2 is
In the case of i), “0.1 or more and less than 0.42”: “0.42 to 1.5”
In the case of the above ii), “0.34 or more and less than 0.50”: “0.50 to 1.5”
In the case of iii), “0.05 or more and less than 0.50”: “0.50 to 1.2”
It is.

  In the multilayer cellulose airgel used in the present invention, one of the outermost layers is a second airgel layer. By making one of the outermost layers a second airgel layer having a high fiber density, the strength of the cellulose airgel can be increased, and the shape stability of the restored cellulose hydrogel can also be improved.

2) Shape and dimension The cellulose airgel used in the present invention is substantially cubic or rectangular parallelepiped. A substantially cube is a shape that conforms to a cube. For example, the substantially cube includes a shape in which the angle formed between the surfaces is slightly deviated from a right angle or rounded, and a shape in which each side is substantially parallel. The same applies to a substantially rectangular parallelepiped. The substantially rectangular parallelepiped includes a plate-like shape in which the length of one side is shorter than the other side. The plate shape is thicker than the aforementioned sheet obtained by culturing bacteria and is different from the sheet.

  Although the dimension of the cellulose airgel used by this invention is not specifically limited, When handling property etc. are considered, it is preferable that the length of one side is 0.5-2.0 cm, and it is 1.0-1.8 cm. Is more preferable.

(2) Preparation of cellulose aerogel It is preferable to prepare a cellulose aerogel by preparing a cellulose hydrogel and drying it. Hereinafter, the preparation method will be described.

1) Cellulose hydrogel Cellulose hydrogel is a gel formed by holding water in pores in a three-dimensional network structure of cellulose fibers. A cellulose hydrogel having the same structure as that shown in FIG. 1 may be selected. Cellulose hydrogel having the same structure as FIG. 1 (a) is obtained by culturing cellulose-producing bacteria in a medium comprising a liquid phase medium part present in the liquid phase and an air phase medium part present in the air phase, It can be produced by forming a first hydrogel layer having a low fiber density derived from the liquid phase medium portion and a second hydrogel layer having a high fiber density derived from the air phase medium. Since acetic acid bacteria are aerobic bacteria, they actively produce cellulose in the air phase medium. For this reason, a layer with high fiber density is obtained in an air phase culture medium. Normally, the gel stretches vertically downward (in the direction of the liquid phase medium) and increases in thickness. However, in the liquid phase medium, the oxygen concentration is low, and because of the accumulation of waste products and the lack of nutrients as they are cultured, etc. Fungus activity and growth is reduced. Therefore, a layer with low fiber density is obtained in the liquid phase medium. In addition, since the air phase medium is poor in water, there is not much water between the produced cellulose fibers. This reduces the distance between the cellulose fibers and results in a higher fiber density in the resulting layer. Conversely, in a liquid phase medium rich in moisture, a lower fiber density layer is formed. Known cellulose-producing bacteria can be used. For example, strains of ATCC 23769, ATCC 10245, ATCC 35959, ATCC 10821, ATCC 7000017, Acetobacter xylinum FF-88 (FERM BP-4407) can be used. A well-known thing can also be used for a culture medium, for example, agar-like solid culture medium, a liquid culture medium (culture solution), etc. Examples of the culture solution include a culture solution containing corn steep liquor and fructose as main components and having a pH adjusted to about 5. The culture is preferably stationary culture.

  A cellulose hydrogel can be obtained by subjecting the cultured medium to a known post-treatment. For example, a cellulose hydrogel can be obtained by taking out the product from the medium and then removing the bacteria by washing with water and alkali treatment. Examples of the cellulose hydrogel produced in this manner include “Fujikko Natadokoco” manufactured by Fujikko Co., Ltd., “Zero Calorie Jelly of Delicious Fruit Juice” manufactured by Tarami Co., Ltd., “Namakokko” manufactured by Wakayama Sangyo Co., Ltd., etc. It is done. From this cellulose hydrogel, a cellulose airgel having a combination of i) average pore diameter, cut surface average interlayer distance, and R can be prepared.

  Moreover, the cellulose hydrogel which has the same structure as FIG.1 (b) is a high-temperature culture | cultivation which cultivates a cellulose producing microbe at 23-40 degreeC, and forms the 1st hydrogel layer with low fiber density, and 10 a cellulose producing microbe. The low-temperature culture in which the second hydrogel layer having a high fiber density is formed by culturing at a temperature of not lower than 23 ° C. and lower than 23 ° C. can be produced alternately. Cellulose-producing bacteria produce cellulose hydrogel by culturing at high temperature (23 to 40 ° C.). Considering easiness of temperature setting, cost and the like, the culture temperature is preferably 23 to 33 ° C, more preferably 25 to 32 ° C, and further preferably 26 to 31 ° C. Moreover, although culture | cultivation time may be suitably adjusted in order to obtain the thickness of a desired layer, 12 to 60 days are preferable, 3 to 22 days are preferable and 4 to 10 days are more preferable. At this time, the culture is preferably stationary culture.

  A second hydrogel layer having a fiber density higher than that of the first hydrogel layer is formed by culturing cellulose-producing bacteria at a low temperature (10 ° C. or more and less than 23 ° C.). In general, the higher the temperature, the higher the activity of the bacteria, so that the fiber density of the resulting layer is also considered to be high. In this method, a layer having a low fiber density is obtained by culturing at a low temperature. Although this reason is not limited, it thinks as follows. Generally, when cellulose-producing bacteria are cultured, the bacteria move randomly while exhaling cellulose. When the culture temperature is appropriate, the bacteria actively move and grow. For this reason, although the quantity of the cellulose fiber produced is large, since the movement distance of bacteria is also large, the fiber density per unit volume becomes low and a low fiber density layer is obtained. However, when the culture temperature is low, the motility of the bacterium is reduced, so that the range of the bacterium's behavior is narrowed, and the bacterium grows without changing its position so much. For this reason, bacteria grow in a certain limited place and produce cellulose, so that the fiber density per unit volume is increased and a high fiber density layer is obtained.

  In addition, by culturing at a low temperature of 10 ° C. or more and less than 23 ° C., the activity of acetic acid bacteria is not lowered, but the activity of other bacteria is lowered, so that impurities in the gel can be reduced or the medium is less likely to corrode. There are advantages.

  In order to express these effects more efficiently, the culture temperature in the low temperature culture is preferably 15 to 20 ° C, more preferably 17 to 19 ° C. The culture time is as described in the high temperature culture.

  By alternately performing the high temperature culture and the low temperature culture, the first hydrogel layer and the second hydrogel layer are alternately stacked. In order to produce efficiently, high temperature culture and low temperature culture are preferably performed continuously. In addition, if the outermost layer of the obtained cellulose hydrogel is a second hydrogel layer having a high fiber density, the strength and shape stability of the gel will be good, so low temperature culture is performed first, and then both cultures are performed. It is more preferable to repeat and finally carry out the low temperature culture.

  In this method, the thicknesses of the first hydrogel layer and the second hydrogel layer can be controlled as desired. Generally, the thickness of each layer is preferably 1 to 8 mm, and more preferably 2 to 4 mm. From this cellulose hydrogel, a cellulose aerogel having a combination of the average pore diameter of iii), the average distance between the cut surfaces, and R can be prepared.

  Moreover, the cellulose hydrogel which has the same structure as FIG.1 (b) can be obtained as Nata de Coco contained in "Halohalo" by Ministop Co., Ltd., Dole Co., Ltd. "Nata de Coco wrapping (light)". These commercially available cellulose hydrogels can be produced by repeating culture at different temperatures, but differ from the above-described method in terms of culture temperature. That is, these commercially available multilayer cellulose hydrogels are produced in a natural environment in Southeast Asian regions such as Thailand and the Philippines. In this case, bacteria are highly active in high temperature (29-32 ° C.) culture during the day and a layer with high fiber density is produced, and in low temperature culture at night (24-25 ° C.), bacteria are low in activity and low in fiber density. Produced. From this cellulose hydrogel, a cellulose aerogel having a combination of the above average pore diameter, the cut surface average interlayer distance, and R of ii) can be prepared.

  Such a multilayer cellulose hydrogel may be formed such that the outermost layer becomes the second hydrogel layer by cutting between layers or layers.

2) Pre-drying treatment As described above, when the cellulose hydrogel is dried, a cellulose aerogel is obtained. However, when the cellulose hydrogel is simply dried, problems such as cracking of the cellulose hydrogel may occur. The reason for this is that the water present inside the cellulose hydrogel may undergo volume expansion during drying, and the strain generated thereby destroys the surface of the cellulose hydrogel that has already been dried and reduced in strength. it is conceivable that. In order to solve this problem, the inventors have developed a method of coating the surface of cellulose hydrogel with water before drying (see Japanese Patent Application No. 2010-020455). Therefore, it is preferable to perform drying in the same manner in the present invention.

  In the present invention, instead of coating the surface of the cellulose hydrogel with water, the cellulose hydrogel may be immersed in an aqueous solution containing a disaccharide such as maltose (maltose). When such an aqueous solution is used, not only the breakage of the cellulose hydrogel during drying is prevented, but also the restoration rate and texture when obtaining the restored cellulose hydrogel are improved. Maltose is a disaccharide in which two α-glucoses are linked by α1-4 glycosidic bonds. In addition, sucrose (sucrose) or lactose (lactose) may be used as the disaccharide. The concentration range is preferably 0.001 to 1% by mass, more preferably 0.01 to 0.5% by mass, further preferably 0.1 to 0.5% by mass, and more preferably 0.2 to 0.3% by mass. Further preferred is 0.22 to 0.27% by mass.

  Since maltose is contained as a main component in the starch syrup, in the present invention, it is preferable to use an aqueous solution containing starch syrup as the aqueous solution containing maltose. Mizuame is an edible sweetener containing glucose and dextrin in addition to the main component maltose. Using water candy can improve the surface gloss. The concentration of the syrup aqueous solution is adjusted so that the concentration of maltose contained in the aqueous solution falls within the above range. However, since other components are contained in the starch candy, it becomes difficult to penetrate into the gel when the concentration of the starch candy increases. Therefore, from this viewpoint, the starch candy concentration is preferably 0.01 to 0.25% by mass.

  Moreover, as an aqueous solution containing maltose, an aqueous solution obtained by further diluting 10 to 1000 times an aqueous solution obtained by dissolving 2 to 10 g of starch syrup and 10 to 20 mL of gelatin in 30 mL of water may be used. Gelatin is an induced protein obtained by boiling collagen in water.

By immersing the cellulose hydrogel in the aqueous solution for 1 to 24 hours, the aqueous solution penetrates into the cellulose hydrogel. The temperature during immersion is preferably room temperature.
The reason why the texture and appearance of the regenerated cellulose hydrogel are improved by using such an aqueous solution is not limited, but is presumed as follows. Since disaccharides such as maltose have a chemical structure similar to cellulose and have a low molecular weight, they easily penetrate into the cellulose hydrogel. And since disaccharide has good affinity with a cellulose fiber, it exists between cellulose fibers also at the time of drying. For this reason, if there is no maltose, the cellulose fibers are strongly bound to each other by drying, but the fact that the cellulose fibers are strongly bound to each other by the disaccharide is reduced. As a result, when the water is absorbed again to obtain the restored cellulose hydrogel, the network structure of the original cellulose fiber is easily reproduced. Further, when the disaccharide is infiltrated into the cellulose hydrogel, an aqueous solution having a relatively low concentration is used in the present invention. Since the concentration is low, capillary action is likely to occur and the disaccharide is more easily penetrated into the cellulose hydrogel.

  In addition, gelatin used in combination with disaccharides is considered to act to reinforce the outer shell of cellulose hydrogel because of its high molecular weight. However, since gelatin is also used as an aqueous solution having a relatively low concentration as described above, the cellulose hydrogel is not completely coated, so that it is considered that the texture is not lowered.

  In addition, an aqueous solution containing agar may be used instead of the aqueous solution containing disaccharides. Agar is obtained by freezing and drying mucus from red algae.

3) Drying Examples of the drying method include freeze drying, vacuum drying, supercritical liquid drying, and subcritical liquid drying. Freeze-drying is drying performed by freezing water and sublimating. In the present invention, it is preferable to freeze-dry at a low temperature of 50 ° C. or lower under reduced pressure in order to avoid gel degradation. Specifically, it is preferable to freeze-dry at a temperature of −50 to −40 ° C. under a pressure of 15 to 25 Pa.

Vacuum drying is a drying that removes water under reduced pressure. In this invention, it is preferable to dry at the temperature of -40-100 degreeC under the pressure of 25 Pa-0.1 MPa.
Supercritical liquid drying is a method in which a solvent solution is heated by being supercritical or higher and then dried by gently discharging solvent vapor out of the system. Subcritical liquid drying is a method in which a solvent solution is brought into a subcritical state where the temperature and pressure are slightly lower than those of the supercritical state, and the solvent vapor is discharged out of the system.

  In the present invention, it is preferable to replace water in the cellulose hydrogel as it is or with ethanol, methanol, carbon dioxide or the like, and dry water or ethanol with supercritical liquid drying or subcritical liquid drying. The critical temperature and pressure are as shown below. For example, when ethanol is used, supercritical liquid drying can be performed at 6.38 MPa and 243 ° C.

In the case of drying as it is without replacing water, it is preferable to carry out in a subcritical state because cellulose may be decomposed in a supercritical state. For example, it is preferable to set the temperature to 100 ° C. or higher at atmospheric pressure and to a temperature of 374.15 ° C. (647.30 K) or lower at 22.12 MPa.
Carbon dioxide: 304.1 (K), 7.38 (MPa)
Water: 647.3 (K), 22.12 (MPa)
Methanol: 512.6 (K), 8.09 (MPa)
Ethanol: 513.9 (K), 6.14 (MPa)
Acetone: 508.1 (K), 4.70 (MPa)
Although drying time can be suitably adjusted with a dry state, it is preferable to carry out for about 24 to 72 hours.

  In addition, instead of coating the cellulose hydrogel, 30 to 50% by volume of the cellulose hydrogel may be subjected to drying in a state of being immersed in water or the aqueous solution.

1-2. Process A1
In the present invention, in addition to the above, a one-layer cellulose airgel composed of a second airgel layer prepared by the method described later, or two or more cellulose airgels in which the second airgel layer is the outermost layer is processed in the next step. It may be used as a target.

  These cellulose airgels can be produced by preparing two or more layers of cellulose airgel and processing the cellulose airgel. Examples of processing in this case include polishing, cutting, and cutting. Taking a cellulose airgel consisting only of the second airgel layer as an example, a two-layer cellulose airgel is prepared, and the interface between the first airgel layer and the second airgel layer is cut, or the inside of the second airgel layer is substantially parallel to the laminated surface. If it cut | disconnects, the 1 layer cellulose airgel which consists of a 2nd airgel layer will be obtained. Moreover, the cellulose hydrogel of two or more layers is prepared, the said cellulose hydrogel is cut | disconnected with a cutter etc., and the 1 layer cellulose hydrogel which consists of a 2nd hydrogel layer (it becomes a 2nd airgel layer when dried), If the said cellulose hydrogel is dried by the above-mentioned method, the 1 layer cellulose airgel which consists of a 2nd airgel layer will be obtained. The same applies to the cellulose airgel in which the second airgel layer is the outermost layer.

1-3. Process B and process B1
(1) Incision processing In step B and step B1, i) the notch 1 having a depth x on the surface of the single-layer cellulose airgel or the second airgel layer constituting the outermost layer, the long side and the short side Or ii) a plurality of cuts 1 with a depth x parallel to either one of the long side or the short side, and a cut with a depth x parallel to the other side A plurality of inserts 2 are provided. The process of i) is also called “parallel cut”, and the process of ii) is also called “cross cut”. FIG. 2 shows a cellulose airgel subjected to such processing. FIG. 2A shows a cellulose aerogel subjected to parallel cut, and FIG. 2B shows a cellulose aerogel subjected to cross cut. In FIG. 2, reference numeral 30 denotes a cut 1, and s <b> 1 is a side 1 (length is L <b> 1) parallel to the cut 1. Reference numeral 32 denotes a cut 2, and s 2 denotes a side 2 (length is L 2) parallel to the cut 2. In FIG. 2, the display of the first airgel layer and the second airgel layer is omitted.

  The depth x of the cut is the average length of the long side and the short side of the surface where the cut of the substantially cube or the substantially rectangular parallelepiped (hereinafter also referred to as “substantially cube” or the like) is provided. When the short side) / 2), the length is 0.02L to 0.1L. Specifically, about 0.5-1 mm is preferable.

  Moreover, it is preferable that the minimum angle made by the depth direction of a notch and the surface which provides a notch is 15-90 degrees. If the angle is about 15 to 30 °, the cut may be provided without damaging the cellulose airgel.

  Thus, the cellulose airgel excellent in the recoverability is obtained by processing the surface of the second airgel layer constituting the outermost layer. The reason for this is not limited, but the second airgel layer has a high fiber density, so the pore diameter is small and water does not easily permeate. However, it is presumed that the above-described processing facilitates water permeation. In order to exhibit this effect more fully, the length of the cut 1 is preferably 70 to 100% of the length L1 of the side 1 parallel to the cut. Moreover, as for the space | interval of the adjacent notches 1, L1 / 5-L1 / 100 are preferable. Specifically, about 5 to 100 are preferably provided on one surface. In this case, it is preferable that the notches 1 are provided at unequal intervals as much as possible. The same applies to the cut 2. When the cuts are provided at regular intervals so as to have periodicity, the surface may be difficult to wet due to the so-called lotus leaf effect, and water may not easily penetrate.

  The means for providing the cut is not limited. For example, a notch may be provided using a cutter or a razor. Further, this cutting process may be performed on other five surfaces such as a substantially cube.

(2) Through perforation processing In addition to the above-described cutting processing, the cellulose airgel may be subjected to through perforation processing. The through drilling process is to provide a hole that passes through the center of a surface such as a substantially cube and penetrates to the center of the opposing surface. This hole makes it easier for water to penetrate into the cellulose airgel. FIG. 3 (a) shows a cellulose airgel that has been perforated. In FIG. 3A, reference numeral 40 denotes a through hole.

  For the perforation, a known material may be used. For example, it is preferable to use a needle having a diameter of 0.3 to 1 mm. Further, the through drilling process may be performed on six surfaces such as a substantially cube.

(3) Non-penetrating perforation processing In addition to the above-described cutting process, the cellulose airgel may be subjected to non-penetrating perforation processing. The non-penetrating drilling process is to provide a hole that does not penetrate from a surface such as a substantially cubic body to a facing surface. FIG. 3 (b) shows a cellulose airgel that has been perforated. In FIG. 3B, reference numeral 42 denotes a non-through hole. The minimum angle formed by the depth direction of the non-through hole 42 and the surface where the non-through hole 42 is provided is preferably 75 to 90 °.

  The depth of the hole is preferably 10 to 70% of the distance M between the facing surfaces. The number of holes not penetrating is preferably about 2 to 20. The non-through drilling process is preferably performed using, for example, a needle having a diameter of 0.3 to 1 mm. Further, the non-penetrating drilling process may be performed on six surfaces such as a substantially cube.

(4) Deep cutting process In addition to the said cutting process, you may give a deep cutting process to a cellulose airgel. Deep cutting is a deep cutting with a depth of 0.5M to 0.7M (where M is the distance between the opposing surfaces) on two opposing faces such as a substantially cube, where both deep cuttings are cellulose. It is to provide one by one so as not to bond in the airgel. This deep cutting makes it easier for water to penetrate into the cellulose airgel. FIG. 3C shows a cellulose airgel that has been deep-cut. In FIG. 3C, 44 is a deep cut. In this case, the minimum angle formed by the depth direction of the deep cut and the surface on which the deep cut is provided is preferably 75 to 90 °, and more preferably 85 to 90 °. Further, the position on the z-axis at which the deep cut is provided is preferably 0.25Z to 0.33Z, where Z is the length of the side (s3) in the z-axis direction in FIG.

  If the width of the deep cut (the length in the y-axis direction in FIG. 3 (c)) is excessively long, the strength of the cellulose airgel may be reduced, so the width of the cut is the short side of the surface on which the cut is provided. And 50 to 70% of the average length L of the long side is preferable. The means for providing the deep cutting is as described in the cutting process.

(5) Combination of the processing The processing described in (1) to (4) may be arbitrarily combined. In particular, when the processes of (1) to (3) are performed on six surfaces such as a substantially cubic body and the process of (4) is performed on two opposing surfaces, a cellulose aerogel having extremely excellent recoverability can be obtained. Therefore, it is preferable. This processing is sometimes referred to as “S processing”.

(6) Significance of processing cellulose aerogel In the present invention, cellulose aerogel, that is, a gel in a dry state is processed. When the cellulose hydrogel is processed and dried, the cellulose fibers in the vicinity of the processed part are excessively adhered during drying. Adhering cellulose fibers are not easily loosened at the time of water absorption, so that the effect of improving the water absorption rate by processing is offset, and satisfactory recoverability cannot be obtained. However, when the cellulose gel after drying is processed, the cellulose fibers in the vicinity of the processed portion do not excessively adhere to each other, so that excellent resilience can be achieved.

2. Processed Cellulose Airgel According to the production method of the present invention, a cellulose airgel having a substantially cubic or substantially rectangular parallelepiped shape having a first airgel layer and a second airgel layer, wherein the main surface of the layer is substantially the bottom surface of the substantially cubic or substantially rectangular parallelepiped. Each layer is laminated so as to be parallel, and one of the outermost layers is the second airgel layer, and a processed cellulose airgel having a specific notch or the like is obtained.

3. Method for Producing Restored Hydrogel (1) Restored Method The processed cellulose aerogel of the present invention can be made into a restored hydrogel by absorbing water. The temperature at this time is preferably 0 to 100 ° C. Water absorption can be performed by immersing the processed cellulose airgel of the present invention in water or an aqueous solution at the above temperature. Examples of the aqueous solution include an aqueous sugar solution, an aqueous solution containing inorganic ions (mineral components), carbonated water, and broth.

  In the conventional cellulose airgel, it was necessary to immerse in hot water in order to quickly restore the hydrogel. However, the processed cellulose airgel of the present invention is cold water (preferably 4 to 30 ° C., more preferably 10 to 10 ° C.). 30 ° C) can be easily restored.

  The soaking time can be selected from 1 minute to 24 hours, but the processed cellulose airgel of the present invention can achieve a high recovery rate even in the case of soaking for about 3 minutes.

(2) Restorability Restorability is an index representing how close the shape and properties of the restored cellulose hydrogel are to the original cellulose hydrogel. Restorability can be evaluated using the restoration rate. The restoration rate is defined by the mass of the restored cellulose hydrogel / the mass of the cellulose airgel. The processed cellulose airgel of the present invention preferably has a recovery rate (also referred to as “3-minute recovery rate”) of 60% or more when immersed in water for 3 minutes.

  The restorability can also be evaluated by visually observing the white residue of the restored cellulose hydrogel. The “white residue” is a portion that appears white because water does not penetrate.

II. Second Method The second method is characterized in that a layer derived from a gas phase medium of cellulose aerogel obtained by culturing cellulose-producing bacteria is processed.

1. 1. Manufacturing method of processed airgel 1-1. Process A2
Step A2 is produced from a cellulose hydrogel obtained by culturing a cellulose-producing bacterium in a medium having an air phase medium portion present in the air phase, and has a substantially cubic shape having a surface exposed to air during the culturing or An approximately rectangular parallelepiped single-layer cellulose airgel is prepared. Such a cellulose aerogel is, for example, the above-mentioned I 1-1. As described in, first, cellulose-producing bacteria are cultured in a medium comprising an air phase medium part present in the air phase and a liquid phase medium part present in the liquid phase, and a layer derived from the air phase medium, A cellulose hydrogel having a medium-derived layer is prepared. Next, the cellulose hydrogel is dried by the above-described method to produce a cellulose aerogel, and the interface between the layer derived from the air phase medium and the layer derived from the liquid phase medium, or the layer derived from the air phase medium is cut. A one-layer cellulose airgel is produced. In this case, it processes so that the said cellulose airgel may have the surface exposed to the air at the time of culture | cultivation.

  In this method, since the cellulose airgel stretches toward the liquid phase surface, the cellulose airgel portion produced first is usually exposed to air. Therefore, the surface exposed to air at the time of culture is a surface obtained by drying the surface of the cellulose hydrogel that was first produced and exposed to air.

  The layer derived from the air phase medium may be either the first airgel layer or the second airgel layer described above.

1-2. Process A3
In step A3, the cellulose-producing bacterium is produced from a cellulose hydrogel obtained by culturing a cellulose-producing bacterium in a medium comprising an air phase medium part present in the air phase and a liquid phase medium part present in the liquid phase. A cuboid cellulose airgel, comprising a first airgel layer derived from a gas phase culture medium part and a second airgel layer derived from a liquid phase culture medium part, wherein a main surface of the layer is substantially parallel to a bottom surface of the substantially cubic or substantially cuboid. The cellulose airgel is prepared, in which the layers are laminated so that one of the outermost layers is the first airgel layer including the surface exposed to air during the culture.

  Such a cellulose aerogel is the same as in 1-1 of the above I. As described above, the cellulose-producing bacterium can be prepared by culturing in a medium comprising an air phase medium part existing in the air phase and a liquid phase medium part existing in the liquid phase. However, in order to obtain the second airgel layer (high density layer) derived from the liquid phase medium and the first airgel layer (low density layer) derived from the air phase medium, the culture temperature is initially set to a high temperature (23 ° C. to 40 ° C.). It is necessary that the temperature be lower than 10 ° C. and lower than 23 ° C. later. As described above, since a high-density layer is produced by culturing at a low temperature (10 ° C. or more and less than 23 ° C.), cellulose hydro having a second airgel layer derived from a liquid phase medium and a first airgel layer derived from an air phase medium. A gel is obtained.

  Cellulose aerogel can be prepared by drying the cellulose hydrogel thus obtained as described in I above.

1-3. Process B2
In the step B2, the surface exposed to the air during the cultivation of the cellulose airgel obtained in the step A2 has a 1-3. Apply the processing as described in. Since the surface exposed to air at the time of culturing has been exposed to air from the time of cellulose hydrogel production, there are portions where the fibers are locally adhered to the surface layer portion. Water does not easily penetrate into the portion, and such a cellulose airgel has low restorability. Therefore, in the present invention, a restored cellulose hydrogel having excellent restoration properties is obtained by performing the above-described processing on the portion.

1-4. Process B3
In the step B3, the first airgel layer (low density layer) that is present in the outermost layer of the cellulose aerogel obtained in the step A3 and exposed to air during the culture is added to the 1-3. Apply the processing as described in. In general, the first airgel layer has better water permeability than the second airgel layer. However, since the first airgel layer derived from the air phase medium has been exposed to air from the time of cellulose hydrogel production, there is a portion where the fibers are locally adhered to the surface layer portion. Accordingly, water hardly penetrates into the portion, and such a cellulose airgel has low restorability. Therefore, in the present invention, a regenerated cellulose hydrogel having excellent recoverability is obtained by processing the first airgel layer derived from the air phase medium.

2. Processed cellulose aerogel According to the present invention, a substantially cubic or substantially rectangular parallelepiped having a surface that is produced from a cellulose hydrogel obtained by culturing in a medium having an air phase medium portion present in the air phase and exposed to air during the culturing. It is a 1 layer cellulose airgel, Comprising: The process cellulose aerogel provided with the specific cut etc. in the said surface can be manufactured.

  Further, according to the present invention, a substantially cubic body produced from a cellulose hydrogel obtained by culturing a cellulose-producing bacterium in a medium comprising an air phase medium part present in the air phase and a liquid phase medium part present in the liquid phase. Or a substantially rectangular parallelepiped cellulose airgel, comprising a first airgel layer derived from a gas phase culture medium part and a second airgel layer derived from a liquid phase culture medium part, the main surface of the layer being on the bottom surface of the substantially cubic or substantially rectangular parallelepiped Each layer is laminated so as to be substantially parallel, and one of the outermost layers is the first airgel layer having a surface that has been exposed to air during culture, and a specific notch or the like is provided in the first airgel layer. A processed cellulose aerogel can be produced. Typically, this processed cellulose aerogel is a two-layer cellulose aerogel.

  I-2. In the method described in the above item, if the cellulose airgel is used, a regenerated cellulose hydrogel can be produced.

[Example 1] Restorability of two-layer cellulose airgel <Example 1-1>
A cubic cellulose hydrogel (Natadecoko manufactured by Tarami Co., Ltd.) having the same structure as that shown in FIG. 1A and having a side of 1.4 cm is prepared, thoroughly washed with water, and then heated with hot water at 100 ° C. Washed twice. The cellulose hydrogel is a cellulose hydrogel obtained by culturing a cellulose-producing bacterium in a medium comprising a liquid phase medium part and an air phase medium part, and has a low fiber density derived from the liquid phase medium part. The second hydrogel layer having a high fiber density derived from the hydrogel layer and the air phase medium was provided. Next, the cellulose hydrogel was immersed in water at room temperature overnight. The cellulose hydrogel after immersion was freeze-dried at −50 to −40 ° C. and 15 to 25 Pa for 48 hours using a freeze dryer (Tokyo Science Instruments Co., Ltd., FDU-1200). The cellulose aerogel shown was obtained.

  The thickness of both the first airgel layer and the second airgel layer of the cellulose airgel was 70 mm. About each layer, the average pore diameter and the average interfiber bundle distance were measured by the above-mentioned method. As a result, the average pore diameter and average fiber bundle distance of the first airgel layer were 1 μm and 8 μm, and the average pore diameter and average fiber bundle distance of the second airgel layer were 0.2 μm and 5 μm. R1 was 0.29% and R2 was 0.52%.

FIG. 4 shows scanning electron microscope images (JSM-5200, manufactured by JEOL Ltd.) of the first airgel layer and the second airgel layer of the cellulose airgel.
The surface of the second airgel layer was subjected to the above-described cross-cut processing using a razor (manufactured by Kaiken Razor Co., Ltd., long pattern gold alpha). The depth of cut was 0.5 to 1 mm, and the number of cuts was 100 per side (50 cuts 1 and 50 cuts 2). The minimum angle formed by the depth direction of the cuts 1 and 2 and the surface provided with the cuts was about 90 °.

  The processed cellulose aerogel was fully immersed in water at 25 ° C., the restoration rate was measured every fixed time, and the remaining white state was visually observed. As described above, the restoration rate was obtained from the mass of the restored cellulose hydrogel / the mass of the cellulose airgel. The mass was measured using a chemical balance (Cal Zeiss).

The white residue was observed on the surface and inside of the gel, and the following criteria A: almost no white residue B: little white residue C: much white residue D: much white residue E: most of the white residue was evaluated .

<Example 1-2>
Using the same lot of cellulose hydrogel, in the same manner as in Example 1-1, a cellulose airgel having six surfaces subjected to cross-cut processing was prepared, and the restorability was evaluated.

[Comparative Example 1] Restorability of two-layer cellulose airgel <Comparative Example 1-1>
A cellulose airgel was prepared in the same manner as in Example 1-1 except that the same lot of cellulose hydrogel was not processed, and the restorability was evaluated.

<Comparative Example 1-2>
A cellulose aerogel was prepared in the same manner as in Example 1-1, except that the cellulose aerogel of the same lot was used, and the first aerogel layer was subjected to crosscut processing instead of the second aerogel layer, and restorability was evaluated. .

<Comparative Example 1-3>
A cellulose hydrogel of the same lot as that of Example 1-1 was prepared. The entire cross-section of Example 1-1 was applied to the entire surface of the cellulose hydrogel. The processed cellulose hydrogel was immersed in water overnight at room temperature. The processed cellulose hydrogel after immersion was freeze-dried in the same manner as in Example 1-1 to prepare a cellulose airgel, and the restorability was evaluated.

  These results are shown in Table 1 and FIG.

  As shown in Table 1, the cellulose aerogels of Examples 1-1 to 1-2 in which the cutting process was performed on the surface of the second airgel layer (high fiber density layer) constituting the outermost layer had a high restoration rate, And there was little white residue.

  The restorability of the cellulose airgel of Comparative Example 1-3 obtained by processing the surface of the second hydrogel layer (the high fiber density layer in the hydrogel) constituting the outermost layer and then drying it is shown in Example 1- It did not reach the recoverability of the cellulose airgel of 1-2.

[Example 2] Restorability of two-layer cellulose airgel <Example 2-1>
A cellulose hydrogel of a different lot from that of Example 1 (Natadecoko, manufactured by Tarami Co., Ltd.) was prepared, and a cellulose airgel was obtained in the same manner as Example 1-1. The six surfaces of the cellulose airgel were subjected to a cross-cut process in the same manner as in Example 1-1, and a processed cellulose airgel was obtained and evaluated. R1 was 0.29% and R2 was 0.52%.

<Example 2-2>
A cellulose aerogel having the same lot as that of Example 2-1 and crosscut processing on six surfaces was prepared in the same manner. On the six surfaces of the cellulose airgel, the above-mentioned through-hole drilling process is performed using a sewing needle (diameter 0.71 mm), and further, the above-mentioned non-through-hole drilling process is performed using a sewing needle (diameter 0.53 mm). did. The number of non-through holes was 20 per surface, and the depth was 1 to 5 mm. The minimum angle formed by the depth direction of the non-through hole and the surface provided with the hole was about 90 °. In the same manner as in Example 2-1, the restorability of the processed cellulose airgel was evaluated.

<Example 2-3>
Using the same lot of cellulose hydrogel as in Example 2-1, a cellulose aerogel having six surfaces subjected to cross-cut processing, through-hole drilling, and non-through-hole drilling was prepared in the same manner as in Example 2-2. . As shown in FIG. 3 (c), using a scalpel (Disposmes No. 10 manufactured by AS ONE Corporation) on the two opposing surfaces of the cellulose airgel, one deep cut having a depth of 8 mm and a length of 14 mm is provided. The “S-processed” cellulose airgel was obtained perpendicular to the surface. The shortest distance between the deep-cut main surface and the cellulose airgel surface parallel to the main surface was 0.3 mm. In the same manner as in Example 2-1, the restorability of the processed cellulose airgel was evaluated.

[Comparative Example 2] Restorability of a two-layer cellulose airgel <Comparative Example 2-1>
Restorability was evaluated in the same manner as in Example 2-1, except that cellulose hydrogel of the same lot as in Example 2-1 was used and the cellulose aerogel was not processed.

<Comparative Example 2-2>
A cellulose aerogel processed in the same manner as in Example 2-2 except that the cellulose hydrogel of the same lot as in Example 2-1 was used and cross-cut processing was not performed. The cellulose aerogel) was prepared and the restorability was evaluated.

  These results are shown in Table 2 and FIG.

  As shown in Table 1, the cellulose aerogels of Examples 2-1 to 2-3 in which cutting was performed on the surface of the second airgel layer (high fiber density layer) constituting the outermost layer had a high restoration rate, And there was little white residue.

[Example 3] Restorability of a cellulose aerogel having a multilayer structure A cuboid cellulose hydrogel having a multilayer structure as shown in Fig. 1 (b) and having a vertical and horizontal side of 1.4 cm and a height of 1.7 cm. Nata de Coco included in “Halohalo” manufactured by Ministop Co., Ltd.) was prepared. Impurities were removed from the Nata de Coco, and after sufficient washing with water, it was washed 10 times with hot water at 100 ° C. The nata de coco was dried in the same manner as in Example 1 to obtain a cellulose airgel.

  The cellulose airgel is formed of two first airgel layers and three second airgel layers. Each layer has a thickness of about 3.1 mm for the first airgel layer and about 3.6 mm for the second airgel layer. there were. About the said cellulose airgel, the average pore diameter and the average distance between fiber bundles were measured by the above-mentioned method. As a result, the average pore diameter and average fiber bundle distance of the first airgel layer were 0.4 μm and 4 μm, and the average pore diameter and average fiber bundle distance of the second airgel layer were 0.2 μm and 3.5 μm. It was. R1 was 0.45% and R2 was 1.0%.

  The six surfaces of the cellulose hydrogel were subjected to cross-cut processing in the same manner as in Example 1-1. The restoration rate of the processed cellulose airgel was evaluated in the same manner as in Example 1-1.

[Comparative Example 3] Restorability of Cellulose Airgel with Multilayer Structure Cellulose aerogel was prepared in the same manner as in Example 3 except that the same lot of cellulose hydrogel as in Example 3 was not used and cross-cut processing was performed. Evaluated.

  These results are shown in FIG. From FIG. 7, it can be seen that the cellulose airgel of Example 3 in which the surface of the second airgel layer (high fiber density layer) constituting the outermost layer has been cut has a high restoration rate. The 3-minute recovery rate of the cellulose airgel is approximately 0.57, and this value is higher than 0.54, which is the 3-minute recovery rate of the two-layer cellulose airgel of Example 2-1.

  The reason why an excellent restoration rate is obtained in the multilayer cellulose airgel is presumed to be because the multilayer cellulose airgel includes a plurality of first airgel layers (low fiber density layers) that are easy to permeate water. That is, the present invention has more excellent effects in the multilayer cellulose airgel.

[Example 4] Restorability of cellulose airgel having a multilayer structure (1) Preparation of cellulose hydrogel and cellulose airgel Acetic acid bacteria (strain ATCC 23769) were prepared as cellulose-producing bacteria. For liquid medium, corn steep liquor (manufactured by Sigma Aldrich, trade name Corn Step Liquid) 10 mL, fructose 20 g, (NH ₄ ) ₂ SO ₄ 1,65 g, KH ₂ PO ₄ 0.5 g, MgSO ₄ .7H ₂ O 125.0 mg, vitamin mixture 5.0 mL, and salt mixture 5.0 mL were prepared.

  The vitamin mixture is inositol 2.0 mg / L, D-Chiro nicotinic acid 0.4 mg / L, pyridoxine hydrochloride 0.4 mg / L, thiamine hydrochloride 0.4 mg / L, calcium pantothenate 0.2 mg / L, riboflavin It was a mixed solution of 0.2 mg / L, p-aminobenzoic acid 0.2 mg / L, folic acid 0.002 mg / L, and biotin 0.002 mg / L. Each reagent was manufactured by Wako Pure Chemical Industries, Ltd.

The salt mixture was CaCl ₂ · 2H ₂ O 14.7 mg / L, FeSO ₄ · 7H ₂ O 3.6 mg / L, Na ₂ MoO ₄ · 2H ₂ O 2.42 mg / L, ZnSO ₄ · 7H ₂ O 1. It was a mixed solution of 73 mg / L, MnSO ₄ · 5H ₂ O 1.39 mg / L, CuSO ₄ · 5H ₂ O 0.05 mg / L, and each reagent was manufactured by Wako Pure Chemical Industries, Ltd.

  Ingredients other than the vitamin mixture were dissolved in distilled water to prepare a 500 mL aqueous solution. NaOH was added to the aqueous solution to adjust the pH to 5, followed by autoclave sterilization (at 121 ° C. for 20 minutes). Subsequently, the aqueous solution was cooled to room temperature, and then a vitamin mixture treated by filtration sterilization (manufactured by Sartorius steady Biotech, trade name Minisart RC15, pore size 0.20 μm was used as a filter) was added.

  Culturing was performed in a 15 mL falcon tube. The culture temperature was changed to 18 ° C. and 29 ° C. every 5 days for a total of 30 days. This gave a 1 cm thick gel.

  The gel was immersed in water and treated with an autoclave at 105 ° C. for 20 minutes. Next, autoclave treatment was performed 10 times at 105 ° C. for 20 minutes using 0.1 N NaOH instead of water. Further, using water, autoclaving was performed at 105 ° C. for 20 minutes, and washing was sufficiently performed to remove alkali.

  The obtained cellulose hydrogel was put into a 10 mL beaker so that the gas phase at the time of culture was below and the layer was horizontal. Distilled water was put into the beaker so that half of the gel was immersed in water, and freeze-drying was performed for 48 hours (Fukuoka, manufactured by Tokyo Science Instruments Co., Ltd., −40 to 50 ° C., 15 to 25 Pa).

  The gel thus obtained was a total of three transparent layers (first hydrogel layer) produced by 29 ° C. culture and three cloudy layers (second hydrogel layer) produced by 18 ° C. culture. It had a multilayer structure consisting of 6 layers.

  The cellulose hydrogel thus obtained was immersed in water overnight at room temperature. The cellulose hydrogel after immersion was freeze-dried with a freeze dryer for 48 hours to obtain a cellulose airgel. The surfaces of the first hydrogel layer and the second hydrogel layer of the cellulose airgel were observed with a scanning electron microscope (JSM-5200, manufactured by JEOL Ltd.) (FIG. 8). The pore diameter was observed from an electron microscope image. Specifically, the portion indicated by the arrow in FIG. 8 was recognized as the pore diameter, and the pore diameter was measured for a plurality of pores. The average pore diameters of the first hydrogel layer and the second hydrogel layer were 1.0 μm and 0.90 μm, respectively. R1 was 0.28% and R2 was 0.9%.

  Furthermore, the cellulose airgel was cut | disconnected in the surface perpendicular | vertical to the lamination | stacking surface using the razor (Kaishin razor Co., Ltd. product, long pattern gold alpha). The fracture surface was observed with a scanning electron microscope (FIG. 9). The average distance between fiber bundles was measured from an electron microscope image. Specifically, the portion indicated by the arrow in FIG. 9 was recognized as the distance between the fiber bundles, and the interlayer distance was measured for a plurality of fiber bundles. The average fiber bundle distances of the first hydrogel layer and the second hydrogel layer were 3.78 μm and 1.15 μm, respectively.

(2) Restoration of processed cellulose aerogel The cellulose aerogel prepared to a thickness of 1.7 mm in the above (1) was cut with a razor to form a rectangular parallelepiped having a side of about 1.4 cm in length and width. At this time, the laminated surface was made parallel to the bottom surface. The above-described cross-cut processing was performed on the surface of the six surfaces of the cellulose airgel using a razor (manufactured by Kai Razor Co., Ltd., long pattern gold alpha). The depth of cut was 0.5 to 1 mm, and the number of cuts was 100 per side (50 cuts 1 and 50 cuts 2). The minimum angle formed by the depth direction of the cuts 1 and 2 and the surface provided with the cuts was about 90 °.

  Next, the 6th surface of the cellulose airgel is subjected to the above-described through-piercing process using a sewing needle (diameter 0.71 mm), and further, the above-described non-through-hole drilling is performed using a sewing needle (diameter 0.53 mm). Processed. The number of non-through holes was 20 per surface, and the depth was 1 to 5 mm. The minimum angle formed by the depth direction of the non-through hole and the surface provided with the hole was about 90 °.

  Further, as shown in FIG. 3 (c), one deep cut having a depth of 8 mm and a length of 14 mm is made by using a scalpel (Dispomes No. 10 manufactured by ASONE CORPORATION) on two opposing surfaces of the cellulose airgel. Each was provided perpendicular to the surface. The shortest distance between the deep-cut main surface and the cellulose airgel surface parallel to the main surface was 0.3 mm.

  The cellulose airgel processed in this manner was fully immersed in water at 25 ° C., and the restoration rate after 3 minutes was measured. As a result, the recovery rate (restoration rate at 3 minutes) was 0.7.

[Example 5] Effect of aqueous solution <Preparation Example 5-1>
(1) Preparation of aqueous solution containing maltose Maltose (Songton Food Industry Co., Ltd., maltose syrup) was dissolved in water to prepare 0.25 mass% aqueous solution S1. The maltose concentration in the aqueous solution S1 was 0.175% by mass.

(2) Preparation of Cellulose Hydrogel A cubic cellulose hydrogel having the structure shown in FIG. 1 (b) and having a vertical and horizontal side of 1 cm and a height of 1.5 cm (Natadecoko included in “Halohalo” manufactured by Ministop Co., Ltd.) Prepared. Impurities were removed from the Nata de Coco, and after sufficient washing with water, it was washed 10 times with hot water at 100 ° C. The same lot of cellulose hydrogel was used in the following examples.

(3) Immersion and drying At 25 ° C., the processed cellulose hydrogel was immersed in the aqueous solution overnight. The cellulose hydrogel after the immersion was placed in a container filled with the aqueous solution S1, and half of the cellulose hydrogel was immersed in the aqueous solution S1. This container was loaded into a freeze-dryer (Tokyo Science Instruments Co., Ltd., FDU-1200) and freeze-dried at −50 to −40 ° C. and 15 to 25 Pa for 48 hours to obtain a cellulose airgel.

<Example 5-2>
(1) Preparation of processed cellulose aerogel The above-described cross-cut processing was performed on the surface of 6 surfaces of the cellulose aerogel obtained in Preparation Example 5-1, using a razor (manufactured by Kaiken Razor Co., Ltd., long pattern gold alpha). The depth of cut was 0.5 to 1 mm, and the number of cuts was 100 per side (50 cuts 1 and 50 cuts 2). The minimum angle formed by the depth direction of the cuts 1 and 2 and the surface provided with the cuts was about 90 °.

  On the six surfaces of the cellulose airgel, the above-mentioned through-hole drilling process is performed using a sewing needle (diameter 0.71 mm), and further, the above-mentioned non-through-hole drilling process is performed using a sewing needle (diameter 0.53 mm). did. The number of non-through holes was 20 per surface, and the depth was 1 to 5 mm. The minimum angle formed by the depth direction of the non-through hole and the surface provided with the hole was about 90 °.

  Subsequently, as shown in FIG. 3 (c), a depth notch of 8 mm in depth and 14 mm in length is formed using a scalpel (Disposmes No. 10 manufactured by ASONE Corporation) on the two opposing surfaces of the cellulose airgel. One by one was provided perpendicular to the surface. The shortest distance between the deep-cut main surface and the cellulose airgel surface parallel to the main surface was 0.3 mm.

(2) Restoration The processed cellulose aerogel obtained in (1) above was fully immersed in water at 25 ° C. for 5 minutes to obtain a restored cellulose hydrogel. The restoration cellulose hydrogel was evaluated for restoration rate, appearance, and texture. As described above, the restoration rate was obtained from the mass of the restored cellulose hydrogel / the mass of the cellulose airgel. The mass was measured using a chemical balance (Cal Zeiss).

Appearance of the gel was observed visually, and the following criteria: a: totally transparent b: not as transparent as a but white turbid c: no white residue but white turbid d: locally white residue e: Evaluation was made with white remaining as a whole.

The texture was evaluated by the following procedure.
1) A panelist engaged in the development of an edible cellulose hydrogel was given a sample of the cellulose hydrogel used as a raw material in this example, and the freshness, crunchiness, and elasticity (feeling of lump) were understood.
2) Next, the cellulose hydrogel obtained in this example was sampled, and it was evaluated whether the freshness, crunchiness, and elasticity (feeling of lump) were equal to or lower than the original cellulose hydrogel.
3) The above evaluation was performed on five panelists to obtain an average value for each texture. That is, for example, when it is determined that 3 or more out of 5 people have decreased in elasticity, it is determined that “elasticity has decreased”.
4) Based on the following average values: A: Freshness, crunchiness, and lumpiness were the same as the original cellulose hydrogel. B: One of the above three textures decreased. C: The above three textures. Among them, two were decreased. D: Of the above three textures, three were evaluated.

<Example 5-3>
A regenerated cellulose hydrogel was prepared and evaluated in the same manner as in Example 5-2 except that the aqueous solution S2 having a concentration of 0.025% by mass was used instead of the aqueous solution S1.

<Example 5-4>
A regenerated cellulose hydrogel was prepared and evaluated in the same manner as in Example 5-2 except that the aqueous solution S3 having a concentration of 0.0025% by mass was used instead of the aqueous solution S1.

<Example 5-5>
As an aqueous solution containing maltose, 15 mL of maltose (Morning Sugar Mame, manufactured by Sonton Foods Industries Co., Ltd.) and 5 g of gelatin (Morinaga Seika Co., Ltd., Cook Gelatin) were dissolved in 30 mL of water to obtain a stock solution. The stock solution was diluted 10 times with water to prepare an aqueous solution G1. The maltose concentration in the aqueous solution G1 was 2.3% by mass. A regenerated cellulose hydrogel was prepared and evaluated in the same manner as in Example 5-2 except that the aqueous solution G1 was used instead of the aqueous solution S1.

<Example 5-6>
A regenerated cellulose hydrogel was prepared and evaluated in the same manner as in Example 5-5 except that the aqueous solution G2 obtained by diluting the stock solution 1000 times with water was used.

<Example 5-7>
A regenerated cellulose hydrogel was prepared and evaluated in the same manner as in Example 5-2 except that the cellulose hydrogel was not immersed in an aqueous solution containing maltose.

<Example 5-8>
Gelatin (Morinaga Seika Co., Ltd., Cook gelatin) was dissolved in water to obtain a 0.2% by mass aqueous solution. A regenerated cellulose hydrogel was prepared and evaluated in the same manner as in Example 5-2 except that the aqueous solution was used instead of the aqueous solution S1.

<Example 5-9>
A regenerated cellulose hydrogel was prepared and evaluated in the same manner as in Example 5-8, except that a 0.002% by mass gelatin aqueous solution was used.

<Example 5-10>
Agar (Ise Foods Co., Ltd., Daddy Agar) was dissolved in water to obtain a 0.066 mass% aqueous solution. A regenerated cellulose hydrogel was prepared and evaluated in the same manner as in Example 5-2 except that the aqueous solution was used instead of the aqueous solution S1.

<Example 5-11>
A regenerated cellulose hydrogel was prepared and evaluated in the same manner as in Example 5-10 except that a 0.00066 mass% agar aqueous solution was used.

  These results are shown in Table 3.

  From Table 3, it is clear that the cellulose airgel of the present invention using an aqueous solution containing a disaccharide is excellent in the restoration rate and gives a restored cellulose hydrogel excellent in appearance and texture.

10 1st airgel layer 20 2nd airgel layer 30 Notch 1
s1 Side 1 parallel to notch 1
32 depth of cut 2
s2 Side 2 parallel to notch 2
40 through hole 42 non-through hole 44 deep cut s3 side

Claims (10)

(A) A cellulose airgel having a substantially cubic or rectangular parallelepiped shape, comprising a first airgel layer having a low cellulose fiber density and a second airgel layer having a cellulose fiber density higher than that of the first airgel layer,
A step of preparing a cellulose airgel, wherein each layer is laminated so that a main surface of the layer is substantially parallel to a bottom surface of the substantially cubic or substantially rectangular parallelepiped, and one of the outermost layers is the second airgel layer; and (B) Depth x defined by the following formula on the surface of the second airgel layer constituting the outermost layer:
0.02L ≦ x ≦ 0.1L (where L is the average length of the long side and the short side of the surface on which the substantially cubic or rectangular parallelepiped cut is provided)
A plurality of cuts 1 are provided in parallel with either the long side or the short side, or a plurality of cuts 1 with a depth x are provided in parallel with either the long side or the short side, and further on the other side. Providing a plurality of incisions 2 having a depth x in parallel;
A process for producing a processed cellulose aerogel. (A1) A cellulose airgel having a substantially cubic or substantially rectangular parallelepiped shape, comprising a first airgel layer having a low cellulose fiber density and a second airgel layer having a cellulose fiber density higher than that of the first airgel layer, wherein the main surface of the layer is Processing the cellulose airgel in which each layer is laminated so as to be substantially parallel to the bottom surface of the substantially cubic or substantially rectangular parallelepiped,
A step of preparing a one-layer cellulose airgel composed of the second airgel layer, or two or more cellulose airgels in which the second airgel layer is an outermost layer; and (B1) a one-layer cellulose airgel surface or two or more layers of cellulose. Depth x defined by the following formula on the surface of the second airgel layer constituting the outermost layer of the airgel:
0.02L ≦ x ≦ 0.1L (where L is the average length of the long side and the short side of the surface on which the substantially cubic or rectangular parallelepiped cut is provided)
A plurality of cuts 1 are provided in parallel with either the long side or the short side, or a plurality of cuts 1 with a depth x are provided in parallel with either the long side or the short side, and further on the other side. Providing a plurality of incisions 2 having a depth x in parallel;
A process for producing a processed cellulose aerogel. The step (A) or (A1)
(A1) The manufacturing method of Claim 1 or 2 including the process of manufacturing a cellulose hydrogel by culture | cultivating a cellulose producing microbe, and (a2) drying the said cellulose hydrogel and obtaining the cellulose airgel. The step (A) or (A1)
(A3) Cellulose-producing bacteria are cultured in a medium comprising a liquid phase medium part present in the liquid phase and an air phase medium part present in the air phase, and the first hydro having a low fiber density derived from the liquid phase medium part Forming a gel layer and a second hydrogel layer having a high fiber density derived from an air phase medium to obtain a two-layer cellulose hydrogel; and (a4) drying the two-layer cellulose hydrogel to obtain a first hydrogel The manufacturing method of Claim 1 or 2 including the process of obtaining the cellulose airgel which has the said 1st airgel layer derived from a layer, and the said 2nd airgel layer derived from a 2nd hydrogel layer. The step (A) or (A1)
(A5) High temperature culture in which cellulose-producing bacteria are cultured at 23 to 40 ° C. to form a first hydrogel layer having low fiber density, and cellulose-producing bacteria are cultured at 10 to 23 ° C. A step of obtaining a multilayer cellulose hydrogel in which three or more layers of the first hydrogel layer and the second hydrogel layer are alternately laminated by repeating low temperature culture to form two hydrogel layers, and (a6) the multilayer A step of drying a cellulose hydrogel to obtain a multilayer cellulose airgel in which three or more layers of the first airgel layer derived from the first hydrogel layer and the second airgel layer derived from the second hydrogel layer are alternately laminated. The manufacturing method of Claim 1 or 2 containing this. (A2) A substantially cubic or substantially rectangular parallelepiped having a surface which is produced from a cellulose hydrogel obtained by culturing cellulose-producing bacteria in a medium having an air phase medium portion present in the air phase and which has been exposed to air during the culture. (B2) depth x defined by the following formula on the surface:
0.02L ≦ x ≦ 0.1L (where L is the average length of the long side and the short side of the surface on which the substantially cubic or rectangular parallelepiped cut is provided)
A plurality of cuts 1 are provided in parallel with either the long side or the short side, or a plurality of cuts 1 with a depth x are provided in parallel with either the long side or the short side, and further on the other side. Providing a plurality of incisions 2 having a depth x in parallel;
A process for producing a processed cellulose aerogel. (A3) A substantially cubic or substantially rectangular parallelepiped produced from a cellulose hydrogel obtained by culturing a cellulose-producing bacterium in a medium comprising an air-phase medium part present in the air phase and a liquid-phase medium part present in the liquid phase A cellulose airgel of
A first airgel layer having a low cellulose fiber density derived from an air phase medium part, and a second airgel layer derived from a liquid phase medium part having a cellulose fiber density higher than that of the first airgel layer, the main surface of the layer being the Each layer is laminated so as to be substantially parallel to the bottom surface of a substantially cube or a substantially rectangular parallelepiped, and one of the outermost layers is a cellulose airgel that is the first airgel layer having a surface exposed to air during the culture. A step of preparing, and (B3) depth x defined by the following formula on the surface of the first airgel layer constituting the outermost layer:
0.02L ≦ x ≦ 0.1L (where L is the average length of the long side and the short side of the surface on which the substantially cubic or rectangular parallelepiped cut is provided)
A plurality of cuts 1 are provided in parallel with either the long side or the short side, or a plurality of cuts 1 with a depth x are provided in parallel with either the long side or the short side, and further on the other side. Providing a plurality of incisions 2 having a depth x in parallel;
A process for producing a processed cellulose aerogel. The length of the cut 1 in the steps (B) to (B3) is 0.7L1 to L1 (where L1 is the length of the side 1 parallel to the cut 1),
The manufacturing method in any one of Claims 1-7 whose length of the notch 2 is 0.7L2-L2 (however, L2 is the length of the side 2 parallel to the notch 2). The interval between adjacent cuts 1 in the steps (B) to (B3) is L1 / 5 to L1 / 100 (where L1 is the length of the side 1 parallel to the cut 1),
The manufacturing method in any one of Claims 1-8 whose space | interval of adjacent notches 2 is L2 / 5-L2 / 100 (however, L2 is the length of the side 2 parallel to the notches 2). The steps (B) to (B3)
(B1) The step of providing the cut 1 or the cut 1 and the cut 2 on the other five surfaces of the substantially cube or the substantially rectangular parallelepiped,
(B2) providing a puncture hole penetrating from the center of the surface to the center of the opposite surface on each surface of the substantially cubic or substantially rectangular parallelepiped;
(B3) a step of providing a plurality of non-penetrating puncture holes on each surface of the substantially cube or cuboid toward the opposite surface; and (b4) 0.5 M on two opposite surfaces of the substantially cube or cuboid. A step of providing one deep cut at a depth of ˜0.7M (where M is the distance between the opposing surfaces) one by one so that both deep cuts do not bond in the cellulose airgel;
The manufacturing method in any one of Claims 1-9 which further contains.