JPS60190947A - Fiber structure - Google Patents

Abstract

An integral fibrous structure has a plurality of continuous polymeric filaments, individual filaments extending from one side of the structure to the opposite side of the structure. The portions of the filaments on one side of the structure are of a first polymeric composition and the portions of the filaments on the opposite side of the structure are of a second polymeric composition different from the first polymeric composition. The structure is built up by a continuous fibre forming process where fibres are attracted to a surface (11) by electrostatic potential, the compounds of the fibres being varied during production.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to fibrous structures, such as fibrous mats or articular tubular structures. More particularly, but not exclusively, the present invention relates to fiber composite vascular grafts.
tlar grafts).

There is already a method using electrostatic attraction, in which a solution of a polymer such as polyurethane is ejected from a thin nozzle toward the surface of the object, and an electrostatic potential is created between the surface and the nozzle. proposed the production of a camphor fiber structure, analogous to a mat. Polymer fibers form between the nozzle and the surface and are attracted to the surface. This method produces tubular fibrous constructs that can be used as synthetic vascular grafts by using a surface in the form of a rotating mandrel to accumulate fibrous tubes around the mandrel. It is applied for.

Electrospinning methods are described in some detail in U.S. Pat.
Anis et al.'s paper in 1978 (Tταna.

Am, Soc, Intern, Organs
), a proposal is made to use electrospinning methods for the production of synthetic vascular grafts. The microstructure of the fiber material produced during electrospinning is also described in the article by Anis et al. More recently, for example, our UK patent no.
No. 217,487, we describe adapting the properties of synthetic vascular grafts to in-vivo conditions, and our British Patent No. 8,216,066.
Developments are being made in controlling aotropic properties.

In the present invention, an integral fiber structure of a plurality of continuous polymeric filaments is provided, where the individual filaments gztend from one side of the structure to the other side of the structure. The portion of the filament on one side of the structure is comprised of a first polymer composition and the portion of the filament on the other side of the structure is comprised of a second polymer composition different from the first polymer composition. Consisting of a polymeric composition.

The term "anisotropic polymer composition" means that the polymer itself varies across the structure, but - for example, certain additives are present in the composition on one side of the structure. This includes changes in the composition of the filaments such that the filaments are present on the opposite side of the structure, but are not present on the opposite side of the structure.

The structure may include a transition zone between opposite sides of the structure, and the portion of the filament in the transition zone may have a polymer composition consisting of a mixture of the first and second polymer compositions. can.

The M@body composition of the filament may vary continuously between both sides of the structure, and the composition of the portion of the filament in the transition zone adjacent to one side of the structure may have a large proportion of the primary of a polymer composition, and the adjacent portion of the filament on the opposite side of the structure can contain a greater proportion of a second polymer composition.

Alternatively, the composition of the filaments can be abruptly changed to provide distinct 1-wions with different polymer compositions within the structure. More than two layers may be present in the structure.

The structure may be in the form of a mat or may be a tubular member (tubl arms rnb tir) or, if the structure is a tubular member, filaments on the inner surface of the tubular member. The portion of the filament is preferably comprised of the first polymeric composition so as to provide compatibility with the material that the inner surface comes into contact with, and the portion of the filament on the outer surface of the tubular member is preferably Preferably, the second polymeric composition is comprised to provide desirable strength properties and other physical properties.

The tubular member is separated from the tube wall by one or more segment elements.
ntal eltptnent&). If the internal diameter of the tubular member is large enough, e.g.
) can be used as

The invention further provides a method for forming an integrated polar fiber structure according to the invention, which method comprises directing filaments of the first polymer composition to a particular surface. initiating accumulation of fibrous structures of the composition;
and it consists in changing the composition of the filament during its manufacture in such a way that the part of the filament remote from the surface of the structure consists of the second polymer composition.

The composition of the filaments may vary abruptly or gradually across the structure.

For purposes of illustration, one embodiment of a fibrous structure according to the invention and its manufacturing method will be described below with reference to the drawings.

FIG. 1 conceptually depicts an apparatus for electrostatically spinning synthetic vascular grafts. The polymer solution is passed through a capillary needle lO at several thousand revolutions per minute, e.g. 5000 r, p,
m, and is discharged toward a mandrel rotating with an electrostatic charge. Generally, the mandrel 11 is -
It is at a potential of 12kV.

When the polymer bath leaves the needle IO, polymer filaments are formed which are then attracted to the rotating electrostatically charged mandrel 11 to form a fibrous structure around the mandrel.

Once the fiber structure has been built, the structure is removed from the mandrel to obtain a fiber tube.

The characteristic properties of the valve-like fibrous structure formed on the mandrel are determined by changes in the speed of rotation of the mandrel, the type of polymer used, and the potential of the auxiliary poles. can do.

Capillary button 10 is supplied with polymer solution from manifold 13, which is supplied by tubes 14 and 15 that meet at T-connector 16. Both tubes 14 and 15 include flexible flexible tubes 17 and 18, respectively. Tube 1 so that each tube can be closed
4 has pulp 19 and '#15 has valve 20.

Control lines 21 and 22 control the opening and closing of valves 19 and 20.

With tube 14 supplied by a first air-plunger driven syringe 23 and tube 15 supplied by a second air-plunger driven syringe 24, the device is configured to It becomes possible to inject the coalescing solution from the needle 10 towards the mandrel 11. closed pulp 2
Manifold 13 by drain line containing 6&c
It is possible to drain the liquid.

The arrangement of FIG. 1 allows the production of an integral, uninterrupted fibrous structure of continuous polymer filaments around the surface of the mandrel 11, while the portion of the filaments on the inner bottom surface of the fibrous structure is on the outside. The polymer composition is different from that of the filament on the surface. Is this id thunder shaped? This is particularly useful when using the hepatocytes, for example, as a synthetic vascular graft. It is known that different polymers have different blood compatibility and that different polymers have different strength properties. In a particular example, −
Yuzu polyurethane has good blood compatibility, but has poor elasticity and exhibits a high degree of crease. The second polyurethane having a high Young's modulus has sufficient strength and axial property f: but poor blood 11ξ adhesion property.

The following example describes the production of a sweet acid vascular graft having a thin inner lining of a first polyurethane over a ridge of a second polyurethane, as described in the following example (apparatus of Figure 1). Furthermore, the graft is composed of continuously spun fibers such that the individual fibers vary in composition between their ends, providing an integrated, uninterrupted five-fiber structure. There is.

Embodiment The sequence of operation of the apparatus of FIG. 1 in this embodiment is as follows.

1. Fill the syringe 24 with the first polymer dope and fill the syringe 23VC with the second polymer dope.

2 Using valves 19, 20 and 26, inject the second polymer dope into tube 14 and then the first polymer dope into tube 15 and manifold 13.

3. Close pulps 19 and 26, syringe 24, tube 15
Then, static spinning using the first polymer dope contained in the manifold 13 is started.

4. After a predetermined time, open valve 19 and close valve 20. After extruding the remaining first polymer dope from the needle 10, spinning continues without interruption using the second polymer dope.

5. The abruptness of the transition from the first polymeric dawg to the second polymeric dawg is such that the manifold 1 of the second polymeric dawg
3 and the volumes of manifold 13, needle lO and T-joint 16.

This transition can be controlled by the use of pulp 26 on drain line 25, which can be used to drain the remaining first polymer doug at different rates. The concentration gradient of the bipolymer in the graft wall follows a constant adjustable relationship, as shown in FIG. 2, where the solid line shows the abrupt change when valve 26 is used. ,
The dashed line indicates gradual change.

A further development of the first example was based on a porosity test, which showed that the permeability of the 2iWl graft was too high. Situations have been observed where blood or plasma flow through the wall leads to excessive platelet entrapment on the inner wall surface, impairing the antithrombotic properties of the graft. The solution is to include an outer layer of a third polymer, such as one with a high Young's modulus, which when deposited on the second polymer produces a small interstitium (1nter-
stitial) gives a dense matrix with volume. In this case, the overall graft wall permeability is determined by this outer layer. FIG. 3 shows a section of the bilayer graft in cross section. A further advance is to add a third polymeric outer layer to the implant shown in FIG.

Many different polymers can be added in the electrospinning process. In U.S. Pat. No. 4,044,404, several examples are given, such as polyurethane, polyamide and polyacrylonitrile, all of which can be spun from solution, and polytetrafluoro Ethylene and polyester can be spun from dispersions. Water-soluble polymers such as polyvinyl alcohol, polyvinylpyrrolidone and polyethylene oxide can be spun from aqueous solutions.

The restrictions on the fiber structure and manufacturing method according to the present invention are as follows:
The two or more polymers used to change the composition of the filament during the spinning process must be dispersible or otherwise soluble in the same solvent system. . Thus, although it is possible to spin with different polyurethanes or with different polyesters in the dispersion, as used in the preferred embodiment,
For example, polyurethane cannot be changed to polyester.

Even if the polymer composition itself varies along the length of the filament, the properties of a particular polymer composition can be changed by the presence of additives. for example,
A silicone lubricant can be added to a polyurethane polymer and spun as the inner surface of the implant, with the outer surface of the implant being a tetra-polyurethane with a silicone lubricant. Such examples are also included within the scope of this invention.

An advantage of the above-described implant embodiments is that different layers can be arranged in different layers, either in their morphology (e.g. porosity, pore shape, fiber thickness) or in their chemistry (e.g. polymer type, presence of drugs). This means that it can be optimized for specific properties. For example, stimulants such as heparin or prostacyclin can be included in the inner layer to improve properties with respect to contact with blood. When such layers are formed discontinuously, lines of weakness exist between adjacent surfaces and delamination can occur at very low mechanical stresses. The advantage of the above method is that it allows the integrally formed subsequent wall components to be formed into a fibrous structure in which the different layers are integrally formed so that they fit together in a well-controlled manner. That's true.

An example of a bilayer graft according to the above embodiment was found to have a 300% improvement in patency compared to a non-laminated, single component graft in a canine common carotid artery study. That's true. Other possibilities, such as as pledgets and drug-releasing vascular grafts, are also possible, as very thick b0 The embodiments described above relate to tubular fibrous structures for use as vascular grafts. However, it is also clear that the present invention is equally applicable to planar fibrous structures, such as mats, and that such other structures have wide application. Probably.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of an apparatus for manufacturing a tubular fiber structure. FIG. 2 shows the concentration of the monopolymer composition in the walls of the structure. FIG. 3 is a partial cross-sectional view of a tubular fibrous structure produced by the apparatus of FIG. Patent applicant: 1 person other than Nichicon Incorporated

Claims (1)

[Claims] 1. A plurality of continuous polymers) in a one-lamin integrated fibrous structure in which the individual filaments extend from one side of the structure to the opposite side of the structure 1 qm; The portion of the filament on one side of the filament is comprised of the first polymer composition.
and wherein the portion of the filaments on the opposite side of the structure is comprised of a second polymer composition different from the first polymer composition. 2. Claim 1 comprising a transition zone between the apexes 11 of the structure, wherein the portion of the filament in the transition zone has a polymer composition consisting of a mixture of the first and second polymer compositions. The fiber structure described in Section 1. λ The composition of the portion of the filament in the transition zone adjacent to one side of the structure contains a large proportion of the first polymer composition and the portion of the filament in the transition zone adjacent to the opposite side of the structure 3. A fibrous structure according to claim 2, characterized in that the second polymer composition comprises a large proportion of the second polymer composition. 4. A fibrous structure according to any one of claims 1 to 3, wherein the polymer composition of the structure varies gradually between opposite sides of the structure. 5. A fibrous structure according to claim 1, wherein the composition of the filaments varies rapidly to provide distinct layers with different polymeric compositions within the structure. 6. The fiber structure according to any one of claims 1 to 5, characterized by various changes in the polymer composition of the fibers. 7. The fibrous structure according to claims 1 to 6, which is in the form of a mat. 8. Claims 1 to 7 in the form of a tubular member
The fibrous structure according to any of the above. 9. The portion of the filament on the inner surface of the g-shaped member is comprised of a first polymeric composition such as to provide compatibility with the material with which the inner surface comes into contact, and the portion of the filament on the outer surface of the tubular member is 10. The fibrous structure of claim 9, wherein the filament portions are comprised of a second polymeric composition that provides desirable strength properties and other physical properties of the tubular member. 10. A fibrous structure consisting of a tubular member as claimed in claim 8 or 9, cut to provide one or more partial elements from the tubular wall. 11. Initiate the accumulation of fibrous structures of the first polymer composition by directing the filaments of the first polymer composition to a specific surface, and during the production process, direct the composition of the filaments to the surface of the structure. (iij
A method for forming an integrated fibrous structure as described in any of the above. 12. The method according to claim 11, wherein the composition of the 1'L filament is abruptly changed. 12. The method of claim 11, wherein %Wr is gradually varied across the structure. 14. A method for forming an integral fibrous structure substantially as described herein with reference to and shown in the drawings. 15. A fibrous structure produced by the method as described in any one of items 11 to 14. 16. A fibrous structure substantially as herein described with reference to and shown in the drawings.