JPH11343339A - Biodegradable water-absorbing resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a novel biodegradable water-absorbing resin comprising a crosslinked poly-γ-glutamic acid. SOLUTION: There are provided biodegradable water-absorbing resins each comprising a poly-γ-glutamic acid and including the following resins (1) to (4): (1) a biodegradable water-absorbing resin prepared by reacting (A) a poly-γ- glutamic acid or (B) a poly-γ-glutamate with (C) a compound having at least two functional groups reactive with a carboxyl group derived from the poly-γ- glutamic acid in the molecule, (2) the biodegradable water-absorbing resin as described in (1), wherein B is prepared by reacting 1 equivalent of the carboxylic acid of the poly-γ-glutamic acid with 0.5-1.0 equivalent of a basic compound, (3) the biodegradable highly water absorbing resin as described in (1), wherein C is a polyepoxide compound, and (4) the biodegradable highly water-absorbing resin as described in (1) and prepared by reacting 100 pts.wt. A or B with 0.1-5.0 pts.wt. polyepoxy compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a biodegradable water-absorbing resin. More specifically, the present invention relates to a water-absorbing resin having excellent water-absorbing ability and biodegradability.

[0002]

2. Description of the Related Art In recent years, water-absorbent resins have been used not only in applications such as disposable diapers, but also in medical fields such as body fluid absorbers, construction fields, food fields such as freshness preserving agents, and agricultural and horticultural fields such as greening. Used in the field. As the water absorbing resin, various kinds of water absorbing resins according to various fields are known.

[0003] Among these various water-absorbing resins, an acrylic acid-based water-absorbing resin has a certain level of water absorbing ability, and
Because it is inexpensive, it is widely used. However, since it has almost no biodegradability, it is not decomposed by bacteria in the soil and the like, causing environmental problems such as environmental pollution. In order to solve this problem, starch-based water-absorbent resins, hyaluronic acid-based water-absorbent resins, and the like have been used as biodegradable water-absorbent resins. As these biodegradable water-absorbing resins, poly-γ-glutamic acid-based crosslinked products and the like have been proposed (for example, JP-A-6-322358, JP-A-7-300563, etc.). However, poly-γ-
The crosslinked glutamic acid has a problem that the water absorption is not sufficient, and a solution has been desired.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a biodegradable water-absorbing resin comprising a crosslinked poly-γ-glutamic acid which has a high water absorption and is stable.

[0005]

The present inventors have conducted various studies in order to develop a biodegradable water-absorbing resin comprising a crosslinked poly-γ-glutamic acid having a high water absorption and being stable. As a result, poly-γ-glutamic acid or poly-γ-
A poly-γ-glutamic acid crosslinked product obtained by reacting a compound having two or more functional groups capable of reacting with a carboxyl group derived from glutamate and poly-γ-glutamic acid in the same molecule has a high water absorption of 100 times or more. It was found that the present invention was completed.

That is, the present invention provides the following biodegradable water-absorbent resin. (1) Compound having two or more functional groups in the same molecule capable of reacting with (A) poly-γ-glutamic acid or (B) poly-γ-glutamate and (C) a carboxyl group derived from poly-γ-glutamic acid And a biodegradable water-absorbent resin. (2) The poly-γ-glutamate salt of (B) is poly-γ-glutamate.
Glutamic acid is added in an amount of 0.5 to 1 equivalent of the carboxylic acid.
The biodegradable water-absorbing resin according to (1), which is obtained by reacting 1.0 equivalent of a basic compound. (3) The biodegradable water-absorbent resin according to (1) or (2), wherein the compound having two or more functional groups of (C) in the same molecule is a polyepoxy compound. (4) 0.1 to 5.0 parts by weight of a polyepoxy compound is reacted with 100 parts by weight of poly-γ-glutamic acid of (A) or 100 parts by weight of poly-γ-glutamate of (B). The biodegradable water-absorbent resin according to any one of (1) to (3). (5) Biodegradable water absorption characterized by reacting (A) poly-γ-glutamic acid or (B) poly-γ-glutamate with a polyepoxy compound under conditions of pH 3 to pH 6. Production method of conductive resin. (6) When reacting (A) poly-γ-glutamic acid or (B) poly-γ-glutamate with a polyepoxy compound, the reaction is carried out under conditions of pH 3.7 to pH 4.8. A method for producing a biodegradable water-absorbent resin. (7) When reacting (A) poly-γ-glutamic acid or (B) poly-γ-glutamate with a polyepoxy compound, an epoxy group derived from a polyepoxy group to a carboxyl group derived from poly-γ-glutamic acid is used. A method for producing a biodegradable water-absorbent resin, wherein the molar ratio is substantially 1. (8) When reacting (A) poly-γ-glutamic acid or the poly-γ-glutamate salt of (B) with a polyepoxy compound, the aqueous solution of poly-γ-glutamic acid is heated and quenched, and then the polyepoxy compound is And a method for producing a biodegradable water-absorbent resin.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The (A) poly-γ-glutamic acid (A) of the present invention is not particularly limited, and those obtained by various production methods can be used. For example, culture methods using microorganisms,
Chemical synthesis methods are conceivable. In particular, those having a molecular weight of several millions or more produced by microorganisms such as Bacillus subtilis are preferable (Japanese Patent Laid-Open No. 1-174397).

The (B) poly-γ-glutamate of the present invention can be obtained by reacting poly-γ-glutamic acid with a basic compound. The reaction method is not particularly limited, and is obtained by dissolving poly-γ-glutamic acid and a basic compound in a solvent at room temperature, followed by heating and stirring. The basic compound is not particularly limited, and may be an alkali such as lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, barium hydroxide, or magnesium hydroxide, a hydroxide of an alkaline earth metal, or an amine. Are preferably used.

When the reaction is carried out, it is preferable to react 0.5 to 1.0 equivalent of the basic compound with respect to 1 equivalent of the carboxylic acid of poly-γ-glutamic acid in a ratio of the poly-γ-glutamic acid and the basic compound. . More preferably, 0.
This is the case where the reaction is carried out in the range of 7 to 0.95. If it is less than 0.5, the solubility of poly-γ-glutamate in water decreases, and high water absorption cannot be obtained. If it exceeds 1.0, salts are undesirably precipitated. The pH for the reaction can be in the range of 3 to 6. Preferably,
3.7 to 4.8. More preferably, 3.75 to
4.75.

The compound (C) of the present invention having two or more functional groups capable of reacting with a carboxyl group derived from poly-γ-glutamic acid in the same molecule is not particularly limited, but a polyepoxy compound is preferred. . The polyepoxy compound is not particularly limited as long as it has two or more epoxy groups in a molecule, but ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, glycerin-1,3-diglycidyl ether, polyethylene glycol And diglycidyl ether.

In the case of crosslinking with a polyepoxy compound, unreacted poly-γ-glutamic acid and the like can be easily removed from the reaction product. In this case, the polyepoxy compound is 100 parts by weight of poly-γ-glutamic acid or 10 parts by weight of poly-γ-glutamate.
It is preferable to add 0.1 to 5.0 parts by weight with respect to 0 parts by weight. In particular, 0.5 to 3.0 parts by weight is preferable. If the amount is less than 0.1 part by weight, the crosslinking reaction does not sufficiently proceed, and a crosslinked product having high water absorption cannot be obtained. Also,
If it exceeds 5.0 parts by weight, a high water absorption is not exhibited, which is not preferable.

The biodegradable water-absorbing resin comprising a crosslinked poly-γ-glutamic acid having a high water absorption according to the present invention can be specifically obtained as follows. That is, poly-
A colorless and transparent resin can be obtained by dissolving γ-glutamic acid and a basic compound in a solvent at room temperature, heating, adding a polyepoxy compound to the mixture, and reacting by stirring. Here, as described above, there is no problem even if poly-γ-glutamate obtained by previously reacting poly-γ-glutamic acid with a basic compound is used.

The solvent used is not particularly limited as long as it can dissolve poly-γ-glutamic acid and a basic compound or poly-γ-glutamate and a polyepoxy compound, and examples thereof include water and dimethyl sulfoxide.
Among them, water is particularly preferred. In the case of dissolving in water, poly-γ-glutamic acid is dissolved in a concentration of 2 to 15% by weight, preferably 6 to 10% by weight.
If it is 2% by weight or less, the water absorption is low, and if it is 15% by weight or more, the gelation rate becomes low, which is not preferable from the viewpoint of yield.

As a reaction form, either a homogeneous system or a suspension system can be suitably used. Reaction temperature is 0 ° C ~
100 ° C is preferred. When the reaction is performed at a low temperature such as 4 ° C., a long time is required for the reaction to proceed. When the temperature exceeds 100 ° C., side reactions such as a decomposition reaction occur undesirably. In addition, poly-
The solution in which γ-glutamic acid is dissolved may be heated and quenched, and then reacted with the polyepoxy compound.
In this case, the reaction time is short, and a high water absorption can be achieved.

The reaction method is not particularly limited, and can be carried out by various methods. Specifically, the reaction can be carried out using a separable flask equipped with a stirrer, or the reaction can be carried out by shaking in an oil bath or water bath using an incubator.

[0016]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Example 1 6.45 g of poly-γ-glutamic acid, 1.8 g of sodium hydroxide and 60 ml of water were charged into a three-neck separable flask equipped with a stirrer and dissolved at room temperature. This aqueous solution is heated to 90 ° C in an oil bath,
Here, ethylene glycol diglycidyl ether 0.2
6 g was added and reacted for 30 minutes to obtain a colorless transparent gel. After completion of the reaction, the gel was poured into methanol to make a powder.
Thereafter, the powder was dried at 50 ° C. under reduced pressure to obtain a powdery resin. When the water absorption of this product was measured by the following method, it was 850 times. [Method of Measuring Water Absorption] 0.1 g of the obtained powdery resin was added to 1 liter of ion-exchanged water, and allowed to stand for 10 minutes. Thereafter, the mixture was filtered through an 80-mesh stainless steel mesh and sufficiently drained, and then the weight was measured. The water absorption was determined by a numerical value obtained by dividing the water absorption weight (the amount obtained by subtracting the dry weight from the wet weight) by the dry weight. Example 2 6.45 g of poly-γ-glutamic acid, 1.4 g of sodium hydroxide and 60 ml of water were charged into a three-neck separable flask equipped with a stirrer and dissolved at room temperature. This aqueous solution is heated to 90 ° C in an oil bath,
Here, ethylene glycol diglycidyl ether 0.2
6 g was added and reacted for 30 minutes to obtain a colorless transparent gel. After completion of the reaction, the gel was poured into methanol to make a powder.
Thereafter, the powder was dried at 50 ° C. under reduced pressure to obtain a powdery resin. When the water absorption of this product was measured by the method described above, it was 550 times. Example 3 10 ml of a 10% aqueous solution of poly-γ-glutamic acid was placed in a 20 ml sample bottle with a lid, and the respective epoxy compounds and sodium hydroxide shown in Table 1 were added to adjust the pH to 4.0. After shaking slowly for the reaction time shown in Table 1 and reacting at room temperature, the water absorption was measured in the same manner as in Example 1. The results are shown in Table 1. [Example 4] In Example 3, ethylene glycol diglycidyl ether (manufactured by Wako Pure Chemical Industries, Ltd.) was used as the epoxy compound, the reaction time was set to 24 hours, and the amount of sodium hydroxide was further described in Table 2. After adjusting to pH, the reaction was carried out in the same manner as in Example 3 except that the reaction was carried out. The results are shown in Table-2. Example 5 Example 3 was repeated except that ethylene glycol diglycidyl ether was used as the epoxy compound and the amount of ethylene glycol diglycidyl ether added and the reaction time were changed as described in Table 3. The same was done. The results are shown in Table-3. Example 6 Poly-γ-glutamic acid was dissolved in water at a concentration of 7% by weight in a 20-ml sample bottle with a lid.
The pH was adjusted to 4.6 with sodium hydroxide and left at 0 ° C. for 5 days. Thereafter, 100 μl of ethylene glycol diglycidyl ether (manufactured by Wako Pure Chemical Industries, Ltd.)
Was added and reacted at 40 ° C. for 48 hours.

The obtained reaction product was taken out of a 20-ml sample bottle with a lid, and unreacted poly-γ-glutamic acid was removed by washing. This reaction product was filtered through an 80-mesh wire gauze and freeze-dried to obtain a cross-linked poly-γ-glutamic acid. The water absorption of this crosslinked product was measured.
The water absorption was determined by immersing the crosslinked poly-γ-glutamic acid in a large excess of distilled water to sufficiently swell, and then measuring the weight (wet weight) after draining with a 80-mesh wire gauze. (The amount obtained by subtracting the dry weight from the above) was divided by the dry weight. The water absorption was 3000 times. Example 7 Poly-γ-glutamic acid was dissolved in water at a concentration of 7% by weight in a 20-ml sample bottle with a lid.
Adjust the pH to 4.6 with sodium hydroxide,
After heating for 1 hour, the mixture was rapidly cooled in ice water. After this,
Add 100 μl of ethylene glycol diglycidyl ether (manufactured by Wako Pure Chemical Industries, Ltd.), and add 48 μg at 40 ° C.
Allowed to react for hours.

The obtained reaction product was taken out of a 20-ml sample bottle with a lid, and unreacted poly-γ-glutamic acid was removed by washing. This reaction product was filtered through an 80-mesh wire gauze and freeze-dried to obtain a cross-linked poly-γ-glutamic acid. The water absorption of this crosslinked product was measured.
The water absorption was determined by immersing the crosslinked poly-γ-glutamic acid in a large excess of distilled water to sufficiently swell, and then measuring the weight (wet weight) after draining with an 80-mesh wire gauze. (The amount obtained by subtracting the dry weight from the above) was divided by the dry weight. The water absorption was 3000 times. Example 8 Poly-γ-glutamic acid was dissolved in water at a concentration of 6, 8, 9, 10% by weight in a 20-ml sample bottle with a lid, and the pH was adjusted to 4.6 with sodium hydroxide. After heating at 60 ° C. for 1 hour, the mixture was rapidly cooled in ice water. Thereafter, 100 μl of ethylene glycol diglycidyl ether (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and 4
The reaction was performed at 0 ° C. for 48 hours.

The obtained reaction product was taken out of a 20-ml sample bottle with a lid, and unreacted poly-γ-glutamic acid was removed by washing. This reaction product was filtered through an 80-mesh wire gauze and freeze-dried to obtain a cross-linked poly-γ-glutamic acid. The water absorption of this crosslinked product was measured.
The water absorption was determined by immersing the crosslinked poly-γ-glutamic acid in a large excess of distilled water to sufficiently swell, and then measuring the weight (wet weight) after draining with a 80-mesh wire gauze. (The amount obtained by subtracting the dry weight from the above) was divided by the dry weight. The water absorption was 2,800, 2900, and 28, respectively, for 6, 8, 9, and 10% by weight aqueous solutions.
It was 00 times and 2700 times.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

The water-absorbent resin of the crosslinked poly-γ-glutamic acid of the present invention exhibits a higher water absorption and also has biodegradability. The above water-absorbent resin is used not only for sanitary fields such as disposable diapers, but also for medical fields, building fields,
It can be applied to a wide range of fields such as food, agriculture and horticulture. In addition, because of its excellent biodegradability, it has the effect that disposal is safe and simple.

Claims (8)

[Claims] 1. A compound having two or more functional groups capable of reacting with (A) poly-γ-glutamic acid or (B) poly-γ-glutamic acid and (C) carboxyl groups derived from poly-γ-glutamic acid in the same molecule. A biodegradable water-absorbent resin characterized by reacting a compound having the same. (B) Poly-γ-glutamic acid is added to poly-γ-glutamic acid in an amount of 0.1 to 1 equivalent of the carboxylic acid.
The biodegradable water-absorbing resin according to claim 1, which is obtained by reacting 5 to 1.0 equivalent of a basic compound. 3. The biodegradable water-absorbent resin according to claim 1, wherein the compound (C) having two or more functional groups in the same molecule is a polyepoxy compound. 4. The poly-γ-glutamic acid 100 of (A)
10 parts by weight or (B) of poly-γ-glutamate
The biodegradable water-absorbing resin according to any one of claims 1 to 3, wherein 0.1 to 5.0 parts by weight of a polyepoxy compound is reacted with 0 parts by weight. 5. A biodegradation characterized by reacting (A) poly-γ-glutamic acid or (B) poly-γ-glutamate with a polyepoxy compound under conditions of pH 3 to pH 6. Of producing a water-soluble water-absorbent resin. 6. The reaction of (A) poly-γ-glutamic acid or (B) poly-γ-glutamate with a polyepoxy compound, wherein the reaction is carried out at a pH of 3.7 to 4.8. A method for producing a biodegradable water-absorbent resin. 7. An epoxy derived from a polyepoxy group relative to a carboxyl group derived from poly-γ-glutamic acid when reacting (A) poly-γ-glutamic acid or (B) poly-γ-glutamic acid with a polyepoxy compound. A method for producing a biodegradable water-absorbent resin, wherein the molar ratio of groups is substantially 1. 8. The reaction between (A) poly-γ-glutamic acid or (B) poly-γ-glutamic acid and a polyepoxy compound, the poly-γ-glutamic acid solution is heated, quenched, and then cooled. A method for producing a biodegradable water-absorbent resin, comprising reacting a compound.