JPH06346314A - Regenerated silk fibroin yarn and its production - Google Patents

Abstract

PURPOSE:To efficiently produce regenerated silk fibroin yarn having excellent mechanical properties. CONSTITUTION:Silk fibroin is dissolved in a solvent prepared by mixing three components of a halogenated alkali metal salt/a lower alcohol/water in a specific ratio to give a high-viscosity spinning dope. The spinning dope is subjected to dry spinning and then solvent extraction, drawing and cleaning are carried out to give regenerated silk fibroin yarn having excellent mechanical properties.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a regenerated silk fibroin fiber and a method for producing the same. More specifically, it relates to a novel method for efficiently producing regenerated silk fibroin fiber and a regenerated silk fibroin fiber having improved physical properties obtained by the production method.

[0002]

2. Description of the Related Art Usually, cocoons and waste threads are produced in the process of producing silk threads, which are treated as industrial waste. Conventionally, effective utilization of these low-grade silk raw materials has been studied. Among them, a method and conditions for dissolving silk fibroin in an appropriate solvent and forming a fiber from this have been studied. For example, a regenerated silk fibroin fiber (short fiber) is produced on an industrial scale by wet spinning a calcium nitrate solution of silk fibroin. It has been done. Similarly, silk fibroin was dissolved in magnesium nitrate to prepare a spinning solution, which was wet-spun in a saturated solution of ammonium sulfate to obtain a strength of 2.5.
There is also a report that a fiber having a ˜3.0 g / d and an elongation of 20 to 25% was obtained (Yazawa, Journal of Industrial Chemistry, 63, 1481,
1960). Furthermore, Japanese Patent Publication No. 57-4723 proposes a method for producing a fibroin undiluted solution, which discloses a fiberizing method, strength of 2.6 to 3.0 g / d, and elongation of 20 to.
3 illustrates a regenerated silk fibroin fiber having a mechanical property of 30%. A method of forming fibers by a wet spinning method using an aqueous lithium bromide solution of silk fibroin as a spinning stock solution is also known, but the obtained fibers generally show an atypical wide-angle X-ray diffraction scattering pattern.

In any of these conventionally known methods for preparing a spinning dope and a spinning process, complicated steps and long working time are required for selecting a solvent for silk fibroin, dialysis of the spinning dope, etc., and the obtained regenerated silk fibroin is obtained. It was also impractical in terms of fiber quality and mechanical properties. Particularly, in the prior art, a dialysis step is indispensable, and the concentration of the spinning dope must be diluted, and when the solution after dialysis is used as the spinning dope, a concentration step of the solution is necessary. This was one of the obstacles to productivity. When such a solvent is used, the degree of polymerization may be lowered and the quality and mechanical properties of the fiber may be adversely affected.

[0004]

According to the prior art, in a method for producing recycled fibers by using a spinning stock solution in which a low-grade silk raw material is dissolved, (1) the spinning stock solution preparation step is complicated and the productivity is low (2). There are problems such as low spinning productivity due to the low concentration of the spinning solution, and (3) poor quality and mechanical properties of the recycled fiber. An object of the present invention is to provide a regenerated silk fibroin fiber having excellent practicality and a manufacturing method capable of solving the above-mentioned drawbacks of the prior art.

[0005]

In order to solve the above-mentioned problems, the inventors of the present invention have made extensive studies as to solve the problem of low productivity, which has been a problem in the past, and as a result, have found that a concentrated solution having a high viscosity can be obtained. The solvent is found, and the concentrated dissolution enables dry-wet spinning (so-called air gear spinning). Continuous spinning, stretching and desolvation can be performed at a relatively high speed, and at the same time, silk fibroin reproduction with high quality and excellent mechanical properties. The inventors have found that fibers can be obtained, and have finally completed the present invention. That is, according to the present invention, in the regenerated silk fibroin fiber obtained by spinning the silk fibroin spinning dope, the hot water insolubility is at least 70% or more and the value of 2θ: 20.7 ° determined by X-ray diffraction of the fiber is Dissolving silk fibroin in a three-component mixed solvent composed of regenerated silk fibroin fiber, alkali metal halide salt, lower alcohol and water, which has an orientation coefficient of 0.6 or more and a residual solvent amount of 4500 ppm or less. The spinning solution prepared above is discharged into a gas atmosphere through a spinneret having a plurality of pores, and then the spun yarn is brought into contact with a non-solvent liquid to coagulate and partially extract the solvent. Subsequently, the spun yarn is drawn in a coagulating medium and then obtained by washing the yarn with a non-solvent liquid and then collecting the yarn. Degree is a manufacturing method of regenerated silk fibroin fiber characterized by satisfying the following formula (I). -2.35 × Cb + 155 <Ce <99 (I) Cb: Alkali metal halide concentration (wt%) = Alkali metal halide / (Alkali metal salt +)
Lower alcohol + water) × 100 (wt%) However, Cb is 29 to 46. Ce: Lower alcohol ratio = Lower alcohol / (Lower alcohol + Water) × 100 (vol%)

The method for producing the regenerated silk fibroin fiber of the present invention will be described in detail below. The silk fibroin raw material in the present invention is cocoon or silk thread, which is prepared by a conventional scouring method, that is, boiling treatment in alkaline soap water to remove sericin. The type of silk fibroin raw material is not particularly limited, but the intrinsic viscosity is at least 0.50 dl / g or more in terms of spinning stability and stretching stability, and the quality and mechanical properties of the obtained recycled silk fibroin fiber [IV ] Are preferred. When silk fibroin having an intrinsic viscosity of less than 0.50 dl / g is used as a raw material, yarn breakage easily occurs during the yarn making process, and spinning stability becomes low. Also, it becomes difficult to obtain regenerated silk fibroin fiber having the desired mechanical properties by the production method of the present invention. In order to produce a regenerated silk fibroin fiber having desired mechanical properties using a silk fibroin raw material, it is necessary to dissolve it in a solvent to prepare a spinning dope.
Conventionally, silk fibroin has a highly hydrating neutral salt, for example, concentrated solution of calcium chloride, lithium bromide, calcium thiocyanate, calcium nitrate or the like or a copper-alkali solution such as copper hydroxide-ammonia solution, copper hydroxide- It is known to dissolve in an alkali-glycerin solution or the like. However, from the viewpoints of spinning stability, drawing stability, and quality and mechanical properties of the obtained regenerated silk fibroin fiber, a ternary mixed solvent of alkali metal halide / lower alcohol / water, particularly lithium bromide / ethyl alcohol / water. Of 3
It is an important constituent feature of the present invention that the component type mixed solvent is most suitable, that the three component type mixed solvent is used for dissolving silk fibroin, and that the concentration of each component is specified.

Next, the preferred mixing ratio of each component of the alkali metal halide / lower alcohol / water ternary mixed solvent, particularly lithium bromide / ethyl alcohol / water ternary mixed solvent will be described. When the concentration of lithium bromide in the three-component mixed solvent decreases, the solubility and initial dissolution rate of silk fibroin tend to decrease, so that it is not possible to efficiently dissolve the silk fibroin raw material and obtain a homogeneous spinning dope. The intrinsic viscosity [IV] also tends to decrease as the lithium bromide concentration decreases. This tendency becomes remarkable especially when the lithium bromide concentration of the three-component mixed solvent is less than 29% by weight. On the other hand, when the concentration of lithium bromide in the three-component mixed solvent exceeds 46% by weight, the solubility is satisfactory, but the lithium bromide in the spun yarn becomes a high concentration and a large amount is required to remove the solvent. This requires a cleaning medium and a long cleaning time, which is disadvantageous in terms of productivity or cost. Therefore, the concentration of lithium bromide in the three-component mixed solvent is preferably 29 to 46% by weight, and particularly preferably 33 to 42% by weight. In addition,
The solubility used in the present invention is a value calculated by the following formula (II). That is, sufficiently dried purified silk fibroin (weight: W0) was sufficiently immersed in 100 ml of the ternary mixed solvent and heated and dissolved at 70 ° C. for a predetermined time. It suction-filtered using the 3 glass filter. The filter residue was thoroughly washed with water and then dried to weigh the insoluble matter (W). Then, the solubility was calculated from W and W0. The dissolution rate of the present invention is obtained from the initial gradient of solubility with respect to the dissolution time. Solubility (%) = [(W0-W) / W0] × 100 (II)

In the past, ethyl alcohol was considered to be the third component and was not regarded as important, but the present inventors have found that the solubility (solubility, dissolution rate) of silk fibroin and the intrinsic viscosity of silk fibroin after dissolution [IV ], It was found that ethyl alcohol is a main component (good solvent) together with lithium bromide. That is 3
The mixing ratio of ethanol in the component mixed solvent is an important constituent factor of the present invention, and the amount of the remaining components obtained by removing lithium bromide from the three component mixed solvent (that is, ethyl alcohol +
The degree of influence on the solubility (solubility, dissolution rate) of silk fibroin and the intrinsic viscosity [IV] of silk fibroin after dissolution depending on the ratio of ethyl alcohol constituting water) depends on the concentration of lithium bromide. The effect becomes more significant as the concentration decreases. Specifically, in a three-component mixed solvent having a low lithium bromide concentration, the solubility (solubility, dissolution rate) and the intrinsic viscosity of silk fibroin after dissolution can be increased by increasing the ratio of ethyl alcohol / water [IV]. Can be secured. Therefore, it is important to set it in the range represented by the following formula (I) in relation to the lithium bromide concentration.

-2.35 × Cb + 155 <Ce <99 (I) Cb: Alkali metal halide concentration (wt%) = Alkali metal halide / (Alkali metal halide +
Lower alcohol + water) × 100 (wt%) However, Cb is 29 to 46. Ce: Lower alcohol ratio = Lower alcohol / (Lower alcohol + Water) × 100 (vol%) When the volume ratio of the lower alcohol is out of the range of the formula (I) in the three-component mixed solvent, the solubility of silk fibroin is lowered. As a result, the viscosity of the obtained silk fibroin spinning dope becomes low and it becomes difficult to achieve good spinnability and stretchability.

When the concentration of the spinning dope solution, that is, the silk fibroin concentration is extremely increased, it takes a long time to dissolve even if the above-mentioned three-component mixed solvent is used, and it is difficult to defoam due to a decrease in molecular weight and high viscosity. On the other hand, if the concentration of the stock solution for spinning is extremely lowered, problems such as instability in dry-wet spinning and reduction in productivity occur. Therefore, in consideration of the handleability of the spinning dope, the stability of spinning, and the productivity, the preferred concentration range of the spinning dope is 8 to 25% by weight, and more preferably 12 to 22% by weight.

Next, the method of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram of an embodiment of an apparatus used for carrying out the method of the present invention. The silk fibroin spinning stock solution prepared as described above is generally supplied to the spinning section after defoaming and filtering by known methods and conditions. The spinning section is composed of a metering section, a pressurizing section, a filtering section, a dispersing section (not shown), and a spinneret section in which a plurality of pores are arranged in a circumferential or lattice pattern. Here, there is no particular limitation on the arrangement of the spinning pores, but the spacing is set so that the spun yarns do not contact each other. The temperature at which the silk fibroin spinning dope is discharged from the spinning pores may be room temperature, but may be heated at a temperature not higher than the boiling point of the ethyl alcohol if necessary. In short, it is necessary to set the viscosity of the spinning pores under shear deformation to be several tens to several hundreds of poise.

Next, the silk fibroin spinning dope is discharged from the spinning pores, but what is important here is to carry out so-called air gap spinning, in which the silk fibroin spinning dope is once discharged into a gas atmosphere. Depending on the spinning tension of the discharged spun yarn, a lateral blowing airflow is positively sprayed or it is connected to the spinneret and a heat insulating tube is installed downwards to allow it to pass through in a substantially static atmosphere. And then introduced into the coagulator. The distance from the spinneret surface to the coagulating medium depends on so-called spinning conditions such as the discharge amount of the spinning dope, the take-up speed, the type of coagulating medium used, the type of ambient temperature, etc., but the usual air gap length is 3 to 20 cm. Can be adopted. The spun yarn is then contacted with a solidifying medium. For contacting with the solidifying medium, a device in which a yarn path changing roller is arranged in a bath in which the solidifying property circulates, or JP-A-63-12.
A device having a funnel shape described in Japanese Patent No. 710, etc. can be used.

The properties of the coagulable medium used for coagulation are important in terms of the stretchability of the spun yarn and the mechanical properties of the obtained regenerated silk fibroin fiber. A lower alcohol is preferable as a medium suitable for coagulating the silk fibroin spinning dope, and by controlling the diffusion rate of the solvent and the non-solvent (coagulating medium) in the spun yarn, a fiber having high drawability and excellent mechanical properties can be obtained. Methyl alcohol is preferred to obtain. Further, when methyl alcohol in which less than 10% by weight of lithium bromide is dissolved is used, the diffusion rate of the solvent and the non-solvent becomes easier to control. The contact length between the spun yarn and the coagulating medium depends on so-called spinning conditions such as the discharge amount of the spinning solution, the take-up speed, the type of the coagulating medium to be used, the temperature of the coagulating medium, the coagulating method and the structure of the apparatus. ~ 1
50 cm can be generally adopted.

The spun yarn thus brought into contact with the coagulable medium is then continuously wound around the group of rollers to run the yarn and continuously contacted with the non-solvent medium so as to be contained in the yarn. Extraction of the remaining solvent (hereinafter referred to as washing) is performed.
Here, the medium used for washing the yarn is preferably water. The temperature of the cleaning liquid is not particularly limited as long as it is a temperature from room temperature to the boiling point of ethyl alcohol or less, but in consideration of operability, it is 40 ° C.
Should be up to.

The yarn thus partially extracted with the solvent is then introduced into the drawing device. Drawing the spun yarn is an important operation for obtaining the fiber of the present invention, and as the drawing medium, water, lower alcohol, acidic aqueous solution adjusted to PH 3 to 4.5, saturated ammonium sulfate solution, or the like can be used. Although the temperature depends on the medium to be used, higher temperature generally gives higher stretchability, but the temperature should be below the boiling point of ethyl alcohol. The degree of stretching was determined by X-ray diffraction of the fiber as described below, 2θ: 2
The orientation coefficient of 0.7 ° should be at least 0.6 or more. If the orientation coefficient is less than 0.6, the mechanical properties of the resulting fiber will be inferior because the resulting fiber will not be sufficiently loosened. The stretched yarn is subsequently wound around a group of rollers and continuously contacted with a washing solution to wash the solvent (lithium bromide) remaining in the yarn to at least 4500 ppm or less. The type of the final cleaning medium used in the present invention is not particularly limited, but water is preferable from the viewpoint of handleability and economy. Subsequent to this cleaning treatment, the heating roller group is wound around and continuously dried, and then a finishing agent is applied by an oil supply device and the package is wound up. The drawn yarn may be washed and then wound and dried as a package, but the productivity is naturally lowered.

The recycled silk fibroin fiber obtained by the method of the present invention preferably comprises at least 70%, preferably 85%, of hot water-insoluble fibroin (β type structure). If the content of the β-type structure is less than 70% by weight, the hot water resistance is poor and the practical value is lacking. Regarding the degree of molecular orientation of the regenerated silk fibroin fiber of the present invention, it is necessary that the orientation degree F determined by the following formula (III) from the half width in X-ray diffraction method is at least 0.6 or more. When the degree of orientation F is less than 0.6, only fibers having low mechanical properties such as strength and initial tensile elastic modulus and low durability in knitted fabric can be obtained. Orientation degree F = (90 ° -H ° / 2) / 90 ° (III) H; Half-width (°) of the interference intensity distribution curve measured along the Debye ring on the equator line at 2θ = 20.7 °

[0017]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these. The methods for measuring physical properties used in the evaluation of the present invention are as follows. <Intrinsic viscosity> Using an Ubbelohde viscometer, the reduced viscosity ηsp / C of a diluted silk fibroin solution having various concentrations C (g / dl) was measured at 30 ° C.
Extrapolation to = 0 was carried out to obtain the intrinsic viscosity [η] from the vertical axis intercept. <Viscosity of spinning solution> 30 using cone plate type MR-3SOLIQUID METER manufactured by Rheology Co., Ltd.
The viscosity was measured by changing the shear rate at a temperature of ° C, and the zero shear viscosity (poise) was determined by extrapolating the viscosity to zero. <Coagulation property of silk fibroin spinning stock solution> A spinning stock solution having a silk fibroin concentration of 10% was placed on a preparation and pressed with a cover glass having a spacer so as to have a constant thickness in a circular shape, and this was immersed in a coagulation medium. The width of the coagulated region was taken out afterward and observed with an optical microscope, and this was used as an evaluation scale of coagulability. <Spinning stability> Spinning was performed for 8 hours, the frequency of occurrence of yarn breakage during this period was counted, and converted into the number of yarn breakages per unit time and number of spindles. <Drawing property> The maximum draw ratio that allows continuous drawing for 3 minutes is determined, and the draw ratio of 90% of the maximum draw ratio is drawn for 8 hours, and the frequency of occurrence of yarn breakage during this period is counted, It was converted into the number of thread breaks per number of weights. <Residual Solvent Concentration in Fiber> The fiber sample was burned to obtain an ash, which was used as an acid solution and quantified by the yarn absorption method. The residual lithium concentration was converted into the total amount of solvent. <Orientation degree> The orientation degree was calculated according to Equation 3 from the half width of the interference intensity distribution curve measured along the Debye ring on the equator line at 2θ = 20.7 ° in the X-ray diffraction method. <Hot water insolubility> Regenerated silk fibroin fiber was boiled in hot water at 100 ° C for 15 minutes, and the hot water insolubility (%) was determined from the weight loss before boiling. <Fineness> 2 ° C, 65RH% in a constant temperature and humidity atmosphere 2
After standing for 4 hours, the weight having a length of 9 m was measured, and the measured weight was converted into a length of 9000 m to obtain the fineness. <Strength and Elongation> It was measured by a method based on JIS L-1013. Tensilon manufactured by Orientec Co., Ltd. was used as the device, and the gripping interval was 20 cm and the pulling speed was 100% / mi.
The measurement of n and n = 10 was performed, and the arithmetic mean value of the strength, the elongation and the initial tensile elastic modulus was determined. <Light resistance> The tenacity was measured after irradiating the yarn with xenon light at a temperature of 63 ° C for 100 hours, and the retention ratio of tenacity to the tenacity before irradiation was obtained.

Examples 1 to 6 and Comparative Examples 1 to 4 A 0.5% pure marcel soap aqueous solution and silkworm cocoons were used in a bath ratio of 1: 5.
The sample was immersed in 0, heated at 100 ° C. for 1 hour, washed with water, and then subjected to a sericin removal treatment again with a freshly adjusted pure marcel soap aqueous solution having the above-mentioned concentration. After dehydrating the raw material, an aqueous sodium carbonate solution (concentration: 0.
(05%) for 30 minutes, then the treated product was washed with water, dehydrated, neutralized with a 0.1% aqueous acetic acid solution, and further washed with water. This was immersed in ethyl alcohol for 24 hours.
The raw material was taken out from the liquid, air-dried, and then dried at a temperature of 40 ° C. or lower. The purified silk fibroin raw material from which sericin was removed by such treatment was dissolved at a temperature of 70 ° C. using a ternary solvent mixture of lithium bromide / ethyl alcohol / water to give a silk fibroin component concentration of 20% by weight. Was adjusted. The silk fibroin solution has an average pore diameter of 12 μm.
40 ℃ after passing through the filter material consisting of the sintered metal sheet
Degassing was performed under reduced pressure at the temperature of. This silk fibroin solution was used as a spinning stock solution and supplied to a spinning device kept at a temperature of 30 ° C. to carry out measurement and filtration, after which a pore diameter of 0.228 mm and a pore length /
A spinning dope was discharged into an air atmosphere at 0.22 g / min per pore from a spinneret composed of pores having a pore diameter ratio of 4.0 and 36 pores. The spun yarn was run for 1.0 cm in a cylindrical body connected to the spinneret, and then a temperature of 22 ± 2 cm provided at a position 1.8 cm below the surface of the spinneret.
Methyl alcohol at 2 ° C. was circulated and introduced into a tank-type coagulating apparatus having a non-driving yarn path regulating roller near the bottom. Next, the spinning yarn is wound around the roller group provided outside the coagulation bath device to release the spinning tension, and at the same time, the shower device provided in the position close to the roller group sprays the ion-exchanged water on the running yarn. Then, coagulation and solvent extraction were performed. Subsequently, the spun strip was introduced into a horizontal stretching tank in which an aqueous acetic acid solution having a PH of 4.5 and heated to a temperature of 65 ° C. circulated, and stretched with the roller group. Further, after the ion-exchanged water was sprayed on the running yarns by the shower device arranged close to the roller group and the solvent extraction was performed for 360 seconds, 130
The yarn was dried by being wound around a group of rollers heated to a temperature of ° C. After finishing the yarn using a guide type oil agent applying device, the yarn was wound into a package with a winder at a speed of 55 m / min. In this example and the comparative example, the mixing ratio of the components of the solvent used for dissolving the silk fibroin was variously changed. The evaluation results are shown in Table 1.

[0019]

[Table 1]

As is clear from Table 1, those belonging to the present invention (Examples 1 to 6) have good solubility of silk fibroin, and stable dry-wet spinning is possible using the obtained spinning dope. It was It can be seen that 70% or more of the obtained regenerated silk fibroin fiber is insoluble in hot water (β type structure), and it is sufficiently practical for mechanical properties. On the other hand, those which do not belong to the present invention (Comparative Examples 1, 3, and 4) had a dissolution time of the raw material of about 3 times that of the Examples, and the spinning dope exhibited turbid and non-uniform properties. The yarn was frequently broken during the spinning / drawing process, and the condition was poor. The obtained recycled fiber had a low orientation coefficient and lacked practicality in terms of mechanical properties.

Comparative Example 5 The solvent described in Example 1 of Japanese Patent Publication No. 57-4723 [copper hydroxide / ethylenediamine: 6/8 (weight ratio),
Concentration 14% by weight] and dissolution conditions were used to prepare a silk fibroin solution having a concentration of 9.1% by weight. However, the solution showed a remarkable decrease in intrinsic viscosity [IV] in a relatively short time of, for example, about 30 minutes after dissolution, and even after that, a decrease in viscosity with time was observed. An attempt was made to carry out dry-wet spinning using a solution whose time-dependent change was stable as a spinning stock solution without dialysis, but the spinnability was extremely poor and spinning was practically difficult.

Comparative Examples 6 and 7 The type of the solvent was 50% by weight of zinc chloride in water (Comparative Example 6).
And a calcium chloride aqueous solution of 50% by weight (Comparative Example 7), respectively, and the concentration was 16.7% by weight in accordance with the method and conditions described in the Examples of JP-B-57-4723.
Of silk fibroin solution was prepared. Then, dry-wet spinning was attempted without dialysis of the solution, but it was difficult to form fibers in the spinneret in which many yarn breakages occurred.

Comparative Examples 8 and 9 Fibers were obtained in the same manner as in Example 1 except that stretching was performed in air at room temperature in Example 1, and this was designated as Comparative Example 8. Fibers were obtained in the same manner as in Example 1 except that the washing time after stretching in Example 1 was 58 seconds, and this was designated as Comparative Example 9. As a result, the yarn obtained in Comparative Example 8 had an orientation degree of 0.53 and a hot water insolubility of 67%, and was inferior in practicality. Further, the residual amount of solvent of the yarn obtained in Comparative Example 9 was 6800 ppm, and the light resistance was as low as 63%.

[0024]

EFFECTS OF THE INVENTION The fiber of the present invention having the above constitution and the method for producing the same have the following outstanding effects. That is, (1) the solubility is improved as compared with the conventional one,
(2) A high-viscosity spinning stock solution is obtained, which enables dry-wet spinning. (3) The spinning speed can be increased to 50 m / min, which is higher than the conventionally known spinning speed of 6 m / min. ) There are various advantages such as obtaining a fiber with a low residual solvent amount by continuous washing for a short time during spinning, and it is possible to efficiently manufacture recycled silk fibroin fiber and contribute to the industry including recycling. is there.

[Brief description of drawings]

FIG. 1 is a schematic view of an embodiment of an apparatus used for carrying out the method for producing regenerated silk fibroin fiber of the present invention.

[Explanation of sign]

 1: Spinneret 2: Coagulating device 3: Cleaning roller group 4: Stretching device 5: Cleaning roller group 6: Drying roller group 7: Oil agent applying device 8: Winding device (package)

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[Procedure amendment]

[Submission date] October 22, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

[0005]

Means for Solving the Problems The inventors of the present invention have made diligent studies to solve the above problems, and particularly to improve low productivity, which has been a problem in the past. As a result, a specific solvent which can give a concentrated solution with high viscosity As a result, the concentrated solution enables dry-wet spinning (so-called air gear spinning), continuous spinning, drawing, and desolvation at a relatively high speed, and at the same time, silk fibroin recycled fiber having high quality and excellent mechanical properties. The inventors have found that what can be obtained and finally completed the present invention. That is, according to the present invention, in the regenerated silk fibroin fiber obtained by spinning the silk fibroin spinning dope, the hot water insolubility is at least 70% or more and the value of 2θ: 20.7 ° determined by X-ray diffraction of the fiber is Dissolving silk fibroin in a three-component mixed solvent composed of regenerated silk fibroin fiber, alkali metal halide salt, lower alcohol and water, which has an orientation coefficient of 0.6 or more and a residual solvent amount of 4500 ppm or less. The spinning solution prepared above is discharged into a gas atmosphere through a spinneret having a plurality of pores, and then the spun yarn is brought into contact with a non-solvent liquid to coagulate and partially extract the solvent. Subsequently, the spun yarn is drawn in a coagulating medium and then obtained by washing the yarn with a non-solvent liquid and then collecting the yarn. Degree is a manufacturing method of regenerated silk fibroin fiber characterized by satisfying the following formula (I). -2.35 × Cb + 155 <Ce <99 (I) Cb: Alkali metal halide concentration (wt%) = Alkali metal halide / (Alkali metal salt +)
Lower alcohol + water) × 100 (wt%) However, Cb is 29 to 46. Ce: Lower alcohol ratio = Lower alcohol / (Lower alcohol + Water) × 100 (vol%)

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

The method for producing the regenerated silk fibroin fiber of the present invention will be described in detail below. The silk fibroin raw material in the present invention is cocoon or silk thread, which is prepared by a conventional scouring method, that is, boiling treatment in alkaline soap water to remove sericin. The type of silk fibroin raw material is not particularly limited, but the intrinsic viscosity is at least 0.50 dl / g or more in terms of spinning stability and stretching stability, and the quality and mechanical properties of the obtained recycled silk fibroin fiber [IV ] Are preferred. When silk fibroin having an intrinsic viscosity of less than 0.50 dl / g is used as a raw material, yarn breakage easily occurs during the yarn making process, and spinning stability becomes low. Also, it becomes difficult to obtain regenerated silk fibroin fiber having the desired mechanical properties by the production method of the present invention. In order to produce a regenerated silk fibroin fiber having desired mechanical properties using a silk fibroin raw material, it is necessary to dissolve it in a solvent to prepare a spinning dope.
Conventionally, silk fibroin has a highly hydrating neutral salt, for example, concentrated solution of calcium chloride, lithium bromide, calcium thiocyanate, calcium nitrate or the like or a copper-alkali solution such as copper hydroxide-ammonia solution, copper hydroxide- It is known to dissolve in an alkali-glycerin solution or the like. However, from the viewpoints of spinning stability, drawing stability, and quality and mechanical properties of the obtained regenerated silk fibroin fiber, a ternary mixed solvent of alkali metal halide / lower alcohol / water, particularly lithium bromide / ethyl alcohol / water. Of 3
It is an important constituent feature of the present invention that the component type mixed solvent is most suitable, that the three component type mixed solvent is used for dissolving silk fibroin, and that the concentration of each component is specified. Examples of the alkali metal halide in the three-component mixed solvent include lithium bromide, lithium chloride, potassium bromide, potassium chloride, and the like, and lower alcohols include ethyl alcohol, methyl alcohol, and isopropyl. Examples thereof include alcohol and normal propyl alcohol.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

In the past, ethyl alcohol was considered to be the third component and was not regarded as important, but the present inventors have found that the solubility (solubility, dissolution rate) of silk fibroin and the intrinsic viscosity of silk fibroin after dissolution [IV ], It was found that ethyl alcohol is a main component (good solvent) together with lithium bromide. That is 3
The mixing ratio of ethyl alcohol in the component mixed solvent is an important constituent factor of the present invention, and the ratio of ethyl alcohol constituting the residual component amount (that is, ethyl alcohol + water) excluding lithium bromide from the three component mixed solvent. Solubility of silk fibroin (solubility, dissolution rate) and the magnitude of its influence on the intrinsic viscosity [IV] of silk fibroin after dissolution depended on the concentration of lithium bromide, and as the concentration of lithium bromide decreased Becomes noticeable. Specifically, for a ternary mixed solvent having a low lithium bromide concentration, ethyl alcohol /
Solubility (solubility, dissolution rate) by increasing the ratio of water
Also, it becomes possible to secure the intrinsic viscosity [IV] of the silk fibroin after dissolution. Therefore, it is important to set it in the range represented by the following formula (I) in relation to the lithium bromide concentration.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

Next, the silk fibroin spinning dope is discharged from the spinning pores. What is important here is to carry out so-called air gap spinning in which the silk fibroin spinning dope is once discharged into a gas atmosphere.
Depending on the spinning tension of the discharged spun yarn, a lateral blowing airflow is positively sprayed or it is connected to the spinneret and a heat insulating tube is installed downwards to allow it to pass through in a substantially static atmosphere. And then introduced into the coagulator. The distance from the spinneret surface to the coagulating medium depends on so-called spinning conditions such as the discharge amount of the spinning dope, the take-up speed, the type of coagulating medium used, the type of ambient temperature, etc., but the usual air gap length is 1 to 20 cm. Can be adopted. The spun yarn is then contacted with a solidifying medium. For contacting with this coagulable medium, a device in which a yarn path changing roller is arranged in a bath in which coagulability circulates, or JP-A-63-1
An apparatus having a funnel shape described in Japanese Patent No. 2710 can be used.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0013

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The properties of the coagulable medium used for coagulation are important in terms of the stretchability of the spun yarn and the mechanical properties of the obtained regenerated silk fibroin fiber. Lower alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, and normal propyl alcohol are preferable as a suitable medium for coagulating the silk fibroin spinning dope, and control the diffusion rate of solvent and non-solvent (coagulating medium) in the spun yarn. Methyl alcohol is particularly preferable in order to obtain fibers having high drawability and excellent mechanical properties. Further, when methyl alcohol in which less than 10% by weight of lithium bromide is dissolved is used, the diffusion rate of the solvent and the non-solvent becomes easier to control. The contact length between the spun yarn and the coagulable medium depends on the discharge amount of the spinning dope, the take-up speed,
Depending on the type of coagulation medium used, the so-called spinning conditions such as the temperature of the coagulation medium, the coagulation method and the structure of the apparatus, 10 to 150
cm can be generally adopted.

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[Name of item to be corrected] 0015

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The yarn thus partially extracted with the solvent is then introduced into the drawing device. Drawing the spun yarn is an important operation for obtaining the fiber of the present invention, and as the drawing medium, water, lower alcohol, acidic aqueous solution adjusted to PH 3 to 4.5, saturated ammonium sulfate solution, or the like can be used. Although the temperature depends on the medium to be used, a higher temperature generally gives a higher stretchability. However, when ethyl alcohol is used, the temperature should be not higher than the boiling point of ethyl alcohol. The degree of stretching must be such that the orientation coefficient of 2θ: 20.7 ° obtained by X-ray diffraction of the fiber is at least 0.6 or more as described later. If the orientation coefficient is less than 0.6, the mechanical properties of the resulting fiber will be inferior because the resulting fiber will not be sufficiently loosened. The stretched yarn is subsequently wound around a group of rollers and continuously contacted with a cleaning liquid so that the solvent (lithium bromide) remaining in the yarn is at least 4500 p.
Wash until pm or less. The type of the final cleaning medium used in the present invention is not particularly limited, but water is preferable from the viewpoint of handleability and economy. Subsequent to this cleaning treatment, the heating roller group is wound around and continuously dried, and then a finishing agent is applied by an oil supply device and the package is wound up. The drawn yarn may be washed and then wound and dried as a package, but the productivity is naturally lowered.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiromoto Ueshima 4-1-1 Shimoda Higashi, Koshiba City, Nara Prefecture (72) Inventor Katsuya Tani 2-1-1 Katata, Otsu City, Shiga Toyobo Co., Ltd. In-house (72) Inventor Kazuyuki Yabuki 2-1-1 Katata, Otsu, Shiga Prefecture, Toyobo Co., Ltd.

Claims (2)

[Claims] 1. A regenerated silk fibroin fiber obtained by spinning a spinning dope of silk fibroin has a hot water insolubility of at least 70% and a value of 2θ: 20.7 ° as determined by X-ray diffraction of the fiber. A regenerated silk fibroin fiber having an orientation coefficient of 0.6 or more and a residual solvent amount of 4500 ppm or less. 2. A spinning dope prepared by dissolving silk fibroin in a ternary mixed solvent consisting of an alkali metal halide, a lower alcohol and water is passed through a spinneret having a plurality of pores and brought into a gas atmosphere. After discharge, the spun yarn is then contacted with a non-solvent liquid to coagulate and partially extract the solvent, and subsequently the spun yarn is stretched in a coagulating medium before the yarn is non-solvent A method for producing regenerated silk fibroin fiber, which is obtained by washing with a liquid and collecting, and the concentration of each component in the three-component mixed solvent satisfies the following formula (I). -2.35 × Cb + 155 <Ce <99 (I) Cb: Alkali metal halide concentration (wt%) = Alkali metal halide / (Alkali metal salt +)
Lower alcohol + water) × 100 (wt%) However, Cb is 29 to 46. Ce: Lower alcohol ratio = Lower alcohol / (Lower alcohol + Water) × 100 (vol%)