JP7103715B2 - Polyolefin microporous membranes, filters, chromatographic carriers and slides for immunochromatography - Google Patents

Description

The present invention relates to polyolefin microporous membranes, filters, chromatographic carriers and strips for later later chromatographs.

Patent Document 1 states that the thickness is 1 to 350 μm, the porosity is 25 to 90%, the bubble point is 1 to 10 kg / cm ² , the water permeability is 1000 liters / hr · m ² · atm or more, and the surface water droplet contact angle is 100. A modified polyolefin porous membrane having a temperature of ゜ or less is disclosed.
Patent Document 2 discloses a polyolefin microporous membrane having an average fibril diameter of 40 to 80 nm and an average pore diameter of 15 to 50 nm.
Patent Document 3 discloses a polyolefin microporous membrane having a water vapor permeation amount of 4000 to 10000 g / m ^2/24 hr and a water pressure resistance of 30 kPa or more.

Japanese Unexamined Patent Publication No. 7-246322 Japanese Unexamined Patent Publication No. 2010-53245 Japanese Unexamined Patent Publication No. 2014-61505

The polyolefin microporous membrane may be used as a filter, a chromatography carrier, or the like for the purpose of separating, purifying, or detecting a substance. In order to improve the accuracy or speed of separation or purification of substances, there is a demand for a polyolefin microporous membrane having a small difference in porous structure between the plane direction and the thickness direction and having excellent isotropic mass transfer.

The embodiments of the present disclosure have been made under the above circumstances.
An object of the present disclosure is to provide a polyolefin microporous membrane having excellent isotropic mass transfer, and it is an object of the present invention to solve this.

Specific means for solving the above problems include the following aspects.

[1] A microporous polyolefin membrane having a film thickness of 1 μm to 400 μm and satisfying the following formulas (1) and (2).
Equation (1): 0.7 ≤ τ _X / τ _Z ≤ 1.5
Equation (2): 0.7 ≤ τ _Y / τ _Z ≤ 1.5
τ _X : Curvature ratio in the first direction along the first surface of the polyolefin microporous membrane.
τ _Y : Curvature ratio in the second direction along the first plane of the polyolefin microporous membrane and orthogonal to the first direction.
τ _Z : Curvature ratio in the thickness direction of the polyolefin microporous membrane.
[2] A microporous polyolefin membrane having a film thickness of 1 μm to 400 μm and satisfying the following formulas (3) and (4).
Equation (3): 0.5 ≤ _TX / _TZ ≤ 2.0
Equation (4): 0.5 ≤ _TY / _TZ ≤ 2.0
_TX : Permeability index in the first direction along the first surface of the polyolefin microporous membrane.
_TY : Permeability index in the second direction along the first surface of the polyolefin microporous membrane and orthogonal to the first direction.
_TZ : Permeability index in the thickness direction of the polyolefin microporous membrane.
[3] The polyolefin microporous membrane according to [1] or [2], wherein the bubble point pressure is 0.001 MPa or more and less than 0.1 MPa.
[4] The value according to any one of [1] to [3], wherein the value obtained by multiplying the ethanol flow rate (mL / (min · cm ² · MPa)) and the film thickness (μm) is 50,000 to 500,000. Polyolefin microporous membrane.
[5] The microporous polyolefin membrane according to any one of [1] to [4], wherein the galley value per unit thickness is 0.0005 seconds / 100 mL · μm to 0.1 seconds / 100 mL · μm.
[6] The polyolefin microporous membrane according to any one of [1] to [5], which has a porosity of 70% to 95%.
[7] The polyolefin according to any one of [1] to [6], which is a hydrophilic polyolefin microporous membrane and has a contact angle of water of 0 to 90 degrees after 1 second of dropping on at least one surface. Microporous membrane.
[8] The polyolefin microporous film according to [7], wherein the hydrophilic polyolefin microporous film has a hydrophilic material on at least one of the membrane surface and the inner surface of the pores.
[9] The hydrophilic polyolefin microporous membrane is a polyolefin microporous membrane in which at least one of the membrane surface and the inner surface of the pores is physically hydrophilized, according to [7] or [8]. Polyolefin microporous membrane.
[10] A filter containing the microporous polyolefin membrane according to any one of [1] to [9].
[11] A chromatography carrier containing the polyolefin microporous membrane according to any one of [1] to [9].
[12] The polyolefin microporous membrane according to any one of [1] to [9] and a detection reagent provided on the polyolefin microporous membrane that specifically binds to the substance to be detected are fixed. A strip for the immunochromatography, including the detector.

According to the embodiment of the present disclosure, a polyolefin microporous membrane having excellent isotropic mass transfer is provided.

It is a schematic diagram which showed the structure of the strip for an immunochromatography. It is a cross-sectional image obtained from the X-ray CT of the polyolefin microporous membrane of Example 1. It is a cross-sectional image obtained from the X-ray CT of the polyolefin microporous membrane of Example 2. It is a cross-sectional image obtained from the X-ray CT of the polyolefin microporous membrane of Example 3. It is a cross-sectional image obtained from the X-ray CT of the microporous polyolefin membrane of Comparative Example 1. It is a cross-sectional image obtained from the X-ray CT of the polyolefin microporous membrane of Comparative Example 2. It is a graph which shows the time-dependent change of the absorbance in Example 2 and Comparative Example 1.

Hereinafter, embodiments of the invention will be described. These explanations and examples exemplify embodiments and do not limit the scope of the invention. The mechanism of action described in the present disclosure includes presumption, and its correctness does not limit the scope of the invention.

When the embodiment is described in the present disclosure with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. Further, the size of the members in each figure is conceptual, and the relative relationship between the sizes of the members is not limited to this.

The numerical range indicated by using "-" in the present disclosure indicates a range including the numerical values before and after "-" as the lower limit value and the upper limit value, respectively.

In the numerical range described stepwise in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. .. Further, in the numerical range described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.

In the present disclosure, the term "process" is included in this term not only as an independent process but also as long as the intended purpose of the process is achieved even if it cannot be clearly distinguished from other processes.

In the present disclosure, each component may contain a plurality of applicable substances. When referring to the amount of each component in the composition in the present disclosure, if a plurality of substances corresponding to each component are present in the composition, unless otherwise specified, the plurality of types present in the composition. It means the total amount of substances.

In the present disclosure, the "mechanical direction" means the long direction in a film, film or sheet manufactured in a long shape, and the "width direction" means a direction orthogonal to the "mechanical direction". In the present disclosure, the "machine direction" is also referred to as the "MD direction", and the "width direction" is also referred to as the "TD direction".

<Polyolefin microporous membrane>
The present disclosure provides a polyolefin microporous membrane with excellent isotropic mass transfer.

In the present disclosure, the polyolefin microporous membrane is a structure in which fibril-like polyolefin forms a three-dimensional network structure, has a large number of micropores inside, and these micropores are connected, and from one surface. Membrane that allows gas or liquid to pass through the other surface.

The present disclosure discloses a first polyolefin microporous membrane and a second polyolefin microporous membrane as polyolefin microporous membranes having excellent isotropic mass transfer.

The first polyolefin microporous membrane has a film thickness of 1 μm to 400 μm and satisfies the following formulas (1) and (2).

Equation (1): 0.7 ≤ τ _X / τ _Z ≤ 1.5
Equation (2): 0.7 ≤ τ _Y / τ _Z ≤ 1.5
τ _X : Curvature ratio in the first direction along the first surface of the polyolefin microporous membrane.
τ _Y : Curvature ratio in the second direction along the first plane of the polyolefin microporous membrane and orthogonal to the first direction.
τ _Z : Curvature ratio in the thickness direction of the polyolefin microporous membrane.

Here, the first surface of the polyolefin microporous membrane is one of the two main surfaces of the polyolefin microporous membrane (for example, when one surface is defined as the front surface, the front surface and the back surface correspond to the two main surfaces). Point to. The direction along the first surface of the polyolefin microporous membrane is orthogonal to the thickness direction of the polyolefin microporous membrane. Therefore, the first direction, the second direction, and the thickness direction are orthogonal to each other.

In the present disclosure, the tortuosity is an index showing how much the flow path through which the fluid flows detours with respect to the shortest distance, and the more the flow path detours, the larger the turnover rate.

The first polyolefin microporous membrane is excellent in isotropic mass transfer by simultaneously satisfying the formulas (1) and (2). When τ _X / τ _Z or τ _Y / τ _Z is less than 0.7 in the polyolefin microporous membrane, the degree of detouring of the flow path is too large in the thickness direction, and it is difficult for the fluid to spread in the thickness direction. When τ _X / τ _Z or τ _Y / τ _Z exceeds 1.5 in the polyolefin microporous membrane, the degree of detour of the flow path is too large in the plane direction, and it is difficult for the fluid to spread in the plane direction.

The first polyolefin microporous membrane preferably satisfies the formula (1'): 0.75 ≤ τ _X / τ _Z ≤ 1.3 from the viewpoint of being superior in the isotropic property of mass transfer, and the formula (1'). '): It is more preferable to satisfy 0.8 ≤ τ _X / τ _Z ≤ 1.1.

The first polyolefin microporous membrane preferably satisfies the formula (2'): 0.75 ≤ τ _Y / τ _Z ≤ 1.3 from the viewpoint of being superior in the isotropic property of mass transfer, and the formula (2'). '): It is more preferable to satisfy 0.8 ≤ τ _Y / τ _Z ≤ 1.1.

The first polyolefin microporous membrane preferably satisfies the formula (1) and the formula (2') at the same time, and more preferably the formula (1) and the formula (2 ″) at the same time.
The first polyolefin microporous membrane preferably satisfies the formulas (1') and (2) at the same time, more preferably the formulas (1') and (2') at the same time, and the formula (1'). It is more preferable that') and the equation (2'') are satisfied at the same time.
The first polyolefin microporous membrane preferably satisfies the formula (1 ″) and the formula (2) at the same time, more preferably the formula (1 ″) and the formula (2 ′) at the same time. It is more preferable that (1 ″) and the equation (2 ″) are satisfied at the same time.

The value of τ _X is not particularly limited, but is preferably 1.2 to 2.0, more preferably 1.2 to 1.8, and even more preferably 1.4 to 1.7.
The value of τ _Y is not particularly limited, but is preferably 1.2 to 2.0, more preferably 1.2 to 1.8, and even more preferably 1.4 to 1.7.
The value of τ _Z is not particularly limited, but is preferably 1.3 to 2.1, more preferably 1.5 to 2.0, and even more preferably 1.6 to 1.9.

The second polyolefin microporous membrane has a film thickness of 1 μm to 400 μm and satisfies the following formulas (3) and (4).

Equation (3): 0.5 ≤ _TX / _TZ ≤ 2.0
Equation (4): 0.5 ≤ _TY / _TZ ≤ 2.0
_TX : Permeability index in the first direction along the first surface of the polyolefin microporous membrane.
_TY : Permeability index in the second direction along the first surface of the polyolefin microporous membrane and orthogonal to the first direction.
_TZ : Permeability index in the thickness direction of the polyolefin microporous membrane.

Here, the first surface of the polyolefin microporous membrane is one of the two main surfaces of the polyolefin microporous membrane (for example, when one surface is defined as the front surface, the front surface and the back surface correspond to the two main surfaces). Point to. The direction along the first surface of the polyolefin microporous membrane is orthogonal to the thickness direction of the polyolefin microporous membrane. Therefore, the first direction, the second direction, and the thickness direction are orthogonal to each other.

In the present disclosure, the permeability index (Permeability) is an index indicating the ease of flow of the fluid with respect to the flow path through which the fluid flows, and the more easily the flow path of the fluid flows, the larger the permeability index. In the present disclosure, the permeability index is a wet area derived from the Darcy-Weisbach equation, and is in units of the square of the length (μm ² ).
Darcy-Weisbach's equation: k = QμL / ΔPA
k: Transparency index (μm ² )
Q: Outflow amount per unit time (μm ³ / s)
μ: Fluid viscosity (Pa · s)
L: Length of flow path (μm)
ΔP: Pressure difference (Pa)
A: Cross-sectional area (μm ² )

The second polyolefin microporous membrane is excellent in isotropic mass transfer by simultaneously satisfying the formulas (3) and (4). When _TX / _TZ or _TY / _TZ is less than 0.5 in the polyolefin microporous membrane, the fluid flows too much in the thickness direction as compared with the plane direction, and it is difficult for the fluid to spread in the plane direction. When _TX / _TZ or _TY / _TZ exceeds 2.0 in the polyolefin microporous membrane, the fluid flows too much in the plane direction as compared with the thickness direction, and it is difficult for the fluid to spread in the thickness direction.

The second polyolefin microporous membrane preferably satisfies the formula (3'): 0.8 ≤ _TX / _TZ ≤ 2.0 from the viewpoint of being superior in the isotropic property of mass transfer, and the formula (3'). '): It is more preferable to satisfy 0.9 ≤ _TX / _TZ ≤ 1.9.

The second polyolefin microporous membrane preferably satisfies the formula (4'): 0.75 ≤ _TY / _TZ ≤ 1.5 from the viewpoint of being superior in the isotropic property of mass transfer, and the formula (4'). ′): It is more preferable to satisfy 0.8 ≦ _TY / _TZ ≦ 1.1.

The second polyolefin microporous membrane preferably satisfies the formula (3) and the formula (4') at the same time, and more preferably the formula (3) and the formula (4 ″) at the same time.
The second polyolefin microporous membrane preferably satisfies the formulas (3') and (4) at the same time, more preferably the formulas (3') and (4') at the same time, and the formula (3'). It is more preferable that') and the equation (4'') are satisfied at the same time.
The second polyolefin microporous membrane preferably satisfies the formula (3 ″) and the formula (4) at the same time, more preferably the formula (3 ″) and the formula (4 ′) at the same time. It is more preferable that (3 ″) and the equation (4 ″) are satisfied at the same time.

The value of _TX is not particularly limited, but is preferably 0.4 to 3.0, more preferably 0.5 to 2.5, and even more preferably 1.0 to 2.0.
The value of _TY is not particularly limited, but is preferably 0.2 to 2.0, more preferably 0.3 to 1.9, and even more preferably 0.5 to 1.8.
The value of _TZ is not particularly limited, but is preferably 0.2 to 2.0, more preferably 0.3 to 1.9, and even more preferably 0.5 to 1.8.

A method for measuring the curvature ratio and the permeability index of the polyolefin microporous membrane will be described.

The polyolefin microporous film is subjected to X-ray computer tomography (X-ray CT), an X-ray transmission image is taken while rotating the sample from 0 ° to 180 °, and a three-dimensional image of the internal structure is computerized from the obtained image data. Rebuild with. The reconstructed three-dimensional image is image-converted by the image processing software ImageJ, and cross-sectional sequence data of 0.26 μm / pixel pitch is obtained for each of the three planes (XY plane, XZ plane, YZ plane). If necessary depending on the scanning direction of the X-ray CT, from the obtained sequence data, the axial direction of the sequence data is set to match the thickness direction of the polyolefin microporous film so that the Z direction of the three views coincides with the thickness direction of the polyolefin microporous film. Convert with. If necessary, the image processing software ImageJ is used to create a three-view drawing. The X direction and the Y direction of the three views are not particularly limited, but are, for example, coincide with the MD direction and the TD direction or the TD direction and the MD direction of the polyolefin microporous membrane, respectively.
Next, from the obtained sequence data, data of 300 μm in the X direction and 300 μm in the Y direction are taken out, and data of a length (μm) corresponding to the film thickness of the polyolefin microporous film is taken out in the Z direction. From the viewpoint of improving the analysis accuracy, it is preferable to extract the data of the central portion in the Z direction except for the data of several μm each in the upper and lower directions (for example, 5 μm each in the upper and lower directions).
The sequence data taken out with the above dimensions is taken into the image analysis software Aviso, converted into three-dimensional data of 0.26 μm / voxel, and the voids are extracted using the software. At that time, it is preferable to remove noise (for example, dots having a volume of 50 voxel or less are removed as noise due to reflection and scattering when photographing X-ray CT). Then, using the Pole network analysis function of the image analysis software Aviso, the centers of the nearest voids are connected in order in each of the X direction, the Y direction, and the Z direction to construct a network, and the contact area between the nearest voids is determined. Get as a parameter. Then, a simulation is performed in which a fluid flows in each of the X direction, the Y direction, and the Z direction with a constant amount of runoff per unit time, and the complexity and permeability of the network are analyzed. Of the extracted data, the length in the direction in which the fluid flows is defined as the length of the flow path, and the area of the plane orthogonal to the direction in which the fluid flows is defined as the cross-sectional area. The simulation conditions are fluid viscosity: 0.001 Pa · s, inlet pressure: 130 MPa, outlet pressure: 100 MPa, and the pressure difference between the inlet and outlet is 30 MPa.
From the analysis results of the network, τ _X , τ _Y and τ _Z , which are the curvature ratios in the X, Y and Z directions, and TX, T, which are the transparency indexes in the _X , Y and Z directions, respectively. _Y and _TZ are obtained. The curve ratio is the average value obtained by dividing the length of the network connecting one surface to the other surface by the shortest distance connecting the start point and the end point of the network. The permeability index is a coefficient derived from Darcy-Weisbach's equation. In Darcy-Weisbach's equation, Q is the amount of runoff per unit time, μ is the viscosity of the fluid, L is the length of the flow path, ΔP is the pressure difference, and A is the cross-sectional area. Find k.

The first polyolefin microporous membrane and the second polyolefin microporous membrane will be described in more detail. Matters common to the first polyolefin microporous membrane and the second polyolefin microporous membrane will be generically described as the polyolefin microporous membranes of the present disclosure.

The polyolefin microporous membrane of the present disclosure may be hydrophobic or hydrophilic. Since polyolefin is a hydrophobic resin, the polyolefin microporous membrane itself is hydrophobic. The polyolefin microporous membrane of the present disclosure may be a hydrophobic polyolefin microporous membrane that has not been subjected to a hydrophilic treatment, or may be a polyolefin microporous membrane that has been imparted with hydrophilicity by a hydrophilic treatment. Details of the method for hydrophilizing the polyolefin microporous membrane will be described later.

In the present disclosure, the hydrophilicity of the polyolefin microporous membrane means that the contact angle of water after 1 second of dropping is 90 degrees or less on at least one surface. The contact angle of water 1 second after dropping is a value measured by a measuring method described later.

Next, other properties other than the curving ratio and the permeability index in the microporous polyolefin membrane of the present disclosure will be described. The characteristics common to the hydrophobic polyolefin microporous membrane and the hydrophilic polyolefin microporous membrane will be described simply as "polyolefin microporous membrane".

[Film thickness]
The film thickness of the microporous polyolefin membrane of the present disclosure is appropriately 1 μm to 400 μm and may be selected within the range depending on the application. For example, it is 10 μm to 300 μm, 20 μm to 250 μm, and 30 μm to 200 μm. It is 40 μm to 150 μm.

[Bubble point pressure]
The bubble point pressure of the microporous polyolefin membrane of the present disclosure may be selected depending on the intended use, for example, 0.001 MPa or more and less than 0.1 MPa, 0.005 MPa to 0.08 MPa, and 0.007 MPa to 0. It is 0.05 MPa.
In the present disclosure, the bubble point pressure of the polyolefin microporous membrane is determined by immersing the polyolefin microporous membrane in ethanol and following the bubble point test method of JIS K3832: 1990, however, changing the liquid temperature during the test to 24 ± 2 ° C. It is a value obtained by performing a bubble point test while boosting the applied pressure at a boosting speed of 2 kPa / sec.

[Ethanol flow rate]
The ethanol flow rate of the microporous polyolefin membrane of the present disclosure may be selected according to the application. In the polyolefin microporous membrane of the present disclosure, the value obtained by multiplying the ethanol flow rate (mL / (min · cm ² · MPa)) and the film thickness (μm) is, for example, 50,000 to 500,000, and 80,000 to 40. It is 10,000, and it is 100,000 to 300,000.

In the present disclosure, the ethanol flow rate (mL / (min · cm ² · MPa) of the polyolefin microporous membrane is a constant differential pressure on the polyolefin microporous membrane set in a liquid permeable cell having a constant liquid permeability area (cm ² ). 100 mL of ethanol is permeated with (kPa), and the time (sec) required for 100 mL of ethanol to permeate is measured and converted into units.

[Gare value]
The galley value (seconds / 100 mL · μm) per unit thickness of the polyolefin microporous film of the present disclosure may be selected depending on the application, for example, 0.0005 to 0.1 and 0.005 to 0. It is 0.05 and is 0.01 to 0.03. In the present disclosure, the gullet value of the polyolefin microporous membrane is a value measured according to JIS P8117: 2009.

[Porosity]
The porosity of the microporous polyolefin membrane of the present disclosure may be selected depending on the intended use, for example, 70% to 95%, 75% to 93%, and 80% to 92%.

In the present disclosure, the porosity (%) of the polyolefin microporous membrane is calculated by the following formula.
Porosity (%) = {1- (Wa / xa + Wb / xb + Wc / xc + ... + Wn / xn) / t} x 100
Here, the constituent materials of the polyolefin microporous membrane are a, b, c, ..., N, and the masses of the constituent materials are Wa, Wb, Wc, ..., Wn (g / cm ² ), respectively. The true densities of the materials are xa, xb, xc, ..., Xn (g / cm ³ ), respectively, and the film thickness of the polyolefin microporous film is t (cm).

[Average flow hole diameter]
The average flow pore diameter of the polyolefin microporous membrane of the present disclosure may be selected depending on the intended use, for example, 0.02 μm to 5 μm, 0.05 μm to 4 μm, and 0.1 μm to 3.5 μm.

For the average flow pore diameter of the polyolefin microporous membrane, a Palm Porometer (model: CFP-1200-AEXL) manufactured by PMI was used, and Galwick (surface tension 15.9 din / cm) manufactured by PMI was used for immersion. Obtained based on the half-dry method specified in ASTM E1294-89.

[BET specific surface area]
The BET specific surface area of the microporous polyolefin membrane of the present disclosure may be selected depending on the intended use, for example, 1 m ² / g to 30 m ² / g, 2 m ² / g to 25 m ² / g, and 3 m ² / G to 20 m ² / g.

The BET specific surface area of the polyolefin microporous film was set by the nitrogen gas adsorption method under liquid nitrogen temperature using a specific surface area measuring device (model: BELSORP-mini) manufactured by Microtrac Bell Co., Ltd., and the relative pressure was set to 1.0. It is a value obtained by measuring the adsorption isotherm of × 10 ^-3 to 0.35 and analyzing it by the BET method.

[Puncture strength]
The microporous polyolefin membrane of the present disclosure has, for example, 0.05 g / μm to 1.5 g / μm, 0.07 g / μm to 1.2 g / μm, and 0. It is 08 g / μm to 1.0 g / μm.

The piercing strength per unit thickness of the polyolefin microporous film is determined by performing a needle penetration test (needle: radius of curvature of the tip 0.5 mm, piercing speed: 320 mm / min) and measuring the maximum piercing load (g). The load is calculated by dividing by the film thickness (μm) of the polyolefin microporous film.

[Water contact angle]
When the polyolefin microporous membrane of the present disclosure is a hydrophilic polyolefin microporous membrane, the contact angle of water 1 second after dropping is 0 to 90 degrees on at least one surface. When the polyolefin microporous film of the present disclosure is a hydrophilic polyolefin microporous film, it is preferable that the contact angle of water 1 second after dropping is 0 to 90 degrees on both sides. The contact angle of water on the surface of the hydrophilic polyolefin microporous membrane 1 second after dropping may be selected depending on the application, for example, 1 degree to 80 degrees, 3 degrees to 70 degrees, 5 degrees to 5 degrees. It is 60 degrees.

With respect to the surface of the microporous polyolefin membrane of the present disclosure, the contact angle of water 1 second after dropping is a value measured by the following measuring method.
In an atmosphere with a temperature of 24 ° C. and a relative humidity of 60%, 1 μL of water droplets are dropped on the surface of the polyolefin microporous film with a syringe, and the static contact angle of water 1 second after the droplets is measured using a fully automatic contact angle meter. Measure by the / 2 method.

[Polyolefin]
The polyolefin contained in the polyolefin microporous film of the present disclosure is not particularly limited, and examples thereof include polyethylene, polypropylene, polybutylene, polymethylpentene, and a copolymer of polypropylene and polyethylene. Among these, polyethylene is preferable, and high-density polyethylene, a mixture of high-density polyethylene and ultra-high molecular weight polyethylene, and the like are preferable. As the polyolefin microporous membrane, a polyethylene microporous membrane containing only polyethylene is preferable.

The microporous polyolefin film of the present disclosure includes a polyolefin composition (in the present disclosure, it means a mixture of polyolefins containing two or more kinds of polyolefins, and when the contained polyolefin is only polyethylene, it is referred to as a polyethylene composition). Is preferable. The polyolefin composition has the effect of forming a network structure with fibrillation during stretching and increasing the porosity of the polyolefin microporous film.

As the polyolefin composition, a polyolefin composition containing ultra-high molecular weight polyethylene having a weight average molecular weight of 9 × 105 or more in an amount of ³ % by mass to 15% by mass with respect to the total amount of polyolefin is preferable, and 5% by mass to 10% by mass. A polyolefin composition containing% is more preferable, and a polyolefin composition containing 5% by mass to 8% by mass is further preferable.

The polyolefin composition consists of ultra-high molecular weight polyethylene having a weight average molecular weight of ^{9 × 105 or more, and a weight average molecular weight of 2 × 10 5 to} 8 × ¹⁰⁵ and a density of 0.92 g / cm ³ to 0.96 g / cm. The high-density polyethylene of ³ is a polyolefin composition mixed at a mass ratio of 3:97 to 15:85 (more preferably 5:95 to 10:90, still more preferably 5:95 to 8:92). Is preferable.

The polyolefin composition preferably has a weight average molecular weight of 2 × 10 ⁵ to 2 × 10 ⁶ as a whole.

The weight average molecular weight of the polyolefins constituting the polyolefin microporous membrane of the present disclosure is determined by heating and dissolving the polyolefin microporous membrane in o-dichlorobenzene and performing gel permeation chromatography (system: Alliance GPC 2000 type manufactured by Waters, column: GMH6). -HT and GMH6-HTL), obtained by measuring under the conditions of a column temperature of 135 ° C. and a flow velocity of 1.0 mL / min. Molecular weight monodisperse polystyrene (manufactured by Tosoh Corporation) is used for molecular weight calibration.

[Method for producing microporous polyolefin membrane]
The polyolefin microporous membrane of the present disclosure can be produced, for example, by a production method including the following steps (I) to (IV).

Step (I): A step of preparing a solution containing the polyolefin composition and a volatile solvent having a boiling point of less than 210 ° C. at atmospheric pressure.
Step (II): A step of melt-kneading the solution, extruding the obtained melt-kneaded product from a die, and cooling and solidifying 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 (secondary stretching) the second gel-like molded product in at least one direction.

By controlling the conditions of steps (I) to (IV), it is possible to produce a polyolefin microporous membrane having a porous structure with excellent isotropic properties and excellent isotropic mass transfer. Become.

Step (I) is a step of preparing a solution containing the polyolefin composition and a volatile solvent having a boiling point of less than 210 ° C. at atmospheric pressure. The solution is preferably a thermoreversible sol-gel solution, and the polyolefin composition is dissolved by heating in a solvent to form a sol to prepare a thermoreversible sol-gel solution. The volatile solvent having a boiling point of less than 210 ° C. at atmospheric pressure is not particularly limited as long as it can sufficiently dissolve polyolefin. Examples of the volatile solvent include tetralin (206 ° C. to 208 ° C.), ethylene glycol (197.3 ° C.), decalin (decahydronaphthalene, 187 ° C. to 196 ° C.), toluene (110.6 ° C.), and xylene. (138 ° C to 144 ° C), diethyltriamine (107 ° C), ethylenediamine (116 ° C), dimethyl sulfoxide (189 ° C), hexane (69 ° C) and the like, with decalin or xylene being preferred (the temperature in parentheses is It is the boiling point at atmospheric pressure.) The volatile solvent may be used alone or in combination of two or more.

The polyolefin composition used in the step (I) (in the present disclosure, means a mixture of polyolefins containing two or more kinds of polyolefins, and when the polyolefin contained is only polyethylene, it is referred to as a polyethylene composition) contains polyethylene. It is preferable, and it is more preferable that it is a polyethylene composition.

The solution prepared in the step (I) preferably has a polyolefin composition concentration of 10% by mass to 40% by mass, preferably 15% by mass, from the viewpoint of controlling the isotropic structure of the porous structure of the polyolefin microporous membrane. More preferably, it is in the amount of ~ 35% by mass. When the concentration of the polyolefin composition is 10% by mass or more, the occurrence of cutting can be suppressed in the film forming process of the polyolefin microporous film, the mechanical strength of the polyolefin microporous film is increased, and the handleability is improved. When the concentration of the polyolefin composition is 40% by mass or less, pores of the polyolefin microporous film are likely to be formed.

Step (II) is a step of melt-kneading the solution prepared in step (I), extruding the obtained melt-kneaded product from a die, and cooling and solidifying to obtain a first gel-like molded product. In step (II), for example, the polyolefin composition is extruded from a die in a temperature range of melting point to melting point + 65 ° C. to obtain an extruded product, and then the extruded product is cooled to obtain a first gel-like molded product. The first gel-like molded product is preferably shaped into a sheet. Cooling may be performed by immersion in water or an organic solvent, by contact with a cooled metal roll, and generally by immersion in the volatile solvent used in step (I). Will be done.

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 of the step (III) is preferably biaxial stretching, and 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 simultaneously performed. The stretching ratio of the primary stretching (the product of the longitudinal stretching ratio and the transverse stretching ratio) is preferably 1.1 to 3 times, and the temperature at the time of stretching, from the viewpoint of controlling the isotropic structure of the porous structure of the polyolefin microporous membrane. Is preferably 75 ° C. or lower. The drying step of the step (III) is carried out without particular limitation as long as the temperature at which the second gel-like molded product is not deformed, but it is preferably carried out at 60 ° C. or lower.

The stretching step and the drying step of the step (III) may be performed simultaneously or stepwise. For example, the primary stretching may be performed while pre-drying, and then the main drying may be performed, or the primary stretching may be performed between the pre-drying and the main drying. The primary stretching can also be performed in a state where drying is controlled and the solvent remains in a suitable state.

Step (IV) is a step of stretching (secondary stretching) the second gel-like molded product in at least one direction. The stretching step of step (IV) is preferably biaxial stretching. In the stretching step of step (IV), longitudinal stretching and transverse stretching are carried out separately; sequential biaxial stretching; longitudinal stretching and transverse stretching are carried out at the same time; simultaneous biaxial stretching; A step of stretching in the vertical direction and a step of stretching in the horizontal direction a plurality of times; a step of sequentially biaxially stretching and then further stretching once or a plurality of times in the vertical direction and / or the horizontal direction;

The draw ratio of the secondary stretch (the product of the longitudinal draw ratio and the transverse draw ratio) is preferably 2 to 25 times, more preferably 2 to 25 times, from the viewpoint of controlling the isotropic structure of the porous structure of the polyolefin microporous membrane. It is 5 to 20 times, more preferably 8 to 15 times. The stretching temperature of the secondary stretching is preferably 90 ° C. to 135 ° C., more preferably 90 ° C. to 125 ° C. from the viewpoint of controlling the isotropic structure of the porous structure of the polyolefin microporous membrane.

The heat fixing treatment may be performed after the step (IV). The heat fixing temperature is preferably 120 ° C. to 150 ° C., more preferably 125 ° C. to 140 ° C. from the viewpoint of controlling the isotropic structure of the porous structure of the polyolefin microporous membrane.

After the heat fixing treatment, the solvent remaining on the microporous polyolefin membrane may be further extracted and annealed. The residual solvent extraction treatment is performed, for example, by immersing the sheet after the heat-fixing treatment in a methylene chloride bath to elute the residual solvent in methylene chloride. The microporous polyolefin membrane immersed in the methylene chloride bath is preferably withdrawn from the methylene chloride bath and then dried to remove methylene chloride. The annealing treatment is carried out by transporting the microporous polyolefin membrane on a roller heated to, for example, 100 ° C. to 140 ° C. after the extraction treatment of the residual solvent.

As a method of controlling the bending ratio in the polyolefin microporous membrane within the range of the formulas (1) and (2), the stretching ratio of the secondary stretching (the product of the longitudinal stretching ratio and the transverse stretching ratio) is 2 to 25 times. It can be mentioned that it is in the range of.

As a method of controlling the permeability index in the polyolefin microporous membrane within the range of the formulas (3) and (4), the stretching ratio of the secondary stretching (the product of the longitudinal stretching ratio and the transverse stretching ratio) is 2 to 25 times. Can be mentioned in the range of. The larger the mass ratio of the ultra-high molecular weight polyethylene contained in the polyolefin composition, the smaller the values of _{TX, TY and TZ} tend to be.

[Hydrophilic treatment of microporous polyolefin membrane]
Examples of the treatment method for making the hydrophobic polyolefin microporous film hydrophilic include a method of applying a hydrophilic material to at least one of the membrane surface and the pore inner surface of the hydrophobic polyolefin microporous film, or a method of imparting a hydrophilic material to the hydrophobic polyolefin microporous film. Examples thereof include a method of physically hydrophilizing at least one of the film surface and the inner surface of the pores.

Specific examples of the method of applying the hydrophilic material to at least one of the surface of the hydrophobic polyolefin microporous film and the inner surface of the pores include coating of a surfactant or a hydrophilic material and graft polymerization of a hydrophilic monomer. Can be mentioned.

The surfactant that hydrophilizes the hydrophobic polyolefin microporous film may be any of a cationic surfactant, an anionic surfactant, an amphoteric ionic surfactant, and a nonionic surfactant. Examples of the cationic surfactant include higher amine halides, alkylpyridinium halides, quaternary ammonium salts and the like. Anionic surfactants include higher fatty acid alkali salts, polyoxyethylene alkyl ether sulfonic acid ester salts, polyoxyethylene alkyl ether phosphonates, alkyl sulfates, alkylbenzene sulfates, alkyl sulfonates, and alkylaryl sulfonic acids. Examples thereof include salts and sulfosuccinate salts. Of these, alkylbenzene sulfonate is preferable, and sodium dodecylbenzene sulfonate is particularly preferable. Examples of the zwitterionic surfactant include alkylbetaine-based compounds, imidazoline-based compounds, alkylamine oxides, and bisoxyborate-based compounds. Examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl allyl ethers, glycerin fatty acid esters, polyoxyethylene sorbitan fatty acid esters, sorbitan fatty acid esters and the like. ..

Examples of the hydrophilic material for coating the hydrophobic polyolefin microporous film include cellulose, polyvinyl alcohol, polyethylene-polyvinyl alcohol copolymer, polyurethane, polyacrylamide and the like.

Examples of the hydrophilic monomer graft-polymerized on the surface of the hydrophobic polyolefin microporous film include acrylic acid, methacrylic acid, vinyl alcohol, N-vinyl-2-pyrrolidone, vinyl sulfonic acid and the like.

Specific examples of the method of physically hydrophilizing at least one of the surface of the hydrophobic polyolefin microporous membrane and the inner surface of the pores include plasma treatment, corona discharge treatment, ultraviolet irradiation, and electron beam irradiation. Can be mentioned.

<Use of polyolefin microporous membrane>
The microporous polyolefin membranes of the present disclosure are used, for example, for the purposes of separation, purification, concentration, fractionation, detection and the like of substances dispersed or dissolved in a fluid (ie, gas or liquid). Applications of the hydrophilic composite membrane of the present disclosure include, for example, filters used for gas-liquid separation, water purification, sterilization, seawater desalination, artificial dialysis, pharmaceutical manufacturing, food manufacturing, medical equipment, in-vitro diagnostic agents, in-vitro diagnostic equipment, and the like. ; Chromatography carrier; etc.

The chromatography carrier is the stationary phase of chromatography. Chromatography and chromatographic carriers are known, and any known form may be applied to construct a chromatographic carrier containing the polyolefin microporous membranes of the present disclosure.

As a more specific morphological example of the chromatography carrier containing the polyolefin microporous membrane of the present disclosure, there is a chromatography carrier contained in an immunochromatographic strip. Examples of the form of the strip for an immunochromatography to which the microporous polyolefin membrane of the present disclosure is applied include the following forms.

The polyolefin microporous membrane of the present disclosure and
A detection unit provided on the microporous polyolefin membrane, wherein a detection reagent that specifically binds to a substance to be detected is fixed, and a detection unit.
Strips for immunochromatography, including.

The microporous polyolefin membrane of the present disclosure functions as a chromatography carrier (stationary phase) in the strip for the immunochromatography of the present disclosure. In the immunochromatographic strip of the present disclosure, a liquid sample moves on a chromatography carrier (that is, the polyolefin microporous membrane of the present disclosure), and the substance to be detected contained in the liquid sample is concentrated in the detection unit and visually observed. Or it is detected using a device.

A preferred embodiment of a strip for an immunochromatography is
A sample pad that accepts liquid samples that may contain substances to be detected, and
A conjugate pad containing a labeling substance that specifically binds to the substance to be detected, and
The polyolefin microporous membrane of the present disclosure, to which a detection reagent that specifically binds to the substance to be detected is fixed, is provided.

FIG. 1 shows an example of an embodiment of the strip for an immunochromatography of the present disclosure. The immunochromatographic strip A contains a sample pad 2 for receiving the dropped sample, a conjugate pad 3 containing a labeling substance, and a detection reagent from upstream to downstream in the development direction (direction indicated by the arrow X in FIG. 1). A fixed chromatography carrier 1 and an absorption pad 4 for absorbing an excess sample are fixed on a resin support 5 in this order.

The chromatography carrier 1 includes a polyolefin microporous membrane of the present disclosure and a detection unit 11 provided on the polyolefin microporous membrane. The detection unit 11 is a region in which a detection reagent that specifically binds to the substance to be detected is fixed. The polyolefin microporous membrane of the present disclosure is preferably used as the chromatography carrier 1 after being lined with a film.

The chromatography carrier 1 contains the polyolefin microporous membrane of the present disclosure. In an example of the chromatography carrier 1, the TD direction of the microporous polyolefin membrane of the present disclosure and the development direction of the sample (the direction indicated by the arrow X in FIG. 1) coincide with each other. In another example of the chromatography carrier 1, the MD direction of the microporous polyolefin membrane of the present disclosure and the development direction of the sample (the direction indicated by the arrow X in FIG. 1) coincide with each other.

As shown in FIG. 1, an example of the detection unit 11 is formed linearly in a direction orthogonal to the development direction at an arbitrary position of the polyolefin microporous film. The detection unit 11 may be formed in the shape of a circular spot, a number, a letter, a symbol (for example, +, −) or the like at an arbitrary position of the polyolefin microporous film.

The chromatography carrier 1 may further include a control unit, which is a region in which a control substance that specifically binds to the labeling substance is fixed, downstream of the detection unit 11. When the chromatography carrier 1 has a control unit downstream of the detection unit 11, when the sample moves to the control unit after passing through the detection unit 11, the labeling substance (that is, the substance to be detected) that is not captured by the detection unit 11 is bound. The labeling substance is concentrated in the control section by specifically binding the labeling substance) to the control substance. As a result, it is possible to confirm that the sample has moved to the control unit visually or by using an appropriate device, and it is possible to grasp the completion of the inspection.

The strip for the immunochromatography is known, and any known form may be applied to form the strip A for the immunochromatography. The material of each member contained in the immunochromatographic strip A, the substance to be inspected in the immunochromatographic strip A, the sample containing the detected substance, the detection reagent fixed on the chromatography carrier 1 and the control substance, and the conju. Any known form may be applied to the labeling substance contained in the gate pad 3.

When the medium constituting the sample containing the substance to be detected is an aqueous medium, the polyolefin microporous membrane of the present disclosure provided in the immunochromatographic strip A is preferably a hydrophilic polyolefin microporous membrane. When the hydrophilic polyolefin microporous membrane of the present disclosure constitutes the immunochromatographic strip A, the surface of the hydrophilic polyolefin microporous membrane in which the contact angle of water 1 second after dropping is 0 to 90 degrees is the substance to be detected. It becomes the surface on the side that receives the liquid sample that may contain.

The strip for the immunochromatography of the present disclosure has excellent inspection accuracy. The mechanism is presumed as follows.
Generally, the detection unit is provided on a part of the chromatography carrier by applying the liquid composition containing the detection reagent to the chromatography carrier. At this time, in the conventional polyolefin microporous membrane, the liquid composition is more likely to flow in the plane direction than in the thickness direction, and as a result, the area of the detection unit is expanded and the concentration of the detection reagent contained in the detection unit is an expected value. Will be lower than.
On the other hand, in the polyolefin microporous membrane of the present disclosure, which has excellent isotropic mass transfer, the liquid composition containing the detection reagent flows in the thickness direction as well as in the plane direction, so that the area of the detection portion is expanded. It is suppressed and the concentration of the detection reagent contained in the detection unit becomes close to the expected value. Since the concentration of the detection reagent in the detection unit formed on the microporous polyolefin membrane of the present disclosure is close to the expected value, the strip for the immunochromatography of the present disclosure is excellent in inspection accuracy.

The strip for the immunochromatography of the present disclosure has a short time required to complete the examination. The mechanism is presumed as follows.
Since the detection unit is formed with a depth in the thickness direction of the chromatography carrier, the substance to be detected must be a chromatographic carrier in order to saturate the specific bond between the detection reagent contained in the detection unit and the substance to be detected. It is necessary to reach the detection part over the entire thickness direction.
However, in the conventional microporous polyolefin membrane, the mobile phase tends to flow in the plane direction as compared with the thickness direction, and it takes time for the mobile phase to spread in the thickness direction. Therefore, the substance to be detected spreads over the entire thickness direction. It takes time to reach the detection unit. Therefore, in the conventional polyolefin microporous membrane, it takes time to saturate the specific bond between the detection reagent contained in the detection unit and the substance to be detected, and the time required to complete the inspection becomes long.
On the other hand, in the polyolefin microporous membrane of the present disclosure having excellent isotropic mass transfer, the mobile phase flows in the thickness direction as well as in the plane direction, so that the substance to be detected reaches the detection portion over the entire thickness direction. Time is reduced. Therefore, in the microporous polyolefin membrane of the present disclosure, the time for which the specific bond between the detection reagent contained in the detection unit and the substance to be detected is saturated is shortened, and the time required for completing the inspection is shortened.

The polyolefin microporous membrane of the present disclosure will be described in more detail with reference to Examples below. The materials, amounts used, proportions, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present disclosure. Therefore, the scope of the polyolefin microporous membranes of the present disclosure should not be construed as limiting by the specific examples set forth below.

<Preparation of microporous polyolefin membrane>
[Example 1]
2. 2.5 parts by mass of ultra-high molecular weight polyethylene (hereinafter referred to as "UHMWPE") having a weight average molecular weight of 4.6 million and high-density polyethylene (hereinafter referred to as "HDPE") having a weight average molecular weight of 560,000 and a density of 950 kg / m ³ . A polyethylene composition mixed with 5 parts by weight was prepared. A polyethylene solution was prepared by mixing the polyethylene composition and decalin so that the polymer concentration was 25% by mass.

The above polyethylene solution was extruded from a die into a sheet at a temperature of 147 ° C., and then the extruded product was cooled in a water bath having a water temperature of 20 ° C. to obtain a first gel-like sheet.

The first gel-like sheet was pre-dried in a temperature atmosphere of 70 ° C. for 10 minutes, then primary stretched 1.1 times in the MD direction, and then the main drying was performed in a temperature atmosphere of 57 ° C. for 5 minutes. After a minute, a second gel sheet (base tape) was obtained (the residual amount of the solvent in the second gel sheet was less than 1%). Next, as secondary stretching, the second gel-like sheet (base tape) was stretched in the MD direction at a temperature of 90 ° C. at a magnification of 2 times, then in the TD direction at a temperature of 130 ° C. at a magnification of 5 times, and then. Immediately, heat treatment (heat fixing) was performed at 140 ° C.

The sheet after the heat fixing treatment was continuously immersed in a methylene chloride bath divided into two tanks for 30 seconds each to extract decalin in the sheet. After the sheet was carried out from the methylene chloride bath, methylene chloride was dried and removed in a temperature atmosphere of 40 ° C., and annealing treatment was performed while transporting the sheet on a roller heated to 120 ° C. In this way, the polyethylene microporous membrane according to the present embodiment was obtained.

Both sides of the above polyethylene microporous membrane were subjected to plasma treatment (AP-300 manufactured by Nordson MARCH: output 150 W, treatment pressure 400 mTorr, gas flow rate 160 sccm, treatment time 135 seconds). In this way, the hydrophilic polyethylene microporous membrane according to the present embodiment was obtained.

A PET film with an adhesive was attached to one side of the above-mentioned hydrophilic polyethylene microporous film to obtain a laminate.

[Examples 2 to 4, Comparative Examples 1 to 2]
A polyethylene microporous membrane, a hydrophilic polyethylene microporous membrane, and a laminate were prepared in the same manner as in Example 1 except that the composition of the polyethylene solution or the manufacturing process of the microporous membrane was changed as shown in Table 1. In Examples 3 and 4, the PET film was attached to the surface of the polyethylene microporous membrane on the side not subjected to the plasma treatment.

<Measuring method of physical properties of polyolefin microporous membrane>
The following measurements were carried out using the polyethylene microporous membranes (that is, hydrophilic polyethylene microporous membranes) after the plasma treatment in Examples 1 to 4 or Comparative Examples 1 and 2 as samples. Table 2 shows the physical characteristics of each polyethylene microporous membrane.

[Film thickness]
The film thickness of the polyolefin microporous film was determined by measuring 20 points with a contact-type film thickness meter (manufactured by Mitutoyo Co., Ltd.) and averaging them. As the contact terminal, a columnar terminal having a bottom surface of 0.5 cm in diameter was used. The measured pressure was 0.1 N.

[Curving rate and transparency index]
A stack of two double-sided tapes is used as a spacer and adhesive, fixed on a polyimide film with a width of about 1 mm, and then a microporous polyolefin film cut out in the MD direction of about 10 mm and the TD direction of about 1 mm is bridged over it. It was fixed in the form of. This sample was fixed to the sample table of the X-ray CT apparatus with wax and used for measurement. The specifications of the X-ray CT were as follows.
X-ray CT device: High-resolution 3DX-ray microscope manufactured by Rigaku, trade name "nano3DX"
X-ray source: Cu, 8.0 keV
X-ray camera: L0270
X-ray tube voltage / tube current: 40kV-30mA
CT imaging range: 0 ° to 180 °

Based on the three-dimensional image obtained from X-ray CT, the curvature ratio (τ _X , τ _Y , τ _Z ) and the permeability index ( _TX , T) of the polyolefin microporous film by the above-mentioned image analysis and simulation _Y , T _Z ) was obtained, and τ _X / τ _Z , τ _Y / τ _Z , _{TX / T Z, and T Y / T Z} were calculated. τ _Z is the curving ratio in the thickness direction, τ _X is the curving ratio in the TD direction, and τ _Y is the curving ratio in the MD direction. _TZ is a transparency index in the thickness direction, _TX is a transparency index in the TD direction, and _TY is a transparency index in the MD direction.

2A to 2E show cross-sectional images obtained from X-ray CT of the polyolefin microporous membranes of Examples 1 to 3 and Comparative Examples 1 and 2. In FIGS. 2A to 2E, X is the TD direction, Y is the MD direction, and Z is the thickness direction. The white straight lines in each image of FIGS. 2A to E are scale bars, the scale bar in the image in the XY direction indicates 50 μm, the scale bar in the image in the XZ direction indicates 20 μm, and the scale in the image in the YZ direction. The bar indicates 20 μm.

[Bubble point pressure]
A microporous polyolefin film was cut into a circle with a diameter of 48 mm, immersed in ethanol, and according to JIS K3832: 1990, however, the liquid temperature during the test was changed to 24 ± 2 ° C., the measurement was started from an applied pressure of 0 MPa, and the step-up speed was increased. The bubble point test was performed while boosting the pressure at 2 kPa / sec, and the bubble point pressure was determined.

[Porosity]
The porosity ε (%) of the polyolefin microporous membrane was calculated by the following formula.
ε = {1- (Wa / xa + Wb / xb + Wc / xc + ... + Wn / xn) / t} × 100
Here, the constituent materials are a, b, c, ..., N, the masses of the constituent materials are Wa, Wb, Wc, ..., Wn (g / cm ² ), respectively, and the true densities of the constituent materials are xa, respectively. , Xb, xc, ..., Xn (g / cm ³ ), and the film thickness is t (cm).

[Gare value]
According to JIS P8117: 2009, the air permeation time (seconds / 100 mL) of a polyolefin microporous film having an area of 642 mm ² was measured, and the air permeation time was divided by the film thickness (μm) of the polyolefin microporous film to per 1 μm of thickness. The air permeation time (seconds / 100 mL · μm) was determined.

[Ethanol flow rate]
The microporous polyolefin membrane was cut out in a direction of 10 cm in the MD direction and 10 cm in the TD direction, immersed in ethanol, withdrawn from ethanol, and dried at room temperature. The dried polyolefin microporous membrane was set in a stainless steel circular liquid permeable cell having a liquid permeable area of 17.34 cm ² . After wetting the microporous polyolefin membrane on the liquid-permeable cell with a small amount (about 0.5 mL) of ethanol, 100 mL of ethanol is permeated with a differential pressure of 92 kPa to 95 kPa, and the time required for 100 mL of ethanol to permeate (sec). ) Was measured. The measurement was performed in a temperature atmosphere at room temperature of 24 ° C. The measurement conditions and the measured values are converted into units to obtain the ethanol flow rate (mL / (min · cm ² · MPa)), and the ethanol flow rate and the previously measured film thickness (μm) of the polyolefin microporous film are determined. Multiplied.

[Water contact angle]
The contact angle of water 1 second after dropping on the surface of the polyolefin microporous film was measured using a fully automatic contact angle meter DMo-701FE manufactured by Kyowa Interface Science Co., Ltd. and analysis software FAMAS (interFAce Measurement and Analysis System). .. In an atmosphere of normal pressure in the air, a temperature of 24 ° C., and a relative humidity of 60%, 1 μL of water (ion-exchanged water) was dropped onto the polyolefin microporous membrane, and the static contact angle 1 second after the dropping was measured. A syringe equipped with a SUS (stainless steel) 22G needle was used to form the water droplets. For the polyolefin microporous membranes of Examples 3 and 4, the contact angle of water was measured on the surface on the side subjected to the plasma treatment.

[Puncture strength]
A needle penetration test (needle: tip curvature radius 0.5 mm, piercing speed: 320 mm / min) was performed using a Tensilon universal material tester (RTE-1210) to measure the maximum piercing load (g), and the maximum piercing load was measured. Was divided by the film thickness (μm) of the polyolefin microporous film to obtain the piercing load (g / μm) per 1 μm of thickness.

<Preparation of strips for immunochromatography>
An immunochromatography strip A for an immunochromatography shown in FIG. 1 using the hydrophilic polyethylene microporous membranes of Examples 1 to 4 or Comparative Examples 1 and 2 and using hCG (human chorionic gonadotropin) as a substance to be detected. The strip was prepared according to the following procedure.

(1) Preparation of Chromatography Carrier 1 A laminate of a hydrophilic polyethylene microporous film and a PET film is cut into a rectangle 150 mm in the MD direction and 25 mm in the TD direction according to the MD direction and the TD direction of the hydrophilic polyethylene microporous film. rice field. Phosphate buffer (pH 7.2) containing 0.5 mg / mL anti-hCG-α subunit antibody (mouse monoclonal antibody) was applied to the surface of the cut-out laminate on the hydrophilic polyethylene microporous membrane side, one length. It was applied linearly at a position 8 mm from the side in parallel with the long side (application amount was 1 μL / cm). Then, it was dried in an atmosphere of a temperature of 50 ° C. for 30 minutes to form a detection unit 11 on a hydrophilic polyethylene microporous membrane to obtain a chromatography carrier 1.

(2) Preparation of Labeling Substance Dispersion Solution Anti-hCG was added to 10 mL of a dispersion in which a colloidal gold (labeled portion) having a particle diameter of 40 nm was diluted with a 50 mM KH ₂ PO ₄ buffer solution (pH 7.0) to a concentration of 60 μg / mL. 1 mL of the antibody (mouse monoclonal antibody) (binding portion) was added, and the mixture was allowed to stand at room temperature for 10 minutes. Then, 0.5 mL of an aqueous solution of 1% by mass polyethylene glycol (PEG, weight average molecular weight 20,000) was added to a dispersion containing gold colloid and an anti-hCG antibody, and the mixture was stirred, and then 10% by mass of BSA (bovine serum albumin) was added. ) Was added, and the mixture was further stirred. Then, centrifugation was performed for 15 minutes at a centrifugal acceleration of 7,000 G, and the supernatant was removed. Next, a 20 mM Tris-hydrochloric acid buffer containing 0.05% by mass of PEG (weight average molecular weight 20,000), 0.009% by mass of NaCl, 1% by mass of BSA and 0.095% by mass of NaN ₃ in the precipitate. A solution (Tris-HCl, pH 8.2) was added, and a labeling substance (anti-hCG antibody labeled with gold colloid) was dispersed to obtain a labeling substance dispersion.

(3) Preparation of Conjugate Pad 3 Tris-hydrochloric acid buffer solution containing 0.05% by mass of PEG (weight average molecular weight 20,000) and 3.5% by mass of sucrose in 0.7 mL of the labeling substance dispersion prepared above. (Tris-HCl, pH 8.2) was added in an amount of 2.1 mL and stirred to obtain a coating solution. The coating liquid was evenly applied to a 150 mm × 8 mm × 400 μm glass fiber pad (manufactured by Ahlstrom) and then dried in a vacuum dryer to obtain a conjugate pad 3.

(4) Preparation of Sample Pad 2 0.6 mL of Tris-hydrochloric acid buffer (Tris-HCl, pH 8.2) was evenly applied to a 150 mm × 18 mm × 340 μm cellulose pad (manufactured by Ahlstrom), and then the temperature was 50 ° C. Was dried for 1 hour to obtain a sample pad 2.

(5) Preparation of Absorption Pad 4 As the absorption pad 4, a filter paper (manufactured by Lohmann) having a size of 150 mm × 20 mm was prepared.

(6) Preparation of Strip A for Lateral Chromatography A chromatographic carrier 1, a conjugate pad 3, a sample pad 2, and an absorption pad 4 are placed on a support 5 (backing sheet manufactured by Lohmann, 150 mm × 60 mm) coated with an adhesive on one side. Was bonded to obtain a composite sheet. At that time, the overlapping width of the sample pad 2 and the conjugate pad 3 is 4 mm, the overlapping width of the conjugate pad 3 and the chromatography carrier 1 is 2 mm, and the overlapping width of the chromatography carrier 1 and the absorption pad 4 is 5 mm. The detection unit 11 of 1 is made closer to the absorption pad 4 than the conjugate pad 3. The entire composite sheet is cut in the length direction every 5 mm width, and a strip A for an immunochromatography (total length 60 mm, width 5 mm in the developing direction. The TD direction of the hydrophilic polyethylene microporous membrane is the developing direction of the sample). Obtained.

<Performance evaluation of strips for immunochromatography>
The following performance evaluation test was performed in an atmosphere having a temperature of 24 ° C. and a relative humidity of 60%. Table 2 shows the evaluation results of strip A for the immunochromatography.

[Saturation time]
A sample was prepared by diluting the hCG antigen (substance to be detected) with a phosphate buffer solution containing 1% by mass of BSA and 0.095% by mass of NaN ₃ so as to be 16.7 nkat. An LED (light emitting diode) having an emission peak wavelength of around 520 nm is developed by dropping 100 μL of a sample onto the sample pad 2 of the strip A for an immunochromatography and using an immunochromatographic reader (manufactured by Hamamatsu Photonics Co., Ltd., model number C10066-10). Was used as a light source, and the absorbance in the detection unit 11 was measured over time. Starting from the time when the sample was dropped on the sample pad 2, the time until the color development (red) of the detection unit 11 was saturated (referred to as the saturation time) was measured and classified into the following three stages. FIG. 3 shows the time course of the absorbance in Example 2 and Comparative Example 1.

A: Saturation time is less than 15 minutes.
B: Saturation time is 15 minutes or more and less than 30 minutes.
C: Saturation time is 30 minutes or more.

[Clarity of color development in the detector]
Simultaneously with the measurement of the saturation time, the clarity of the color development (red) of the detection unit 11 was visually determined and classified into the following three stages.

A: A red line can be clearly confirmed on the detection unit.
B: A red line can be confirmed in the detection unit.
C: A red line can be seen in the detector, but it is unclear.

A: Strip for immunochromatography X: Development direction 1: Chromatography carrier 2: Sample pad 3: Conjugate pad 4: Absorption pad 5: Support 11: Detection unit

Claims (12)

A microporous polyolefin membrane having a film thickness of 1 μm to 400 μm and satisfying the following formulas (1) and (2).
Equation (1): 0.7 ≤ τ _X / τ _Z ≤ 1.5
Equation (2): 0.7 ≤ τ _Y / τ _Z ≤ 1.5
τ _X : Curvature ratio in the first direction along the first surface of the polyolefin microporous membrane.
τ _Y : Curvature ratio in the second direction along the first plane of the polyolefin microporous membrane and orthogonal to the first direction.
τ _Z : Curvature ratio in the thickness direction of the polyolefin microporous membrane. A microporous polyolefin membrane having a film thickness of 1 μm to 400 μm and satisfying the following formulas (3) and (4).
Equation (3): 0.5 ≤ _TX / _TZ ≤ 2.0
Equation (4): 0.5 ≤ _TY / _TZ ≤ 2.0
_TX : Permeability index in the first direction along the first surface of the polyolefin microporous membrane.
_TY : Permeability index in the second direction along the first surface of the polyolefin microporous membrane and orthogonal to the first direction.
_TZ : Permeability index in the thickness direction of the polyolefin microporous membrane. The polyolefin microporous membrane according to claim 1 or 2, wherein the bubble point pressure is 0.001 MPa or more and less than 0.1 MPa. The polyolefin according to any one of claims 1 to 3, wherein the value obtained by multiplying the ethanol flow rate (mL / (min · cm ² · MPa)) and the film thickness (μm) is 50,000 to 500,000. Microporous membrane. The microporous polyolefin membrane according to any one of claims 1 to 4, wherein the galley value per unit thickness is 0.0005 seconds / 100 mL · μm to 0.1 seconds / 100 mL · μm. The polyolefin microporous membrane according to any one of claims 1 to 5, wherein the porosity is 70% to 95%. The micropolyolefin according to any one of claims 1 to 6, which is a hydrophilic polyolefin microporous film and has a contact angle of water of 0 to 90 degrees after 1 second of dropping on at least one surface. Porous membrane. The polyolefin microporous membrane according to claim 7, wherein the hydrophilic polyolefin microporous membrane has a hydrophilic material on at least one of the membrane surface and the inner surface of the pores. The polyolefin microporous according to claim 7 or 8, wherein the hydrophilic polyolefin microporous membrane is a polyolefin microporous membrane in which at least one of the membrane surface and the inner surface of the pores is physically hydrophilized. Porous membrane. The filter containing the polyolefin microporous membrane according to any one of claims 1 to 9. A chromatography carrier comprising the polyolefin microporous membrane according to any one of claims 1 to 9. The polyolefin microporous membrane according to any one of claims 1 to 9.
A detection unit provided on the microporous polyolefin membrane, wherein a detection reagent that specifically binds to a substance to be detected is fixed, and a detection unit.
Strips for immunochromatography, including.

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