Polyethylene microporous film, and medical device

Abstract

To provide a polyethylene microporous film excellent in workability, and inhibiting leakage of a liquid from a place fixed by means such as stitching.SOLUTION: A polyethylene microporous film includes polyethylene, where a stitch retention strength (SMD) in a longitudinal direction (MD) of the polyethylene microporous film is 1.5 N or more, a stitch retention strength (STD) in a transverse direction (TD) of the polyethylene microporous film is 1.5 N or more, and a ratio (STD / SMD) of the stitch retention strength (STD) to the stitch retention strength (SMD) is 0.8 to 1.2.SELECTED DRAWING: None

Description

[Technical Field]

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

[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 substitutes, 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, European PFAS regulations have 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 mesh, wound care products, tubes, and catheters) and medical device tubes and catheter applications and products are subject to reporting, although there is a grace period (13.5 years), and early replacement with alternative products is recommended.

[0004] Porous polyolefin membranes, particularly ultra-high molecular weight polyethylene (UHMWPE) porous membranes, can be used in a variety of 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. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-314593 [Patent Document 2] Patent No. 7343104 Summary of the Invention [Problem to be solved by the invention]

[0006] In the field of implantable materials, high tear strength is required in all directions when sutured, while patch materials require uniform physical properties across the membrane surface. Particularly in biomedical or surgical applications, it is necessary to fix the implant in place or to another component by means such as metal clamps or stitching. Holes (pinholes) resulting from clamping or stitching can be stress concentrations and / or small defects that can promote or induce tearing and premature failure of the porous membrane under mechanical load. To overcome tearing and premature failure of the porous membrane during use, it is very important to improve the suture retention strength. However, in the polyolefin porous membrane described in Patent Document 2, the pores in the film are partially filled with an elastomer, and although the strength of the filled parts is high, sufficient strength cannot be obtained when sewing is performed at parts other than the filled parts. Therefore, tearing and early breakage are promoted or induced from parts of the porous membrane that are not strong, and leakage of liquid from broken parts of the porous membrane or pinholes may not be sufficiently prevented. Furthermore, since the resin density differs between the elastomer-filled portion and the non-filled portion, the polyolefin porous membrane described in Patent Document 2 tends to exhibit anisotropic strength. Therefore, when cutting the polyolefin porous membrane described in Patent Document 2 into a desired shape, the ease of cutting tends to vary, and the polyolefin porous membrane cannot necessarily be said to be excellent in workability. The present disclosure has been made in consideration of the above-described conventional circumstances, and aims to provide a polyethylene microporous membrane that is easy to work with and inhibits liquid leakage at sites fixed by means such as suturing, and a medical device using the same. [Means for solving the problem]

[0007] Specific means for achieving the above object are as follows. <1> A polyethylene microporous membrane comprising polyethylene, The suture retention strength (S MD ) is 1.5N or more, The suture retention strength (S TD ) is 1.5N or more, The suture retention strength (S TD ) of the suture retention strength (S MD ) to the ratio (S TD / S MD ) is 0.8 to 1.2. <2> When the porosity of the polyethylene microporous membrane is ε (%) and the thickness of the polyethylene microporous membrane is t (μm), parameter A represented by the following formula (A) exceeds 60: <1> The polyethylene microporous membrane according to claim 1. A=(2-ε / 50) 1.5 ×t formula (A) <3> The proportion of ultra-high molecular weight polyethylene having a weight average molecular weight of 3 million to 6 million in the polyethylene is 50 mass% or less. <1> or <2> The polyethylene microporous membrane according to claim 1. <4> The porosity ε (%) of the polyethylene microporous membrane is 35% to 90%. <1> ~ <3> The polyethylene microporous membrane according to any one of claims 1 to 10. <5> The thickness t (μm) of the polyethylene microporous membrane is 40 μm to 300 μm. <1> ~ <4> The polyethylene microporous membrane according to any one of claims 1 to 10. <6> <1> ~ <5> A medical device comprising the polyethylene microporous membrane according to any one of claims 1 to 4. [Effects of the Invention]

[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. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 10 is a diagram for explaining a method for measuring the suture retention strength in the examples. DETAILED DESCRIPTION OF THE INVENTION

[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 a process that is independent of other processes, but also a process 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 the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. In the present disclosure, each component may contain multiple substances corresponding to the component. When multiple substances corresponding to each component are present in the composition, the content or amount of each component means 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 area when the area in which the layer or film is present is observed, as well as cases where the layer or film is formed over only a portion of the area.

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

[0013] <Polyethylene microporous membrane> The polyethylene microporous membrane of the present disclosure comprises polyethylene, and the polyethylene microporous membrane has a suture retention strength (S MD ) is 1.5 N or more, and the suture retention strength of the polyethylene microporous membrane in the transverse direction (TD) is (S TD ) 1.5N or more, and the suture retention strength (S TD ) of the suture retention strength (S MD ) to the ratio (S TD / S MD ) is set to 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 ) exhibit high strength of 1.5 N or more, so the porous membrane is less likely to break or tear from pinholes. Therefore, leakage of liquid from areas 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 (STD / S MD ) is 0.8 to 1.2, exhibiting isotropic strength, so there is less unevenness in the ease of cutting the polyethylene microporous membrane into a desired shape, and workability tends to be excellent. From the above, it is presumed that the polyethylene microporous membrane of the present disclosure has excellent workability and suppresses liquid leakage at locations 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 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 The value may be 5.0N or less. In the present disclosure, the suture retention strength (S TD ) is 1.5N or more. TD 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. TD The value may be 5.0N or less. S 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 that are subject 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 this disclosure, the ratio (S TD / S MD ) is set to 0.8 to 1.2, preferably 0.85 to 1.15, and more preferably 0.9 to 1.1. Ratio(S TD / S MD ) in the range of 0.8 to 1.2, the polyethylene microporous membrane will exhibit isotropic strength, and the workability of the polyethylene microporous membrane will tend to be improved. The ratio (S 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 favorable 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, 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 this disclosure, the porosity of a polyethylene microporous membrane refers to the value determined by the method described in the Examples section.

[0019] (film thickness) The polyethylene microporous membrane of the present disclosure preferably has a thickness of 40 μm to 300 μm. When the polyethylene microporous membrane has a thickness of 40 μm or more, handleability tends to be improved. The polyethylene microporous membrane of the present disclosure preferably has a thickness of 40 μm or more, more preferably 50 μm or more, and even more preferably 60 μm or more. On the other hand, when the polyethylene microporous membrane has a thickness of 300 μm or less, flexibility tends to be improved. The polyethylene microporous membrane has a thickness of 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, parameter A represented by the following formula (A) preferably exceeds 60, more preferably is 62 or more, and even more preferably is 65 or more, 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 may be 120 or less, preferably 100 or less, and more preferably 90 or less, from the viewpoint of a balance between flexibility and ability to penetrate into the porous structure of surrounding tissue. Parameter A is preferably greater 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 diameter) In the present disclosure, the pore size of the polyethylene microporous membrane is preferably 0.01 μm to 5 μm. When the pore size of the polyethylene microporous membrane is 0.01 μm or more, penetration of surrounding tissue into the porous structure tends to be improved. 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, when the pore size of the polyethylene microporous membrane is 5 μm or less, a tissue blocking effect that makes it possible to prevent penetration and adhesion of surrounding tissue tends to be obtained. 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 this disclosure, the pore size of a polyethylene microporous membrane refers to the value determined by the method described in the Examples section.

[0023] (Piercing strength) The 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 prevention. The 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 puncture strength of the polyethylene microporous membrane of the present disclosure is preferably 400 gf to 1000 gf. In this disclosure, the pin puncture strength of a polyethylene microporous membrane refers to the 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 prevention. 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 a polyethylene microporous membrane refers to the value determined by the method described in the Examples section.

[0025] (Components of polyethylene microporous membrane) The microporous polyethylene membrane of the present disclosure comprises polyethylene. The microporous polyethylene membrane of the present disclosure may be made of polyethylene alone, or may be made 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 film may contain one type of polyethylene or two or more types of polyethylene 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 UHMWPE, 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 resin components constituting the polyethylene microporous membrane is preferably 50% by mass or less. When the proportion of ultra-high molecular weight polyethylene in the resin components 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 components 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 the ultra-high molecular weight polyethylene in the resin content constituting the polyethylene microporous membrane is preferably 1% by mass or more. When the proportion of the ultra-high molecular weight polyethylene in the resin content constituting the polyethylene microporous membrane is 1% by mass or more, the mechanical strength of the polyethylene microporous membrane is likely to be increased. The proportion of the ultra-high molecular weight polyethylene in the resin content constituting the polyethylene microporous membrane is more preferably 3% by mass or more, and even more preferably 5% by mass or more.

[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 means polyethylene having a weight average molecular weight of 3,000,000 to 6,000,000. The weight-average molecular weight of the ultra-high molecular weight polyethylene is preferably 3.5 million or more, more preferably 4 million or more, and is preferably 5 million or less, more preferably 4.8 million or less.

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

[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 microporous polyethylene membrane of the present disclosure, the pores within the microporous polyethylene membrane may be at least partially filled with an elastomer. The elastomer that at least partially fills the pores includes a polymer selected from the group consisting of polyesters, polyamides, polystyrenes, polyacrylates, polyurethanes, polyolefins, polyethers, and polysiloxanes (or silicones), or combinations thereof.

[0034] (Uses of polyethylene microporous membrane) The use of the polyethylene microporous membrane is 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 microporous polyethylene 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 mixture 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 molding in at least one direction (primary stretching) and drying the solvent to obtain a second gel-like molding. Step (IV): A step of stretching the second gel-like molding 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 that are used as needed. As the solvent, a solution containing 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 can be used. 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 solvents 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 breakage during the polyethylene microporous membrane production process, and also increases the mechanical strength and handleability of the polyethylene microporous membrane. 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 shaped product in at least one direction (primary stretching) and drying the solvent to obtain a second gel-like shaped 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. 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 times, more preferably 1.1 to 3.5 times, from the viewpoint of controlling the porous structure of the polyethylene microporous membrane. The temperature during the primary stretching is preferably 120°C or lower. The drying of the solvent in step (III) (drying step) is preferably carried out at a temperature at which the second gel-like shaped product does not deform, more preferably at 80° C. or lower.

[0042] The stretching and drying steps 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 followed by 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. The polyethylene microporous membrane immersed in the methylene chloride bath is preferably removed from the bath by drying after being withdrawn from the bath. 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 Devices> The medical device of the present disclosure comprises the microporous polyethylene membrane of the present disclosure. The polyethylene microporous membrane of the present disclosure has excellent workability and inhibits liquid 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. Additionally, the polyethylene microporous membrane of the present disclosure can be fabricated into medical devices for temporary or permanent use in the body, such as vascular devices such as vascular grafts, occlusion devices, stent covers or catheter balloons, and artificial cartilage replacement materials. Furthermore, it can also be used as a material for constructing medical implants, particularly orthopedic implants used in orthopedic surgery related to the musculoskeletal system. The medical device of the present disclosure can be suitably used for the various bioimplant materials described above. [Example]

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

[0051] (film thickness) The thickness of the polyethylene microporous membrane was measured using a contact-type film thickness meter (Mitutoyo Corporation, ABS Digimatic Indicator, Model ID: ID-S112X). Specifically, the thickness of the polyethylene microporous membrane was measured at 20 points, and the arithmetic mean value was taken 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 Ws: basis weight of polyethylene microporous membrane (g / m 2 ) ds: True density of polyethylene (g / cm 3 ) t: Thickness of the polyethylene microporous membrane (μm) The basis weight of the polyethylene microporous membrane was determined by cutting a sample to a size of 10 cm x 10 cm, 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)) Based on the thickness and porosity of the polyethylene microporous membrane measured as described above, parameter A represented by formula (A) was calculated.

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

[0055] (Piercing strength) The puncture test was performed using a Kato Tech KES-G5 handy compression tester with 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. The sample was clamped and fixed in a metal frame (specimen 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 arithmetic average was calculated.

[0056] (Suture retention strength) The method for measuring the suture retention strength will be explained with reference to the drawings. Suture retention strength was measured using a Shimadzu EZ-SX compact benchtop testing machine (model QC-005-02). Test specimens were cut to 10 mm x 50 mm as shown in Figure 1(a). Five specimens were cut so that their longitudinal direction was aligned with the machine direction (MD) of the polyethylene microporous membrane, and five specimens were cut so that their longitudinal direction was aligned with the machine 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 specimen and 30 mm from that end, as shown in Figure 1(b). A hole was drilled at the 2 mm marking, taking care not to widen the hole due to the load from the needle. For example, a hole could be drilled on a urethane foam board, aligning the needle's curvature so that the needle always penetrates perpendicularly to the film. A 5-0 surgical polypropylene monofilament suture (Prolene 5-0 M8321) was threaded through the 2 mm marking. The length of the suture was adjusted to 15cm or more by folding the suture 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 suture were in a straight line. Measurements were carried out five times at a test speed of 50mm / min, and the average of the maximum test force (N) was calculated and used as the suture retention strength. The value obtained from the test specimen cut along the machine direction (MD) of the polyethylene microporous membrane was used as S. MDThe value obtained from a test piece cut out along the machine direction (TD) of the polyethylene microporous membrane was defined as S TD The value was set as Furthermore, the obtained S MD Value and S TD From the value, the ratio (S TD / S MD ) was sought.

[0057] [Example 1] 12 parts by mass of ultra-high molecular weight polyethylene (UHMWPE) with a weight average molecular weight (Mw) of 4.6 million and 12 parts by mass of polyethylene terephthalate (PE) with a weight average molecular weight (Mw) of 560,000 and a density of 950 kg / m 3 A polyethylene composition was used, which was mixed with 18 parts by mass of high-density polyethylene (HDPE) of 1.0% by mass. A polyethylene solution was prepared by mixing the polyethylene composition with 70 parts by mass of liquid paraffin so that the total concentration of the polyethylene resin was 30% by mass. This polyethylene solution was extruded into a sheet form through a die at a temperature of 181°C, and the extrudate was then cooled to 15°C in a water bath. A water flow was created on the surface of the water bath to prevent the mixed solvent released from the gelled sheet and floating on the water surface from adhering to the sheet again, producing a gel-like sheet (base tape). The gel-like sheet was pre-dried at 55°C for 22 minutes, then first stretched 2.3 times in the MD at 100°C, and then secondly stretched 5.1 times in the TD at 115°C. Immediately after the second stretching, the sheet was heat-treated (heat-set) at 128°C. The heat-set sheet was immersed in three separate methylene chloride baths for a total of 12 minutes 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 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) with a weight average molecular weight (Mw) of 4.6 million and 15 parts by mass of polyethylene terephthalate (PE) with a weight average molecular weight (Mw) of 560,000 and a density of 950 kg / m 3A polyethylene composition was prepared by mixing 85 parts by mass of high-density polyethylene (HDPE) containing 1,000 parts of polyethylene glycol fluoride (PEF) and 85 parts by mass of high-density polyethylene (HDPE). Next, the polyethylene composition was mixed with decalin as a solvent so that the concentration of the polyethylene composition was 30% by mass, thereby preparing a polyethylene solution. This polyethylene solution was extruded into a sheet form through a die at a temperature of 160°C, and the extrudate was then cooled in a water bath at a water temperature of 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 by 1.25 times, and then dried at 55°C for 10 minutes to obtain a second gel-like sheet. The residual solvent content in the second gel-like sheet was less than 1% by mass. Next, as the second stretching, the second gel-like sheet was stretched in the MD direction at a stretching ratio of 1.9 at a temperature of 80° C., and then stretched in the TD direction at a stretching ratio of 4.4 at a temperature of 125° C. Immediately after the second stretching, a heat treatment (heat setting) at 130° C. was carried out. The heat-set sheet was 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. Through the above steps, a polyethylene microporous membrane was obtained.

[0059] [Example 3] 3.4 parts by mass of ultra-high molecular weight polyethylene (UHMWPE) with a weight average molecular weight (Mw) of 4.6 million and 560,000 parts by mass of polyethylene terephthalate (PE) with a density of 950 kg / m 3 A polyethylene composition was used in which 13.6 parts by mass of high-density polyethylene (HDPE) was mixed with 51 parts by mass of liquid paraffin and 32 parts by mass of decalin so that the total concentration of the polyethylene resin was 17% by mass, to prepare a polyethylene solution. This polyethylene solution was extruded into a sheet form through a die at a temperature of 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 at 100°C, and then secondly stretched 4.0 times in the TD at 110°C. Immediately after the second stretching, the sheet was heat-treated (heat-set) at 133°C. The heat-set sheet was immersed in three separate methylene chloride baths for a total of 12 minutes 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 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) with a weight average molecular weight (Mw) of 4.6 million and 15 parts by mass of polyethylene terephthalate (PE) with a weight average molecular weight (Mw) of 560,000 and a density of 950 kg / m 3 A polyethylene composition was prepared by mixing 85 parts by mass of high-density polyethylene (HDPE) containing 1,000 parts of polyethylene glycol fluoride (PEF) and 85 parts by mass of high-density polyethylene (HDPE). Next, the polyethylene composition was mixed with decalin as a solvent so that the concentration of the polyethylene composition was 30% by mass, thereby preparing a polyethylene solution. This polyethylene solution was extruded into a sheet form through a die at a temperature of 159°C, and the extrudate was then cooled in a water bath at a water temperature of 20°C to obtain a first gel-like sheet. The first gel-like sheet was pre-dried at 60°C for 10 minutes, then stretched in the MD direction at 1.3 times its original size, and then dried at 55°C for 7 minutes to obtain a second gel-like sheet. The residual solvent content in the second gel-like sheet was less than 1% by mass. Next, as the second stretching, the second gel-like sheet was stretched in the MD direction at a stretching ratio of 2.5 at a temperature of 80° C., and then stretched in the TD direction at a stretching ratio of 6.0 at a temperature of 125° C. Immediately after the second stretching, a heat treatment (heat setting) at 134° C. was carried out. The heat-set sheet was 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. Through the above steps, a polyethylene microporous membrane was obtained.

[0061] Comparative Example 2 15 parts by mass of ultra-high molecular weight polyethylene (UHMWPE) with a weight average molecular weight (Mw) of 4.6 million and 15 parts by mass of polyethylene terephthalate (PE) with a weight average molecular weight (Mw) of 560,000 and a density of 950 kg / m 3 A polyethylene composition was prepared by mixing 85 parts by mass of high-density polyethylene (HDPE) containing 1,000 parts of polyethylene glycol fluoride (PEF) and 85 parts by mass of high-density polyethylene (HDPE). Next, the polyethylene composition was mixed with decalin as a solvent so that the concentration of the polyethylene composition was 30% by mass, thereby preparing a polyethylene solution. This polyethylene solution was extruded into a sheet form through a die at a temperature of 160°C, and the extrudate was then cooled in a water bath at a water temperature of 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 1.3 times its original size, and then dried at 55°C for 10 minutes to obtain a second gel-like sheet. The residual solvent content in the second gel-like sheet was less than 1% by mass. Next, as the second stretching, the second gel-like sheet was stretched in the MD direction at a stretching ratio of 2.0 at a temperature of 80° C., and then stretched in the TD direction at a stretching ratio of 4.7 at a temperature of 125° C. Immediately after the second stretching, a heat treatment (heat setting) at 130° C. was carried out. The heat-set sheet was 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. Through the above steps, a polyethylene microporous membrane was obtained.

[0062] [evaluation] The polyethylene microporous membrane obtained as described above was evaluated as follows, and the results are shown in Table 1.

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

[0064] (liquid leakage) A polyethylene microporous membrane was cut into a 200 mm x 200 mm piece. A polypropylene monofilament suture (Prolene 5-0 M8321) was sewn into the center of the 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 according to JIS L 1092:2009 Method A (low water pressure method). A water resistance of 150 mm or more was rated A, and a water resistance of less than 150 mm was rated B.

[0065] [Table 1]

[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.

Claims

1. A polyethylene microporous membrane comprising polyethylene, The suture retention strength (S ＭＤ ) is 1.5 N or more, The suture retention strength (S ＴＤ ) is 1.5 N or more, 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 Equation (A)

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

5. The polyethylene microporous membrane according to claim 1, which 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 claims 1 to 5.

Images