Injection molded medical devices made from high molecular weight polyethylene

Abstract

A high molecular weight polyethylene polymer is formulated so that the polymer can be injection molded. The polyethylene polymer has a viscosity value greater than about 400 ml / g and a melt flow rate greater than about 0.9 g / 10 min. The polyethylene polymer has high purity and is particularly well suited for the production of medical products.

Description

[0001] Related Applications

[0002] This application is based upon and claims the benefit of priority of U.S. Provisional Patent Application No. 62 / 823,166, filed on March 25, 2019, which is incorporated herein by reference. Background Art

[0003] Polyethylene has been recognized as an extremely useful engineering material in a variety of applications, in part due to its unique combination of desirable properties. For example, high molecular weight polyethylene polymer particles can exhibit improved abrasion resistance, chemical resistance, lubricity, impact strength, stress crack resistance, heat deflection temperature, wear resistance, and energy absorption capacity at high stress rates compared to other thermoplastic polymers.

[0004] High molecular weight polyethylene polymers generally include linear polyethylene polymers and can be distinguished from other polyethylene grades by a very high degree of polymerization. In fact, the high degree of polymerization is responsible for the fact that these polymers do not flow well when melted and actually show a melt flow index of 0 grams per 10 minutes. Therefore, special processing methods such as pressure sintering and ram extrusion are used to form these polymers into objects.

[0005] However, as described above, high molecular weight polyethylene polymers have various excellent properties that make them suitable for many applications. For example, high molecular weight polyethylene polymers can have very high impact strengths that are maintained even at very low temperatures. In fact, high molecular weight polyethylene polymers can be produced that do not break when subjected to notched impact strength testing as tested by ISO 179.

[0006] High molecular weight polyethylene polymers also have a relatively wide operating temperature range and are extremely wear resistant. In addition, high molecular weight polyethylene has excellent wear resistance, which can be as good as or better than steel.

[0007] High molecular weight polyethylene polymers can also be produced to be biocompatible. As such, the polymers have been used in the past to produce various medical devices, such as orthopedic implants.

[0008] However, there is a need for high molecular weight polyethylene polymers that can be injection molded to produce medical products. The ability to injection mold high molecular weight polyethylene polymers can, for example, allow the polymers to be used to produce smaller medical devices or to more efficiently produce a variety of different types of medical products. Therefore, there is a need for high molecular weight polyethylene polymers that can be injection molded while still retaining many of the properties exhibited by low flow polyethylene polymers. Summary of the invention

[0009] The present disclosure generally relates to a high molecular weight polyethylene polymer composition that is well suited for producing medical products. The high molecular weight polyethylene polymer is, for example, biocompatible and can be used in a variety of different types of medical applications, including implants, prosthetic devices, drug delivery devices, and the like. According to the present disclosure, the high molecular weight polyethylene polymer is formulated to have melt flow properties sufficient to allow the polymer to be used in an injection molding process to produce a medical product.

[0010] In one embodiment, for example, the present disclosure relates to a medical device comprising an injection molded polymeric article. The polymeric article comprises a high molecular weight polyethylene polymer. When measured according to ISO 1133 at 190° C. and with a load of 21.6 kg, the melt flow index of the high molecular weight polyethylene polymer is greater than about 0.8 g / 10 min, such as greater than about 0.9 g / 10 min, and typically less than about 3 g / 10 min, such as less than about 2 g / 10 min. In addition, when tested according to ISO 1628-3, the viscosity value of the high molecular weight polyethylene polymer can be greater than about 400 cm 3 / g, for example greater than about 500cm 3 / g, and is usually less than about 900 cm 3 / g. For example, the molecular weight of the high molecular weight polyethylene polymer can be greater than about 350,000 g / mol, such as about 500,000 g / mol to about 5,000,000 g / mol. Molecular weight as used herein is determined according to ASTM D4020 testing. When tested according to ISO 1183-1 Test Method A, the specific gravity of the high molecular weight polyethylene polymer can be about 0.93 g / cm 3 To about 0.97g / cm 3 .

[0011] The high molecular weight polyethylene polymer is biocompatible and can be produced to meet the testing requirements of the ISO 10993 test. For example, the high molecular weight polyethylene polymer can pass the ISO 10993-11 test for systemic toxicity, can pass the ISO 10993-10 test for intradermal reactions, can pass the ISO 10993-6 test for two-week muscle implantation, can pass the ISO 10993-5 test for cytotoxicity, can pass the ISO 10993-3 test for genotoxicity, can pass the ISO 10993-4 test for hemolytic reactions, and can pass the USP 661 test for physical chemistry.

[0012] The polymer objects of the present disclosure can be made mainly of the high molecular weight polyethylene polymer. For example, the polymer object can contain an amount greater than about 70wt%, such as an amount greater than about 80wt%, such as an amount greater than about 90wt%, such as an amount greater than about 95wt% of the high molecular weight polyethylene polymer. The high molecular weight polyethylene polymer can be a homopolymer or can include a copolymer. For example, in one embodiment, the high molecular weight polyethylene polymer can be a copolymer of ethylene and at least one monomer including propylene, butene or a mixture thereof. In one embodiment, the high molecular weight polyethylene polymer can be used to produce an object and then cross-linked.

[0013] The polymer object may contain various other components besides the high molecular weight polyethylene polymer. For example, the polymer object may contain active pharmaceutical ingredients, imaging agents, reinforcing materials, and the like.

[0014] Various different types of medical devices can be prepared from the high molecular weight polyethylene polymer. For example, the medical device can include a prosthesis or an implant. In one embodiment, the medical device can have a tubular shape for conveying liquids or for covering electrical components (e.g., wires).

[0015] In one embodiment, the polymeric object may be included in a chip, an RFID device, a pump, a surgical instrument, or a neurostimulator. In other embodiments, the polymeric object may include a feeding tube, a catheter, an expandable balloon, a stent, a heart valve, a cochlear implant, a craniomaxillofacial implant, an artificial cartilage, a gastric ring, a vascular clamp, an aneurysm clip, a spinal plug, a base-plate stem cap for an artificial joint, a muscle implant, a nasopharyngeal implant, a laryngeal implant, an oromucosal insert, an intrauterine device, a vaginal contraceptive ring, or a tooth fiber. In another embodiment, the medical device may include a drug delivery device, a transdermal patch, or a subcutaneous implant.

[0016] The present disclosure also relates to a method for injection molding a medical product. In another embodiment, the present disclosure relates to a method for implanting the above-mentioned medical device into a patient.

[0017] Other features and aspects of the disclosure are discussed in more detail below. DETAILED DESCRIPTION

[0018] Those skilled in the art will appreciate that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the present disclosure.

[0019] In general, the present disclosure relates to a polyethylene composition comprising a high molecular weight polyethylene polymer that is not only biocompatible but also capable of being melt processed by injection molding. The polyethylene polymer composition is well suited for producing a variety of different types of medical products. Because the polymer composition can be injection molded, the polyethylene polymer composition is particularly well suited for producing small medical devices or other medical objects where injection molding provides advantages in terms of production efficiency or provides a variety of other benefits and advantages.

[0020] The polyethylene polymer present in the polymer composition has a molecular weight as high as possible while still being able to be injection molded. The polyethylene polymer is, for example, a high molecular weight polyethylene polymer having a melt flow rate of at least about 0.5 g / 10 min, such as at least about 0.7 g / 10 min, such as at least about 0.9 g / 10 min, such as at least about 1.1 g / 10 min, such as at least about 1.3 g / 10 min, and typically less than about 2.5 g / 10 min, such as less than about 2.3 g / 10 min, such as less than about 2 g / 10 min, such as less than about 1.8 g / 10 min. The melt flow index is measured at 190 ° C with a load of 21.6 kg according to ISO 1133 test.

[0021] The high molecular weight polyethylene polymer has high purity and is biocompatible. More specifically, the polyethylene polymer in the composition of the present disclosure passes at least most of the requirements of the ISO 10993 test. For example, the polyethylene polymer passes the ISO 10993-11 test for systemic toxicity, passes the ISO 10993-10 test for intradermal reaction, passes the ISO 10993-6 test for two-week muscle implantation, passes the ISO 10993-5 test for cytotoxicity, passes the ISO 10993-3 test for genotoxicity, passes the ISO 10993-4 test for hemolytic reaction, and passes the USP 661 test for physical chemistry.

[0022] The high molecular weight polyethylene may be a homopolymer, a copolymer or a blend thereof. In one embodiment, the polyethylene may be a homopolymer.

[0023] In another embodiment, polyethylene can be a copolymer. For example, polyethylene can be a copolymer of ethylene and another olefin containing 3 to 16 carbon atoms, for example, containing 3 to 10 carbon atoms, for example, containing 3 to 8 carbon atoms. These other olefins include but are not limited to propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methylpent-1-ene, 1-decene, 1-dodecene, 1-hexadecene, etc. Polyene comonomers can also be used herein, such as 1,3-hexadiene, 1,4-hexadiene, cyclopentadiene, dicyclopentadiene, 4-vinylcyclohex-1-ene, 1,5-cyclooctadiene, 5-vinylidene-2-norbornene and 5-vinyl-2-norbornene. However, when present, the amount of non-olefin monomers in the copolymer can be less than about 10mol.%, for example, less than about 5mol.%, for example, less than about 2.5mol.%, for example, less than about 1mol.%, wherein mol.% is based on the total moles of the monomers in the polymer.

[0024] In one embodiment, polyethylene can present bimodal molecular weight distribution. For example, bimodal distribution generally refers to that polymer has significantly higher molecular weight and significantly lower molecular weight (for example, two obvious peaks) on gel permeation chromatography curve. In another embodiment, polyethylene can present peaks exceeding two molecular weight distributions, for example polyethylene presents multimodal (for example, trimodal, tetramodal, etc.) distribution. Alternatively, polyethylene can present wide molecular weight distribution, wherein polyethylene is made up of blends of higher and lower molecular weight components, so that size exclusion chromatography or gel permeation chromatography curve does not show at least two obvious peaks but shows one obvious peak wider than single component peak.

[0025] In one embodiment, the composition can be composed of more than one polyethylene polymer, each having a different molecular weight and / or molecular weight distribution. For example, the molecular weight distribution can be within the average molecular weight specifications provided above.

[0026] In addition, the composition can be composed of a blend of one or more polyethylene polymers or copolymers and another thermoplastic polymer such as polypropylene or polybutylene. However, the non-polyethylene polymer in the composition can be less than about 10 wt.%, such as less than about 5 wt.%, such as less than about 2.5 wt.%, such as less than about 1 wt.%, wherein the wt.% is based on the total weight of the composition.

[0027] Any method known in the art can be used to synthesize polyethylene. High molecular weight polyethylene powder is usually produced by catalytic polymerization of ethylene monomer and optionally one or more other 1-olefin comonomers using a heterogeneous catalyst and an organic aluminum or magnesium compound as a cocatalyst, and the 1-olefin content in the final polymer is less than or equal to 10% of the ethylene content. Ethylene is usually polymerized in a gaseous phase or a slurry phase at relatively low temperatures and pressures. The polymerization reaction can be carried out at a temperature between 50°C and 100°C and a pressure in the range of 0.02 to 2MPa.

[0028] The molecular weight of polyethylene can be adjusted by adding hydrogen. Changes in temperature and / or the type and concentration of co-catalysts can also be used to fine-tune the molecular weight. In addition, the reaction can take place in the presence of an antistatic agent to avoid fouling the wall and contaminating the product.

[0029] Suitable catalyst systems include, but are not limited to, Ziegler-Natta catalysts. Typically, Ziegler-Natta catalysts are obtained by combining transition metal compounds of groups 4 to 8 of the periodic table with alkyl or hydrogenated derivatives of metals of groups 1 to 3 of the periodic table. Frequently used transition metal derivatives include metal halides or esters or combinations thereof. Exemplary Ziegler-Natta catalysts include catalysts based on the reaction products of organic aluminum or magnesium compounds (such as, but not limited to, alkyl aluminum or magnesium) and titanium, vanadium or chromium chlorides or esters. Heterogeneous catalysts may be unloaded or loaded onto porous fine-grained materials, such as silicon oxide or magnesium chloride. Such carriers may be added during the synthesis of the catalyst, or may be obtained as a chemical reaction product of the synthesis of the catalyst itself.

[0030] In one embodiment, a suitable catalyst system can be obtained by reacting a titanium (IV) compound with a trialkyl aluminum compound in an inert organic solvent at a temperature in the range of -40°C to 100°C, preferably -20°C to 50°C. The concentration of the starting materials is in the range of 0.1 to 9 mol / L, preferably 0.2 to 5 mol / L for the titanium (IV) compound, and in the range of 0.01 to 1 mol / L, preferably 0.02 to 0.2 mol / L for the trialkyl aluminum compound. The titanium component is added to the aluminum component over a period of 0.1 min to 60 min, preferably 1 min to 30 min, and the molar ratio of titanium to aluminum in the final mixture is in the range of 1:0.01 to 1:4.

[0031] In another embodiment, a suitable catalyst system is obtained by a one-step or two-step reaction of a titanium (IV) compound with a trialkyl aluminum compound in an inert organic solvent at a temperature in the range of -40°C to 200°C, preferably -20°C to 150°C. In the first step, the titanium (IV) compound is reacted with the trialkyl aluminum compound at a temperature in the range of -40°C to 100°C, preferably -20°C to 50°C, using a titanium to aluminum molar ratio in the range of 1:0.1 to 1:0.8. The concentration of the starting materials is in the range of 0.1 to 9.1 mol / L, preferably 5 to 9.1 mol / L for the titanium (IV) compound, and in the range of 0.05 to 1 mol / L, preferably 0.1 to 0.9 mol / L for the trialkyl aluminum compound. The titanium component is added to the aluminum compound over a period of 0.1 min to 800 min, preferably 30 min to 600 min. In the second step (if used), the reaction product obtained in the first step is treated with a trialkylaluminum compound at a temperature in the range of -10°C to 150°C, preferably 10°C to 130°C, using a titanium to aluminum molar ratio in the range of 1:0.01 to 1:5.

[0032] In yet another embodiment, a suitable catalyst system is obtained by a procedure in which, in a first reaction stage, magnesium alcoholate is reacted with titanium chloride in an inert hydrocarbon at a temperature of 50° C. to 100° C. In a second reaction stage, the reaction mixture formed is subjected to a thermal treatment at a temperature of 110° C. to 200° C. for a period of about 10 to 100 hours with the gradual formation of alkyl chlorides until no more alkyl chlorides are formed, and then the solids are separated from the soluble reaction products by washing several times with hydrocarbons.

[0033] In yet another embodiment, a catalyst supported on silica, such as the commercially available catalyst system Sylopol 5917, may also be used.

[0034] Using this catalyst system, polymerization is usually carried out continuously or batchwise in one or more steps at low pressure and temperature in suspension. The polymerization temperature is usually in the range of 30°C to 130°C, preferably in the range of 50°C to 90°C, and the partial pressure of ethylene is usually less than 10MPa, preferably, 0.05 and 5MPa. Trialkylaluminum, such as but not limited to isobutyl isopentyl aluminum (isoprenyl aluminum) and triisobutyl aluminum, is used as a cocatalyst so that the ratio of Al:Ti (cocatalyst: catalyst) is in the range of 0.01-100:1, more preferably, in the range of 0.03-50:1. The solvent is an inert organic solvent commonly used for the polymerization of Ziegler (Ziegler) type. Examples are butane, pentane, hexane, cyclohexene, octane, nonane, decane, their isomers and mixtures thereof. The molecular weight of the polymer is controlled by supplying hydrogen. The ratio of the hydrogen partial pressure to the ethylene partial pressure is in the range of 0 to 50, preferably in the range of 0 to 10. The polymer is separated and dried under nitrogen in a fluidized bed dryer. If a high boiling point solvent is used, the solvent can be removed by steam distillation. Salts of long chain fatty acids can be added as stabilizers. Common examples are calcium, magnesium and zinc stearates.

[0035] Alternatively, other catalysts may be used, such as Phillips catalysts, metallocenes and post-metallocenes. Cocatalysts such as alumoxane or alkylaluminum or alkylmagnesium compounds are also commonly used. For example, U.S. Patent Application Publication No. 2002 / 0040113 to Fritzsche et al. discusses several catalyst systems for producing high molecular weight polyethylene, the entire contents of which are incorporated herein by reference. Other suitable catalyst systems include Group 4 metal complexes of phenolate ether ligands, such as described in International Patent Publication No. WO2012 / 004675, the entire contents of which are incorporated herein by reference.

[0036] The polyethylene as used herein has an average molecular weight as determined according to ASTM D4020 testing of at least or greater than 100,000 g / mol, such as at least about 200,000 g / mol, such as at least about 300,000 g / mol, such as at least about 350,000 g / mol, such as at least about 450,000 g / mol, such as at least about 500,000 g / mol, such as at least about 600,000 g / mol, such as greater than about 1,000,000 g / mol, such as greater than about 1,500,000 g / mol, such as greater than about 2,000,000 g / mol, and typically less than about 5,000,000 g / mol, such as less than about 3,000,000 g / mol, such as less than about 1,000,000 g / mol. For example, the average molecular weight of the polymer can be greater than about 300,000 g / mol and less than about 5,000,000 g / mol, including all increments to 25,000 g / mol therebetween.

[0037] Polyethylene can be manufactured in the form of a powder, such as a micropowder. For example, the polyethylene powder can be a free-flowing powder. The polyethylene powder can have a multi-lobed (popcorn-like) morphology. The average particle size d50 of the powder can be no more than 2,000 μm, such as between about 10 μm and about 1,500 μm, such as about 50 μm to about 650 μm, such as about 50 to about 400 μm, such as about 50 to about 200 μm. Preferably, the synthetic polymer has a desired particle size. However, if the particle size of the synthetic polymer exceeds the desired value, the particles can be ground to the desired particle size. The particle size of the powder can be measured using a laser diffraction method according to ISO 13320.

[0038] The polyethylene may have a viscosity value of from at least 100 mL / g, such as at least 200 mL / g, such as at least 300 mL / g, such as at least 400 mL / g, such as at least 500 mL / g to less than about 2,000 mL / g, such as less than about 1,500 mL / g, such as less than about 1,000 mL / g, such as less than about 800 mL / g, such as less than about 600 mL / g, when measured according to ISO 1628, part 3, using a concentration of 0.0002 g / mL in decalin.

[0039] The amount of polyethylene present in the composition can be greater than about 70wt.%, such as greater than about 75wt.%, such as greater than about 80wt.%, such as greater than about 85wt.%, such as greater than about 90wt.%, such as greater than about 95wt.%, such as greater than about 98wt.%, and less than about 100wt.%, such as less than about 98wt.%, such as less than about 95wt.%. The above amount can be applicable to a single high molecular weight polyethylene polymer, or can be applicable to a blend of high molecular weight polyethylene polymers. However, in one embodiment, only a single high molecular weight polyethylene polymer is used to produce a polymer object.

[0040] As described above, the high molecular weight polyethylene polymer generally has a high purity. In this regard, the ash content of the high molecular weight polyethylene polymer can be less than about 500 ppm, such as less than about 250 ppm, such as less than about 100 ppm, such as less than about 50 ppm, such as less than about 10 ppm. When tested according to ISO 1183, the specific gravity of the high molecular weight polyethylene polymer can generally be greater than about 0.93 g / cm 3 , for example, greater than about 0.94 g / cm 3 , for example greater than about 0.95 g / cm 3 , and is usually less than about 0.97 g / cm 3 .

[0041] The polymer composition and the polymer articles produced therefrom may also contain other known additives, such as antioxidants, UV stabilizers, light stabilizers, heat stabilizers, reinforcing fibers or fillers, lubricants, brighteners, colorants, mold release agents, crosslinking agents, plasticizers, pigments, antistatic agents, etc. In one embodiment, any polymer additive present in the polymer is biocompatible.

[0042] In some embodiments, antioxidants slow down oxidation and / or chemical degradation of the polyethylene compositions described herein during storage, transport, and / or implementation (in vivo and / or in vitro). In some embodiments, examples of antioxidants suitable for use in conjunction with the polyethylene compositions described herein include, but are not limited to, ascorbic acid, glutathione, lipoic acid, uric acid, resveratrol, flavonoids, carotenes (e.g., beta-carotene), carotenoids, tocopherols (e.g., alpha-tocopherol), tocotrienols, panthenol, melatonin, secondary aromatic amines, benzofuranones, hindered phenols, polyphenols, hindered amines, organophosphorus compounds, thioesters, benzoates, lactones, hydroxylamines, and any combination thereof.

[0043] In some embodiments, reinforcing fillers can particularly enhance the mechanical strength of the polyethylene compositions described herein. In some embodiments, examples of reinforcing fillers suitable for use in conjunction with the polyethylene compositions described herein include, but are not limited to, glass spheres, glass fibers, bioglass, graphite, aluminum powder, talc, chalk, silicates, carbonates, calcium carbonate, alumina trihydrate, marble powder, cement powder, clay, feldspar, fumed silica, aluminum oxide, magnesium oxide, magnesium hydroxide, antimony oxide, zinc oxide, barium sulfate, aluminum silicate, calcium silicate, titanium dioxide, titanates, glass microspheres, carbon fibers, metal fibers, carbon nanotubes, wood flour, carbon black, etc., and any combination thereof.

[0044] In some embodiments, examples of pigments or dyes suitable for use in conjunction with the polyethylene compositions described herein include, but are not limited to, inorganic-based colorants, organic-based colorants, and the like, and any combination thereof.

[0045] In some embodiments, examples of antifouling agents suitable for use in combination with the polyethylene compositions described herein include, but are not limited to, sulfonamides, penicillins, cephalosporins, carbapenems, quinolones, oxazolidinones, quaternary ammonium compounds, precious metals (e.g., silver, gold, copper, etc.), amine-containing polymers, etc., and any combination thereof.

[0046] These additives can be used alone or in any combination thereof. Usually, unless otherwise stated, if an additive is used, the additive may be present in an amount of at least about 0.05wt.%, such as at least about 0.1wt.%, such as at least about 0.25wt.%, such as at least about 0.5wt.%, such as at least about 1wt.%, and usually less than about 20wt.%, such as less than about 10wt.%, such as less than about 5wt.%, such as less than about 4wt.%, such as less than about 2wt.%. The sum of the wt.% of all components including any additive (if present) used in the polymer composition will be 100wt.%.

[0047] In one embodiment, the polyethylene polymer composition may contain an active pharmaceutical ingredient and / or at least one developer. The active pharmaceutical ingredient may be surface coated onto the polymer object, or may be uniformly mixed with the polymer. Generally, any suitable active pharmaceutical ingredient may be included in the polymer object.

[0048] Imaging agents may also be included in the polymeric object, which interact with electromagnetic radiation so that the polymeric object can be better identified by X-ray or other imaging systems. In some embodiments, examples of imaging agents suitable for use in conjunction with the polyethylene compositions described herein include, but are not limited to, magnetic resonance imaging agents (e.g., barium sulfate, iron oxide particles, gadolinium compounds, erbium compounds, gadolinium endogenous fullerenes, gadolinium endogenous nanotubes), X-ray imaging agents (e.g., barium sulfate, iodine compounds, and iodine endogenous nanotubes), ultrasound imaging agents (e.g., perfluorocarbons and air bubbles), near infrared imaging agents (e.g., carbon nanotubes, gold nanoparticles, silver nanoparticles, and gold nanoshells), bismuth compounds, tungsten compounds, and the like, and any combination thereof. Typically, the imaging agent may be present in the polymeric composition in an amount of about 0.01 wt.% to about 5 wt.%.

[0049] The polymer compositions of the present disclosure can be used to produce many different types of medical products. For example, the polyethylene polymer compositions can be used to produce prosthetic devices, implants, and the like. The polymer compositions can also be used to produce medical instruments and various types of tubular devices, such as catheters, inhalers, and the like.

[0050] Examples of medical products that can be prepared according to the present disclosure include, but are not limited to, chips, RFID tags, tubes, pumps, feeding tubes, catheters, vascular catheters, prostheses, expandable balloons, stents, heart valves, neurostimulators, cochlear implants, craniomaxillofacial implants, artificial cartilage, gastric rings, surgical instruments, vascular clamps, aneurysm clips, spinal plugs used in conjunction with joint fusion systems, baseplates for use in artificial joints, muscle implants, nasopharyngeal implants, laryngeal implants, drug delivery devices, transdermal patches, subcutaneous implants, oral mucosal inlays, intrauterine devices, vaginal contraceptive rings, tooth fibers, hip implants, tibial implants, wrist implants, hand implants, portions thereof, and the like.

[0051] In some embodiments, the shaped polyethylene member of the present invention can be a pipe comprising at least one wall defining an interior volume, the at least one wall comprising the polyethylene composition described herein.

[0052] In some embodiments, the tubing-shaped polyethylene member can be designed to allow fluid to flow through the interior volume. For example, biomedical devices such as pumps, tubes, feeding tubes, catheters, vascular catheters, stents, heart valves, surgical instruments (e.g., surgical suction instruments), nasopharyngeal implants, and laryngeal implants can each include at least one tubing-shaped polyethylene member designed to allow fluid to flow through the interior volume.

[0053] In some embodiments, the tubing-formed polyethylene member may have at least one wire disposed within the interior volume. By way of non-limiting example, in some embodiments, a biomedical device (e.g., a pacemaker) may include at least one wire around which the tubing-formed polyethylene member is disposed.

[0054] In some embodiments, the molded polyethylene member described herein can be a major component of a biomedical device (e.g., craniomaxillofacial implant). In some examples, the polyethylene composition of the molded polyethylene member can include polyethylene and a bioabsorbable polymer, such that when implanted, the bioabsorbable polymer is absorbed, leaving voids in the polyethylene composition.

[0055] In certain embodiments, the polyethylene component of the molding of the present invention can substantially encase other components of biomedical equipment. In certain embodiments, the encasement can make when implanted in the patient, the surrounding tissue can be mainly exposed to the polyethylene component of molding. In certain embodiments, the encasement can be realized by carrying out overmolding (over molding), thermoforming or shrink wrapping around other components to be encased by the polyethylene composition described herein at least in part. In certain embodiments, the encasement can be realized by forming a polyethylene component of the molding that is suitable for placing biomedical equipment and / or its components therein in a size.

[0056] By way of non-limiting example, in some embodiments, a biomedical device (e.g., a cochlear implant or an RFID tag) may be substantially encased in a molded polyethylene member such that the molded polyethylene member resembles a coating disposed substantially around the biomedical device. By way of another non-limiting example, a biomedical device (e.g., a pacemaker or a neurostimulator) may include a molded polyethylene member including a wire having a coating disposed substantially around it, the coating comprising the polyethylene composition described herein. By way of another non-limiting example, a power source for a neurostimulator may include a molded polyethylene member substantially encasing the power source (e.g., by overmolding, thermoforming, or shrink wrapping).

[0057] In certain embodiments, the polyethylene component of molding described herein can be a drug delivery device or a part thereof.In certain embodiments, transdermal patch can include backing, drug-containing layer and release layer, wherein the polyethylene component of molding can be drug-containing layer and / or release layer.For non-limiting example, drug-containing layer can be the polyethylene component of molding, and release layer can include the second polymer (for example, ethylene copolymer such as ethylene vinyl acetate).In some examples, the polyethylene component of molding can include polyethylene and the second polymer.In some examples, drug-containing layer and release layer can be the polyethylene component of molding with different compositions independently.

[0058] Similar to the example of the transdermal patch, other drug delivery devices may include a molded polyethylene member. For example, a vaginal contraceptive ring has a core similar to the above drug-containing layer and a shell similar to the above release layer. In another example, a subcutaneous implant such as a rod or sheet having a multi-layer structure may have at least one layer similar to the drug-containing layer and at least one layer similar to the above release layer.

[0059] The high molecular weight polyethylene polymer compositions of the present disclosure can be formed into medical products using a variety of different techniques. However, the polymer compositions are particularly well suited for injection molding.

[0060] During melt forming, the polymer composition can be heated to a temperature of greater than about 100°C to about 300°C. In one embodiment, the polymer composition can be crosslinked after forming the polymer object. In one embodiment, for example, the polymer composition can contain a crosslinking agent in an amount of about 0.001 wt.% to about 1 wt.%. Crosslinking agents that can be used include, for example, peroxides or silanes. Electron beam crosslinking or gamma radiation can be used to crosslink the polymer.

[0061] The following examples demonstrate injection molding of polymer compositions according to the present disclosure.

[0062] Example

[0063] A high molecular weight polyethylene polymer was formulated according to the present disclosure. When tested at 190°C and with a load of 21.6 kg, the high molecular weight polyethylene polymer had a melt flow index of 1.1 g / 10 min. The polyethylene polymer had a viscosity value of 500 ml / g.

[0064] To demonstrate that a high molecular weight polymer can be injection molded, the polymer was formed into ISO tensile bars using injection molding.

[0065] During injection molding, the total shot weight was 25 grams. The injection molding apparatus was operated such that zone 1 was at 52° C., zone 2 was at 188° C., zone 3 was at 238° C., zone 4 was at 274° C., and the nozzle was at 260° C. The mold temperature was 70° C. The injection speed was 25 mm / s and the injection pressure was 686 bar.

[0066] During injection molding, the holding time was 12 seconds, the cooling time was 35 seconds, the screw rewind time was 15.7 seconds, the cycle time was 63 seconds, the screw speed was 225 rpm, and the back pressure was 69 bar.

[0067] ISO tensile test bars were successfully injection molded. The tensile stress of the tensile test bars was tested according to ISO 11542-2. The tensile stress of the tensile test bars was less than 0.05MPa.

[0068] Without departing from the spirit and scope of the present invention, those of ordinary skill in the art can skillfully make these and other changes to the present invention, the spirit and scope of the present invention are more specifically set forth in the appended claims. In addition, it should be understood that the various aspects of the various embodiments can be interchanged in whole or in part. In addition, those of ordinary skill in the art will recognize that the foregoing description is only by way of example and is not intended to limit the present invention, and therefore the present invention is further described in these appended claims.

Claims

1. A medical device comprising: An injection molded polymer article, the polymer article comprising a high molecular weight polyethylene polymer having a melt flow index greater than 0.8 g / 10 min and less than 2.5 g / 10 min when measured by ISO 1133 at 190° C. and with a load of 21.6 kg, and a viscosity value greater than 400 cm3 when measured according to ISO 1628-3. 3 / g and less than 900cm 3 / g, and wherein the high molecular weight polyethylene polymer contained in the polymer article is also a high density polyethylene polymer, and when measured according to method A of ISO 1183-1, the specific gravity of the high molecular weight polyethylene polymer is 0.94 g / cm 3 Up to 0.97g / cm 3 , and wherein the injection molded polymer article contains greater than 80 wt.% of the high molecular weight polyethylene polymer.

2. The medical device according to claim 1, wherein: The high molecular weight polyethylene polymer has a melt flow index of 0.9 g / 10 min to 2.0 g / 10 min.

3. The medical device according to claim 1 or 2, wherein: The viscosity of the high molecular weight polyethylene polymer is greater than 450 cm 3 / g and less than 900cm 3 / g.

4. The medical device according to claim 1 or 2, wherein: The high molecular weight polyethylene polymer has a molecular weight greater than 300,000 g / mol as tested according to ASTM D4020.

5. The medical device according to claim 4, wherein: The high molecular weight polyethylene polymer has a molecular weight of 350,000 g / mol to 5,000,000 g / mol as measured by ASTM D4020.

6. The medical device according to claim 1 or 2, wherein: When tested according to ISO 1183-1, method A, the specific gravity of the high molecular weight polyethylene polymer is 0.93 g / cm 3 Up to 0.97g / cm 3 .

7. The medical device according to claim 1 or 2, wherein: The high molecular weight polyethylene polymer meets the testing requirements of ISO10993 testing.

8. The medical device according to claim 7, wherein: The high molecular weight polyethylene polymer passed the ISO 10993-11 test for systemic toxicity, passed the ISO 10993-10 test for intradermal reactions, passed the ISO 10993-6 test for two-week muscle implantation, passed the ISO 10993-5 test for cytotoxicity, passed the ISO 10993-3 test for genotoxicity, passed the ISO 10993-4 test for hemolytic reactions, and passed the USP 661 test for physical chemistry.

9. The medical device according to claim 1 or 2, wherein: The injection molded polymer article contains the high molecular weight polyethylene polymer in an amount greater than 70 wt.%.

10. The medical device according to claim 1 or 2, wherein: The injection molded polymer article contains the high molecular weight polyethylene polymer in an amount greater than 90 wt.%.

11. The medical device according to claim 1 or 2, wherein: The high molecular weight polyethylene polymer comprises a copolymer of ethylene and at least one monomer comprising propylene, butene or a mixture thereof.

12. The medical device according to claim 1 or 2, wherein: The injection molded polymeric article also contains an active pharmaceutical ingredient.

13. The medical device according to claim 1 or 2, wherein: The polymeric object also includes an imaging agent.

14. The medical device according to claim 1 or 2, wherein: The polymeric article comprises a prosthetic device.

15. The medical device according to claim 1 or 2, wherein: The polymeric object comprises an implant.

16. The medical device according to claim 1 or 2, wherein: The polymer object has a tubular shape.

17. The medical device according to claim 1 or 2, wherein: The polymer object is incorporated into a chip, an RFID tag, a surgical instrument, a neurostimulator or a pump.

18. The medical device according to claim 1 or 2, wherein: The polymeric article includes a feeding tube, a catheter, an expandable balloon, a stent, a heart valve, a cochlear implant, a craniomaxillofacial implant, artificial cartilage, a gastric ring, a vascular clamp, an aneurysm clip, a spinal plug, a baseplate cap for an artificial joint, a muscle implant, a nasopharyngeal implant, a laryngeal implant, an oral mucosal inlay, an intrauterine device, a vaginal contraceptive ring, or a tooth fiber.

19. The medical device according to claim 1 or 2, wherein: The polymeric article includes a drug delivery device, a transdermal patch, or a subcutaneous implant.