JP2010024196A - Method of preparing silk fibroin powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a preparation method capable of obtaining silk fibroin powder with the properties inherent to the crystalline structure of silk kept therein, and of enhancing the yield in its embrittlement treatment. <P>SOLUTION: The method of preparing silk fibroin powder is characterized by comprising a process of feeding raw material silk into an aqueous solution of a neutral salt and heating the same to cause the raw material silk to swell, a subsequent process of embrittling the raw material silk by feeding an alkali or an acid into the aqueous solution of a neutral salt, a process of neutralizing the above aqueous solution of a neutral salt by adding an acid or an alkali thereinto, a process of taking out the embrittled raw material silk by dehydrating the neutralized solution, a process of washing the raw material silk taken out, a process of dehydrating the washed raw material silk, a process of drying the dehydrated raw material silk, and a process of crushing the dried raw material silk. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing silk fibroin powder, and more particularly to a method for producing silk fibroin powder capable of improving the yield in embrittlement during the production process.

In order to obtain a silk fibroin powder, it is necessary to embrittle the silk raw material, that is, to appropriately crush the molecular chain and then to pulverize it.
A conventional method for producing silk fibroin powder using alkali embrittlement (Japanese Patent Laid-Open No. 2008-115316) is to embrittle silk material with sodium hydroxide, neutralize with hydrochloric acid, dehydrate, wash, It is dehydrated and dried and pulverized with a ball mill (FIG. 2).
In addition, in the one disclosed in Japanese Patent Laid-Open No. 06-70702, silk raw material is introduced into an aqueous solution in which neutral salt and alkali are dissolved, and the silk raw material is hydrolyzed and neutralized to produce silk fibroin powder. is doing.
JP 2008-115316 A Japanese Patent Laid-Open No. 06-70702

However, the method disclosed in Patent Document 1 has a problem that the yield of silk fibroin powder is as low as 40 to 50% at most, and therefore costs are high. There is also a problem in that the progress of embrittlement varies, and the particle size varies due to the pulverization process performed after the embrittlement process.
Moreover, in the method shown by patent document 2, since it melt | dissolved by hydrolyzing a silk raw material completely, there existed a fault that the property which the original crystal structure of silk had not been utilized. Moreover, since it dissolved, the yield of silk fibroin powder was also low.
The present application solves the above problems, and provides a method for producing a silk fibroin powder that can increase the yield in embrittlement treatment and obtain a silk fibroin powder that retains the properties of the original crystal structure of silk. It is an object.

The method for producing silk fibroin powder according to the present invention is a method for producing silk fibroin powder by crushing embrittled silk raw material into powder, and the silk raw material is charged into a neutral salt aqueous solution and the neutral salt aqueous solution is heated. And the step of swelling the silk raw material and the step of embrittlement of the silk raw material by adding an alkali or acid to the neutral salt aqueous solution after the silk raw material is swollen.
The present invention also includes a step of adding a silk raw material to a neutral salt aqueous solution, heating the neutral salt aqueous solution to swell the silk raw material, and swelling the silk raw material, and then adding the alkali salt or acid to the neutral salt aqueous solution. A step of embrittlement of the silk raw material by adding a solution, a step of neutralizing by adding acid or alkali to the neutral salt aqueous solution, a step of dehydrating the neutralized solution and taking out the embrittled silk raw material, and a removal A step of washing the silk raw material, a step of dehydrating the washed silk raw material, a step of drying the dehydrated silk raw material, and a step of pulverizing the dried silk raw material.

  According to the present invention, first, by treating a silk raw material with a neutral salt aqueous solution, the silk raw material in a state oriented and stretched in a certain direction weakens the orientation of the molecular chain, and the molecular chain shrinks. The silk raw material can be embrittled to the inside without hydrolyzing the outer surface by carrying out an alkali or acid treatment after the loosening state. Thereby, since the melt | dissolution by hydrolysis of a silk raw material can be suppressed as much as possible and it can embrittle to the inside, it can grind | pulverize with few dispersion | variation in a particle size, and can improve a yield.

Hereinafter, preferred embodiments of the present invention will be described in detail.
When the silk raw material is released from the mouth of the cocoon, the molecular chain is oriented and stretched in a certain direction.
Alkali embrittles the silk raw material by cutting the molecular chain of the silk peptide. However, Patent Document 1 allows the alkali to act directly on the silk raw material in which the molecular chain is oriented and stretched in a certain direction. Alternatively, in the method such as 2, the progress of the embrittlement is from the outer surface, and therefore, when the embrittlement is advanced to the inside, the outer surface is completely dissolved (hydrolysis). The silk peptide in the dissolved state is unrecoverable or requires an extra cost to recover, and therefore the yield is poor. In addition, the nature of the original crystal structure of silk is lost.

  Further, in any of the methods of Patent Documents 1 and 2, for example, if the treatment with alkali is lightened and the dissolution of the external surface is to be reduced, the embrittlement is weak and the fibrous material remains, and pulverization with a ball mill or the like As described above, there is a problem that the particle size varies.

  In this regard, in the present invention, the treatment with a neutral salt is first performed as described above. The treatment with the neutral salt swells the silk raw material and can be unwound and stretched without breaking the molecular chain. That is, by treating this silk raw material with a neutral salt aqueous solution, the silk raw material in a state of being oriented and stretched in a certain direction becomes weak in the orientation of the molecular chain, so that the molecular chain is It will be in a state where it has shrunk and loosened. The silk raw material hardly embrittles at a low concentration of neutral salt alone.

  In this way, neutral salt is used to unwind or extend the molecular chain, and then it is alkali or acid treatment in that state, making the silk raw material brittle to the inside without hydrolyzing the outer surface. I was able to. As described above, dissolution due to hydrolysis can be suppressed as much as possible, and the inside can be embrittled. Therefore, the particles can be pulverized with little variation in particle diameter, and the yield can be increased.

As the neutral salt, a neutral salt that can be subjected to salt shrinkage processing on the silk raw material, for example, calcium chloride, potassium bromide, or calcium nitrate can be suitably used.
A silk raw material is put into this neutral salt aqueous solution and heated to about 95 ° C. to perform a swelling treatment.

The embrittlement treatment is performed at a high temperature using an alkali such as sodium hydroxide or potassium hydroxide.
In addition, hydrochloric acid or phosphoric acid can also be used instead of alkali.

Examples and comparative examples will be described below.
[Example 1]
1) 50 g of silk raw material (boulet) and 50 g of neutral salt (calcium chloride dihydrate) were added to 1 liter of water and heated at 95 ° C. for 30 minutes.
2) 5 g of sodium hydroxide dissolved in a small amount of water was added and heated for 2 hours.
3) Appropriate neutralization with hydrochloric acid.
4) Dehydrate the treated product appropriately.
5) Wash with water and wash 6) Dehydrate again.
7) Dry with an electric dryer at 80 ° C for about 3 hours.
8) Grind using a ball mill.
The yield at the time of drying in this example was 62%.

[Example 2]
The same as Example 1 except that 2.5 g of sodium hydroxide was added and heated for 4 hours.
The yield at the time of drying in this example was 65%.

Example 3
The same as Example 1 except that 20 g of calcium chloride was added.
The yield at the time of drying in this example was 77%.

Example 4
The same as Example 1 except that 20 g of calcium chloride and 2.5 g of sodium hydroxide were added and heated for 4.5 hours.
The yield at the time of drying in this example was 72%.

Example 5
The same as Example 1 except that 10 g of calcium chloride was added and heated for 2 hours.
The yield at the time of drying in this example was 72%.

Example 6
Example 10 is the same as Example 1 except that 10 g of calcium chloride and 2.5 g of sodium hydroxide are added and heated for 5 hours.
The yield at the time of drying in this example was 68%.

Example 7
Example 5 is the same as Example 1 except that 5 g of calcium chloride and 5 g of sodium hydroxide are added and heated for 2.5 hours.
The yield at the time of drying in this example was 74%.

Example 8
The same as Example 1 except that 5 g of calcium chloride and 2.5 g of sodium hydroxide were added and heated for 5 hours.
The yield at the time of drying in this example was 70%.

[Comparative Example 1]
The same as Example 1 except that calcium chloride is not added.
The yield at the time of drying in this comparative example was 56%. However, embrittlement did not progress and pulverization did not proceed.

[Comparative Example 2]
The same as Example 1 except that calcium chloride is not added and heating is performed for 3 hours.
The yield at the time of drying in this comparative example was 41%. The embrittlement progressed after 3 hours, but the yield deteriorated.

[Comparative Example 3]
Example 10 is the same as Example 1 except that 10 g of sodium carbonate instead of sodium hydroxide is added instead of calcium chloride, and the mixture is heated for 8 hours.
The yield at the time of drying in this example was 74%. However, embrittlement did not progress and pulverization did not proceed.

Table 1 shows the results of the above examples and comparative examples.
Table 1

As shown in Table 1, by adding a neutral salt (calcium chloride) from Examples 1 to 8 and Comparative Examples 1 to 3, the yield at the time of drying increases, which is suitable for the subsequent pulverization treatment. I understand that. Further, the progress of embrittlement was uniform, there was no variation in the embrittlement treatment as occurred in the comparative example, and a uniform particle size could be achieved by the subsequent pulverization treatment.
In Comparative Examples 1 and 3, the yield is relatively high. This is because the embrittlement is weak, pulverization is not sufficient, and the total yield is calculated with the particle size variation remaining large. . There is a large variation in particle size, making it unacceptable as a product.

Similar results were obtained when potassium bromide or calcium nitrate was used as the neutral salt instead of calcium chloride.
In addition, the embrittlement treatment obtained similar results when potassium hydroxide was used.
The same embrittlement treatment could be performed when hydrochloric acid or phosphoric acid was used instead of alkali.

It is process drawing in this Embodiment. It is process drawing of a prior art example.

Claims (6)

In the method for producing silk fibroin powder that pulverizes embrittled silk raw material into powder,
Adding a silk raw material to a neutral salt aqueous solution and heating the neutral salt aqueous solution to swell the silk raw material;
A method for producing silk fibroin powder, comprising: swelling a silk raw material, and then adding an alkali or an acid to a neutral salt aqueous solution to embrittle the silk raw material. Adding a silk raw material to a neutral salt aqueous solution and heating the neutral salt aqueous solution to swell the silk raw material;
After swelling the silk raw material, adding a alkali or acid to the neutral salt aqueous solution to embrittle the silk raw material,
Neutralizing the neutral salt solution with an acid or alkali;
Dehydrating the neutralized solution and removing the embrittled silk raw material;
A step of washing the extracted silk raw material;
Dehydrating the washed silk raw material;
Drying the dehydrated silk raw material;
A method for producing silk fibroin powder, comprising a step of pulverizing a dried silk raw material.   The method for producing silk fibroin powder according to claim 1 or 2, wherein the neutral salt is a neutral salt that can be subjected to salt shrinkage processing on the silk raw material.   The method for producing silk fibroin powder according to claim 3, wherein the neutral salt is calcium chloride, potassium bromide or calcium nitrate.   The method for producing silk fibroin powder according to any one of claims 1 to 4, wherein sodium hydroxide or potassium hydroxide is used as the alkali.   The method for producing silk fibroin powder according to any one of claims 1 to 5, wherein hydrochloric acid or phosphoric acid is used as the acid.

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