JP3007957B2 - Water absorbing / water retaining material 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 water absorbing / water retaining material and a method for producing the same. This water absorbing / water retaining material is
For example, it can be used as a moisture retaining material for growing plants, a moisturizing material for cosmetics, or a moisturizing material for fresh foods, etc., and a composition for absorbing materials such as medical underpads, tampons, sanitary napkins, etc. It can also be used as a material.

[0002]

2. Description of the Related Art In recent years, absorbent materials that absorb tens to hundreds of times the weight of their own weight and water retention materials that retain absorbed moisture for a long time have been widely used in various industries. For example, sanitary materials such as disposable diapers and sanitary napkins, moisturizers for cosmetic products (see JP-A-58-183612 and JP-A-58-38206), or base materials for deodorant and fragrance (JP-A-61-73664, JP-A-5-73664)
No. 9-189855). In the fields of agriculture and fisheries, for example, food processing sheets (see JP-A-58-58124), soil modifying materials and water retention materials (see JP-A-61-207485, etc.), agricultural chemicals and fertilizers Such as a carrier (JP-A-61-47484)
Reference), water retention material for plant cultivation (Japanese Utility Model Application Laid-Open No. 61-4)
3868), artificial seeds (JP-A-63-133).
No. 904).

The water-absorbing materials used in these prior arts include polyacrylic acid, methacrylic acid,
Alkali metal salts of polymer electrolytes such as (meth) acryloylethanesulfonic acid and copolymers thereof with acrylamide and 2-hydroxyethyl (meth) acrylate;
Moreover, those crosslinked bodies are the main components. Although these materials have the advantage that they can be mass-produced inexpensively by technology in the petrochemical industry, they also have disadvantages such as lack of biodegradability and low biocompatibility, and their use is limited.
For example, when used as a soil modifying material or a water retaining material, these materials remain in the soil for a long period of time, causing a problem in environmental conservation. Also, disposable diapers, sanitary napkins,
When used as an additive for cosmetic products, problems such as irritation to the living body and waste disposal arise.

In order to improve these drawbacks, attempts have been made to develop water-absorbing materials made of natural polymers. For example,
Hyaluronic acid, carrageenan, sodium carboxymethylcellulose (see Japanese Patent Publication No. 47-19965), polysaccharides such as alginic acid, and proteins such as collagen and gelatin are known. However, these natural polymers have problems in that their production requires high extraction costs since they require an extraction operation from natural products, and that their biocompatibility is not sufficient. For this reason, attempts have been made to develop a water-absorbing material using a hybrid of fibroin, a natural polymer having excellent biocompatibility, and a synthetic polymer (see JP-A-58-183612). Problems such as changes in the properties of fibroin due to the synthetic polymer and retention of the synthetic polymer after decomposition may occur.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a water-absorbing / water-holding material which is excellent in biocompatibility, is environmentally friendly, has a simple production process and is inexpensive, and a method for producing the same. Is an issue.

[0006]

Means for Solving the Problems The present inventor can provide a water-absorbing and water-retaining material containing a sulfated silk protein as a main component which can solve the above-mentioned problems by treating a silk protein with a sulfating agent. And completed the present invention.

The silk protein used in the present invention may be any of those produced from silkworms such as silkworms, wild silkworms, and natural silkworms. Any known method such as extraction may be used. In particular, extraction from silkworm cocoons is preferred because of the simplicity of the manufacturing process. Fibroin, sericin and the like are known as silk proteins, and any silk protein may be used for the production of the water-absorbing / water-retaining material of the present invention. Fibroin is particularly preferred in view of productivity. It can also be used as a mixture of various silk proteins. In addition, any form such as fiber, cloth, non-woven fabric, powder, and film can be used.

The method for producing a water-absorbing / water-retaining material of the present invention comprises:
After treating the silk protein with a sulfating agent in the reaction solvent and reacting for a predetermined time, the obtained reaction mixture is neutralized with an aqueous solution of a basic compound, and the sulfated silk protein recovered from the neutralized reaction mixture To obtain a water-absorbing / water-retaining material containing as a main component.

The method for producing a water-absorbing and water-retaining material of the present invention
The details will be described below.

First, a silk protein is dispersed in a reaction solvent. Any reaction solvent may be used as long as it does not react with the sulfating agent, but pyridine and dioxane are preferred from the viewpoint of production cost and the like. The concentration of silk protein is
0.1 to 50% by weight based on the total reaction solvent, preferably
0.1 to 30% by weight. Here, the total reaction solvent is
It means a combination of a solvent used for dispersing the silk protein and a solvent to be mixed with a sulfate agent described below, and is used in an arbitrary amount in each operation. Regarding the concentration of silk protein, if it is less than 0.1% by weight, it is disadvantageous in production cost,
If it exceeds 50% by weight, the sulfation reaction may not proceed uniformly.

The silk protein dispersion thus obtained is
Add to the previously prepared sulfating agent-reaction solvent mixture. The sulfating agent is not particularly limited, and for example, chlorosulfuric acid and fuming sulfuric acid, which are usually used, can be used. This sulfating agent-reaction solvent mixture is prepared by dropping the sulfating agent in a solvent cooled on ice. The mixing ratio of the sulfating agent to the reaction solvent in the reaction system is 1/100 to 1/1 (sulfating agent / total reaction solvent), preferably 5/100 to 1/2. 1/10
If it is less than 0, the reaction does not proceed sufficiently, and if it exceeds 1/1, the production cost is disadvantageous and handling becomes inconvenient.

The amount of water absorption and water retention of the resulting water-absorbing and water-retaining material can be controlled by the amount of the sulfating agent used. The amount used is in the range of 1 to 100 parts (volume / weight), preferably 5 to 100 parts by mass of the silk protein to be reacted.
The range is 50 parts. If the amount is less than 1 part, the reaction does not proceed sufficiently, and if it exceeds 100 parts, the resulting water-absorbing / water-retaining material cannot sufficiently achieve the water-absorbing / water-holding performance.

The above-mentioned sulfation reaction is carried out for a predetermined time at a predetermined temperature while stirring. Depending on the reaction time and the reaction temperature, the water absorption and the water retention of the obtained water absorbing / water retaining material change. The reaction temperature may be any range from room temperature to the boiling point of the solvent, but it is preferable to carry out the reaction at as high a temperature as possible in order to increase the reaction efficiency. The reaction time is not particularly limited, but is preferably 5 minutes or more. If the time is less than 5 minutes, the reaction may not sufficiently proceed.

After completion of the reaction, the reaction mixture is treated with an alkali metal compound such as sodium hydroxide, potassium hydroxide and sodium carbonate, an alkaline earth metal compound such as magnesium hydroxide and calcium hydroxide, and a compound such as ammonia. Neutralize with an aqueous solution of a basic compound. The amount of the basic compound used is preferably approximately equivalent to the amount of the sulfating agent used. The neutralized reaction mixture is filtered to collect water-insolubles. If necessary, the recovered water-insoluble matter may be treated with a normal silk protein dissolving agent, for example, 9 mol of lithium bromide or 60% lithium thiocyanate to remove soluble components. The obtained reaction product is sufficiently washed with water and then dried to obtain a water-absorbing and water-retaining material containing the water-insoluble sulfated silk protein of the present invention as a main component.

[0015]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 Preparation of water-absorbing and water-retaining material using chlorosulfuric acid A silkworm cocoon (Shinakebono) extracted with toluene / methanol was refined by boiling for 1 hour in a 0.5% aqueous sodium carbonate solution. Silk protein was prepared. Disperse 0.2 g of this silk protein in 8 ml of pyridine,
The dispersion was previously immersed in 2 ml of chlorosulfuric acid
It was added to the reaction mixture which had been prepared by mixing in 1 pyridine. Predetermined time (1, 2, and 3) in a constant temperature bath at 80 ° C
Time) The reaction was allowed to proceed while stirring. After the reaction is completed, 2.5
After neutralization with an aqueous solution of N sodium hydroxide, soluble components were removed by suction filtration. A 9M lithium bromide solution was added to the insoluble component, and the mixture was stirred at 60 ° C. for 1 hour or more, and the soluble component was removed again by suction filtration. The obtained sample was washed with a sufficient amount of water and then freeze-dried. The obtained dried product is
As a result of R spectrum analysis, sulfate ester groups and characteristic peaks of ester groups were observed, and it was confirmed that the used silk protein was sulfated. Table 1 shows the relationship between the reaction time and the yield.

Table 1 ────────────────────────── Sample No. Reaction time (hour) Yield (%) ─────── {1 130 2 22 75.5 3 3 95.5} ──────── Example 2 Preparation of water-absorbing and water-retaining material using fuming sulfuric acid 0.2 g of silk protein prepared in the same manner as in Example 1
The mixture was dispersed in ml of dioxane, and the resulting dispersion was added to a reaction solution previously prepared by mixing 2 ml of fuming sulfuric acid in 12 ml of dioxane. Reaction and post-treatment were carried out in the same manner as in Example 1. IR spectrum analysis of the obtained dried product showed peaks of a sulfate ester group and an ester group, and it was confirmed that the used silk protein was sulfated. Table 2 shows the relationship between the reaction time and the yield of the obtained sample.

Table 2 試 料 Sample No. Reaction time (hour) Yield (%) ─────── {4 125 5 2 67.5 6 3 93.0} ──────── Example 3 0.2 g of silk protein prepared in the same manner as in Example 1 was added to 8
The dispersion was added to a reaction solution prepared by mixing chlorosulfuric acid in an amount shown in Table 3 in 12 ml of pyridine. After the reaction was allowed to proceed while stirring in a constant temperature bath at 80 ° C. for 6 hours, post-treatment was performed in the same manner as in Example 1. IR spectrum analysis of the obtained dried product showed peaks of a sulfate ester group and an ester group, and it was confirmed that the used silk protein was sulfated. Table 3 shows the relationship between the amount of chlorosulfuric acid and the yield of the obtained sample.

Table 3 ────────────────────────── Sample number Amount of chlorosulfuric acid (ml) Yield (%) ────── {7 186 8 3 96 9 4 98.5} ─────── Example 4 Measurement of water absorption The water absorption of the water-absorbing and water-retaining materials prepared in Examples 1 to 3 was measured. A predetermined amount of each sample was weighed in a test tube, and the weight was measured (W ₁ ). Add water gradually to the test tube,
Water was added to the maximum that water was not dripped even if the test tube was inverted, and the weight at that time was measured (W ₂ ). The water absorption was calculated by the following equation (1) as the water absorption per unit weight of the sample. Table 4 shows the results. As a comparative example, the same measurement was performed for untreated silk protein, and the results are shown in Table 4.

Water absorption (g / g) = (W ₂ −W ₁ ) / W ₁ (1) Table 4 試 料 Sample No. Water absorption ( g / g) {1 116 293 3 91 4 108 5 90 6 88 7 108 8 8 65 9 54 Comparative Example 36}か ら From the results shown in Table 4, the material of the present invention is a water-absorbing material that can absorb water at least about 55 times its own weight, It can be seen that it has better water absorption than the case of (Comparative Example). Also, it can be seen that the amount of water absorption can be controlled by selecting the reaction conditions.

Example 5 Measurement of Moisture Retention A sample absorbed by the same method as in Example 4 was allowed to stand at room temperature, and one month later, its weight was measured (W ₃ ). The moisture retention was calculated by the following equation (2), and the results are shown in Table 5.

Moisture retention = (W ₃ −W ₁ ) × 100 / (W ₂ −W ₁ ) (2) Table 5 (5) Sample No. Moisture Retention rate (%) 183 256 356 564 80 548 48 649 774 84 8 369 331 Comparative Example 6結果 From the results in Table 5, it is understood that the material of the present invention is a water retention material that can hold approximately 30% or more of moisture for one month or more. On the other hand, in the untreated silk protein (Comparative Example), most of the water evaporates, indicating that there is no water retention effect.

In Examples 1 to 3, the insoluble components recovered from the neutralized reaction mixture are further treated with a silk protein dissolving agent. The recovered insoluble components themselves are the same as in Examples 4 and 5. Has water absorption and water retention properties.

[0024]

The water-absorbing and water-retaining material of the present invention is produced from silk proteins derived from silkworms or silkworm cocoons, and does not require a reaction with a synthetic polymer, so that the production process is simple. The manufacturing cost is also low. In addition, the water absorption of the present invention
Since the water retention material is manufactured from silk protein that is excellent in biocompatibility, it is less irritating to the living body,
In addition, since the skeleton is a protein, biodegradability can be expected, which is effective for environmental conservation.

The water-absorbing / water-retaining material of the present invention has excellent biocompatibility and is biodegradable. Therefore, it can be used as a sanitary material such as disposable diapers, medical underpads, tampons, sanitary napkins, etc. While it can be used as a humectant, it can also be suitably used in the agricultural and fishery fields, such as soil water retention agents and food processing sheets.

Claims (4)

(57) [Claims] 1. A water-absorbing / water-retaining material comprising a sulfated silk protein as a main component. 2. A silk protein is treated with a sulfating agent in a reaction solvent, and after reacting for a predetermined time, the obtained reaction mixture is neutralized with a basic compound aqueous solution and recovered from the neutralized reaction mixture. A method for producing a water-absorbing / water-retaining material, comprising obtaining a water-absorbing / water-retaining material containing a sulfated silk protein as a main component. 3. The method according to claim 2, wherein the treatment with the sulfating agent is performed by mixing the silk protein dispersed in a reaction solvent with the mixture of the sulfating agent and the reaction solvent. 3. The method for producing a water-absorbing and water-retaining material according to item 1. 4. The method according to claim 2, wherein the sulfating agent is chlorosulfuric acid or fuming sulfuric acid.
A method for producing a water retention material.