Polyethylene microporous film and medical device

Abstract

A polyethylene microporous film according to the present invention contains polyethylene. The suture retention strength (SMD) in the vertical direction (MD) of the polyethylene microporous film is at least 1.5 N, the suture retention strength (STD) in the horizontal direction (TD) of the polyethylene microporous film is at least 1.5 N, and the ratio (STD / SMD) of the suture retention strength (STD) to the suture retention strength (SMD) is 0.8–1.2.

Description

Polyethylene microporous membrane and medical device

[0001] The present disclosure relates to polyethylene microporous membranes and medical devices.

[0002] In the medical field, expanded polytetrafluoroethylene (PTFE) porous membranes are known as the ideal material for applications in direct contact with biological tissues due to their properties such as chemical stability, non-toxicity to living organisms, non-degradability, and antithrombogenicity. Furthermore, expanded PTFE porous membranes can flexibly change their shape to fit various biological tissue shapes, and are therefore used as porous bodies having sheet or tubular structures as medical polymer materials for patch materials, artificial blood vessels, catheters, artificial cartilage replacement materials, and the like. For example, Patent Document 1 discloses a biaxially expanded PTFE porous membrane used as a biological implant material.

[0003] In recent years, the European PFAS regulation has restricted "fluorinated substances containing at least one fully fluorinated methyl or methylene carbon atom (with no H / Cl / Br / I atoms bonded)." Implantable medical devices (excluding meshes, wound care products, tubes, and catheters) and medical device tubes and catheters are subject to reporting, although there is a grace period (13.5 years), and early replacement with alternative products is desirable.

[0004] Porous polyolefin membranes, particularly ultra-high molecular weight polyethylene (UHMWPE) porous membranes, can be used in various life science applications, including biomedical applications, as components of medical devices (see, for example, Patent Document 2). Such porous polyethylene membranes have permeability, mechanical strength and flexibility, biocompatibility, and biological stability, and therefore can also be suitable components for use in medical applications that come into contact with body tissues or fluids, such as in vascular applications such as vascular grafts, stent covers, or catheter balloons.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2005-314593 Patent Document 2: Japanese Patent No. 7343104

[0006] In the field of bioimplants, high tear strength against sutures is required in all directions when sewn with sutures. Furthermore, uniform physical properties across the membrane surface are required for patch materials. Particularly in biomedical or surgical applications, bioimplants must be fixed in place or to another component by means such as metal clamps or stitching. Holes (pinholes) resulting from clamping or sutures can become stress concentrations and / or small defects that can promote or induce tearing and premature failure of porous membranes under mechanical load. To overcome tearing and premature failure of porous membranes during use, it is crucial to improve suture retention strength. However, in the polyolefin porous membrane described in Patent Document 2, the pores within the film are partially filled with an elastomer, and although the filled areas have high strength, sufficient strength cannot be obtained when suturing at areas other than the filled areas. Therefore, tearing and premature breakage may be promoted or induced from areas of the porous membrane where strength is low, and liquid leakage from damaged areas or pinholes in the porous membrane may not be sufficiently prevented. Furthermore, because the resin density differs between the elastomer-filled areas and areas other than the filled areas, the polyolefin porous membrane described in Patent Document 2 tends to exhibit anisotropic strength. Therefore, the polyolefin porous membrane described in Patent Document 2 is prone to unevenness in ease of cutting when cut into a desired shape, and is not necessarily a polyolefin porous membrane with excellent workability. The present disclosure has been made in consideration of the above-mentioned conventional circumstances, and aims to provide a polyethylene microporous membrane that is easy to work with and suppresses liquid leakage at areas fixed by means such as suturing, and a medical device using the same.

[0007] Specific means for achieving the above object are as follows: <1> A polyethylene microporous membrane containing polyethylene, wherein the polyethylene microporous membrane has a suture retention strength (S ＭＤ ) is 1.5 N or more, and the suture retention strength (S ＴＤ ) is 1.5N or more, and the suture retention strength (SＴＤ ) the suture retention strength (S ＭＤ ) to the ratio (S ＴＤ / S ＭＤ <2> The polyethylene microporous membrane according to <1>, wherein a parameter A represented by the following formula (A) exceeds 60, where ε (%) is the porosity of the polyethylene microporous membrane and t (μm) is the thickness of the polyethylene microporous membrane: A=(2-ε / 50): １．５ ×t Formula (A) <3> The polyethylene microporous membrane according to <1> or <2>, wherein the ultrahigh molecular weight polyethylene having a weight-average molecular weight of 3,000,000 to 6,000,000 accounts for 50 mass% or less of the polyethylene. <4> The polyethylene microporous membrane according to any one of <1> to <3>, wherein the polyethylene microporous membrane has a porosity ε (%) of 35% to 90%. <5> The polyethylene microporous membrane according to any one of <1> to <4>, wherein the polyethylene microporous membrane has a thickness t (μm) of 40 μm to 300 μm. <6> A medical device comprising the polyethylene microporous membrane according to any one of <1> to <5>.

[0008] According to the present disclosure, it is possible to provide a polyethylene microporous membrane that is easy to work with and that suppresses liquid leakage at sites fixed by means such as suturing, and a medical device using the same.

[0009] FIG. 10 is a diagram for explaining a method for measuring the suture retention strength in the examples.

[0010] Hereinafter, embodiments of the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments. In the following embodiments, components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit the present disclosure.

[0011] In the present disclosure, the term "process" includes not only processes that are independent of other processes, but also processes that cannot be clearly distinguished from other processes as long as the purpose of the process is achieved. In the present disclosure, numerical ranges indicated using "to" include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in the present disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another staged numerical range. Furthermore, in numerical ranges described in the present disclosure, the upper or lower limit of that numerical range may be replaced with a value shown in the Examples. In the present disclosure, each component may contain multiple corresponding substances. When multiple substances corresponding to each component are present in a composition, the content or amount of each component refers to the total content or amount of the multiple substances present in the composition, unless otherwise specified. In the present disclosure, the terms "layer" and "film" include cases where the layer or film is formed over the entire region when the region in which the layer or film is present is observed, as well as cases where the layer or film is formed only over a portion of the region.

[0012] In this disclosure, with respect to a polyethylene microporous membrane, "longitudinal direction" refers to the longitudinal direction of a polyethylene microporous membrane produced in a long shape, and "transverse direction" refers to the direction perpendicular to the longitudinal direction of the polyethylene microporous membrane. Hereinafter, the "transverse direction" is also referred to as "TD," and the "longitudinal direction" is also referred to as "MD." In this disclosure, the "length" of a polyethylene microporous membrane refers to the length of the polyethylene microporous membrane in the longitudinal direction. The "width" of a polyethylene microporous membrane refers to the length of the polyethylene microporous membrane in the width direction.

[0013] <Polyethylene microporous membrane> The polyethylene microporous membrane of the present disclosure contains polyethylene, and the suture retention strength (S ＭＤ ) is 1.5 N or more, and the suture retention strength in the transverse direction (TD) of the polyethylene microporous membrane is (S ＴＤ ) 1.5N or more, and the suture retention strength (S ＴＤ ) the suture retention strength (S ＭＤ ) to the ratio (S ＴＤ / SＭＤ ) is 0.8 to 1.2. The polyethylene microporous membrane of the present disclosure has excellent workability and suppresses liquid leakage at locations fixed by means such as sewing. The reason for this is not clear, but is presumed to be as follows. The polyethylene microporous membrane of the present disclosure has a suture retention strength (S ＭＤ ) and suture retention strength in the transverse direction (TD) (S ＴＤ ) are both 1.5 N or more, which is a high strength, and therefore the porous membrane tends to be less susceptible to breakage or tearing from pinholes. Therefore, leakage of liquid at the site fixed by means such as sewing tends to be more easily suppressed. On the other hand, the polyethylene microporous membrane of the present disclosure has a ratio (S ＴＤ / S ＭＤ ) is 0.8 to 1.2, exhibiting isotropic strength, the polyethylene microporous membrane is less prone to unevenness in ease of cutting into a desired shape and tends to have excellent workability. From the above, it is presumed that the polyethylene microporous membrane of the present disclosure has excellent workability and suppresses liquid leakage at sites fixed by means such as sewing.

[0014] A polyethylene microporous membrane is a microporous membrane containing polyethylene. Here, the microporous membrane refers to a membrane having numerous micropores inside, which are interconnected, allowing gas or liquid to pass from one surface to the other.

[0015] The resins constituting the polyethylene microporous membrane of the present disclosure, its physical properties, and the like will be described in detail below.

[0016] (Suture Retention Strength) In the present disclosure, the suture retention strength (S ＭＤ ) is set to 1.5N or more. ＭＤ The value is preferably 1.6 N or more, more preferably 1.7 N or more, and even more preferably 1.8 N or more. ＭＤ In the present disclosure, the suture retention strength (S) of the polyethylene microporous membrane in the transverse direction (TD) may be 5.0 N or less. ＴＤ ) is set to 1.5N or more. ＴＤThe value is preferably 1.6 N or more, more preferably 1.7 N or more, and even more preferably 1.8 N or more. ＴＤ The value may be 5.0 N or less. ＭＤ value and S ＴＤ When both values ​​are 1.5 N or more, tearing and premature breakage from parts of the polyethylene microporous membrane subjected to stress concentration and / or small defects tends to be suppressed. The suture retention strength of the polyethylene microporous membrane refers to a value determined by the method described in the Examples section.

[0017] In the present disclosure, the suture retention strength (S ＴＤ ) suture retention strength (S ＭＤ ) to the ratio (S ＴＤ / S ＭＤ The ratio (S) is set to 0.8 to 1.2, preferably 0.85 to 1.15, and more preferably 0.9 to 1.1. ＴＤ / S ＭＤ When the ratio (S ) of the polyethylene microporous membrane is in the range of 0.8 to 1.2, the polyethylene microporous membrane exhibits isotropic strength, and the workability of the polyethylene microporous membrane tends to be improved. ＴＤ / S ＭＤ ) is S ＭＤ value and S ＴＤ This refers to the value obtained by calculating the ratio between the two values.

[0018] (Porosity) In the present disclosure, the porosity of the polyethylene microporous membrane is preferably 35% to 90%. When the porosity of the polyethylene microporous membrane is 35% or more, surrounding tissue tends to infiltrate and become integrated into the porous structure, resulting in a tendency for a good healing state to be achieved. 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, when the porosity of the polyethylene microporous membrane is 90% or less, a tissue blocking effect that makes it possible to prevent the infiltration and adhesion of surrounding tissue tends to be obtained. The porosity of the polyethylene microporous membrane is preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less. In the present disclosure, the porosity of the polyethylene microporous membrane refers to the value determined by the method described in the Examples section.

[0019] (Thickness) The thickness of the polyethylene microporous membrane of the present disclosure is preferably 40 μm to 300 μm. When the thickness of the polyethylene microporous membrane is 40 μm or more, handleability tends to be improved. The thickness of the polyethylene microporous membrane of the present disclosure is preferably 40 μm or more, more preferably 50 μm or more, and even more preferably 60 μm or more. On the other hand, when the thickness of the polyethylene microporous membrane is 300 μm or less, flexibility tends to be improved. The thickness of the polyethylene microporous membrane is more preferably 290 μm or less, and even more preferably 280 μm or less. The thickness of the polyethylene microporous membrane refers to the value determined by the method described in the Examples section.

[0020] (Parameter A) In the polyethylene microporous membrane of the present disclosure, where ε (%) is the porosity of the polyethylene microporous membrane and t (μm) is the thickness of the polyethylene microporous membrane, from the viewpoint of resistance to breakage during use, parameter A represented by the following formula (A) is preferably more than 60, more preferably 62 or more, and even more preferably 65 or more. From the viewpoint of a balance between flexibility and ability to penetrate into the porous structure of surrounding tissue, parameter A may be 120 or less, preferably 100 or less, and more preferably 90 or less. Parameter A is preferably more than 60 and 120 or less.

[0021] A = (2 - ε / 50) １．５ ×t Formula (A) Here, ε in Formula (A) represents the porosity of the polyethylene microporous membrane, and when the porosity of the polyethylene microporous membrane is, for example, 60%, ε takes a value of 60. Furthermore, t in Formula (A) represents the membrane thickness of the polyethylene microporous membrane, and when the membrane thickness of the polyethylene microporous membrane is, for example, 100 μm, t takes a value of 100.

[0022] (Pore size) In the present disclosure, the pore size of the polyethylene microporous membrane is preferably 0.01 μm to 5 μm. A polyethylene microporous membrane with a pore size of 0.01 μm or more tends to improve penetration 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, a polyethylene microporous membrane with a pore size of 5 μm or less tends to provide a tissue blocking effect that makes it possible to prevent penetration 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. In the present disclosure, the pore size of the polyethylene microporous membrane refers to a value determined by the method described in the Examples section.

[0023] (Pin puncture strength) The pin puncture strength of the polyethylene microporous membrane of the present 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 leakage suppression. The pin puncture strength of the polyethylene microporous membrane of the present disclosure may be 1000 gf or less, from the viewpoint of suture needle operability. The pin puncture strength of the polyethylene microporous membrane of the present disclosure is preferably 400 gf to 1000 gf. In the present disclosure, the pin puncture strength of the polyethylene microporous membrane refers to a value determined by the method described in the Examples section.

[0024] (Air permeability) The air permeability (Gurley value) of the polyethylene microporous membrane of the present disclosure is preferably 10 sec / 100 mL or more, more preferably 50 sec / 100 mL or more, and even more preferably 100 sec / 100 mL or more, from the viewpoint of leakage suppression. The air permeability of the polyethylene microporous membrane of the present disclosure may be 500 sec / 100 mL or less, from the viewpoint of breathability. The air permeability of the polyethylene microporous membrane of the present disclosure is preferably 10 sec / 100 mL to 500 sec / 100 mL. In the present disclosure, the air permeability of the polyethylene microporous membrane refers to a value determined by the method described in the Examples section.

[0025] (Constituent components of polyethylene microporous membrane) The polyethylene microporous membrane of the present disclosure contains polyethylene. The polyethylene microporous membrane of the present disclosure may be composed of only polyethylene, or may be composed of polyethylene and a material other than polyethylene. Of the resin components constituting the polyethylene microporous membrane, the polyethylene content is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and extremely preferably 99% by mass or more. The polyethylene microporous membrane may contain only one type of polyethylene, or two or more types with different molecular weights, etc.

[0026] When the polyethylene microporous membrane contains a resin component other than polyethylene, examples of the other resin component include polypropylene, polybutylene, polymethylpentene, and copolymers thereof.

[0027] The polyethylene microporous membrane may contain ultra-high molecular weight polyethylene (UHMWPE) as the polyethylene. When the polyethylene microporous membrane contains ultra-high molecular weight polyethylene, the pore size of the polyethylene microporous membrane tends to be not too large and the strength tends to be excellent.

[0028] When the polyethylene microporous membrane contains ultra-high molecular weight polyethylene, the proportion of ultra-high molecular weight polyethylene in the polyethylene that is the resin component constituting the polyethylene microporous membrane is preferably 50% by mass or less. When the proportion of ultra-high molecular weight polyethylene in the resin component constituting the polyethylene microporous membrane is 50% by mass or less, the pore size of the polyethylene microporous membrane tends to be not too small and the permeability performance tends to be excellent. The proportion of ultra-high molecular weight polyethylene in the resin component constituting the polyethylene microporous membrane is preferably 48% by mass or less, more preferably 45% by mass or less. Furthermore, when the polyethylene microporous membrane contains ultra-high molecular weight polyethylene, the proportion of ultra-high molecular weight polyethylene in the polyethylene that is the resin component constituting the polyethylene microporous membrane is preferably 1% by mass or more. When the proportion of ultra-high molecular weight polyethylene 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 increased. The proportion of ultra-high molecular weight polyethylene in the resin component constituting the polyethylene microporous membrane is more preferably 3% by mass or more, even more preferably 5% by mass or more. When the polyethylene microporous membrane contains ultra-high molecular weight polyethylene, the proportion of the ultra-high molecular weight polyethylene in the polyethylene that is the resin component constituting the polyethylene microporous membrane is preferably 1% by mass to 50% by mass.

[0029] When the polyethylene microporous membrane contains ultra-high molecular weight polyethylene and a polyolefin other than ultra-high molecular weight polyethylene (hereinafter also referred to as other polyolefin) as polyethylene, the type of the other polyolefin is not particularly limited. As the other polyolefin, high-density polyethylene (HDPE) is preferred. In the present disclosure, high-density polyethylene refers to polyethylene having a density of 942 kg / m ３ The above polyethylene refers to polyethylene of the above type.

[0030] In the present disclosure, ultra-high molecular weight polyethylene refers to polyethylene having a weight-average molecular weight of 3 million to 6 million. The weight-average molecular weight of the ultra-high molecular weight polyethylene is preferably 3.5 million or more, and more preferably 4 million or more. The weight-average molecular weight of the ultra-high molecular weight polyethylene is preferably 5 million or less, and more preferably 4.8 million or less.

[0031] In the present disclosure, the weight-average molecular weight of polyethylene is measured by gel permeation chromatography. Specifically, the polyethylene to be measured is heated and dissolved in o-dichlorobenzene, and measurement is performed using gel permeation chromatography (system: Alliance GPC 2000 manufactured by Waters Corporation, columns: GMH6-HT and GMH6-HTL) at a column temperature of 135°C and a flow rate of 1.0 mL / min. Monodisperse polystyrene (manufactured by Tosoh Corporation) is used to calibrate the molecular weight.

[0032] The polyethylene microporous membrane may contain additives such as organic fillers, inorganic fillers, and surfactants as materials other than the resin component, as needed, to the extent that the effects of the present disclosure are not affected.

[0033] In one or more discrete regions on the surface of the polyethylene microporous membrane of the present disclosure, the pores in the polyethylene microporous membrane may be at least partially filled with an elastomer, such as a polymer selected from the group consisting of polyester, polyamide, polystyrene, polyacrylate, polyurethane, polyolefin, polyether, and polysiloxane (or silicone), or a combination thereof.

[0034] (Uses of polyethylene microporous membrane) The uses of the polyethylene microporous membrane are not particularly limited. Specific uses include use as a material for constituting the medical devices described below. Further uses of the polyethylene microporous membrane include air filters, liquid filters, moisture-permeable waterproof membranes, bags, dust-collecting sheet substrates, and reinforcing materials for ion-exchange membranes.

[0035] <Method for producing polyethylene microporous membrane> The polyethylene microporous membrane can be produced, for example, by a production method including the following steps (I) to (IV).

[0036] Step (I): A step of preparing a solution containing polyethylene and a solvent. Step (II): A step of melt-kneading the solution, extruding the resulting melt-kneaded product through a die, and cooling and solidifying it to obtain a first gel-like molded product. Step (III): A step of stretching the first gel-like molded product in at least one direction (primary stretching) and drying the solvent to obtain a second gel-like molded product. Step (IV): A step of stretching the second gel-like molded product in at least one direction (secondary stretching).

[0037] Step (I) is a step of preparing a solution containing polyethylene and a solvent, and further containing other components as needed. The solvent can be a non-volatile solvent having a boiling point of 210°C or higher at atmospheric pressure, or a volatile solvent having a boiling point of less than 210°C at atmospheric pressure. Examples of solvents used in preparing the solution include non-volatile solvents such as liquid paraffin, paraffin oil, mineral oil, and castor oil, and volatile solvents such as tetralin, ethylene glycol, decalin, toluene, xylene, diethyltriamine, ethylenediamine, dimethyl sulfoxide, and hexane, with liquid paraffin, decalin, and xylene being particularly preferred. The volatile solvent may be used alone or in combination of two or more. Among these, decalin and xylene are preferred.

[0038] The polyethylene used in step (I) may be one type or two or more types, and can be selected depending on the desired physical properties of the polyethylene microporous membrane, etc. Other components include resins other than polyethylene, the above-mentioned additives, etc.

[0039] From the viewpoint of controlling the porous structure of the polyethylene microporous membrane, the solution prepared in step (I) preferably has a polyolefin concentration of 10% to 35% by mass, more preferably 12% to 34% by mass, and even more preferably 15% to 32% by mass. A polyolefin concentration of 10% by mass or more in the solution can suppress the occurrence of breakage in the polyethylene microporous membrane production process, and also increases the mechanical strength of the polyethylene microporous membrane, improving handleability. A polyolefin concentration of 35% by mass or less in the solution makes it easier to obtain the polyethylene microporous membrane of the present disclosure.

[0040] Step (II) is a step of melt-kneading the solution prepared in step (I), extruding the resulting melt-kneaded mixture through a die, and solidifying it by cooling to obtain a first gel-like molded product. In step (II), for example, extrusion through a die is performed at a temperature range from the melting point of polyethylene to the melting point + 65°C to obtain an extrudate, which is then cooled to obtain a first gel-like molded product. The first gel-like molded product is preferably shaped into a sheet. The cooling method is not particularly limited. For example, cooling may be performed by immersion in water or an organic solvent, contact with a cooled metal roll, or the like.

[0041] Step (III) is a step of stretching the first gel-like molded product in at least one direction (primary stretching) and drying the solvent to obtain a second gel-like molded product. The stretching step in step (III) may be either uniaxial stretching or biaxial stretching. Biaxial stretching may be sequential biaxial stretching in which longitudinal stretching and transverse stretching are performed separately, or simultaneous biaxial stretching in which longitudinal stretching and transverse stretching are performed simultaneously. From the viewpoint of controlling the porous structure of the polyethylene microporous membrane, the stretching ratio in the primary stretching (the product of the longitudinal stretching ratio and the transverse stretching ratio) is preferably 1.1 to 4 parts, more preferably 1.1 to 3.5 parts. The temperature during primary stretching is preferably 120°C or lower. Drying of the solvent in step (III) (drying step) is preferably performed at a temperature at which the second gel-like molded product does not deform, more preferably 80°C or lower.

[0042] The stretching step and the drying step in step (III) may be carried out simultaneously or stepwise. For example, the first stretching may be carried out while pre-drying and then main drying, or the first stretching may be carried out between pre-drying and main drying. The first stretching may also be carried out in a state where the drying is controlled and the solvent remains in a suitable state.

[0043] Step (IV) is a step of stretching the second gel-like molded product in at least one direction (secondary stretching). The stretching step in step (IV) may be uniaxial stretching or biaxial stretching. The biaxial stretching may 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 simultaneously; a step of stretching in the longitudinal direction multiple times and then stretching in the transverse direction; a step of stretching in the longitudinal direction and then stretching in the transverse direction multiple times; or a step of sequential biaxial stretching and then further stretching in the longitudinal and / or transverse directions once or multiple times.

[0044] From the viewpoint of controlling the porous structure of the polyethylene microporous membrane, the stretching ratio in the second stretching (the product of the longitudinal stretching ratio and the transverse stretching ratio) is preferably 4 to 30. From the viewpoint of controlling the porous structure of the polyethylene microporous membrane, the stretching temperature in the second stretching is preferably 70°C to 135°C, more preferably 80°C to 130°C.

[0045] If necessary, heat setting may be performed after step (IV). The heat setting temperature is preferably 110°C to 150°C, more preferably 120°C to 140°C, from the viewpoint of controlling the porous structure of the polyethylene microporous membrane.

[0046] If necessary, the heat setting may be followed by an extraction treatment of the solvent remaining in the polyethylene microporous membrane and an annealing treatment. The extraction treatment of the residual solvent is carried out, for example, by immersing the heat-set sheet in a methylene chloride bath to dissolve the residual solvent in the methylene chloride. After the polyethylene microporous membrane immersed in the methylene chloride bath is removed from the methylene chloride bath, the methylene chloride is preferably removed by drying. The annealing treatment can be carried out after the extraction treatment of the residual solvent by transporting the polyethylene microporous membrane over rollers heated to, for example, 70°C to 140°C, or by transporting the polyethylene microporous membrane in a heated atmosphere at 70°C to 140°C while maintaining a constant width dimension.

[0047] <Medical Device> A medical device of the present disclosure includes the polyethylene microporous membrane of the present disclosure. The polyethylene microporous membrane of the present disclosure is easy to work with and inhibits fluid leakage at sites fixed by means such as sutures, making it suitable as a patch material used to repair the pericardium, pleura, diaphragm, peritoneum, tendon sheath, and the like. Furthermore, the polyethylene microporous membrane of the present disclosure can be subjected to secondary processing and used as medical devices for temporary or permanent use in the body, such as vascular devices such as vascular grafts, occlusion devices, stent covers, and catheter balloons, and artificial cartilage replacement materials. Furthermore, it can be used as a material for medical implants, particularly orthopedic implants used in orthopedic surgery related to the musculoskeletal system. The medical device of the present disclosure can be suitable for use as the various bioimplant materials described above.

[0048] Examples and comparative examples of the present disclosure will be described below, but the present disclosure is not limited to these examples in any way.

[0049] [Measurement methods] The methods for measuring the physical properties of the polyethylene microporous membranes of Examples and Comparative Examples are described below. The results are shown in Table 1.

[0050] (Pore diameter) The pore diameter of the polyethylene microporous membrane was determined by the half-dry method specified in ASTM E1294-89 using a Perm Porometer (model: CFP-1200-AEXL) manufactured by PMI and Galwick (surface tension 15.9 dyn / cm) manufactured by PMI as the immersion liquid. The measurement temperature was 25°C, and the measurement pressure was changed in the range from 0 kPa to 600 kPa.

[0051] (Film Thickness) The film thickness of the polyethylene microporous membrane was measured using a contact film thickness meter (Mitutoyo Corporation, ABS Digimatic Indicator, Model ID: ID-S112X). Specifically, the polyethylene microporous membrane was measured at 10 uniformly spaced points across the width, and then at 10 different locations, and the arithmetic average of the 20 points in total was determined as the film thickness. A cylindrical terminal with a bottom diameter of 6.5 mm was used as the contact terminal.

[0052] (Porosity) The porosity (ε) of the polyethylene microporous membrane was calculated by the following formula: ε (%) = {1 - Ws / (ds·t)} × 100, where Ws is the basis weight (g / m) of the polyethylene microporous membrane. ２ ) ds: true density of polyethylene (g / cm ３ t: film thickness (μm) of the polyethylene microporous membrane. The basis weight of the polyethylene microporous membrane was determined by cutting a 10 cm × 10 cm sample, measuring the mass, and dividing the mass by the area. The true density of polyethylene is 0.96 g / cm ３ The value of was used.

[0053] (Parameter A (A value)) Parameter A represented by formula (A) was calculated based on the thickness and porosity of the polyethylene microporous membrane measured as described above.

[0054] (Air permeability (Gurley value)) The Gurley value of the polyethylene microporous membrane was measured using a Gurley densometer manufactured by Toyo Seiki Seisaku-sho, Ltd., in accordance with JIS P8117: 2009. The time required for 200 mL of air to pass through a 28.6 mmφ sample was measured, and this time was halved to obtain a value per 100 mL.

[0055] (Puncture Strength) A puncture test was performed using a KES-G5 handy compression tester manufactured by Kato Tech Co., Ltd., under conditions of a needle tip curvature radius of 0.5 mm and a puncture speed of 2 mm / sec, and the maximum puncture load was taken as the puncture strength. Here, the sample was clamped and fixed in a metal frame (sample holder) with a Φ11.3 mm hole, together with a silicone rubber packing. Measurements were taken at a total of 10 points in the TD direction of the polyethylene microporous membrane, including two points 10 mm from both ends and eight points equally spaced between the two points, and the puncture strength was calculated by arithmetic averaging.

[0056] (Suture Retention Strength) The method for measuring suture retention strength will be described with reference to the drawings. Suture retention strength was measured using a small benchtop testing machine EZ-SX (model: QC-005-02) manufactured by Shimadzu Corporation. Test specimens were cut to 10 mm x 50 mm as shown in Figure 1(a). Five test specimens were prepared with their longitudinal direction aligned with the machine direction (MD) of the polyethylene microporous membrane, and five with their longitudinal direction aligned with the transverse direction (TD) of the polyethylene microporous membrane. Marks were made with a ballpoint pen or a felt-tip pen at positions 2 mm from one end of the test specimen and 30 mm from that position, as shown in Figure 1(b). Perforation of the marked portion 2 mm from the marked position can be performed by taking care not to widen the pinhole due to the load from the needle during perforation. For example, holes can be made on a urethane foam plate so that the needle always pierces the film perpendicularly, following the curvature of the needle. A surgical polypropylene monofilament suture (Prolene 5-0 M8321) with a thread thickness of 5-0 was threaded through the marked 2 mm position. The length of the suture was adjusted to 15 cm or more by folding the suture back as shown in Figure 1 (c). The test specimen was clamped so that the marked line was aligned with the lower tensile jig, and the test specimen was set vertically while checking from the side. The suture was connected to the thread gripper fixed in the tensile test jig, and the suture was clamped so that the test specimen and the suture were aligned in a straight line. Five measurements were performed at a test speed of 50 mm / min, and the average of the maximum test force (N) was calculated and used as the suture retention strength. The value obtained from a test specimen cut along the machine direction (MD) of the polyethylene microporous membrane was used as S. ＭＤ The value obtained from a test piece cut out along the longitudinal direction (TD) of the polyethylene microporous membrane was defined as S ＴＤFurthermore, the obtained S ＭＤ value and S ＴＤ From the values, the ratio (S ＴＤ / S ＭＤ ) was sought.

[0057] [Example 1] 12 parts by mass of ultra-high molecular weight polyethylene (UHMWPE) having a weight average molecular weight (Mw) of 4.6 million and 12 parts by mass of polyethylene terephthalate having a weight average molecular weight (Mw) of 560,000 and a density of 950 kg / m ３ A polyethylene composition was used, which was a mixture of 18 parts by mass of high-density polyethylene (HDPE) and 70 parts by mass of liquid paraffin, to prepare a polyethylene solution with a total polyethylene resin concentration of 30% by mass. This polyethylene solution was extruded into a sheet from a die at 181°C. The extrudate was then cooled to 15°C in a water bath, and a water flow was created on the surface of the water bath to prevent the mixed solvent, which had been released from the gelled sheet and floated on the water surface, from re-adhering to the sheet. This produced a gel-like sheet (base tape). The gel-like sheet was pre-dried at 55°C for 22 minutes, then stretched 2.3 times in the machine direction at 100°C, followed by a second stretch of 5.1 times in the transverse direction at 115°C. Immediately after the second stretching, it was heat-treated (heat-set) at 128°C. The heat-set sheet was continuously immersed in three separate methylene chloride baths for a total of 12 minutes to extract the solvent from the sheet. The sheet was taken out of the methylene chloride bath and then dried on a heated roll at 39° C. to remove the methylene chloride. The sheet was then annealed in a heated atmosphere at 120° C. Through the above steps, a polyethylene microporous membrane was obtained.

[0058] [Example 2] 15 parts by mass of ultra-high molecular weight polyethylene (UHMWPE) having a weight average molecular weight (Mw) of 4.6 million and 15 parts by mass of polyethylene terephthalate having a weight average molecular weight (Mw) of 560,000 and a density of 950 kg / m ３A polyethylene composition was prepared by mixing the polyethylene composition with 85 parts by mass of high-density polyethylene (HDPE). Next, a polyethylene solution was prepared by mixing the polyethylene composition with decalin as a solvent so that the concentration of the polyethylene composition was 30% by mass. This polyethylene solution was extruded into a sheet form through a die at 160°C, and the extrudate was then cooled in a water bath at 20°C to obtain a first gel-like sheet. The first gel-like sheet was pre-dried at 60°C for 15 minutes, then stretched in the MD direction at 100°C at a ratio of 1.25 times, and then dried at 55°C for 10 minutes to obtain a second gel-like sheet. The residual amount of solvent in the second gel-like sheet was adjusted to less than 1% by mass. Next, as a second stretching step, the second gel-like sheet was stretched in the MD direction at 80°C at a ratio of 1.9 times, and then stretched in the TD direction at 125°C at a ratio of 4.4 times. Immediately after the second stretching step, a heat treatment (heat setting) was performed at 130°C. The heat-set sheet was continuously immersed in a methylene chloride bath for a total of 1 minute to extract the solvent from the sheet. After removing the sheet from the methylene chloride bath, the sheet was dried on a heated roll at 40°C to remove the methylene chloride. The sheet was then annealed in a heated atmosphere at 80°C. A polyethylene microporous membrane was obtained through the above steps.

[0059] [Example 3] 3.4 parts by mass of ultra-high molecular weight polyethylene (UHMWPE) having a weight average molecular weight (Mw) of 4.6 million and 1.0 parts by mass of polyethylene terephthalate having a weight average molecular weight (Mw) of 560,000 and a density of 950 kg / m ３A polyethylene composition was used, which was a mixture of 13.6 parts by mass of high-density polyethylene (HDPE) of 1,000 ppm by mass. A polyethylene solution was prepared by mixing 51 parts by mass of liquid paraffin and 32 parts by mass of decalin so that the total polyethylene resin concentration was 17% by mass. This polyethylene solution was extruded into a sheet through a die at 157°C, and the extrudate was then cooled in a water bath at 15°C to obtain a first gel-like sheet. The first gel-like sheet was pre-dried at 70°C for 10.5 minutes, then first stretched 3.0 times in the MD direction at 100°C, and then secondly stretched 4.0 times in the TD direction at 110°C. Immediately after the second stretching, the sheet was heat-treated (heat-set) at 133°C. The heat-set sheet was continuously immersed in three separate methylene chloride baths for a total of 12 minutes to extract the solvent from the sheet. The sheet was taken out of the methylene chloride bath and then dried on a heated roll at 39° C. to remove the methylene chloride. The sheet was then annealed in a heated atmosphere at 120° C. Through the above steps, a polyethylene microporous membrane was obtained.

[0060] [Comparative Example 1] 15 parts by mass of ultra-high molecular weight polyethylene (UHMWPE) having a weight average molecular weight (Mw) of 4.6 million and 15 parts by mass of polyethylene terephthalate having a weight average molecular weight (Mw) of 560,000 and a density of 950 kg / m ３A polyethylene composition was prepared by mixing the polyethylene composition with 85 parts by mass of high-density polyethylene (HDPE). Next, a polyethylene solution was prepared by mixing the polyethylene composition with decalin as a solvent so that the concentration of the polyethylene composition was 30% by mass. This polyethylene solution was extruded into a sheet from a die at 159°C, and the extrudate was then cooled in a water bath at 20°C to obtain a first gel-like sheet. The first gel-like sheet was pre-dried at 60°C for 10 minutes, then primarily stretched in the MD direction at 1.3 times its original size, and then fully dried at 55°C for 7 minutes to obtain a second gel-like sheet. The residual amount of solvent in the second gel-like sheet was adjusted to less than 1% by mass. Next, as a second stretching step, the second gel-like sheet was stretched in the MD direction at 80°C at a stretching ratio of 2.5 times, and then in the TD direction at 125°C at a stretching ratio of 6.0 times. Immediately after the second stretching step, a heat treatment (heat setting) was performed at 134°C. The heat-set sheet was continuously immersed in a methylene chloride bath for a total of 1 minute to extract the solvent from the sheet. After removing the sheet from the methylene chloride bath, the sheet was dried on a heated roll at 40°C to remove the methylene chloride. The sheet was then annealed in a heated atmosphere at 80°C. A polyethylene microporous membrane was obtained through the above steps.

[0061] [Comparative Example 2] 15 parts by mass of ultra-high molecular weight polyethylene (UHMWPE) having a weight average molecular weight (Mw) of 4.6 million and 15 parts by mass of polyethylene terephthalate having a weight average molecular weight (Mw) of 560,000 and a density of 950 kg / m ３A polyethylene composition was prepared by mixing the polyethylene composition with 85 parts by mass of high-density polyethylene (HDPE). Next, a polyethylene solution was prepared by mixing the polyethylene composition with decalin as a solvent so that the concentration of the polyethylene composition was 30% by mass. This polyethylene solution was extruded into a sheet form through a die at 160°C, and the extrudate was then cooled in a water bath at 20°C to obtain a first gel-like sheet. The first gel-like sheet was pre-dried at 60°C for 15 minutes, then primarily stretched in the MD direction at 1.3 times its original size, and then fully dried at 55°C for 10 minutes to obtain a second gel-like sheet. The residual amount of solvent in the second gel-like sheet was adjusted to less than 1% by mass. Next, as a second stretching step, the second gel-like sheet was stretched in the MD direction at 80°C at a stretching ratio of 2.0 times, and then in the TD direction at 125°C at a stretching ratio of 4.7 times. Immediately after the second stretching step, a heat treatment (heat setting) was performed at 130°C. The heat-set sheet was continuously immersed in a methylene chloride bath for a total of 1 minute to extract the solvent from the sheet. After removing the sheet from the methylene chloride bath, the sheet was dried on a heated roll at 40°C to remove the methylene chloride. The sheet was then annealed in a heated atmosphere at 80°C. A polyethylene microporous membrane was obtained through the above steps.

[0062] [Evaluation] The polyethylene microporous membranes obtained as described above were evaluated as follows. The results are shown in Table 1.

[0063] (Workability) Using surgical scissors (manufactured by Matsuyoshi Medical Instruments) (Medical Device Notification Number: 11B3X00081000017), the polyethylene microporous membrane was trimmed into a circle with a radius of 3 cm. The ease of trimming was evaluated according to the following criteria. - Criteria - 1. Easy to cut and easy to work with 2. Cuttable but catches 3. Difficult to cut

[0064] (Liquid Leakage) A polyethylene microporous membrane was cut into a size of 200 mm x 200 mm. A polypropylene monofilament suture (Prolene 5-0 M8321) was sewn into the center of this polyethylene microporous membrane with five stitches to prepare a test specimen for testing liquid leakage through a pinhole. The water resistance of this test specimen was measured in accordance with JIS L 1092:2009 Method A (low water pressure method). A water resistance of 150 mm or more was evaluated as A, and a water resistance of less than 150 mm was evaluated as B.

[0065]

[0066] The evaluation results in Table 1 show that the polyethylene microporous membranes of Examples have superior workability and suppress liquid leakage at sites fixed by means such as sutures, compared to the polyethylene microporous membranes of Comparative Examples.

[0067] The disclosure of Japanese Patent Application No. 2024-055062, filed on March 28, 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated by reference into this specification to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A polyethylene microporous membrane containing polyethylene, wherein the suture retention strength (S) of the polyethylene microporous membrane in the machine direction (MD) is ＭＤ ) is 1.5 N or more, and the suture retention strength (S ＴＤ ) is 1.5N or more, and the suture retention strength (S ＴＤ ) the suture retention strength (S ＭＤ ) to the ratio (S ＴＤ / S ＭＤ ) is 0.8 to 1.

2.

2. The polyethylene microporous membrane according to claim 1, wherein a parameter A represented by the following formula (A) exceeds 60, where ε (%) is the porosity of the polyethylene microporous membrane and t (μm) is the thickness of the polyethylene microporous membrane: A=(2-ε / 50): １．５ ×t Formula (A) 3. The microporous polyethylene membrane according to claim 1, wherein the proportion of ultra-high molecular weight polyethylene having a weight-average molecular weight of 3,000,000 to 6,000,000 in the polyethylene is 50 mass% or less.

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

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

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

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