Hydrophilic medical device

Abstract

A medical device, such as a catheter, is disclosed, comprising a substrate and having on its surface, on at least a part thereof, a hydrophilic surface layer providing low-friction surface character of the medical device when wetted by a wetting fluid. At least one base layer of the substrate, including the hydrophilic surface layer, is made of a polymer blend comprising at least one base polymer and at least one hydrophilic polymer, and wherein the concentration of the at least one hydrophilic polymer is higher in the hydrophilic surface layer than in the rest of the base layer. A method for producing such a medical device is also disclosed.

Claims

1. A medical device comprising a substrate, having on its surface, on at least a part thereof, a hydrophilic surface layer providing low-friction surface character of the medical device when wetted by a wetting fluid, wherein at least one base layer is arranged as an extruded layer on the substrate, said base layer including said hydrophilic surface layer, is made of a polymer blend comprising at least one predominantly hydrophobic base polymer and at least one outer hydrophilic polymer, the base layer comprising said outer hydrophilic surface layer, an interior base layer and a transition layer, arranged between the interior base layer and the hydrophilic surface layer, wherein the concentration of said at least one hydrophilic polymer is higher in the hydrophilic surface layer than in the rest of the base layer, wherein the polymers in said hydrophilic surface layer are crosslinked, and wherein the transition layer provides a gradual increase in concentration of the at least one hydrophilic polymer from the interior base layer towards the hydrophilic surface layer, wherein, when in a dry state, the interior base layer comprises 25-75 wt % of the at least one hydrophilic polymer and the hydrophilic surface layer comprises at least 80 wt % of the at least one hydrophilic polymer.

2. The medical device of claim 1, wherein the at least one hydrophilic polymer comprises at least one material selected from: polyvinyl compounds, polysaccharides, polyurethanes, polyacrylates or copolymers of vinyl compounds and acrylates or anhydrides, poly (alkyl ether), i.e. polyethylene oxide or polypropylene oxide, polyoxyethylene, polyethylene oxide, polyvinyl-pyrrolidone, heparin, dextran, xanthan gum, polyvinyl alcohol, hydroxy propyl cellulose, methyl cellulose, copolymer of vinylpyrrolidone and hydroxy ethylmethyl acrylate or copolymer of polymethylvinyl ether and maleinic acid anyhydride, and copolymers thereof.

3. The medical device of claim 1, wherein the at least one hydrophilic polymer comprises at least one of polyethyleneoxide, poly(acrylic acid), polyvinyl-pyrrolidone and polysaccharide.

4. The medical device of claim 1, wherein the at least one hydrophilic polymer has a molecular weight of at least 50 kDa.

5. The medical device of claim 1, wherein the at least one base polymer comprises at least one of polyolefin and polyurethane.

6. The medical device of claim 1, wherein the medical device is a catheter.

7. The medical device of claim 1, wherein the substrate further comprises a filler material.

8. The medical device of claim 7, wherein the filler material comprises a calcium carbonate filler.

9. The medical device of claim 1, wherein the interior base layer comprises at least two different sub-layers, wherein an outer sub-layer, being closer to the hydrophilic surface layer, has a higher concentration of the at least one hydrophilic polymer than an inner sub-layer, being farther from said hydrophilic surface layer.

10. The medical device of claim 9, wherein said at least two different sub-layers are coextruded together.

11. A medical device assembly, comprising a medical device of claim 1, a container and a wetting fluid, wherein said container houses at least a part of the medical device together with the wetting fluid, so that the hydrophilic surface layer is maintained in a wetted state.

12. The medical device of claim 1, wherein the material composition of the hydrophilic surface layer when in a dry state comprises at least 95 wt % of the at least one hydrophilic polymer.

13. The medical device of claim 1, wherein the polymer blend in the interior base layer comprises 25-50 wt % of the at least one hydrophilic polymer.

14. The medical device of claim 1, wherein the polymer blend in the interior base layer comprises 50-75 wt % of the at least one base polymer.

15. The medical device of claim 1, wherein the at least one hydrophilic polymer has a molecular weight of at least 200 kDa.

16. The medical device of claim 1, wherein the medical device is a urinary catheter, wherein the hydrophilic surface layer is provided at least on an insertable part thereof.

17. The medical device of claim 1, wherein the concentration of the at least one hydrophilic polymer is essentially the same in the entire interior base layer.

18. The medical device of claim 1, wherein the interior base layer forms at least 95% of the total thickness of the base layer.

19. The medical device of claim 1, wherein the at least one base polymer comprises at least 75 wt % of polyolefin and/or polyurethane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) By way of example embodiments of the invention will now be described with reference to the accompanying drawings in which:

(2) FIG. 1 illustrates an embodiment of a catheter according to the invention;

(3) FIG. 2 is a cross-sectional view of an exemplary catheter assembly in accordance with an embodiment of the invention; and

(4) FIG. 3 is a cross-sectional view of an exemplary catheter assembly in accordance with another embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

(5) In the following detailed description preferred embodiments of the invention will be described. However, it is to be understood that features of the different embodiments are exchangeable between the embodiments and may be combined in different ways, unless anything else is specifically indicated. It may also be noted that, for the sake of clarity, the dimensions of certain components illustrated in the drawings may differ from the corresponding dimensions in real-life implementations of the invention, e.g. the length of the catheter. Further, even though the following detailed description focuses on a urinary catheter, it is to be appreciated by the skilled reader but is equally applicable to other types of catheters, e.g. intended to be introduced into other type of body-cavities than the urethra, and is also applicable to many other types of medical devices having a need for a hydrophilic surface.

(6) A catheter 1 as illustrated in FIG. 1, comprises a flared rearward portion 2 and an elongate shaft or tube 3 projecting forwardly from the rearward portion 2. An open-ended internal lumen (not shown) extends from the rear end of the rearward portion 2 to a drainage aperture 4 in a rounded tip 5 of the elongate tube 3. The catheter preferably has only one, single internal lumen. The drainage openings are preferably arranged close to the proximal, insertable end of the catheter. The insertable tip of the catheter is preferably closed, and is preferably formed in a rounded shape. The rearward portion 2 is preferably formed as a flared end, and may function as a connector of the catheter 1, being connectable to other devices, such as a urine collection bag, a drainage tube or the like.

(7) At least a part of the elongate tube 3 forms an insertable length to be inserted through a body opening of the user, such as the urethra in case of a urinary catheter. By insertable length is normally meant that length of the elongate tube 2 which is insertable into the urethra of the patient. Typically, this will be 80-140 mm for a female patient and 200-350 mm for a male patient. At least the insertable part of the catheter is preferably provided with a hydrophilic surface layer, to be discussed in more detail in the following.

(8) The catheter is preferably arranged in a closed container, functioning as a package, and optionally also as a sterile barrier, in a sterilized state. The container houses at least the insertable part of the catheter, and preferably also a wetting fluid to maintain the catheter in an activated, wetted state. Hereby, the catheter becomes immediately ready to use upon withdrawal from the package.

(9) In FIG. 2, a catheter assembly 20 is schematically illustrated in which the entire catheter 1 is enclosed within the container 21. Here, it is preferred that the entire catheter is arranged in contact with the wetting fluid 23, thereby ensuring that an adequate wetting is maintained at all times. The container is preferably made of a gas-impermeable material, such as a material comprising an aluminum barrier layer. The container is preferably arranged with a shape resembling the shape of the catheter, having a narrow elongate part housing the insertable part of the catheter, and a somewhat wider rearward part 22, housing the connector end of the catheter. Hereby, the package encloses the catheter narrowly, thereby limiting the volume between the catheter and the package walls. This type of package is per se further disclosed in U.S. Pat. No. 6,848,574 by the same applicant, said patent hereby being incorporated in its entirety by reference. However, the container may also have many other shapes and dimensions, such as being rectangular etc.

(10) In FIG. 3, an alternative embodiment of a catheter assembly is illustrated. Here, only a part of the catheter, including the insertable part, is enclosed within the package together with the wetting fluid.

(11) The receptacle 31 could e.g. be connected to the catheter, and in particular to the connector. For example, the connection could be provided by means of a welding joint arranged between the catheter and the receptacle, or by means of a shrink fit, an adhesive or the like. The catheter lumen may be closable by means of a cap or cover 32 arranged to sealingly close the connector opening. However, other ways of providing a closure of the lumen are feasible as well, such as arranging a breakable membrane somewhere in the lumen.

(12) The wetting fluid 23 is here in contact only with the catheter shaft. Thus, the entire insertable, hydrophilic part is maintained immersed in the wetting fluid, whereas non-insertable parts are to at least some extent outside the package, and without contact with the wetting fluid. However, similar to the embodiment above, the catheter is maintained in a activated, ready-to-use condition. In order to preserve this wetted condition the compartment formed by the receptacle and the catheter is preferably gas sealed, and further, the receptacle is preferably gas impermeable. Catheter assemblies of this general type are further disclosed in US 2009/0200187 by the same applicant, said document hereby being incorporated in its entirety by reference.

(13) In use, the receptacle may, in both the embodiments discussed above, simply be opened, and the catheter could immediately be introduced into the patient.

(14) The receptacle housing the wetting fluid and part of or the whole catheter is preferably a gas impermeable material. For example one or several of the following gas impermeable materials could be used: aluminium foil laminate, poly(vinylidene chloride) or laminate comprising a metallised film, such as metallised poly(ethylene terepthalate), or silicon oxide coated film, or a laminate comprising aluminum oxide.

(15) In case the catheter is maintained in a wetted state during storage, such as in the above-discussed assembly embodiments, the catheter is immediately ready for use and insertion upon withdrawal from the container. In this ready-so-use case, the catheter may be stored immersed in a wetting liquid, as discussed in the foregoing. However, the catheter may also be stored in an activated state, where all wetting fluid is present within the hydrophilic surface layer and no or very limited excess wetting fluid is present in the rest of the container. Further, the wetting fluid need not be present in liquid form, but may also be present in the form of gas, e.g. by providing a moist, vapor containing atmosphere in the container. However, the catheter may also be stored in a dry state. In such a case, the wetting fluid may be arranged in a separate compartment or pouch of the package, for wetting and activation of the catheter immediately prior to use. When maintained in a dry state, it is also possible to wet the catheter with a wetting fluid provided from an external supply.

(16) The wetting fluid is preferably a water-based liquid, i.e. using plain water or a solution comprising water as a solvent, such as saline or other.

(17) The catheter tubing substrate material is produced by preparing a polymer blend comprising at least one base polymer and at least one hydrophilic polymer and forming a substrate or a base layer in the substrate from said polymer blend. The preparation of the blend may be made by a compounding step. The forming may e.g. be obtained by extrusion. The substrate is then arranged in a wetting liquid. Hereby, the at least one hydrophilic polymer migrate(s) towards a surface of the substrate. After a sufficient waiting time, which may amount to only a few minutes, or which may have a duration of hours or even days, the substrate is irradiated, thereby forming cross-linking between the polymers. This cross-linking prohibits further migration of the hydrophilic polymer(s), whereby a stable hydrophilic surface layer, comprising a higher concentration of the hydrophilic polymer(s) than said polymer blend, is formed on the surface of the substrate.

(18) Thus, the resulting catheter comprises on at least a part thereof, a hydrophilic surface layer providing low-friction surface character of the medical device when in wet state, and the substrate, or at least a base layer of the substrate, is made of a polymer blend comprising the at least one base polymer and the at least one hydrophilic polymer, and wherein the concentration of said at least one hydrophilic polymer is higher in the hydrophilic surface layer than in the interior of the base layer or substrate. Thus, the hydrophilic surface layer is formed not as a coating, but as an integral part of the base layer or substrate.

(19) The substrate may be formed in its entirety by the base layer, and thus be entirely formed by the specified polymer blend. However, the substrate may also comprise one or more additional support layer(s), preferably being arranged inside or underneath the base layer. For example, the base layer may be attached to a support layer (or second base layer) made of a thermoplastic polymer material, such as polyurethane, polyolefin or the like. In case of a catheter, such an additional support layer is preferably arranged inside the base layer comprising the specified polymer blend, so that the hydrophilic surface layer faces the exterior of the catheter. Attachment of the base layer to a further support layer may be obtained in various ways, such as by co-extrusion and the like.

(20) The step of arranging the substrate in a wetting liquid preferably comprises arranging the medical device in the container together with the wetting liquid, and closing the container, as illustrated in FIGS. 2 and 3. Hereby, the subsequent irradiating step may also effect sterilization of the medical device.

(21) The concentration of the hydrophilic polymer may be essentially the same in the entire of the interior of the base layer or substrate, i.e. with a homogeneous blend throughout the interior of the base layer/substrate. However, instead of being entirely homogeneous, the interior of the base layer may comprise at least two different sub-layers, wherein an outer sub-layer, being closer to the hydrophilic surface layer, has a blend of base polymer(s) and hydrophilic polymer(s) with a higher concentration of the hydrophilic polymer(s) than in the corresponding blend of the inner sub-layer, being farther from said hydrophilic surface layer. These two different sub-layers, which both comprise blends of base polymer(s) and hydrophilic polymer(s), may e.g. be coextruded together.

(22) The at least one hydrophilic polymer may comprise at least one material selected from: polyvinyl compounds, polysaccharides, polyurethanes, polyacrylates or copolymers of vinyl compounds and acrylates or anhydrides, poly (alkyl ether), i.e. polyethylene oxide or polypropylene oxide, such as polyoxyethylene (POE), and in particular polyethylene oxide (PEO), polyvinyl-pyrrolidone (PVP), heparin, dextran, xanthan gum, polyvinyl alcohol, hydroxy propyl cellulose, methyl cellulose, copolymer of vinylpyrrolidone and hydroxy ethylmethyl acrylate or copolymer of polymethylvinyl ether and maleinic acid anyhydride, and copolymers of these. Preferably, the hydrophilic polymer is a meltable polymer.

(23) The hydrophilic polymer is preferably at least one of polyethyleneoxide (PEO), poly(acrylic acid), polyvinyl-pyrrolidone (PVP) and polysaccharide, such as carboxy methyl cellulose. In a particularly preferred embodiment, the hydrophilic polymer(s) comprises polyethyleneoxide.

(24) The hydrophilic polymer(s) preferably has a relatively high molecular weight. Preferably, the hydrophilic polymer(s) has a molecular weight of at least 50 kDa, and preferably at least 100 kDa, and most preferably at least 200 kDa.

(25) The at least one base polymer is preferably a predominantly hydrophobic polymer. For example, the at least one base polymer may comprise at least one of polyolefin and polyurethane, such as thermoplastic polyurethane.

(26) In case polyolefin is used, the polyolefin may comprise at least one polymer selected from the group: polyethylene, polypropylene, and styrene block copolymer (SEBS). The base polymer(s) may also comprise polyolefin and at least one composition having molecules with active hydrogen(s), the molecules preferably being molecules where the active hydrogen(s) is bound to the molecules via nitrogen. The compound having molecules with active hydrogen(s) can be either a polymer or smaller molecules, or various combinations of such polymers/molecules. Examples of such compositions having molecules with active hydrogen groups are alcohols, amides, amines, urethanes and acids, and in particular amides, amines and urethanes are preferred.

(27) The base layer or substrate may further comprise a filler material, such as calcium carbonate filler.

(28) In order to obtain good mechanical properties, the substrate materials is preferably prepared and composed in such a way that it fulfills at least some of the following requirements, and preferably essentially all of them: The material should have a hardness adequate for the intended use. For example for urinary catheter, the hardness Shore A should preferably be in the range 75-85, and most preferably within the range 78-82. Possibility to be sterilized by known sterilization methods. In particular it is preferred that the substrate has a radiation resistance such that it can endure at least 25 kGy, and preferably at least 50 kGy, essentially without degradation, in order to enable radiation sterilization of the medical device. The material should exhibit low resilience. The material should have good kinking properties. The material should preferably be meltprocessable, extrudable, or usable for molding, and in particular useable for injection molding. The substrate material should preferably be biocompatible. The substrate material should preferably have good dimension stability. In particular, it is preferred that the longitudinal shrinkage of the catheters as a result of the coating process is less than 5%, and preferably less than 1%, of the original length.

(29) Experiments

(30) In a first line of comparative experiments, a PEO coating was co-extruded on top of a poyolefin based substrate. However, it was found that the resulting coated substrates were not useable for catheters. The PEO coating became very thick, uneven and eventually dissolved when wetted.

(31) In a second line of comparative experiments, attempts were made to make the substrate solely of PEO. Even though this substrate has adequate low friction properties on the surface, it could not be used as a catheter material. During wetting, the substrate was severely deformed, swelled extensively, became unstable, with poor mechanical properties, etc.

(32) In experiments in accordance with the invention, the following materials were used: PEO: Polyox WSR N80 from Dow Chemical. This polyethyleneoxide is meltable, and has a molecular weight of about 200 kDa. PVP: PVP K90, sold by e.g. Sigma Aldrich. This polymer disintegrates at about 190 deg. C. but blends well below such temperatures, and has a molecular weight of above 300 kDa. T60: A thermoplastic polyurethane, sold as Tecophil HP-60D-20 by Lubrizol, having components allowing some uptake of water. T93: A thermoplastic polyurethane, sold as Tecophil HP-93-A-100 by Lubrizol, having components allowing even higher uptake of water (i.e. higher than for T60). PU: A thermoplastic polyurethane with very low hydrophilicity, sold as Pellethane 5863-82AE by Lubrizol. PB: A polyolefin base polymer based on the commercially available polyolefin material Meliflex®. PE: A block copolymer of polybutylene terepthalate (PBT) and polyether glycol terephthalate sold under the tradname Skypel by SK Chemicals. Filler: A calcium carbonate filler, Imercarb 10L, from Imerys Carbonates. Compatibilizer: Fusabond E226 from DuPond.

(33) In a first line of experiments, various blends where prepared, comprising different blends of a base polymer and PEO. The blends were compounded by means of a Brabender compounder. The hygroscopic materials, such as T60, T93 and PEO were dried prior to compounding, in order to get a more homogeneous blend. In the following table 1, the type and amount of base polymer is specified, as well as the operational conditions of the compounder (temperature, mixing time and mixing rate).

(34) TABLE-US-00001 TABLE 1 Samples mixed in compounder Base polymer PEO Mixing Mixing Base amount amount T time rate Sample polymer (g) (g) (deg. C.) (mts) (rpm) A1 T93 5 10 140 2 20 A2 T93 8 8 140 1.5 30 A3 PU 5 10 140 2 30 A4 PU 8 8 140 4 40 A5 T60 8 8 140 2 40 A6 PB 10 5 170 4 50 A7 PB 12 4 160 4 50 A8 PU 10 5 140 1.5 50 A9 PU 8 8 120 1.5 50

(35) It was found that all the samples blended adequately, and in particular the polyurethane blended very well. This was also confirmed by study of films pressed out of the blended materials, and wetted for 30 seconds before being wiped off. By micrographs comparing the surface before and after wetting it was seen that structures were formed on the material, indicating migration out of the PEO.

(36) Further, all the samples provided a much more slippery surface than the base polymer in itself when wetted.

(37) In a further experiment, some of the samples, having PU or T93 as a base polymer, were placed in a vial filled with 1 mL water. After a certain time, ranging from 3 minutes to 1 hour, the water was analyzed, to determine the amount of PEO that had leached into the water. The analysis was made with fast liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF).

(38) The results of this experiment are summarized in table 2 below, where the dimensions of the samples prior to wetting are specified, together with the weight of the sample, the leaching time (i.e. the time during which the sample was immersed in the water), the PEO content of the blend of the sample, the base polymer of the blend, and the determined PEO concentration of the water after leaching.

(39) TABLE-US-00002 TABLE 2 Leaching of PEO into water Dimensions Weight PEO PEO when non- when non- Leach content in concentration wetted wetted time sample Base in the water (mm) (g) (mts) (wt %) polymer (g/l) 5 × 10 × 1.7 0.097 60 40 T93 0.74 5 × 10 × 0.8 0.054 3 75 PU 0 6 × 10 × 1 0.061 3 50 T93 0 5 × 10 × 1.5 0.11 3 75 PU 0 5 × 10 × 1.5 0.11 60 75 PU 2.51 5 × 10 × 1.5 0.09 30 75 PU 1.10 5 × 10 × 1 0.064 30 50 T93 0.40 5 × 10 × 1.2 0.074 3 50 PU 0.10 5 × 10 × 1.2 0.077 30 50 PU 0.47 5 × 10 × 1.2 0.072 60 50 PU 1.05 5 × 10 × 1.2 0.061 60 50 PU 0.82 5 × 10 × 1 0.03 3 50 PU 0.04 5 × 10 × 1 0.049 30 50 PU 0.38

(40) It can be seen that already within a few minutes, a substantial amount of PEO has leached out from many of the materials. This confirms the finding that PEO immediately begin to migrate from the surface when in contact with water. Further, it can be determined that the amount of leached out PEO increases with leaching time. Thus, the amount of migrated PEO can be controlled by inter alia control of the leaching time. Further, the amount of leached out PEO increases when the concentration of PEO in the blend is higher.

(41) Thus, based on this, it is deduced that the migration of the hydrophilic polymer towards the surface of the substrate, and eventually into the surrounding fluid, can be very efficiently controlled inter alia by controlling how long the wetting is allowed to proceed prior to cross-linking. The leaching and migration effect only occurs prior to cross-linking, After cross-linking, it has been found that the migration immediately stops, and that essentially no hydrophilic polymer is leached out into the wetting liquid when the catheter is immersed.

(42) In yet another line of experiments blends were prepared by a first run in a Brabender extruder, and then followed by a second run in the extruder, to blend the materials further, and to produce an extruded substrate. In the following table 3, the type and amount of base polymer is specified, as well as the operational conditions of the extruder temperature, mixing time and mixing rate).

(43) TABLE-US-00003 TABLE 3 Samples mixed in extruder PU T93 PEO Mixing Mixing amount amount amount T time rate Sample (wt %) (wt %) (wt %) (deg. C.) (mts) (rpm) B1 13 87 120 2 70 B2 33 66 120 2 70 B3 50 50 120 2 70 B4 66 33 120 2 70 B5 25 75 120 2 70 B6 33 66 120 2 70

(44) It was found that all the samples blended adequately, and in particular the polyurethane blended very well, and all the samples provided a much more slippery surface than the base material in itself when wetted.

(45) Solid tubes were made by extrusion of these sample materials. Sample tubes were allowed to swell for 2 hours in water, and the swelling and wetting of the tubes were studied. When wetted, an outer layer of wetted, swelled material is formed around a core of non-wetted, un-swelled material. Over time, the outer layer increases in thickness, and the core diminishes gradually, to a point where the entire material is swelled. If the diameter of the solid tube initially is A, in un-swelled condition, and after 2 hours of swelling, the thickness of the swelled layer is b, and the diameter of the remaining inner core of un-swelled material is a, we consider the amount of swelling to be (2×b)/(A−a) and the amount of wetting to be (A−a)/A. The swelling and wetting of the samples is presented in the table below.

(46) TABLE-US-00004 TABLE 4 Swelling and wetting Sample Swelling (%) Wetting (%) B1 158 100 B2 144 76 B3 147 63 B4 129 60 B5 243 82 B6 N/A (boundaries became 63 to diffuse to enable measuring)

(47) It can be deduced from this that blends with PU swells less than blends with T93 as base polymer, but the percentage of the tube that has been wetted after 2 hours is comparable. In general, for both types of base polymers, a higher ratio of PEO provides a faster wetting process and a higher degree of swelling.

(48) The tubes were then packaged in gas impermeable packages together with different amounts of water, but in a volume that assured complete wetting of the tubes. Tubes packaged with less water were hence packaged in smaller container, with a “tighter” fit. The assemblies were further subject to irradiation at 56 kGy after one hour.

(49) Further, the friction and durability of the hydrophilic surface layer of the tubes were in all cases subjectively determined to be very good. However, in order to confirm this, some of the samples were evaluated using a Harland FTS Friction Tester, available from Harland Medical Systems, with a clamp force of 100 g and a pull speed of 1.0 cm/s. For some of the samples, the friction measurement was also done repeatedly for several times, in order to determine the durability of the hydrophilic surface layer. The results of this are presented in the table below.

(50) TABLE-US-00005 TABLE 5 Friction coefficient Friction Friction Friction Sample (1.sup.st time) (5.sup.th time) (10.sup.th time) B3 0.083 0.133 0.166 B4 0.093 N/A N/A B5 0.098 0.096 0.100 B3 - tight 0.091 0.090 0.091

(51) Thus, all samples showed a very low friction coefficient, which is in all cases similar to the friction coefficient of the best commercially available hydrophilic urinary catheters on the market today, such as the hydrophilic urinary catheters sold as LoFric® by Wellspect HealthCare (previously Astra Tech).

(52) Further, the hydrophilic surface layer is in all cases very durable, with limited deterioration when subject to the extensive wear of 5 or 10 measurement cycles. In two of the samples, the hydrophilic surface layer appears to be totally unaffected by this wear.

(53) “B3—tight” was a sample packed with a very limited amount of water. Since the PEO leached out from the catheter cannot diffuse away from the surface, it formed a more compact gel around the material. This improved the durability of the hydrophilic surface layer.

(54) Further, some packed and cured B3 samples were aged in a climate chamber for 6 months. No signs of degradation of the material could be detected.

(55) Further, the B4 blend was used to extrude catheter tubes, and after cutting one end was formed into a catheter tip through melting and molding, and holes were punched out using a side punch. The produced catheter was found to be useable as a urinary catheter, and have comparable properties and characteristics as urinary catheters on the market today. Further, the friction coefficients of the catheter was found to be the same as for the solid tubes discussed above.

(56) In a further experiments, PEO was blended with PE in a compounder. Various compositions of the blend was used, some with a compatibilizer (Fusabond E226 from DuPond). Small amounts of filler was also added in some of the samples. The compositions of the samples are presented in Table 6 below.

(57) TABLE-US-00006 TABLE 6 Samples mixed in compounder Calcium Base PEO Compatibilizer carbonate Mixing Mixing polymer PE amount amount amount T time rate Sample (wt %) (wt %) (wt %) (wt %) (deg. C.) (mts) (rpm) C1 84 10 6 190 2 20 C2 78 10 6 6 190 2 20 C3 40 48 12 180 2 20

(58) All the compounds blended very well. This was also confirmed by study of films pressed out of the blended materials, and wetted for 60 seconds before being wiped off. By micrographs comparing the surface before and after wetting it was seen that structures were formed on the material, indicating migration out of the PEO.

(59) Further, all the samples provided a much more slippery surface than the base material in itself when wetted.

(60) In yet further experiments, PEO was blended with PU, and PVP with PU, respectively, in a compounder. The compositions of the samples are presented in Table 7 below.

(61) TABLE-US-00007 TABLE 7 Samples mixed in compounder Base Calcium polymer PU PEO PVP carbonate Mixing Mixing amount amount amount amount T time rate Sample (wt %) (wt %) (wt %) (wt %) (deg. C.) (mts) (rpm) D1 60 20 20 140 1 30 D2 80 20 150 5 50 D3 60 20 20 150 5 50

(62) Again, all the compounds blended adequately well. This was also confirmed by study of films pressed out of the blended materials, and wetted for 60 seconds before being wiped off. By micrographs comparing the surface before and after wetting it was seen that structures were formed on the material, indicating migration out of the PEO and PVP, respectively.

(63) Again, all the samples provided a much more slippery surface than the base material in itself when wetted.

CONCLUSION AND SUMMARY

(64) The invention has now been discussed in relation to different embodiments. However, it should be appreciated by those versed in the art that several further alternatives are possible. For example, the features of the different embodiments discussed above may naturally be combined in many other ways.

(65) It is further possible to use the invention for other types of medical devices, and for example for other types of catheters than urinary catheters, such as vascular catheters or the like.

(66) Many different materials could also be used for the different parts of the catheter assembly. Specifically, other blends of various base polymers and hydrophilic polymers may be used, and additives, such as fillers, compatibilizers etc may be included. It is also possible to include e.g. an osmolality increasing agent, such as NaCl directly in the polymer blend.

(67) It will be appreciated by those versed in the art that several such alternatives similar to those described above could be used without departing from the spirit of the invention, and all such modifications should be regarded as a part of the present invention, as defined in the appended claims.