Fibrillar product

(54) Name: Product for use as a vascular prosthesis and method of preparation

7508781-7 i

The present invention relates to a product for use as a vascular prosthesis, comprising a tubular component, also to a method of producing such a product, the manufacture of which is based on electrostatic spinning of organic materials.

The technique of electrostatic spinning of liquids in the form of solutions containing a fiber-forming material is known and has been described in a number of patents and also in the general literature.

Electrostatic spinning involves introducing a liquid into an electric field, thereby causing the liquid to produce fibers which tend to be drawn into an electrode. Simultaneously with the drawing from the liquid, the fibers are usually cured, which can be done by a simple cooling (eg when the liquid is normally solid at room temperature), by chemical curing (eg by treatment with a curing steam) or by evaporation of solvent (eg by removing water). The fiber product can be collected on a suitably placed device and later removed therefrom.

Fibers produced by electrostatic spinning are thin and have a diameter of 0.1-25 microns, preferably 0.5-10 microns and most preferably 1.0-5 microns.

It has been found that the fibers, if collected, form a fibrous web of suitable thickness, due to the natural porosity of this web, provide a fibrous web with a variety of uses, which

7508781-7 is determined by the composition of the fibers, their density at the precipitation, their diameter and natural half-strength as well as the thickness and design of the fiber rope. The fiber rope can also be finished with other materials to modify the properties, e.g. to increase the strength or water resistance.

Fibers with different properties can be produced by varying the composition, either by spinning a liquid containing several components which individually can give the final product a desired property, or by simultaneously spinning different fiber liquids of different composition, whereby the fibers are collected and formed simultaneously to a fibrous tuber consisting of an intimate mixture of different fibrous materials. Another alternative is to produce a fiber rope which is built up of a plurality of layers of different fibers (or fibers of the same material but with different properties, eg different diameters) and thereby vary the time during which the different fibers are applied to the collecting device. One way to achieve this alternative is e.g. to allow a moving I collection device in turn to pass a set of spin- | nozzles from which the fibers are spun electrostatically, whereby the fibers in are applied in the order in which the collecting device reaches a suitable position in relation to the different spinning nozzles.

According to the present invention, a product of the kind initially described is characterized in that the tubular component contains fibers, produced by electrostatic spinning of a fiber-forming organic material.

The method according to the invention is mainly characterized by electrostatic spinning of a fluid for forming fibers which is collected on a suitably designed, charged forming means to form a substantially tubular fiber product and removal of the product from the forming means.

The fibers are preferably present in the form of a fiber rope.

According to the present invention there is thus obtained a fibrous rope consisting of a plurality of fibers of organic material, which fibers are produced by electrostatic spinning of a liquid containing the material or a starting compound therefor.

The term fibertova here refers to electrostatically spun fibers in the form of three-dimensional as well as two-dimensional products.

According to an embodiment of the present invention, a fibrous tuber formed of electrostatically spun fibers is produced in a form suitable for using seam wound dressings. A special advantage of materials

7508781-7 made of electrostatically spun fibers is that the fibers can have a very small diameter and thus give a fiber rope with small spaces between the fibers and consequently with a large surface content. When the wound dressing is made of a wettable polymer, blood and serum leaving the wound can penetrate the dressing, and the large surface content thereby promotes coagulation. The dressings can be used in emergencies to stop bleeding. Examples of suitable wettable polymers are polyurethanes. A special advantage when the wound dressing is made of a non-wettable polymer is that if the gaps between the fibers are small enough, on average about 1-100 p, then tissue fluids, including blood, have no tendency to penetrate into the dressing but are retained next to the wound there. coagulation occurs. Such a dressing can be easily removed because no blood penetrates and coagulates in the dressing material. The dressings further have the advantage that they are usually porous enough to allow the exchange of oxygen and water vapor between the atmosphere and the wound surface. Examples of non-wettable polymers are saturated polyesters, e.g. polyethylene terephthalate, fluorinated compounds and especially fluorinated hydrocarbons, e.g. PTFE, as well as silicones.

The dressings can of course be combined with suitable supporting or reinforcing materials, with e.g. fiber cushions of woven fibers having other desired properties, or they may be subjected to surface treatment or other treatment with materials having antiseptic or wound healing properties. Coagulation can be facilitated, for example, by the presence of substances that accelerate or induce coagulation in or on the nonwoven fabric and / or on materials with which the wound dressing is combined. Other components that can be included in the fiber rope are waterproof layers that protect against the unwanted effect of moisture, dirt, etc.

The wound dressing according to the invention preferably consists of a fibrous web of flexible, non-absorbent, porous hydrophobic material in combination with a non-absorbent backing layer. The backing layer is preferably, but not necessarily, made of hydrophobic material. The dressing can also include materials that make it possible to apply pressure to the fiber rope. Such a material can e.g. consists of a stretchable elastic bandage.

In a preferred embodiment, the dressing consists of a support layer, one surface of which has an adhesive coating, and on the same surface of the support layer also a porous fiber rope according to the invention. A small pad of absorbent or non-absorbent material may, if desired, be placed between the backing layer and the nonwoven fabric.

The effect of non-adhesive dressings according to the invention is examined.j

7508781-7 | in

- ⁴. in thesis by applying the dressing over the wound of a rabbit, which was a surface with total skin loss, and the healing process was observed. were compared with control ulcers. A dressing made of the preferred material allowed normal healing with little or no fluid flow through the dressing and minimal adhesion of the dressing to the wound crust.

According to another embodiment of the invention, a shaped fiber rope is obtained, which consists of electrostatically spun fibers, in the form of a cladding or surface coating on a component which can come into contact with body fluids, such as blood and lymph. The fiber rope may be tubular or have an irregular shape.

The difficulty of obtaining with blood and body fluids satisfactorily compatible surfaces on e.g. walls of artificial hearts and other circulatory systems as well as such compatible coatings on damaged as well as artificial blood vessels constitute an obstacle to the development of reliable artificial organs and tissues. It has been found that if a coating of fine fibers of suitable material is applied to the surfaces of the artificial organs and tissues, the compatibility with blood and other tissue fluids can be increased. In this case, however, it is desirable that the coating is very thin and the use of an electrostatically precipitated fiber coating has been found to solve many of the critical problems. The primary desires are: a) very small fiber diameter (small in relation to the cell dimensions) and a fiber diameter of 0.1-10 microns, most preferably 0.5-5 microns is particularly suitable;

b) the coating should be so porous that it allows cells to penetrate into it, and the ideal pore dimension is therefore 5-25 microns, preferably 7-15 microns;

c) the coating should preferably have a thickness of 10-50 microns;

d) the coating must be able to be attached to the object on which it is to form a cladding in any way that does not adversely affect the above-mentioned properties;

(e) the coating shall not contain any substances which are harmful to the body or to the cells and liquids with which it comes into contact.

The electrostatic spinning technique enables a method to produce coatings that perfectly match the dimensions and contours of the articles to be applied to a coating, since the surface of the article, or positive or negative copies thereof, can be used as a collection device in the electrostatic spinning process.

Materials from which the coatings can be conveniently prepared are polymeric substances and especially inert polymeric substances. Preferred substances are fluorinated hydrocarbons, e.g. PTFE, which can be easily spun from a dispersion of the material in a suitable dispersant, and polyurethanes which can be spun from a solution.

7508781-7

In some cases, the fiber pad can be so strong or spun so thick that it can be used without any supporting material, ie it can not rightly be called a coating. Such self-supporting products in the form of tubes can be electrostatically spun, and for example, vascular parts can be made of polytetrafluoroethylene or polyurethanes, etc.

The electrostatically spun products, e.g. tubes or other shapes, as mentioned above may have sufficient strength to be used as such without reinforcement. However, a material which is reinforced by e.g. a reinforcing layer has been applied to one side of the product, which layer can also be electrostatically spun, or by reinforcing material being included in the product wall itself. Thus, electrostatically spun products can be reinforced by incorporating into their walls a woven or non-woven fabric or some alternative fiber arrangement. In particular, it is preferred to use as a reinforcement a spiral of suitable fibers, which spiral, which consists of electrostatically spun fibrous material, is applied inside the walls of the tubular product. Although the reinforcement is usually enclosed in the wall material, the possibility cannot be ruled out that the reinforcement is applied to the surface of the product, if its presence there is not to the detriment. The thickness of the reinforcement depends, among other things, on on the thickness of the fiber rope, the location of the reinforcement and the desired strength. In general, the thickness of the reinforcement is less than that of the fiberboard, although the thickness when the reinforcement is applied to the surface of the fiberboard and protrudes therefrom may be greater than the thickness of the fiberboard. Usually the thickness of the reinforcement (or the reinforcing fibers) is 0.1-10 times the thickness of the fibrous web, preferably 0.2-0.8 times the thickness of the fibrous web.

Suitable reinforcing materials are metal fibers, polymeric fibers and glass fibers. Electrostatically spun tubes and other artificial body parts have the advantage, compared to other tubes previously used for such purposes, that they provide thinner layers of encapsulating natural material, so tubes with smaller diameters can be used without the tube being clogged with natural tissue.

The fiber ropes of the present invention may be spun from a solution or dispersion of a polymer or starting compounds therefor. Polymers that can be easily spun from a solution are high molecular weight fiber-forming thermoplastics, and in particular polyurethane, polyamides and polyacrylonitrile can be mentioned. Polymers that can be easily spun from dispersions are polytetrafluoroethylene, polyesters and also those listed above. As an example of a starting compound for a polymer which can be spun from a solution, mention may be made of urea-formaldehyde which can be crosslinked after spinning by treatment with acid vapor.

7508781-7 ^r Water-soluble polymers, such as polyvinyl alcohol, polyvinylpyrrolidone and polyethylene oxide, can be spun from an aqueous solution. Although the possibility that nonwovens made of such materials can be used directly cannot be ruled out, they should preferably be made insoluble, at least to some extent, in aqueous media. for example by crosslinking with a suitable reagent.

When the products are spun from a dispersion, the spinning material preferably also contains a solution of an additional component, intended to increase the viscosity of the suspension and improve the fiber-forming properties. The best way to achieve this object has been found to be to add an organic polymeric material. desired, can be decomposed by sintering ·

The preferred spinning material thus consists of a solution or dispersion which preferably contains an organic polymer in such an amount that it can form fibers and which has such cohesive properties that the fibrous form is maintained in a subsequent curing of the fibers until they harden so much that they do not lose it. fibrous form when detached from a substrate, if desired ·

When the fiber ropes are spun from a solution, they contain point-bound fibers and are then often strong enough to be used without further treatment.

When the fiber ropes are spun from a dispersion, they often have a tendency to disintegrate, and they form only an agglomerate of different particles held together in the form of fibers by means of the present additional organic polymer component. Such fiber ropes are preferably sintered so that the particles soften and flow into each other, and thereby the fibers become point bonded. In the case of PTFE, the sintering preferably takes place at temperatures between 330 and 450 ° C, preferably between 370 and 390 ° C. Sterilization can be done simultaneously with sintering. In the case of PTFE, the sintering temperature is usually high enough to completely decompose any unwanted organic compound in the final product, such as materials added solely to increase the viscosity or emulsifier.

The additional organic component need only constitute a relatively small proportion (usually 0.001-12% by weight and preferably 0.01-3% by weight) of the suspension, and the exact concentration for a particular application can be readily determined by experiment.

The degree of polymerization of the additional organic component is preferably greater than about 2000 units linearly. A large number of such polymers are available. An important requirement is that the polymer should be soluble in the selected solvent or suspension diet, which is preferably water. Examples of water-soluble polymers are polyethylene oxide, polyacrylamide, polyvinylpyrrolidone and nolyvinyl alcohol. · When an organic medium is used in the production of the spinning material! either as the sole liquid solvent or as part thereof, a large number of additional organic polymers are available, such as polystyrene and polymethyl methacrylate.

The degree of polymerization of the polymer is selected taking into account the desired solubility and the ability of the polymer to impart desired cohesion and viscosity properties to the fiber-forming liquid.

It has been found that the viscosity of the fiber-forming liquid, whether due solely to the presence of the fiber-forming polymer or partly achieved by the additional organic polymer, should be higher than 0.1 P but not higher than 150 P. Preferably, it is between 0.5-50 P and more preferably between 1 and 10 P (the viscosities being determined at low shear rates). The viscosity required when a given additional organic polymer is used varies with the molecular weight of the polymer, i.e. the lower the molecular weight the higher the final viscosity required ·· On the other hand, as the molecular weight of the polymer increases, the concentration thereof required for good fiber formation decreases. By way of example, in the manufacture of fiber pads from polytetrafluoroethylene, it has been found that when a polyethylene oxide having a molecular weight of 100,000 is used as the additional organic polymer, a concentration of about 12% by weight relative to the PTFE content is required for satisfactory fiber formation. while at a molecular weight of 300,000 a concentration of 1-6% by weight may be sufficient. Furthermore, at a molecular weight of 600,000 a concentration of 1-4% by weight is satisfactory, while at a molecular weight of 4x10 a concentration as low as 0.2% by weight can give good fiber formation.

The concentration of the fiber-forming polymer depends on the amount required to achieve suitable fiber properties, and the concentration can also be affected by the need to produce a liquid of suitable viscosity and by the curing rate of the fibers. In the case of dispersions, it is thus possible to work with concentrations in the range of 25% by weight to saturation (in the case of a dispersion, saturation refers to the maximum concentration which can exist without losing the advantageous spinnability of the liquid), preferably in the range of 40-70% and even more preferably 50-60%, and in the case of solutions, concentrations within the unsaturated 10-60% by weight, preferably 20-35% by weight, can be used.

Of course, the concentration of each of the components must be weighed against the presence and concentration of the other components »their relative effect on viscosity, etc.

The spinning material must have a certain electrical conductivity which, however, can vary within fairly wide limits; for example, it is preferred to work with solutions with a conductance loss in the range 1x10 *⁶ 5xl0 “² S cm¹.

The spinning material can be brought into contact with the electrostatic field in any suitable manner, for example the spinning liquid can be introduced into this field at a suitable place by being fed to a nozzle from which the liquid dragee by means of the field, whereby fiber formation takes place. Any device can be used for this purpose.

Drops of spinning liquid can be introduced into the field in other ways "as will be readily appreciated by one skilled in the art" and the only requirement is that the drops within the field be kept at such a distance from the electrostatically charged surface that fiber formation occurs. The droplets can, for example, be inserted into the field on a continuous support, for example a metal wire.

Of course, when the liquid is fed into the field through a nozzle, several nozzles can be inserted simultaneously to increase the production rate of the fibers. An alternative device for introducing the fiber-forming liquid into the charged field is, for example, a perforated plate (the perforations being fed with fiber-forming liquid from a manifold).

In one embodiment of the invention, the surface to which the fibers are drawn is a continuous surface "such as a cylinder surface" over which a strip passes which is discharged from the charged area and carries with it the formed fibers which are adhered thereto. The accompanying drawings show such an arrangement and Fig. 1 is a schematic side view of a device for continuous production of fibers. In Fig. 1, 1 denotes a grounded syringe needle of metal »which is fed from a container with spinning material at a speed which is proportional to the production speed of the fibers. The belt 2 consists of gauze and is fed by means of a transport roller 3 and a non-driven roller 4, which roller 4 is electrostatically charged by a generator 5 (in the device shown a Van de Graaff machine).

7508781-7 _____ __________ ^r The removal of the fibrous rope 6 from the belt 2 can take place in a suitable manner, for example by suction or by means of an air jet, or the fibrous rope can be removed by means of a second belt or an additional roller arranged immediately adjacent thereto »Preferably it is cut off and lifted away · Fig. 1 shows how the fibrous material is taken up by a roller 7 which rotates towards the belt ·

The maximum distance between the nozzle and the charged surface is determined simply by experiment · It has been found, for example, that if one has a potential of the order of 20 kV, a distance of 5 * 35 cm is suitable, since the charge, the dimensions of the nozzle, the liquid flow rate , the size of the charged surface etc can vary, so can the maximum distance also vary, and it is therefore most appropriate to determine the distance by experiment ·

Alternative methods of collecting the fibers include the use of a large rotating collecting cylinder surface, substantially similar to the one described, on which the fibers are collected from another place on the surface by means of a non-electrically conductive collecting device instead of being carried further on the belt. the electrostatically charged surface is constituted by the wall of a rotating tube, which pipe is arranged coaxially with the nozzle and at a suitable distance therefrom · Alternatively, the deposition of fibers and the pipe production can take place on a cylindrical molding tool · The molding tool can be made of a number of different materials · A metal tool is preferred and especially one of aluminum · The pipe can be removed from the mold tool in different ways · In particular it can be mentioned that a polyurethane pipe is preferably peeled off from an aluminum tool, while the aluminum tool can be dissolved in sodium hydroxide solution when making a PTFE pipe · To facilitate the removal of the polyurethane pipe from the aluminum tool, the latter can be easily coated with a layer of flexible polyurethane foam ·

The electrostatic potential used is usually in the range 5-1000 kV, preferably 10-100 kV and preferably 10-50 kV · The desired potential can be achieved in any way · In Fig. 1 a conventional Van de Graaff machine is thus used, but other commercially available and more suitable devices are known and can be used »

It is of course important that the electrostatic charge is not conducted away from the charged surface, and when the charged surface is in contact with a secondary device, for example a fiber collecting strip, this strip should be made of non-conductive material (but it may na7508781- 7 io --......-. ......

of course not to insulate the charged surface from the fiber-forming material © It has been found suitable to use as a strip a thin mesh of terylene (RTM) with a mesh width of 3 mm ©) · Of course all supporting parts * supporting bearings etc. included in the device must be suitably isolated · Such precautions are readily apparent to those skilled in the art ·

In order to obtain high production rates, the curing of the fibers must. is rapid * and curing can be facilitated by the use of concentrated fiber-forming liquids (so that the minimum amount of liquid must be removed), volatile solvents (for example, the liquid may consist wholly or partly of low-boiling organic liquid) and relatively high temperatures in the vicinity of fiber formation · A gas stream , usually an air stream, can often accelerate the hardening of the fibers * especially if the gas is hot · By carefully directing the air flow, this can also be used to make the produced fibers occupy a desired position or direction. However, under the conditions set out in the examples, no special precautions are required)

I take to ensure a rapid cure · It has been shown that during the actual fiber formation and transport from the nozzle to the belt sufficient curing takes place (dewatering in the case described)? at ambient temperature, so no further curing treatment is necessary.

Fiber ropes made according to the present invention can have a thickness of a few microns to a few centimeters, and the selected dough thickness depends on the particular area of ​​use. Thus, for a coating, the thickness may be 5-100 μ, preferably 10-50 / U, and for a wound dressing, the thickness may be 25-1500 / U, preferably 50- |

1000 / U.!

The pore size of nonwovens made according to the invention can be 0.001-500 / U. For coatings, the fibrous material should be so porous that it allows penetration of cells into the nonwoven, and preferably the average pore dimension should be of the order of 5-25 / U and preferably between 7 and 15 / U. In the case of wound dressings, the size of the pores depends on the hydrophobicity used and the area of ​​use, ie whether the dressing is adhesive or not. Typical average values ​​for the pore dimension are for an adhesive wound dressing of polyurethane 50-100 .mu.m, and for a non-adhesive wound dressing of polytetrafluoroethylene 1-50 .mu.l.

The spun nonwoven fabric itself has a porosity in the range of 55-95%, but the porosity can be reduced to a value as low as 1% by a suitable compression finishing. Porous

7508781-7 the condition is conditioned by the particular area of ​​use, and typical values ​​are for a coating 75%, for an adhesive wound dressing 80% and for a non-adhesive wound dressing 60%. The term porosity here refers to the percentage of the total volume of the nonwoven that is free space.

When the spinning material consists of dispersions, the particle size may be between 0.01 and 1 and preferably it is between 0.1 and 0.3

The large surface content of the nonwoven fabric according to the invention enables a method of immobilizing a number of active substances so that they are forced to act on the applied area and do not penetrate the fibrous material. Substances that can be immobilized are enzymes, drugs and activated carbon. These substances can be added to the spinning solutions or dispersions, or the nonwoven fabric can be post-treated therewith.

Some applications require fiber ropes with a large surface content, ie fine fibers, and others require fiber ropes with high porosity. Methods are previously known by means of which a desired relationship between porosity and specific surface area can be achieved, and this is done by adding an electrolyte to the spinning material or by compressing the fibrous web after the spinning.

PTFE and polyesters are the preferred polymers for non-wettable products, but the possibility cannot be ruled out that they can be made wettable by mixing wettable additives. The wettable additive is preferably, but not necessarily, an inorganic material, preferably a difficult-to-digest material, and it should have a stability adapted to the conditions of use. Although the wettable additive material is preferably stable to the body. liquids and is not permeated too rapidly, if at all, the possibility cannot be ruled out that reaction or dissolution may in some cases be beneficial or desirable. Of course, it is also important that the presence of the wettable additive does not adversely affect the nonwoven fabric to such an extent that its handling or use is excessively difficult or that the dimensional stability is affected to an undesired extent. The preferred additive is an inorganic oxide or hydroxide, and examples of such materials are zirconia, titanium oxide, chromium oxide and oxides and hydroxides of magnesium and calcium, but other suitable materials or mixtures of such materials may also be used. Methods for incorporating a wettable additive into nonwovens have also been previously described.

7508781-7 ^r The invention is further illustrated by the following examples:

Example 1

The device was the one shown in Fig. 1. The belt consisted of a net of terylene (RTM) with a width of 15 cm, the diameter of the nozzle was 0.25 mm and it was placed 15 cm from the surface of the loaded roll, and the roll had a diameter of 10 cm and a width of 16 cm ·

To 80 g of an aqueous dispersion of PTFE, in which the average particle size was 0.22 microns (the specific gravity of the polymer by default was 2.190), which contained 3.6% by weight, based on the weight of the dis® z dispersion, of the surfactant Triton X100 (Rohm and Haas) and which had a solids PTFE solids content of 60% by weight, 20 g of a 10% (wt%) aqueous solution of polyethylene oxide (PEO) with an average molecular weight of 2 x 10⁵. The final composition contained 48% by weight PTFE and about 2% by weight PEO (the conductance was 1.8 x 10⁴ S cm '¹).

The suspension was mixed thoroughly and fed to the nozzle on a grounded sprayer. The electrodes were charged up to 20 kV, and a fine jet of liquid was drawn from the nozzle and collected on the receiving surface. The fibers thus collected were found to be dry and have an even cross-sectional area (1.0-2.0 / U). The fibers, which were very brittle, were carefully removed from the collector, dried at a temperature of 80 ° C and then sintered on a bed. of titanium dioxide at a temperature of 380 ° C for 15 minutes. After this treatment, it was found that the nonwoven fabric, which had a thickness of 200 .mu.m, had retained its fibrous structure and consisted of fibers having a diameter of 1 .mu.m / .mu.m. The fiber rope had good strength.

The contact angle of the fiber optic, measured by a modified method according to Owens and Wendt (Journal of Applied Polymer Science 1969, 13, p. 17411747) was 137 °, and in hydrostatic experiments (BS 2823) the fiber optic was not penetrated at a pressure of 50 cm.

A piece of fibrous tissue (1.3 cm in diameter) was applied to the surface of a wound on a rabbit, which wound consisted of a surface with total skin loss. No penetration of body fluid into the fibrous tissue was observed.

The preparation was repeated to obtain a spun fibrous web which in itself had a thickness of 800 .mu.m, the porosity 83% and the distribution of the pore size shown in Table 1. The fibrous material was compressed to a thickness of 300 .mu.l for 3 minutes at 100 ° C and a

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7508781-7 pressure of 28 kg / cm, and then heated at a temperature of 380 ° C for 15 minutes · The resulting fibrous material had a thickness of 400 / U, a porosity of 59% and the pore size distribution shown in Table 2 .

Table 1 Distribution of pore size in the spun nonwoven fabric as such

<td>Pore ​​diameter</td><td>(/ U)</td><td>% pores with smaller diameter</td>

<td> 100</td><td></td><td> 100</td>

<td> 60</td><td></td><td> 80</td>

<td> 8</td><td></td><td> 50</td>

<td> 2</td><td></td><td> 30</td>

<td>Table 2</td><td>Distribution of the fiber rope</td><td>pore size in the finished</td>

<td>Pore ​​diameter</td><td>(/ U)</td><td>% pores with smaller diameter</td>

<td> 100</td><td></td><td> 100</td>

<td> 15</td><td></td><td> 85</td>

<td> 2,5</td><td></td><td> 75</td>

<td> 2</td><td></td><td> 67</td>

<td> 1,2</td><td></td><td> 50</td>

Example 2

Example 1 was repeated with the exception that 1 g of potassium chloride was added to the spin composition to give a conductance of 1.2 x 10 -1.

cm · The resulting fibers had, after sintering, a diameter of 0.5-1.4 / U ·

Example 3

Example 1 was repeated with the exception that the polyethylene oxide had an average molecular weight of 2 x 10⁵The resulting fibers, after sintering, had a diameter of 0.9-1.6 .mu.m and the fibrous material had a thickness of 50 .mu.m.

The contact angle of the fibrous material, measured according to Example 1, was 123 °, and the fibrous rope carried a water column 16.5 cm long.

Example 4

Example 1 was repeated with the exception that the collecting surface consisted of metallic gauze, as shown in Fig. 2, on which the nonwoven fabric was supported during the subsequent sintering process.

7508781-7 ¹⁴ Example 5

The procedure of Example 1 was repeated using a spinning solution consisting of a 25% solution of a polyurethane (Daltoflex 33QS®) in dimethylformamide / methylethyl ketone (conductance 1 x 10⁶ S cm *¹·), And the collecting surface consisted of a metal tube 10 provided with a sleeve 11 of flexible polyurethane foam with open cells (see Fig. 3). The tube rotated at a speed of 100 rpm.

The polyurethane fibers formed had an average diameter of 2 = 4 microns, and they were collected in the form of a tube, which after completion of spinning had a thickness of about 2 mm and which could be peeled off from the foam layer.

Example 6

The procedure of Example 5 was repeated except that the product was collected as a flat fiber tuber with a thickness of 75 .mu.l.

The contact angle of the material, determined according to Example 1, was 73 ° and the fibrous material supported a water column with a height of 1.5 cm.

Some of this fibrous material was tested in the same manner as in Example 1 for its effectiveness. · The healing wound looked clean and well cared for and no coarse tissue was present.

Example 7

The procedure of Example 1 was repeated using an aluminum tube whose wall had a thickness of 0.5 mm as the collecting device, and PTFE was collected directly on the metal. A first layer of PTFB was applied to the aluminum tube, a dense wire coil of Wicrome '⁰(0.2 mm diameter) was then applied over the PTFE layer and on top of this a new layer of PTFE, after which the whole tube composition was sintered on the collecting device. The aluminum tube was then removed by dissolving in a concentrated solution of sodium hydroxide.

Example 8

The procedure of Example 7 was repeated, the spiral being made of glass fiber with a diameter of 0.02 mm. Several fiberglass layers were applied. Tubes with diameters of 1-10 cm were prepared according to the procedures described in Examples 7 and 8.

Example 9

A coating with an irregular contour was prepared by using a porous, electrically conductive matrix and applying suction pressure to the facing surface which was not to be coated with fibers, which suction pressure was

7508781-7 sufficient for the formed fiber rope to form to the contour of the matrix · The coating could, for example, be attached to an artificial body part by means of a suitable binder, for example nylon in formic acid or polyurethane in DMF.

Example 10

A protective mask for pollen filtration was prepared by making a model designed to fit just over the nose and mouth · The surface of the model was metallized so that it became electrically conductive to the required extent and a fiber layer of polyurethane with a thickness of 3 mm was applied to the model. removed from the model, resulting in a face mask with precise contour that was both light and relatively elastic ·

Fiber products, generally prepared as described in Example 1, with a diameter of 10 cm, an average fiber diameter of 1-2 microns, an average pore size of 5 microns and a porosity of about 80%, were used as air filters and, when the properties of the polymer were suitable therefore, as filters for liquids, eg water and beer · When the fiber rope was made of hydrophobic material, eg PTFE, pressure was needed to force a liquid through it. However, a certain degree of hydrophobicity was desirable, for example, when the fiber cloth was used as a diaphragm in, for example, oxygenation of blood and other liquids.

Using a cylindrical stainless steel mold (1.6 cm diameter) charged to 20 kV, a 10% solution of polyurethane (Daltomold 338E®) in dimethylformamide was electrostatically applied through a needle at a rate of 0.7 g PU / hrs. The tubular product formed had a wall thickness of 0.4 mm, a total pore volume of 1800 mm / g and an average pore radius of 9.4 microns, and it consisted of polymer knots of about 10 microns in size held together by fibers having a diameter of 0 mm. , 4 / U.

A portion of this product was inoculated by suturing to the descending portion of the aorta of a pig, and after 10 days the pig was sacrificed and the transplanted tissue examined. A close examination clearly showed that there were no signs of intravascular thrombosis. Histologically, there were signs of connective tissue and capillary growth between the fibers in the artificial part.

Example 12

Example 1 was repeated with the exception that as a spinner mate -. j

7508781-7

... -16

- (r) tial inserted a 10% (wt%) solution of a polyamide (Maranyl AlOO 2) in formic acid. The fibers were collected dry and had an even cross-section (0.06-0.5 ^).

The preparation was repeated using a 16% (wt%) solution of Maranyl A100 in formic acid. The collected fibers were dry and had an even cross-section (0.70-2.8yU). Example 13

Example 1 was repeated with the exception that a 12% (wt%) solution of polyacrylonitrile in dimethylformamide was used as the spinning material. The collected fibers were dry and had a uniform cross section (0.8-1.4 .mu.m). Example 14

Example 1 was repeated with the exception that a 10% (wt%) solution of a polyacrylonitrile / vinylidene chloride copolymer (Viclan A85 / 02®) in tetrahydrofuran was used as the spinning material. The collected fibers were dry and had an even cross-section (1.0-1.0 / U). Example 15

A wound dressing (Fig. 4) was prepared which consisted of a woven textile backing 12 with an adhesive layer 13 on one surface and a pad of absorbent material 14 covered with a fibrous layer 15 of electrostatically spun material, prepared in the manner described in Example 1. . The adhesive layer 13 on the substrate was protected by covering strips 16, which are intended to be removed before the wound dressing is used.

7508781-7