JPS60153903A - Ultrafiltration membrane and its preparation - Google Patents

Abstract

PURPOSE:To enhance water permeability without lowering membrane strength, by using a hydrophobic polymer in which hydrophilic silica is substantially uniformly dispersed. CONSTITUTION:Hydrophilic silica is dispersed in an aprotic polar solvent and a hydrophobic polymer is added to and dissolved in the resulting dispersion to prepare a spinning stock solution. As the hydrophobic polymer, polyvinylidene halide or polyvinyl halide is used and hydrophilic silica is dispersed in the solvent in a ratio of 1-30wt% of the hydrophobic polymer. Generally, hydrophilic silica with a particle size of about 1mum or less is used but it is pref. to use said silica after treating the surface thereof with a coupling agent for enhancing compatibility with the hydrophobic polymer. A membrane is formed by a usual method but drying and the heat treatment in an acidic aqueous solution are pref. applied.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrafiltration membrane and a method for producing the same. More specifically, the present invention relates to an ultrafiltration membrane that improves membrane performance, particularly water permeability, without reducing the membrane strength of the porous membrane, and a method for producing the same.

Conventionally used ultrafiltration membranes, especially hollow fiber ultrafiltration membranes, are made of hydrophobic membranes such as polyvinylidene halides, typified by polyvinylidene fluoride, and polyvinyl halides, typified by polyvinyl fluoride. It is generally produced by a dry-wet spinning method. In the dry-wet spinning method, a hydrophobic polymer is dissolved in a solvent and the
A spinning stock solution with a concentration of 1% is prepared, and it is discharged from a hollow annular nozzle and allowed to fall naturally for about 1 to 100 cm, and then introduced into a gel bath made of a non-solvent of a hydrophobic polymer for coagulation. The company manufactures hollow fibers. At this time, in order to maintain the hollow structure of the membrane, a core liquid is simultaneously injected from the center of the annular nozzle, and the porous structure and skin layer of the hollow fiber membrane are discharged from the nozzle and immersed in a gelling bath. , which are formed during the final winding.

Since the hollow fiber membrane produced in this way has a porous structure, a decrease in membrane strength is unavoidable.On the other hand, when this membrane is used as an ultrafiltration membrane, hollow Since a pressure of about 3 to 4 degrees is applied to the operating chamber from inside or outside the filamentous membrane as overpressure, a membrane with membrane strength that can withstand such load pressure and high water permeability is required. has been done.

There are two possible methods to increase the water permeability of hollow fiber ultrafiltration membranes, but both have their own problems.
This is not a desirable method.

(Method of reducing the concentration of hydrophobic polymer in the spinning stock solution) The hollow fiber membrane produced by this method has a coarse structure, and although the water permeability improves, the membrane strength decreases significantly, making it impossible to obtain the desired strength. I can't.

(2) How to reduce the membrane thickness (wall thickness) of hollow fiber membranes Since the knee water permeability is almost inversely proportional to the membrane thickness, it is desirable to reduce it, but in reality, the inner and outer diameters that can be spun are Since the thickness is almost fixed, the film thickness cannot be made too thin, and if it is made too thin, it will not be able to withstand oral overpressure.

The present inventor has realized that without reducing the membrane strength of the porous membrane,
Alternatively, as a result of various studies to develop an ultra-porous membrane that improves membrane strength and membrane performance, especially water permeability, we have developed a porous membrane made of hydrophobic polymer with hydrophilic silica substantially uniformly dispersed. It was discovered that an ultrafiltration membrane made of a diaphragm can sufficiently solve these problems. Accordingly, the present invention relates to such an ultraporous membrane.

Although such ultraviolet filters may be planar, they are generally manufactured and used in the form of hollow fibers. The present invention is a method for producing such a hollow fiber-like ultrafiltration membrane. The spinning stock solution prepared by the method is discharged from a hollow annular nozzle, and then introduced into a gelatinizer containing a non-solvent of the hydrophobic polymer and coagulated. More preferably, the resulting porous II membrane is It is carried out by treating at a temperature of about 50 to 110°C.

Since hydrophilic silica has hydroxyl groups on its surface, it improves the water permeability of porous membranes made of hydrophobic polymers such as polyvinylidene halide and polyvinyl halide. Hydrophilic silica is generally dispersed in the spinning dope in a proportion of about 1 to 30% by weight relative to the hydrophobic polymer. If the ratio is lower than this, the effect of adding hydrophilic silica cannot be obtained,
On the other hand, if it is used in a proportion higher than this, a defective fraction of hydrophilic silica will be caused.

Hydrophilic silica with a primary particle size of about 1 μm or less is generally used, but if it is used alone, the affinity of the hydrophobic main body is not always sufficient, so the surface of the hydrophilic silica is It is highly preferable to use it after treatment with a coupling agent that increases its affinity with hydrophobic polymers. As a coupling agent, a silane coupling agent,
Titanium-based coupling agents are used, and since these coupling agents have two or more types of mutually different reactive groups in one molecule, they act on the interface between hydrophilic silica and hydrophobic polymer, and create a bond between the two. As a bridge, C1 brings about a strong reinforcing effect.

As a silane coupling agent, the general formula R'-s is usually
:+, (On), where R' is an organic functional group such as an amino group, a mercapto group, a vinyl group, a MeeoS tacryloxy group, or a Todoroki Juxy group; group, acetoxy group, etc., and the following compounds can be enumerated, and other specific silane compounds can also be used in the same way.

r-chloropropyltrimethoxysilane vinyl I-IJ
Ethoxysilane Vinyltris(β-methoxyethoxy)silane r-methacryloxyglobiltrimethoxysilane β-(3',4-epoxychlorohexyl)ethyltrimethoxysilane l-glycidoxyglobiltrimethoxysilane vinyltriacetoxysilane l -Mercaptopropyltrimethoxysilane r-Aminopropyltrimethoxysilane N-β-(aminoethyl)
-r-Minopropyltrimethoxysilane Vinyltrichlorosilane In addition, examples of the titanium-based coupling agent include the following compounds.

Isoprobyl triisostearoyl titanate Isoprobyl tridodecyl benzene sulfonyl titanate Isopropyl tris(dioctylpyrophosphate) Titanate Tetraisopropyl bis(dimethyl phosphite) Titanelli Tetraoctyl bis(ditridecyl phosphite) Titanate Tetra(2,2- diallyloxymethyl-1-butyl)
Bis(di-tridecyl) phosphite titanate bis(dioctylpyrophos-7ate) oxyacetate titanate tris(dioctylpyrophosphate) ethylene titanate The spinning stock solution is prepared using an aprotic polar solvent, generally chosen from an economic standpoint. Hydrophilic silica particles (water-soluble in relation to aqueous gelling baths) such as dimethylformamide, dimethylformamide, dimethylacetamide, diethylacetamide, triethylphosphate, N-methylpyrrolidone, hexamethylphosporamide, tetramethylurea, etc. After dispersing, if a coupling agent is used, add one coupling agent in an amount of about 0.05 to 5% to the hydrophilic silica, stir and disperse. Add water to the hydrophobic polymer and dissolve it to remove the bamboo. During this preparation, aprotic polar
When a solvent other than 1 is used for pouring, water, which is generally used as a gelling bath, is immiscible with the aqueous medium and may cause gelation.

Dry-wet spinning using the hydrophilic silica spinning dope prepared in this way is carried out in the same manner as in the method described in ``Tsu''. However, the presence of F51 aqueous silica dispersed in the spinning dope increases the viscosity of the spinning dope.
It has the effect of making notes better.

The resulting hollow fiber-like porous membrane is coated on the inner and outer sides of the hollow membrane when a gelling liquid is used as the core liquid, and on the inner and outer sides of the hollow membrane when a non-gelling liquid is used as the core liquid. A skin layer is formed only on the outer surface side, and these skin layers are permeable layers having a porous structure with an average pore size of about 20 to 200 pores,
The portion of the membrane other than the skin layer forms a porous layer with an average pore diameter of about 1 to 10 μm.

Such a hollow fiber porous membrane is left at room temperature for about half a day,
The dried one! It can be used as an ultrafiltration membrane, but it is further dried in a drying oven at a temperature of about 50 to 110°C for about 2 to 3 hours or at a pH of 2.0 to 5.5 and a temperature of about 50 to 110°C. for about 1 to 2 hours in an acidic aqueous solution of
By heat treating it, the bond between the hydrophobic polymer and the hydrophilic silica can be made stronger. Note that the reason why the heat treatment in the aqueous solution is performed on the acidic side is to prevent hydrolysis of the bond between the coupling agent and the hydrophilic silica. But, these heat treatment J' is about 110
The reason why the temperature is below 0.degree. C. is close to the thermal deformation temperature of the hydrophobic material, which is the porous membrane material, to prevent changes in the pore distribution on the surface of the membrane.

The ultrafiltration membrane produced in this way, which consists of a porous membrane of a hydrophobic polymer in which hydrophilic silica is substantially uniformly dispersed, improves membrane performance, especially water permeability, without reducing membrane strength. In particular, those using heat-treated hollow fiber porous membranes can significantly improve not only membrane performance but also membrane strength as shown by pressure resistance data.

Next, the present invention will be explained with reference to examples.

Practical Example 1 While stirring 780 g of dimethylacetamide, add hydrophilic silica (H1-511233, a product of PPG, Inc., USA).
After stirring at room temperature for 10 minutes, adding a specified amount of silane coupling agent (UOO product A-1120) and further stirring at room temperature for 10 minutes, and adding polyvinylidene fluoride (UOO product A-1120) to it. Kiner 460) 200
g was added. After stirring for 5 hours at a temperature of about 20 to 40°C to dissolve polyvinylidene fluoride, about 4 to 5 T
The mixture was degassed under vacuum for about 20 minutes using ORR, and then allowed to stand for 10 minutes to prepare a spinning dope.

Using the spinning dope thus prepared, wet-dry spinning was performed according to the following spinning conditions to produce a hollow fiber porous membrane with an outer diameter of 1.51 m and an inner diameter of 1.1 mm.

Spinning stock solution discharge rate: 30-7 min Core liquid (water) discharge rate: 28 m/min Gelation bath: water at a temperature of 15°C Winding speed: 26 m/min Regarding the obtained hollow fiber porous membrane, water permeability, polyethylene glycol (Gyudon Kagaku) Wlooo~20000)
Mak is polyvinylpyrrolidone (Kanto Chemical Products pvpK-
The rejection rate of each substance in each 0.05 J1 mfl:% aqueous solution of 90) and the pressure resistance by bursting test were measured.

The results obtained are shown in Table 1 below, where A1 is a comparative example in which no hydrophilic silica was used, and A2 to A7 are examples in which hydrophilic silica was not treated with a coupling agent.
A8-12 are examples using hydrophilic silica surface-treated with a silane coupling agent, and &13-14 are examples using All hollow fiber porous membranes at 80°C and 10°C, respectively.
This is an example in which a sample was heat-treated for 2 hours in a drying oven at 0°C.

Example 2 In blacks 8-14 of Example 1, a titanium thread coupling agent was used in place of the silane thread coupling. That is, A1 to A5 are examples using hydrophilic silica surface-treated with a silane coupling agent (Ei no Moto Products Plenaku T, TS), and A6 to A7 are examples using the hollow fiber porous membrane of A4. In this example, samples were heat-treated in a drying oven at 80°C and 100°C for 2 hours, respectively. Furthermore,
A8 was boiled for 2 hours (10
This is an example using a sample heated to 0°C. The results obtained are shown in Table 2 below.

1-------1

Claims (1)

[Claims] 1. An ultrafiltration membrane comprising a porous membrane of a hydrophobic main body in which hydrophilic silica is substantially uniformly dispersed. 2. The ultra-diaphragm membrane according to claim 1, wherein about 1 to 30 weight percent of hydrophilic silica is dispersed in the hydrophobic main body. 3. The ultrafiltration membrane according to claim 1, wherein the porous membrane is in the form of hollow fibers. 44 A spinning dope prepared by dissolving and dispersing hydrophilic silica and a hydrophobic polymer in an aprotic polar solvent is discharged from a hollow annular nozzle, and then poured into a gelatinizing solution made of a non-solvent for the hydrophobic polymer. A method for producing a moderately strained thread-like ultrafiltration membrane, which is characterized by guiding and coagulating it. 5. A method for producing an ultrafiltration membrane according to claim 4, in which a hydrophilic silane whose surface is treated with a coupling agent that increases its affinity with the hydrophobic main body is used. A spinning stock solution prepared by dissolving and dispersing a hydrophobic polymer in an aprotic polar solvent is discharged from a hollow annular nozzle, and then introduced into a gelling bath made of a non-solvent for the hydrophobic polymer and coagulated. A method for producing a hollow fiber ultrafiltration membrane, characterized in that the obtained porous membrane is heat-treated at a temperature of about 50 to 110°C. 7. The method for producing an ultrafiltration membrane according to claim 6, wherein a hydrophilic silane whose surface is treated with a coupling agent that increases its affinity with a hydrophobic polymer is used. 8. The method for producing an ultrafiltration membrane according to claim 6, wherein the heat treatment is performed in a drying oven. 9. The method for producing an ultrafiltration membrane according to claim 6, wherein the heat treatment is performed in an acidic aqueous solution having a pH of 2.0 to 5.5.