JPH03174230A - Flat permeable membrane - Google Patents

Abstract

PURPOSE:To form the permeable membrane useful in filtering crystals, etc., by forming one surface of a flat polyolefin membrane having a specified composition with a dense layer in which polyolefin fine particles are closely bound together and forming the inside and other surface with a continuous aggregate of fine particles. CONSTITUTION:The one surface of a flat polyolefin membrane 1 having 10-500mum thickness T is formed with a dense layer 2 in which polyolefin fine particles are closely bound together and having micropores. The average diameter of the micropores is controlled to about 0.01-2mum, and the surface is smoothed. Meanwhile, the inside and other surface are formed with a continuous aggregate layer 4 of independent fine particles 3 of polyolefin having 0.02-1.0mum average diameter, the fine communicating holes 5 communicating with one another in the form of a labyrinth are formed, and both surfaces are communicated. The polyolefin constituting the member 1 has a m.p. of >=150 deg.C and contains an org. crystal nucleus forming agent having a specified gel point.

Description

[Detailed description of the invention] ■0 Background of the invention Technical field The present invention relates to a flat membrane type permeable membrane.

More specifically, the present invention relates to a flat membrane type permeable membrane useful for plasma filtration. More specifically, the present invention relates to a flat membrane permeable membrane that efficiently removes pathogenic macromolecules, has a high albumin recovery rate, has a fast filtration rate, and has a controlled pore size that can efficiently process a large amount of plasma.

PRIOR ART In the past, various permeable membranes have been used to separate blood into corpuscular and plasma components. For example, permeable membranes for plasma separation are used in the preparation of plasma preparations for component transfusions, in the pretreatment of artificial kidneys, and in plasmapheresis therapy. This plasma exchange therapy has been recognized to be effective against autoimmune diseases such as liver failure, myasthenia gravis, and rheumatoid arthritis. In order to carry out this plasmapheresis therapy effectively, blood is separated into blood cells and plasma components, the plasma containing the pathogenic substance is then discarded, and healthy human plasma or plasma preparations are added. However, due to problems such as securing plasma preparations and side effects of infection, it is desirable to use a method in which separated autologous plasma is purified and then mixed with blood cell components, and the development of a separation membrane for this purpose is desired.

Such plasma separation membranes include regenerated cellulose membranes,
Cellulose acetate membranes, polyvinyl alcohol membranes, polysulfone membranes, polymethyl methacrylate membranes, and the like are known. However, these polymer membranes have insufficient mechanical strength, membrane pore size, plasma processing capacity, etc., and albumin, which is useful for the human body, cannot pass through them.Also, even though albumin does pass through, pathogenic macromolecules cannot pass through them at the same time. or
Alternatively, in many cases, the membrane quickly became clogged and a sufficient amount of pathogenic macromolecules could not be removed. The pathogenic macromolecules referred to here include immunoglobulin M (Ig M, My approximately 950,000), which has a larger molecular weight than albumin, low-density lipoprotein (LDL, My approximately 1.2 million to 3.3 million), immune complexes, and rheumatoid arthritis. factors etc. Under these circumstances, in order to remove the target pathogenic macromolecules and return albumin, the remaining useful plasma component, to the body, a large amount of albumin with the desired pore size and porosity and a membrane structure that is resistant to clogging is necessary. A separation membrane that can purify plasma is needed.

In this way, as a separation membrane for removing plasma components with medium molecular weight or higher, at least 0.955 g/c! 13
A porous hollow fiber membrane made of high-density polyethylene having a density of A porous polyethylene hollow fiber membrane with a membrane porosity of 30 to 90% by volume has been proposed (Japanese Patent Laid-Open No. 58-75, 55).
No. 5). However, in such hollow fiber membranes, micropores are mechanically formed by cold stretching and then hot stretching highly oriented crystalline unstretched hollow fibers, and furthermore, the micropores are internally formed. Since the pores are almost straight from the surface side to the outer surface side and have almost the same diameter, the pore density per unit volume cannot be increased, the amount of plasma processed per unit area is small, and the recovery rate of albumin etc. is low. . In addition, it is easily torn due to orientation, and is greatly deformed and shrunk by heating such as autoclave sterilization.

Further, the hollow fiber membrane has a dense layer on at least one surface,
A hollow fiber made of a vinyl alcohol polymer having a porous layer inside has been proposed (Japanese Patent Application Laid-Open No. 155-86-1986).
No. 5). However, such hollow fiber membranes are obtained by spinning a solution of a vinyl alcohol polymer, and the pore density per unit volume cannot be increased, and the plasma processing amount per unit area is low. It has the disadvantage that the recovery rate of realbumin, which is small and cannot remove a large amount of pathogenic macromolecules, is low.

Furthermore, polymers that are poorly soluble in solvents and have stretchability, such as crystalline polyolefins and polyamides, and compounds that are partially compatible with the polymers and easily soluble in solvents. A permeable membrane has been proposed that is obtained by forming a mixture of the Special Publication No. 57-20,970). However, since such membranes are stretched to increase the pore size, they not only have low mechanical strength and poor durability, but also have a nearly uniform pore structure on both surfaces and inside the polymer. Because the crystals are coarse, it has the disadvantage that it is difficult to separate components with medium molecular weight or higher, despite the low strength.

Il. OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide a novel flat membrane permeable membrane. Another object of the present invention is to provide a flat membrane type permeable membrane useful for crystal filtration. Still another object of the present invention is to provide a flat membrane type permeable membrane having a controlled pore size that allows a high albumin recovery rate, efficiently removes pathogenic macromolecules, and processes a large amount of plasma.

These objectives are to have a film thickness of 10 to 500 μml,
A flat polyolefin film containing an organic crystal nucleating agent made of an organic heat-resistant substance with a melting point of 150° C. or higher and a gel point higher than the crystallization initiation temperature of the polyolefin used, wherein one of the membranes The surface exhibits a dense layer in which polyolefin fine particles are tightly bound together, and the inside and the other surface exhibit an aggregate layer of independent fine particles with an average particle size of 0.02 to 1.0 μm, forming a labyrinth-like fine communication. This is achieved by a flat membrane type permeable membrane having holes formed therein and both surfaces communicating with each other.

Further, in the present invention, one surface of the membrane and the other surface are
This is a flat membrane type permeable membrane that has an anisotropic membrane structure exhibiting a dense layer with smaller gaps between particles toward one side. Further, in the present invention, the dense layer has a thickness of 3% of the entire film thickness.
It is a flat membrane type permeable membrane with a portion of 0% or less. moreover,
In the present invention, the porosity of the polyolefin membrane is 10 to 60%.
It is a flat membrane type permeable membrane. The present invention is a flat membrane type porous membrane in which the pores of the dense layer have an average pore diameter of 0.01 to 5 μml. The present invention also provides a flat membrane type permeable membrane in which the polyolefin is at least one selected from the group consisting of polyethylene, polypropylene, and ethylene-propylene copolymers.

IIl. Specific Structure of the Invention Next, the present invention will be specifically explained with reference to the drawings. That is, FIG. 1 is a diagram schematically depicting a cross section of a flat membrane type permeable membrane according to the present invention, and as is clear from the figure, the membrane thickness T is 10 to 500 μml, preferably 20 to 3 μml.
This is a flat membrane type polyolefin membrane 1 having a volume of 00 μml.

On one surface side of this flat membrane 1, a dense layer 2 is formed in which fine particles of polyolefin are closely bonded and have fine pores, and the pores have an average diameter of 0.01 to 2 μml.
Preferably it is 0.02 to 0.5 μm. Moreover, the surface is a smooth surface. On the other hand, the average grain size of the inside and other surfaces is 0.
A large number of independent fine particles 3 of polyolefin having a diameter of 0.02 to 1.0 μm form a continuous aggregate layer 4, forming fine communication holes 5 that communicate in a maze-like manner, and both surfaces thereof communicate with each other. Therefore, the dense layer thickness 7 is 30% or less of the total film thickness, preferably 0.1 to 5%. If this dense layer 2 exists, it is preferable that it be thin. In addition, the surface on the opposite side of the dense layer 2 has polyolefin fine particles tightly bonded thereto in almost the same way as the inner surface, and has a relatively large pore size (for example, 0.1 to 5 μm, preferably 0
．． Pores having a diameter of 1 to 2 μm) are formed.

Such a flat membrane type permeable membrane is prepared, for example, as follows. That is, as shown in FIG. 2, a blend 11 of polyolefin, organic filler, and organic crystal nucleating agent
is supplied from the hopper 12 to a kneading machine, for example, a twin-screw extruder 13, where the mixture is melt-kneaded and extruded, and then sent to a T-die 14 where it is discharged in the form of a flat film, and then passed through a cooling roll. 15 to cool and solidify this molten film. Furthermore, after contacting with another cooling roll 16 and a feed roll 17.18 if necessary, a tension roll 19.
It is pulled at 19 and further wound up on a take-up roll 20.

The flat film 21 cooled and solidified in this way is rolled up on a winding roll 20.
After winding it up, it is cut into a predetermined size, and then immersed in an extraction solution to extract and remove the organic filler, and dried if necessary to obtain a flat membrane type porous membrane. Also,
By subjecting the flat porous membrane thus obtained to heat treatment, a flat membrane permeable membrane with even better dimensional stability can be obtained. Moreover, the shape of the surface that contacts the roll depends on the surface shape of the roll. Therefore, if the roll surface is smooth, the roll contact surface of the membrane will also be a smooth surface.

Polyolefins used as raw materials in the present invention include polypropylene, polyethylene, ethylene-propylene copolymer, etc., and their melt index (M,
I, ) is preferably 5 to 70, especially M, I
, is preferably 15 to 65. Among the polyolefins, polypropylene is particularly preferred. As for polypropylene, one having a high degree of crystallinity is preferable. The degree of crystallinity is the weight fraction of crystalline parts relative to the total weight, and is determined by X-ray diffraction, infrared absorption spectrum, density, etc. In general, vinyl polymers -(cH2
-CHRT- can take three steric structures depending on the arrangement of the substituent R: regular actutactic and syndiotactic, and irregular actutic. When the tick ratio is high, crystallization is easy. This also applies to polypropylene.
The crystallinity of polypropylene is determined by the ratio of tactical parts: 1. In other words, the higher the toughness city, the larger it becomes. The polypropylene used in the present invention preferably has a toughness of 97% or more when expressed as toughness, which is an index different from crystallinity.

The organic filler must be able to be uniformly dispersed in the polyolefin while it is melted, and be easily soluble in the extract as described below. Such fillers include liquid paraffin (
(number average molecular weight 100 to 2,000), α-olefin oligomer [e.g., ethylene oligomer (number average molecular weight ff 1100 to 2,000), propylene oligomer (
number average molecular weight 100-2.000), ethylene-propylene cooligomer (number average molecular weight 100-2.000)
etc.], paraffin wax (number average molecular weight 200-2,
500), various hydrocarbons, etc., preferably liquid paraffin.

The blending ratio of the polyolefin and the organic filler is 35 to 3 parts by weight of the organic filler per 100 parts by weight of the polyolefin.
00 parts by weight, preferably 50 to 200 parts by weight. That is, if the organic filler is less than 35 parts by weight, a porous flat membrane with sufficient albumin permeability cannot be obtained;
This is because if the amount exceeds 0 parts by weight, the viscosity becomes too low and the moldability into a flat film deteriorates. Such raw material formulations are prepared (designed) by a premixing 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. .

The organic crystal nucleating agent blended into the raw materials in the present invention has a melting point of 150°C or higher, preferably 200 to 25°C.
It is an organic heat-resistant material whose gel point is 0° C. and higher than the crystallization initiation temperature of the polyolefin used. That is, as mentioned above, it refers to a substance that has a melting point of 150° C. or higher and does not decompose even when melted. The reason for blending such a crystal nucleating agent is to control the pore diameter of the pores formed by the organic filler which is kneaded to reduce the size of the polyolefin particles and which is extracted later. -For example,
For example 1.3.2.4-dibenzylidene sorbitol,
Examples include 1,3.2.4-bis(p-methylbenzylidene) sorbitol, 1.3,2.4-(p-ethylbenzylidene) sorbitol, and the like.

Generally, crystal nucleating agents are used to improve the transparency of molded resins. However, in the present invention, by using the above-mentioned organic crystal nucleation agent, the polyolefin particles are reduced in size to the extent that the pore diameter formed in the membrane is not regulated by the polyolefin particle diameter, and the polyolefin particles are then kneaded. The pores formed by the extracted organic filler can be controlled to a pore size that meets the purpose. The blending ratio of the polyolefin and the organic crystal nucleating agent is 0 parts by weight of the organic crystal nucleating agent per 100 parts by weight of the polyolefin.
．． The amount is 1 to 5 parts by weight, preferably 0.3 to 1.0 parts by weight.

The raw material mixture thus prepared is further melted and kneaded using an extruder such as a twin-screw extruder at a temperature of, for example, 160 to 250°C, preferably 180 to 230°C, and then passed through a T-die into a flat film. The molten material is discharged into a shape, and the molten material is allowed to fall.
It is cooled and solidified by contacting with a cooling roll. The cooling roll is maintained at a predetermined temperature by circulating water or other cooling medium. Cooling temperature at this time (temperature of cooling roll)
is 10 to 100°C, preferably 30 to 80°C. That is, below 10°C, the cooling rate is too fast and phase separation does not proceed sufficiently, resulting in low albumin permeability. On the other hand, 100℃
If this value is exceeded, the crystallization rate of the polyolefin becomes too slow, promoting the adhesion and association of fine particles, which not only lowers the porosity of the membrane, but also makes it impossible to remove pathogenic macromolecules because the microscopic pores become too large. This is because the structure may become easily clogged.

As the extracting liquid, any liquid can be used as long as it does not dissolve the polyolefin constituting the membrane and can dissolve and extract the organic filler. - Examples include alcohols such as methanol, ethanol, propatools, butanols, hexanols, octatools, lauryl alcohol, etc. 1.1.2-) Lichloro 1.2.
2-trifluoroethane, trichlorofluoromethane,
There are halogenated hydrocarbons such as dichlorofluoromethane, 1.1.2.2-tetrachloro-1,2-difluoroethane, etc. Among these, halogenated hydrocarbons are preferable from the viewpoint of extraction ability for organic fillers. In particular, chlorinated fluorinated hydrocarbons are preferred from the viewpoint of safety to the human body.

The flat membrane type permeable membrane thus obtained is further subjected to heat treatment if necessary. The heat treatment is carried out at 50 to 160°C, preferably 70 to 160°C, in an atmosphere of air, nitrogen, carbon dioxide, etc.
at a temperature of 140°C for 1 to 120 minutes, preferably 2 to 60 minutes.
It takes place for a minute. This heat treatment stabilizes the structure of the film and increases its dimensional stability. Further, stretching may be performed before or during this heat treatment.

The flat membrane type permeable membrane thus obtained has a thickness of 10
It is a sheet-like material of ~500 μm, preferably 20 to 300 μm. Its structure is shown in Figure 3 (roll temperature 12
℃), Figure 4 (roll temperature 30℃), Figure 5 (roll temperature 40℃), Figure 6 (roll temperature 50℃), and Figure 7 (roll temperature 60℃), the roll contact The side surface exhibits a dense layer in which fine particles of polyolefin are closely bonded and has fine pores. In addition, the contact surface between the roll and the air on the opposite side is shown in Figure 8 (roll temperature: 12°C).
), Fig. 9 (roll temperature 30°C), Fig. 10 (roll temperature 40°C), kjS11 (roll temperature 50°C) and Fig. 12 (roll temperature 60°C),
Although the fine particles of polyolefin are tightly bound together, pores having a relatively large pore diameter are formed in the dense layer. Furthermore, the inside is as shown in Figure 13 (roll temperature 12°
C), Fig. 14 (roll temperature 30°C), Fig. 15 (roll temperature 40°C), Fig. 16 (roll temperature 50°C) and Fig. 17 (roll temperature 60°C), it is clear that the polyolefin It exhibits an aggregate layer of relatively large independent particles, and the gaps between these independent particles form communicating pores that communicate in a maze-like manner.

Figure 20 shows the roll contact surface (roll temperature °C) for a product without an organic crystal nucleating agent, and the cross section is shown in Figure 2.
In Figure 2, the air contact surface was as shown in Figure 21.

The reason why a film having such an anisotropic structure is formed is considered to be as follows.

A polyolefin kneaded with an organic filler and a crystal nucleating agent is extruded into a sheet, and the extrudate is brought into contact with a cooling roll. Therefore, solidification of the polyolefin sheet extrudate begins at the roll contact surface. and,
Since cooling of the internal and non-contact surfaces is delayed compared to the roll contact surface, phase separation between the polyolefin and the organic filler in the film proceeds by the amount of delay, and the dispersed organic filler converges to some extent. Therefore, it is thought that the permeable membrane of the present invention is formed to have a special structure in which the pores are small on the roll-contacting surface of the membrane, and the pores are large inside the membrane and on the other side. Furthermore, at the roll contact surface, polyolefin particles generated due to contact with the roll are crushed, which is thought to make the difference in structure between the contact surface and other parts more pronounced.

Further, as described above, solidification of the extruded polyolefin starts from the contact surface of the rolls, so the farther from the contact surface the further the solidification is delayed. For this reason, the pores are larger on the non-roll contact surface of the membrane than on the inside of the membrane. Therefore, it is considered that in the permeable membrane of the present invention, the pores become larger from the roll contact surface toward the non-contact surface.

Furthermore, as is clear from the drawings, when the cooling roll temperature is low (quick cooling), the aperture ratio and opening diameter of the roll side surface become smaller, and the hole shape becomes circular. Cooling roll temperature 50~
When the temperature is as high as 60° C., the porosity increases and the pores become interconnected. In other words, when the cooling rate is increased,
Although liquid paraffin becomes a dispersed phase in the surface structure, it can be made closer to a continuous phase by slowing down the cooling rate.

However, if the cooling rate is too slow, phase separation will be promoted and polyolefin molecules will associate with each other, resulting in a decrease in the number of pores. Considering that the liquid paraffin phase becomes pores after extraction, it is desirable that the liquid paraffin phase is a continuous phase, and from the viewpoint of strength, it is also preferable that the polyolefin that is the membrane material be a continuous phase. In this way, conditions are required for both to phase-separate from each other as continuous phases. This is possible within the temperature range mentioned above.

The porosity of the permeable membrane thus obtained is 10 to 60%.
, preferably 30 to 60%.

In addition, in the conventional polyolefin flat membrane manufactured by the stretching method, as is clear from the cross section shown in Fig. 18 and the surface shown in Fig. 19, there are no particles, and pores are formed by the cracks formed by the drawing. has been done.

Furthermore, in the present invention, if a roll having a smooth surface is used, the resulting permeable membrane will have a smooth surface on the roll contacting surface. When plasma or the like is poured onto such a smooth surface, since there are no irregularities on the surface, no turbulence occurs and a uniform flow is formed, and there is less clogging, which is advantageous in terms of fractionation performance, processing capacity, etc.

In this specification, the definition and measuring method of porosity, and the measuring method of average particle diameter and average pore diameter are as follows.

1. Measuring method and definition of porosity After a flat membrane is immersed in ethanol, it is replaced with water to be hydrated, and the porosity when hydrated is measured: Wwet. When the dry weight is Wdry and the density of the polymer is ρg/11, the porosity is calculated by the following formula.

Porosity = 0 volume of pores X100 [%]
Volume of part of polymer + volume of pores = (Wwet Wdry) x 10
0 [:%] Wdry + (Wwct - Wdry) ρ 2, Measuring method of average particle size Scanning electron microscope (manufactured by JEOL: JSM-50A or JSM-840) at a magnification of XI 0.000 or X 3,0
00, the diameters of 50 fine particles were measured and the average was determined.

Average pore diameter: The pore diameter of the pores in the dense layer was determined by measuring the diameters of 100 pores using the above-mentioned scanning electron microscope at a magnification of XI 0,000 (or X 20°, 000) and averaging them.

Next, the present invention will be explained in more detail by giving examples.

Examples 1-3 M, 1. 10 per 100 parts by weight of polypropylene of 23
0 parts by weight of liquid paraffin (number average molecule ff1324)
and 1,3.2 as a crystal nucleating agent in the amounts shown in Table 1.
．． EC-1 or 1.3,2.4-4-dibenzylidene sorbitol, manufactured by Easy Chemical Co., Ltd.
Gelol MD (trade name, manufactured by Shin Nippon Rika Co., Ltd.) consisting of bis(p-methylbenzylidene) sorbitol was charged, melt-kneaded using a twin-screw extruder (PCM-30-25 manufactured by Ikegai Iron Works Co., Ltd.), extruded, and pelletized. . This pellet was heated to 150 mm using a twin-screw extruder (PCM-30-25 manufactured by Ikegai Iron Works Co., Ltd.) 13 using the apparatus shown in FIG.
T-die 14 that melts at ~200°C and has a slit width of 0.61
It is discharged into the air at a discharge rate of 70 g/sin, and is brought into contact with the water on the surface of the cooling roll 15 provided at the bottom thereof, cooled and solidified, and then stretched with a tension roll 19 and 19, and then with a take-up roll 20. I rolled it up. Winding roll 2
1.1. After cutting the sheet material rolled up in step 0 into a fixed length.
Fixed-length extraction was performed by immersing in 2-trichloro-1,2,2-trifluoroethane (hereinafter referred to as Freon 113) twice for 10 minutes at a liquid temperature of 25°C, and then in air at 130°C for 2 minutes. After heat treatment, making it hydrophilic with 50% ethanol water, and washing with water, a flat permeable membrane having the properties shown in Table 1 was obtained.

Comparative Examples 1 to 2 When the same tests as in Example 1 were conducted on commercially available polypropylene flat membrane permeable membranes and polytetrafluoroethylene flat membrane permeable membranes made by the stretching method, the results shown in Table 1 were Obtained.

In the above method, the blue dextran test was conducted as follows. That is, blue dextran 2
00 (manufactured by Pharmacia, weight average molecular weight 2,000
,000) of 0.05 wt% aqueous solution, the transmittance after 7 nights and the initial hourly permeation amount (flux) were calculated as 0.3 kg/
It was carried out under a pressure of cm2.

The porosity P was determined by the following formula.

P= w'xlOO(%)Dlo
, 94+ (W-D) (Formula Φ, W is water content 1, and D is absolute dry weight.) The amount of water permeation is 150% for a membrane with a membrane area of 1.38
Water is permeated under a pressure of m+eHg, and a certain amount (5a+
l) Measure the time it takes to pass through.

As a secondary filter in a plasma separator,
The closer the transmittance in the blue dextran test is to O, the better, and the higher the flux. Also,
Blue dextran Flux/water Flux is preferably high because it means that the membrane is less clogged with solutes.

Evaluation as a membrane is performed by comprehensively evaluating the above factors and the evaluation using bovine plasma, which will be described later.

Using the permeable membranes obtained in Examples 1 and 3 and Comparative Examples 1 and 2, the membrane area was 100 cm2 (5X20 cm).
A module was made, and bovine plasma (albumin: 5.Ig/l, total protein: 9.4g/l) obtained using Terumo Corporation's Plasma Separator 1st filter was mixed at 0.2ml/win using pump l. The plasma was supplied to the module immersed in a constant temperature bath with a liquid temperature of 37° C. via an air chamber at a flow rate of plasma u = 280 cm/win), and the filtrate was circulated to the air chamber at a rate of 70 ml/win using pump II. The filtrate thus obtained was subjected to HPLC (column TSK-G3000SW1 flow rate 1
ml/win, solvent 0.3M-NaCI containing 0. IMS
orcn buffer (pH7゜0)
When quantified by detection at 280 nm (O,D,'), the results shown in Table 2 were obtained.

Examples 4-8 M, I, 10 per 100 parts by weight of polypropylene of 30
0 parts by weight, 150 parts by weight, 174 parts by weight of liquid paraffin (number average molecular ff1324) and EC-1 by 0.0 parts by weight.
A flat permeable membrane was obtained in the same manner as in Example 1 by adding 5 parts by weight. The results of a test similar to Example 1 are shown in Table 3.

Further, when the membranes of Examples 4 to 8 and Comparative Example 1.2 were used to conduct a blood plasma test in the same manner as in Example 1, the results shown in Table 4 were obtained.

Example 9 A membrane was formed using the same method as in Example 4 except that 0.4 parts by weight of EC-1 was added, and a blue dextran test was conducted on the obtained flat membrane type permeable membrane. However, the results shown in Table 5 were obtained (see Figure 16).

Comparative Example 3 A blue dextran test was conducted on a flat membrane type permeable membrane obtained by forming a membrane using the same method as in Example 1 except that EC-1 was not used at all in Example 9. The results shown in the table were obtained (see Figure 22). In addition,
Blue dextran test is Blue Dextran 200
(Manufactured by Pharmacia, weight average molecular weight 200,000) 0.0
The permeability and initial hourly flux of a 5% by weight aqueous solution were measured under a pressure of 0.3 kg/cJ.

The modules used were 02 exchange capacity and CO2
This was done using the same device used to measure exchange capacity.

(Space below) 5 (Table 5 Blue dextran test sample Average particle size Transmittance Flux (μm)
(%) (ml/hr) Implementation 9 0
．． 1-1.0 0 9.1 Comparative example 32.5
~5.0 99 or more 500 or more
A flat film type polyolefin film containing an organic crystal nucleating agent made of an organic heat-resistant substance having a melting point of 150°C or higher and a gelation point higher than the crystallization start temperature of the polyolefin used, which is a wave film. One surface exhibits a dense layer in which polyolefin fine particles are tightly bonded and have fine pores, and the inside and other surface have an average particle size of 0.02 to 1.
Since it is a flat membrane type permeable membrane with an aggregate layer of independent particles of 0 μm forming fine communicating pores that communicate in a labyrinth shape, and both surfaces are connected, the fine communicating pores are formed in the direction of the membrane thickness. They are not linearly penetrating holes, but are a large number of micropores that are formed between the fine particles and connected to each other from one surface through the inside to the other surface. Therefore, when used for plasma separation, it efficiently removes pathogenic macromolecules, has less clogging, has less pressure loss, and has a high albumin recovery rate and is stable over time. Therefore, it is extremely useful as a secondary filter for plasma separation, especially for plasma separation.

In addition, while the stretching method cannot produce a film thicker than about 40 μm, the present invention can produce a thicker film, which improves strength and allows use over a wider surface area. A useful film can be formed.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a flat membrane type permeable membrane according to the present invention;
FIG. 2 is a schematic cross-sectional view of the apparatus used for manufacturing the flat membrane type permeable membrane according to the present invention, FIGS. 3 to 17 are electron micrographs showing the structure of the flat membrane type permeable membrane according to the present invention, and FIG. ~1
FIG. 9 is an electron micrograph showing the structure of a commercially available porous membrane, and FIGS. 20 to 22 are electron micrographs showing the structure of a flat membrane-type permeable membrane containing no crystal nucleating agent. DESCRIPTION OF SYMBOLS 1... Flat membrane type permeable membrane, 2... Dense layer, 3... Polyolefin particles, 4... Continuous particle aggregate layer, 5...
・Communication hole, 11... Compound, 12... Hopper 13
... Extruder, 14 ... T die, 15 ... Cooling roll, 19 ... Tension roll, 20 ... Winding roll, 2
1... flat membrane.

Claims (7)

[Claims] (1) The film thickness is 10 to 500 μm and the melting point is 15
A flat polyolefin membrane containing an organic crystal nucleating agent made of an organic heat-resistant substance whose gel point is above 0°C and whose gel point is above the crystallization temperature of the polyolefin used, one side of the membrane being The fine particles are closely bonded and exhibit a dense layer with fine pores, and the inside and other surface exhibit a continuous aggregate layer of independent fine particles with an average particle size of 0.02 to 1.0 μm, forming a labyrinth-like structure. A flat membrane type permeable membrane in which both sides communicate with each other by forming fine communication holes that communicate with each other. (2) One surface and the other surface of the membrane have an anisotropic membrane structure exhibiting a dense layer with smaller particle gaps toward the one surface.
The flat membrane type permeable membrane described in . (3) The flat membrane type permeable membrane according to claim 1, wherein the dense layer accounts for 30% or less of the total membrane thickness. (4) The flat membrane type permeable membrane according to any one of claims 1 to 3, wherein the polyolefin membrane has a porosity of 10 to 60%. (5) The average pore diameter of the pores in the dense layer is 0.01 to 5 μm
A flat membrane type permeable membrane according to any one of claims 1 to 4. (6) Claim 1, wherein the polyolefin is at least one selected from the group consisting of polyethylene, polypropylene, and ethylene-propylene copolymer.
The flat membrane type permeable membrane according to any one of Items 1 to 5. (7) The flat membrane type permeable membrane according to any one of claims 1 to 6, wherein the surface exhibiting the dense layer is a smooth surface.