JPH022861A - Porous membrane and production thereof - Google Patents

Abstract

PURPOSE:To enhance the heat resistance of a heat resistant porous membrane and to prevent a change in the shape by holding a cross-linked polymer consisting of a specified polymerizable monomer, styrene and divinylbenzene, on the surface of polyethylene to form the porous membrane. CONSTITUTION:A polymerizable monomer A' contg. an acid anhydride or two esterified carboxyl groups and monomers including styrene and divinylbenzene are held on at least part of the surface of a porous polyolefin membrane and heated to form a cross-linked polymer. The acid anhydride or the esterified carboxyl groups in the polymer are then hydrolyzed to produce a hydrophilic porous membrane. The monomer A' and monomers including divinylbenzene may be used in place of the monomer A' and the monomers including styrene and divinylbenzene.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polyolefin porous membrane having excellent heat resistance or excellent heat resistance and hydrophilicity, and a method for producing the same.

[Conventional technology]

In recent years, with the development of industry, various separation membranes have been used in the water purification field, blood treatment field, air purification field, food industry field, etc. For example, VCVi microfiltration membranes are used to obtain highly purified water or highly clean air. Among these, precision filtration membranes made of polyolefins such as polyethylene are inexpensive, have excellent chemical resistance, and are also excellent in membrane properties such as strength, elongation, and flexibility, and are particularly widely used.

The scope of application of microfiltration membranes is increasing, and use at high temperatures of, for example, 80 to 95°C is strongly desired. On the other hand, depending on the use of the microfiltration membrane, it is not acceptable for the inner membrane of the membrane to be contaminated with imitative organisms such as bacteria and phlegm, and in that case, the membrane must be sterilized by some method.

The sterilization method includes ethylene oxide, formalin,
Methods include drugs such as hydrogen peroxide, radiation such as R-rays, and steam heating, but the steam heating method is the most desirable in terms of effectiveness and simplicity, and is usually used12).
A condition of approximately 30 minutes at ℃ is used.

However, porous membranes made of polyolefins such as polyethylene have significant thermal shrinkage, and when these porous membranes are heat-treated or used at high temperatures, their morphology changes and water or air permeability is extremely reduced, resulting in separation. Its function as a membrane decreases.

Furthermore, since this porous membrane is hydrophobic, water cannot pass through it as it is.

2 +) In order to improve the heat resistance of porous olefin membranes, JP-A-62-5587B proposes a method in which a heat-resistant polymer thin film having a crosslinked structure is formed on the surface of a polyolefin hollow fiber membrane. ing. Also, Japanese Patent Application Publication No. 1983
JP-A-57856 proposes a polyethylene porous membrane in which sulfone groups are introduced to impart hydrophilicity.

[Problem to be solved by the invention]

However, in the heat-resistant polyolefin hollow fiber membrane described in JP-A-62-55878, the polymer thin film itself has insufficient β resistance.

Also, the polyethylene porous membrane I/'i described in JP-A-56-57856, which has hydrophilic properties, has sufficient heat resistance.

An object of the present invention is to provide a polyethylene or polypropylene porous membrane with excellent heat resistance that can be subjected to steam sterilization, a polyolefin porous membrane with excellent heat resistance and hydrophilicity, and a method for producing them.

[Problem to be solved by the invention]

The gist of the present invention is that the functional group has an acid anhydride or an esterified carboxyl group, and that the reactivity ratio r and r2 in the copolymerization reaction with styrene are CL30.
The heat-resistant porous membrane has a crosslinked polymer made of the following polymerizable monomer and divinylbenzene or further styrene held on at least a part of the surface of a porous membrane made of polyethylene or polypropylene, and further contains the polymerizable monomer A (hereinafter referred to as "carboxy monomer") A heat-resistant method characterized by thermally polymerizing monomers containing divinylbenzene or styrene while keeping at least a portion of the surface of a porous membrane made of polyethylene or polypropylene. A method for manufacturing a porous membrane.

Further, the gist of the present invention is to prepare a polyolefin porous membrane by using a crosslinked polymer in which monomer units B having two levoxyl groups and divinylbenzene or further styrene are substantially uniformly distributed. The hydrophilic porous membrane is retained on at least a portion of the surface, and
A polymerizable monomer A' having an acid anhydride or two esterified carboxyl groups, and divinylbenzene, or further styrene, are held on at least a portion of the surface of the polyolefin porous membrane, and the porous polyolefin membrane is heat-treated and crosslinked. A method for producing a hydrophilic porous membrane, which comprises forming a polymer and then hydrolyzing the acid anhydride or esterified carboxyl group in the crosslinked polymer.

Polyolefin materials constituting the polyolefin porous membrane used in the present invention include ethylene, propylene,
- Polymers or copolymers whose main component is one or more monomers selected from the group consisting of meth-Iv-1-pentene and 3-methyl-1-butene. b refers to fluorinated products of these. I can do it.

The porous membrane of the present invention can be in any form such as a hollow fiber membrane, flat membrane, or tubular membrane, and can have various pore diameters depending on the purpose. Five preferred examples include a film thickness of approximately 20 to 200 μm, a porosity of approximately 20 to 90 μm, and a water permeability in the alcohol-7L/hydrophilization method of (L OQ i ~1017 m” h
Examples include those with a pore diameter of about 11L01 to 5 μm.

The porous membrane may have a pore structure obtained by various methods, including a method in which the membrane is melt-shaped and then stretched, or a method in which an inorganic substance or ester is mixed in and the stretched product is extracted after melt-shaping. Among these, porous membranes obtained by a method of melt-forming and then stretching are preferably used because they have a large porosity and are less likely to deteriorate in performance due to clogging. In the porous membrane obtained by the method of melt-forming and then stretching, slit-like micro spaces (pores) formed by microfibrils and knots communicate with each other three-dimensionally. It is a porous membrane having a pore structure, for example,
2) It can be produced by the method described in Publication No. 23, Japanese Unexamined Patent Publication No. 57-42919, etc.

Further, as the form of the porous membrane, a hollow fiber type is preferably used because the membrane area per unit volume is large.

In the heat-resistant porous membrane of the present invention, a carboxy monomer whose reactivity ratios r1 and r2 with styrene are both (L30 or less) is used, and rl and r are values defined as follows.

r1=Kp(day t-8t)/Kp(8t-Oa
)rl=Kp(Oa-Ca)/Kp(8t-Oa
) However, xp(st-st): Reaction rate between styrene monomers [
p(at-Cia): Reaction rate between styrene monomer and carboxy monomer Kp(Oa-Oa): Reaction rate between carboxy monomer.

Examples of the carboxy monomer (m-combinable 4-mer A) include maleic anhydride, itaconic anhydride, hymic anhydride, maleic ester, and tuma V-acid ester.

Also, among these, maleic anhydride, maleic acid di-n
-propyl, di-1-propyl maleate, di-2-ethyM hexyl maleate, di-n-butyl maleate, di-t-buty-M maleate.

Particularly preferred examples include di-n-propyl fumarate, di-1-propy-V fumarate, di-n-butyl fumarate, t-butyl fumarate, dicyclobenzene fumarate, synchlohexyl fumarate, and di-2-ethylhexyl fumarate. − is.

A cross-linked polymer consisting of divinylbenzene alone or a two-component system of styrene and divinylbenzene can impart a certain degree of heat resistance to the porous membrane, but monomers containing esterified V-poxy V groups Since the crosslinked polymer contained therein has excellent heat resistance, when this is used, the same level of heat resistance can be imparted to the porous membrane with a smaller retained amount than the former. Therefore, heat resistance can be imparted while suppressing a decrease in the porosity of the porous membrane as much as possible.

In addition, the reactivity ratio rl and r2 of the carboxy monomer in the copolymerization reaction with styrene are both 0.30 or less, and in the crosslinked polymer, each monomer component is distributed at an almost constant ratio at the molecular level M, and the block copolymerization Since no polymer is formed, this crosslinked polymer exhibits approximately constant physical properties in each component.

The acid anhydride or esterified carboxyl group of this force V poxy monomer is converted to force M box V by alkaline hydrolysis.
Since it can be changed to /L/ group, hydrophilicity can be easily imparted as needed.

Divinylbenzene, which is a raw material for the crosslinked polymer, is industrially available as a mixture of 55 to 6 otl of divinylbenzene, 35 to 40% of divinylbenzene and 10 tl or less of saturated compounds. It is possible to use a cold-temperature compound such as Hako, or a compound with further improved purity.

In the hydrophilic porous membrane of the present invention, each monomer unit constituting the crosslinked polymer retained on the surface of the porous membrane is used to impart heat resistance to the porous membrane, and the monomer unit having two carboxyl groups is used to impart heat resistance to the porous membrane. Unit B (hereinafter referred to as "dicarboxylic acid unit") is used to impart hydrophilicity to the porous membrane.

In this crosslinked polymer, the dicarboxylic acid units are substantially uniformly distributed, and "substantially uniformly distributed" means that the monomer units are substantially uniformly distributed at the molecular level without forming a block copolymer. It means that it is evenly distributed. Therefore, each part of the crosslinked polymer exhibits hydrophilicity evenly.

Examples of such dicarboxylic acid units are maleic acid,
Examples include monomer units having structures such as Tuma V acid, itaconic acid, and Himic acid.

Furthermore, it is particularly preferable that this crosslinked polymer has a structure in which dicarboxylic acid units are substantially alternately bonded with divinylbenzene or styrene, and the dicarboxylic acid units forming such a structure include maleic acid, divinylbenzene, and styrene. Examples include those having the structure.

In the porous membrane of the present invention, the surface of at least a portion of the porous membrane on which the heat-resistant or hydrophilic crosslinked polymer is retained is:
b refers to all of the pore surface and part of the outer surface. That is,
It is only necessary that the crosslinked polymer is maintained in such a way that the heat resistance is substantially improved, or furthermore, it has hydrophilicity to the extent that water can permeate through the normally used transmembrane pressure. 4. It is not necessary that the crosslinked polymer be retained on all surfaces.

Retained means that the cross-linked polymer is strongly bonded or adhered to the pore surface to the extent that it does not easily detach during storage or use, and the cross-linked polymer is chemically bonded to the pore surface. Alternatively, the crosslinked polymer may be closely attached to the micropores by an anchor effect, or the crosslinked polymer may be held by a chemical bond or an anchor effect in combination.

Special K: When a porous membrane made porous by the above-mentioned stretching method is used, a crosslinked polymer is formed to wrap around the microfibrils and can be held firmly. It is preferable to use a porous material.

The amount of heat-resistant or hydrophilic cross-linked polymer retained on the surface depends on the composition of each compound (unit), the porosity and pore diameter of the porous membrane, but it depends on the iK of the porous membrane. Approximately 5-8
Preferably, the culm is 0% by weight. If the amount of crosslinked polymer retained is less than this range, it will not be possible to impart sufficient heat resistance or even hydrophilicity to the porous JtM, and even if it exceeds this range, the porous membrane will not have sufficient hydrophilicity or heat resistance. This is not preferable because the pore volume may be reduced and the fluid permeation performance may be lowered, rather than being improved further.

The holding weight of the crosslinked polymer is more preferably about 10 to 70 weights, particularly preferably about 15 to 60 weights.

Molar composition ratio Dvn of divinylbenzene (DvB) and styrene (st), which are monomer units constituting the crosslinked polymer
/st may be 1/20, and the sum of DVD and St and polymerizable monomer A (or monomer unit B) (7) 7v composition ratio (vvya+s t )/polymerizable monomer A (or monomer unit B) is It should be about 1/1 to 2/1,
More preferably, it is about 1/1 to 1,571.

The method for manufacturing the heat-resistant porous membrane invented by Tsugi Eki will be explained.

In the present invention, various methods can be employed to retain the crosslinked polymer on the surface of the porous membrane.

For example, a method in which a solution is prepared by dissolving monomers or a polymerization initiator if necessary in a suitable solvent, and the porous membrane is immersed in the solution, or after the membrane module V of the porous membrane is manufactured. A method can be adopted in which the porous membrane is impregnated with the solution by, for example, a method of pressurizing the solution into the porous membrane, the solvent is removed by evaporation, and then the monomers are polymerized. When a solution diluted with a solvent is used, the monomers can be almost uniformly deposited over the entire porous membrane without clogging the pores of the porous membrane. Further, by changing the concentration of the monomers in the solution and the immersion time, the adhesion 1 of the cymonomers can be adjusted.

When preparing the above solution, an organic solvent is used that has a boiling point lower than that of the monomers and is capable of dissolving the monomers, but when adding a polymerization initiator, the polymerization initiator is It is preferable to use a solvent in which it can be dissolved.

Such organic solvents include methanol, ethanol,
Examples include alcohols such as propatool and isopropatool; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; ether Vs such as tetrahydrofuran and dioxane; ethyl acetate and chloroform.

The boiling point of the organic solvent is not particularly limited, but in view of ease of solvent removal before the polymerization step, it is preferably about 100°C or less, more preferably about 80°C or less.

The composition of the monomers and the solvent in the solution may be selected appropriately taking into account the type of solvent and the amount of crosslinked polymer to be retained, etc., and the IJ ratio is 50 to 10,000 parts by weight for 100 parts by weight of the monomers. As long as it is about 200 to 5 parts by weight
More preferably, the amount is about 1,000 parts by weight.

It is preferable to set the composition ratio of monomers in the solution in consideration of the boiling point, vapor pressure, or target retention amount of the crosslinked polymer of each compound, and the monomer composition ratio in the target crosslinked polymer. It is preferable to increase the proportion of low boiling point components such as divinylbenzene (I) VB) and styrene (St). That is, the monomer composition ratio (DV
B+day 1)/polymerizable monomer A ratio is preferably about 1/1 to 10/1 (mol).

Incidentally, once the combination of monomers is determined, the ratio of each monomer component in the crosslinked polymer is determined from the reactivity ratio thereof. Therefore, when the value of the monomer composition ratio of (DVD + 8t) is increased, the amount of crosslinked polymer retained depends on the monomer concentration of polymerizable monomer A, which is a high boiling point component, so the amount of retained crosslinked polymer can be controlled by K. I can do it.

When dipping or press-fitting porous membranes with these solutions, the immersion time or id IEE time is about α5 seconds to 30 minutes, and it is recommended to use solutions that have good cutting properties for porous membranes. The more you have, the faster it can be done.

In this way, the porous membrane in which the monomers or the polymerization initiator are retained on at least a portion of its surface is removed from the surrounding excess liquid and, if necessary, the solvent inside the pores is removed by evaporation. After that, it is transferred to the next polymerization step.

If the temperature during evaporation of the solvent is too high, polymerization will partially proceed while the solvent remains, and polymerization will occur inside the pores of the porous membrane instead of on the pore surface, resulting in some pores being removed. This is not preferable because the solvent may become clogged. Considering this, it is preferable that the temperature at the time of solvent removal is approximately 10 to 50°C.

In the present invention, polymerization methods such as thermal polymerization, photopolymerization, and radiation polymerization can be employed, and known polymerization initiators can be used.

In the case of the photopolymerization method, ultraviolet rays or visible light can be used as the light source for light irradiation, and the ultraviolet ray sources include low-pressure mercury lamps,
High-pressure mercury lamps, xenon lamps, arc lamps, etc. can be used. Further, in the case of radiation polymerization, it can be carried out by using, for example, an electron beam irradiation device.

In the case of the thermal polymerization method, the polymerization temperature is desirably higher than the decomposition temperature of the polymerization initiator and lower than the temperature that does not change the membrane structure of the porous membrane and damage the membrane substrate; A temperature of about 30 to 100°C can be employed. Although the heating time depends on the type of polymerization initiator and the heating temperature, in the patch method, it is usually about 1 minute to 5 hours, preferably 15 minutes [IV about 1 to 3 hours.

Further, in the continuous method, since the heat transfer efficiency is high, polymerization can be carried out in a shorter time than in K, and the heating time is usually about 10 seconds to 60 minutes, more preferably 20 seconds to 10 minutes.

In addition, during these polymerizations, the presence of oxygen in the atmosphere will significantly inhibit the polymerization reaction, so polymerization should be carried out in an inert gas atmosphere such as a nitrogen atmosphere, or in a situation where oxygen is substantially absent, such as in a vacuum. is desirable.

In the present invention, a monomer containing a levoxy monomer is used.
Because of the use of divinylbenzene, the polymerization rate is significantly higher than that of divinylbenzene alone or a two-component system of styrene and divinylbenzene. Furthermore, since the boiling point of the -carboxy monomer is high and the vaporization temperature is low at the polymerization temperature, the crosslinked polymer for the porous membrane when the monomer concentration of the solution is the same is compared to a single system of divinylbenzene or a two-component system of styrene and divinylbenzene. This has the advantage that the retained amount is increased and the yield is improved.

In the present invention, various polymerization methods can be employed as described above, but a method using thermal energy is most preferred. When thermal energy is used, the pores of the porous membrane can be heated to a uniform temperature, so monomers can be uniformly polymerized on all the pore surfaces where monomers are held. By setting the polymerization temperature appropriately, there is an advantage that polymerization can be carried out without changing the membrane structure or deteriorating the membrane substrate. On the other hand, when using light energy, there is a problem that light scattering makes it difficult for light to reach the pores of a porous membrane, and that increasing the intensity of light irradiation tends to cause deterioration of the membrane substrate. Also, when using radiation double energy, there is a problem in that the membrane substrate tends to deteriorate. Therefore, when employing these polymerization methods, it is necessary to carefully select polymerization conditions that will not degrade the membrane substrate.

Since the monomers held on the surface of the porous membrane are polymerized and crosslinked by these polymerization techniques, at least a portion of the surface of the porous membrane is coated with these crosslinked polymers.

After the crosslinked polymer is produced, unreacted monomers and free polymers existing around the pore surface and outer surface of the porous membrane are removed by dipping or press injection using an appropriate cleaning solvent as necessary. It is desirable to remove the components.

Although each step has been explained separately above, in the present invention, it is also possible to carry out the retention of monomers, etc. on the surface of the porous membrane, solvent removal, polymerization, washing after polymerization, etc. almost continuously.

Next, the method for producing the hydrophilic porous membrane of the present invention will be explained.

The hydrophilic porous membrane is produced by retaining a cross-linked polymer on at least a portion of the surface of the polyolefin porous membrane in the same manner as the manufacturing method of the heat-resistant porous membrane, and by hydrolyzing the cross-linked polymer to introduce carboxyl groups. It can be obtained from K.

The polymerizable monomer A', which has an acid anhydride or two carboxy V groups each esterified, has high reactivity with divinylbenzene and styrene, and the reaction rate is significantly higher than the polymerization reaction between divinylbenzene and styrene. This means that the polymerizable monomer A' is substantially uniformly distributed at the molecular level in the resulting polymer.

Furthermore, since the polymerizable monomer A' can be easily converted into a carboxyne V group by hydrolysis, it can impart hydrophilicity to the crosslinked polymer.

As the polymerizable 7-mer A', the reactivity ratio with styrene rl
and r2 are both α30 or less, and
The same polymerizable monomers as A can be mentioned.

In order to uniformly hydrolyze the crosslinked polymer held on the pore surface of the porous membrane, a heating method is preferable, but in that case, the thermal and chemical stability of the polyolefin and the held crosslinked polymer is It becomes a problem. For this reason, it is preferable to prepare a dicarboxylic acid salt by immersing a porous membrane in a solution in which an alkaline substance is dissolved in a solvent system with a low surface tension.

Examples of alkaline substances include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide, carbonates, and ammonia, with concentrations of a,
It may be about 1 to 2 regulations. As the solvent, methanol, ethanol-V, isozolopanol, or a mixed solution of these and water can be used. The immersion time may be 5 minutes or more.

〔Example〕

The present invention will be specifically explained below using examples.

In the examples, the porous membranes were all porous membranes in which slit-like spaces (pores) formed by knots and microfibrils obtained by melt-forming and stretching were connected three-dimensionally. A membrane was used.

The amount of crosslinked polymer retained was determined by a dissolution fractionation method in which the porous membrane was dissolved under reflux of boiling xylene and was expressed as a weight relative to the porous membrane. The heat shrinkage rate was measured by treating the porous membrane in steam at 12)° C. for 30 minutes and using the shrinkage before treatment as a reference. Further, the water permeability and water permeability pressure were measured by the following method using a test membrane module with an effective membrane area of 163 mm.

(1) Water permeability: 25 t of ethanol from one side of the test membrane module V (inside the hollow fiber membrane in the case of a hollow fiber membrane)
After applying pressure for 15 minutes at a flow rate of d/min to sufficiently wet the inside of the pores of the porous membrane with ethanol, water was added at a rate of 10 min.
The water is allowed to flow for 15 minutes at a flow rate of 0 ml/win to replace the ethanol-V present inside the pores with water. Next, from one side of the test membrane module V (inside of the hollow fiber in the case of hollow fiber) 2
Measure the amount of permeated water at iH with a transmembrane pressure difference of 50 m by flowing water at 5°C, and use that value to determine the water permeability (17 m”/hr).
-mHg).

(2) Water permeability EE = Water permeability from one side of the test membrane module (inside of the hollow fiber in the case of a hollow fiber membrane) every 1 minute (11#/-
Supply water at 25℃ while raising the rice field at a rate of y,
Measure the water pressure when the cumulative amount of permeated water becomes 30- and 50 WtK. 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.

Examples 1 to 5 As a porous membrane, the porosity is 65%, the membrane thickness is 70 μm, the elongation at break is 67, the heat shrinkage rate is 41%, and the water permeability by alcohol hydrophilization method is 1.2) 7 m"・hr・sang A porous membrane made of polyethylene was used.

This porous membrane was immersed for 10 seconds in an acetone solution containing styrene, divinylbenzene, maleic anhydride at the concentrations shown in Table 1, and benzoyl peroxide at a concentration [L2 weight], and then air-dried at room temperature for 50 minutes. The acetone was volatilized, and the monomers were polymerized by heating in a nitrogen atmosphere at 60° C. for 20 minutes to obtain a porous membrane in which the crosslinked polymer was retained on the pore surface.

The polymer retention amount, breaking elongation, water permeability, and heat shrinkage rate of these porous membranes were measured and are shown in Table 1.

Further, when the condensed water of the water vapor used for measuring the heating shrinkage rate was evaluated using a UV absorption photometer, no eluted components were detected.

In addition, the reactivity ratio of styrene and maleic anhydride is r1=α0
1, r = 0.

Comparative Example 1 Maleic anhydride was not used, other conditions were Example 6
It was conducted and evaluated in the same manner. Compared to the case of Example 3, the polymerization rate is slow, so the amount of polymer retained is CL085f.
/117, and the heat shrinkage rate was large.

Comparative Example 2 The polymerization time was 90 minutes, and the other conditions were the same as in Comparative Example 1. Although the amount of polymer retained increased as the polymerization time was increased, the value of the heat shrinkage rate was large compared to the amount retained.

Examples 6 to 11 Porous membrane with porosity of 70, membrane thickness of 55 μm, and inner diameter of 27
0μm, elongation at break 43, heat shrinkage rate 45 candy, water permeability by alcohol hydrophilization method 4.5t/m"・hr-m
A porous hollow fiber membrane made of polyethylene made of Hg was used.

While continuously supplying this porous membrane, styrene, divinylbenzene, maleic anhydride at the concentrations shown in Table 1, and bis-(4-t-butylcyclohexyl) peroxydicarbonate ( Made by Kayaku Nouri ■
In an acetone solution containing Vercadox 16) [12
After dipping for seconds, the membrane was run for 5 minutes on a heated surface at 85°C with nitrogen flowing at a flow rate of 3 L/min to polymerize the monomers, forming a porous membrane with crosslinked polymers retained on the pore surface. Obtained.

The polymer retention, breaking elongation, water permeability, and heat shrinkage of these porous membranes were measured and shown in Table 1.

Examples 12 to 17 In Example 6, the results shown in Table 1 were obtained in the same manner as in Example 6 except that di-n-butyl fumarate was used in an amount equivalent to the amount of water in Table 1 in place of maleic anhydride.

In addition, the reactivity ratio #ir of styrene and di-n-butyl fumarate
1 = (L j 5, r2=0.

Examples 18 to 20 As a porous membrane, the porosity is 40 cm, the film thickness is 22 μm, and the inner diameter is 20 μm.
0μm, elongation at break 102mm, heat shrinkage rate 28%, water permeability by alcohol hydrophilization method α2417m”・hr
-mHg, a polypropylene porous hollow fiber membrane was used.

This porous membrane bundle was continuously fed to produce 0 degrees of styrene, divinylbenzene, maleic anhydride, and concentration Q, 5% by weight of 2.2)-azobis(4-methoxy-2) shown in Table 1. ,4-dimethylvaleroni) +7 /L/) (V2O manufactured by Wako Tsumugi Pharmaceutical Co., Ltd.) in an acetone solution containing
After being immersed for seconds, the membrane was run through a heated surface at 85°C through which nitrogen was flowing at a flow rate of 3 t/mtn to polymerize the monomers, yielding a porous membrane in which the crosslinked polymer was retained on the pore surface.

The polymer retention, breaking elongation, water permeability, and heat shrinkage of these porous membranes were measured and shown in Table 1.

Examples 2) to 24 Porous membranes were obtained using the monomers shown in Table 2 and the other conditions were the same as in Example 1, and the performance thereof is shown in Table 2.

Examples 25 to 31 Porous membranes were obtained using the monomers listed in Table 2 and other conditions similar to those of Example 6, and the performance thereof is shown in Table 2.

Example 32 A porous membrane was obtained using the monomers shown in Table 2 and other conditions were the same as in Example 3, and its performance is shown in Table 2.

Examples 33 to 37 A porous membrane in which a crosslinked polymer obtained under the same conditions as in Examples 1 to 5 was retained on the pore surface was hydroxylated using ethanol with a concentration of +7 um of 0.1N. It was immersed in the solution for 3 hours and then washed in running water for 30 minutes.

The amount of polymer retained, elongation at break, water permeability, water permeability and heat shrinkage of the porous membrane thus obtained were measured and shown in Table 3. Furthermore, when the condensed water of the water vapor used for measuring the heat shrinkage rate was evaluated using a σV@photometer, no eluted components were detected.

Examples 38 to 41 A porous membrane in which a crosslinked polymer obtained under the same conditions as in Examples 6 to 9 was retained on the pore surface was prepared using a porous membrane having a concentration of sodium hydroxide (15 N ethanol/water (9515 vol). H) A porous membrane of the present invention having the heat resistance and hydrophilicity shown in Table 3 was obtained by immersing it in the mixed solution for 5 minutes and washing it in water for 30 minutes.

Examples 42 to 47 A porous membrane in which a crosslinked polymer obtained under the same conditions as in Examples 12 to 17 was retained on the pore surface was hydroxylated under the same conditions as in Example 38) IJum solution A porous membrane having the performance shown in Table 3 was obtained.

Examples 48 and 49 Porous membranes obtained under the same conditions as in Examples 19 and 20, in which the crosslinked polymer was retained on the pore surface, were hydroxylated in the same manner as in Example 38) and treated with +3um solution. A porous membrane having the performance shown in Table 3 was obtained.

Examples 5Q and 51 Poly4-methylpentene-1 (manufactured by Mitsui Petrochemicals TP)
XRT18) was melt-spun using a double cylindrical hollow fiber production nozzle I at a spinning temperature of 2500 and a spinning draft of 500, and then subjected to constant length heat treatment at 140°C for 2 minutes and then heated at 25°C for 1 hour.
．． By stretching 8 times, then stretching to 25 times at 130°C, and further relaxing and heat setting at 140°C until the total stretching ratio becomes 2-0 times, the water permeability by alcohol hydrophilization method is cL15t. /m2・hr-+llllHg, porosity: 32, inner diameter: 250 μm%, membrane thickness: 20 pm, water permeability: 1
8k! A porous hollow fiber membrane of i//cm2 was obtained.

While continuously supplying this porous membrane, styrene, divinylbenzene, maleic anhydride or di-n-butyl fumarate at the concentrations shown in Table 1, and Perforce Dox 16 at a concentration α2 double f1% are dissolved. After immersing the tube in an acetone solution for 12 seconds, the tube was run for 5 minutes in heated rain at 85°C with nitrogen flowing at a flow rate of 3 L/min to remove the monomers.
(A porous membrane in which the crosslinked polymer was retained on the pore surface was obtained.

These porous membranes were then coated with potassium hydroxide at a concentration of 15
The porous membrane was immersed in a specified ethanol-V/water (9515 VOW LII) mixed solution for 5 minutes and further washed in water for 30 minutes, thereby obtaining a porous membrane having the performance shown in Table 3.

Examples 52 to 54 The same porous polyethylene membrane as in Example 1 was used, and the monomers listed in Table 4 were used, and the other conditions were the same as in Example 1. The porous membrane was retained on the pore surface and then treated with a sodium hydroxide solution under the same conditions as in Example 33 to obtain a porous membrane having the performance shown in Table 4.

Examples 55 to 57 The same porous polyethylene membrane as in Example 6 was used, and the monomers listed in Table 4 were used, and the other conditions were the same as in Example 6. I
A porous membrane having the performance shown in Table 4 was obtained by treatment with Jum solution.

Examples 58 to 60 In Example 57, di-n-buty-V fumarate was used in the amount shown in Table 4 in place of maleic anhydride, and the results in Table 4 were obtained in the same manner as in Example 57 except for that. .

Examples 61 and 62 The crosslinked polymer was maintained on the pore surface of the porous membrane under the same conditions as in Example 18, and then hydroxylated under the same conditions as in Example 38) IJum solution treatment, A porous membrane having the performance shown in Table 4 was obtained.

Examples 66 and 64 A porous membrane made of poly-4-methylpentene-1 similar to that in Example 50 was used as the porous membrane, and monomers from Table 4 were used, and the other conditions were as in Example 50. In the same manner, the crosslinked polymer was retained on the pore surface of the porous membrane, and then treated with a potassium hydroxide solution under the same conditions as in Example 5.
A porous membrane having the performance shown in the table was obtained.

〔Effect of the invention〕

As is clear from the results of the Examples, the heat resistant porous membrane of the present invention has significantly improved heat resistance as compared to ordinary polyethylene porous membranes and polypropylene porous membranes. That is, the porous membrane retaining the crosslinked polymer of the present invention shows almost no change in form or decrease in water permeability even after steam treatment at 12)°C.

Further, the monomers used in the method of the present invention have a high reaction rate, so that a crosslinked polymer can be formed in a short period of time. Furthermore, since a carboxy monomer with a low boiling point is used in combination, the yield of the crosslinked polymer retained in the porous membrane is high, and the crosslinked polymer can be retained more uniformly on the surface of the porous membrane. Furthermore, the retention jλ of the crosslinked polymer can be easily controlled.

Furthermore, the hydrophilic porous membrane of the present invention has significantly lower water permeability pressure than an untreated polyolefin porous membrane. Also, 12
Even after steam treatment at )°C, the shrinkage rate is small and there is almost no change in form, and it has excellent heat resistance.

According to the method of the present invention, since the polymerization rate is high, a crosslinked polymer can be retained on the surface of a porous polyolefin membrane in a short time, and furthermore, this crosslinked polymer can be easily imparted with hydrophilicity by hydrolysis treatment. be able to.

The porous membrane of the present invention can be applied to membrane separation applications that require steam sterilization in the medical, food, and fermentation industries, as well as high-temperature water treatment such as polysaccharide purification and condensate treatment in power plants. Furthermore, it can be applied to animal and plant culture, adsorption separation of proteins, membrane chromatography, etc.

Claims (8)

[Claims] (1) Polymerizable monomer A having an acid anhydride or esterified carboxyl group as a functional group and having reactivity ratios r_1 and r_2 of copolymerization reaction with styrene of 0.30 or less, styrene and A heat-resistant porous membrane in which a crosslinked polymer made of divinylbenzene is held on at least a part of the surface of a porous membrane made of polyethylene or polypropylene. (2) A method for producing a heat-resistant porous membrane, in which monomers containing polymerizable monomer A, styrene, and divinylbenzene are thermally polymerized while being retained on at least a portion of the surface of a porous membrane made of polyethylene or polypropylene. (3) A heat-resistant porous membrane according to claim 1, in which a crosslinked polymer consisting of polymerizable monomer A and divinylbenzene is retained instead of the crosslinked polymer consisting of polymerizable monomer A, styrene, and divinylbenzene. (4) A method for producing a heat-resistant porous membrane according to claim 2, using monomers containing polymerizable monomer A and divinylbenzene instead of monomers containing polymerizable monomer A, styrene, and divinylbenzene. (5) A crosslinked polymer in which monomer units B having two carboxyl groups, styrene and divinylbenzene are monomer units, and monomer units B are substantially uniformly distributed is held on at least a portion of the surface of the porous polyolefin membrane. hydrophilic porous membrane. (6) An acid anhydride or a polymerizable monomer A' each having two esterified carboxyl groups, monomers containing styrene and divinylbenzene are retained on at least a part of the surface of the porous polyolefin membrane. A method for producing a hydrophilic porous membrane, which comprises heat-treating to form a crosslinked polymer, and then hydrolyzing the acid anhydride or esterified carboxyl group in the crosslinked polymer. (7) Monomer unit B having two carboxyl groups = divinylbenzene as a monomer unit, and a crosslinked polymer in which monomer units B are substantially uniformly distributed is held on at least a part of the surface of the porous polyolefin membrane. Hydrophilic porous membrane. (8) A method for producing a hydrophilic porous membrane according to claim 6, using monomers containing polymerizable monomer A' and divinylbenzene instead of monomers containing polymerizable monomer A', styrene, and divinylbenzene. .