JPH11131318A - Method for separating and recovering sericin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a source material good in biocompatibility by freezing an aqueous solution of sericin prepared by treating silk fibers with high temperature water under a high pressure, washing sericin precipitated during thawing with a hydrophilic organic solvent in a wet condition and recovering sericin in a solid state. SOLUTION: In separating and recovering sericin from silk fibers by treating silk fibers with hot water having temperature 100-140 deg.C under a high pressure and freezing and thawing the obtained aqueous solution of sericin, sericin is separated and recovered from the silk fibers by carrying out the freezing by a slow speed freezing to be >=10 hours from a room temperature to complete freezing, precipitating sericin crystals in a wet condition, washing the crystal with a hydrophilic organic solvent such as ethanol, etc., and recovering sericin in a powdery form. It is preferable to freeze in a low speed by maintaining an aqueous solution of sericin at 0-40 deg.C and thaw in the low speed after gelation. It is preferable to recover sericin having >=100,000 average molecular weight by carrying out the high temperature treatment at 120-130 deg.C for 10-60 minutes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for separating and recovering sericin discarded in a silk scouring waste liquid in the silk fiber industry.

[0002]

2. Description of the Related Art A silk fiber has a double structure in which the surface of an oriented fiber protein, fibroin, is coated with sericin, a glue-like protein, and its component is about 25% to about 75% of fibroin. Consists of% sericin. Since the excellent luster and texture of silk are exhibited by fibroin, sericin is dissolved and removed in the scouring process, and only fibroin is used as a component fiber of the final silk-woven or knitted product.

[0003] Usually, scouring of silk fibers is carried out by scouring with a chemical such as soap or alkali, or enzymatic scouring. In the scouring with a chemical, a surfactant, a metal sequestering agent, etc. are added to a scouring bath in addition to an alkali such as Marcel soap, sodium carbonate or sodium silicate, and the mixture is treated at 95 to 99 ° C. for several hours. In enzymatic scouring, treatment is performed for several hours in a weakly alkaline scouring bath containing proteolytic enzymes.

[0004] By these scouring, sericin is partially hydrolyzed, dissolved in a scouring bath and separated from fibroin, and the silk fiber is further subjected to a post-treatment step, washed sufficiently with hot water and water, and then dried. The scouring water and the washing water containing sericin are usually discarded as a scouring waste liquid.

[0005] Since the ratio of sericin in silk fibers is as high as about 25%, the water pollution load of the scouring waste liquid is high, and various methods have been studied in order to prevent such water pollution (Japanese Patent Application Laid-Open No. 47-47). No. 23247, JP-A-49-117712
No., JP-A-1-168906).

[0006] However, there is a problem in practical use of any of them, and even now, silk refining waste liquid is treated and discarded mainly by the activated sludge method. The heavy burden on the wastewater treatment facility caused by the concentrated refining waste liquid containing sericin is large, and the treatment cost is high.

On the other hand, sericin has attracted attention as a novel organic material which is very excellent due to its good biocompatibility and reactivity. Therefore, separating and recovering sericin is important not only for pollution control but also for economical purposes such as effective use of resources.

Attempts to recover and utilize sericin from silk refined wastewater have long been considered, but the biggest factor that makes recovery difficult is that sericin undergoes partial hydrolysis during the scouring process. The point is that the molecular weight has been reduced.

When a scouring agent having a strong sericin dissolving power such as an alkali is used, sericin is partially hydrolyzed to have a low molecular weight, so that it is difficult to recover sericin. Also, alkali,
It is extremely difficult to separate and collect sericin with high purity from a scouring waste liquid containing a surfactant or the like.

[0010] The refining waste liquid of silk fiber is used for isoelectric point pH of sericin.
After adjusting the pH to 4.0 to 5.0, a filter aid, a flocculant and the like are added, and the formed precipitate is separated by filtration (Japanese Patent Laid-Open No. 1-16).
No. 8906) has low molecular weight of sericin due to scouring, requires addition of a large amount of a drug such as a pH adjuster, a filter aid, a flocculant, and the recovered material contains many impurities other than sericin.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to improve the disadvantages of the prior art, and to provide a method for efficiently separating and recovering high-purity sericin from silk fibers in powder form. .

[0012]

According to the present invention, silk fibers are
High-temperature and high-pressure treatment under controlled conditions of hydrolysis of sericin using high-temperature water, to produce a high-purity, high-molecular-weight sericin aqueous solution, and under special conditions from the aqueous solution, to recover sericin in powder form, The problem has been solved.

That is, in the first method of the present invention, the silk fiber is
Sericin precipitated at the time of thawing is subjected to hydrophilic treatment in a wet state by subjecting the resulting sericin aqueous solution to high-temperature and high-pressure treatment with high-temperature water of 00 ° C to 140 ° C, freezing and thawing the obtained sericin aqueous solution and separating and collecting sericin from the silk fiber. The powdered sericin is recovered by washing with an organic solvent.

In the second method of the present invention, the silk fiber
The above-mentioned freezing is performed from normal temperature to complete freezing (−10 ° C.) by subjecting the resulting sericin aqueous solution to high-temperature and high-pressure treatment with high-temperature water of 00 ° C. to 140 ° C., freezing and thawing, and separating and recovering sericin from silk fibers. (−20 ° C.) or more, preferably at least 15 hours, more preferably at least 24 hours, by slow freezing, and by precipitating sericin in a crystalline form, powdery (or (Crystalline) sericin can be recovered. In such slow freezing, sericin can be precipitated in a state in which filtration is very easy, and sericin can be recovered at a high rate of about 80% or more.

Furthermore, when the sericin aqueous solution is kept at 0 to 40 ° C. and gelled, and then subjected to slow freezing, the sericin recovery rate can be further increased. In addition, it is preferable to carry out the gelation generally at 0 to 20 ° C. from the viewpoint of workability.

Next, thawing after freezing is preferably carried out without raising the temperature so much.
It is good to carry out at about 5 to 25 ° C.

The freezing and thawing may be repeated several times in order to increase the sericin recovery rate. Also,
After thawing, the insolubilized sericin precipitate or gel is filtered,
It is separated and collected by squeeze separation or centrifugation.

At the time of separating and recovering sericin, in the first method of the present invention, sericin is washed by washing wet sericin with a hydrophilic organic solvent such as methanol, ethanol, propanol, butanol, acetone, methyl ethyl ketone, and ethyl acetate. Can be recovered in the form of powder (or crystal), but this organic solvent treatment can be performed by slow freezing as in the second method of the present invention, even when freezing is performed by quick freezing. Even if it is, it is effective.

The silk fibers treated in the present invention are cocoons,
Any state may be used as long as it is made of silk fibers containing sericin, such as raw silk and woven fabric, but prior to high-temperature and high-pressure treatment, oils and fats (natural waxy materials, twisted yarns, woven fabrics, It is preferable to remove in advance oils and the like that have adhered secondarily). In this case, in a state in which oils and fats are not mixed in the sericin aqueous solution and the purity of sericin is not reduced, high temperature by subsequent water High-pressure scouring can be performed. Such fat removal removes silk fibers from petroleum ether,
It may be carried out by a method such as washing with an organic solvent such as hexane or treating with warm water containing a detergent.

Next, the high-temperature and high-pressure treatment of the silk fiber with high-temperature water in the present invention is preferably carried out only with water.
General scouring treatment may be used. In addition, as an apparatus for performing high-temperature and high-pressure treatment of silk fiber only with water, an existing high-temperature and high-pressure scouring tank can be used, and the bath ratio is 1:30 to 1 as usual.
It may be about 1:50. The processing temperature may be 100 to 140 ° C, but is more preferably 120 to 130 ° C. The molecular weight of sericin varies greatly depending on the scouring conditions. Sericin is reduced in molecular weight in a treatment at a high temperature for a long time. Therefore, the treatment time should be as short as possible (about 10 to 60 minutes), In particular, it is better to be 150,000 or more. It is desirable that the mixing reduction rate be kept at about 20%.

The high-purity and high-molecular-weight aqueous sericin solution obtained by the high-temperature and high-pressure treatment may be rapidly frozen as it is, but immediately or after refrigerated storage,
If it is frozen very slowly, sericin molecules will aggregate and precipitate out in a crystalline form. Therefore, it is preferable to freeze slowly under the conditions described above. As a device for performing this slow freezing, a refrigerator capable of adjusting the freezing speed is desirable. However, even in a normal freezer set at −20 ° C., the sericin aqueous solution can be gradually frozen by putting it in an adiabatic container. It is.

Since sericin precipitated in a crystal form by slow freezing is hardly soluble in water and will not dissolve unless boiled, it can be easily solid-liquid separated by thawing and filtering. Sericin which was slowly frozen under suitable conditions, thawed, and separated by filtration was in the form of plate-like crystals, and was dried in a short time even by air drying.
The dried product is bulky and of good quality which easily becomes a powder when crushed by hand.

When normal freezing and thawing is performed, sericin precipitates as in the case of slow freezing, but the crystallization is insufficient, and this is filtered off and air-dried to form a hard solid. Also, in the case of slow freezing, when sericin has a low molecular weight, etc., it may become a hard solid when air-dried.In such a case, according to the first method of the present invention, filtration is performed. Sometimes sericin containing water is treated with an organic solvent such as ethanol or acetone, and the water hydrated into sericin is replaced by the solvent and separated, so this is air-dried and powdered. Sericin can be obtained.

The silk fiber from which most of sericin has been removed by this scouring method is subjected to post-treatment (main kneading), washing and finishing by a conventional soap, alkali method, etc. to remove residual sericin and impurities. However, it is possible to produce a high-quality silk product that makes the most of the characteristics of silk as before or more. In this case, since most of the sericin has been removed in the previous step, only a small amount of the drug is used in the post-treatment step, which is very economical.

The effect of the slow freezing according to the present invention is that the macromolecular sericin aqueous solution obtained by high-temperature and high-pressure scouring with water is frozen very slowly, so that the ice crystals grow and the water around the sericin molecule grows. It is presumed that the structure of the sum changes, and that the sericin molecules whose molecular motion has decreased due to the decrease in temperature are orderedly assembled and crystallized. This aggregate (crystal) of sericin molecules is no longer insoluble in water, and when thawed, is separated in an insoluble state in water, so that it can be easily recovered by filtration.

In addition, since wet sericin which is insufficiently crystallized is partially hydrated, it is treated with an organic solvent to replace the hydrated water molecules with the solvent and to reduce the hydration. As described above, sericin in a powder form can be obtained by breaking the structure.

[0027]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the examples. In the examples, “%” means “% by weight” unless otherwise specified.

[0028]

【Example】

Example 1 (High-temperature / high-pressure scouring of raw silk and slow freezing treatment) Raw silk was subjected to Soxhlet extraction with n-hexane for 8 hours to remove fats and oils, and then distilled with raw silk in a heat-resistant bottle so that the bath ratio was 1:50. Water was added and the mixture was treated at 120 ° C. for 30 minutes in a high-pressure steam treatment apparatus to extract sericin. The sericin extract was put in a plastic bottle, refrigerated at 2 ° C. overnight, gelled, and then put in an insulated box for slow freezing, and placed in a -20 bottle.
It was frozen in a freezer at ℃. After the freezing was completed about 27 hours after the start of freezing, the crystalline sericin was thawed in a thermostat at 30 ° C., and the crystalline sericin collected by suction filtration was air-dried. The yield determined from the raw silk scouring loss and the sericin yield was about 95%.

Example 2 (High-temperature and high-pressure scouring using only water in which hydrolysis of sericin is controlled) The smaller the molecular weight of sericin, the more difficult it is to separate and recover sericin from an aqueous solution. In the same manner as in Example 1, the raw silk from which oils and fats had been removed was scoured at high temperature and pressure using only water. FIG. 1 shows the relationship between the scouring temperature and time and the average molecular weight of sericin, and FIG. 2 shows the relationship between the average molecular weight and the yield. From this result, even when scouring is performed only with water, sericin is successively hydrolyzed to lower the molecular weight in scouring at a high temperature for a long time, so that the scouring temperature is 120 to 13
0 ° C, scouring time is 30-60 minutes at 120 ° C, 130
It is understood that 10 to 30 minutes is desirable in the case of ° C. Under such conditions, sericin having an average molecular weight of 150,000 or more can be efficiently recovered.

Example 3 (Freezing speed and yield of sericin in freezing and thawing treatment) [0030] The state of insolubilization of sericin is different between a case where a sericin aqueous solution is rapidly frozen and a case where a sericin aqueous solution is slowly frozen. This greatly affects the difficulty of filtration and the yield. The delipidated raw silk was scoured with distilled water having a bath ratio of 1:50 at 120 ° C. for 60 minutes. The obtained sericin aqueous solution was frozen at different freezing rates, then thawed, and thawed. After suction-filtration using 5A, it was air-dried and the sericin recovery was compared. Table 1 shows the results.

The freezing method in Table 1 is as follows. (1) Rapid freezing: Performed in ethanol cooled to −60 ° C. with a cool pipe, and after freezing, stored in a −20 ° C. freezer. (2) Ordinary freezing: The sample was left standing in a freezer at -20 ° C. (3) Slow freezing: A plastic bottle containing a sericin aqueous solution was placed in a heat-insulating box, sealed, and allowed to stand in a freezer at -20 ° C. (4) Slow freezing after gelation: The aqueous sericin solution was allowed to stand in a refrigerator at 2 ° C. overnight to gel, and then slowly frozen in the same manner as (3).

Table 1 Relationship between freezing time and yield Freezing method Time required for freezing Time required for filtration Sericin recovery rate Rapid freezing About 1 hour 70 minutes 73.3% Normal freezing About 5 hours 30 minutes 76.8% Slow Fast freezing About 26 hours 15 seconds 81.7% Slow freezing after gelation About 26 hours 10 seconds 85.1%

As shown in Table 1, the slower the freezing rate, the higher the sericin recovery rate, and the time required for filtration is extremely short in slow freezing or slow freezing after gelling as compared to rapid freezing and ordinary freezing. It can be seen that a dried product having good filterability can be obtained.

Example 4 Raw silk from which oil and fat had been removed was subjected to high-temperature and high-pressure scouring with water only in the same manner as in Example 1 and the scouring conditions and sericin recovery method were changed.
The sericin powder was recovered. The recovery rate of sericin is shown in Table 2, and the average molecular weight of the recovered sericin is shown in Table 3. A, B and C in Tables 2 and 3 indicate that sericin was recovered by the following method, respectively. A: Spray drying method 100 ml of sericin aqueous solution was spray-dried by a spray dryer at an inlet temperature of 120 ° C. and a drying rate of 100 ml / hr. B: Freeze-drying method 100 ml of sericin aqueous solution was frozen in a 500 ml eggplant-shaped flask with a cool pipe at -60 ° C, and then dried with a freeze dryer for 2 days. C: Freezing and thawing method Put 100 ml of sericin aqueous solution into a bottle,
After overnight storage in a refrigerator at 5 ° C., it was sealed in a heat-insulating box, left in a freezer at −20 ° C., and slowly frozen. The average molecular weight was determined by dissolving 5 mg of sericin powder in 1 ml of distilled water by boiling, cooling, and filtering with a membrane filter (0.45 μm).
m) and subjected to HPLC (High Performance Liquid Chromatography).

[0035] Table 2 scouring and collection conditions and sericin sericin recovery of immediately after the scouring conditions kneading lapse rate scouring yield (%) Temperature Time (%) Average molecular weight (kDa) A B C 120 ℃ 10 minutes 5 660 9 100 96 〃 30 min 20 390 38 98 95 〃 60 min 23 220 34 95 87 130 ℃ 10 min 15 660 43 100 100 〃 30 min 23 200 45 97 86 〃 60 min 23 76 43 95 59

[0036] Table 3 scouring-average molecular weight relationship sericin recovery condition and the average molecular weight of recovered sericin (kDa) Scouring conditions scouring after drying immediately after drying 20 ° C. for 14 days after storage temperature time (scouring solution) A B C A B C 120 ℃ 10 minutes 660 560 650 570 680 580 480 〃 30 minutes 390 350 390 430 370 360 370 〃 60 minutes 220 200 200 240 190 200 210 130 ℃ 10 minutes 660 530 560 510 570 580 530 〃 30 minutes 200 200 200 220 190 190 200 〃 60 minutes 76 64 69 83 64 62 83

From these results, sericin having an average molecular weight of 100,000 or more (100 kDa or more) can be obtained by specifying the scouring conditions.
Spray drying and freeze-drying of B are also possible. The freeze-drying of B has a particularly high yield, but the freeze-thaw of C, which requires only a freezer and does not require any special equipment, is very efficient and highly efficient. It can be seen that sericin having a molecular weight can be recovered.

Example 5 When the sericin separated in Example 1 was filtered, it was washed with an organic solvent, and the properties and yield of the recovered sericin were examined.
The results are shown in Table 4 in comparison with those of products obtained by quick freezing. Table 4 Effect of organic solvent washing during filtration Yield of solvent sericin used for washing under freezing conditions Properties of sericin Slow freezing Ethanol 89% White crystals Slow freezing Acetone 89% White crystals Slow freezing Unwashed 94% Includes white mass about 5mm in diameter, but easy to powder with light pressing. Easy to freeze Quick freezing Unwashed 90% Brown very hard mass Quick freezing Ethanol 87% Lightly colored powder Quick frozen acetone 86% Lightly colored powder

[0039]

【The invention's effect】

(1) In the present invention, sericin of silk fiber can be easily separated and recovered in a powder form that is easy to handle with good workability. (2) The method for separating and recovering sericin according to the present invention induces the insolubilization of sericin by a mere temperature change, so that no agent such as a flocculant or a pH adjuster is required, and the method is simple. , Good operability, and no contamination of sericin by chemicals. (3) Since the water-soluble amino acids, saccharides, surfactants, and other impurities can be removed from the aqueous sericin solution in the freeze-insolubilization step and the subsequent separation and recovery step, the purity of sericin is improved. When a volatile solvent is used, sericin is further washed with the solvent to improve the purity. (4) In the present invention, sericin having a high molecular weight having an average molecular weight of 100,000 or more can be obtained with high purity, so that sericin in silk fiber can be effectively used as an organic resource having good biocompatibility and reactivity.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between scouring temperature and time and the average molecular weight of sericin.

FIG. 2 is a graph showing a change in yield when sericin aqueous solutions having different average molecular weights are recovered by a freeze-thaw method.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kiyoshi Hayakawa 26-8 Ryugaoka, Otsu City, Shiga Prefecture

Claims (4)

[Claims] 1. A method of treating silk fibers with high-temperature and high-pressure water at a temperature of 100 ° C. to 140 ° C. to freeze and thaw the obtained sericin aqueous solution to separate and recover sericin from the silk fibers. A method for separating and recovering sericin from silk fibers, wherein the precipitated sericin is washed with a hydrophilic organic solvent in a wet state and recovered in a powder form. 2. A method in which a silk fiber is subjected to high-temperature and high-pressure treatment with high-temperature water at 100 ° C. to 140 ° C., and the obtained sericin aqueous solution is frozen and thawed to separate and recover sericin from the silk fiber. A method for separating and recovering sericin from silk fiber, wherein the method is performed by slow freezing such that the time from normal temperature to complete freezing is 10 hours or more, and selicin is precipitated in a crystalline form and recovered in a powder form. . 3. The method according to claim 2, wherein the slow-speed freezing is performed after the sericin aqueous solution is maintained at 0 to 40 ° C. and gelled. 4. The sericin having an average molecular weight of 100,000 or more is recovered by performing the high-temperature and high-pressure treatment at 120 to 130 ° C. for 10 to 60 minutes.
the method of.