JP3416741B2 - Novel biodegradable superabsorbent and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel biodegradable highly water absorbent body and a method for producing the same. The biodegradable highly water-absorbing material of the present invention undergoes biodegradation in nature, and therefore, for example, a modifier in the field of civil engineering, a soil improver in the field of agriculture and horticulture, a seed coating agent, a water retention agent for plant cultivation, in the field of makeup and toiletries. It can be used for disposable diapers, sanitary products, mechanochemical materials, etc.

[0002]

2. Description of the Related Art It is known that superabsorbents are formed by using graft polymerization, radiation crosslinking, ionic crosslinking, crosslinking with a crosslinking agent, molecular crosslinking by repeating freezing and melting on a water-soluble polymer. There is. Unlike water absorbents such as cloth and cotton, these compounds have the property that they do not release water even when pressure is applied, and by utilizing these properties, after absorbing aqueous dirt, it retains it so that it does not leak. Possible products,
For example, it is often used in disposable diapers and sanitary products.

As such a water-absorbing material, a starch-based high water-absorbing material obtained by graft-polymerizing a synthetic monomer such as acrylic acid into starch as a raw material and three-dimensionally crosslinking it, or a biological hydrogel Examples of the hyaluronic acid-based superabsorbent, chemically synthesized polyvinyl alcohol-based superabsorbent, acrylate-based superabsorbent, and acrylamide-based superabsorbent.

[0004] When used in the natural world like a soil conditioner, these superabsorbents remain without being decomposed in the natural world after use. Also, it is very difficult to collect these. Therefore, from the viewpoint of environmental protection, there is an urgent need to develop a highly water-absorbing body having biodegradability that can be decomposed by microorganisms living in the natural world after use and taken into the carbon cycle in nature.

Further, since the super absorbent body using only poly (γ-glutamic acid) absorbs a liquid containing an electrolyte such as NaCl or CaCl ₂ , the water absorption capacity is extremely lowered.
It is necessary to develop a highly water-absorbent body that has biodegradability that does not reduce the water absorption capacity even if it contains an electrolyte.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a biodegradable superabsorbent body which overcomes the drawbacks of the conventional superabsorbent body and can be used in the natural world. To do.

[0007]

Means for Solving the Problems As a result of various studies to develop a highly water-absorbing material having good biodegradability, the present inventors have found that poly (γ-), which is a biodegradable water-soluble polymer. Glutamic acid) and poly (ε-lysine) are mixed at a specified concentration in an aqueous solution or water-soluble solution, and the crosslinked product obtained by irradiating with a specified irradiation dose of radiation has excellent water absorption without losing biodegradability. Based on this finding, they have completed the biodegradable highly water-absorbing material of the present invention.

The present invention has the following configuration. (1) A biodegradable highly water-absorbing material comprising a poly ([gamma] -glutamic acid) and a poly ([epsilon] -lysine) mixed radiation cross-linked product having a water absorption capacity of 10 or more. (2) Mixing water with a water-soluble solvent or water such that the concentration of poly (γ-glutamic acid) is 0.1 to 6% by weight and the concentration of poly (ε-lysine) is 0.1 to 10% by weight. A method for producing a biodegradable highly water-absorbing body, which comprises dissolving in a solvent and then irradiating the obtained mixed solution with radiation, and separating the produced crosslinked body. (3) Poly (γ-glutamic acid) and poly (ε-lysine)
3. The production method according to the above item 2, wherein the weight ratio in the mixed solution is 1: 100 to 100: 1. (4) The production method according to the above item 2, wherein the poly (γ-glutamic acid) and the poly (ε-lysine) are produced by a microorganism.

In the present invention, the water absorption capacity is the ratio of the maximum weight of water retained in the crosslinked product when the dried product of the radiation crosslinked product is swollen in a sufficient amount of water or aqueous solution to the dry weight of the radiation crosslinked product. Say.

The biodegradable highly water-absorbing material of the present invention comprises poly (γ-
Glutamic acid) to a concentration of 0.1 to 6% by weight, preferably 1 to 4.5% by weight, and poly (ε-lysine) to a concentration of 0.1 to 10% by weight, preferably 0.5 to 4% by weight. And the weight ratio of poly (γ-glutamic acid) to poly (ε-lysine) at this time is 1: 100 to 100: 1.
By dissolving in a mixed solvent of water and a water-soluble solvent or water so that the ratio is preferably 2: 8 to 9: 1, and then irradiating the resulting mixed solution with radiation, the resulting crosslinked product is separated. It can be manufactured.

The poly (γ-glutamic acid) used in the present invention is not particularly limited, and any production method such as a production method using a microorganism or a chemical synthesis method may be used. 1-1743
Those obtained by the method for producing poly (γ-glutamic acid) described in Japanese Patent Laid-Open No. 97, that is, Bacillus subtilis (B
It is preferably obtained by culturing Bacillus such as acillus subtilis) in a medium and separating and collecting poly (γ-glutamic acid) from the obtained culture, which has a molecular weight of hundreds of thousands to hundreds. It is preferable to use 100,000.

Further, poly (ε-lysine) used in the present invention
Is not particularly limited, and may be produced by any production method such as a production method using a microorganism or a chemical synthesis method,
Those produced by microorganisms, for example, those obtained by the method for producing poly (ε-lysine) described in JP-B-59-20359, that is, strept which is a poly (ε-lysine) -producing bacterium belonging to the genus Streptomyces. Myces Alblas Subspecies Lizino Polymeras (Strepto
Myces albulus subsp. lysinopolymerus) is cultivated in a medium, and poly (ε-lysine) is separated and collected from the obtained culture.

In the present invention, the water-soluble solvent used as a mixed solvent with water for dissolving poly (γ-glutamic acid) and poly (ε-lysine) is not particularly limited, but poly (γ-glutamic acid) is not particularly limited. ) And poly (ε
It is preferable that the ratio of water is sufficient and the ratio of the water-soluble solvent is appropriately adjusted so that (lysine) can be dissolved. Examples of the water-soluble solvent include methyl alcohol, ethyl alcohol, acetone, methyl acetate, ethyl acetate and the like.

Poly (γ-glutamic acid) and poly (ε
The solution in which lysine) is dissolved is preferably placed in a radiation permeable container such as a glass vial and sealed, and then used. The radiation to be applied to this solution is not particularly limited, and examples thereof include α rays, β rays, γ rays, electron rays, neutron rays, Χ rays, and charged particle rays, but γ rays are preferably used, Further, β-rays, electron beams, and α-rays have small penetrating power, and are suitable for obtaining a target object in a film shape.

The γ-ray is not particularly limited, but for example, one generated by an irradiation device using cobalt 60 as a radiation source is used. In the cross-linking, the temperature is not particularly important, and the cross-linking usually proceeds at room temperature.

The crude product thus obtained is subjected to a purification treatment with an aqueous medium, preferably water such as distilled water, to remove uncrosslinked polymers and decomposed products, thereby obtaining a desired highly pure crosslinked product. It is possible to prepare a biodegradable highly water absorbent body. This purification treatment can usually be performed by immersion, dialysis, or the like.

The biodegradable highly water-absorbent material thus obtained is a colorless and transparent gel, is excellent in water absorption, and swells in a mixed solvent of water and alcohol or a mixed solvent of acetone and water, Methyl alcohol, ethyl alcohol, acetone, tetrahydrofuran, chloroform, benzene, n
-It does not swell in hexane or n-heptane.

The characteristics of the biodegradable water-absorbent material of the present invention are that poly (γ-glutamic acid) and (ε-lysine) upon irradiation with radiation.
It depends on the solution concentration and ratio. When the concentration and the ratio of poly (γ-glutamic acid) are high, the water absorption capacity is high, and when the concentration and the ratio of poly (ε-lysine) are high, the water absorption capacity is low.

Further, the biodegradable superabsorbent material of the present invention is different from the biodegradable superabsorbent material of poly (γ-glutamic acid).
Even in the solution to which the electrolyte is added, the water absorption capacity does not change so much and a high water absorption capacity can be maintained.

[0020]

EXAMPLES The present invention will be specifically described below based on examples. Examples 1 to 11 Crosslinked bodies (biodegradable highly water-absorbing bodies) having different ratios of poly (γ-glutamic acid) and poly (ε-lysine) were produced. A 5% by weight aqueous solution of poly (γ-glutamic acid) and a 5% by weight aqueous solution of poly (ε-lysine) were mixed at a predetermined ratio, and the obtained mixed solution was placed in a vial having a volume of 5 ml, 2 ml each.
The lid was capped under a nitrogen atmosphere. Each of these samples was irradiated with γ-rays at an irradiation dose of 87 kGy by a γ-ray irradiation device equipped with cobalt 60 (110 TBq) as a radiation source. Remove each obtained processed product from each vial,
By immersing in distilled water, uncrosslinked polymer and decomposition products were removed. Thus, a highly pure crosslinked product was obtained. The water absorption of the crosslinked products of these examples was measured. The results are shown in Table 1. The weight ratios given below are
[Poly (ε-lysine) weight]: [Poly (γ-glutamic acid) weight] is shown.

Comparative Example 1 Irradiation treatment was carried out according to Example 1 except that only a 5% by weight aqueous solution of poly (ε-lysine) was used. Comparative Example 2 Irradiation treatment was performed according to Example 1 except that only a 5% by weight aqueous solution of poly (γ-glutamic acid) was used.

[0022]

[Table 1]

When the weight ratio is 90:10 or more, the water absorption ratio is low, but when the weight ratio is in the range of 20:80 to 80:20, the water absorption ratio is about 100 and is almost constant. As a result, it was confirmed that it has a higher water absorption capacity than the crosslinked product of only poly (ε-lysine).

Infrared absorption spectra of the crosslinked product obtained in Example 6 with a weight ratio of 50:50 and Example 3 with a weight ratio of 80:20 are shown in FIGS. 1 and 2. As is apparent from these figures, the methylene group derived 2858Cm ^-1, the specific absorption around 2936cm ^-1 observed in (.gamma.-glutamic acid) absorption and poly (.epsilon.-lysine) of 1408cm ^-1 from the carboxyl group of the It is 1550 cm ⁻¹ derived from an amide group,
Specific absorption at 1655 cm ^-1 was observed. In addition, as a result of elemental analysis, the cross-linked product obtained in a weight ratio of 50:50 was C:
43.9% by weight, H: 6.59% by weight, N: 13.3% by weight, and the crosslinked product obtained at a weight ratio of 80:20 is C:
The amounts were 48.7% by weight, H: 8.1% by weight, and N: 16.8% by weight. From this, when the weight ratio of poly (ε-lysine) was large, the content rate of N was increased.
As a result, the crosslinked product was poly (γ-glutamic acid).
Was confirmed to be a cross-linked product of poly (ε-lysine). The crosslinked product was a water-insoluble gel.

The biodegradability of the obtained crosslinked product was examined by the following method. That is, when each crosslinked product was buried in soil (field) and left to stand, it was decomposed to half after 2 months and completely decomposed after 4 months.

Further, in order to confirm the biodegradability of the obtained crosslinked product, degradation of the crosslinked product by protease was examined. The cross-linked product (600 mg) obtained in Example 3 at a weight ratio of 80:20 was used as an Aspergillus oryzae-produced protease (trade name: Protease A "Amano", manufactured by Amano Pharmaceutical Co., Ltd.) (2.5 mg) and a phosphate buffer solution (10 ml). The mixture was placed in a suspension suspended in and reacted at 40 ° C. for 20 hours. The amount of decomposition was determined by increasing the amount of total organic carbon solubilized in the buffer solution. As a result, the crosslinked product was almost completely solubilized in the buffer solution, and no residual crosslinked product was confirmed.

The crosslinked product obtained in Example 3 in a weight ratio of 80:20 was swollen with a 3% by weight CaCl ₂ aqueous solution and a 3% by weight Na ₂ SO ₄ aqueous solution for 24 hours to determine the water absorption capacity. The water absorption was 52 for CaCl _{2 and} 61 for Na ₂ SO ₄ .

The crosslinked product obtained from the 5% by weight solution of poly (γ-glutamic acid) in Comparative Example 2 was swollen with distilled water, 3% by weight CaCl ₂ aqueous solution and 3% by weight Na ₂ SO ₄ aqueous solution for 24 hours,
The water absorption rate was calculated. Water absorption ratio is 248 for distilled water, CaCl
_It was 12 for _{2 and} 52 for Na ₂ SO ₄ .

From these results, in the crosslinked product of only poly (γ-glutamic acid), the water absorption capacity is remarkably reduced in the aqueous solution containing the electrolyte, but in the crosslinked product of the present invention, the water absorption capacity is not significantly reduced even in the aqueous solution containing the electrolyte. I understand.

[0030]

The biodegradable highly water-absorbing material of the present invention is decomposed by microorganisms living therein even when left in the natural environment,
Has excellent biodegradability. Therefore, the biodegradable water absorbent of the present invention can be suitably used as a soil improving agent that is left in the natural environment after use, a seed coating agent, a material for a water retention agent for plant cultivation, and after use. Can be used for sanitary products, materials for disposable diapers, etc. because it is easy to treat and has excellent water absorbability even in an aqueous solution containing an electrolyte. Further, the highly water-absorbent body of the present invention has good compatibility with living organisms, and thus can be used as a material for artificial skin, and also as a material for mechanochemical elements by utilizing volume change due to the surrounding environment.

[Brief description of drawings]

FIG. 1 is an infrared absorption spectrum diagram of a crosslinked product produced at an irradiation dose of 87 kGy in Example 3.

FIG. 2 is an infrared absorption spectrum diagram of a crosslinked product produced at an irradiation dose of 87 kGy in Example 6.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Hiraki 10-1-104, Otsumen-cho, Kanazawa-ku, Yokohama, Kanagawa Prefecture (56) References International Publication 93/20856 (WO, A1) (58) Fields investigated ( Int.Cl. ⁷ , DB name) C08G 69/00-69/50 G08L 77/00-77/12

Claims (4)

(57) [Claims] 1. A biodegradable highly water-absorbing material comprising a poly ([gamma] -glutamic acid) and a poly ([epsilon] -lysine) mixed radiation cross-linked product having a water absorption capacity of 10 or more. 2. The concentration of poly (γ-glutamic acid) is 0.
1 to 6% by weight and poly (ε-lysine) concentration of 0.1
Biodegradation characterized by being dissolved in a mixed solvent of water and a water-soluble solvent or water to 10 wt% and then irradiating the resulting mixed solution with radiation, and then separating the crosslinked product formed For producing a highly absorbent water absorbent body. 3. Poly (γ-glutamic acid) and poly (ε-)
The weight ratio of the lysine) in the mixed solution is 1: 100 to 100 :.
The manufacturing method according to claim 2, wherein the manufacturing method is 1. 4. The method according to claim 2, wherein poly (γ-glutamic acid) and poly (ε-lysine) are produced by a microorganism.