JP3500525B2 - Solvent for silk fibroin - Google Patents

Description

Detailed Description of the Invention

[0001]

[Industrial field of application] Although the recycling of a large amount of waste generated during the silk production process has been studied for a long time, its recycling as fiber has not been successful. The reason is,
This is because no suitable solvent has been found. The present invention relates to a silk fibroin solvent, and the fiber, film and coating material prepared from the silk fibroin solution obtained thereby can be widely used in clothing, medical care, industrial fields and the like. For example, it can be industrially utilized by utilizing the characteristics of silk fibroin such as silk recycled fiber clothing, artificial dialysis membrane, and synthetic fiber processing agent.

[0002]

2. Description of the Related Art Studies on a solvent for silk fibroin have been conducted for a long time, and the following have been proposed so far. 1) Saturated aqueous solution of calcium chloride, 2) Saturated aqueous solution of lithium bromide, 3) Saturated aqueous solution of sodium thiocyanate, 4) Saturated aqueous solution of halide of alkali metal or alkaline earth metal, Schweitzer solvent. However, these solvents have a slow dissolution rate and a dissolution concentration of about several%, and in order to recycle them, it was necessary to improve the dissolution concentration by some method. The present inventor has already found that as a good solvent, the mixing ratio of lower aliphatic alcohol and water is alcohol / water> 1.
The solution in which 20% or more of the alkali metal halide is dissolved in the solvent is proposed as a solvent (hereinafter referred to as MU solvent).

[0003]

[Problems to be Solved by the Invention] MU previously proposed
In the case of the solvent, the solubility is remarkably better than that of the existing solvent, but the behavior of the obtained solution is different from that of fibroin in the silk thread. That is, the fibroin in the silk thread exhibits a polymer liquid crystal behavior in the spout hole when spun, but it is not observed in the MU solvent. Since the mechanical properties of the fiber obtained therefor are insufficient,
An object is to obtain a solvent that solves this problem.

[0004]

Means for Solving the Problems As a result of earnest studies for solving the above problems, the present inventors have surprisingly found that calcium contained in silk fibroin was added to the MU solvent proposed above. , Magnesium salt, etc., and equimolar to 2 molar amount of iminodiacetic acid or ethylenediamine
By dissolving the silk fibroin in a solution containing tetraacetic acid as a solvent, it was revealed that the liquid crystal behavior and polyelectrolyte behavior which were not exhibited at all until now are exhibited, and the lower aliphatic of the present invention is The mixing ratio of alcohol and water is low aliphatic alcohol: water = 50: 50-
A lower aliphatic alcohol alone or a mixed solution of lower aliphatic alcohol and water in an amount of 0: 100 is added to 20
% -Saturated alkali metal salts and iminodiacetic acid
Alternatively, a solvent is obtained by dissolving ethylenediaminetetraacetic acid and equimolar amount to 2 mol of the heavy metals such as calcium and magnesium contained in the silk fibroin. This behavior is almost the same as the solution behavior of the silk fibroin solvent in the spinning hole as already known, and is a behavior never observed in the existing solvent.

The aliphatic alcohol used in the present invention is represented by C _n H _{2n + 1} OH, preferably n =
1 to 4, particularly preferably methyl alcohol, ethyl alcohol and isopropyl alcohol, but not limited thereto.

Of the alkali metals used in the present invention, lithium and sodium are particularly preferable, but the present invention is not limited thereto. Among the halogens used in the present invention, chlorine and bromine are particularly preferable, but the halogen is not limited thereto. Among these alkali metal halides, lithium bromide and lithium chloride are particularly preferable, but are not limited thereto. Alkali metal halide concentration is 20%
~ At a saturated concentration, particularly preferably 40 to 50%,
It is not limited to this.

In the present invention, the mixing ratio of alcohol / water is preferably larger than 1, and particularly preferably 8/2 to 10/0, but not limited to this. Also, lower aliphatic alcohol alone or lower fat
Alcohol is mixed with the mixed solution of group alcohol and water.
Potassium metal salt and iminodiacetic acid (hereinafter referred to as IDA),
Is ethylenediaminetetraacetic acid (hereinafter referred to as EDTA)
Is. The amount added is equal to twice the amount of heavy metals such as calcium contained in the silk fibroin used.

The concentration of silk fibroin dissolved in this solvent is not particularly limited. The reason why when the silk fibroin is dissolved in such a solvent, a completely new solution behavior that has never existed can be considered as follows. That is, it is considered that the end of the silk fibroin molecule in the solvent proposed so far is complex-bonded with calcium and other heavy metals contained therein, and the free spread of the molecule itself is controlled. By that,
It is considered that it does not exhibit solution behavior as a polyelectrolyte. In order to solve this problem, the present invention provides a more stable iminodiacetic acid or ethylenediamine ether with these metals.
It can be considered that this was solved by the presence of traacetic acid in the system. As a result, the solution behavior inherent in silk fibroin is exhibited, and the silk fibroin, which has not been obtained up to now, can be easily regenerated. As its application example, a film, a fiber, various molding materials and the like can be considered.

[0009]

The present invention will be described in more detail with reference to the following examples.
Examples 9 to 24, Comparative Examples 1 to 8 A predetermined amount of dried silk fibroin which has been scoured in advance is sampled in a beaker. And the ethanol: water ratio of 100: 0,
Then, a solution having a lithium bromide (monohydrate) concentration of 40% or a solution containing IDA or EDTA added thereto is added, and then the solution is thoroughly permeated at room temperature for 5 minutes. Then 8
While heating with a water bath adjusted to 5 ° C., the mixture is stirred and dissolved with a stirring rod. An example of the result of measuring the solution viscosity of the obtained liquid at 30 ° C. with an Ubbelohde viscometer is shown in FIG. Further, the intrinsic viscosity η _SP / c was determined from this figure, and the value is shown in Table 1. Similarly, the solution viscosity was measured also when the ratio of ethanol: water: lithium bromide was changed, and the value of the intrinsic viscosity obtained from the measured value is also shown. As is clear from these results, the effect of the addition of IDA and EDTA clearly appears.

Table 2 shows the results of Examples 28 to 33 and Comparative Examples 25 to 27 when ethanol was changed to methanol. In this case as well, obviously IDA and EDT
The effect of addition of A is recognized. Examples 37 to 42 and Comparative Examples 34 to 36 Table 2 also shows the results when propyl alcohol was used instead of ethanol in the above Examples. Also in this case, the effect of the addition is clearly recognized.

[0011]

[Table 1]

[0012]

[Table 2]

[0013]

As apparent from FIG, according to the present invention, the MU solvent of Comparative Example, eta relationship _{SP / c} and concentration, although the comparative relationship, IDA, when added EDTA, the, eta at each concentration _SP / The value of c decreases in the order of EDTA>IDA> MU, and at the same time, the amount of EDTA and IDA added increases in the low concentration range. This suggests that when the silk fibroin molecule is dissolved in this solution, the silk fibroin molecule comes to exist in the solution as a polyelectrolyte, and at the same time, it is also dissolved in a state in which larger molecules are spread. ing. This means that this solvent is a good solvent for completely new silk fibroin which has never been seen before, and it can be prepared at a concentration of 25% like the MU solvent. In addition, this solution has excellent spinnability and is expected to behave as a polymer liquid crystal. By directly spinning or forming a film from this solution by a dry-wet combination method, an excellent silk fibroin fiber or film can be obtained. Can be manufactured.

[Brief description of drawings]

FIG. 1 shows the relationship between the concentration of a solution and the viscosity in Examples.

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Claims (2)

(57) [Claims] 1. A mixture ratio of lower aliphatic alcohol and water is such that low aliphatic alcohol: water = 50: 50 to 0: 100.
A lower aliphatic alcohol alone or a mixed solution of a lower aliphatic alcohol and water in an amount within the range of 20% to a saturated concentration of an alkali metal salt, iminodiacetic acid or ethyl acetate.
A solvent for silk fibroin, which is characterized by dissolving diamine tetraacetic acid and equimolar to 2 mol of heavy metals such as calcium and magnesium contained in silk fibroin. 2. The lower aliphatic alcohol is methyl alcohol, ethyl alcohol and isopropyl alcohol, and the alkali metal salt is lithium bromide, lithium chloride,
The solvent for silk fibroin according to claim 1, which is sodium thiocyanate.