JP2011256488A - Method for producing fiber by wet spinning - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a fiber of protein with a high molecular orientation from dope containing protein.SOLUTION: In a method for producing a fiber by wet spinning, a tubular hollow fiber made from a porous semipermeable membrane is set such that an outer peripheral surface and a tip opening are in a coagulation liquid. Protein that is dissolved in dope is sent to the hollow fiber. The protein is made to be a fiber in a semi-solidification state which can be drawn, by the action of the coagulation liquid that permeates the hollow fiber, and the resulting fiber is discharged from the tip opening of the hollow fiber into the coagulation liquid. The fiber in the semi-solidification state which has been discharged into the coagulation liquid is drawn and then coagulated, thereby obtaining a protein fiber.

Description

  The present invention relates to a method for producing fibers by wet spinning.

  Wet spinning is a method in which a dope (a material in which a polymer is dissolved in a solvent or the like) is directly discharged from a micro nozzle into a coagulating liquid, and the solvent in the dope is dissolved in the coagulating liquid and the polymer is solidified and fiberized. . Particularly in protein-spun wet spinning, in which the polymer is a protein, rapid solidification and aggregation of the protein is likely to occur in the coagulation liquid, so that there is a problem that a constant fiber diameter cannot be obtained and stretching work cannot be performed later. In addition, once solidified, the protein has a problem that it is difficult to redissolve due to the interaction between molecules.

  In Patent Document 1, when a part of a wall forming the tubular passage is made of a semipermeable and porous material, the tubular material is surrounded by a fluid material, and the spinning solution is sent along the tubular passage. A spinning method in which the pH, ionic composition, water content, and / or low molecular weight composition of the spinning solution flowing through the tubular passage is changed by the component of the fluid material that penetrates the semipermeable and porous material of the wall. Is described. For example, it can be used to form fibers from a dope containing a protein solution of recombinant silkworm silk or silkworm silk, and other ingredients can be added to the dope to keep the protein in solution. Its components are semi-permeable and porous walls when the dope reaches the appropriate place in the tubular passage where it is desired to induce the conversion of the liquid dope into a solid product such as yarn or fiber. Is removed.

  Patent Document 2 describes a protein fiber production method using an organic acid, an inorganic neutral salt, and hydrogen peroxide as a solid bath composition.

  Patent Document 3 describes a method for producing a fiber comprising a specific ratio of plant protein and polyvinyl alcohol.

Special Table 2003-515209 Japanese Patent Laid-Open No. 48-80761 JP-T-2005-513298

The spinning method of Patent Document 1 describes that the orientation is improved by devising the shape of the tubular passage. For example, in paragraph 0029, “The use of a tapered or divergent mold advantageously induces a flow that is stretched into the droplets to form oriented and stretched packed particles or gaps in the volume phase. The mold tends to orient and stretch such droplets in a direction parallel to the formed product, whereas the divergent mold tends to orient the droplets in the hoop direction across the direction of flow in the tubular passage. It is said that.
However, it is considered that even with the above-described devices, the molecular orientation is still insufficient and a fiber having practically sufficient characteristics cannot be obtained. In addition, in the spinning method of Patent Document 1, as shown in FIG. 11, the components (additives) that hold the protein in the solution are almost removed from the dope containing the protein in the region of the tubular passage. Therefore, it is considered that the protein fibers are pulled out from the outlet of the tubular passage with the coagulation almost completed. For this reason, there is a possibility that the fiber diameter may vary, and it is considered that the orientation cannot be increased by stretching the drawn fiber.

  Accordingly, an object of the present invention is to produce a protein fiber having a high molecular orientation from a dope containing a protein.

  The method for producing a fiber by wet spinning according to the present invention is a protein in which a tubular hollow fiber made of a porous semipermeable membrane is set so that an outer peripheral surface and a tip opening are in a coagulation liquid, and dissolved in a dope To the hollow fiber, and by the action of the coagulation liquid penetrating the hollow fiber, the protein is made into a semi-coagulated fiber that can be drawn and discharged into the coagulation liquid from the opening of the tip of the hollow fiber, and the coagulation liquid The semi-coagulated fiber discharged inside is stretched and then coagulated to obtain a protein fiber.

  The aspect of each element in the present invention is exemplified below.

  The drawing of the semi-solidified fiber discharged into the coagulation liquid may be performed in the coagulation liquid, or in the air such as air or in a liquid other than the coagulation liquid. Since the process can be simplified, it is preferably performed in the discharged coagulating liquid.

1. Hollow fiber The shape of the hollow fiber is not particularly limited, but a straight pipe shape is preferable because stress concentration during stretching can be avoided.
The dimension of the hollow fiber is not particularly limited, but in the case of a straight pipe shape, the length / inner diameter ratio is preferably 200/1 to 20/1. When the length is larger than the same ratio, the protein dissolved in the dope is solidified in the hollow fiber, and the hollow fiber may be clogged. On the other hand, when the length is smaller than the same ratio, it is difficult to discharge the protein dissolved in the dope into the coagulation liquid as a semi-coagulated fiber.
The material of the semipermeable membrane forming the hollow fiber is not particularly limited, but a material having a small interaction with protein and low surface free energy is preferable, and specific examples include polypropylene and the like.
The absolute filtration accuracy of the hollow fiber is not particularly limited, but is preferably 0.01 to 0.1 μm because the coagulation liquid easily permeates.

2. Coagulation liquid The coagulation liquid is not particularly limited, but one kind of liquid may be used, and in order to dissolve the protein on the distal end side and the proximal end side with the middle portion in the length direction of the hollow fiber as a boundary. You may use two types from which the solubility of the additive currently added in dope differs. By using two kinds of coagulation liquids having different solubility of additives, the speed of extracting the additive from the dope in the hollow fiber can be changed, and the coagulation of protein can be controlled. Specific examples include alcohols such as methanol and ethanol, aqueous alcohol solutions such as methanol aqueous solution, and ethanol aqueous solution.

3. Dope Although it does not specifically limit as protein melt | dissolved in dope, It is preferable that molecular weight is 50 KDa or more, More preferably, it is 50 KDa-1000 KDa. This is because when the dope is discharged into the coagulation liquid, the molecules are not interrupted and are likely to become fibrous.

4). Additive The additive added to the dope to dissolve the protein is not particularly limited, and examples include solubilizers such as urea and surfactants.

  The discharge speed represented by the length of the discharged fiber per unit time is not particularly limited, but it is 0.6 to 3 m / min since the yarn breakage after fiber formation can be prevented and the productivity is good. Is preferred. It is also possible to perform spinning at higher speed.

  The stretching ratio when stretching the semi-solidified fiber discharged into the coagulation liquid is not particularly limited, but the molecular orientation is increased by aligning the molecular orientation of the protein, and the strength and elastic modulus of the fiber are improved. Therefore, 2 to 20 times is preferable. More preferably, it is 3 to 5 times.

  According to the present invention, a protein fiber having a high molecular orientation can be produced from a protein-containing dope.

It is a photograph of the cylindrical tube and hollow fiber used for the Example. FIG. 3 is a schematic diagram showing the action of the hollow fiber in Example 1. 3 is a schematic diagram of a process of Example 1. FIG. It is a polarization micrograph of a part of protein fiber f. It is a polarization micrograph of a part of protein fiber g. It is a polarization micrograph of a part of protein fiber h. It is a stereomicrograph of a part of protein fiber h. It is a graph of the birefringence of protein fiber. It is a graph of the relationship between the draw ratio of protein fiber, and tensile breaking strength. FIG. 6 is a schematic diagram showing the action of the hollow fiber in Example 2. It is a schematic diagram of the conventional spinning method.

  In the present invention, after setting the hollow fiber attached to the tip of a stainless steel cylindrical tube (nozzle) so that the outer peripheral surface and the tip opening are in the coagulation liquid, the dope was fed into the hollow fiber. Then, the protein in the dope was discharged into the coagulation liquid from the tip of the hollow fiber as a semi-coagulated fiber by the action of the coagulation liquid permeating the hollow fiber. Thereafter, the semi-solidified fiber is drawn and then solidified to obtain a protein fiber, which is a method for producing a fiber by wet spinning.

  Hereinafter, a method for producing a fiber by wet spinning in Example 1 will be described with reference to FIGS.

[1] Equipment and samples used The hollow fiber is a cylindrical straight tube porous PP (polypropylene) with an outer diameter of 0.5 mm and an inner diameter of 0.4 mm, and an absolute filtration accuracy of 0.05 μm. The hollow fiber of the brand name "CUNO nano shield filter tube" (model number: NSP005T15) of Sumitomo 3M Co. is used.
As the dope, a solution of Fabroin protein (molecular weight 60 KDa) dissolved in an aqueous solution of 7.5 M urea (additive) so as to be 13% by mass was used.
As the coagulation liquid, ethanol coagulation liquid A was used.

[2] Procedure [2-1] Preparation (1) The dope was filled in a syringe. When the production amount is large, a dedicated container for storing the dope (for example, an opening for allowing the dope to flow out on the bottom or the like) is used instead of the syringe.
(2) A stainless steel cylindrical tube (injection needle) having an inner diameter of 0.3 mm was attached to the syringe. When a dedicated container is used instead of the syringe, the cylindrical tube and this dedicated container are connected.
(3) As shown in FIG. 1, the hollow fiber was fitted on the cylindrical tube so as to extend 10 mm from the tip of the cylindrical portion, and the cylindrical tube and the hollow fiber were connected. The outer diameter of the cylindrical tube and the inner diameter of the hollow fiber were made substantially the same so that the dope would not leak from the connecting portion between the cylindrical tube and the hollow fiber.
(4) The syringe was set in the syringe pump, and the hollow fiber was set in a state immersed in the coagulation liquid A as shown in FIG.

[2-2] Spinning and Drawing (1) The syringe pump was operated at a set speed so that a certain amount of dope flowed through the cylindrical tube, and the dope was sent to the hollow fiber. When a dedicated container is used instead of the syringe, a certain amount of dope flows through the cylindrical tube using a gear pump or the like.
(2) As shown in FIG. 2, the coagulation liquid A penetrates into the hollow fiber, and the additive diffuses into the coagulation liquid A by its action. As a result, the protein becomes semi-coagulated due to the lower concentration of the additive. And, as shown in FIG. 3, after passing the fiber discharged into the coagulation liquid A from the tip opening of the hollow fiber through a drawing machine provided in the coagulation tank filled with the coagulation liquid A, I took it to the take-up roller provided outside.
(3) After the stretching of the semi-solidified fiber after being discharged to the coagulating liquid A by the rotation of the stretching roller of the stretching machine, the protein fiber obtained by coagulating the semi-solidified fiber is wound up. I wound up with.

[3] Protein fiber Four types of protein fibers a to c and e were produced according to Example 1. Moreover, protein fiber fh was manufactured with the manufacturing method which is not Example 1. FIG.
・ Protein fiber a
Using the manufacturing method of Example 1 above, the dope is sent to the cylindrical tube so that the discharge speed is 0.7 m / min, and the fiber in a semi-solid state discharged from the opening of the hollow fiber into the coagulation liquid A Was stretched by a stretching machine so that the stretching ratio was about 3 times (about 3 times when the length was discharged) to produce a protein fiber a.
・ Protein fiber b
A protein fiber b was produced in the same manner as the protein fiber a except that the stretching ratio was about 5 times.
・ Protein fiber c
A protein fiber c was produced in the same manner as the protein fiber a, except that the stretch ratio was approximately doubled.
・ Protein fiber e
A protein fiber e was produced in the same manner as the protein fiber a except that the stretch ratio was about 4 times.
・ Protein fiber f
The protein fiber f was manufactured by the method which does not perform post-drawing. Specifically, the dope is sent to a cylindrical tube so that the discharge speed is 0.6 m / min, and the protein dissolved in the dope is semi-solidified into the coagulating liquid A from the end opening of the hollow fiber. In addition, since it was discharged as it was not passed through a stretching machine, it was manufactured without performing post-stretching. In addition, since the post-stretching was not performed, the stretch ratio is set to 1 time (the length remains as it was discharged).
・ Protein fiber g
A protein fiber g was produced in the same manner as the protein fiber f except that the discharge speed was 0.7 m / min. In addition, since the post-drawing was not performed, the drawing rate is set to 1 time.
・ Protein fiber h
Protein fiber h was produced by a method not using a hollow fiber. Specifically, the dope is sent to the cylindrical tube so that the discharge speed is 0.6 m / min, and the protein dissolved in the dope is directly discharged into the coagulation liquid A from the tip of the cylindrical tube and stretched. Since it did not pass through the machine, it was manufactured without post-stretching. In addition, since the post-drawing was not performed, the drawing rate is set to 1 time.

  The protein fibers a, b, f, g, and h thus produced were measured for birefringence with a polarizing microscope equipped with a compensator. The measured values are shown in Table 1, and FIG. 8 is a graph of measured values. Indicates. In addition, microphotographs of protein fibers f, g, and h are shown in FIGS.

Here, the birefringence was determined as follows.
A compensator (Olympus “U-CTB”) was set on a polarizing microscope, and the stage was fixed at 45 ° from the extinction position. Then, the retardation value was obtained from the angle calculation by turning the compensator handle. A value obtained by dividing the retardation value by the fiber diameter was determined as a birefringence.

  Moreover, while measuring the tensile breaking strength about protein fiber ac, e, and g, while showing the measured value in Table 2, the graph of an extending | stretching rate and tensile breaking strength is shown in FIG. The tensile breaking strength was a value obtained by dividing the load immediately before breaking when it was pulled at a crosshead speed of 10 mm / min by the cross-sectional area of the fiber.

As shown in the photograph of FIG. 7, the protein fiber h spun without using hollow fibers had uneven fiber diameters. Therefore, when stretching in the coagulating liquid A, the fiber diameter was cut off from a small (thin) part, and good post-stretching could not be performed. This is because the protein dissolved in the dope is directly discharged into the coagulation liquid A from the opening at the end of the cylindrical tube, so that the protein immediately after the discharge flows in the coagulation liquid A in a dissolved state in the dope. This is because it is in a stable state and suddenly coagulates into fibers when there is a protein flowing in the coagulation liquid A.
Moreover, as shown in the photograph of FIG. 6, the protein fiber h was in a state in which the molecular arrangement was not uniform up to the inside of the fiber. This is because the hollow fiber is not used, so the speed at which urea (additive) is removed from the dope cannot be adjusted, and the protein aggregation speed cannot be adjusted. In the polarizing micrograph, the part where the molecules are oriented is bright and the part where the molecules are not oriented appears dark.

As shown in the photographs of FIGS. 4 and 5, the protein fiber spun using the hollow fiber was able to ensure the uniformity of the fiber diameter. This is because the protein dissolved in the dope is not directly discharged into the coagulation liquid A from the opening of the end of the cylindrical tube, but passes through the hollow fiber having a substantially uniform inner diameter. This is because urea (additive) is gradually removed from the dope due to the action of the coagulation liquid A infiltrated with (polypropylene), and the protein gradually coagulates into fibers in the hollow fiber.
Moreover, these protein fibers were in a state where the molecular arrangement was uniform (high molecular orientation) as shown in the photographs of FIGS. This is because the protein dissolved in the dope is passed through the hollow fiber, so that urea (additive) in the dope is removed by the action of the coagulation liquid A that has penetrated the wall surface (porous polypropylene) of the hollow fiber and the hollow fiber. This is due to the acceleration of shearing with the wall surface.

Protein fibers spun by a method using hollow fiber and post-stretching in coagulation liquid A have higher molecular orientation (higher molecular orientation results in higher birefringence. Table 1 and FIG. (See graph 8).
Further, the tensile strength at break increased due to the increase in molecular orientation (see the graphs in Table 2 and FIG. 9). In particular, the protein fibers a, b, and e that had been stretched 3 times or more had a value at least 3 times that of the protein fiber g that had not been stretched.

As described above, according to the fiber manufacturing method of Example 1, the dope is passed through the hollow fiber having the outer peripheral surface and the tip opening in the coagulating liquid, so that the protein fiber has a substantially uniform fiber diameter and high molecular orientation. Could be manufactured.
In addition, since the protein is discharged into the coagulation liquid A as a semi-coagulated fiber in which molecules are oriented to some extent, the fiber can be made difficult to collapse even in the coagulation liquid A.
In addition, the semi-coagulated state of the fibrous protein discharged into the coagulation liquid A could be changed by changing the length of the hollow fiber.
In addition, since the semi-coagulated protein fibers discharged into the coagulation liquid A have a strength that does not collapse in the coagulation liquid A, post-stretching can be performed in the coagulation liquid A, and the molecular orientation is further improved. It was possible to produce a protein fiber having a high molecular orientation and high strength.

  Next, a method for producing fibers by wet spinning in Example 2 will be described with reference to FIG.

This manufacturing method differs from the manufacturing method of Example 1 only in that a coagulating liquid having different solubility of urea (additive) is used on the proximal end side and the distal end side of the hollow fiber. Is the same.
Specifically, as coagulation liquid, coagulation liquid B made of methanol and coagulation liquid C made of 70% by volume methanol aqueous solution, which is a mixture of methanol and water with methanol added to 70% by volume. Different types of coagulant were used.
Then, as shown in FIG. 10, using a coagulation tank in which the inside of the tank is divided into two by a partition wall provided substantially in the center in the length direction of the hollow fiber, the coagulation liquid B is added to the coagulation tank on the proximal end side of the hollow fiber. After filling the coagulation liquid C into the coagulation layer on the distal end side of the hollow fiber, the protein is discharged into the coagulation liquid C from the opening at the tip of the hollow fiber as a semi-coagulated fiber, and then in the coagulation liquid C. Post-stretching was performed.

  According to the fiber production method of Example 2, in addition to the effects obtained by the fiber production method of Example 1, urea (additive) is gradually extracted from the dope with the coagulation liquid B, and the dope with the coagulation liquid C. It was possible to promote protein coagulation by completely extracting urea (additive) from the protein.

  In addition, this invention is not limited to the said Example, In the range which does not deviate from the meaning of invention, it can change suitably and can be actualized.

Claims (10)

  A tubular hollow fiber made of a porous semi-permeable membrane is set so that the outer peripheral surface and the tip opening are in the coagulation liquid, the protein dissolved in the dope is sent to the hollow fiber, and the hollow fiber penetrates By the action of the coagulation liquid, the protein is drawn into a semi-coagulated fiber that can be drawn and discharged into the coagulation liquid from the opening of the tip of the hollow fiber, and the semi-coagulated fiber discharged into the coagulation liquid A method for producing a fiber by wet spinning, characterized by obtaining a protein fiber by stretching and then coagulating.   The method for producing a fiber by wet spinning according to claim 1, wherein the semi-solidified fiber discharged into the coagulating liquid is drawn in the coagulating liquid.   The method for producing fibers by wet spinning according to claim 1 or 2, wherein the material of the semipermeable membrane is polypropylene.   The method for producing a fiber by wet spinning according to any one of claims 1 to 3, wherein the hollow fiber has a straight pipe shape.   The method for producing fibers by wet spinning according to claim 4, wherein the ratio of length / inner diameter of the hollow fiber is 200/1 to 20/1.   The method for producing fibers by wet spinning according to any one of claims 1 to 5, wherein a discharge speed is 0.6 to 3 m / min.   The method for producing a fiber by wet spinning according to any one of claims 1 to 6, wherein a drawing ratio for drawing the semi-solidified fiber is 2 to 20 times.   The method for producing a fiber by wet spinning according to any one of claims 1 to 7, wherein the protein has a molecular weight of 50 KDa or more.   The method for producing a fiber by wet spinning according to any one of claims 1 to 8, wherein one kind of coagulating liquid is used as the coagulating liquid.   As the coagulation liquid, two kinds of additives having different solubilities are added in the dope in order to dissolve the protein on the distal end side and the proximal end side with respect to the middle portion in the length direction of the hollow fiber. The method for producing a fiber by wet spinning according to any one of claims 1 to 8, wherein a coagulating liquid is used.