JPS6297603A - Porous membrane of polypropylene and production thereof - Google Patents

Abstract

PURPOSE:To obtain a membrane having high porosity and water permeability which enables stable separation of blood plasma, by producing a membrane in such a manner that propylene, to which organic filler and crystalline-nucleus formation agents dispersing uniformly in molten polypropylene being added, is melted and kneaded. CONSTITUTION:A compound 11 consisting of polypropylene and an organic filler and, if required, a crystalline nucleus formation agent is fed from a hopper 12 to a kneading machine 13, melted, kneaded, extruded and discharged through a T-die 14 to be formed into a flat film. Said extruded compound is immediately contacted with a cooling liquid 16 in a cooling tank 15 to be completely cooled and solidified and wound up on a tension roll 19. Film-shaped material thus wound up is led to an extraction tank containing extraction liquid, where organic filler is extracted. Further, heat treatment is carried out under sizing, whereby a membrane having an average pore diameter of 0.1-5mum, bubble point not exceeding 1.8kgf/cm<2>, porosity of 60-85%, water permeability of 100ml/min mmHg m<2>, wherein a core layer having a porous surface and net work structures between layers, is formed.

Description

Detailed Description of the Invention ■1 Background of the Invention (Technical Field) The present invention relates to a flat membrane type device used for plasma separation to separate blood into blood cell components and plasma components, removal of bacteria from blood, etc. The present invention relates to a porous polypropylene membrane and a method for producing the same.

More specifically, the present invention relates to a polypropylene porous membrane that has high porosity and high water permeability and causes little damage to separated blood cells and plasma components when used for plasma separation, and a method for producing the same.

PRIOR ART A variety of permeable membranes have been used in the past to separate blood into corpuscular and plasma components. These permeable membranes are used for example in systemic erythera 1--death, rheumatoid arthritis,
Abnormal proteins and antigens in diseases caused by immune abnormalities such as glomerulonephritis 1 myasthenia gravis.

Plasma separation permeable membranes are used for plasma purification for the purpose of removing antibodies, immune complexes, etc., as well as for preparation of plasma preparations for component transfusion, pretreatment of artificial kidneys, and the like. Such membranes for plasma separation include cellulose acetate membranes (Japanese Patent Laid-Open No. 54-15476), polyvinyl alcohol membranes, polyester membranes, polycarbonate membranes, polymethyl methacrylate membranes, and polyethylene membranes (Japanese Patent Laid-Open No. 57-84).
No. 702) etc. have been used. However, these membranes for plasma separation not only have insufficient mechanical strength, porosity, and plasma separation ability, but when used for plasma separation, red blood cells are damaged due to clogging, and plasma components are Certain complements were activated and the separated plasma was severely damaged.

In addition, polymers that are poorly soluble in solvents and stretchable, such as crystalline polyolefins and polyamides, and polymers that are partially compatible with the polymers and easily soluble in solvents are also used. A permeable membrane has been proposed in which a mixture with kimono is molded into a film, sheet, or hollow body, the molded body is treated with a solvent, and after drying, the film is expanded by 50 to 1500% in one or two axial directions. (Japanese Unexamined Patent Publication No. 57-20, No. 970).

However, since such membranes are stretched to increase the pore size, when used for medical purposes, they are not only unable to be sterilized in an autoclave, but also undergo significant heat shrinkage.
Furthermore, since the pore structures on both surfaces and inside the membrane are almost uniform, when used for plasma separation, clogging with proteins and blood cells is likely to occur.

Alternatively, a molten mixture of 10 to 80% by weight of paraffin and 90 to 20% by weight of polypropylene resin is extruded through a die into a film, sheet, or hollow fiber, and the molten mixture is introduced into water maintained at 50° C. or below for rapid cooling and solidification. A method for producing a porous membrane for extracting and separating paraffin from the obtained molded product is disclosed (Japanese Patent Laid-Open No. 55-605
However, the porous membrane obtained by this method had a low porosity and water permeability, and could be used for gas separation, but the filtration rate was extremely low and it could not be used for plasma separation.

■3 Purpose of the Invention Therefore, the present invention provides a flat membrane type porous polypropylene J that has high porosity and water permeability, has a fast plasma separation rate, and is capable of stable plasma separation with less clogging of proteins and blood cells.
The purpose of the present invention is to provide li and a method for producing the same.

A membrane that achieves these objectives has a superficial porous layer with a network structure on both sides of the membrane, and a core layer with a denser network structure than the superficial porous layer is formed between the superficial porous layers. , average pore size is 0.1-5.0μm, bubble point is 1
．． A flat membrane type polypropylene porous membrane consisting essentially of polypropylene, having a porosity of 8 Kgf/am2 or less, a porosity of 60 to 85%, a water permeability of 100 ml/n1n-+nmHg-m2 or more, and a film thickness of 30 to 300 μmm. be.

It is preferable that the surface porous layer accounts for 5 to 301 parts of the entire film. Bubble point is 1.1kgf/
It is preferable that c +n is 2 or less. Furthermore, it is preferable that the water permeation amount is 140 nl/+in-+*mt1g-m2 or more. Further, the porous membrane has 121
It is preferable that the shrinkage rate after heat treatment at ℃ for 120 minutes is 6.0% or less.

Furthermore, what achieves the object of the present invention is that for every 100 parts of polypropylene, 200 parts of organic filler can be uniformly dispersed in the polypropylene while the polypropylene is melted.
~600 parts by weight and 0.1 to 5.0 parts by weight of a crystal nucleating agent were added and melt-kneaded, and the mixture thus obtained was discharged in a molten state from a die in the form of a flat film, and the discharged molten The membrane is immersed in a cooling solidification liquid consisting of the organic filler or its similar compound or a solvent that is compatible with the organic filler, and then brought into contact with an extraction liquid that does not dissolve polypropylene to remove the organic filler containing the membrane. After removal, the resulting polypropylene film was fixed at a certain length and 11
This is a method for producing a flat polypropylene porous membrane in which heat treatment is performed at a temperature of 0 to 150°C.

Further, the crystal nucleating agent is preferably an organic heat-resistant substance having a melting point of 150° C. or higher and a gel 1 Hi point higher than the crystallization initiation temperature of polypropylene.

Furthermore, it is preferable that the extract is a mixture of halogenated carbon and arsenic.

■1 Specific structure of the invention The present invention will be specifically explained below.

The flat membrane type polypropylene porous membrane of the present invention is a porous membrane substantially made of polypropylene, and has a superficial porous layer having a network structure on both sides of the membrane, and a superficial porous layer between the superficial porous layers. A core layer with a denser network structure is formed, and the average pore size is 0.1 to 5.0 μm, preferably 0.2
~3.0ALm, ^Bubble point measured using isopropyl alcohol according to STMF316 modified method is 1
．． 8 kgf/am2 or less, preferably 1.1 kgf/a
m2 or less, porosity is 60-85%, preferably 65-8
5%, water permeability is 100ml/+in-mmHg-m2 or more, preferably 140ml/sin-mmHfI-m2
In addition to the above, the film thickness is 30 to 300 μIO1, preferably 6
It is 0 to 200 μm. Furthermore, it is preferable that the surface porous layer accounts for 5 to 3 oz of the entire membrane. The above-mentioned network structure has a state in which string-like filaments are intertwined.

Surprisingly, when the polypropylene porous membrane of the present invention having such characteristics is used for plasma separation, the surface porous layer acts as a pre-filter, allowing proteins, proteins,
It has been found that plasma separation can be performed stably with less clogging of blood cells, and damage to the separated plasma, particularly activation of complement components, can be kept to an extremely low level.

Activation of complement components in plasma occurs through the so-called classical pathway (CI
assical Patbway) or the so-called separate route (81tern+aLiue Patl+way)
), and it is thought that activation occurs through two routes, and which route causes stronger activation depends on the type of polymer. For example, cellulose acetate membranes and polyvinyl alcohol membranes conventionally used as membranes for plasma separation cause complement activation through a different route.

Polymethyl methacrylate membranes, which have been considered to be an excellent material in terms of complement activity, have been shown to cause significant activation of alternative pathways in plasma that passes through the pores of the membrane and is separated. I've come to understand.

In contrast, the porous membrane of the present invention showed extremely low complement activation even in plasma that had passed through the pores of the membrane and was separated.

In the porous membrane of the present invention, the average pore diameter is 0.1 to 5°θ
Being μ-shaped is a diameter that allows plasma components to pass through without passing through blood cell components (red blood cells, white blood cells, platelets), and within the above range, without passing through blood cell components. It can permeate more than 95% of total protein, which is a plasma component. Further, it is preferable that the pot has an average pore diameter of 0.2 to 3.0 μm. Note that the average pore diameter referred to here is the average pore diameter of the entire membrane as measured using a mercury porosimeter, and does not refer to the pore diameter of only the surface porous layer. Furthermore, the reason why the bubble point is 1.8 kgf/cm2 or less is to define the maximum pore diameter of the membrane. They do things like that.

In addition, the porosity needs to be 60 to 85%, and 60% to 85%.
If it is less than 85%, performance may deteriorate or a sufficient plasma separation rate may not be obtained, while if it exceeds 85%, it may not be strong enough to withstand use. In addition, the water permeability is 100ml/m
i++·mmHg-m2 or more is required, and if it is less than this, there is a possibility that a sufficient plasma separation rate may not be obtained.

Furthermore, the film thickness needs to be 30 to 300 μm, and 3
If it is less than 0 μm, there will be a problem in terms of strength, while if it exceeds 300 μm, it will take up a large volume when incorporated into a module, causing a practical problem.

In addition, the surface porous roofing layer accounts for 5 to 30% of the entire membrane.
It is preferable that If it is less than 5%, the effect of the prefilter may be insufficient when used for plasma separation, and if it exceeds 30%, there is a risk that membrane strength that can withstand use may not be obtained. The portion of the membrane other than the surface porous layer is a core layer having a denser network structure than the surface porous layer. Further, the porous membrane of the present invention has a flat membrane shape.

The above porous membrane has a shrinkage rate of 6 after heat treatment at 121°C.
．． It is preferably 0% or less. Heat treatment at 121° C. for 120 minutes indicates high-pressure steam sterilization according to the Japanese Pharmacopoeia. The shrinkage rate indicates the degree of change in the porous membrane before and after the heat treatment.

Since the porous membrane of the present invention is a flat membrane, the change in the length of the porous membrane in the direction of the forming axis and the length in the direction perpendicular to the forming axis after the heat treatment is 6.0% or less. Shrinkage rate is 6.
This is because if it exceeds 0%, as will be described later, the amount of water permeated after heat treatment and the plasma separation rate will decrease, making it impossible to separate blood components sufficiently. Further, it is preferable that the shrinkage rate is 3.0% or less.

The polypropylene porous membrane of the present invention having such characteristics is produced, for example, as follows.

That is, as shown in FIG. 1, polypropylene, an organic filler, and a crystal nucleating agent mixture 11, which is blended as necessary, are supplied from a hopper 12 to a mixer, for example, a twin-screw extruder 13. Melt-knead and extrude the compound,
It is fed into the T-die 14 and discharged in the form of a flat film, and is brought into contact with the cooling liquid 16 in the cooling tank 15 to solidify it, and is also brought into contact with the roll 17 in the cooling tank 15, so that it is completely removed while passing through the cooling tank 15. Cool and solidify, then pull roll 1
Wind it up to 9. Further, during this time, the cooling liquid 16 supplied from the line 20 is discharged from the line 21, and then cooled to a predetermined temperature by a cooling device (for example, a heat exchanger) 22 and recirculated.

Then, the wound film-like material is further introduced into an extraction tank (not shown) containing an extraction liquid to extract the organic filler. As described below, if this extract is volatile and immiscible with water, such as halogenated carbon or arsenic, a layer of water or the like may be provided as an upper layer to prevent evaporation. . Then, if necessary, re-extraction is performed, and in order to stabilize the structure and permeation performance, it is preferable to fix the membrane-like material to a certain length and perform heat treatment. The organic filler may be extracted by providing an extraction layer before winding.

The polypropylene used as a raw material in the present invention is not limited to a 10-pyrene homopolymer, but includes block polymers containing propylene as a main component and other monomers (eg, polyethylene). The melt index (M, 1.) is preferably 5 to 7o, especially Hol
, is preferably from 1o to 4o.Also, for the purpose of increasing the strength of the membrane, those with a large molecular weight, that is, M, 1. It may also be blended with polypropylene having a low carbon content. Among the polypropylenes, propylene homopolymers are particularly preferred, and those with a high degree of crystallinity are more preferred. The degree of crystallinity is the weight fraction of the crystalline portion relative to the total weight, and is determined by X-ray diffraction, infrared absorption spectrum, density, etc.

And generally vinyl polymer (Ct12-CHR)n
can take on three tertiary structures depending on the arrangement of the substituents R: regular atactic and syndiotactic, and irregular atactic. When a polymer has a high proportion of tactic or syndiotactic, crystallization is easy. This also applies to polypropylene, and when expressed in terms of toughness, which is an index different from the crystallinity of polypropylene, it is preferable that the toughness is 97% or more. The melting point of polypropylene varies depending on the degree of polymerization and the like, and is approximately 160 to 180°C.

The organic filler used in the production method of the present invention must be one that can be uniformly dispersed in the polyolefin while it is melted, and that is easily soluble in the extract as described below. is necessary. As such a filler, liquid paraffin (number average molecule i 100
~2000)-α-olefin oligomer [e.g., ethylene oligomer (number average molecular weight 100-2000),
Propylene oligomer (number average molecular weight 100-2000
), ethylene-propylene oligomer (number average molecular weight 100-2000), Kobara fin wax (number average molecular weight M2O 0-2500), various hydrocarbons, etc.
Liquid paraffin is preferred.

The proportion of polypropylene and the organic filler is 200 to 60 parts by weight of the organic filler per 100 parts by weight of polypropylene.
0 parts by weight, preferably 300 to 500 parts by weight.

If the organic filler is less than 200 parts by weight, the porosity and water permeability will be too low to provide sufficient filtration performance, and if it exceeds 600 parts by weight, the viscosity will be too low and it will be difficult to form it into a membrane. This is because workability is reduced. Such raw material mixtures are prepared (designed) by a pre-kneading method in which a mixture of a predetermined composition is melt-kneaded using an extruder such as a twin-screw extruder, extruded, and then pelletized. do.

In the present invention, the crystal nucleating agent blended into the raw material has a melting point of 150°C or higher, preferably 200 to 250°C.
It is an organic heat-resistant substance with a gel point higher than the crystallization initiation temperature of the polypropylene used. The reason for distributing such a crystal nucleation agent is Bolin.

The aim is to reduce the size of Robylene particles by controlling the pore size of the pores formed by the organic filler that is kneaded and subsequently extracted. - For example, 1, 3, 2.
4-dibenzylidene sorbitol, 1,3,2° 4-bis(P-methylbenzylidene) sorbitol, 1°3.
2.4- (P-ethylbenzylidene) sorbitol,
Examples include sodium bis(4-butylphenyl)phosphate, sodium benzoate, adipic acid, talc, and kaolin. Generally, crystal nucleation molding agents are used to improve the transparency of molded resins. However, by using the crystal nucleating agent in the present invention, the polypropylene particles are reduced to the extent that the pore size of the pores formed in the membrane is not restricted by the polypropylene particle size.
The voids formed by the organic filler extracted after kneading can be controlled to a desired pore size. This is the Borip part. The raw material mixture thus prepared is further processed using an extruder such as a twin-screw extruder, for example,
The mixture is melted and kneaded at a temperature of 0° C., preferably 180 to 230° C., and discharged from a T-die in the form of a flat film, and the molten discharged material is allowed to fall and come into contact with the cooled solidified liquid in a cooling tank.

As the cooling solidification liquid, a solvent having compatibility with the organic filler, its analogous compound, or the organic filler is used. For example, when liquid paraffin with a number average molecular weight of 324 is used as the organic filler or its similar compound, the cooling solidification liquid may be liquid paraffin, such as liquid paraffin with a number average molecular weight of M324, liquid paraffin with a number average molecular weight of 299, or liquid paraffin with a number average molecular weight of 299. It is preferable to use liquid paraffin having a relatively similar number average molecular weight, such as liquid paraffin having a molecular weight of 420. Furthermore, examples of solvents that are compatible with the organic filler include tetrachloromethane, 1,1,2.2-tetrachloro-1,2 difluoroethane, and 1,2.2-1-lichloro1.2.2. -) There are halogen arsenic hydrocarbons such as refluoroethane, trichloroethylene, and perchlorethylene.

In the present invention, by using an organic filler, a similar compound thereof, or a solvent that is compatible with the organic filler in the cooling liquid, a surface porous layer having a relatively loose network structure is formed on both sides of the membrane, and a surface porous layer is formed inside the layer. We were able to obtain a highly permeable porous membrane with a sandwich structure consisting of a core layer with a denser network structure than the core layer. It is preferable to use an organic filler or its analog as the cooling liquid. The reason for this is that by being compatible with the organic filler in the raw material, a surface porous layer having a relatively loose network structure can be reliably formed on the membrane surface.

The film-like material that has completely charred on the cooling surface in the cooling solidification tank is sent to an extraction tank or the like, where the organic filler is dissolved and extracted. Methods for dissolving and extracting the organic filler include an extraction tank method, a one-way shower method in which extract liquid is showered onto a film-like material on a belt conveyor, and a method in which a film-like material that has been rolled up once is rolled back into another skein. Any method may be used as long as the film-like material can come into contact with the extract, such as a rolling method in which a skein is immersed in the extract, and it is also possible to combine two or more of these methods.

As the extraction liquid, any liquid can be used as long as it does not dissolve the polyrobylene constituting the porous membrane and can dissolve and extract the organic filler. - Examples include, for example, tetrachloromethane, 1. l,2-trichloro-1,2,2
-) Lifluoroethane, 1,1.2-trichloro-1,
There are halogenated hydrocarbons such as 2,2-)lifluoroethane, trichlorofluoromethane, dichlorofluoromethane, 1,1,2.2-tetrachloro-1,2-difluoroethane, trichlorethylene, perchlorethylene, etc. Of these, chlorinated fluorohydrocarbons are preferred from the viewpoint of extraction ability for organic fillers and safety for the human body. The porous membrane thus obtained is preferably further heat treated. The heat treatment is performed in a gaseous atmosphere such as air, nitrogen, or carbon dioxide at a temperature that is 10 to 50°C lower than the melting temperature of polypropylene, for example, 110 to 50°C.
The heating is carried out at a temperature of 150°C, preferably 130-140°C, for 60-180 seconds. When performing the above-mentioned heat treatment, it is necessary to fix the obtained porous membrane to a certain length in advance. The above-mentioned fixation of a certain length may be performed by cutting it into a certain length. The heat treatment may be performed after the polypropylene film is cooled and solidified, but before the organic filler is extracted.

The method of measuring physical properties used in the present invention is as follows.

(1) Bubble Point ^ Measurement was performed according to the STM F316 modified method using isopropyl alcohol as the liquid phase using a stainless steel holder with a diameter of 47 mm. The pressure was then increased, and the pressure at which a series of nitrogen bubbles began to rise uniformly and without interruption from the center of the filter in the isopropyl alcohol was defined as the bubble point.

(2) Film thickness Actual measurements were made using a micrometer.

(3) Porosity (r') After the porous membrane is immersed in ethanol, the porous membrane is replaced with water to make it hydrated, and the weight when hydrated <1'lp) is measured. when dry.

When the weight is l'l+ll and the density of the polymer is Pg/ml, the porosity (P) is calculated by the following formula.

(W p - W 111) P-X100 ($) (W/P), + (Wp-Ww) (4) Water permeability 0.7 Kgf/ for a membrane with a membrane area of 1.45 x 10-'m2
Permeate water at 25°C under a pressure of cm2, 100II
The time required for 11 to pass through was measured.

(5) Maximum plasma velocity (Qfmax) Measured using the circuit shown in FIG. Hemadcrit 40 in measurement
Using % heparinized fresh bovine blood (5000U/1), the blood flow rate was 100ml/m in module 30 with a membrane area of 0.4m2.
10 → 15-20 every 30 minutes from the filtrate pump flow rate of 10 ml/min by circulating with a pressure loss of 30 mm/min.
→ Increase to 25-30 → 40 → 42 and T within 30 minutes
MP () - Talmen Plan Pressure) is 20mm
Let Qfmax be the amount of filtration immediately before the amount increases by Hg or more.

However, T M P = P in + P out/2
- P fit.

Gl, G2 in FIG. G3 is a pressure meter, the pressure of G1 is Pin, the pressure of G2 is Pfil, and the pressure of G3 is Pout. P each indicates a pump.

(6) Average pore diameter Measured using a mercury porosimeter.

(7) Complement activity (C3a, C4a) Blood collected from a healthy person was transferred to a glass test tube and heated to 37°C.
Did you heat it for 15 minutes and completely coagulate the blood? The inflammation serum was isolated. Centrifugation is performed at 4℃ and 3000r in a refrigerated centrifuge.
The separated serum, which was carried out at pm for 20 minutes, was immediately transferred to ice water. Membrane area 24 provided with porous membrane 35
The mini module 30 of c+*2 was set in the circuit shown in Fig. 3, serum was circulated at a flow rate of 5 ml/min, and the serum coming out from the filtration source side outlet 40 was sampled every 1.5 ml, and was analyzed by RIA method. C3a and C4a concentrations were measured.

C3a and C4a are generated during the complement activation process, and it can be said that the less they are present, the less complement activation occurs.
In the figure, 42 is a heating tank at 37° C., and 44 is a cooling tank containing ice water.

Examples 1 to 3, Comparative Examples 1 to 3, per 100 parts by weight of polypropylene (mixture) with a melt flow index of 30 and 0.3, the flow rate of paraffin (a few thousand equal parts 'i') was as shown in Table 1. -I::324
) and 1,3,2.4bis(paraethylbenzylidene)sorbitol as a crystal nucleating agent were melt-kneaded and pelletized using a twin-screw extruder (manufactured by Ikegai Tekko Co., Ltd.). It was melted at ~200° C., extruded into the air through a T-die with a slit width of 0.6+ nm, plunged into a cooling liquid tank placed directly below the T-die, cooled, and then rolled up. The cooling liquid and its temperature are as shown in Table 1. Roll up the film-like material to a certain length (approximately 200 x 2 (j
Otn tn ), fix both length and width, 1,
1.2-), Rechloro 1.2.2-) Liquid paraffin was extracted by immersing in refluoroethane (liquid temperature 25°C) for 10 minutes four times in total, and then in air at 135°C for 2 minutes. Heat treatment was performed. The obtained porous membrane had a surface porous layer having a relatively sparse network structure on both sides, and a core layer having a denser network structure than the surface porous layer on the inner side. FIG. 4 is a photograph taken by a scanning electron microscope (magnification: 1000) showing the surface of the porous membrane of Example 1;
No. 511Z is a photograph taken by a scanning electronic IS mirror (magnification: 3000) showing a partial cross section of the porous membrane of Example 1;
It can be seen from FIG. 5 that a superficial porous layer is formed on the surface and a core tank is formed inside the surface porous layer. FIG. 6 is a photograph taken with a scanning electronics tE1 mirror showing the surface of the porous membrane of Comparative Example 2 (
7 is a photograph taken by a scanning electron microscope (magnification 3000) showing a partial cross section of the porous membrane of Comparative Example 1.
0). It can be seen from these photographs that no surface porous layer was formed on the surface. When evaluating filtration performance, membranes were stacked, assembled into a module, made hydrophilic with 50% ethanol water, and washed with water before use. The results were as shown in Table 1.

Comparative Example 4 Comparative Example 4 was a commercially available cellulose acetate membrane (CA, manufactured by Toyo Roshi).

Comparative Example 5.6 A sample was prepared without undergoing the heat treatment in air at 135° C. for 2 minutes as in the example. In other respects, a porous membrane obtained by the same method as in Example 1.2 was designated as Comparative Example 5.6.

The measurement results of C3a and C4a of Example 1 and Comparative Example 4 are shown in Tables 3 and 4.

Table 3 Change in concentration of C3a Table 3 Change in concentration of C4a As is clear from these results, the porous membrane of the present invention has a high porosity, high water permeability, and high plasma separation rate. On the other hand, in Comparative Example 1, in which the organic filler content was less than 200 parts by weight, both the porosity and the water permeability were low, and the plasma separation rate was also low. Furthermore, in Comparative Example 2 using water cooling, no surface porous layer was formed and the plasma separation rate was low. Furthermore, the porous membrane of the present invention, which is heat-treated after being fixed to a certain length, is a thermally stable membrane that does not change in size due to autoclave sterilization and does not change in porosity or water permeability. , the membrane of the comparative example showed significant shrinkage after autoclave sterilization.
For example, when assembled into a product, there is a risk of problems such as the sealing part breaking after being autoclaved, and other membrane performances would also be significantly degraded.

(1) Specific effects of the invention A surface porous layer having a relatively sparse network structure is provided on both sides of the membrane, and a core layer having a denser network structure than the surface porous layer is formed between the surface porous snow layers. , average pore diameter is 0.1~
5.0μm, bubble point is 1. ,8 kg f
/c1112 or less, porosity 60-85%, water permeability 1
00+nl/min・IIIHg-2 or more, and the film thickness is 30-300 μm.It is a flat membrane porous membrane made of polypropylene that is essentially made of polypropylene, so it has a high porosity and water permeability, making it suitable for plasma separation. In this case, a highly efficient plasma separation membrane with less clogging by proteins, blood cells, etc. can be obtained, and the separated plasma is extremely less damaged. In particular, the activation of the complement system is extremely low, and it can be suitably used as a plasma separation membrane to separate blood into blood cell components and plasma components, especially when plasma separated as in donor pheresis is used. This is particularly useful when

Furthermore, the bubble point is 1.1Kgf/cm” or less,
Porosity is 65-83%, water permeability is 140ml/+in-
mmHg-m2 or more, and the film thickness is 60 to 200μ
If it is m, it will be more excellent.

The present invention also includes adding, to 100 parts by weight of polypropylene, 200 to 600 parts by weight of an organic filler and 0.1 to 5.0 parts by weight of a crystal nucleating agent, which can be uniformly dispersed in the polypropylene while the polypropylene is melted. The mixture thus obtained is discharged in a molten state from a die, and the discharged molten film is mixed with the organic filler, agent or similar compound thereof, or a solvent that is compatible with the organic filler. The resulting polypropylene film is then protruded into a cooled solidified liquid consisting of a polypropylene film, and then brought into contact with an extraction liquid that does not dissolve the polypropylene to remove the organic filler contained therein.The resulting polypropylene film is then fixed to a certain length and heat-treated at a temperature of 110 to 150°C. Since this is a method for producing a flat membrane type porous polypropylene membrane, it is possible to easily produce a porous membrane having excellent performance as described above.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of an example of a manufacturing apparatus used in the method for manufacturing a flat membrane type porous polypropylene membrane of the present invention, Figure 2 is a circuit diagram for measuring the maximum plasma separation rate, and Figure 3 is a diagram of complement A circuit diagram for measuring activity, FIGS. 4 and 5 are electron micrographs of the membrane surface and partial cross section of the porous membrane of the present invention,
FIGS. 6 and 7 are electron micrographs of the membrane surface and partial cross section of a porous membrane of a comparative example. 11... Compound 12... Hopper 13...
Single screw extruder 14...Dice 15...Cooling tank
16... Coolant 17... Roll 18... Tension roll 19... Winding roll

Claims (9)

[Claims] (1) Having a surface porous layer with a network structure on both sides of the membrane,
A core layer having a denser network structure than the surface porous layer is formed between the surface porous layers, and has an average pore diameter of 0.1 to 5.0.
μm, bubble point less than 1.8kgf/cm^2,
Porosity is 60-85%, water permeability is 100ml/min・
mmHg・m^2 or more, and the film thickness is 30 to 300 μm
A flat polypropylene porous membrane characterized in that it consists essentially of polypropylene. (2) The proportion of the surface porous layer in the entire membrane is 5 to 3
0% of the porous membrane according to claim 1. (3) The porous membrane according to claim 1 or 2, wherein the bubble point is 1.1 kgf/cm^2 or less. (4) The water permeability is 140ml/min・mmHg・m
^2 or more, the porous membrane according to any one of claims 1 to 3. (5) The porous membrane according to any one of claims 1 to 4, wherein the porous membrane has a shrinkage rate of 6.0% or less after heat treatment at 120° C. for 120 minutes. (6) To 100 parts by weight of polypropylene, add 200 to 600 parts by weight of an organic filler and 0.1 to 5.0 parts by weight of a crystal nucleating agent that can be uniformly dispersed in the polypropylene while the polypropylene is melted. The mixture thus obtained is then discharged in a molten state from a die in the form of a flat film. The resulting polypropylene film was fixed at a certain length and heated at 110 to 140°C. A method for producing a flat polypropylene porous membrane characterized by heat treatment at a high temperature. (7) The method for producing a porous membrane according to claim 6, wherein the crystal nucleating agent is added in an amount of 0.1 to 1.0 parts by weight. (8) The porous nucleating agent according to claim 6 or 7, wherein the crystal nucleating agent is an organic heat-resistant substance having a melting point of 150° C. or higher and a gelling point higher than the crystallization initiation temperature of polypropylene. Method for manufacturing membranes. (9) The method for producing a porous membrane according to any one of claims 6 to 8, wherein the extract is a halogenated hydrocarbon.