JPH0526499B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surgical suture made of a polyvinylidene fluoride resin porous thread and a method for manufacturing the same, and more specifically, the present invention relates to a surgical suture thread made of a polyvinylidene fluoride resin porous thread, and more particularly, to a surgical suture thread made of a polyvinylidene fluoride resin porous thread, The present invention relates to a surgical suture having excellent mechanical strength, having fiber bundles oriented in the same direction and having an asymmetric pore size structure, and a method for manufacturing the same.

Surgical suture threads have traditionally been woven from natural fibers such as silk, nylon, and polyester-based synthetic resins, but in recent years, suture threads with improved biocompatibility and strength have been used. Drawn yarns made of polypropylene and tetrafluoroethylene resin have been developed. In the case of drawn polypropylene yarn, although its strength has been improved, its biocompatibility is not sufficient and it also lacks flexibility. On the other hand, drawn threads of tetrafluoroethylene resin have improved strength, are highly flexible, and have excellent biocompatibility as resin properties.

However, since the processability of tetrafluoroethylene resin is extremely poor, it is necessary to go through a complicated manufacturing process, which tends to result in non-uniformity of properties and is inevitably disadvantageous in terms of cost.

From this point of view, the present inventors used polyvinylidene fluoride resin, which has biocompatibility and strength equivalent to that of tetrafluoroethylene resin, and has excellent processability. By obtaining a surgical suture system having oriented fiber bundles and an asymmetric pore size structure, in which the average pore diameter of the compact layer of the asymmetric pore structure is 0.5μ or less and the average thickness of the compact layer is 10μ or less. , we have found that we can take a step forward toward this goal.

In addition to biocompatibility and strength, properties required for surgical sutures include flexibility, surface smoothness, and strength to prevent the surface from becoming fluffy. Sutures fill these requirements well.

One of the features of the invention is that the surgical suture has fiber bundles oriented along its length. The fiber bundle provides the yarn with longitudinal tensile strength and at the same time gives the yarn flexibility against bending.

Another feature of the present invention is that the yarn has an asymmetric pore size structure, the average pore size of the dense layer of the asymmetric pore size structure is 0.5μ or less, and the average thickness of the dense layer is
It must be 10μ or less.

Here, the asymmetric pore size structure in the present invention is
This refers to a pore size structure in which the pores near the surface of the porous yarn are small and the pores inside the yarn are large. A pore structure in which the pore diameter is small in the vicinity and increases toward the inside of the thread.

(2) A structure with a sponge-like pore shape, with pores near the surface and large pores inside.

(3) Composite structures of (1) and (2) are mentioned, but are not limited to this.

The asymmetric pore size structure provides the yarn with flexibility, surface smoothness, and strength to prevent the surface from becoming fluffy, and at the same time serves to impart strength to the yarn as a whole.

In other words, the dense layer with a pore size of 0.5μ or less provides surface smoothness and strength to prevent the surface from fuzzing, and at the same time, the dense layer and the small-diameter structure in the vicinity of the dense layer, together with the aforementioned fiber bundle, The large pores inside the yarn are responsible for the flexibility of the entire yarn.

In this way, the surgical suture of the present invention can satisfy the opposing properties of flexibility and tensile strength.

The shape of the fibers of the present invention is not particularly limited, and may be hollow fibers in addition to filled fibers.

Further, the cross-sectional shape is not particularly limited, and may be circular, elliptical, or star-shaped.

Next, the manufacturing method will be explained.

Although much research has been conducted on polyvinylidene fluoride resin porous membranes and porous hollow fibers, it has been difficult to obtain porous fibers with properties suitable for the purpose of the present invention using conventional methods. Have difficulty.

The following is a typical method for manufacturing a thermoplastic resin porous membrane.

(1) Melt extrusion method, (2) Extraction method, (3) Elution method, (4) Sintering method
(5) Neutron irradiation method, (6) semi-wet method, (7) wet method Melt extrusion method is Japanese Patent Publication No. 59-5327, Japanese Patent Publication No. 59-59-
41310 and JP-A No. 54-62273, a method is to melt-extrude a resin, mold it, and then stretch it to make it porous. However, it is difficult to obtain sufficient porosity and the flexibility is poor. I can't get it.

The extraction method and elution method are described in JP-A-51-75675 and JP-A-Sho.
49-98880, this method involves adding inorganic or organic fillers to a resin, press-molding it, or stretching it in combination with a melt-extrusion method, followed by solvent extraction or elution, but it is difficult to control the pore size. It is not easy, the process is complicated, and extraction takes a long time. With this method, it is difficult to obtain an asymmetric pore size structure.

The sintering method is a method in which fine particles of resin are sintered to form pores by enlarging the gaps between the particles either as they are or by stretching, and is disclosed in US Pat. In addition, a method is also used in which the filler mixed in the resin is eluted after sintering in combination with the elution method.
Although disclosed in JP-A-51-134761, all of them have large pore diameters, and when the film is made thinner or smaller in diameter, the mechanical strength decreases significantly, making it difficult to put them to practical use. This type of method is often applied and effective for insoluble ethylene tetrafluoride resins, but is less compatible with polyvinylidene fluoride resins.

As a semi-wet method, Japanese Patent Application Publication No. 51-136579,
59-12691 and JP-A-59-6231, etc., however, it is difficult to control the gel state when the solution is cooled to gel or the solvent is removed by evaporation to obtain a gelled product, and it is difficult to control the gel state. It is difficult to obtain molded products with strength.

Among these membrane-forming methods, the wet method is considered to be the most suitable for manufacturing porous membranes.

For example, JP-A-56-56202, JP-A-55-99934,
As seen in JP-A-55-69627, resin, solvent,
By a method in which a solution consisting of a surfactant is brought into contact with a coagulant, an asymmetric pore membrane having a skin layer, a support layer, and microvoids can be obtained.
However, the strength is still insufficient.
In addition, as seen in JP-A-58-91731 and JP-A-59-16503, it is possible to change the coagulant or to add impurity to the solution.
By adding a non-solvent or the like, phase separation can be controlled and a membrane without an asymmetric pore size structure can be obtained, but this also cannot be said to have sufficient strength.

On the other hand, in Japanese Patent Publication No. 52-38591, strength was improved by stretching a porous membrane obtained by a wet method from a solution consisting of a resin, a slow-drying solvent, and a quick-drying solvent. When using a method in which a dry solvent is the main component and most of it is volatilized and then immersed in a non-solvent, the porosity and asymmetric pore size structure required for the purpose of the present invention cannot be obtained.

In addition, in the manufacturing method disclosed in Japanese Patent Application Laid-Open No. 58-91808,
The development of fiber bundles required for this purpose cannot be expected, and as a result, high strength cannot be obtained.

As a result of intensive studies from this viewpoint, the present inventors extruded a solution containing a polyvinylidene fluoride resin, a solvent, and, if necessary, a swelling agent, under heating above room temperature, and added a coagulant to the coagulant. After contacting to remove the solvent and drying, the resin is stretched by 200% or more at a temperature below the melting point of the resin, so that the yarn has fiber bundles oriented in the length direction and has an asymmetric pore size structure. Therefore, a surgical suture can be obtained in which the average pore diameter of the compact layer with the asymmetric pore size structure is 0.5μ or less and the average thickness of the compact layer is 10μ or less, and it has excellent biocompatibility, strength, flexibility, and surface smoothness. It has been found that both of them have a satisfactory strength and do not have a fluffy surface.

Polyvinylidene fluoride resins used in the present invention include vinylidene fluoride homopolymers, copolymers of vinylidene fluoride with tetrachloroethylene, hexafluoropropylene, propylene, ethylene, or methyl methacrylate, and resins miscible with vinylidene fluoride, such as A mixture with acrylic resin is selected.

In addition, as a solvent, dimethylformamide,
diethylformamide, dimethylacetamide,
Selected as one or a mixed solvent of two or more of amides such as diethylacetamide, urea such as tetramethylurea and tetraethylurea, and nitrogen-containing solvents such as N-methyl 2-pyrrolidone, N-formylpiperidine, and 1-formylmorpholine. However, N-methyl 2-pyrrolidone is particularly preferably selected.

The swelling agent may be a poor solvent or a non-solvent for the polyvinylidene fluoride resin, as long as it is water-soluble, and is added within a range that does not impair the uniformity of the solution and the formation of a dense layer.

In order to achieve high strength, which is one of the objectives of the present invention, it is necessary to use unstretched porous yarn obtained by a wet method.
It must be highly fibrous by stretching more than 200%.

For this purpose, the resin concentration of the solution is preferably 200% by weight or more, preferably 30% by weight or more.

Further, in order to uniformly spin the highly concentrated solution into a desired diameter, the solution is heated to above room temperature and extruded. The heating temperature of the solution depends on the ease of spinning, the spinning diameter,
The draft ratio, pore shape, and porosity are selected to be controlled according to the purpose, but in order to perform uniform spinning, it is necessary to keep the temperature below the boiling point of the solvent.

The yarn thus spun is introduced into a coagulant, which is selected from water, methanol, ethanol, and mixtures of one or more of these. Although a solvent for polyvinylidene fluoride resin may be added, it is preferable to use water as the main component in order to obtain an asymmetric pore size structure and not to interfere with the formation of a dense layer.

When forming hollow fibers, a coagulant is discharged from the hollow fiber nozzle at the same time as the solution, or a gas is discharged instead of the coagulant.

The solidified porous thread is washed with water to complete the solvent removal, then dried at a temperature below the heat deformation temperature of the resin, and stretched at a temperature below the melting point of the resin.

When the melting point of the resin is Tm, the stretching temperature is preferably Tm - 50°C or more and Tm or less, more preferably Tm - 20°C or more and Tm or less.

The stretching ratio is preferably 200% or more, more preferably 400% or more. This stretching ratio is more stably achieved within the above stretching temperature range. This drawing operation causes the matrix layer of the porous yarn to become highly fibrous, resulting in a porous yarn with significantly improved strength compared to undrawn yarn.

The heating medium for heating during stretching is not particularly limited, but may be appropriately selected from hot liquid medium, hot air, metal rolls, and the like. From the viewpoint of temperature control, a solid heat medium such as a metal roll is preferably used.

In the following, the present invention will be further explained by examples.

Example 1 A polyvinylidene fluoride-ethylene tetrafluoride copolymer (Kynar 5201 manufactured by Pennwalt) was dissolved in N-methyl 2-pyrrolidone to prepare a 35% by weight solution.
This solution was extruded through a die with a diameter of 3 mm under heating at 70°C, allowed to fall through the air under tension of 5 cm, immersed in distilled water to solidify, and then continuously desolvented in water. After winding it up,
The bobbin was immersed in water at 80°C, the water was circulated to complete the solvent removal, and then dried in hot air at 80°C to obtain a porous yarn with a nearly circular cross-sectional shape of 0.7 mm in diameter. .

When the cross-sectional structure was observed using a scanning electron microscope,
As shown in Figures 2-a and 2-b, it exhibited an asymmetric pore size structure with a dense layer.

This porous yarn was stretched at 142°C with a stretching ratio of 500%, and had a diameter of 0.35 mm, a porosity of 34%, a tensile strength per optical cross-sectional area of 11.9 Kg/mm ² at room temperature, and a Young's modulus.
A surgical suture of 38.8 Kg/mm ² was obtained.

When the cross-sectional structure was observed using a scanning electron microscope,
As shown in Figures 1-a and 1-b, it exhibited an asymmetric pore size structure with a dense layer, and had fiber bundles oriented in the length direction of the yarn.

Example 2 A surgical suture was obtained in exactly the same manner as in Example 1 except that the stretching ratio was 800%. When the physical properties were measured, the diameter was 0.29 mm, the porosity was 28%, the tensile strength per optical cross-sectional area at room temperature was 18.1 Kg/mm ² , and the Young's modulus was 96.4 Kg/mm ² .

Comparative Example 1 Diameter 0.7 mm obtained in exactly the same manner as Example 1
When the physical properties of the porous yarn having a substantially circular cross-sectional shape were measured without being stretched, it was found to have a porosity of 45% and a tensile strength per optical cross-sectional area of 1.2 Kg/mm ² at room temperature.

〔Effect of the invention〕

Made of polyvinylidene fluoride resin with excellent biocompatibility, mechanical properties, and processability, it has fiber bundles oriented in the length direction of the thread, has an asymmetric pore size structure, and has a dense layer with an asymmetric pore size structure. Average pore size is 0.5μ
In the following, by obtaining a porous thread with a thickness of the dense layer of 10μ or less, it is possible to perform high-performance surgery with excellent biocompatibility, high strength, flexibility, surface smoothness, and strength without fuzzing. It has become possible to provide sutures for use at low cost.

[Brief explanation of drawings]

Figures 1-a and 1-b are scanning electron micrographs of a cross section of a surgical suture made of polyvinylidene fluoride resin. Figure-2-a and Figure-2-
b is a scanning electron micrograph of a cross section of an undrawn porous yarn obtained by wet spinning polyvinylidene fluoride resin.

Claims (1)

[Scope of Claims] 1. A surgical suture made of a polyvinylidene fluoride resin porous thread has fiber bundles oriented in the length direction of the thread, and has an asymmetric pore size structure, and has an asymmetric pore size structure. A surgical suture characterized in that the average pore diameter of the lamina densa is 0.5μ or less and the average thickness of the lamina densa is 10μ or less. 2. Claim 1, wherein the yarn has a porosity of 5% or more and a tensile strength per optical cross-sectional area at room temperature of more than 5 kg/mm ²
Surgical sutures as described in section. 3. Claim 1, wherein the yarn has a porosity of 30% or more and a tensile strength per optical cross-sectional area at room temperature of more than 10 Kg/mm ²
Surgical sutures as described in section. 4 A solution containing a polyvinylidene fluoride resin, a solvent, and if necessary a swelling agent is extruded and brought into contact with a coagulant under heating above room temperature to remove the solvent and dry, and then heated to a temperature below the melting point of the resin. at 200%
A method for producing a surgical suture, characterized by stretching the suture thread. 5 When the melting point of the resin is Tm, the stretching temperature is
5. The method for producing a surgical suture thread according to claim 4, wherein the temperature is Tm -50°C or higher and Tm or lower. 6. The method for producing a surgical suture according to claim 4, wherein the stretching temperature is Tm - 20°C or higher and Tm or lower. 7. The method for producing a surgical suture according to claim 4, wherein the stretching ratio is 400% or more. 8. The method for producing a surgical suture according to claim 4, wherein the resin concentration of the solution is in a range exceeding 30% by weight. 9. The method for producing a surgical suture according to claim 4, wherein the solvent is N-methyl-2-pyrrolidone.