KR20210055091A - Polyolefin microporous membrane, filter, chromatography carrier, and immunochromatographic strip - Google Patents

Abstract

A polyolefin microporous membrane having a film thickness of 1 µm to 400 µm and satisfying formulas (1) and (2) or satisfying formulas (3) and (4).
Equation (1): 0.7≤τ _X /τ _{Z ≤1.5}
Equation (2): 0.7≤τ _Y /τ _{Z ≤1.5}
τ _X : the curvature rate in the first direction along the surface of the polyolefin microporous membrane, τ _Y : the curvature rate in the second direction along the surface of the _{polyolefin microporous membrane, τ Z} : the polyolefin microporous membrane The curvature rate in the thickness direction.
Equation (3): 0.5≤T _X /T _{Z ≤2.0}
Equation (4): 0.5≤T _Y /T _{Z ≤2.0}
T _X : Permeability index in the first direction along the surface of the polyolefin microporous membrane, T _Y : Permeability index in the second direction along the surface of the _{polyolefin microporous membrane, T Z} : In the thickness direction of the polyolefin microporous membrane Permeability indicator.

Description

Polyolefin microporous membrane, filter, chromatography carrier, and immunochromatographic strip

The present invention relates to a polyolefin microporous membrane, a filter, a chromatography carrier, and an immunochromatographic strip.

In Patent Document 1, a modified polyolefin porous membrane having a thickness of 1 to 350 μm, a porosity of 25 to 90%, a bubble point of 1 to 10 kg/cm 2, a water permeability of 1000 liters/hr·m 2 ·atm or more, and a water droplet contact angle of 100° or less on the surface 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 pores of 15 to 50 nm.

Patent Document 3 discloses a polyolefin microporous membrane having a water vapor permeation amount of 4000 to 10,000 g/m 2 /24 hr and a water pressure of 30 kPa or more.

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

Polyolefin microporous membranes are sometimes used as filters, chromatography carriers, etc. for the purpose of separation, purification, or detection of substances. In order to improve the degree or speed of separation or purification of substances, a polyolefin microporous membrane having a small difference in a porous structure in a plane direction and a thickness direction and excellent in isotropy of material transfer is required.

Embodiments of the present disclosure have been made under the above circumstances.

An embodiment of the present disclosure aims to provide a polyolefin microporous membrane excellent in isotropy of mass transfer, and makes it a subject to solve this.

The following aspects are included in the specific means for solving the said subject.

[1] A polyolefin microporous 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 : The curvature rate in the first direction along the first surface of the polyolefin microporous membrane.

τ _Y : The curvature rate in the second direction along the first surface of the polyolefin microporous membrane and perpendicular to the first direction.

τ _Z : The curvature ratio in the thickness direction of the polyolefin microporous membrane.

[2] A polyolefin microporous membrane having a film thickness of 1 µm to 400 µm and satisfying the following formulas (3) and (4).

Equation (3): 0.5≤T _X /T _{Z ≤2.0}

Equation (4): 0.5≤T _Y /T _{Z ≤2.0}

T _X : Permeability index in the first direction along the first surface of the polyolefin microporous membrane.

T _Y : Permeability index in the second direction along the first surface of the polyolefin microporous membrane and perpendicular to the first direction.

T _Z : 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 polyolefin microporous membrane according to any one of [1] to [3], wherein a value obtained by multiplying the ethanol flow rate (mL/(min·cm 2·MPa)) and the film thickness (µm) is 50,000 to 500,000.

[5] The polyolefin microporous membrane according to any one of [1] to [4], wherein the Gurley value per unit thickness is 0.0005 sec/100 mL·µm to 0.1 sec/100 ml·µm.

[6] The polyolefin microporous membrane according to any one of [1] to [5], wherein the porosity is 70% to 95%.

[7] The polyolefin microporous membrane according to any one of [1] to [6], wherein the polyolefin microporous membrane is a hydrophilic polyolefin microporous membrane, and the contact angle of water after 1 second dropping on at least one surface is 0 to 90 degrees.

[8] The polyolefin microporous membrane according to [7], wherein the hydrophilic polyolefin microporous membrane has a hydrophilic material on at least one of the membrane surface and the pore inner surface.

[9] The polyolefin microporous membrane according to [7] or [8], wherein the hydrophilic polyolefin microporous membrane is a polyolefin microporous membrane physically subjected to a hydrophilic treatment on at least one of the membrane surface and the inner surface of the pores.

[10] A filter containing the polyolefin microporous membrane according to any one of [1] to [9].

[11] A chromatography carrier comprising the polyolefin microporous membrane according to any one of [1] to [9].

[12] An immunochromato comprising a polyolefin microporous membrane according to any one of [1] to [9], and a detection unit provided on the polyolefin microporous membrane, wherein a detection unit to which a detection reagent specifically binding to a substance to be detected is fixed. Graph strip.

According to an embodiment of the present disclosure, a polyolefin microporous membrane excellent in isotropic material transfer is provided.

1 is a schematic diagram showing the configuration of an immunochromatographic strip.
2A is a cross-sectional image obtained from X-ray CT of a polyolefin microporous membrane of Example 1. FIG.
2B is a cross-sectional image obtained from X-ray CT of the polyolefin microporous membrane of Example 2. FIG.
2C is a cross-sectional image obtained from X-ray CT of the polyolefin microporous membrane of Example 3. FIG.
2D is a cross-sectional image obtained from X-ray CT of a polyolefin microporous membrane of Comparative Example 1. FIG.
2E is a cross-sectional image obtained from X-ray CT of a polyolefin microporous membrane of Comparative Example 2. FIG.
3 is a graph showing changes over time in absorbance in Example 2 and Comparative Example 1. FIG.

Hereinafter, an embodiment of the invention will be described. These descriptions and examples are illustrative of embodiments and do not limit the scope of the invention. The functional mechanism described in the present disclosure includes an estimate, and the government does not limit the scope of the invention.

In the present disclosure, when an embodiment is described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. In addition, the size of the member in each figure is conceptual, and the relative relationship of the size between members is not limited to this.

In the present disclosure, the numerical range indicated using "-" represents a range including the numerical values described before and after "-" as a lower limit value and an 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 substituted with the upper limit value or the lower limit value of the numerical range described in another stepwise manner. In addition, in the numerical range described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be substituted with a value shown in Examples.

In the present disclosure, the word "step" is included in this term not only as an independent step, but also in the case where the desired purpose of the step is achieved even if it cannot be clearly distinguished from other steps.

In the present disclosure, each component may contain a plurality of types of corresponding substances. When referring to the amount of each component in the composition in the present disclosure, when there are multiple types of substances corresponding to each component in the composition, unless specifically limited, the total amount of the plurality of substances present in the composition it means.

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

<Polyolefin microporous membrane>

The present disclosure provides a polyolefin microporous membrane excellent in isotropic material 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, and has a structure in which these micropores are connected. It refers to a membrane through which liquid is allowed to pass.

The present disclosure discloses a first polyolefin microporous membrane and a second polyolefin microporous membrane as a polyolefin microporous membrane excellent in material transfer isotropy.

The first polyolefin microporous membrane has a thickness of 1 μm to 400 μm, and satisfies the following equations (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 : The curvature rate in the first direction along the first surface of the polyolefin microporous membrane.

τ _Y : The curvature rate in the second direction along the first surface of the polyolefin microporous membrane and perpendicular to the first direction.

τ _Z : The curvature ratio in the thickness direction of the polyolefin microporous membrane.

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

In the present disclosure, the tortuosity is an index indicating how much the flow path through which the fluid flows is detoured for the shortest distance, and the more the flow path is detoured, the larger the curvature rate.

The first polyolefin microporous membrane is excellent in isotropy of mass transfer by satisfying the formulas (1) and (2) at the same time. In the polyolefin microporous membrane, when τ _X / τ _Z or τ _Y / τ _Z is less than 0.7, the degree of bypass of the flow path is too large in the thickness direction, and it is difficult for the fluid to pass in the thickness direction. In the polyolefin microporous membrane, when τ _X / τ _Z or τ _Y / τ _Z exceeds 1.5, the degree of bypass of the flow path is too large in the plane direction, and it is difficult for the fluid to pass in the plane direction.

The first polyolefin microporous membrane preferably satisfies the formula (1'): 0.75 ≤ _{τ X} /τ _Z ≤ 1.3, and the formula (1 ``): 0.8 ≤ τ _X It is more preferable to satisfy /τ _{Z ≤ 1.1.}

First polyolefin microporous membrane is on the superior aspect of the mobile isotropic material, formula _{(2 '): 0.75≤τ Y /} τ Z ≤1.3 is preferable, and expression (2 satisfying''): 0.8≤τ _Y It is more preferable to satisfy /τ _{Z ≤ 1.1.}

The first polyolefin microporous membrane preferably satisfies the formulas (1) and (2') at the same time, and more preferably satisfies the formulas (1) and (2'') at the same time.

The first polyolefin microporous membrane preferably satisfies the formulas (1') and (2) at the same time, more preferably satisfies the formulas (1') and (2') at the same time, and the formula (1') It is more preferable to satisfy and equation (2'') at the same time.

The first polyolefin microporous membrane preferably satisfies the formulas (1") and (2) at the same time, more preferably satisfies the formulas (1") and (2') at the same time, and the formula (1 It is more preferable to satisfy both'') and equation (2'') at the same time.

The value of τ _X is not particularly limited, but 1.2 to 2.0 are preferable, 1.2 to 1.8 are more preferable, and 1.4 to 1.7 are more preferable.

Although _{the value of τ Y} is not particularly limited, 1.2 to 2.0 are preferable, 1.2 to 1.8 are more preferable, and 1.4 to 1.7 are more preferable.

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 still more preferably 1.6 to 1.9.

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

Equation (3): 0.5≤T _X /T _{Z ≤2.0}

Equation (4): 0.5≤T _Y /T _{Z ≤2.0}

T _X : Permeability index in the first direction along the first surface of the polyolefin microporous membrane.

T _Y : Permeability index in the second direction along the first surface of the polyolefin microporous membrane and perpendicular to the first direction.

T _Z : Permeability index in the thickness direction of the polyolefin microporous membrane.

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

In the present disclosure, the permeability index is an index indicating the ease of flow of a fluid with respect to a flow path through which the fluid flows, and a flow path through which the fluid flows easily has a larger permeability index. In the present disclosure, the permeability index is the wetted area derived from the equation of Dalsey-Weissbaha, and the square of the length (µm ² ) is used as a unit.

Dalsey-Weissbach's equation: k=QμL/ΔPA

k: permeability index (㎛ ² )

Q: Outflow per unit time (㎛ ³ /s)

μ: viscosity of fluid (Pa·s)

L: length of flow path (㎛)

ΔP: pressure difference (Pa)

A: Cross-sectional area (㎛ ² )

The 2nd polyolefin microporous membrane is excellent in isotropic property of mass transfer by satisfying the formula (3) and the formula (4) at the same time. In the polyolefin microporous membrane, when T _X /T _Z or T _Y /T _Z is less than 0.5, the fluid flows too much in the thickness direction compared to the surface direction, and it is difficult for the fluid to pass through the surface direction. In the polyolefin microporous membrane, when T _X /T _Z or T _Y /T _Z exceeds 2.0, the fluid flows too much in the surface direction compared to the thickness direction, and it is difficult to pass the fluid in the thickness direction.

Second polyolefin microporous membrane is on the superior aspect of the mobile isotropic material, formula _{(3 '): 0.8≤T X /} T Z ≤2.0 is preferable, and expression (3 satisfying''): 0.9≤T _X It is more preferable to satisfy /T _{Z ≤ 1.9.}

Second polyolefin microporous membrane is on the superior aspect of the mobile isotropic material, formula _{(4 '): 0.75≤T Y /} T Z ≤1.5 is preferable, and expression (4 satisfying a''): 0.8≤T _Y It is more preferable to satisfy /T _Z≦1.1.

The second polyolefin microporous membrane preferably satisfies the formulas (3) and (4') at the same time, and more preferably satisfies the formulas (3) and (4'') at the same time.

The second polyolefin microporous membrane preferably satisfies the formulas (3') and (4) at the same time, more preferably satisfies the formulas (3') and (4') at the same time, and the formula (3') It is more preferable to satisfy the equation (4'') at the same time.

The second polyolefin microporous membrane preferably satisfies the formulas (3'') and (4) at the same time, more preferably satisfies the formulas (3'') and (4') at the same time, and the formula (3 It is more preferable to satisfy both'') and equation (4'') at the same time.

Although _{the value of T X} is not particularly limited, 0.4 to 3.0 are preferable, 0.5 to 2.5 are more preferable, and 1.0 to 2.0 are still more preferable.

Although _{the value of T Y} is not particularly limited, 0.2 to 2.0 are preferable, 0.3 to 1.9 are more preferable, and 0.5 to 1.8 are more preferable.

Although _{the value of T Z} is not particularly limited, 0.2 to 2.0 are preferable, 0.3 to 1.9 are more preferable, and 0.5 to 1.8 are more preferable.

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

Using a polyolefin microporous membrane for X-ray computed tomography (X-ray CT), an X-ray transmission image is imaged while rotating the sample by 0° to 180°, and a three-dimensional image of the internal structure is reconstructed by a computer from the obtained image data. . The reconstructed three-dimensional image is image-converted with image processing software ImageJ, and cross-sectional sequence data of 0.26 mu m/pixel pitch is obtained for each of the three planes (XY plane, XZ plane, and YZ plane). Depending on the scanning direction of the X-ray CT, but if necessary, from the obtained sequence data, the axial direction of the sequence data is converted into ImageJ, the image processing software, so that the Z direction in the three-sided view matches the thickness direction of the polyolefin microporous film. Also, if necessary, a three-sided view is produced with the image processing software ImageJ. The X direction and Y direction of the three-sided view are not particularly limited, but, for example, match the MD direction and the TD direction or the TD direction and the MD direction of the polyolefin microporous membrane, respectively.

Subsequently, data of 300 µm in the X direction and 300 µm in the Y direction are extracted from the obtained sequence data, and data of the length (µm) according to the film thickness of the polyolefin microporous film is extracted in the Z direction. From the viewpoint of increasing the degree of analysis, it is preferable to remove the data of several µm each up and down in the Z direction (for example, 5 µm each up and down) and extract the data of the central portion in the Z direction.

After the sequence data taken out of the above dimensions is introduced into the image analysis software Avizo, it is converted into 0.26 µm/voxel three-dimensional data, and voids are extracted using the software. At that time, it is preferable to remove the noise (for example, as noise due to reflection and scattering when taking an X-ray CT, a dot having a volume of 50 voxel or less is removed). And, using the Pore network analysis function of the image analysis software Avizo, a network is constructed in each of the X-direction, Y-direction, and Z-direction, with the centers of the closest pores in order, and the contact area between the closest pores is determined. Acquired as a parameter. Then, in each of the X-direction, Y-direction, and Z-direction, a simulation in which a fluid flows at a certain amount of outflow per unit time is performed, and the complexity and permeability of the network are analyzed. Among the extracted data, the length in the direction in which the fluid flows is taken as the length of the flow path, and the area of the plane orthogonal to the direction in which the fluid flows is taken 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, the curvature rates τ _X , τ _Y and τ _Z in each of the X, Y and Z directions, and T _X , T _Y and T _{Z as permeability indices in the X, Y and Z directions respectively.} Get The curvature rate is an average value obtained by dividing the length of a network extending from one side to the other side by the shortest distance connecting the starting point and the end point of the network. The permeability index is a coefficient derived from the equation of Dalsey Weisbach. In the equation of Darcy and Weisbach, the coefficient k is obtained by substituting Q for the number of outflows per unit time, μ for the viscosity of the fluid, L for the length of the flow path, ΔP for the pressure difference, and A for the cross-sectional area. .

The first polyolefin microporous membrane and the second polyolefin microporous membrane will be described in more detail. The matters common to the first polyolefin microporous membrane and the second polyolefin microporous membrane will be collectively referred to as the polyolefin microporous membrane 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 not subjected to a hydrophilization treatment, or may be a polyolefin microporous membrane to which hydrophilicity is imparted by a hydrophilization treatment. Details of the method of hydrophilizing the polyolefin microporous membrane will be described later.

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

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

[Film thickness]

The film thickness of the polyolefin microporous membrane of the present disclosure is suitably 1 µm to 400 µm, and may be selected according to the application within the range, for example, 10 µm to 300 µm, 20 µm to 250 µm, and 30 It is from µm to 200 µm, and from 40 µm to 150 µm.

[Bubble point pressure]

The bubble point pressure of the polyolefin microporous membrane of the present disclosure may be selected depending on the application, 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 0.05 MPa.

In the present disclosure, the bubble point pressure of the polyolefin microporous membrane is applied by immersing the polyolefin microporous membrane in ethanol and according to the bubble point test method of JIS K3832:1990, but changing the liquid temperature at the time of the test to 24±2°C. It is a value obtained by performing a bubble point test while increasing the pressure at a pressure increase rate of 2 kPa/sec.

[Ethanol flow rate]

The ethanol flow rate of the polyolefin microporous membrane of the present disclosure may be selected depending on 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 400,000. , 100,000 to 300,000.

In the present disclosure, the ethanol flow rate (mL/(min·cm2·MPa) of the polyolefin microporous membrane) permeates 100 mL of ethanol at a constant differential pressure (kPa) through the polyolefin microporous membrane set in a fluid permeation cell having a constant permeation area (cm 2 ). And, the time required for 100 mL of ethanol to permeate (sec) is measured, and it is calculated in terms of units.

[Gurley Value]

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

[Power]

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

In the present disclosure, the porosity (%) of the polyolefin microporous membrane is determined by the following equation.

Porosity (%)={1-(Wa/xa+Wb/xb+Wc/xc+…+Wn/xn)/t}×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, ..., respectively. , Wn (g/cm2), and the true densities of the constituent materials are xa, xb, xc, ..., respectively. , xn (g/cm 3 ), and the film thickness of the polyolefin microporous membrane is t (cm).

[Average flow pore diameter]

The average flow pore size of the polyolefin microporous membrane of the present disclosure may be selected depending on the application, for example, 0.02 µm to 5 µm, 0.05 µm to 4 µm, and 0.1 µm to 3.5 µm.

The average flow pore diameter of the polyolefin microporous membrane is ASTM E1294-89 using PMI's perm porometer (model: CFP-1200-AEXL) and using PMI's Galwick (surface tension 15.9 dyn/cm) for immersion. It is obtained in accordance with the prescribed half-dry law.

[BET specific surface area]

The BET specific surface area of the polyolefin microporous membrane of the present disclosure may be selected depending on the application, for example, 1 m2/g to 30 m2/g, 2 m2/g to 25 m2/g, and 3 m2/g to It is 20 m2/g.

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

[Dolja (突刺) robbery]

The polyolefin microporous membrane of the present disclosure has a piercing strength per unit thickness of, for example, 0.05 g/µm to 1.5 g/µm, 0.07 g/µm to 1.2 g/µm, and 0.08 g/µm to 1.0 g/µm. to be.

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

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

The contact angle of water 1 second after dropping with respect to the surface of the polyolefin microporous membrane of the present disclosure is a value measured by the following measuring method.

In an atmosphere of a temperature of 24°C and a relative humidity of 60%, a drop of 1 μL is dropped on the surface of the polyolefin microporous membrane with a syringe, and the static contact angle of water 1 second after dropping is measured by the θ/2 method using a fully automatic contact angle meter. .

[Polyolefin]

The polyolefin contained in the polyolefin microporous membrane 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 a high-density polyethylene, a mixture of a high-density polyethylene and an ultra-high molecular weight polyethylene, and the like are suitable. As the polyolefin microporous membrane, a polyethylene microporous membrane in which the polyolefin contained is only polyethylene is suitable.

It is preferable that the polyolefin microporous membrane of the present disclosure contains a polyolefin composition (in the present disclosure, it means a mixture of polyolefins containing two or more polyolefins, and when the polyolefin contained is only polyethylene, it is referred to as a polyethylene composition). . The polyolefin composition has the utility of forming a network structure with fibrillation during stretching, thereby increasing the porosity of the polyolefin microporous membrane.

As the polyolefin composition, a polyolefin composition containing 3% by mass to 15% by mass of ultrahigh molecular weight polyethylene having a weight average molecular weight of 9×10 ⁵ or more with respect to the total amount of the polyolefin is preferable, and a polyolefin composition comprising 5% by mass to 10% by mass This is more preferable, and the polyolefin composition containing 5 mass%-8 mass% is more preferable.

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

As for the polyolefin composition, it is preferable that the weight average molecular weight of the whole polyolefin is 2×10 ⁵ to 2×10 ^6.

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

[Method for producing polyolefin microporous 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 a polyolefin composition and a volatile solvent having a boiling point of less than 210°C in atmospheric pressure.

Step (II): A step of melt-kneading the solution, extruding the obtained melt-kneaded product from a die, cooling and solidifying it to obtain a first gel-like molded product.

Step (III): A step of stretching the first gel-like molded product in at least one direction (primary stretching) and drying the solvent to obtain a second gel-like molded product.

Step (IV): A step of stretching (secondary stretching) the second gel-like molded product in at least one direction.

By controlling the conditions of steps (I) to (IV), it becomes possible to manufacture a polyolefin microporous membrane having a porous structure excellent in isotropy and excellent in isotropy of mass transfer.

Step (I) is a step of preparing a solution containing a polyolefin composition and a volatile solvent having a boiling point of less than 210°C in atmospheric pressure. The solution is preferably a thermoreversible sol-gel solution, and the polyolefin composition is solized by heating and dissolving in a solvent to prepare a thermoreversible sol-gel solution. The volatile solvent having a boiling point at atmospheric pressure of less than 210°C is not particularly limited as long as it is a solvent capable of sufficiently dissolving 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), xylene ( 138°C to 144°C), diethyltriamine (107°C), ethylenediamine (116°C), dimethyl sulfoxide (189°C), hexane (69°C), and the like, and decalin or xylene is preferable ( The temperature in parentheses is the boiling point at atmospheric pressure). The volatile solvents may be used alone or in combination of two or more.

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

The solution prepared in step (I) is preferably 10% by mass to 40% by mass, and 15% by mass to 35% by mass, from the viewpoint of controlling the isotropy of the porous structure of the polyolefin microporous membrane. It is more preferable. When the concentration of the polyolefin composition is 10% by mass or more, it is possible to suppress the occurrence of cutting in the film-forming step of the polyolefin microporous membrane, and the mechanical strength of the polyolefin microporous membrane increases, thereby improving the handling properties. When the concentration of the polyolefin composition is 40% by mass or less, pores in the polyolefin microporous membrane 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, cooling and solidifying to obtain a first gel-like molded product. Step (II) is, for example, extruded from a die in a temperature range of the melting point to +65°C of the polyolefin composition to obtain an extruded product, and then the extruded product is cooled to obtain a first gel-like molded product. It is preferable to shape the 1st gel-like molded article into a sheet shape. Cooling may be performed by immersion in water or an organic solvent, may be performed by contact with a cooled metal roll, or generally by immersion in a volatile solvent used in the step (I).

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, 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 draw ratio of the primary stretching (the product of the longitudinal draw ratio and the transverse draw ratio) is preferably 1.1 to 3 times, and the temperature at the time of stretching is preferably 75°C or less from the viewpoint of controlling the isotropy of the porous structure of the polyolefin microporous membrane. Do. The drying step of the step (III) is carried out without particular limitation as long as the second gel-like molded product is at a temperature at which it does not deform, but 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 may be performed stepwise. For example, primary stretching may be performed while pre-drying, followed by main drying, or primary stretching may be performed between pre-drying and main drying. The primary stretching can be performed even in a state in which 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. As for the extending|stretching process of process (IV), biaxial extension is preferable. The stretching step of step (IV) includes sequential biaxial stretching in which longitudinal stretching and transverse stretching are performed separately; Simultaneous biaxial stretching with simultaneous longitudinal stretching and transverse stretching; Stretching in the transverse direction after stretching in the longitudinal direction a plurality of times; Stretching in the longitudinal direction and stretching in the transverse direction a plurality of times; After successive biaxial stretching, any of the steps of stretching once or more in the longitudinal direction and/or the transverse direction may be employed.

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

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

After the heat setting treatment, extraction treatment and annealing treatment of the solvent remaining in the polyolefin microporous film may be further performed. The extraction treatment of the residual solvent is performed, for example, by immersing the sheet after heat setting treatment in a methylene chloride bath, and eluting the residual solvent in methylene chloride. After the polyolefin microporous membrane immersed in a methylene chloride bath is pulled up from a methylene chloride bath, it is preferable to remove methylene chloride by drying. The annealing treatment is performed by conveying the polyolefin microporous film on a roller heated at, for example, 100°C to 140°C after extraction treatment of the residual solvent.

As a method of controlling the curvature rate in the polyolefin microporous membrane in the range of formulas (1) and (2), the draw ratio of the secondary stretching (the product of the longitudinal draw ratio and the transverse draw ratio) is in the range of 2 to 25 times. What to do with it is mentioned.

As a method of controlling the permeability index in the polyolefin microporous membrane in the range of formulas (3) and (4), the draw ratio of the secondary stretching (the product of the longitudinal draw ratio and the transverse draw ratio) is in the range of 2 to 25 times. What to do with it is mentioned. As the mass ratio of the ultra-high molecular weight polyethylene contained in the polyolefin composition increases, _{the values of T X} , T _Y and T _Z tend to decrease.

[Hydrophilic treatment of polyolefin microporous membrane]

As a treatment method for hydrophilizing the hydrophobic polyolefin microporous membrane, for example, a method of imparting a hydrophilic material to at least one of the membrane surface and the inner surface of the pores of the hydrophobic polyolefin microporous membrane, or the membrane surface and the inner pores of the hydrophobic polyolefin microporous membrane. A method of physically subjecting at least one of the surfaces to a hydrophilic treatment is exemplified.

Specific examples of the method of imparting a hydrophilic material to at least one of the membrane surface and the inner surface of the pores of the hydrophobic polyolefin microporous membrane include coating of a surfactant or a hydrophilic material, and graft polymerization of a hydrophilic monomer.

The surfactant that hydrophilizes the hydrophobic polyolefin microporous membrane 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 halide salts, alkyl pyridinium halide, and quaternary ammonium salts. As anionic surfactants, higher fatty acid alkali salts, polyoxyethylene alkyl ether sulfonic acid ester salts, polyoxyethylene alkyl ether phosphonic acid salts, alkyl sulfates, alkylbenzene sulfates, alkyl sulfonates, alkylarylsulfonic acid salts, sulfosuccinic acid ester salts And the like. Among them, alkylbenzene sulfonate is preferable, and sodium dodecylbenzenesulfonate is particularly preferable. Examples of the amphoteric ionic surfactant include an alkyl betaine compound, an imidazoline compound, an alkylamine oxide, and a bisoxyborate compound. Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl allyl ethers, glycerin fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and sorbitan fatty acid esters. have.

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

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

As a method of physically hydrophilizing at least one of the membrane surface and the inner surface of the pores of the hydrophobic polyolefin microporous membrane, specifically, for example, plasma treatment, corona discharge treatment, ultraviolet irradiation, and electron beam irradiation may be mentioned.

<Use of polyolefin microporous membrane>

The polyolefin microporous membrane of the present disclosure is used for the purpose of separation, purification, concentration, fractionation, detection, etc. of substances dispersed or dissolved in a fluid (ie, gas or liquid). Examples of the use of the hydrophilic composite membrane of the present disclosure include filters used in gas-liquid separation, water purification, sterilization, seawater desalination, artificial dialysis, pharmaceutical manufacturing, food manufacturing, medical devices, in vitro diagnostic drugs, in vitro diagnostic devices, and the like; And a chromatography carrier.

The chromatography carrier is the stationary phase of chromatography. Chromatography and chromatography carriers are known, and all known forms may be applied to constitute a chromatography carrier comprising the polyolefin microporous membrane of the present disclosure.

As a more specific example of the chromatography carrier including the polyolefin microporous membrane of the present disclosure, a chromatography carrier included in an immunochromatographic strip may be mentioned. As an example of the form of a strip for immunochromatography to which the polyolefin microporous membrane of the present disclosure is applied, the following forms may be mentioned.

The polyolefin microporous membrane of the present disclosure, and

As a detection unit provided in the polyolefin microporous membrane, a detection unit in which a detection reagent specifically binding to a substance to be detected is fixed

Immunochromatography strip comprising a.

The polyolefin microporous membrane of the present disclosure functions as a chromatography carrier (fixed phase) in the immunochromatographic strip of the present disclosure. In the immunochromatographic strip of the present disclosure, a liquid sample is moved through a chromatography carrier (i.e., a polyolefin microporous membrane of the present disclosure), and a substance to be detected contained in the liquid sample is concentrated in the detection unit, and visually or It is detected using an instrument.

A preferred embodiment of the immunochromatographic strip is,

A sample pad for accommodating a liquid sample that may contain a substance to be detected,

A conjugate pad containing a labeling substance that specifically binds to the substance to be detected,

A polyolefin microporous membrane of the present disclosure to which a detection reagent specifically binding to the substance to be detected is immobilized is provided.

Fig. 1 shows an example of an embodiment of an immunochromatographic strip according to the present disclosure. The immunochromatographic strip (A) is a sample pad (2) containing the dropped sample from upstream to downstream in the development direction (direction indicated by arrow X in Fig. 1), and a conjugate containing a labeling substance. A pad 3, a chromatography carrier 1 on which a detection reagent is fixed, and an absorption pad 4 for absorbing an extra 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 in the polyolefin microporous membrane. The detection unit 11 is a region in which a detection reagent that specifically binds to a substance to be detected is fixed. It is preferable that the polyolefin microporous membrane of the present disclosure is used as a chromatography carrier (1) after atmospheric processing on the back side with a film is performed.

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 polyolefin microporous membrane of the present disclosure and the development direction of the sample (direction indicated by arrow X in Fig. 1) coincide. In another example of the chromatography carrier 1, the MD direction of the polyolefin microporous membrane of the present disclosure and the development direction of the sample (direction indicated by arrow X in Fig. 1) coincide.

An example of the detection unit 11 is formed in a straight line in a direction orthogonal to the development direction at an arbitrary position of the polyolefin microporous membrane, as shown in FIG. 1. The detection unit 11 may be formed in a shape such as a circular spot, a number, a letter, or a symbol (eg, +, -) at an arbitrary position on the polyolefin microporous membrane.

The chromatography carrier 1 may further include a control unit, which is a region in which a control substance specifically binding to a 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 passes through the detection unit 11 and then moves to the control unit, a labeling substance that is not captured by the detection unit 11 (i.e., a substance to be detected) The labeling substance is concentrated in the control portion by specifically binding to the control substance). Thereby, it is possible to confirm that the sample has moved to the control unit visually or by using a suitable device, and it is possible to grasp the completion of the inspection.

The immunochromatographic strip is known, and all known forms may be applied to form the immunochromatographic strip (A). Materials of each member included in the immunochromatography strip (A), the detection subject to be inspected by the immunochromatography strip (A), a sample containing the detection material, and the chromatography carrier (1) All known forms may be applied to the immobilized detection reagent and control substance, and to the labeling substance contained in the conjugate 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 having a contact angle of water of 0 degrees to 90 degrees after 1 second dropping should contain the substance to be detected. It becomes the side of the side that receives the sample in the liquid phase of the possibility.

The immunochromatographic strip of the present disclosure has excellent inspection accuracy. The mechanism is estimated as follows.

In general, the detection unit is provided on a part of the chromatography carrier by applying a liquid composition containing a 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, as a result, the area of the detection unit is widened, and the concentration of the detection reagent contained in the detection unit is lower than the expected value.

On the other hand, in the polyolefin microporous membrane of the present disclosure having excellent material transfer isotropy, since the liquid composition containing the detection reagent flows in the thickness direction at the same level as the surface direction, the widening of the area of the detection unit is suppressed, and is included in the detection unit. The concentration of the detection reagent becomes a concentration close to the expected value. Since the detection unit formed on the polyolefin microporous membrane of the present disclosure has a concentration of a detection reagent close to an expected value, the immunochromatographic strip of the present disclosure has excellent inspection accuracy.

In the immunochromatographic strip of the present disclosure, the time required to complete the inspection is short. The mechanism is estimated as follows.

Since the detection unit is formed to have a depth in the thickness direction of the chromatography carrier, in order to saturate the specific binding between the detection reagent included in the detection unit and the substance to be detected, the detection unit is Requires to reach.

However, in the conventional polyolefin microporous membrane, the mobile phase tends to flow in the plane direction compared to the thickness direction, and it takes time for the mobile phase to pass in the thickness direction, so it takes time for the substance to be detected to reach the detection unit over the entire thickness direction. Therefore, in the conventional polyolefin microporous membrane, it takes time for the specific binding between the detection reagent contained in the detection unit and the substance to be detected to saturate, and the time required to complete the inspection becomes longer.

On the other hand, in the polyolefin microporous membrane of the present disclosure having excellent material transfer isotropy, since the mobile phase flows in the thickness direction at the same degree as the plane direction, the time for the detection target material to reach the detection unit over the entire thickness direction is shortened. Therefore, in the polyolefin microporous membrane of the present disclosure, the time for saturating the specific binding between the detection reagent contained in the detection unit and the substance to be detected is shortened, and the time required to complete the inspection is shortened.

(Example)

Hereinafter, an example is given, and the polyolefin microporous membrane of the present disclosure will be described in more detail. Materials, usage, ratios, treatment procedures, and the like shown in the following examples can be changed as appropriate, as long as they do not deviate from the spirit of the present disclosure. Therefore, the range of the polyolefin microporous membrane of the present disclosure should not be limitedly interpreted by the specific examples shown below.

<Production of polyolefin microporous membrane>

[Example 1]

A polyethylene composition obtained by mixing 2.5 parts by mass of ultra-high molecular weight polyethylene (hereinafter referred to as ``UHMWPE'') with a weight average molecular weight of 4.6 million and 22.5 parts by mass of high-density polyethylene (hereinafter referred to as ``HDPE'') with a weight average molecular weight of 560,000 and a density of 950 kg/m 3 I prepared. The polyethylene composition and decalin were mixed so that the polymer concentration became 25 mass %, and the polyethylene solution was prepared.

The above-described 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 for 10 minutes in a temperature atmosphere of 70° C., and then, primary stretching was performed in the MD direction by 1.1 times, and then, main drying was performed for 5 minutes in a temperature atmosphere of 57° C., and the second gel-like sheet (base Tape) was obtained (the residual amount of the solvent in the second gel-like sheet was less than 1%). Subsequently, as secondary stretching, a second gel-like sheet (base tape) is stretched in the MD direction at a temperature of 90° C. at twice the magnification, and then stretched in the TD direction at a temperature of 130° C. at a magnification of 5 times, and then heat treated at 140° C. ( Heat setting).

Decalin in the sheet was extracted while the sheet after the heat setting treatment was continuously immersed in a methylene chloride bath divided into two baths for 30 seconds each. After the sheet was taken out from the methylene chloride bath, methylene chloride was dried and removed under a temperature atmosphere of 40°C, and annealing treatment was performed while conveying the roller top heated to 120°C. In this way, a polyethylene microporous membrane according to the present embodiment was obtained.

Plasma treatment (AP-300 manufactured by Nordson MARCH: output 150 W, treatment pressure 400 mTorr, gas flow rate 160 sccm, treatment time 135 seconds) was performed on both surfaces of the above-described polyethylene microporous membrane. In this way, a hydrophilic polyethylene microporous membrane according to the present embodiment was obtained.

A PET film with an adhesive was bonded to one side of the hydrophilic polyethylene microporous membrane described above 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 produced 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 described in Table 1. In Example 3 and Example 4, the PET film was pasted on the side of the polyethylene microporous membrane on the side not subjected to plasma treatment.

[Table 1]

<Method of measuring physical properties of polyolefin microporous membrane>

The following measurement was performed using the polyethylene microporous membrane (that is, hydrophilic polyethylene microporous membrane) after plasma treatment in Examples 1 to 4 or Comparative Examples 1 and 2 as a sample. Table 2 shows the physical properties 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 Corporation), and averaging them. As the contact terminal, a cylindrical terminal with a diameter of 0.5 cm at the bottom was used. The measurement pressure was 0.1N.

[Curvature rate and permeability index]

Using two double-sided tapes as spacers and adhesives, fixing them on a polyimide film with a width of about 1 mm, and then cutting a polyolefin microporous membrane cut into about 10 mm in the MD direction and about 1 mm in the TD direction in the form of a bridge. Fixed as. This sample was fixed to the sample stage of the X-ray CT apparatus using wax, and was used for measurement. The specifications of the X-ray CT were as follows.

X-ray CT device: manufactured by Rigaku Corporation, high-resolution 3DX-ray microscope, brand name "nano3DX"

X-ray source: Cu, 8.0keV

X-ray camera: L0270

X-ray tube voltage and tube current: 40kV-30mA

CT scan range: 0°∼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 (T _X , T _Y , and the polyolefin microporous membrane) were obtained by image analysis and simulation of the technology. T _Z ) was calculated, and τ _X /τ _Z , τ _Y /τ _Z , T _X /T _Z and T _Y / T _Z were calculated. τ _Z is the curvature rate in the thickness direction, τ _X is the curvature rate in the TD direction, and τ _Y is the curvature rate in the MD direction. T _Z is a permeability index in the thickness direction, T _X is a permeability index in the TD direction, and T _Y is a permeability index in the MD direction.

2A to E, cross-sectional images obtained from X-ray CT of the polyolefin microporous membranes of Examples 1 to 3 and Comparative Examples 1 to 2 are shown. 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-by, 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 bar in the image in the YZ direction is 20 μm. Represents.

[Bubble point pressure]

The polyolefin microporous membrane was cut into a circle with a diameter of 48 mm, immersed in ethanol, however, in accordance with JIS K3832:1990, however, the liquid temperature at the time of the test was changed to 24±2°C, and the measurement was started from the applied pressure of 0 MPa, and the pressure was raised. A bubble point test was performed while increasing the pressure at a speed of 2 kPa/sec to determine the bubble point pressure.

[Power]

The porosity ε (%) of the polyolefin microporous membrane was determined by the following equation.

ε={1-(Wa/xa+Wb/xb+Wc/xc+…+Wn/xn)/t}×100

Here, the constituent materials are a, b, c,… , n, and the masses of the constituent materials are Wa, Wb, Wc, ..., respectively. , Wn (g/cm2), and the true density of the constituent material is xa, xb, xc, ... , xn (g/cm 3 ), and the film thickness is t (cm).

[Gurley Value]

According to JIS P8117:2009, the air permeation time (second/100 mL) of a polyolefin microporous membrane having an area of 642 mm 2 was measured, and the air permeation time was divided by the thickness (μm) of the polyolefin microporous membrane, and the air permeation time per 1 μm in thickness. (Sec/100 mL·µm) was determined.

[Ethanol flow rate]

The polyolefin microporous membrane was cut out into 10 cm in the MD direction x 10 cm in the TD direction, immersed in ethanol, pulled up from ethanol, and dried at room temperature. The dried polyolefin microporous membrane was set in a stainless steel circular liquid permeation cell having a liquid permeation area of 17.34 cm 2. After wetting the polyolefin microporous membrane on the liquid permeation cell with a small amount (about 0.5 mL) of ethanol, 100 mL of ethanol was permeated at 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 of room temperature and 24°C. Measurement conditions and measured values were converted into units to obtain ethanol flow rate (mL/(min·cm 2·MPa)), and the ethanol flow rate was multiplied by the film thickness (µm) of the polyolefin microporous membrane measured in advance.

[Water contact angle]

The contact angle of water 1 second after dropping on the surface of the polyolefin microporous membrane was measured using a fully automatic contact angle meter DMo-701FE manufactured by Kyowa Chemical Industry Co., Ltd. and an analysis software FAMAS (interFAce Measurement and Analysis System). Under atmospheric pressure, in an atmosphere at a temperature of 24° C. and a relative humidity of 60%, 1 μL of water (ion-exchanged water) was added dropwise to the polyolefin microporous membrane, and the static contact angle 1 second after the dropping was measured. For the formation of water droplets, a syringe equipped with a 22G needle made of SUS (stainless steel) was used. About the polyolefin microporous membranes of Example 3 and Example 4, the contact angle of water was measured on the surface on the side to which the plasma treatment was performed.

[Pass the robbery]

The maximum thrust load (g) was measured by performing a needle penetration test (needle: a radius of curvature of the tip of 0.5 mm, thrust speed: 320 mm/min) using a Tensiron universal testing machine (RTE-1210), and the maximum thrust load was measured. It was divided by the film thickness (µm) of the polyolefin microporous membrane, and the piercing load per 1 µm in thickness (g/µm) was obtained.

<Production of immunochromatographic strips>

Using the hydrophilic polyethylene microporous membranes of Examples 1 to 4 or Comparative Examples 1 to 2, as the immunochromatographic strip (A) shown in Fig. 1, hCG (human chorionic gonadotropin) was used as a substance to be detected. A strip for immunochromatography to be described was produced according to the following procedure.

(1) Preparation of chromatography carrier (1)

The laminated body of the hydrophilic polyethylene microporous membrane and the PET film was cut into a rectangle having 150 mm MD direction and 25 mm TD direction along the MD and TD directions of the hydrophilic polyethylene microporous membrane. A phosphate buffer (pH 7.2) containing 0.5 mg/mL of an anti-hCG-α subunit antibody (mouse monoclonal antibody) was applied to the side of the hydrophilic polyethylene microporous membrane side of the cut laminate, 8 mm from the long side of one side. It was applied in a straight line parallel to the long side at the position of (application amount is 1 µL/cm). Subsequently, it was dried for 30 minutes in an atmosphere at a temperature of 50° C. to form the detection unit 11 on the hydrophilic polyethylene microporous membrane to obtain a chromatography carrier 1.

(2) Preparation of labeling substance dispersion

Anti-hCG antibody (mouse monoclonal antibody) (binding portion) to 10 mL of a dispersion of a 40 nm particle diameter gold colloid (labeled _{portion) diluted with 50 mM KH 2} PO _{4 buffer (pH 7.0) at a concentration of 60 μg/mL} ) Was added, and left to stand at room temperature for 10 minutes. Next, 0.5 mL of an aqueous solution of 1% by mass polyethylene glycol (PEG, weight average molecular weight 20,000) was added to the dispersion containing gold colloid and anti-hCG antibody, stirred, and then 1 mL of an aqueous solution of 10% by mass BSA (bovine serum albumin) And further stirred. Subsequently, centrifugation was performed for 15 minutes at a centrifugal acceleration of 7,000 G, and the supernatant was removed. Subsequently, in the precipitate, a 20 mM tris-hydrochloric acid buffer (Tris-HCl, pH 8.2) 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} ) Was added, and a labeling substance (anti-hCG antibody labeled with a gold colloid) was dispersed to obtain a labeling substance dispersion.

(3) Preparation of conjugate pad (3)

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

(4) Fabrication of the sample pad (2)

To a 150 mm×18 mm×340 μm cellulose pad (manufactured by Ahlstrom), 0.6 mL of tris-hydrochloric acid buffer (Tris-HCl, pH 8.2) was evenly applied, and then dried at a temperature of 50° C. for 1 hour, and the sample The pad (2) was obtained.

(5) Preparation of absorbent pad (4)

As the absorbent pad 4, a filter paper of 150 mm x 20 mm (manufactured by Lohmann) was prepared.

(6) Preparation of immunochromatographic strip (A)

On the support 5 (Lohmann backing sheet, 150 mm×60 mm) coated with an adhesive on one side, a chromatography carrier 1, a conjugate pad 3, a sample pad 2, and an absorbent pad 4 were placed. It bonded together to obtain a composite sheet. At that time, the overlapping width of the sample pad 2 and the conjugate pad 3 was 4 mm, the overlapping width of the conjugate pad 3 and the chromatography carrier 1 was 2 mm, and the chromatography carrier 1 and the absorption pad The overlapping width of (4) was 5 mm, and the detection part 11 of the chromatography carrier 1 was made closer to the absorption pad 4 than the conjugate pad 3. The entire composite sheet was cut every 5 mm width in the longitudinal direction, and an immunochromatographic strip A (full length 60 mm in the expansion direction, 5 mm width. The TD direction of the hydrophilic polyethylene microporous membrane is the sample development direction). Got it.

<Performance evaluation of immunochromatographic strip>

The following performance evaluation tests were performed in an atmosphere at a temperature of 24°C and a relative humidity of 60%. In Table 2, the evaluation results of the immunochromatographic strip (A) are shown.

[Saturation time]

A sample was prepared by diluting _{BSA in a phosphate buffer containing 1% by mass and 0.095% by mass of NaN 3} so that the hCG antigen (substance to be detected) was 16.7 nkat. 100 µL of a sample was dropped onto the sample pad 2 of the immunochromatography strip (A) and developed, and the emission peak wavelength was 520 nm using an immunochromator (manufactured by Hamamatsu Photonics, Model No. C10066-10). Using a nearby light emitting diode (LED) as a light source, the absorbance in the detection unit 11 was measured over time. Taking the time when the sample was dropped onto the sample pad 2 as a starting point, the time until the color development (red) of the detection unit 11 becomes saturated (referred to as saturation time) was measured, and classified into the following three steps. In Fig. 3, changes over time in absorbance in Example 2 and Comparative Example 1 are shown.

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 of detection part]

Simultaneously with the measurement of the saturation time, the clarity of color development (red) of the detection unit 11 was visually determined and classified into the following three steps.

A: You can clearly see the red line on the detection part.

B: You can see a red line on the detection part

C: A red line can be seen on the detector, but it is unclear

[Table 2]

As for the indication of Japanese Application No. 2018-202062 for which it applied on October 26, 2018, the whole is taken in into this specification by reference.

All documents, patent applications, and technical standards described in this specification are incorporated by reference in the present specification to the same extent as those specifically and individually described that individual documents, patent applications, and technical standards are introduced by reference. .

A: Immunochromatography strip
X: unfolding direction
1: chromatography carrier
2: sample pad
3: conjugate pad
4: absorbent pad
5: support
11: detection unit

Claims (12)

A polyolefin microporous 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 : The curvature rate in the first direction along the first surface of the polyolefin microporous membrane.
τ _Y : The curvature rate in the second direction along the first surface of the polyolefin microporous membrane and perpendicular to the first direction.
τ _Z : The curvature ratio in the thickness direction of the polyolefin microporous membrane. A polyolefin microporous membrane having a film thickness of 1 µm to 400 µm and satisfying the following formulas (3) and (4).
Equation (3): 0.5≤T _X /T _{Z ≤2.0}
Equation (4): 0.5≤T _Y /T _{Z ≤2.0}
T _X : Permeability index in the first direction along the first surface of the polyolefin microporous membrane.
T _Y : Permeability index in the second direction along the first surface of the polyolefin microporous membrane and perpendicular to the first direction.
T _Z : Permeability index in the thickness direction of the polyolefin microporous membrane. The method according to claim 1 or 2,
A polyolefin microporous membrane having a bubble point pressure of 0.001 MPa or more and less than 0.1 MPa. The method according to any one of claims 1 to 3,
A polyolefin microporous membrane in which the product of the ethanol flow rate (mL/(min·cm2·MPa)) and the film thickness (µm) is 50,000 to 500,000. The method according to any one of claims 1 to 4,
A polyolefin microporous membrane having a Gurley value per unit thickness of 0.0005 sec/100 mL·µm to 0.1 sec/100 ml·µm. The method according to any one of claims 1 to 5,
A polyolefin microporous membrane having a porosity of 70% to 95%. The method according to any one of claims 1 to 6,
A polyolefin microporous membrane having a hydrophilic polyolefin microporous membrane, and having a contact angle of water 1 second after dropping on at least one surface of 0 to 90 degrees. The method of claim 7,
The hydrophilic polyolefin microporous membrane has a hydrophilic material on at least one of the membrane surface and the pore inner surface. The method according to claim 7 or 8,
The said hydrophilic polyolefin microporous membrane is a polyolefin microporous membrane physically subjected to a hydrophilization treatment on at least one of the membrane surface and the inner surface of the pores. A filter comprising 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, and
As a detection unit provided in the polyolefin microporous membrane, a detection unit in which a detection reagent specifically binding to a substance to be detected is fixed
Immunochromatography strip comprising a.

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