JPS62114610A - Method for making porous polyolefin membrane hydrophilic - Google Patents

Abstract

PURPOSE:To carry out treatment for providing hydrophilicity of excellent durability, by heating polymerizing surface active monomer with polymerizable unsaturated link having HLB value of 2-20 and polymerization catalyst that are held on a porous surface of a porous polyolefin membrane. CONSTITUTION:A porous membrane having pores with a diameter of 0.01-5mum using ethylene, propylene, 4-methyl-1-pentene, fluoro-polyolefin, etc. After surface active monomer is held on the porous surface of at least a part of a said porous membrane, said monomer is polymerized by heating. Monomer has a molecular weight of under 10,000, HLB value of 2-20, and polymerizable unsaturated linkages. Hydrophilic part is composed of ethylene oxide, sulfonic acid groups, quaternary ammonium group, etc. After the addition of polymerization catalyst, solution of monomer is pressurized into pores of porous membranes to be polymerized by heating at a temperature of 30-100 deg.C for 1min-5hr.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for making a porous polyolefin membrane hydrophilic, which is used in fields such as water treatment and blood purification.

[Conventional technology]

Polyolefin porous membranes have excellent mechanical properties and chemical resistance, so their application fields are rapidly expanding. However, since polyolefin porous membranes are hydrophobic, it is difficult for water to pass through them as is, and a hydrophilic treatment is required to allow water and other hydrophilic liquids to pass through them.

Various methods have been studied for making polyolefins hydrophilic by surface modification, but in contrast to making porous membranes with complex surface shapes hydrophilic, a simple method for making hydrophilic materials such as film-like materials with smooth surfaces has been proposed. It cannot be applied.

Known methods for making porous polyolefin membranes hydrophilic include organic solvent wetting/water displacement methods, physical adsorption methods, and chemical surface modification methods. The organic solvent wetting/water displacement method involves moistening the entire surface of a polyolefin porous membrane, including the micropores, with an organic solvent that has good compatibility with water, such as alco-p or ketone, and then removing the organic solvent. This method replaces water with water, but in this method, once the water in the pores escapes during storage or use, the area returns to hydrophobicity and becomes unable to pass through, so water is constantly kept around the porous membrane. It is necessary to satisfy the requirements, and handling is complicated. The physical adsorption method is a method in which a hydrophilic substance such as polyethylene glycol or a surfactant is adsorbed onto the surface of a porous membrane to impart hydrophilicity to the porous membrane (for example, Japanese Patent Application Laid-Open No. 153872/1989, Showa 59-2
No. 4752, etc.) and is easy to operate, but it cannot necessarily be said to be a sufficient hydrophilization method because the hydrophilic substance is desorbed during long-term use.

Chemical modification methods include a method in which a hydrophilic monomer is held on the surface of a porous film and then irradiated with radiation (Japanese Patent Application Laid-Open No. 56-58535), or a method in which a hydrophobic resin porous structure is irradiated with radiation. Methods such as plasma treatment in a state impregnated with molecules or surfactants have been proposed (Japanese Unexamined Patent Publication No. 56-157457), but these methods are insufficient to make the pore surface hydrophilic. Hydrophilic treatment cannot be achieved. Further, when radiation irradiation, light irradiation, etc. are carried out, the membrane substrate deteriorates and mechanical strength decreases.

[Problem that the invention seeks to solve]

As mentioned above, in the conventional technology, there are problems such as inconvenience in handling due to temporary hydrophilization, and inability to sufficiently hydrophilize the pore surface.Currently, polyolefin porous No effective method for making membranes hydrophilic has been established.

The purpose of the present invention is to solve the problems of the prior art, and to make it possible to impart highly durable hydrophilicity to almost the entire surface of the pores without reducing the mechanical strength of the polyolefin porous membrane. An object of the present invention is to provide a method for making a porous polyolefin membrane hydrophilic.

[Failure to solve the problem]

The gist of the present invention is to use a monomer having an HLB value of 2 to 2o and having a polymerizable unsaturated bond (hereinafter referred to as a surfactant monomer).
and a method for making a porous polyolefin membrane hydrophilic, characterized by carrying out heating-type polymerization while holding a polymerization catalyst on at least some of the pore surfaces of the porous polyolefin membrane.

Polyolefins used in the polyolefin porous membrane of the present invention include ethylene, propylene, 4-methy/l/
Examples include polymers or copolymers selected from the group such as -1-pentene and 5-methyl-1-butene, and fluorinated polyolefins. Further, the porous membrane can be in any form such as a hollow fiber membrane, a flat membrane, or a tubular membrane, and can have various pore diameters depending on the purpose. Pore diameter is 0.0
Examples include those having a diameter of about 1 to 5 μm.

The surface-active monomer of Kokuu6mei has a hydrophilic part and a hydrophobic part in its molecule, and its x form shows appropriate hydrophilicity and hydrophobicity, and ionicity and nonionicity are problematic. Not be left behind. The molecular weight is not particularly limited, but the permeability into the pores of the porous membrane is taken into consideration (11).The molecular weight is preferably about 10,000 or less, more preferably 5,000 or less.

The surface active monomer of the present invention has an HLB value of 2 to 20.
Any monomer having a polymerizable unsaturated bond can be used. For example, a double bond such as a vinyl bond or an allyl bond or a triple bond such as diacetylene is used as a polymerizable unsaturated bond. In addition, hydrophilic portions include ethylene oxide, phosphoric acid esters, sulfonic acid groups or salts thereof, hydroxyl groups, carboxylic acid groups or salts thereof, quaternary ammonium groups, etc., and hydrophobic portions. Examples include monomers having hydrocarbon chains such as methylene groups, alkyl/L/7A, phenyl groups, vinyl groups, allyl groups, acetylene bonds, and alkylene oxides of 03 or more such as propylene oxide and butene oxide. can.

Specific examples thereof include compounds represented by the following general formulas (1) to αυ, and compounds represented by formulas 04 and (2).

H2C=CR,C00(EO)barR2)m(EO)n
COCR1sCR2(')R2C=CRlCOO(R
2) t(EO)m (R2)nCOCR+ =CR2(
”)H2c=cR, coo(Eo)z(R+)m(EO
) nRs (3) H2C=CR, C○○(”
e )m (Eo)t(R2)rry R3(')R
2C=CR+COO(E O)1(R2)mCOC
IR+ = CR2 (5) H2C Tomi CRICOO ((CH
2)40)kCOCRH=C% (6)H
, C=CRIC00(EO)zPo(OH)OR4(8
)H, C=CR, CH, C0CH, CH(OH)CH2
) hS03M (9)) (, C=CHCH2/
\, H2C=CR,Coo(EO)lCOCR,=CH,(
b) CH3CH, C3c'c3CC0OHUCH3(C
H2),,CTCC=C(CH2)13COONa
03R, , R, , R3, R4, R, , Ma and M are defined as below, but depending on the chain length of ethylene oxide or propylene oxide or the way of selecting alkyl, etc., compounds may be outside the scope of the present invention. However, in the present invention, the chain length of these compounds is appropriately selected and a compound having an HLB value in the range of 2 to 20 is used.

t, m, n, m', klh; integer EO; ethylene oxide R; hydrogen or methyl group R; propylene oxide or a compound of propylene oxide and ethylene oxide R, , R4, R, , R6: carbon number 4 ~20
Alkyl group M; alkali metal The HLBI value of the surface-active monomer in the present invention is 2 to 2.
0, but those in the range of 5 to 15 are particularly preferred. In addition, the HLB value in the present invention is D
The value determined by the method of AVIES (Progress Second International Cong Vs. Surface Activity 1, 426, (1?57)) was adopted.

As the polymerization catalyst in the present invention, various peroxides, azo compounds, redox initiators, etc. known as radio)V polymerization initiators can be used. As an example,
Examples include benzoyl peroxide, dicumyl peroxide, lauroyl peroxide, a combination of azobisisobutylnitrile, a combination of penzoyl peroxide and dimethylaniline, and benzophenone.

In the present invention, the surface-active monomer and the polymerization catalyst are retained on the surface of at least some of the pores of the polyolefin porous membrane, but the polymerization catalyst may or may not be retained at least in part.

As a method of retaining and filtering the surface-active monomer and the polymerization catalyst on the pore surface of the polyolefin porous membrane according to the present invention, various methods can be adopted.
A method using a solution containing a monomer and a polymerization catalyst is simple. That is, a method of preparing a solution in which a surface-active monomer and a polymerization catalyst are dissolved in an organic solvent or water as a solvent, and immersing a polyolefin porous membrane in the le liquid;
Alternatively, a method can be adopted in which a membrane module is manufactured using a porous polyolefin membrane and then this solution is pressurized into the porous membrane.

As the solvent, water or an organic solvent capable of dissolving the surfactant is used, but it is desirable to use a solvent capable of dissolving the polymerization catalyst as well. However, when water is used as a solvent, if the surface-active monomer is dissolved in water in advance, even if the polymerization catalyst is not inherently soluble in water, it will be microdispersed in water due to the surface activity of the additive. Since the polymer acts as if dissolved in water, water can be used as a solvent even when using a polymerization catalyst that does not dissolve in water.

Examples of organic solvents that can simultaneously dissolve the surfactant and the polymerization catalyst include methanol, ethanol, butanol, propano-p1 chloroform, acetic acid, toluene, benzene, acetone, methyl ethyl ketone, methyl isobutyμ ketone, tetrahydrofuran, dimethylacetamide, and dimethyl. Examples include acetamide and dimethyl sulfoxide.

The composition of the surfactant Zumer 1 solvent and polymerization catalyst in the solution is 100 parts by weight of the surfactant Zumer, 50 to 10,000 parts by weight of the solvent, and 0.001 to 10 parts of the polymerization catalyst.
Although conditions of approximately 0 parts by weight can be adopted, 500 to 1000 parts by weight of the solvent to 100 parts by weight of the surfactant
It is more preferable if the amount of the polymerization catalyst (LO) is about 0 parts by weight and about 1 to 30 parts by weight.

Since the surface of a polyolefin porous membrane is hydrophobic, especially when water is used as a solvent, when an aqueous solution containing a surface-active tumer permeates into the side pores, the surface-active tumer will increase its hydrophilicity on the pore surface. Since it is easy to be adsorbed with the groups facing outward, hydrophilicity can be imparted extremely efficiently if this state is fixed by polymerization. Note that it is preferable to use water as a solvent from the viewpoint of workability, working environment, etc.

When an organic solvent is used as the solvent, there are advantages such as the solution permeating into the pores of the polyolefin porous membrane in a short time and the solvent being easily removed from the pores.

Furthermore, even when polymerization is carried out in a state in which the surfactant polymers are randomly oriented on the pore surface without using the above-mentioned oriented adsorption, the formed polymer layer has a lower degree of hydrophilicity than polyolefin. Because of its large size, the pore surface on which the polymer layer is retained is relatively hydrophilic compared to the pore surface where the polymer is not retained, so Can impart hydrophilicity.

When applying the above solution to the polyolefin porous membrane by dipping or press-fitting, the dipping time or press-fitting time is about 0.5 seconds to 50 minutes, and the wetting properties for the polyolefin porous membrane are good. It can be carried out in a shorter time if a suitable solution is used.

In this way, the polyolefin porous membrane retains the surfactant and the polymerization catalyst on at least some of the pore surfaces, and excess liquid in the surroundings is removed, and if necessary, the solvent inside the pores is removed. is removed and then heat treated.

In the present invention, polymerization is carried out by heating a polyolefin porous membrane holding the above-mentioned surface-active monomer and polymerization catalyst. Polymerization methods include methods that use heat, light, or radiation as energy, but when using thermal energy, it is possible to heat even the pores of the porous membrane to a uniform temperature, which increases the surface activity and maintains the surface activity. The point that polymerization can be uniformly carried out on all pore surfaces,
Another feature is that by appropriately setting the polymerization temperature, polymerization can be carried out without changing the structure of the membrane or deteriorating the membrane substrate. On the other hand, when using light energy, one part of the porous membrane is
There is a problem that light does not sufficiently reach the f4Il hole portion, and when radiation energy is used, there is a problem that the simulated substrate deteriorates significantly.

The surfactant polymer retained on the pore surface of the porous membrane is graft-polymerized to the pore surface or polymerized on the pore surface by this heat treatment, so that at least some of the pores are polymerized. The pore surfaces are coated with these polymers. The presence of oxygen in the atmosphere during the heat treatment will significantly inhibit the polymerization reaction, so it is desirable to conduct the heat treatment in an inert gas atmosphere such as a nitrogen atmosphere or in a substantially oxygen-free state such as a vacuum.

The polymerization temperature in the heat treatment is preferably higher than the decomposition temperature of the polymerization catalyst and lower than the temperature that does not change the membrane structure of the porous membrane and damage the membrane substrate, and is usually 50 to 100°C. Temperatures of degrees can be adopted. The heating time depends on the type of polymerization catalyst and the P8 temperature, but is usually about 1 minute to 5 hours, more preferably about 5 minutes to 60 minutes.

After the heat treatment, it is desirable to remove unnecessary components such as unreacted polymers and free homopolymers existing around the porous membrane by a suitable RD strategy. When the polymer formed on the surface of the porous V membrane is an uncrosslinked polymer, it is preferable to use a solvent that dissolves unreacted polymers but does not dissolve the polymer. In addition, when the polymer is a crosslinked polymer, a solvent capable of dissolving unreacted polymers may be used.

In the method for hydrophilizing a polyolefin porous membrane of the present invention,
The amount of the polymer retained on the pore surface is preferably approximately 0.5 to 50% by weight, more preferably 1 to 50% by weight, relative to the frozen amount of the porous polyolefin membrane.
Particularly preferably, the commercial weight is 2 to 15 υ, and approximately (1,2 to 5
It is preferably about 0 m/m", more preferably 0.5 to 20 cape/m", particularly preferably 1.0 to 10
η/door 2.

In the present invention, a monomer with an HLB value of 2 to 20 is used, but when using a monomer with an HLB value greater than 20, the degree of hydrophilicity of the monomer is greater than the hydrophobic polyolefin. Due to insufficient affinity, it is difficult to retain the monomer on the pore surface of the polyolefin porous membrane, and therefore it is also difficult to retain the polymer layer on the pore surface. be. Furthermore, even if a polymer layer is formed on the surface of the pores, the polymer layer is water-soluble and will be dissolved and desorbed during use in water. Furthermore, even if a crosslinked structure is introduced into such a water-soluble polymer to form a water-insoluble crosslinked polymer layer on the surface of the core pores, the crosslinked polymer layer will swell in water, causing problems in the porous membrane. The disadvantage is that the pore size becomes smaller. In addition, monomers with an HLB value of less than 2 have a high degree of hydrophobicity, so they are easily adsorbed on the surface of the porous polyolefin membrane, making it easy to form a polymer layer on the pore surface of the porous polyolefin membrane. However, since the degree of hydrophilicity of the polymer layer is insufficient, it is not possible to substantially impart hydrophilicity.

According to the method for making a porous polyolefin membrane hydrophilic according to the present invention, it is possible to firmly adhere a hydrophilic polymer layer to a porous polyolefin membrane by plot polymerization or an anchor effect. The possibility of the combined layer being desorbed during use is extremely low, and hydrophilicity can be imparted for a longer period of time compared to conventional surfactant adsorption methods.

Furthermore, since a heating polymerization method is adopted as the polymerization method, it is possible to make the porous polyolefin membrane hydrophilic without reducing its mechanical strength.

〔Example〕

The present invention will be specifically explained below using Examples.

In addition, in the examples, the water permeability, water permeability, and water permeability in the alcohol hydrophilization method were determined based on the effective membrane area of 165 c.
The measurement was carried out using a test membrane module of m2 according to the following method. In addition, measurements of the retained amount and surface coverage of the polymer layer and a bending fatigue test were carried out using the following method.

(1) Water permeation pressure: Water at 25°C is supplied from one side of the test membrane module (the inside of the hollow fiber in the case of a hollow fiber membrane) while increasing the water pressure at a rate of α1 / 2 every minute, and the amount of permeated water is increased. is 3
Measure the water pressure when it reaches 0- and 50-. Next, the water pressure is plotted on the horizontal axis and the amount of permeated water is plotted on the vertical axis, and the pressure value at the point where the straight line connecting the two plotted points intersects with the horizontal axis is determined, and that value is taken as the permeable pressure.

(2) Water permeability: Water at 25°C was flowed through one side of the test membrane module P (inside the hollow fiber in the case of a hollow fiber membrane), and the amount of permeated water was measured with the intermembrane pressure differential set to 50 ■Hg. , the water permeability (t/m1·hr·−H, 9) is determined from that value.

(3) Water permeability in Apcor/V hydrophilization method: After moistening with ethanol from one side of the test membrane module μ (inside of the hollow fiber membrane in the case of a hollow fiber membrane) that has not been hydrophilized, 100 water
The water is allowed to flow for 15 minutes at a flow rate of dl min to replace the ethanol present inside the pores with water. Subsequently, water permeability is measured by the method described in (2).

(4) Retention amount of polymer layer The weight % of the polymer layer retained with respect to the unit weight of the polyolefin porous membrane is measured.

(5) Surface coverage ratio Surface tension 5 described in JIS K676B (1971)
The porous membrane was immersed in a standard solution for wetting test (blue) of 4 dyn/3 for 1 minute, air-dried, and 10 cross-sections of the porous membrane were observed with an optical microscope to determine the coloring area relative to the membrane thickness. Determine the thickness ratio (@) and use this as the surface coverage.

(6) Bending fatigue test With a load of 50 g/11 applied to the hollow fiber membrane, the bending angle is set to 90 degrees, and the number of bends until the hollow fiber membrane breaks is determined.

Example 1 Porosity: 68 cm, film thickness: 70 μm, inner diameter: 270 μm, water permeability by alcohol)v hydrophilization method: 1.5 t/m2.
A membrane module with an effective membrane area of 163 cpn'' was fabricated using a polyethylene porous hollow fiber membrane of hr-IIIHg, and a solution having the composition shown in Table 1 was applied from the inside of the hollow fiber membrane of the membrane module at a rate of 7.5 yd/ 10 in min
After being press-fitted for a minute, the membrane module was taken out into nitrogen to remove excess liquid and air-dried for 16 hours in its original state.

Next, the membrane module was placed in a nitrogen atmosphere at 60°C for 3 hours.
A hydrophilic porous membrane was obtained by heating for 0 minutes and then thoroughly washing with acetone.

Subsequently, the amount retained in the polymer layer and the water permeability pressure before and after hydrophilization were measured.

In addition, for the purpose of evaluating the durability of the hydrophilic treatment, a test membrane module after the hydrophilic treatment was used, and the membrane area was 13! Hit Shiro 00
- After draining the water, drying treatment and measuring the water permeability pressure again were repeated 5 times. The water permeability pressure after 5 cycles of washing and drying was exactly the same as before washing and drying, confirming the durability of the hydrophilic treatment of this example.

These results are shown in Table 1.

Examples 2 to 6 Porosity: 68 mm, membrane thickness: 60 μm, inner diameter: 270 μm, water permeability by alcohol hydrophilization method: 1. St/m2・hr・
A polyethylene porous hollow fiber membrane made of Hg was immersed in each solution having the composition shown in Table 1 for 3 seconds each, and then taken out from the solution into nitrogen to remove excess liquid. Next, after air-drying for 16 hours, each porous membrane was heat-treated at 60°C for 50 minutes in a nitrogen atmosphere to retain the polymer layer on the pore surface of the porous membrane, and then thoroughly washed with acetone. A hydrophilized porous membrane was obtained by this, and the retention amount and water permeability of the polymer layer were measured.

For Examples 2 and 4, surface coverage measurements, bending fatigue tests, and durability evaluations were performed.

The surface coverage of the hydrophilized products was 90 to 100% and 95 to 100%, respectively, and it was confirmed that a polymer layer was formed on almost the entire surface of the pores. In addition, the number of bending cycles before breaking was approximately 45,000 and 48,000 times, and the untreated polyethylene porous hollow fiber membrane
.

It was confirmed that there was almost no change in the strength of the porous membrane compared to the previous test. Also, Example 1
When the durability was evaluated by carrying out 5 cycles of water washing and drying in the same manner as above, good results were obtained for all windings.

These results are shown in Table 1.

Example 7 After immersing a polyethylene porous flat membrane with a porosity of 70% and a membrane thickness of 42 μm and a water permeability of A5A/m"·hr-mHg by alcohol hydrophilization method for 5 seconds in a solution having the composition shown in Table 1. The solution was taken out into nitrogen to remove excess liquid, and was further air-dried for 16 hours.

Next, the porous membrane was heat-treated at 70°C for 20 minutes in a nitrogen atmosphere, and then thoroughly washed with acetone to obtain a hydrophilized porous membrane. Water pressure was measured.

These results are shown in Table 1.

Example 8 Porosity: 45 cm, film thickness: 22 μm, inner diameter: 200 μm, water permeability by alcohol hydrophilization method: α8t/m2・hrφ■
After immersing a polypropylene porous hollow fiber membrane of Hg in a solution having the composition shown in Table 1 for 5 seconds, the membrane module /L/
The sample was taken out in nitrogen, excess liquid was removed, and the sample was further air-dried for 16 hours. Next, the membrane module was placed in a nitrogen atmosphere for 80 minutes.
A hydrophilic porous membrane was obtained by heating at .degree. C. for 20 minutes and then thoroughly washing with acetone.

Subsequently, in the same manner as in Example 2, the amount retained in the polymer layer and the water permeability pressure before and after hydrophilization and after 5 cycles of water washing and drying were measured.

These results are shown in Table 1.

Comparative Examples 1 and 2 Using solutions having the compositions shown in Table 1 and using the same conditions as in Example 2, each was subjected to hydrophilic treatment, and the performance was evaluated, and the results shown in Table 1 were obtained.

The permeability pressure is e, 3, 97cm” and 1α7, respectively.
kg/cm'' is a fairly high value, indicating that sufficient hydrophilicity cannot be imparted.

Comparative Example 5 A solution having the composition shown in Table 1 was subjected to hydrophilic treatment under the same conditions as in Example 8, and the performance was evaluated.
Obtained the results in the table. The water permeability pressure was 11.5'Kg/tan2, which is a considerably higher value compared to 0.5Y/cm2 in Example 8, indicating that sufficient hydrophilicity was not imparted.

Comparative Examples 4 and 5 The same polyethylene porous hollow fiber membrane as in Example 2 was immersed in (e!D) having the composition shown in Table 1 for 5 seconds each, then taken out from the solution, excess liquid removed, and air-dried for 16 hours. Next, each porous membrane was placed in a nitrogen atmosphere for 2 hours.
2 kW high-pressure mercury lamps (input 80W/CM+ type)
The surface active material was polymerized by irradiation for 3 seconds from a distance of zero, and then thoroughly washed with acetone to obtain a hydrophilic porous membrane.

Next, the water permeability pressure was measured, and as shown in Table 1, results as good as #1 were obtained. On the other hand, the number of bending cycles until breakage in the bending fatigue test was approximately 500 and 500, respectively. This is significantly smaller than the value of the thermal polymerization amount of the present invention, and it can be seen that the strength of the porous membrane is significantly reduced by the photopolymerization method.

Comparative Example 6 Instead of heating and polymerizing in Example 2, an electron beam irradiation device was used to irradiate the porous membrane with an electron beam at an acceleration voltage of 200 kV, an electron current of 1 mA, and a temperature of 80° C. or less.
Polymerization was carried out by M rad irradiation, and the other conditions were the same as in Example 2 to obtain a hydrophilized porous membrane, and the retained amount and water permeability of the polymer layer were measured, as shown in Table 1. Almost good results were obtained. On the other hand, the number of bending cycles until rupture in a bending fatigue test is approximately 10.
It was 0 times.

It can be seen that when compared with the thermal polymerization method of the present invention, the strength of the porous membrane is extremely reduced in the radiation polymerization method.

Comparative Example 7 The same polyethylene porous hollow fiber membrane as in Example 2 was immersed in a solution having the composition shown in Table 1 for 1 minute, then taken out into the air and air-dried at room temperature for 16 hours to produce a membrane module. The water permeability pressure measured in the membrane module was 1 2 kg 7 m.
” was obtained, and hydrophilicity could be imparted by the Zummer adhesion method on surface activity. However, when a water washing and drying test was conducted once in the same manner as in Example 2, the water permeability pressure was F!-Okg/m2.
rose to It can be seen that the attachment method only imparts temporary hydrophilicity.

(Note 1) H2C-CI(Coo(KO)1□(PO
),, (EO)1. CH.

(Note 2) H, C TSCH COO (KO) 14 COCH-C
H.

(Note 5) H,C-CHCOO((C)!,)40
)s C0CI(-CH.

(Note 4) H,C-CHCOO(PO)so (EO
),,C0CH-CH.

(Note 5) H,C-CHCOO(PO)5゜(EO)
sC0CH-CH.

(Note 6) H2C=CHC00(EO)12 (PO
)2o (EO)12C0CH-CH2 (Note 8) H
2C-C1(C00(PO),,C0CH-CH.

(Note 9) In (Note 1) to (Note 8), (EO) and (p
o) represent ethylene oxide and propylene oxide, respectively.

〔Effect of the invention〕

As is clear from the results of the Examples, by employing the method of the present invention, it is possible to perform hydrophilic treatment with excellent durability without reducing the strength of the polyolefin porous membrane.

Claims (1)

[Claims] A polyolefin having an HLB value of 2 to 20 and characterized in that it is thermally polymerized with a monomer having a polymerizable unsaturated bond and a polymerization catalyst retained on the surface of at least some pores of a porous polyolefin membrane. Hydrophilization method for porous membranes.