JP2008138316A - Twisted yarn and method for producing twisted yarn - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a twisted yarn having mechanical characteristics and a sufficient surface area, and to provide a method for producing the twisted yarn. <P>SOLUTION: The twisted yarn is obtained by converting filaments obtained by an electrostatic spinning method into the twisted yarn and carrying out drawing of the twisted yarn. Thereby, the twisted yarn is composed of the plurality of filaments having an aliphatic polyester as the main component. The average fiber diameter of a plurality of the filaments is ≥0.1 and ≤2 μm. A plurality of the filaments contain substantially no filament having a fiber diameter of ≥5 μm and the average angle formed by the filaments relative to the fiber axis direction is within 10°. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a twisted yarn and a method for producing a twisted yarn. More specifically, the present invention relates to a twisted yarn that is constituted by a plurality of filaments having a small fiber diameter and has mechanical characteristics and a sufficient surface area because the filaments are oriented in the fiber axis direction, and a method for producing the same.

  In the field of regenerative medicine, a fiber structure may be used as a base material when cells are cultured. And as a fiber structure, the structure which consists of the fiber which used the polyglycolic acid used for the surgical suture etc. as a raw material, for example is examined (refer nonpatent literature 1).

  However, the fiber structure using fibers obtained by a normal method as described in Non-Patent Document 1 has a small effective area to which cells can adhere because the fiber diameter is too large. . Therefore, in order to increase the surface area for culturing, a fiber structure having a smaller fiber diameter has been desired.

  Here, as a method for producing a fiber structure having a small fiber diameter, an electrostatic spinning method is already known (see Patent Documents 1 and 2). The electrostatic spinning method is a method of forming a fiber structure by introducing a liquid, for example, a solution containing a fiber-forming substance into an electric field and causing the liquid to flow toward an electrode. Usually, the fiber-forming substance is cooled (e.g., when the spinning liquid is solid at room temperature), chemically cured (treatment with curing steam, etc.), solvent evaporation, etc. To solidify and form fibers. The obtained fiber is collected on an appropriately arranged electrode to form a fiber structure, and is peeled off from the electrode if necessary.

  In addition, it is already known that a fiber structure obtained by an electrospinning method is used as a substrate for culturing cells (see Non-Patent Document 2). In Non-patent Document 2, smooth muscle cells are cultured on a fiber structure made of polylactic acid formed by an electrospinning method, and the regeneration of blood vessels is studied.

  However, when producing a fiber structure by an electrospinning method, an electrode for collecting the fibers is required, so that many of the obtained fiber structures are planar, and therefore can be produced. The body shape was limited. On the other hand, there are tissues of various structures in the living body, and the presence rate of cells as linear bodies is particularly large. Therefore, there has been a great demand for fibers having a small fiber diameter obtained by an electrospinning method and capable of forming a form other than a planar body.

  In response to this requirement, Patent Document 3 proposes a twisted yarn that is composed of a filament having a small average fiber diameter and substantially does not include a filament having a fiber diameter of a certain size or more. The twisted yarn described in Patent Document 3 can be used as a suture as it is, and a structure having a form other than a planar body can be created by processing such as knitting.

JP-A 63-145465 JP 2002-249966 A Japanese Patent Laying-Open No. 2005-226210 Noriya Ohno, Director of Translation by Masao Aizawa, “Regenerative Medicine”, NTS Corporation, January 31, 2002, p. 258 Joel D. Stitzel, Kristin J. Pawlowski, Gary E. Wnek, David G. Simpson, Gary L. Bowlin, “Journal of Biomaterials Applications” ), SAGE Publications, 2001, 16, pages 22-33.

  However, in Patent Document 3, although it is possible to obtain a twisted yarn composed of filaments having a small fiber diameter to a certain extent, the orientation of the filaments constituting the twisted yarn in the fiber axis direction is still weak. It was still insufficient for use in sutures and the like in terms of mechanical properties.

  Moreover, in the fiber structure used for cell culture, it is preferable that the effective area to which cells can adhere is large. According to the twisted yarn in Patent Document 3, a structure having a certain surface area can be produced, but the demand for improving the surface area is not exhausted, and further improvement has been demanded.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a twisted yarn having mechanical properties and a sufficient surface area, and a method for producing the same.

  The present inventors have made extensive studies in view of the above problems. As a result, the filament obtained by the electrospinning method is used as a twisted yarn, and the twisted yarn is stretched to have a sufficient surface area because it is constituted by a plurality of filaments having a small fiber diameter. It has been found that a twisted yarn with improved mechanical properties can be obtained because the filaments are oriented in the fiber axis direction, and the present invention has been completed.

  That is, the present invention is a twisted yarn composed of a plurality of filaments mainly composed of aliphatic polyester, the average fiber diameter of the plurality of filaments is 0.1 μm or more and 2 μm or less, the plurality of filaments, It is a twisted yarn that does not substantially contain a filament having a fiber diameter of 5 μm or more and that has an average angle of 10 ° or less with respect to the fiber axis direction.

  In another aspect of the present invention, there are provided a fiber forming composition preparation step of preparing a fiber forming composition containing an aliphatic polyester and a solvent, and a fiber by ejecting the fiber forming composition by an electrostatic spinning method. A spinning process for obtaining a fiber aggregate by accumulating the fibers, a drawing process for drawing a plurality of fibers from one end of the fiber aggregate to form a fiber bundle, and twisting the fiber bundle A twisted yarn manufacturing method comprising: a twisting step for forming a twisted fiber bundle; a winding step for winding the twisted fiber bundle to obtain a twisted yarn; and a stretching step for drawing the twisted yarn to obtain a stretched twisted yarn.

  The twisted yarn of the present invention is composed of a plurality of filaments having a small fiber diameter, and the filaments are oriented in the fiber axis direction. For this reason, the fiber structure formed from the twisted yarn of the present invention has a surface area larger than that of the conventional structure and further has sufficient mechanical properties. As a result, the obtained fiber structure can be suitably used as a substrate for cell culture.

  Moreover, since the twisted yarn of the present invention can be used as a suture as it is, it is very useful as a suture with excellent biocompatibility depending on the selection of materials. Moreover, various structures can be formed by performing processing such as knitting using the twisted yarn of the present invention. Therefore, according to the twisted yarn of the present invention, it is possible to easily produce a structure having a shape other than a planar body, which has been difficult to obtain by the conventional electrospinning method. Furthermore, it can also be used in combination with other members, whereby a structure satisfying the requirements can be easily obtained.

Hereinafter, the present invention will be described in detail.
<Twisted yarn>
The twisted yarn of the present invention is a twisted yarn composed of a plurality of filaments whose main components are aliphatic polyesters, and the average fiber diameter of the plurality of filaments is 0.1 μm or more and 2 μm or less. In addition, the filament diameter does not substantially include a filament having a fiber diameter of 5 μm or more, and the average value of the angle formed by the filament with respect to the fiber axis direction is within 10 °.
Here, “twisted yarn” in the present invention means a substantially cylindrical fiber structure in which multifilaments are ground and twisted.

[Material of twisted yarn]
The plurality of filaments constituting the twisted yarn of the present invention are required to be mainly composed of aliphatic polyester from the viewpoint of excellent biocompatibility and handleability. Here, “main component” means that the aliphatic polyester is in the range of more than 50% by mass to 100% by mass with respect to the entire material constituting each filament.
Examples of such aliphatic polyester include aliphatic groups such as polylactic acid, polyglycolic acid, polylactic acid-polyglycolic acid copolymer, polycaprolactone, polybutylene succinate, polyethylene succinate, and copolymers thereof. Examples include polyester. Among these, from the viewpoint of biocompatibility, it is preferably at least one selected from the group consisting of polylactic acid, polyglycolic acid, and polylactic acid-polyglycolic acid copolymer. From the viewpoint, polylactic acid is particularly preferable.
In addition, the aliphatic polyester used as the main component of the filament which comprises the twisted thread | yarn of this invention can also blend and use 2 or more types not only individually by 1 type.

[Types of filaments constituting twisted yarn]
Moreover, the filament which comprises the twisted yarn of this invention can also be comprised from several different types of filaments according to the request | requirement not only 1 type. Here, “different types of filaments” means both the case where the form of the filament is different and the case where the composition of the filament is different.
When the form of the filament is different, for example, the case where the fiber diameter of the filament is different, the case where the surface structure of the filament is different, and the case where the cross-sectional structure of the filament is different are included.
Moreover, when the composition of a filament differs, the case where the kind of aliphatic polyester differs, or the case where the structures of arbitrary components, such as an additive, differ are included, for example.

[Average fiber diameter of multiple filaments]
Next, the average fiber diameter of the filaments constituting the twisted yarn will be described. The average fiber diameter of the plurality of filaments constituting the twisted yarn of the present invention is 0.1 μm or more and 2 μm or less. When the average fiber diameter exceeds 2 μm, the specific surface area of the obtained twisted yarn becomes too small, and as a result, the number of cells that can be cultured decreases. Moreover, if the average fiber diameter of a filament is 0.1 micrometer or more, the mechanical characteristic of the twisted yarn obtained will become sufficient. In addition, the preferable range of the average fiber diameter of the filament which comprises twisted yarn is 0.2 micrometer or more and 1.5 micrometers or less, and a more preferable range is 0.2 micrometer or more and 1 micrometer or less.

[Filaments with a fiber diameter of 5 μm or more]
Next, it will be described that a filament having a fiber diameter of 5 μm or more is not substantially contained. In the present invention, “substantially free” means that a filament having a fiber diameter of 5 μm or more is not observed when an arbitrary portion of the twisted yarn is observed in an observation with an electron microscope.
When the filaments constituting the twisted yarn of the present invention include filaments having a fiber diameter of 5 μm or more, the specific surface area of the obtained twisted yarn is reduced, and the number of cells that can be cultured is preferably reduced. This is also undesirable because flexibility suitable for the above is impaired.
In order to obtain flexibility suitable for cell culture, it is more preferable that a filament having a fiber diameter of 3 μm or more is not substantially contained.

[Orientation in the fiber axis direction]
Next, the fact that the filament is oriented in the fiber axis direction will be described. The plurality of filaments constituting the twisted yarn of the present invention have high orientation in the fiber axis direction, and the average angle formed by the filaments with respect to the fiber axis direction is within 10 °. In the twisted yarn of the present invention, since the plurality of filaments constituting the twisted yarn are oriented in the fiber axis direction, the proportion of filaments contributing to mechanical properties increases, and as a result, the mechanical properties of the twisted yarn are improved. To do. In the twisted yarn of the present invention, the average value of the angle formed by the filament with respect to the fiber axis direction is preferably within 5 °, more preferably within 3 °.
The standard deviation value of the angle formed by the filament with respect to the fiber axis direction is preferably within 10 °, and more preferably within 5 °.

[Diameter of twisted yarn]
The diameter of the twisted yarn of the present invention is not particularly limited as long as the cells to be cultured can be cultured, but is preferably in the range of 0.01 mm to 1 mm, more preferably The range is from 0.05 mm to 0.5 mm.

[Elastic modulus of twisted yarn]
The elastic modulus of the twisted yarn of the present invention is preferably in the range of 1 GPa to 10 GPa. If it is less than 1 GPa, it is not preferable because problems such as breakage during handling and low dimensional stability occur. On the other hand, when it exceeds 10 GPa, the affinity with a cell tissue such as a living body is lowered, which is not preferable. More preferably, it is the range of 3 GPa or more and 7 GPa or less.

[Stress at break of twisted yarn]
The breaking stress of the twisted yarn of the present invention is preferably in the range of 0.5 cN / dtex to 5 cN / dtex. When it is less than 0.5 cN / dtex, it is not preferable because problems such as breakage during handling and low dimensional stability occur. On the other hand, when it exceeds 5 cN / dtex, it is not preferable because the affinity with a cell tissue such as a living body is lowered. More preferably, it is the range of 1 cN / dtex or more and 3 cN / dtex or less.

<Method for producing twisted yarn>
An embodiment for producing the twisted yarn of the present invention will be described.
As a method for producing the twisted yarn of the present invention, any method can be adopted as long as it can obtain a twisted yarn that satisfies the above-mentioned requirements at the same time, but a composition for forming a fiber comprising an aliphatic polyester and a solvent. A fiber-forming composition preparation step, a spinning step of obtaining fibers by ejecting the fiber-forming composition by an electrostatic spinning method, and a cumulative step of accumulating the fibers to obtain a fiber aggregate A drawing step of drawing a plurality of fibers from one end of the fiber assembly to form a fiber bundle, a twisting step of twisting the fiber bundle to form a twisted yarn, and a drawing step of drawing the twisted yarn to obtain a drawn twisted yarn And a method for producing a twisted yarn comprising:

In the present invention, a winding step may optionally be included. The winding process is carried out by continuously performing the stretching process after the twisting process and winding the obtained stretched yarn, or winding the twisted thread obtained after the twisting process. May be carried out, followed by a stretching step, or both.
Below, the component of the composition for fiber formation used for one aspect | mode of the preferable manufacturing method for obtaining the twisted yarn of this invention, and each manufacturing process are demonstrated.

[Configuration of Fiber Forming Composition]
The fiber-forming composition used in one embodiment of a preferred production method for obtaining the twisted yarn of the present invention will be described. The fiber forming composition used as a preferred embodiment is a composition containing an aliphatic polyester and a solvent as essential components. The structure of the fiber forming composition will be described below.

[Aliphatic polyester]
The aliphatic polyester in the fiber-forming composition used as a preferred embodiment is an aliphatic polyester that is a material for the above-described twisted yarn. That is, examples of the aliphatic polyester used include polylactic acid, polyglycolic acid, polylactic acid-polyglycolic acid copolymer, polycaprolactone, polybutylene succinate, polyethylene succinate, and copolymers thereof. Of aliphatic polyesters. Among these, from the viewpoint of biocompatibility, it is preferably at least one selected from the group consisting of polylactic acid, polyglycolic acid, and polylactic acid-polyglycolic acid copolymer. From the viewpoint, polylactic acid is particularly preferable.
In addition, not only one type of aliphatic polyester but also two or more types can be blended and used.

〔solvent〕
The solvent used as a preferred embodiment may be a single solvent or a mixed solvent in which a plurality of solvents are combined. The solvent used in one embodiment of a preferred production method for obtaining the twisted yarn of the present invention is not particularly limited as long as it can dissolve the above aliphatic polyester, but is spun by an electrostatic spinning method. If it evaporates easily in the step of forming, fibers can be easily formed. Therefore, it is preferable to use a volatile solvent. Here, “volatile” in the present invention means a boiling point of 165 ° C. or lower.
Examples of such solvents include acetone, chloroform, ethanol, propanol, isopropanol, methanol, toluene, tetrahydrofuran, benzene, 1,4-dioxane, methylene chloride, carbon tetrachloride, cyclohexane, cyclohexanone, pyridine, trichloroethane, acetic acid, Examples include formic acid, hexafluoroisopropanol, hexafluoroacetone, N, N-dimethylformamide, acetonitrile, 1,3-dioxolane, methyl ethyl ketone, and a mixed solvent of these solvents.
Moreover, the solvent used for this invention may be not only 1 type independent but the mixed solvent which mixed 2 or more types.

  In the present invention, it is preferable to use a solvent containing a halogenated hydrocarbon and / or alcohol from the viewpoints of excellent handleability and excellent solubility. Among these, it is particularly preferable to use one selected from the group consisting of methylene chloride, methanol, ethanol, and a mixed solvent thereof from the viewpoint of good spinnability.

[Other ingredients]
In a preferred embodiment of the production method for obtaining the twisted yarn of the present invention, fibers can be formed from the fiber-forming composition, and components other than the above essential components are used for fiber formation as long as they do not exceed the gist of the present invention. You may make it contain as an arbitrary component of a composition.
Examples of such optional components include resins and additives other than aliphatic polyester. It is also possible to add functionality to the twisted yarn by blending a drug. As a drug to be used, not only a low molecular compound drug having high compatibility with aliphatic polyester, but also a compound with low compatibility, by using a fiber-forming composition in which drug granules are dispersed, The drug can be dispersed in the filament constituting the twisted yarn. When the filament constituting the twisted yarn of the present invention contains a drug, it becomes a twisted yarn having a function of sustained drug release.

[Fiber-forming composition preparation step]
In the fiber forming composition preparation step, a fiber forming composition containing an aliphatic polyester and a solvent is prepared.
In an embodiment of a preferred production method for obtaining the twisted yarn of the present invention, first, an aliphatic polyester and a solvent are mixed to obtain a fiber forming composition. In addition, the composition for fiber formation obtained becomes a uniform solution or mixed solution. The mixing method is not particularly limited, and a known method such as stirring can be employed.
The concentration of the aliphatic polyester in the fiber forming composition is preferably 1% by mass or more and 30% by mass or less. When the concentration of the aliphatic polyester is less than 1% by mass, it is difficult to form a fiber because the concentration is too low. On the other hand, when the concentration is larger than 30% by mass, the fiber diameter of the obtained fiber is not preferable. A more preferable concentration of the aliphatic polyester is in a range of 2% by mass or more and 20% by mass or less with respect to the entire fiber-forming composition.

  In the present invention, from the viewpoint of improving the stability of the solution (or dispersion) of the fiber forming composition and the spinning stability, or from the viewpoint of imparting functionality to the obtained twisted yarn, the fiber forming composition. In the case of adding other optional components, the optional component may be added before the aliphatic polyester is mixed with the solvent or after the aliphatic polyester is mixed. Examples of optional components include emulsions, organic or inorganic powders, drugs, and the like.

[Spinning process]
In the spinning step, fibers are obtained by ejecting the fiber-forming composition by an electrostatic spinning method. The spinning method and spinning device in the spinning process will be described below.

[Spinning method]
In the spinning process of a preferred embodiment, fibers are produced by an electrostatic spinning method. Here, the “electrostatic spinning method” refers to discharging a solution or dispersion containing a fiber-forming substrate or the like into an electrostatic field formed between the electrodes, and directing the solution or dispersion to the electrodes. This is a method of forming a fibrous substance by spinning.
An arbitrary method can be adopted as a method of ejecting the fiber-forming composition into the electrostatic field. For example, the fiber-forming composition is supplied to the nozzle and placed at an appropriate position in the electrostatic field, and the nozzle The fiber-forming composition is twisted by an electric field. Here, the fibers are formed between the nozzle and the electrode by eliminating the charge from the fiber forming composition while the fiber forming composition is drawn toward the electrode.
If the room temperature is normal, the solvent contained in the fiber-forming composition completely evaporates until the fiber reaches the collection surface, but if the solvent evaporation is insufficient, The spinning atmosphere temperature may be controlled or the spinning may be performed under reduced pressure conditions. The temperature at the time of spinning depends on the evaporation behavior of the solvent contained in the fiber-forming composition and the viscosity of the fiber-forming composition (spinning solution), but is usually in the range of 0 ° C to 50 ° C. Is preferred.

The method for eliminating the charge from the fiber forming composition is not particularly limited as long as the charge of the fiber forming composition can be eliminated to form the fiber. For example, the charge is eliminated using an ionizer. The method can be preferably adopted. An “ionizer” is a device that can generate an ion with a built-in ion generator and discharge the ion to a charged material, thereby eliminating the charge from the charged material. When an ionizer is used in the spinning process, it is not particularly limited as long as it can form fibers, but an ion generator that generates ions by applying a high voltage to a built-in discharge needle is provided. It can preferably be employed.
The fibrous material formed in the spinning step includes not only a state in which the solvent and the like contained in the fiber-forming composition are completely distilled off, but also a state in which the fibrous material remains in the fibrous material. In addition, the obtained fiber may be further subjected to heat treatment or chemical treatment.

[Spinning equipment]
Next, an apparatus used in the electrostatic spinning method will be described.
The electrode for forming the electrostatic field may be any material such as a metal, an inorganic material, or an organic material as long as it exhibits conductivity. Alternatively, a thin film made of a metal, an inorganic material, an organic material, or the like having conductivity may be provided over an insulator.
The electrostatic field used in the electrostatic spinning method is formed between a pair or a plurality of electrodes, and a high voltage may be applied to any electrode that forms the electrostatic field. This includes, for example, the case of using two high voltage electrodes having different voltage values (for example, 15 kV and 10 kV) and one electrode connected to the ground, or a total of more than three electrodes. Including the case of using.

Hereinafter, the electrostatic spinning method will be described more specifically with reference to FIG.
The fiber-forming composition holding tank 3 has a cylindrical syringe shape. An injection needle-like fiber-forming composition ejection nozzle 1 is installed at the tip of the fiber-forming composition holding layer 3, and appropriate means such as high voltage generation is provided in the fiber-forming composition ejection nozzle 1. A voltage is applied by the vessel 5 to guide the fiber forming composition 2 to the tip of the fiber forming composition ejection nozzle 1. The tip of the fiber forming composition ejection nozzle 1 is arranged at an appropriate distance from the grounded electrode 4 and ionizer 6. Then, the fiber forming composition 2 is ejected from the tip portion of the fiber forming composition ejection nozzle 1, and fibers are formed between the tip portion of the fiber forming composition ejection nozzle 1 and the ionizer 6.

  When supplying the fiber-forming composition 2 into the electrostatic field from the fiber-forming composition jet nozzle 1, several nozzles can be used in parallel to increase the fiber production rate. The distance between the electrodes (fiber-forming composition ejection nozzle 1 and electrode 4) depends on the charge amount, nozzle size, ejection amount of the fiber-forming composition, concentration of the fiber-forming composition, etc., but is 10 kV. A distance of 5 to 20 cm is appropriate for the case. The applied electrostatic potential is generally in the range of 3 to 100 kV, preferably 5 to 50 kV, more preferably 5 to 30 kV. The desired potential can be generated by any appropriate method known in the art.

[Cumulative process]
In the accumulation process, the fibers formed in the spinning process are accumulated to obtain a fiber assembly. Specifically, a fibrous aggregate is obtained by accumulating (stacking) the fibrous material formed in the spinning process on an electrode or a collecting device having a collecting surface.
Therefore, although a planar fiber assembly can be obtained by using a flat surface as the collection surface, a fiber assembly having a desired shape can be produced by changing the shape of the collection surface. In addition, when the fiber aggregates are concentrated (stacked) in one place on the collection surface and the uniformity is low, the collection surface can be shaken or rotated.
Further, in the same manner as described above, the fiber aggregate is not only in a state where the solvent and the like contained in the fiber-forming composition are completely distilled off to form an aggregate, but also the solvent and the like are contained in the fibrous substance. The state which remains as it is is also included.

[Drawing process]
In the drawing step, a plurality of fibers are drawn from one end of the fiber assembly formed in the accumulation step to form a fiber bundle. In the method for producing a twisted yarn of the present invention, a fiber bundle can be continuously formed by pulling out one end of the fiber assembly obtained by the accumulating step, by entanglement of fibers.
The method of pulling out a plurality of fibers from the fiber assembly is not particularly limited, and for example, a method of pulling up with a winder or the like can be employed.

[Twisting process]
In the twisting process, the fiber bundle drawn in the drawing process is twisted to obtain a twisted yarn. The method for twisting the fiber bundle is not particularly limited, and various known methods can be employed. For example, a method of rotating the collection surface on which the fibers are accumulated in the accumulation process at a constant speed can be mentioned.
Further, the number of twists is not particularly limited as long as it can be oriented in the fiber axis direction in the drawing step described later, and can be appropriately selected according to the use for which the twisted yarn is used.

[Stretching process]
In the stretching step, a stretched yarn is obtained by stretching the twisted yarn obtained in the twisting step. By further stretching the twisted yarn, the average fiber diameter can be reduced, and the filaments constituting the twisted yarn can be aligned and oriented in the fiber axis direction.
The stretching method is not particularly limited, and a known method can be employed. In the present invention, it is preferable to stretch using a known stretching apparatus while heating. The stretching temperature can be appropriately selected depending on the type of aliphatic polyester to be used. In the case of polylactic acid, it is preferably in the range of 70 ° C. or higher and 110 ° C. or lower.
As for the draw ratio, any ratio can be selected as long as the twisted yarn of the present invention is obtained, but in order to obtain a twisted yarn having sufficient mechanical properties for handling, the draw ratio is set to 3 times or more. It is preferable. More preferably, it is in the range of 5 to 10 times.

[Winding process]
The winding process is a process of winding the obtained twisted yarn or drawn twisted yarn. In the present invention, the stretching process is carried out continuously after the twisting process, and not only when the winding process is performed on the obtained stretched twisted yarn, but also the winding process is performed after the twisting process, Thereafter, the stretching step may be performed, or both.
The winding method is not particularly limited, and a known method can be adopted, and examples thereof include a method of continuously winding at a constant speed using a winding roller or the like.

[Twisted yarn production equipment]
As a device for producing the twisted yarn of the present invention, any device can be adopted as long as it is a production device capable of obtaining a twisted yarn that satisfies the above-mentioned requirements at the same time. As one aspect of a preferable production apparatus for obtaining the twisted yarn of the present invention, a fiber forming composition supply apparatus for supplying a fiber forming composition (spinning solution) to the nozzle tip, and the fiber forming composition from the nozzle tip A fiber manufacturing apparatus for producing fibers by ejecting the fibers, a fiber capturing apparatus for capturing the fibers to form a fiber aggregate, a twisting apparatus for drawing a fiber bundle from the fiber aggregate and twisting the fiber bundle, and Examples include a winding device that winds a twisted fiber bundle and a stretching device that stretches the wound fiber bundle.

  A preferred embodiment as an apparatus for producing the twisted yarn of the present invention will be specifically described with reference to FIG. The anti-static fiber production apparatus (up to the spinning process) is as described above for the spinning apparatus. Here, the apparatus after the fiber formation (spinning process) by the electrostatic spinning method will be described.

  The fiber capturing device 7 is installed between the tip portion of the fiber forming composition ejection nozzle 1 and the ionizer 6, and the formed fibers are accumulated on the fiber capturing device 7 to form a fiber assembly. . Next, a plurality of fibers are pulled out from one end of the accumulated fiber assembly using a winding roller 11 to form a fiber bundle, and the fiber capturing device 7 is rotated relative to the winding roller 11 to rotate the fiber. The bundle is twisted to form a twisted fiber bundle, the twisted fiber bundle is wound up by a winding roller 11 to be a twisted yarn, and the obtained twisted yarn is stretched by a stretching device 12 to obtain a stretched twisted yarn.

  Here, as the fiber capture device 7, for example, a tube and a circular support are prepared, and the tube is made arcuate, and both ends of the tube are joined on the circumference of the circular support. What was made into the target shape can be used. In addition, the fiber capture | acquisition apparatus 7 in FIG. 1 has described the example (refer FIG. 2) using three tubes. However, the shape of the fiber capture device 7 is not particularly limited as long as it has a function of capturing fibers (entangles or hooks fibers). For example, a combination of plates or the like is used as the fiber supplement device 7. Can also be used.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these unless it exceeds the gist.

<Measurement and evaluation method>
In the examples, the following items were measured and evaluated by the following methods.
[Average fiber diameter of twisted yarn]
Ten locations were randomly selected from the obtained twisted yarn. The selected part was photographed (magnification: 200 times) with a scanning electron microscope (manufactured by Hitachi, model: S-2400), and in the obtained photographic diagram, when the twisted cross section is a circle, the diameter is the fiber diameter. In the case of an ellipse, the fiber diameter (n = 10) was measured with the average of the long and short diameters as the fiber diameter, and the average value of all these (n = 10) was taken as the average fiber diameter of the twisted yarn.

[Observation of average fiber diameter of filament and fiber having fiber diameter of 5 μm or more]
The surface of the obtained twisted yarn was photographed (magnification: 2000 or 8000 times) with a scanning electron microscope (manufactured by Hitachi, model: S-2400), and a photograph was obtained. Twenty spots were selected at random from the obtained photograph and the filament diameter was measured. The average value of all the measurement results of the fiber diameter (n = 20) was determined to obtain the average fiber diameter of the filament, and it was confirmed whether or not there was a fiber having a fiber diameter of 5 μm or more.

[Filament orientation]
The surface of the obtained twisted yarn was photographed with a scanning electron microscope (manufactured by Hitachi, Ltd., model: S-2400) so that the longitudinal direction of the photographic diagram was parallel to the fiber axis direction (magnification: 2000 or 8000 times). The angle of the filament with respect to the fiber axis direction was measured for all the filaments observable in the obtained photographic diagram, and the average and standard deviation of the angles obtained were calculated.

[Elastic modulus of twisted yarn, stress at break]
Ten locations were randomly selected from the obtained twisted yarns, and the selected locations were subjected to a tensile test using a tensile tester (ORIENTEC, model: RTC-1225A). The average value (n = 5) of the obtained elastic modulus was the elastic modulus of the twisted yarn, and the average value (n = 5) of the breaking point stress was the breaking point stress of the twisted yarn.

<Example 1>
[Preparation of fiber-forming composition]
1 part by mass of polylactic acid (manufactured by Shimadzu Corporation, trade name: Lacty 9031), 3 parts by mass of ethanol (manufactured by Wako Pure Chemical Industries, grade: special grade), 6 parts by mass of methylene chloride (manufactured by Wako Pure Chemical Industries, grade: special grade) The parts were mixed at room temperature (25 ° C.) to prepare a fiber-forming composition.

[Spinning process / Cumulative process]
The fiber forming composition was ejected using the apparatus shown in FIG. 1 to obtain a fiber assembly. Various settings in the apparatus are as follows.
Inner diameter of fiber forming composition jet nozzle 1: 0.8 mm
Voltage: 15kV
Height from the fiber forming composition ejection nozzle 1 to the apex of the fiber capturing device 7: 5 cm, horizontal distance: 10 cm
Distance from the center of the fiber capture device 7 to the electrode 4: 10 cm
Fiber capture device 7 diameter: 10 cm, height: 22 cm

[Drawing process, twisting process, winding process]
Using the winding roller 11, a plurality of fibers are drawn from one end of the fiber assembly obtained above to form a fiber bundle, and the fiber bundle is twisted by rotating the fiber supplement device 7 to twist the fiber bundle. Then, it was wound up by the winding roller 11. Various settings in the apparatus are as follows.
Distance from the top of the fiber capture device 7 to the take-up roller 11: 25 cm
Rotation speed of the fiber supplement device 7: 300 rpm
Winding speed of the winding roller 11: 1.5 m / min

[Stretching process]
Finally, with respect to the twisted fiber bundle wound in the winding process, a stretching process was performed using the stretching device 12 under the following conditions.
Stretching temperature: 100 ° C
Stretch ratio: 8 times

[Measurement / Evaluation]
The obtained twisted yarn had an average fiber diameter of 0.1 mm and a fineness of 79 dtex. Moreover, the average fiber diameter of the filament which comprises twisted yarn is 440 nm, and the fiber whose fiber diameter is 5 micrometers or more was not observed. The average angle representing the degree of orientation was 0.8 °, the standard deviation value was 1.6 °, the elastic modulus of the twisted yarn was 4.8 GPa, and the breaking stress of the twisted yarn was 1.7 cN / dtex.

<Comparative Example 1>
A twisted fiber bundle was obtained in the same manner as in Example 1 except that the stretching step was not performed.
[Measurement / Evaluation]
The resulting twisted fiber bundle had an average fiber diameter of 0.7 mm and a fineness of 598 dtex. Moreover, the average fiber diameter of the filament which comprises a twisted fiber bundle is 1740 nm, and the fiber whose fiber diameter is 5 micrometers or more was not observed. The average value representing the degree of orientation was 16.3 °, the standard deviation value was 9.1 °, the elastic modulus of the twisted fiber bundle was 0.7 GPa, and the stress at break of the twisted fiber bundle was 0.2 cN / dtex. It was.

It is the figure which showed typically the manufacturing apparatus for manufacturing the twisted yarn of this invention. It is the figure which showed typically a mode that the fiber capture | acquisition apparatus 7 of FIG. 1 was seen from upper part. It is the photograph figure obtained by image | photographing (400 times) the surface of the twisted yarn obtained by operation of Example 1 with a scanning electron microscope so that a longitudinal direction may become horizontal with a fiber axis direction. It is the photograph figure obtained by image | photographing with a scanning electron microscope (8000 time) so that the surface of the twisted yarn obtained by operation of Example 1 may become horizontal with a fiber axis direction. It is the photograph figure obtained by image | photographing (100 times) the surface of the twisted yarn obtained by operation of the comparative example 1 with a scanning electron microscope so that a vertical direction might become horizontal with a fiber axis direction. It is the photograph figure obtained by image | photographing (2000 times) the surface of the twisted yarn obtained by operation of the comparative example 1 with a scanning electron microscope so that a vertical direction might become horizontal with a fiber axis direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fiber formation composition ejection nozzle 2 Fiber formation composition 3 Fiber formation composition holding tank 4 Electrode 5 High voltage generator 6 Ionizer 7 Fiber capture device
8 Motor 9 Rotating shaft 10 Transmission 11 Winding roller 12 Stretching device

Claims (7)

A twisted yarn composed of a plurality of filaments mainly composed of aliphatic polyester,
The average fiber diameter of the plurality of filaments is 0.1 μm or more and 2 μm or less,
The plurality of filaments are twisted yarns that do not substantially include a filament having a fiber diameter of 5 μm or more, and that an average value of angles formed by the filaments with respect to the fiber axis direction is within 10 °.   The twisted yarn according to claim 1, wherein the elastic modulus is 1 GPa or more and 10 GPa or less.   The twisted yarn according to claim 1 or 2, wherein the aliphatic polyester is at least one selected from the group consisting of polylactic acid, polyglycolic acid, and a polylactic acid-polyglycolic acid copolymer. A fiber-forming composition preparation step of preparing a fiber-forming composition comprising an aliphatic polyester and a solvent;
A spinning step of obtaining fibers by ejecting the fiber-forming composition by an electrostatic spinning method;
A cumulative step of accumulating the fibers to obtain a fiber aggregate;
A drawing step of drawing a plurality of fibers from one end of the fiber assembly to form a fiber bundle;
A twisting process in which the fiber bundle is twisted into a twisted yarn; and
And a drawing step of drawing the twisted yarn to obtain a drawn twisted yarn.   The method for producing a twisted yarn according to claim 4, wherein the aliphatic polyester is at least one selected from the group consisting of polylactic acid, polyglycolic acid, and a polylactic acid-polyglycolic acid copolymer.   The method for producing a twisted yarn according to claim 4 or 5, wherein the solvent is a volatile solvent.   The method for producing a twisted yarn according to any one of claims 4 to 6, wherein the solvent contains a halogenated hydrocarbon and / or an alcohol.