CN114481353A - Polyglycolic acid fiber and method for producing same - Google Patents
Polyglycolic acid fiber and method for producing same Download PDFInfo
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- CN114481353A CN114481353A CN202111181995.2A CN202111181995A CN114481353A CN 114481353 A CN114481353 A CN 114481353A CN 202111181995 A CN202111181995 A CN 202111181995A CN 114481353 A CN114481353 A CN 114481353A
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Images
Classifications
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
- D01F6/58—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products
- D01F6/62—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyesters
- D01F6/625—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyesters derived from hydroxy-carboxylic acids, e.g. lactones
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/08—Melt spinning methods
Landscapes
- Engineering & Computer Science (AREA)
- Textile Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Mechanical Engineering (AREA)
- Artificial Filaments (AREA)
Abstract
The present invention has been made to solve the above problems, and an object of the present invention is to provide a polyglycolic acid fiber having low heat shrinkability and easy hydrolyzability. The invention provides a polyglycolic acid fiber, which has the following three characteristics: (A) the crystallinity is more than 20%; (B) birefringence 35X 10‑3The above; and (C) an amorphous orientation coefficient of 0.30 or less.
Description
Technical Field
The present invention relates to a polyglycolic acid fiber and a method for producing the same.
Background
Polyglycolic acid, which is a biodegradable aliphatic polyester, is known to have excellent mechanical properties and gas barrier properties. Polyglycolic acid is also used as a biocompatible material for medical materials such as bioabsorbable sutures. In recent years, polyglycolic acid has been used in a wide range of applications, and is used for members used in petroleum gas excavation work, for example, by utilizing the high mechanical properties and hydrolysis properties of polyglycolic acid.
As a method for producing polyglycolic acid fibers, a direct spinning and drawing method in which a spinning step and a drawing step are performed as a series of processes has been generally considered as a spinning method suitable for producing polyglycolic acid fibers (for example, see patent document 1).
Documents of the prior art
Patent document
Patent document 1: international publication No. 2010/143526
Disclosure of Invention
Problems to be solved by the invention
In general, materials for industrial use represented by fibers are sometimes required to have a low heat shrinkage rate. However, polyglycolic acid fibers manufactured using the prior art as described above have a high heat shrinkage rate. It is also known that polyglycolic acid fibers are characterized by having hydrolysis properties, and further, are required to have hydrolysis properties suitable for the application, such as easy hydrolysis.
An object of one embodiment of the present invention is to realize a polyglycolic acid fiber having low heat shrinkability and easy hydrolyzability.
Means for solving the problems
In order to solve the above problems, a polyglycolic acid fiber according to one aspect of the present invention has the following properties: (A) the crystallinity is more than 20 percent; (B) birefringence 35X 10-3The above; and (C) an amorphous orientation coefficient of 0.30 or less.
In order to solve the above problems, a method for producing polyglycolic acid fibers according to one aspect of the present invention includes: discharging polyglycolic acid melted at a melting temperature T ℃ from a spinneret by an extruder; and a step of obtaining a polyglycolic acid fiber obtained by collecting a fibrous melt of polyglycolic acid discharged from the spinneret into a gas phase at a spinning speed Vm/min, wherein the method for producing polyglycolic acid fiber satisfies the following conditions (i) to (iii): (i) t is more than or equal to 250 and less than or equal to 300, (ii) V is more than or equal to 3000, and (iii) V/T is more than or equal to 11.5.
Advantageous effects
According to one aspect of the present invention, polyglycolic acid fiber having low heat shrinkability and easy hydrolyzability can be realized.
Drawings
Fig. 1 is a view schematically showing an example of the structure of a high-speed melt spinning apparatus capable of producing polyglycolic acid fibers according to one embodiment of the present invention.
Fig. 2 is a view schematically showing an example of the structure of a direct spinning and drawing apparatus for producing polyglycolic acid fibers of a comparative example.
Detailed Description
[ polyglycolic acid fiber ]
[ constitution ]
The polyglycolic acid fiber according to one embodiment of the present invention has the following characteristics.
(A) The crystallinity is 20% or more.
(B) Birefringence 35X 10-3The above.
(C) The amorphous orientation coefficient is 0.30 or less.
In the present embodiment, the "polyglycolic acid fiber" means a fiber containing polyglycolic acid as a main component in a composition constituting the fiber. "polyglycolic acid as a main component" means that polyglycolic acid is the largest component in the resin component. The content of polyglycolic acid in the composition may be 80% by mass or more, may be 90% by mass or more, and may be 100% by mass.
Polyglycolic acid may be a homopolymer or a copolymer. Other monomers that may be sources of other structural units in the copolymer may be any monomers that can polymerize with glycolic acid, and examples thereof include lactic acid, caprolactone, and trimethylene carbonate. The kind and amount of the other monomer may be appropriately determined within a range in which the effects of the present embodiment can be obtained.
The polyglycolic acid fiber may have other configurations within a range in which the effects of the present embodiment are obtained. One or more of such other structures may be used. Examples of other structures include a coating layer for coating the surface of the polyglycolic acid fiber.
The polyglycolic acid fiber may further contain other components within a range in which the effects of the present embodiment are obtained. Such other component may be one or more, and examples thereof include additives and other thermoplastic resins. Examples of the additives include a heat stabilizer, a blocking agent, a plasticizer, a heat ray absorber, and a filler. Examples of the other thermoplastic resins include poly-L-lactic acid, poly-DL-lactic acid, poly (L-lactic acid-co-epsilon-caprolactone), polyhydroxybutyrate, polybutylene succinate, poly (R-3-hydroxybutyrate-co-R-3-hydroxyhexanoate), polycaprolactone, and polyvinyl alcohol. The polyglycolic acid fibers may contain a thermoplastic resin in addition to polyglycolic acid, but are preferably substantially composed of a homopolymer of polyglycolic acid.
[ Properties ]
(degree of crystallinity)
The polyglycolic acid fiber in the present embodiment has a crystallinity of 20% or more. When the crystallinity of the polyglycolic acid fiber is 20% or more, the heat shrinkage of the polyglycolic acid fiber tends to be sufficiently low. When the crystallinity of the polyglycolic acid fiber is too low, the thermal shrinkage of the polyglycolic acid fiber may be high. When the crystallinity of the polyglycolic acid fiber is too high, the hydrolysis rate may be lowered.
From the viewpoint of reducing the heat shrinkage of the polyglycolic acid fiber, the crystallinity of the polyglycolic acid fiber is preferably 25% or more, and more preferably 30% or more. In addition, from the viewpoint of increasing the hydrolysis rate of polyglycolic acid fibers, the crystallinity of polyglycolic acid fibers is preferably 50% or less, more preferably 45% or less, and still more preferably 40% or less.
The crystallinity of polyglycolic acid fiber can be determined by a density gradient tube method. The crystallinity can be adjusted by V/T in the production method described later, and the crystallinity tends to be increased by increasing V/T.
[ double refraction ]
The polyglycolic acid fiber in the present embodiment has a birefringence of 35X 10-3The above. From the viewpoint of sufficiently reducing the heat shrinkage rate by highly orienting polyglycolic acid and forming a stable fiber structure, the polyglycolic acid fiber preferably has a birefringence of 35 × 10-3The above. When the birefringence of the polyglycolic acid fiber is too low, the polyglycolic acid fiber becomes an oriented amorphous fiber and the heat shrinkage rate becomes high. When the birefringence of the polyglycolic acid fiber is too high, the molecular orientation may be too high, and the hydrolysis rate of the polyglycolic acid fiber may decrease.
The birefringence of polyglycolic acid fiber is preferably 40 × 10 from the viewpoint of sufficiently reducing the heat shrinkage rate of polyglycolic acid fiber-3Above, more preferably 50 × 10-3The above. From the viewpoint of improving the hydrolyzability of the polyglycolic acid fiber, the birefringence of the polyglycolic acid fiber is preferably 80 × 10-3Hereinafter, more preferably 70 × 10-3Hereinafter, more preferably 60 × 10-3The following.
The birefringence of polyglycolic acid fibers can be measured using a polarizing microscope. The birefringence can be adjusted by V/T in the production method described later.
[ amorphous orientation factor ]
The polyglycolic acid fiber in the present embodiment has an amorphous orientation coefficient of 0.30 or less. When the amorphous orientation coefficient of polyglycolic acid fibers is 0.30 or less, the hydrolysis rate can be sufficiently increased. When the amorphous orientation coefficient of polyglycolic acid fibers is too large, the hydrolysis rate may be decreased.
From the viewpoint of improving hydrolyzability, the amorphous orientation coefficient of polyglycolic acid fibers is preferably 0.25 or less, and more preferably 0.20 or less. The polyglycolic acid fiber may have a low amorphous orientation coefficient, and for example, it may be 0.05 or more from the viewpoint of exhibiting sufficient hydrolyzability.
The amorphous orientation coefficient of polyglycolic acid fiber can be calculated by assuming a two-phase model of crystal and amorphous, and using the crystal orientation coefficient, birefringence and crystallinity described later. The amorphous orientation coefficient can be adjusted by V/T in the manufacturing method described later.
[ Heat shrinkage ratio ]
The polyglycolic acid fiber of the present embodiment has sufficiently low heat shrinkability. The heat shrinkage rate of the polyglycolic acid fiber of the present embodiment can be appropriately determined depending on the use of the polyglycolic acid fiber. From the viewpoint of the thermal dimensional stability generally required as a fiber material, the thermal shrinkage rate of the polyglycolic acid fiber at 100 ℃ is preferably 5% or less, and more preferably 2.5% or less. When the heat shrinkage ratio of the polyglycolic acid fiber exceeds 5%, the polyglycolic acid fiber may not be suitable for use as an industrial fiber, and may adversely affect the processing of the base fabric.
The heat shrinkage ratio of polyglycolic acid fiber at 100 ℃ can be calculated from the fiber length before and after the specific heat treatment in an environment of 100 ℃. The heat shrinkage can be adjusted by the V/T of the production method described later, and the heat shrinkage tends to be small by increasing the V/T.
[ hydrolyzability ]
The polyglycolic acid fiber of the present embodiment has sufficiently high hydrolyzability. The hydrolyzability of the polyglycolic acid fiber of the present embodiment can be appropriately determined depending on the use of the polyglycolic acid fiber. The hydrolyzability may be appropriately specified depending on the use. For example, in the case of the use as an in vivo material, the hydrolyzability of polyglycolic acid fibers can be determined from the molecular weight retention of polyglycolic acid fibers after immersion in a phosphoric acid buffer solution at 37 ℃ for 2 weeks. It can be said that the lower the molecular weight retention, the higher the hydrolyzability. The above-mentioned retention ratio of the molecular weight in the polyglycolic acid fiber of the present embodiment is preferably 50% or less, more preferably 40% or less, and still more preferably 30% or less, from the viewpoint of suppressing the generation of inflammation when used as an in vivo material.
The molecular weight retention can be determined by the ratio of the weight average molecular weight of the polyglycolic acid fiber before and after immersion in the above-mentioned phosphoric acid buffer solution, and the weight average molecular weight can be measured by a known method such as gel permeation chromatography. The molecular weight retention can be adjusted by V/T in the production method described later.
[ melting Point ]
The polyglycolic acid fiber of the present embodiment may have two or more melting peaks detected by Differential Scanning Calorimetry (DSC) at a temperature of 220 ℃. The two or more melting peaks are preferably a melting point specific to polyglycolic acid constituting the fiber and a temperature higher than the melting point. Polyglycolic acid fibers having two or more melting peaks tend to have lower heat shrinkability. Therefore, from the viewpoint of reducing the heat shrinkage rate, the polyglycolic acid fiber preferably has two or more melting peaks described above. The more developed crystal structure is formed, for example, the higher the crystallinity is, the more the number of the melting peaks tends to become 2 or more.
[ fiber diameter ]
The fiber diameter of the polyglycolic acid fiber in the present embodiment can be appropriately determined in accordance with the range in which the effects of the present embodiment are obtained from the viewpoint of productivity of the polyglycolic acid fiber and realization of a normal appearance. When the fiber diameter of the polyglycolic acid fiber is too small, the productivity may be lowered, and when the fiber diameter of the polyglycolic acid fiber is too large, the appearance of the polyglycolic acid fiber may be adversely affected by, for example, a crimp. From the viewpoint of suppressing the decrease in productivity, the fiber diameter of the polyglycolic acid fiber is preferably 5 μm or more, more preferably 10 μm or more, and still more preferably 12 μm or more. In addition, the fiber diameter of the polyglycolic acid fiber is preferably 40 μm or less, and more preferably 37 μm or less, from the viewpoint of suppressing adverse effects on the appearance of the polyglycolic acid fiber.
[ Crystal orientation factor ]
From the viewpoint of achieving low heat shrinkability, the polyglycolic acid fiber of the present embodiment preferably has a high crystal orientation coefficient. From the viewpoint of reducing the heat shrinkability, the crystal orientation coefficient of polyglycolic acid is preferably 0.85 or more, more preferably 0.90 or more, and still more preferably 0.92 or more.
The crystal orientation coefficient of polyglycolic acid fiber can be determined by a calculation method of Wilchinsky using a diffraction intensity curve obtained from an X-ray diffraction image obtained by using an X-ray diffraction apparatus. The crystal orientation coefficient can be adjusted by V/T in the production method described later.
[ use ]
The polyglycolic acid fiber of the present embodiment can be preferably used for applications requiring low heat shrinkability and high hydrolyzability. The polyglycolic acid fiber of the present embodiment can be used for biomedical materials such as sutures, artificial blood vessels, and cell culture substrates; cloth products such as non-woven fabrics and clothes; or various industrial materials.
In addition, the polyglycolic acid fiber of the present embodiment is expected to have excellent dyeability because of its low heat shrinkability. Therefore, in applications to living bodies, a visually recognizable color is easily colored, and thus improvement of convenience in the applications is expected. Further, since polyglycolic acid fibers of the present embodiment are hydrolyzable, it is expected that fabrics having a characteristic texture and the like are created as new fabrics and materials for the same by weaving the fibers into fabrics and hydrolyzing the fibers.
[ effect ] of action
The polyglycolic acid fiber of the present embodiment has a crystallinity of 20% or more. The high crystallinity means that the amount of polyglycolic acid crystals in the fiber is large. In addition, the polyglycolic acid fiber of the present embodiment has a birefringence as high as 35 × 10-3The above. This high birefringence means that the polyglycolic acid in the fiber has a high molecular orientation. The polyglycolic acid fiber of the present embodiment has an amorphous orientation coefficient as low as 0.30 or less. The amorphous orientation coefficient indicates the orientation of the amorphous phase, and a low amorphous orientation coefficient means that the orientation of the amorphous phase of polyglycolic acid in the fiber is low (disordered).
The polyglycolic acid fiber of the present embodiment has a high crystallinity and a low amorphous orientation coefficient. That is, the polyglycolic acid fibers of the present embodiment have high molecular orientation due to high microscopic birefringence, and mainly have a structure with developed crystal phases.
In general, an increase in strain due to the spinning speed is manifested as an increase in thermal shrinkage as a thermal relaxation phenomenon, but a developed crystal structure and a stable structure of an amorphous phase having a low orientation can be formed by further increasing the spinning speed. The heat shrinkage tends to be low when the crystallinity is high and further the amorphous orientation coefficient is low. Thus, the polyglycolic acid fiber of the present embodiment has low heat shrinkability.
The polyglycolic acid fiber of the present embodiment has a low amorphous orientation coefficient. Hydrolysis of polyglycolic acid starts by diffusion of water into amorphous portions. Regarding roots, et al ((1) Sekine, s., Akieda, h., Ando, i., Asakura, T.A Study of the Relationship between the sensitive string and Dynamics of As-span and drain polymer (glycoolic acid) fibers.j.40, 10-16 (2008.) (2) Sekine, s., Yamauchi, k., Aoki, a., Asakura, t.heteologenes structure of Poly (glycoolic acid) fiber with differential scanning meter, X-ray differential hydrolysis, solid-NMR and molecular Dynamics amorphous 6083.90. 6090. the existence of high degree of inhibition of hydrolysis is shown. That is, assuming that the diffusion rate of water into the amorphous portion is affected by the orientation of the amorphous portion, the polyglycolic acid fiber of the present embodiment having a low amorphous orientation coefficient has a structure in which water easily enters in a microscopic scale. Thus, the polyglycolic acid fiber of the present embodiment has high hydrolyzability.
The polyglycolic acid fiber of the present embodiment may have two or more melting peaks in DSC. This is considered to be because, when a developed crystal phase is formed in polyglycolic acid fibers, the crystal phase is less likely to melt than other portions, and exhibits a sufficient difference in melting point. Thus, such polyglycolic acid fibers having two or more melting peaks tend to have lower heat shrinkability.
The polyglycolic acid fiber of the present embodiment may have a fiber diameter of 5 to 40 μm. Within this range of fiber diameter, the polyglycolic acid fiber of the present embodiment can be produced to have both the characteristics of good morphology of the fiber and the above-mentioned good microstructure. Therefore, the polyglycolic acid fiber having the fiber diameter has good productivity, and can suppress the occurrence of appearance defects such as curling marks.
The polyglycolic acid fiber of the present embodiment can be produced by the following production method.
[ Process for producing polyglycolic acid fiber ]
A method for producing polyglycolic acid fibers according to an embodiment of the present invention includes: a first step of discharging polyglycolic acid melted at a melting temperature T ℃ from a spinneret by an extruder; and a second step of obtaining a polyglycolic acid fiber obtained by collecting a fibrous melt of polyglycolic acid discharged from a spinneret into a gas phase at a spinning speed Vm/min, wherein the method for producing the polyglycolic acid fiber satisfies the following conditions (i) to (iii).
(i)250≤T≤300；
(ii)V≥3000；
(iii)V/T≥11.5。
The first step and the second step in the production method of the present embodiment may be performed by a known method, also referred to as a high-speed melt spinning method, within a range that satisfies the above-described conditions.
[ first step ]
The melting temperature (T ℃) in the first step is 250 ℃ to 300 ℃. When the melting temperature is 250 to 300 ℃, a good melt of polyglycolic acid can be discharged from the spinneret. If the melting temperature is too low, the polyglycolic acid may not melt sufficiently. Therefore, it may be difficult to discharge a molten polyglycolic acid from the spinneret, and the load on the extruder may be increased to stop the screw of the extruder. When the melting temperature is too high, polyglycolic acid is thermally decomposed, and the molecular weight of polyglycolic acid may be reduced by the thermal decomposition.
The melting temperature in the first step is preferably 255 ℃ or higher, more preferably 260 ℃ or higher, from the viewpoint of sufficiently melting polyglycolic acid. From the viewpoint of suppressing the thermal decomposition of polyglycolic acid, the melting temperature is preferably 295 ℃ or lower, and more preferably 290 ℃ or lower.
In the first step, a molten polyglycolic acid is discharged from a spinneret connected to an extruder.
In the present embodiment, a spinneret of a type known in the art can be used according to the application of the polyglycolic acid fiber to be obtained. The shape of the discharge hole provided in the spinneret may be determined as appropriate. Examples of the shape of the discharge hole provided in the spinneret include a circle, a quadrangle, a triangle, a star, and the like. The diameter of the discharge hole provided in the spinneret may be appropriately determined. The number of the discharge holes provided in the spinneret may be appropriately determined depending on the production conditions, and may be one or more.
The first step can be performed by a known extrusion molding machine. From the viewpoint of stably discharging the polyglycolic acid melt from the spinneret, it is preferable to feed the polyglycolic acid melt toward the spinneret using a quantitative fluid supply device such as a gear pump.
In the first step, the amount of polyglycolic acid discharged from the spinneret as a melt is appropriately determined depending on the fiber diameter of the polyglycolic acid fiber to be produced and the spinning speed described below. In the present embodiment, the discharge amount of the discharge hole per one spinneret can be appropriately determined within a range of, for example, 0.1 to 13.7 g/min.
[ second Process ]
In the second step, the spinning speed (Vm/min) is a speed at which the melt discharged from the spinneret into the gas phase is cooled and solidified, and recovered as fibrous polyglycolic acid. The fiber may be recovered by reeling onto a winder. The spinning speed is represented by the length per unit time of the spun yarn at the time of collection, and when the spun yarn is collected by winding the spun yarn into a winder, the spinning speed is represented by the length per unit time of the fiber wound onto the winder.
The spinning speed in the second step is 3000 m/min or more. When the spinning speed is 3000 m/min or more, the polyglycolic acid melt discharged from the spinneret can be molded into an appropriate fiber shape, and the molecular structure of polyglycolic acid in the polyglycolic acid fiber can be set to a desired state. In this way, the recovery of the melt in the second step forms the appearance of the fiber and also builds the microscopic internal structure of the fiber. The desired state in the molecular structure means a state in which the molecular chain of polyglycolic acid is oriented in the direction of elongation and crystallized. In the present embodiment, the construction of such a desired internal structure is also referred to as "orientation crystallization".
If the spinning speed is too low, the orientation of the molecular chains of the polyglycolic acid fiber may become insufficient and crystallization may not be achieved, and if the spinning speed is too high, yarn breakage may occur. The spinning speed is preferably 4000 m/min or more from the viewpoint of achieving oriented crystallization. From the viewpoint of suppressing the occurrence of yarn breakage, the spinning speed is preferably 10000 m/min or less, more preferably 9000 m/min or less, and still more preferably 8000 m/min or less.
In the second step, the molten polyglycolic acid discharged from the spinneret is formed into a fiber shape, elongated, and cooled while being recovered. The position from the discharge hole of the spinneret to the collection position is also referred to as a spinning line, and the length of the spinning line may be appropriately determined within a range that can construct a desired microscopic internal structure.
In the production method of the present embodiment, the ratio (V/T (m/(min. degree. c))) of the spinning speed (V) to the melting temperature (T) is 11.5 or more. If the ratio is too small, the oriented crystallization described above becomes insufficient, and the polyglycolic acid in the collected polyglycolic acid fibers may have a low crystallinity or a low birefringence. From the viewpoint of producing a polyglycolic acid fiber having sufficient orientation crystallization, the above ratio is preferably 12.0 m/(min. DEG C) or more, and may be 40.0 m/(min. DEG C) or less.
[ other Processes ]
The manufacturing method of the present embodiment may further include other steps than the first step and the second step described above within a range in which the effects of the present embodiment are obtained.
For example, the production method of the present embodiment may further include a step of charging a material containing polyglycolic acid into an extruder before the first step. The form of the material may be any form known in extrusion molding of resins, and examples thereof include granules, powders, granules, sheets, blocks and the like. The material may be fed into the extruder at one time, may be fed in a plurality of times, may be fed from a plurality of places of the extruder together, or may be fed in sequence.
The production method of the present embodiment may further include a step of cooling the molten polyglycolic acid in a fiber form on the spinning line in the second step. In the second step, the molten material of the fibrous polyglycolic acid is cooled by air while moving in a gas phase. The cooling step may be a step of supplying cold air to the fibrous melt or a step of supplying warm air. The cooling step may be a step of appropriately adjusting the length from the discharge holes of the spinneret to the position where the polyglycolic acid fibers are collected, or a step of appropriately adjusting the cooling time in accordance with the spinning speed.
The production method of the present embodiment may further include, in the second step, a step of adjusting the temperature of the melt discharged from the spinneret. Such a temperature adjustment step can be performed by a heating tube disposed immediately below the spinneret and surrounding the discharge port. The temperature adjusting step may be a step of maintaining the temperature of the space inside the heating cylinder at 80 to 320 ℃.
The production method of the present embodiment does not include a drawing step of the polyglycolic acid fiber recovered in the second step. The drawing step is a step of drawing a polyglycolic acid fiber formed into a fiber shape to change the internal structure such as the molecular structure and the crystal structure of the polyglycolic acid fiber, thereby constructing an internal structure showing the physical properties of the fiber. In the present embodiment, since the polyglycolic acid fiber formed into a fiber shape and having an internal structure which exhibits desired physical properties of the fiber can be produced by the first step and the second step, the above-mentioned drawing step is not necessary. This is because the above-described drawing step is performed on a polyglycolic acid fiber having an internal structure that already exhibits desired physical properties, and the internal structure of the polyglycolic acid fiber may be changed to an internal structure that does not exhibit the desired physical properties.
[ manufacturing apparatus ]
The production method of the present embodiment can be carried out by a high-speed melt spinning method as described above, and can be carried out using a known apparatus capable of carrying out the method. Fig. 1 is a view schematically showing an example of the structure of a high-speed melt spinning apparatus capable of producing polyglycolic acid fibers according to one embodiment of the present invention.
As shown in fig. 1, the high-speed melt spinning apparatus 1 includes: an extruder 11 having a barrel containing a screw; a hopper 12 for feeding a fiber material into the barrel; a gear pump 13 for feeding the melt in the barrel; a conduit 14 serving as a flow path for the melt fed out by the gear pump 13; a spinneret 15 for discharging the melt passing through the conduit 14 to the outside; and a winder 16 for winding the fibrous polyglycolic acid melt F discharged from the spinneret 15 at a high speed. The extruder 11 is a device capable of producing a molten polyglycolic acid at the above-mentioned melting temperature, and the winder 16 is a device capable of winding the molten material F while stretching it at the above-mentioned spinning speed. The distance from the spinneret 15 to the winder 16 can be adjusted as appropriate, and for example, can be adjusted within a range of 1 to 5 m.
[ effect ] of action
In the production method of the present embodiment, a molten polyglycolic acid which has been melted at a specific melting temperature T ° is discharged from a spinneret, and the discharged fibrous molten polyglycolic acid is stretched in a gas phase at a specific spinning speed and collected by a winder. The melting temperature and the spinning speed are set so that the ratio of the spinning speed to the melting temperature is a specific ratio.
In the production method of the present embodiment, a melt of polyglycolic acid having a sufficiently high temperature is discharged from a spinneret, and the discharged melt is recovered after being stretched and recovered by winding or the like. The melt becomes polyglycolic acid fibers having an internal structure exhibiting desired physical properties until the recovery. In this manner, in the production method of the present embodiment, the polyglycolic acid fiber is molded from the melt of polyglycolic acid, and a desired internal structure is built inside the fiber. The fibrous melt is subjected to orientation crystallization by elongation due to recovery. The ratio of the spinning speed to the melting temperature can also be said to be a parameter for achieving moderate oriented crystallization. According to the production method of the present embodiment, polyglycolic acid fiber having a low thermal shrinkage rate (at 100 ℃) and high hydrolyzability can be produced. For example, the production method of the present embodiment can produce the polyglycolic acid fiber of the present embodiment having the above-described characteristics (a) to (C).
The production method of the present embodiment has found that polyglycolic acid fibers having a characteristic internal structure as described above can be obtained by using polyglycolic acid in a high-speed melt spinning method, and has been carried out as described above.
In the production method of the present embodiment, in order to achieve oriented crystallization, it is considered effective to draw a molten material of polyglycolic acid in a fibrous form at a high speed in a state of being cooled to some extent.
By controlling the process of stretching the melt in the spinning line, it becomes easy to build an internal structure in the polyglycolic acid fiber, which exhibits desired physical properties. That is, by adjusting the spinning speed or the melting temperature in the spinning line, a large elongation stress is applied to the melt in the spinning line, whereby the oriented crystallization can be realized. The increase in the elongation stress is caused by an increase in the tension based on the inertial force or the air resistance and an increase in the force against the deformation generated by the magnitude of the elongation strain speed. The distribution of the elongation of the melt in the spinning line can be appropriately set by adjusting the above-mentioned characteristics (i) to (iii), or by the above-mentioned cooling step, or by the above-mentioned heating cylinder. The "distribution of elongation of the melt in the spinning line" refers to the transition of the elongation stress of the fibrous material at each point from the discharge port to the winding.
For example, when the melting temperature of the fibrous polyglycolic acid is low, the molten material may be recovered at a high speed to generate a sufficiently strong stress in the fibrous polyglycolic acid, which is preferable from the viewpoint of sufficiently proceeding the oriented crystallization. When the melting temperature is high, the solidification point (position) shifts to the winding side, but by further increasing the spinning speed, sufficient stress can be generated in the fibrous polyglycolic acid.
The position and strength of the stress on the spinning line caused by the recovered fibrous polyglycolic acid can be determined or estimated based on experimentally measured values or on calculated values in computer simulations. The production of polyglycolic acid fibers in which such stress is generated in fibrous polyglycolic acid can be appropriately realized by the configuration of the production apparatus and the operating conditions thereof.
Therefore, in the step of recovering the fibrous polyglycolic acid, optimization in accordance with the state of production of the polyglycolic acid fiber can be expected by adjusting the elongation distribution on the spinning line so that a desired elongation stress is generated in a desired position on the spinning line in the fibrous polyglycolic acid.
The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the description. Embodiments obtained by appropriately combining technical means disclosed in the different embodiments are also included in the technical scope of the present invention.
[ conclusion ]
As is apparent from the above description, the polyglycolic acid fiber according to the embodiment of the present invention has the following features: (A) the crystallinity is more than 20 percent; (B) birefringence 35X 10-3The above; and (C) an amorphous orientation coefficient of 0.30 or less. The method for producing polyglycolic acid fibers according to the present embodiment includes: discharging polyglycolic acid melted at a melting temperature T ℃ from a spinneret by an extruder; and a step for obtaining a polyglycolic acid fiber obtained by recovering a fibrous polyglycolic acid melt discharged from a spinneret into a gas phase at a spinning speed Vm/min, wherein the method for producing a polyglycolic acid fiber satisfies the following conditions: (i) t is more than or equal to 250 and less than or equal to 300; (ii) v is more than or equal to 3000; and (iii) V/T.gtoreq.11.5. Thus, according to the embodiment of the present invention, a polyglycolic acid fiber having low heat shrinkability and easy hydrolyzability can be provided.
In addition to the easy hydrolyzability, the polyglycolic acid fiber according to the embodiment of the present invention has a molecular weight retention of 50% or less after immersion in a phosphoric acid buffer solution at 37 ℃ for 2 weeks, from the viewpoint of suppressing inflammation when used in a living body.
Further, from the viewpoint of reducing the heat shrinkability, it is still more effective that the polyglycolic acid fiber of the embodiment of the present invention has two or more melting peaks at 220 ℃ or higher as detected by differential scanning calorimetry.
In addition, from the viewpoint of improving the productivity of polyglycolic acid fibers and suppressing the occurrence of defects in appearance, polyglycolic acid fibers according to an embodiment of the present invention are more effective in which the fiber diameter is 5 μm or more and 40 μm or less.
In the method for producing polyglycolic acid fibers according to the embodiment of the present invention, the produced polyglycolic acid fibers may have the above-described characteristics (a) to (C). This production method is suitable for producing polyglycolic acid fibers according to the present embodiment.
Examples
[ example 1]
< Condition >
Materials: polyglycolic acid (melting point 220 ℃, melt viscosity 960 Pa.s (temperature 270 ℃, shear rate 122 seconds)-1))。
Melting temperature (T): 270 ℃.
Spinning nozzles: single hole (nozzle aperture 1.0 mm).
Discharge amount (per hole): 5.0 g/min.
Spinning speed (V): 4000 m/min.
[ example 2]
Polyglycolic acid fiber 2 was obtained in the same manner as in example 1 except that the spinning speed was changed to 5000 m/min.
[ example 3]
Polyglycolic acid fiber 3 was obtained in the same manner as in example 1 except that the spinning speed was changed to 6000 m/min.
[ example 4]
Polyglycolic acid fiber 4 was obtained in the same manner as in example 1 except that the spinning speed was changed to 7000 m/min.
[ example 5 ]
Polyglycolic acid fiber 5 was obtained in the same manner as in example 1 except that the melting temperature of polyglycolic acid was changed to 255 ℃ and the spinning speed was changed to 3000 m/min.
[ example 6 ]
Polyglycolic acid fiber 6 was obtained in the same manner as in example 5 except that the spinning speed was changed to 4000 m/min.
[ example 7 ]
Polyglycolic acid fiber 7 was obtained in the same manner as in example 5 except that the spinning speed was changed to 5000 m/min.
[ comparative example 1]
Polyglycolic acid fiber C1 was obtained in the same manner as in example 1 except that the spinning speed was changed to 1000 m/min.
[ comparative example 2]
Polyglycolic acid fiber C2 was obtained in the same manner as in example 1 except that the spinning speed was changed to 3000 m/min.
[ comparative example 3]
Polyglycolic acid fiber C3 was obtained in the same manner as in example 5, except that the spinning speed was changed to 2000 m/min.
[ comparative example 4]
Polyglycolic acid fibers were produced using a direct spinning and drawing apparatus 2 as shown in fig. 2. Fig. 2 is a view schematically showing an example of the structure of a direct spinning and drawing apparatus for producing polyglycolic acid fibers of a comparative example.
As shown in fig. 2, the direct spinning and drawing apparatus 2 includes a spinneret 17 instead of the spinneret 15, the spinneret 17 includes a plurality of discharge ports, the first godet roller 19 instead of the winder 16 is provided, and the first godet roller 19 receives the fiber F1 generated by spinning and sends the fiber F1 to a drawing apparatus at a later stage. The direct spinning and drawing apparatus 2 further includes a drawing apparatus, and a heating cylinder 18 is further provided immediately below the spinneret 17. Except for this, the direct spinning stretching apparatus 2 has the same configuration as the high-speed melt spinning apparatus 1 described above.
The drawing device includes a second godet 21, a third godet 22, and a fourth godet 23 for drawing the fiber F1, and a winder (also referred to as "winder") 24 for winding up the drawn fiber F2.
Polyglycolic acid fiber C4 was produced under the following conditions using a direct spinning and drawing apparatus shown in fig. 2. In order to maintain the tension of the fiber F2, the rotation speed of the second godet roller 21 was set to be about 1% higher than the rotation speed of the first godet roller 19.
< Condition >
Materials: polyglycolic acid (melting point 220 ℃, melt viscosity 960 Pa.s (temperature 270 ℃, shear rate 122 seconds)-1))。
Melting temperature: 255 ℃.
Spinning nozzles: 24 holes (nozzle aperture 0.25 mm).
Discharge amount (per hole): 0.292 g/min.
Heating a cylinder: length 20cm, temperature 120 ℃.
Spinning speed: 4000 m/min.
Spinning temperature (temperature of the first godet 19): at 25 ℃.
Stretching ratio: 5.0 times (between the second godet roller 21 and the third godet roller 22).
Drawing temperature (temperature of second godet roller 21): and 65 ℃.
Relaxation/heat treatment temperature (temperature of third godet roller 22 and fourth godet roller 23): at 90 ℃.
[ comparative example 5 ]
Polyglycolic acid fiber C5 was obtained in the same manner as in comparative example 4, except that the draw ratio was changed to 4.0 times.
[ comparative example 6 ]
Polyglycolic acid fiber C6 was obtained in the same manner as in comparative example 4, except that the draw ratio was changed to 3.0 times.
[ evaluation ]
[ fiber diameter ]
The diameters of polyglycolic acid fibers 1 to 7 and C1 to C6 were measured by a polarizing microscope ("BX 53-P", manufactured by Olympus corporation). The average of the diameters of five samples of polyglycolic acid fibers measured was defined as the fiber diameter of the fiber.
[ degree of crystallinity ]
Using a density gradient tube prepared from 1, 2-dichloroethane and carbon tetrachloride, the density ρ of each of polyglycolic acid fibers 1 to 7 and C1 to C6 was measured after immersing the sample in the density gradient tube at 25 ℃ for 24 hours. Degree of crystallinity XcFrom the measured density p (g/cm)3) Calculated by using the following formula (1). In the formula (1), ρcAnd ρaRespectively show the crystal density and amorphous density of polyglycolic acid, and in this example, they are each represented by ρc＝1.69g/cm3，ρa＝1.50g/cm3。
[ numerical formula 1]
[ double refraction ]
Birefringence of each of polyglycolic acid fibers 1 to 7 and C1 to C6 was measured using a polarizing microscope ("BX 53-P", manufactured by olympus corporation) equipped with a berek compensator. The average value of birefringence obtained by measuring five samples of polyglycolic acid fibers was defined as the birefringence of the fiber.
[ Crystal orientation factor ]
Since the C-axis orientation could not be directly evaluated without obtaining diffraction of the (00l) plane, the crystal orientation coefficients f of polyglycolic acid fibers 1 to 7 and C4 to C6cThe calculation was performed according to the following Wilchinsky calculation method, based on the following formula (2). In the formula (2), the reaction mixture is,
the orientation coefficient of the c-axis is calculated from the following equation (3). In the formula (3), the reaction mixture is,
and
the mean square of the cosines of the orientation angles calculated from the diffraction intensity curves of the (110) plane and the (020) plane are respectively expressed, and calculated from the following equation (4). In the above formula (3), θ1And theta2Denotes the angle formed by the (110) plane and the (020) plane with respect to the b-axis, and θ is represented in this example according to the crystal structure of polyglycolic acid1、θ2Are respectively set to theta1＝49.9°，θ2＝0°。
[ numerical formula 2]
In the above-mentioned formula (4),
represents the diffraction intensity curve. The diffraction intensity curves were obtained by obtaining wide-angle X-ray diffraction (WAND) images of polyglycolic acid fibers 1 to 7 and C4 to C6 using an X-ray diffraction apparatus ("NANO-Viewer", manufactured by NIHOM CORPORATION). At this time, the sample was vertically irradiated with CuK α rays (wavelength: 0.154nm) generated at 40kV and 20mA for 30 minutes and treated with a nickel filter, and a wide-angle X-ray diffraction image was obtained using an imaging plate.
The diffraction intensity curve was corrected for air scattering. (110) The planes contain amorphous halos and (101) planes and are therefore separated by a Gaussian function fit of the following equation (5). Since the diffraction angle of the (020) plane is also close to that of the (102) plane, the separation is performed by the same method. In the formula (5), N is the peak intensity of diffraction intensity,
the peak intensity position, w is the half width (half-width).
[ numerical formula 3]
In the polyglycolic acid fibers C1 to C3, no diffraction image was obtained, and the crystal orientation coefficient f could not be calculatedc。
[ amorphous orientation factor ]
When a two-phase model of crystal and amorphous is assumed, the birefringence Δ n is represented by the following formula (6). In the following formula (6), it is assumed that the contribution of the form birefringence to the total birefringence is small and is ignored. Here, XcIs the degree of crystallinity, fcIs a crystal orientation coefficient, faIs an amorphous orientation coefficient, ΔncAnd Δ naCrystalline and amorphous intrinsic birefringence of polyglycolic acid, respectively.
[ numerical formula 4]
Δn＝ΔncXcfc+Δna(1-Cc)fa (6)
In the above formula (6), Δ ncAnd Δ naValues calculated using atomic bond polarizabilities of Bunn et al were set as Δ nc＝0.137，Δna＝0.117。
In the polyglycolic acid fibers C1 to C3, the crystal orientation coefficient f could not be calculatedcTherefore, the amorphous orientation coefficient f cannot be calculateda。
[ melting Point ]
The melting peaks of polyglycolic acid fibers 1 to 7 and C1 to C6 were measured using a Differential Scanning Calorimetry (DSC) apparatus ("DSC-60A plus", manufactured by Shimadzu corporation). About 10mg of the sample was weighed and sealed in an aluminum crucible. The temperature was raised from 0 ℃ to 280 ℃ at a temperature raising rate of 10 ℃ per minute under a nitrogen atmosphere (flow rate of 10 mL/minute). The melting point of the fiber was determined as the melting peak.
[ Heat shrinkage ratio ]
The thermal shrinkage of polyglycolic acid fibers 1 to 7 and C1 to C6 were measured. The sample (100 m) was rewound to a rewinder having an outer frame of a circumference of 1m, one end of the resultant skein was fixed, and a weight of 20g was applied to the other end to measure the skein length L. Then, the weight was removed, and the mixture was suspended in a dry oven at 100 ℃ for 30 minutes and then cooled to room temperature. Then, one end of the skein was fixed again, a weight of 20g was applied to the other end, the skein length LHT was measured, and the heat shrinkage (%) was calculated from the following formula (7). Here, L represents the skein length (m) before heat treatment, and LHT represents the skein length (m) after heat treatment. In the application of the fiber material, it is judged that there is no problem in practice as long as the heat shrinkage rate is 5% or less.
(formula (II))
Heat shrinkage (%) (L-LHT)/L.times.100 (7)
[ molecular weight holding ratio ]
The hydrolysis characteristics of polyglycolic acid fibers 1 to 7 and C1 to C6 were evaluated. The weight average molecular weight of each polyglycolic acid fiber was measured. Next, each polyglycolic acid fiber was immersed in a phosphate buffer solution, allowed to stand in an oven set at 37 ℃ for 2 weeks, taken out, and the weight average molecular weight of each polyglycolic acid fiber was measured by Gel Permeation Chromatography (GPC). The percentage of the weight average molecular weight of the polyglycolic acid fiber before the impregnation and standing was determined as a molecular weight retention ratio, and the hydrolysis characteristics were evaluated from the molecular weight retention ratio. In applications where the hydrolyzability is utilized, it is judged that there is no problem in practice as long as the molecular weight retention is 50% or less.
The weight average molecular weight of each polyglycolic acid fiber was measured as follows. 10mg of polyglycolic acid fiber was weighed out and dissolved in 0.5mL of dimethyl sulfoxide at 150 ℃. The solution was cooled to room temperature, dissolved in 10mL of hexafluoro-2-propanol containing 5mM sodium trifluoroacetate, and filtered using a 0.2 μm membrane filter. This solution was poured into a GPC apparatus ("Shodex-104", manufactured by Showa Denko K.K.) to determine the weight average molecular weight of the polyglycolic acid fiber as a value converted to polymethyl methacrylate.
The production conditions and the above evaluation results for each of polyglycolic acid fibers 1 to 7 and C1 to C6 are shown in table 1.
[ Table 1]
TABLE 1 production conditions and Properties
[ Observation ]
As is apparent from table 1, polyglycolic acid fibers 1 to 7 all had sufficiently low heat shrinkability and sufficiently good hydrolysis-facilitating properties. This is considered to be because the melt of the fibrous polyglycolic acid is wound and elongated at a sufficiently high speed during spinning, and an appropriate stress is generated in the melt, thereby inducing orientation and crystallization of the polyglycolic acid in the fiber together with formation of the fiber.
In polyglycolic acid fibers 1 to 7, the crystallinity is high, the crystal phase shows high orientation, and the amorphous phase has low orientation. Since the degree of crystallinity is sufficiently high and the amorphous orientation coefficient is sufficiently low, it is considered that polyglycolic acid fibers 1 to 7 have low heat shrinkability.
Further, since the orientation of the amorphous phase in the polyglycolic acid fibers is low, it is considered that water easily permeates into the fibers and diffuses in the polyglycolic acid fibers 1 to 7 to easily hydrolyze, and sufficiently high easy hydrolysis is exhibited.
The polyglycolic acid fibers 2 to 4 and 7 have two melting points of about 220 to 250 ℃ and about 230 to 245 ℃, and have a high crystallinity. The former of polyglycolic acid fibers 2 to 4 and 7 is considered to be the melting point of polyglycolic acid, and the latter is considered to be the melting point derived from a component less fusible than polyglycolic acid, i.e., the melting point derived from developed crystals of polyglycolic acid. It is considered that, in the polyglycolic acid fibers 2 to 4 and 7, crystallization proceeds further in the above-mentioned oriented crystallization, and thus lower heat shrinkability is exhibited. From the above, it is considered that the low heat shrinkability contributes to both the low orientation in the amorphous phase and the developed crystal structure of polyglycolic acid, although it cannot be concluded at a glance.
On the other hand, polyglycolic acid fibers C1 to C3 have easy water-wet characteristics, but have high heat shrinkability and are insufficient from the viewpoint of low heat shrinkability. The polyglycolic acid fibers C1 and C3 both had a low spinning speed and a small V/T. Polyglycolic acid fiber C2 has a small V/T. In addition, in these fibers, the crystallinity is significantly low, and a diffraction image by X-ray irradiation is not obtained, so that the crystal orientation coefficient cannot be obtained. Therefore, polyglycolic acid fibers C1 to C3 are considered to be amorphous fibers.
In addition, polyglycolic acid fibers C4 to C6 have higher heat shrinkability and lower hydrolysis rate than polyglycolic acid fibers 1 to 7. The polyglycolic acid fibers C4 to C6 have a significantly low spinning speed and a significantly low V/T, and further include a drawing step in the production process. Therefore, it is considered that the crystal structure is developed by the oriented crystallization by stretching, and the orientation in the amorphous phase is also increased, and as a result, the heat shrinkage is increased, and the water diffusion rate is suppressed, and the hydrolyzability is insufficient.
Industrial applicability of the invention
The present invention can be used for a fiber or cloth material requiring low heat shrinkability and high hydrolyzability, such as a medical material represented by a bioabsorbable suture, and a product containing the fiber or cloth material.
Description of the reference numerals
1: a high speed melt spinning device;
2: a direct spinning stretching device;
11: an extruder;
12: a hopper;
13: a gear pump;
14: a conduit;
15. 17: a spinneret;
16. 25: a coiler;
18: a heating cylinder;
19: a first godet roller;
21: a second godet roller;
22: a third godet roller;
23: a fourth godet roller;
24: a coiler (winder).
Claims (6)
1. A polyglycolic acid fiber having the following properties:
(A) the crystallinity is more than 20 percent;
(B) birefringence 35X 10-3The above; and
(C) the amorphous orientation coefficient is 0.30 or less.
2. The polyglycolic acid fiber according to claim 1,
the polyglycolic acid fiber has a molecular weight retention of 50% or less after being immersed in a phosphoric acid buffer solution at 37 ℃ for 2 weeks.
3. The polyglycolic acid fiber according to claim 1 or 2,
the polyglycolic acid fiber has two or more melting peaks at 220 ℃ or higher as detected by differential scanning calorimetry.
4. A polyglycolic acid fiber according to any one of claims 1 to 3,
the fiber diameter is 5 to 40 μm.
5. A method for producing polyglycolic acid fiber, comprising:
discharging polyglycolic acid melted at a melting temperature T ℃ from a spinneret by an extruder; and
a step for obtaining a polyglycolic acid fiber in which a fibrous melt of polyglycolic acid discharged from the spinneret into a gas phase is collected at a spinning speed Vm/min,
the method for producing a polyglycolic acid fiber satisfies the following conditions (i) to (iii):
(i)250≤T≤300；
(ii)V≥3000；
(iii)V/T≥11.5。
6. the method for producing polyglycolic acid fiber according to claim 5, wherein,
the polyglycolic acid fiber has the following characteristics:
(A) the crystallinity is more than 20 percent;
(B) birefringence 35X 10-3The above; and
(C) the amorphous orientation coefficient is 0.30 or less.
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