Polyethylene microporous membrane and medical device

Abstract

A polyethylene microporous film is a film containing polyethylene, a seam holding strength (S MD ) in a machine direction (MD) of the aforementioned polyethylene microporous film is 1.5 N or more, a seam holding strength (S TD ) in a transverse direction (TD) of the aforementioned polyethylene microporous film is 1.5 N or more, a ratio (S TD / S MD ) of the aforementioned seam holding strength (S TD ) to the aforementioned seam holding strength (S MD ) is 0.8 to 1.2.

Description

Technical Field

[0001] This disclosure relates to polyethylene microporous membranes and medical devices. Background Technology

[0002] In the medical field, stretched polytetrafluoroethylene (PTFE) porous membranes are known to possess properties such as chemical stability, non-toxicity to organisms, non-degradability, and antithrombotic properties, making them ideally suited for direct contact with biological tissues. Furthermore, stretched PTFE porous membranes can flexibly adapt to the shapes of various biological tissues, thus serving as porous materials with sheet-like or tubular structures, used as patch materials, artificial blood vessels, catheters, and artificial cartilage replacement materials, among other medical polymer materials. For example, Patent Document 1 discloses a biaxially stretched PTFE porous membrane for implantation in biological tissues.

[0003] However, in recent years, with the implementation of European PFAS regulations, fluorinated substances containing at least one fully fluorinated methyl or methylene carbon atom (without bonded H / Cl / Br / I atoms) have become restricted. Although there is a grace period (13.5 years) for implantable medical devices (excluding mesh, wound care products, tubing, and catheters) and tubing and catheters for medical devices, it is hoped that alternative products will be replaced as soon as possible for those applying for approval.

[0004] Polyolefin porous membranes, particularly ultra-high molecular weight polyethylene (UHMWPE) porous membranes, can be used as components of medical devices for various life science applications, including biomedical uses (see, for example, Patent Document 2). Such polyethylene porous membranes possess permeability, mechanical strength and flexibility, biocompatibility, and biological stability, thus making them suitable components for use in medical applications involving contact with in vivo tissues or body fluids, such as vascular grafts, stent grafts, or catheter balloons.

[0005] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2005-314593 Patent Document 2: Japanese Patent No. 7343104 Summary of the Invention

[0006] The problem that the invention aims to solve In the field of implantable materials, when using sutures for suturing, high tear strength is required in all directions. Additionally, in patch materials, uniform physical properties of the membrane surface are essential.

[0007] Especially in biomedical or surgical applications, it is necessary to fix implanted materials in the body to designated locations or other components using metal clamps or sutures. The holes (pinholes) created by clamp fixation or sutures can become stress concentration points and / or small defects, which can promote or induce tearing and premature failure of porous membranes under mechanical loads. Therefore, improving the suture retention strength is crucial to overcome tearing and premature failure of porous membranes during use.

[0008] However, in the polyolefin porous membrane described in Patent Document 2, the pores within the membrane are partially filled by an elastomer. Although the strength of this filled area is high, sufficient strength is not achieved when stitching is performed at locations outside the filled area. Therefore, tearing and premature breakage can be promoted or induced from areas of low strength within the porous membrane, and sometimes it is not possible to adequately prevent liquid leakage from damaged parts or pinholes in the porous membrane.

[0009] Furthermore, the resin density differs between the elastomer filling location and other locations, thus the polyolefin porous membrane described in Patent Document 2 tends to exhibit anisotropic strength. Consequently, when cutting the polyolefin porous membrane described in Patent Document 2 into the desired shape, the ease of cutting is prone to unevenness, and it may not be considered a polyolefin porous membrane with excellent operability.

[0010] This disclosure is made in view of the above-mentioned existing conditions, and its purpose is to provide a polyethylene microporous membrane with excellent operability that can suppress fluid leakage at locations fixed by means such as suturing, and medical devices using the same.

[0011] Methods for solving problems The specific means to achieve the aforementioned goals are as follows.

[0012] <1> Polyethylene microporous membrane, which is a polyethylene microporous membrane containing polyethylene. The stitch retention strength (S) in the longitudinal direction (MD) of the aforementioned polyethylene microporous membrane MD The value is above 1.5N. The stitch retention strength (S) of the aforementioned polyethylene microporous membrane in the transverse (TD) direction TD The value is above 1.5N. The aforementioned suture retention strength (S) TD ) and the aforementioned suture retention strength (S MD The ratio of (S) TD / S MD The value ranges from 0.8 to 1.2.

[0013] <2> like <1> The polyethylene microporous membrane, wherein when the porosity of the aforementioned polyethylene microporous membrane is set as ε (%) and the membrane thickness of the aforementioned polyethylene microporous membrane is set as t (μm), the parameter A represented by the following formula (A) is greater than 60.

[0014] A = (2 - ε / 50) 1.5 ×t Equation (A) <3> like <1> or <2> The polyethylene microporous membrane wherein the proportion of ultra-high molecular weight polyethylene with a weight-average molecular weight of 3 million to 6 million in the aforementioned polyethylene is less than 50% by mass.

[0015] <4> like <1> ~ <3> The polyethylene microporous membrane according to any one of the following methods, wherein the porosity ε (%) of the aforementioned polyethylene microporous membrane is 35% to 90%.

[0016] <5> like <1> ~ <4> The polyethylene microporous membrane according to any one of the following methods, wherein the membrane thickness t (μm) of the aforementioned polyethylene microporous membrane is 40 μm to 300 μm.

[0017] <6> Medical devices, which include <1> ~ <5> The polyethylene microporous membrane described in any one of the following statements.

[0018] Invention Effects According to this disclosure, a polyethylene microporous membrane with excellent operability that can suppress liquid leakage at locations fixed by means such as suturing, and a medical device using the same, are available. Attached Figure Description

[0019] Figure 1 This is a diagram illustrating the method for measuring the suture retention strength in an embodiment. Detailed Implementation

[0020] The embodiments of this disclosure are described in detail below. However, this disclosure is not limited to the embodiments described below. In the embodiments described below, unless specifically stated otherwise, the constituent elements (including element steps, etc.) are not essential. Similarly, numerical values ​​and their ranges are not limited in this disclosure.

[0021] In this disclosure, the term "process" includes not only processes that are independent of other processes, but also processes that achieve their purpose, even if they cannot be clearly distinguished from other processes.

[0022] In this document, the numerical range indicated by “~” includes the minimum and maximum values ​​recorded before and after the “~”, respectively.

[0023] In the numerical ranges described in this disclosure, the upper or lower limit of one numerical range can be replaced with the upper or lower limit of another numerical range described in other stages. Furthermore, the upper or lower limit of a numerical range described in this disclosure can be replaced with the values ​​shown in the embodiments.

[0024] In this disclosure, each component may contain multiple corresponding substances. When multiple substances belonging to each component are present in the composition, unless otherwise specified, the content or percentage of each component refers to the total content or percentage of the multiple substances present in the composition.

[0025] In this disclosure, the terms “layer” or “membrane” include both cases where the layer or membrane is formed as a whole of the region in which it is observed, and cases where it is formed only in a part of the region.

[0026] In this publication, regarding polyethylene microporous membranes, "longitudinal" refers to the length direction of the polyethylene microporous membrane as it is manufactured into a strip shape, and "transverse" refers to the direction orthogonal to the length direction of the polyethylene microporous membrane. Hereinafter, "transverse" will also be referred to as "TD" and "longitudinal" as "MD".

[0027] In this disclosure, the “length” of a polyethylene microporous membrane refers to its length along the longitudinal direction. The “width” of a polyethylene microporous membrane refers to its length along the transverse direction.

[0028] <Polyethylene Microporous Membrane> The polyethylene microporous membrane disclosed herein is a membrane comprising polyethylene, wherein the stitch retention strength (S) in the longitudinal direction (MD) of the aforementioned polyethylene microporous membrane is... MD The strength of the stitch retention in the transverse (TD) direction of the aforementioned polyethylene microporous membrane is above 1.5N (S). TD ) 1.5N or above, the aforementioned suture retention strength (S) TD ) and the aforementioned suture retention strength (S MD The ratio of (S) TD / S MD The value ranges from 0.8 to 1.2.

[0029] The polyethylene microporous membrane disclosed herein exhibits excellent operability and can suppress liquid leakage at locations fixed by means such as stitching. The reason for this is not yet clear, but is speculated as follows.

[0030] The longitudinal (MD) stitch retention strength (S) of the polyethylene microporous membrane disclosed herein. MD ) and suture retention strength in the transverse (TD) direction (S) TDAll of these components have a strength of 1.5N or higher, exhibiting high strength and thus exhibiting a tendency to resist damage to the porous membrane or tearing from pinholes. Therefore, they tend to easily suppress liquid leakage at locations secured by means such as sewing.

[0031] On the other hand, the polyethylene microporous membrane of this disclosure has a ratio (S) TD / S MD The strength ranges from 0.8 to 1.2, indicating isotropic strength. Therefore, when cutting polyethylene microporous membranes into the desired shape, the cutting ease is not prone to unevenness and the operability is excellent.

[0032] Based on the above, it can be inferred that the polyethylene microporous membrane disclosed herein has excellent operability and can suppress liquid leakage at locations that are fixed by means such as stitching.

[0033] Polyethylene microporous membranes are microporous membranes composed of polyethylene. Here, a microporous membrane refers to a structure with a large number of interconnected micropores inside, which means that gas or liquid can pass through from one side to the other.

[0034] The following provides a detailed description of the resin, physical properties, etc., of the polyethylene microporous membrane that constitutes this disclosure.

[0035] (Sutures maintain strength) In this disclosure, the stitch retention strength (S) along the longitudinal direction (MD) of the polyethylene microporous membrane is... MD Set to 1.5N or higher. MD The value is preferably 1.6N or higher, more preferably 1.7N or higher, and even more preferably 1.8N or higher. MD The value can be below 5.0N.

[0036] In this disclosure, the stitch retention strength (S) in the transverse (TD) direction of the polyethylene microporous membrane is... TD Set to 1.5N or higher. TD The value is preferably 1.6N or higher, more preferably 1.7N or higher, and even more preferably 1.8N or higher. TD The value can be below 5.0N.

[0037] By making S MD Value and S TD The values ​​are all above 1.5N, which makes it easy to suppress the tearing and early damage of polyethylene microporous membranes from stress-concentrated parts and / or small defects.

[0038] It should be noted that the stitch retention strength of the polyethylene microporous membrane was determined using the method described in Example 1.

[0039] In this disclosure, the stitch retention strength (S) of the polyethylene microporous membrane is specified. TD ) and suture retention strength (S) MD The ratio of (S) TD / S MD The value is set to 0.8 to 1.2, preferably 0.85 to 1.15, and more preferably 0.9 to 1.1.

[0040] If compared to (S) TD / S MD If the strength is in the range of 0.8 to 1.2, the polyethylene microporous membrane exhibits isotropic strength, and there is a tendency to improve the operability of the polyethylene microporous membrane.

[0041] It should be noted that the ratio (S) of polyethylene microporous membranes TD / S MD ) is achieved by using S MD Value and S TD The value is obtained by calculating the ratio of the two.

[0042] (Porosity) In this disclosure, the porosity of the polyethylene microporous membrane is preferably 35% to 90%. If the porosity of the polyethylene microporous membrane is 35% or more, there is a tendency for surrounding tissue to invade into the porous structure and become integrated, thereby forming a good healing state. The porosity of the polyethylene microporous membrane is preferably 35% or more, more preferably 40% or more, and even more preferably 45% or more. On the other hand, if the porosity of the polyethylene microporous membrane is 90% or less, there is a tendency to obtain a tissue barrier effect that can prevent the invasion and adhesion of surrounding tissue. The porosity of the polyethylene microporous membrane is preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less.

[0043] In this disclosure, the porosity of the polyethylene microporous membrane is a value obtained by the method described in the Example 1 section.

[0044] (film thickness) The thickness of the polyethylene microporous membrane disclosed herein is preferably 40 μm to 300 μm. If the thickness of the polyethylene microporous membrane is 40 μm or more, there is a tendency to improve operability. The thickness of the polyethylene microporous membrane disclosed herein is preferably 40 μm or more, more preferably 50 μm or more, and even more preferably 60 μm or more. On the other hand, if the thickness of the polyethylene microporous membrane is 300 μm or less, there is a tendency to improve flexibility. The thickness of the polyethylene microporous membrane is more preferably 290 μm or less, and even more preferably 280 μm or less.

[0045] It should be noted that the thickness of the polyethylene microporous membrane was determined using the method described in the Example 1 section.

[0046] (Parameter A) Regarding the polyethylene microporous membrane of this disclosure, when the porosity of the polyethylene microporous membrane is set as ε (%) and the membrane thickness is set as t (μm), from the viewpoint of minimizing damage during use, parameter A, expressed in the following formula (A), is preferably greater than 60, more preferably 62 or more, and even more preferably 65 or more. From the viewpoint of balancing invasiveness and softness into the porous structure from the surrounding tissue, parameter A can be 120 or less, preferably 100 or less, and more preferably 90 or less. Parameter A is preferably greater than 60 and less than 120.

[0047] A = (2 - ε / 50) 1.5 ×t Equation (A) Here, ε in Equation (A) represents the porosity of the polyethylene microporous membrane. When the porosity of the polyethylene microporous membrane is, for example, 60%, ε is taken as 60. In addition, t in Equation (A) represents the membrane thickness of the polyethylene microporous membrane. When the membrane thickness of the polyethylene microporous membrane is, for example, 100 μm, t is taken as 100.

[0048] (Aperture) In this disclosure, the pore size of the polyethylene microporous membrane is preferably 0.01 μm to 5 μm. If the pore size of the polyethylene microporous membrane is 0.01 μm or more, there is a tendency for increased invasiveness of surrounding tissue into the porous structure. The pore size of the polyethylene microporous membrane is preferably 0.02 μm or more, more preferably 0.04 μm or more, and even more preferably 0.05 μm or more. On the other hand, if the pore size of the polyethylene microporous membrane is 5 μm or less, there is a tendency to obtain a tissue barrier effect that can prevent the invasion and adhesion of surrounding tissue. The pore size of the polyethylene microporous membrane is preferably 3 μm, more preferably 2 μm or less, and even more preferably 1.5 μm or less.

[0049] In this disclosure, the pore size of the polyethylene microporous membrane is a value obtained by the method described in the Example 1 section.

[0050] (Puncture strength) From the viewpoint of suppressing leakage, the puncture strength of the polyethylene microporous membrane of this disclosure is preferably 400 gf or more, more preferably 450 gf or more, and even more preferably 500 gf or more. From the viewpoint of suture needle operability, the puncture strength of the polyethylene microporous membrane of this disclosure can be 1000 gf or less. The puncture strength of the polyethylene microporous membrane of this disclosure is preferably 400 gf to 1000 gf.

[0051] In this disclosure, the puncture strength of the polyethylene microporous membrane is a value obtained by the method described in the Example 1 section.

[0052] (Breathability) From the viewpoint of suppressing leakage, the air permeability (Gurley value) of the polyethylene microporous membrane of this disclosure is preferably 10 seconds / 100 mL or more, more preferably 50 seconds / 100 mL or more, and even more preferably 100 seconds / 100 mL or more. From the viewpoint of air permeability, the air permeability of the polyethylene microporous membrane of this disclosure can be 500 seconds / 100 mL or less. The air permeability of the polyethylene microporous membrane of this disclosure is preferably 10 seconds / 100 mL to 500 seconds / 100 mL.

[0053] In this disclosure, the air permeability of the polyethylene microporous membrane is a value obtained by the method described in the Example 1 section.

[0054] (Components of polyethylene microporous membrane) The polyethylene microporous membrane disclosed herein is a membrane containing polyethylene.

[0055] The polyethylene microporous membrane disclosed herein may be formed of polyethylene alone, or it may be formed of polyethylene and materials other than polyethylene.

[0056] In the resin component constituting the polyethylene microporous membrane, the content of polyethylene is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, particularly preferably 90% by mass or more, and most preferably 99% by mass or more.

[0057] The polyethylene microporous membrane may contain only one type of polyethylene, or it may contain two or more types with different molecular weights.

[0058] When a polyethylene microporous membrane contains resin components other than polyethylene, examples of such resin components include polypropylene, polybutene, polymethylpentene, or copolymers thereof.

[0059] Polyethylene microporous membranes can also contain ultra-high molecular weight polyethylene (UHMWPE) as polyethylene. If a polyethylene microporous membrane contains UHMWPE, there is a tendency for the pore size of the polyethylene microporous membrane to be not too large while maintaining excellent strength.

[0060] When the polyethylene microporous membrane contains ultra-high molecular weight polyethylene (UHMWPE), the proportion of UHMWPE in the resin component constituting the polyethylene microporous membrane is preferably 50% by mass or less. If the proportion of UHMWPE in the resin component constituting the polyethylene microporous membrane is 50% by mass or less, there is a tendency for the pore size of the polyethylene microporous membrane to be not too small, resulting in excellent permeability. The proportion of UHMWPE in the resin component constituting the polyethylene microporous membrane is preferably 48% by mass or less, more preferably 45% by mass or less.

[0061] Furthermore, when the polyethylene microporous membrane includes ultra-high molecular weight polyethylene (UHMWPE), the proportion of UHMWPE in the resin component (polyethylene) constituting the polyethylene microporous membrane is preferably 1% by mass or more. If the proportion of UHMWPE in the resin component constituting the polyethylene microporous membrane is 1% by mass or more, the mechanical strength of the polyethylene microporous membrane is easily improved. More preferably, the proportion of UHMWPE in the resin component constituting the polyethylene microporous membrane is 3% by mass or more, and even more preferably 5% by mass or more.

[0062] When the polyethylene microporous membrane contains ultra-high molecular weight polyethylene, the proportion of ultra-high molecular weight polyethylene in the resin component that constitutes the polyethylene microporous membrane, i.e., polyethylene, is preferably 1% to 50% by mass.

[0063] When a polyethylene microporous membrane comprises ultra-high molecular weight polyethylene and polyolefins other than ultra-high molecular weight polyethylene (hereinafter also referred to as other polyolefins) as polyethylene, the type of other polyolefins is not particularly limited. High-density polyethylene (HDPE) is preferred as an other polyolefin. In this disclosure, high-density polyethylene refers to polyethylene with a density of 942 kg / m³. 3 The above refers to polyethylene.

[0064] In this publication, ultra-high molecular weight polyethylene refers to polyethylene with a weight-average molecular weight of 3 million to 6 million.

[0065] The weight-average molecular weight of ultra-high molecular weight polyethylene is preferably 3.5 million or more, and more preferably 4 million or more. Furthermore, the weight-average molecular weight of ultra-high molecular weight polyethylene is preferably 5 million or less, and more preferably 4.8 million or less.

[0066] In this disclosure, the weight-average molecular weight of polyethylene can be determined using gel permeation chromatography.

[0067] Specifically, the following method can be used: Polyethylene, the analyte, is dissolved in o-dichlorobenzene by heating, and the solution is determined using gel permeation chromatography (system: Waters Alliance GPC 2000, column: GMH6-HT and GMH6-HTL) at a column temperature of 135°C and a flow rate of 1.0 mL / min. Molecular weight is corrected using monodisperse polystyrene (TOSOH).

[0068] In addition to resin components, polyethylene microporous membranes may also contain additives such as organic fillers, inorganic fillers, and surfactants as needed, without affecting the effectiveness of this disclosure.

[0069] In one or more isolated regions on the surface of the polyethylene microporous membrane of this disclosure, the pores within the polyethylene microporous membrane may be at least partially filled with an elastomer.

[0070] Examples of elastomers that at least partially fill pores include polymers selected from the group consisting of polyesters, polyamides, polystyrene, polyacrylates, polyurethanes, polyolefins, polyethers, and polysiloxanes (or organosilicones) or combinations thereof.

[0071] (Applications of polyethylene microporous membranes) There are no particular limitations on the applications of polyethylene microporous membranes. Specifically, they can be used as materials for medical devices described later. Other applications of polyethylene microporous membranes include air filters, liquid filters, breathable and waterproof membranes, bags, dust collection sheet substrates, and reinforcing materials for ion exchange membranes.

[0072] <Method for manufacturing polyethylene microporous membranes> Polyethylene microporous membranes can be manufactured, for example, by a manufacturing method including the following steps (I) to (IV).

[0073] Process (I): The process of preparing a solution containing polyethylene and a solvent.

[0074] Step (II): The aforementioned solution is melt-mixed, the resulting melt-mixed material is extruded from the mold, and cooled and solidified to obtain the first gel-like molded product.

[0075] Step (III): The process of stretching the first gel-shaped molded article in at least one direction (single stretching) and drying it with solvent to obtain the second gel-shaped molded article.

[0076] Step (IV): The step of stretching the aforementioned second gel-like molded article in at least one direction (secondary stretching).

[0077] Process (I) is the process of preparing a solution containing polyethylene and a solvent, as well as other components to be used as needed.

[0078] As a solvent, a non-volatile solvent with a boiling point above 210°C at atmospheric pressure or a volatile solvent with a boiling point below 210°C at atmospheric pressure can be used.

[0079] Examples of solvents used for solution preparation include non-volatile solvents such as liquid paraffin, paraffin oil, mineral oil, and castor oil; and volatile solvents such as tetrahydronaphthalene, ethylene glycol, decahydronaphthalene, toluene, xylene, diethyltriamine, ethylenediamine, dimethyl sulfoxide, and hexane, with liquid paraffin, decahydronaphthalene, or xylene being particularly preferred. One volatile solvent may be used alone, or two or more may be used in combination. Among these, decahydronaphthalene and xylene are preferred volatile solvents.

[0080] The polyethylene used in process (I) can be of only one type or two or more types, and the selection can be made according to the desired physical properties of the polyethylene microporous membrane. In addition, other resin components besides polyethylene and the aforementioned additives can be cited as other components.

[0081] Regarding the solution prepared in step (I), from the viewpoint of controlling the porous structure of the polyethylene microporous membrane, the polyolefin concentration is preferably 10% to 35% by mass, more preferably 12% to 34% by mass, and even more preferably 15% to 32% by mass. If the polyolefin concentration in the solution is 10% by mass or more, breakage can be suppressed during the manufacturing process of the polyethylene microporous membrane. In addition, the mechanical strength of the polyethylene microporous membrane is increased, and its operability is improved. If the polyolefin concentration in the solution is 35% by mass or less, the polyethylene microporous membrane of this disclosure can be easily obtained.

[0082] Step (II) is the following step: the solution prepared in step (I) is melt-blended, the resulting melt-blended compound is extruded from a mold, and cooled and solidified to obtain a first gel-like molded article. In step (II), for example, an extrudate is obtained by extrusion from a mold within a temperature range from the melting point of polyethylene to +65°C, and then the extrudate is cooled to obtain the first gel-like molded article. The first gel-like molded article is preferably shaped into a sheet. There are no particular limitations on the cooling method. For example, cooling can be performed by immersion in water or an organic solvent, contact with a cooled metal roller, etc.

[0083] Step (III) involves stretching the first gel-like molded article in at least one direction (single stretching) and drying it with solvent to obtain the second gel-like molded article. The stretching step in step (III) can be either uniaxial stretching or biaxial stretching. Biaxial stretching can be sequential biaxial stretching with separate longitudinal and transverse stretching, or simultaneous biaxial stretching with both longitudinal and transverse stretching. From the viewpoint of controlling the porous structure of the polyethylene microporous membrane, the stretching ratio (the product of the longitudinal stretching ratio and the transverse stretching ratio) of the single stretching is preferably 1.1 to 4 times, more preferably 1.1 to 3.5 times. The stretching temperature during the single stretching is preferably below 120°C.

[0084] The drying of the solvent in step (III) (drying step) is preferably carried out at a temperature at which the second gel-shaped molded article will not deform, and more preferably at a temperature below 80°C.

[0085] The stretching and drying processes in step (III) can be performed simultaneously or in stages. For example, pre-drying can be performed while stretching is being done, followed by formal drying, or stretching can be performed between pre-drying and formal drying. The stretching can also be performed while controlling the drying process so that the solvent remains in a suitable state.

[0086] Step (IV) is a step of stretching (secondary stretching) the second gel-like molded article in at least one direction. The stretching step (IV) can be uniaxial stretching or biaxial stretching. Biaxial stretching can be any of the following: sequential biaxial stretching in which longitudinal stretching and transverse stretching are performed separately; simultaneous biaxial stretching in which longitudinal stretching and transverse stretching are performed at the same time; a step of stretching in the longitudinal direction multiple times followed by stretching in the transverse direction; a step of stretching in the longitudinal direction and stretching in the transverse direction multiple times; a step of performing sequential biaxial stretching followed by stretching in the longitudinal direction and / or transverse direction once or more.

[0087] From the viewpoint of controlling the porous structure of the polyethylene microporous membrane, the stretching ratio (the product of the longitudinal stretching ratio and the transverse stretching ratio) of the secondary stretching is preferably 4 to 30 times. From the viewpoint of controlling the porous structure of the polyethylene microporous membrane, the stretching temperature of the secondary stretching is preferably 70°C to 135°C, and more preferably 80°C to 130°C.

[0088] If necessary, heat-fixing treatment can also be performed after step (IV). From the viewpoint of controlling the porous structure of the polyethylene microporous membrane, the temperature of heat-fixing treatment is preferably 110°C to 150°C, and more preferably 120°C to 140°C.

[0089] If necessary, solvent extraction and annealing can be performed after heat-fixing. Solvent extraction can be performed, for example, by immersing the heat-fixed sheet in a dichloromethane bath to dissolve the residual solvent into the dichloromethane. Preferably, the dichloromethane is removed by drying after lifting the polyethylene microporous membrane from the dichloromethane bath. Annealing can be performed after solvent extraction by conveying the polyethylene microporous membrane on rollers heated to, for example, 70°C to 140°C, or by conveying the polyethylene microporous membrane in a heated atmosphere at 70°C to 140°C while maintaining a constant dimension in the width direction.

[0090] <Medical Devices> The medical devices disclosed herein include the polyethylene microporous membrane of this disclosure.

[0091] The polyethylene microporous membrane disclosed herein has excellent operability and can suppress fluid leakage at locations fixed by means of suturing, making it suitable as a patch material for use in repairing the pericardium, pleura, diaphragm, peritoneum, tendon sheath, etc.

[0092] Furthermore, the polyethylene microporous membrane disclosed herein, through secondary processing, can also be used as a vascular device such as a vascular graft, occlusion device, stent cover or catheter balloon, or artificial cartilage substitute material for temporary or permanent use in the body.

[0093] In addition, it can also be used as a material for medical implants, especially for orthopedic implants used in orthopedic surgery related to the musculoskeletal system.

[0094] The medical device disclosed herein is suitable for use with the aforementioned various biological implant materials.

[0095] Example The following describes embodiments and comparative examples of this disclosure, but this disclosure is not limited to these embodiments in any way.

[0096] [Determination Method] The methods for determining the physical properties of the polyethylene microporous membranes of the Examples and Comparative Examples are described below. The results are shown in Table 1.

[0097] (Aperture) For the pore size of the polyethylene microporous membrane, a PMI fine pore size distribution measuring instrument (model: CFP-1200-AEXL) was used, with PMI Galwick (surface tension 15.9 dyn / cm) as the immersion solution, and the pore size was determined using the semi-dry method specified in ASTM E1294-89. The measurement temperature was set to 25°C, and the measurement pressure was varied within the range of 0 kPa to 600 kPa.

[0098] (film thickness) The thickness of the polyethylene microporous membrane was measured using a contact-type thickness gauge (Mitutoyo, ABS digital display gauge, Model ID: ID-S112X). Specifically, 10 points were taken equally along the width of the polyethylene microporous membrane for measurement, and 10 points were taken at other locations in the same manner. The arithmetic mean of the 20 points was taken as the membrane thickness. Cylindrical terminals with a bottom diameter of 6.5 mm were used as contact terminals.

[0099] (Porosity) The porosity (ε) of the polyethylene microporous membrane is calculated using the following formula.

[0100] ε(%)={1-Ws / (ds·t)}×100 Ws: Weight per unit area of ​​polyethylene microporous membrane (g / m³) 2 ) ds: True density of polyethylene (g / cm³) 3 ) t: Thickness of the polyethylene microporous membrane (μm) It should be noted that the weight per unit area of ​​the polyethylene microporous membrane is calculated by cutting the sample into 10cm×10cm pieces, measuring its mass, and then dividing the mass by the area.

[0101] In addition, the true density of polyethylene is expressed as 0.96 g / cm³. 3 .

[0102] (Parameter A (A value)) Based on the membrane thickness and porosity of the polyethylene microporous membrane measured as described above, the parameter A represented by equation (A) is calculated.

[0103] (Breathability (Gurley value)) The Gurley value of the polyethylene microporous membrane was determined according to JIS P8117:2009 using a Gurley permeability meter from Toyo Seiki Co., Ltd. For the measurement, the permeability of 200 ml of air through 28.6 mm was measured. The time for the sample is calculated by halving that time and converting it per 100 ml.

[0104] (Puncture strength) A puncture test was conducted using a KATO TECH KES-G5 handheld compression tester with a needle tip curvature radius of 0.5 mm and a puncture speed of 2 mm / sec. The maximum puncture load was taken as the puncture strength. The sample, along with a silicone gasket, was clamped and fixed to a metal frame (sample holder) with a Φ11.3 mm hole.

[0105] On the TD direction of the polyethylene microporous membrane, two points 10 mm away from both ends and eight points at equal intervals between the two points are taken for measurement, and the arithmetic mean of these measurements is used to calculate the result.

[0106] (Maintaining the strength of the sutures) The method for determining the retention strength of sutures is explained based on the attached figures.

[0107] The suture retention strength was determined using a small benchtop testing machine, Shimadzu Corporation, EZ-SX (model: QC-005-02). Figure 1As shown in (a), the test pieces were cut to 10mm × 50mm. Five test pieces were prepared along the longitudinal direction (MD) of the polyethylene microporous membrane, and five test pieces were prepared along the transverse direction (TD) of the polyethylene microporous membrane. Figure 1 As shown in (b), marks are made using a ballpoint pen or felt-tip pen at a position 2 mm from one end of the test piece and at a position 30 mm from that position. When perforating the marked portion at the 2 mm mark, care should be taken to avoid enlarging the needle hole due to the load from the needle during perforation. For example, the needle curvature can be adjusted to ensure the needle is always perpendicular to the membrane when making the perforation on the foamed urethane plate. A 5-0 surgical polypropylene monofilament suture (PROLENE 5-0 M8321) is passed through the marked portion at the 2 mm mark. Figure 1 As shown in (c), the suture length is set to be at least 15 cm after folding it back. The test piece is clamped in such a way that the marked suture is aligned with the lower tension clamp, ensuring the test piece is vertically positioned as confirmed from the side. The suture is connected to the suture clamp holder fixed by the tension test clamp, and the suture is clamped so that the test piece and the suture are in a straight line. Five measurements are performed at a test speed of 50 mm / min, and the average value of the maximum point test force (N) is calculated as the suture holding strength. The value obtained from the test piece cut along the longitudinal (MD) direction of the polyethylene microporous membrane is taken as S. MD The value, obtained by cutting a test piece along the longitudinal (TD) direction of the polyethylene microporous membrane, is used as S. TD value.

[0108] Then, from the obtained S MD Value and S TD Calculate the ratio (S) TD / S MD ).

[0109] [Example 1] Using 12 parts by weight of ultra-high molecular weight polyethylene (UHMWPE) with a weight average molecular weight (Mw) of 4.6 million and a weight average molecular weight (Mw) of 560,000 with a density of 950 kg / m³ 3 A polyethylene composition was obtained by mixing 18 parts by weight of high-density polyethylene (HDPE). A polyethylene solution was prepared by mixing 70 parts by weight of liquid paraffin with the total polyethylene resin concentration of 30% by weight.

[0110] The polyethylene solution is extruded from the mold in sheet form at a temperature of 181°C. The extrudate is then cooled in a water bath at 15°C, and a water flow is provided on the surface of the water bath to prevent the mixed solvent released from the gelled sheet in the water bath and floating on the water surface from re-adhering to the sheet, thereby producing a gelled sheet (base tape).

[0111] The gel-like sheet was pre-dried at 55°C for 22 minutes. Then, it was stretched once along the MD direction at 100°C and 2.3 times the normal strength. Next, it was stretched a second time along the TD direction at 115°C and 5.1 times the normal strength. Immediately after the second stretching, it was heat-treated at 128°C (heat setting).

[0112] The heat-fixed sheet was continuously immersed in a dichloromethane bath divided into three sections for a total of 12 minutes to extract the solvent. After being removed from the dichloromethane bath, the sheet was dried on heated rollers at 39°C to remove the dichloromethane. Then, the sheet was annealed in a heating atmosphere at 120°C.

[0113] The above process yields a polyethylene microporous membrane.

[0114] [Example 2] Prepare 15 parts by weight of ultra-high molecular weight polyethylene (UHMWPE) with a weight-average molecular weight (Mw) of 4.6 million and 560,000 parts by weight of polyethylene with a density of 950 kg / m³. 3 A polyethylene composition was obtained by mixing 85 parts by mass of high-density polyethylene (HDPE). Next, a polyethylene solution was prepared by mixing the polyethylene composition with decahydronaphthalene as a solvent, so that the concentration of the polyethylene composition was 30% by mass.

[0115] The polyethylene solution was extruded from the mold in sheet form at a temperature of 160°C, and then the extrudate was cooled in a water bath at a temperature of 20°C to obtain a first gel-like sheet.

[0116] The first gel-like sheet was pre-dried at 60°C for 15 minutes, then stretched once along the MD direction at 100°C and 1.25 times the original length, followed by formal drying at 55°C for 10 minutes to obtain the second gel-like sheet. The residual solvent content in the second gel-like sheet was kept less than 1% by mass.

[0117] Next, as a secondary stretching, the second gel-like sheet was stretched along the MD direction at a temperature of 80°C at a ratio of 1.9, and then stretched along the TD direction at a temperature of 125°C at a ratio of 4.4. Immediately after the secondary stretching, it was subjected to heat treatment (heat setting) at 130°C.

[0118] The heat-fixed sheet was continuously immersed in a dichloromethane bath for a total of 1 minute to extract the solvent. After being removed from the dichloromethane bath, the sheet was dried on a heated roller at 40°C to remove the dichloromethane. Then, the sheet was annealed in a heating atmosphere at 80°C.

[0119] The above process yields a polyethylene microporous membrane.

[0120] [Example 3] Using 3.4 parts by weight of ultra-high molecular weight polyethylene (UHMWPE) with a weight average molecular weight (Mw) of 4.6 million and a weight average molecular weight (Mw) of 560,000 with a density of 950 kg / m³ 3 A polyethylene composition was obtained by mixing 13.6 parts by weight of high-density polyethylene (HDPE). A polyethylene solution was prepared by mixing 51 parts by weight of liquid paraffin and 32 parts by weight of decahydronaphthalene in such a way that the total concentration of polyethylene resin was 17% by weight.

[0121] The polyethylene solution was extruded from the mold in sheet form at a temperature of 157°C, and then the extrudate was cooled in a water bath at 15°C to obtain a first gel-like sheet.

[0122] The first gel-like sheet was pre-dried at 70°C for 10.5 minutes. Then, it was stretched once along the MD direction at 100°C and 3.0 times the normal strength. Next, it was stretched a second time along the TD direction at 110°C and 4.0 times the normal strength. Immediately after the second stretching, it was heat-treated at 133°C (heat setting).

[0123] The heat-fixed sheet was continuously immersed in a dichloromethane bath divided into three sections for a total of 12 minutes to extract the solvent. After being removed from the dichloromethane bath, the sheet was dried on heated rollers at 39°C to remove the dichloromethane. Then, the sheet was annealed in a heating atmosphere at 120°C.

[0124] The above process yields a polyethylene microporous membrane.

[0125] [Comparative Example 1] Prepare 15 parts by weight of ultra-high molecular weight polyethylene (UHMWPE) with a weight-average molecular weight (Mw) of 4.6 million and 560,000 parts by weight of polyethylene with a density of 950 kg / m³. 3 A polyethylene composition was obtained by mixing 85 parts by mass of high-density polyethylene (HDPE). Next, a polyethylene solution was prepared by mixing the polyethylene composition with decahydronaphthalene as a solvent, so that the concentration of the polyethylene composition was 30% by mass.

[0126] The polyethylene solution was extruded from the mold in sheet form at a temperature of 159°C, and then the extrudate was cooled in a water bath at a temperature of 20°C to obtain the first gel-like sheet.

[0127] The first gel-like sheet was pre-dried at 60°C for 10 minutes, then stretched once along the MD direction by 1.3 times, and finally dried at 55°C for 7 minutes to obtain the second gel-like sheet. The residual solvent content in the second gel-like sheet was made less than 1% by mass.

[0128] Next, as a secondary stretching, the second gel-like sheet was stretched along the MD direction at a temperature of 80°C at a ratio of 2.5, and then stretched along the TD direction at a temperature of 125°C at a ratio of 6.0. Immediately after the secondary stretching, it was subjected to heat treatment (heat setting) at 134°C.

[0129] The heat-fixed sheet was continuously immersed in a dichloromethane bath for a total of 1 minute to extract the solvent. After being removed from the dichloromethane bath, the sheet was dried on a heated roller at 40°C to remove the dichloromethane. Then, the sheet was annealed in a heating atmosphere at 80°C.

[0130] The above process yields a polyethylene microporous membrane.

[0131] [Comparative Example 2] Prepare 15 parts by weight of ultra-high molecular weight polyethylene (UHMWPE) with a weight-average molecular weight (Mw) of 4.6 million and 560,000 parts by weight of polyethylene with a density of 950 kg / m³. 3 A polyethylene composition was obtained by mixing 85 parts by mass of high-density polyethylene (HDPE). Next, a polyethylene solution was prepared by mixing the polyethylene composition with decahydronaphthalene as a solvent, so that the concentration of the polyethylene composition was 30% by mass.

[0132] The polyethylene solution was extruded from the mold in sheet form at a temperature of 160°C, and then the extrudate was cooled in a water bath at a temperature of 20°C to obtain a first gel-like sheet.

[0133] The first gel-like sheet was pre-dried at 60°C for 15 minutes, then stretched once along the MD direction by 1.3 times, and finally dried at 55°C for 10 minutes to obtain the second gel-like sheet. The residual solvent content in the second gel-like sheet was made less than 1% by mass.

[0134] Next, as a secondary stretching, the second gel-like sheet was stretched along the MD direction at a temperature of 80°C at a ratio of 2.0, and then stretched along the TD direction at a temperature of 125°C at a ratio of 4.7. Immediately after the secondary stretching, it was subjected to heat treatment (heat setting) at 130°C.

[0135] The heat-fixed sheet was continuously immersed in a dichloromethane bath for a total of 1 minute to extract the solvent. After being removed from the dichloromethane bath, the sheet was dried on a heated roller at 40°C to remove the dichloromethane. Then, the sheet was annealed in a heating atmosphere at 80°C.

[0136] The above process yields a polyethylene microporous membrane.

[0137] [evaluate] The polyethylene microporous membranes obtained as described above were evaluated as follows. The results are shown in Table 1.

[0138] (Operability) Using surgical scissors (manufactured by Songji Medical Instruments) (medical device registration number: 11B3X00081000017), the polyethylene microporous membrane was trimmed into a circle with a radius of 3 cm. The ease of trimming was evaluated based on the following criteria.

[0139] -Benchmark- 1. Easy to cut and easy to operate 2. It can be cut, but it will lag. 3. Difficult to cut (Liquid leakage) A polyethylene microporous membrane was cut into 200mm × 200mm pieces. Five stitches were sewn in the center of the membrane using polypropylene monofilament suture (PROLENE 5-0M8321) to create a test piece for testing liquid leakage through pinholes. The water resistance of this test piece was determined according to JIS L 1092:2009 Method A (low water pressure method). A rating of A was given for water resistance greater than 150mm, and a rating of B was given for water resistance less than 150mm.

[0140] [Table 1] According to the evaluation results in Table 1, the polyethylene microporous membrane of the embodiment has superior operability and can suppress liquid leakage at locations that are fixed by means such as sewing compared to the polyethylene microporous membrane of the comparative example.

[0141] The full disclosure of Japanese Patent Application No. 2024-055062, filed on March 28, 2024, is incorporated herein by reference.

[0142] All documents, patent applications and technical standards described in this specification are incorporated herein by reference to the extent that each document, patent application and technical standard is incorporated by reference to the extent that it is specifically and separately described.

Claims

1. A polyethylene microporous membrane, which is a polyethylene microporous membrane containing polyethylene, wherein, The stitch retention strength (S) along the longitudinal direction (MD) of the polyethylene microporous membrane MD The value is above 1.5N. The transverse (TD) stitch retention strength (S) of the polyethylene microporous membrane TD The value is above 1.5N. The suture retention strength (S) TD ) and the suture retention strength (S) MD The ratio of (S) TD / S MD The value ranges from 0.8 to 1.

2.

2. The polyethylene microporous membrane as described in claim 1, wherein, When the porosity of the polyethylene microporous membrane is set as ε (%) and the membrane thickness is set as t (μm), the parameter A represented by the following formula (A) is greater than 60. A=(2-ε / 50) 1.5 ×t Formula (A).

3. The polyethylene microporous membrane as described in claim 1, wherein, Ultra-high molecular weight polyethylene with a weight-average molecular weight of 3 million to 6 million accounts for less than 50% by mass of the total polyethylene.

4. The polyethylene microporous membrane as described in claim 1, wherein, The porosity ε (%) of the polyethylene microporous membrane is 35% to 90%.

5. The polyethylene microporous membrane as described in claim 1, wherein, The thickness t (μm) of the polyethylene microporous membrane is 40μm to 300μm.

6. A medical device comprising a polyethylene microporous membrane according to any one of claims 1 to 5.

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