JPH10296062A - Manufacture of polymer porous tubular film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for industrially manufacturing a porous tubular film formed of polyolefin while easily controlling a pore diameter. SOLUTION: In the method for manufacturing the polymer porous tubular film, 10-55 pts.wt. water-soluble polymer compound, 50-210 pts.wt. water-soluble fine powder having 3-50 μm average particle diameter and 1-15 pts.wt. dispersant are blended with 100 pts.wt. polyolefin. After the obtained mixture is melted and kneaded, it is formed into a tubular film and then the obtained tubular film is immersed into an aqueous solvent. Higher fatty acid, higher aliphatic alcohol, parafin and higher aliphatic amid are favorable as the dispersant. Polyethylene oxide of >=400,000 molecular weight is favorable as the water-soluble polymer compound. Pentaerythritol is favorable as the water-soluble fine powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a polymer porous tubular membrane useful as a separation membrane or the like. More specifically, the present invention uses a polyolefin as a membrane material, and melts and kneads a predetermined water-soluble substance into the membrane material. The present invention relates to a method for industrially and easily producing a high-quality polymer porous tubular membrane by blending and forming a film, and then eluting the water-soluble substance in the membrane with an aqueous solvent. According to the method of the present invention, the pore size of the porous tubular membrane can be easily controlled, and the obtained porous tubular membrane has excellent separation efficiency. Useful for separating substances.

[0002]

2. Description of the Related Art In recent years, separation membrane technology has been used in various fields such as food, pharmaceutical, biotechnology, chemical and electronics industries for energy saving, simplification of processes and improvement of quality. Among them, the porous separation membrane made of polyolefin has a wide range of applications because of its excellent chemical resistance.
The demand is great.

A method for producing a porous material from a polyolefin includes an extraction method in which an additive is added to a polymer compound to form a film, and then the additive is extracted by an appropriate method, or a polymer compound is dissolved in an organic solvent. After casting the film forming solution on a substrate such as a glass plate, immersing it in an appropriate gelling solution, casting it to obtain micropores by phase separation, forming the polymer into an arbitrary shape, stretching it, And the like.

However, currently used polyolefin porous membranes are almost flat membranes or tubular or hollow fiber-shaped ones having an inner diameter of 1 mm or less, so that their use is inevitably limited. For example, in some cases, the treatment cannot be performed depending on the composition and physical properties of the liquid to be separated. On the other hand, 1 mm
The above-mentioned tubular membrane is complicated and extremely expensive to manufacture, or has a limitation in terms of chemical resistance because it is a composite membrane. When the polymer porous tubular membrane is used as a separation membrane for separating suspended substances contained in factory wastewater such as metal hydroxide, the particle size of the metal hydroxide in such wastewater is usually 10%. Since the pore size of the separation membrane is about 5 μm or less, sufficient separation performance can be obtained by filtration and separation, but when the pore size is 1 μm or less,
In order to improve the efficiency of filtration and separation, the operation cost is too high because the separation energy is too high, and the operation cost is too high, and the porosity of the one with a pore diameter of more than 1 μm decreases as the porosity increases. In order to increase the filtration speed, it is necessary to make the filtration pressure such as pressure filtration or vacuum filtration severe, but it is inevitable that the membrane performance decreases, such as not being able to adequately meet such required characteristics .

[0005] As a method for producing a porous substance using a polyolefin, an extraction method is considered to be relatively simple and suitable for industrialization. However, in a film forming method using this method, a porous body having a uniform pore diameter is produced. It is difficult, and the control of the pore size largely depends on the physical shape of the particles to be extracted, and there are many technical restrictions.

[0006]

DISCLOSURE OF THE INVENTION The present invention overcomes the drawbacks of the conventional polymer porous tubular membrane and the method for producing the same, and enables the porous tubular membrane made of polyolefin to be produced easily while controlling the pore size. The purpose of the present invention is to provide a method for manufacturing a semiconductor device.

[0007]

Means for Solving the Problems The present inventors have conducted various studies in order to develop a method for producing the above-mentioned preferable polymer porous tubular membrane. It was found that the purpose could be achieved by using a compound comprising a finely divided powder and a dispersant as a film-forming material, and employing a method of eluting a water-soluble material in the film with an aqueous solvent as an extraction method. The present invention has been completed based on the findings.

That is, the present invention relates to a polyolefin 10
Water-soluble fine powder having an average particle diameter of 3 to 50 μm and a water-soluble fine powder of 50 to 210 parts by weight, based on 0 part by weight.
Parts by weight, and a mixture formed by mixing 1 to 15 parts by weight of a dispersant is melt-kneaded, then formed into a tubular film, and then the obtained tubular film is immersed in an aqueous solvent. A method for producing a tubular membrane is provided.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the method of the present invention, a polyolefin is used as a material for a porous tubular membrane because it is excellent in chemical resistance, heat stability, moldability, and inexpensive. The polyolefin is not particularly limited, but preferably has a melt index (MI) of 0.5 to 4.
5, polypropylene and propylene-based random copolymer,
Examples thereof include polyethylene having a melt index (MI) of 3 to 7, and among them, the above-mentioned polypropylene, particularly atactic polypropylene, and a propylene-based random copolymer, particularly, a propylene-ethylene random copolymer are preferable.

As the eluting substance, a substance capable of forming a desired porous structure with respect to the polyolefin selected as the membrane material is used. As such an eluting substance, a water-soluble polymer compound and a water-soluble fine powder are used. The water-soluble polymer compound is a polymer compound that is soluble in an aqueous solvent, especially water, and has a melting temperature lower than the melting temperature of the polyolefin. For example, polyethylene oxide, polyethylene glycol, paogen (Daiichi Kogyo) Pharmaceutical company) and the like, among which polyethylene oxide,
In particular, those having a high molecular weight of 400,000 or more are preferable, and among such high molecular weight polyethylene oxides, the molecular weight is 1,000,000 to 5,000,000, particularly 2,000,000 to 40,000.
One having a molecular weight of 100,000 is preferred because it has excellent moldability of a required tubular membrane.

The water-soluble fine powder is a fine powder having an average particle size of 3 to 50 μm which is soluble in an aqueous solvent, especially water, and is stable at the melting temperature of the polyolefin, and preferably inert. Examples of such substances include inorganic salts such as ammonium chloride, potassium sulfate, calcium chloride, and potassium bromide, thiourea, and pentaerythritol. It is preferable that the water-soluble fine powder is stable even in a temperature range from the melting temperature of the polyolefin to the processing temperature. Particularly preferred as the water-soluble fine powder is pentaerythritol, and when it is used, a polymer porous tubular membrane having a pore structure in which countless fibers are intimately entangled is obtained. This is presumed to be due to the fact that pentaerythritol is a substance having good thermal stability and being inert to polyolefins and having high self-dispersibility. The water-soluble fine powder can change the internal structure of the polymer porous tubular membrane by changing its particle shape and particle size, its physical properties, such as thermal stability, and various kinds of materials. Can be.

In the method of the present invention, first, these polyolefin, water-soluble polymer compound, water-soluble fine powder and dispersant are melt-kneaded. At this time, it is preferable to use polyethylene oxide having a molecular weight of 1,000,000 to 5,000,000, particularly 2,000,000 to 4,000,000 as the water-soluble polymer compound and pentaerythritol as the water-soluble fine powder. The melt-kneading process is performed by heating and mixing a water-soluble polymer compound, a water-soluble fine powder, and a dispersing agent until the melting point of the water-soluble polymer compound, and then adding the mixture to a sufficient molten polyolefin and kneading the mixture. Is preferred. When the water-soluble polymer compound is compounded, the water-soluble fine powder alone is not sufficiently continuous in the particle pores after the water-soluble fine powder is eluted from the tubular membrane.
This is for preventing the function as the separation membrane from being deteriorated, and the water-soluble polymer compound can cause sufficient continuation of the particle pores.

In the melt-kneading treatment, it is important to uniformly disperse the water-soluble polymer compound and the water-soluble fine powder in the polyolefin, and a dispersant is used for this purpose. Examples of the dispersant include higher fatty acids such as stearic acid, higher fatty alcohols such as stearyl alcohol, higher fatty acid amides such as paraffin, stearoamide, palmitylamide, methylenebisstearamide, and ethylenebisstearamide. And preferably at least one selected from higher fatty acids, higher fatty alcohols, paraffins and higher fatty acid amides.
Species are mentioned, and higher fatty acid amides are particularly preferred. One type of dispersant may be used, or two or more types may be used in combination. Also, the dispersant generally has a tendency that the smaller the particle size, the larger the cohesive force tends to be, but by dispersing this,
This is effective in reducing the open cell structure of the porous tubular membrane and making the pore diameter more uniform.

In the melt-kneading treatment, an additive for imparting stability to the resin such as an antioxidant and a metal deactivator such as a metal deterioration inhibitor may be used as long as the object of the present invention is not impaired. Can be added.

The mixing ratio of each material used in the melt-kneading process is 100 parts by weight of polyolefin based on weight.
The water-soluble polymer compound is 10 to 55 parts, preferably 25 to
45 parts, water-soluble fine powder 50 to 210 parts, preferably 1
10 to 160 parts, dispersant 1 to 15 parts, preferably 6 to
Selected in the range of 9 parts. If the proportion of the water-soluble polymer compound is too small, the continuity of the pores becomes difficult. If the proportion is too large, the viscosity of the compound is reduced, so that it is difficult to form the compound into a tube. If the proportion of the water-soluble fine powder is less than this range, the porosity will decrease, and the membrane performance will decrease. If the proportion is too large, the strength of the tubular membrane will decrease. If the proportion of the dispersing agent is too small, the effect of the addition becomes insufficient, and the uniformity of the pores is reduced. No longer.

In the method of the present invention, the film-forming material, that is, the compound thus melt-kneaded is formed into a tubular film. This film is preferably formed by extrusion. Examples of the tubular membrane thus obtained include a tube and a pipe. The size of the tubular membrane is
It is appropriately selected depending on the purpose of use and the type and particle size of the suspended substance to be separated by filtration. For example, a separation membrane used for filtration and separation of suspended solids in factory wastewater has an inner diameter of 2 to 8 mm, preferably 3 to 6 mm, and a wall thickness of 0.5 to 3 mm, preferably 1 to 3.
Those having a size of ２2 mm, especially an inner diameter of 3-6 mm and a thickness of 1-2 mm, are advantageous. In film formation, especially in film formation by extrusion molding, generally the form of the film is a flat film,
Alternatively, the physical properties of the compound are related to the moldability depending on whether it is a tubular membrane. In flat membrane molding, a method in which a predetermined compound is melt-kneaded and then solidified in a mold can be used.On the other hand, in tubular membrane molding, a predetermined shape is formed by using an extruder such as a tube molding. Since the melt molding is performed, the influence of the melting characteristics of the compound on the molding is increased. About the water-soluble polymer compound in this compound, the viscosity at the time of melting differs depending on the kind, and in the case of typical examples, such as paogen, polyethylene glycol, and polyethylene oxide, the viscosity at the time of melting becomes higher in this order. The difference in viscosity of the water-soluble polymer compound affects the moldability. Some water-soluble polymer compounds become too soft under the molding processing conditions of the base resin, causing layer separation depending on the molding temperature, making the water-soluble polymer compound more likely to flow out, and reducing the viscosity of the compound too much. Although there are some which make the forming of the tubular membrane itself difficult, polyethylene oxide having the highest viscosity among the above representative examples is preferable because of its excellent molding stability. In the extrusion molding, it is preferable that the extruded high-temperature soft tubular membrane is hardened by dry cooling so as to lower the temperature to 50 ° C. or higher within a short period of time, preferably within 15 seconds, to form a tubular membrane. The tubular membrane having a size of 8 mm and a wall thickness of 0.5 to 3 mm is advantageously obtained by dry cooling and hardening the high-temperature soft tubular membrane so as to lower the temperature to 50 to 100 ° C. within 3 to 7 seconds. By doing so, it is possible to achieve both the formation of the tubular membrane and the homogeneous distribution state of the eluted components effective for the expected pore formation described later.
It is desirable to use dehumidified nitrogen gas for dry cooling, but dehumidified air may be used.

In the method of the present invention, the tubular membrane thus formed is then immersed in an aqueous solvent as an eluent to immerse the water-soluble polymer compound or water-soluble fine powder in the membrane. The volatile substances are removed by elution with an aqueous solvent to form a porous tubular membrane. As the aqueous solvent used at this time, an aqueous solvent capable of dissolving a water-soluble polymer compound or a water-soluble fine powder, preferably water is used.

As the aqueous solvent, in addition to water, a mixed solvent of water and a water-soluble organic solvent is used. As the water-soluble organic solvent, for example, methanol, ethanol, 1-
Propanol, 2-propanol, 1-butanol, 2
Alcohols such as -butanol, isobutyl alcohol and tert-butyl alcohol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; and ethers such as diisopropyl ether, dibutyl ether, tetrahydrofuran and dioxane. It is preferable that the content of the water-soluble organic solvent in the mixed solvent does not exceed 30% by weight.

The elution treatment is advantageously carried out by placing the formed tubular membrane in an outflow water tank at a liquid temperature of 40 to 60 ° C. and immersing it. The elution time is usually 12 hours or more, and is preferably selected in the range of 18 to 54 hours.

In the method of the present invention, the pore size of the porous tubular membrane can be controlled arbitrarily, for example, in the range of 5 to 50 μm by appropriately selecting the type and physical properties of the water-soluble polymer compound and the water-soluble powder and the production conditions. And the membrane can have an open cell structure. In the method of the present invention,
To obtain a tubular membrane, especially a tube, having an inner diameter of 2 to 8 mm and a wall thickness of 0.5 to 3 mm, polyolefin 100
10 to 55 parts by weight of the water-soluble polymer compound, based on parts by weight,
A mixture obtained by mixing 50 to 210 parts by weight of a water-soluble fine powder having an average particle size of 3 to 50 μm and 1 to 15 parts by weight of a dispersant is melt-kneaded, then subjected to extrusion molding and extruded, and extruded high-temperature soft tubular membrane. Is dried and cooled to lower the temperature within 50 to 100 ° C. within 3 to 7 seconds to form a tubular film, and then the resulting tubular film is immersed in an aqueous solvent. Higher fatty alcohols,
It is preferable to use at least one selected from paraffins and higher fatty acid amides. Further, the molecular weight of the water-soluble polymer compound is 400,000 or more, preferably 1
It is preferable to use 0,000 to 5,000,000, especially 2,000,000 to 4,000,000 polyethylene oxide, and pentaerythritol as a water-soluble fine powder.

[0021]

Next, the present invention will be described in more detail by way of examples, which should not be construed as limiting the present invention.

Example 1 100 parts by weight of polypropylene (RV421, manufactured by Tokuyama Corporation) and polyethylene oxide (PEO-, manufactured by Sumitomo Seika Co., Ltd.)
15) 25 parts by weight, 125 parts by weight of pentaerythritol having an average particle diameter of 30 μm and 7.5 parts by weight of stearic acid
After granulating the compound obtained by melt-kneading at 75 to 200 ° C., the obtained pellets are extruded with a tube die (UEV type manufactured by Union Plastics).
Under the molding conditions shown in Table 1, the outer diameter was 8 mm and the inner diameter was 5
at a rate of 4 m / min into a cooling device having an inner diameter of 12 mm, and a dehumidifying air flow of 7 ° C. is jetted radially into the ring of the cooling device at a flow rate of 9 L / sec to perform dry cooling. Reduce to 110 ° C in seconds and cure, outer diameter 8mm
And a tubular membrane having an inner diameter of 5 mm. Then, the tubular membrane was submerged in a 40 ° C.
After immersion for 8 hours, the water-soluble substance in the membrane was almost eluted to produce a porous tubular membrane sample. Table 2 shows the dissolution rate and various properties of the sample thus obtained. The elution rate is the amount of the eluting substance eluted by the immersion treatment with respect to the total amount of the eluting substance in the tubular membrane before the immersion treatment (the amount obtained by subtracting the remaining amount of the eluting substance in the sample from the total amount). ) Means the weight percentage.

Examples 2 to 5 A porous tubular membrane sample was obtained in the same manner as in Example 1 except that the compounds having the composition shown in Table 1 were used. Table 2 shows the dissolution rate and various characteristics of this sample. FIG. 1 shows an electron micrograph of the cross-sectional structure of the sample of Example 2.
From FIG. 1, it can be seen that this sample has fine pores of uniform pore diameter. Further, the pore size distributions of the samples of Examples 1 and 2 are shown in graphs in FIGS. 2 and 3, respectively. This indicates that the pore size distribution of the sample of the example is within a relatively narrow range.

Example 6 The amount of the dispersant was changed as shown in Table 1 and the immersion time was set to 24.
A porous tubular membrane sample was obtained in the same manner as in Example 2 except that the time was changed. Table 2 shows the dissolution rate and various characteristics of this sample.

Example 7 A porous tubular membrane sample was obtained in the same manner as in Example 6, except that the water-soluble polymer compound and the molding conditions were changed as shown in Table 1.
Table 2 shows the dissolution rate and various characteristics of this sample.

Comparative Examples 1 to 3 Compounds having no dispersant having the composition shown in Table 1 were directly subjected to extrusion molding without granulation, and the molding conditions were changed as shown in Table 1. Except for the above, a porous tubular membrane sample was obtained in the same manner as in Example 1. Table 2 shows the dissolution rate and various characteristics of this sample. Comparative Example 1
FIG. 4 is a graph showing the pore size distribution of the sample.
This indicates that the pore size distribution of the sample of the comparative example covers a relatively wide range.

[0027]

[Table 1]

Various symbols in Table 1 have the following meanings. RV421: manufactured by Tokuyama Corporation, polypropylene PN110K: manufactured by Tokuyama Corporation, polypropylene PN410G: manufactured by Tokuyama Corporation, polypropylene PEO-3: manufactured by Sumitomo Seika Chemical Co., Ltd., polyethylene oxide (average molecular weight 600,000 to 1.1 million) PEO-15: Sumitomo Seika Chemical Co., Ltd. PEO-18: manufactured by Sumitomo Seika Co., Ltd., polyethylene oxide (average molecular weight: 4.3 million to 4.8 million) PEO-1105: manufactured by Union Carbide Co., Ltd., polyethylene oxide (average molecular weight: 90) 10,000) PET * 5: pentaerythritol with an average particle size of 5μ PET * 30: pentaerythritol with an average particle size of 30μ STM: stearamide MBSTM: methylenebisstearic amide

[0029]

[Table 2]

The amount of permeated water was determined by injecting water into the sample at a filtration pressure of 0.2 MPa by a cross flow filtration method.

From the above, it can be seen that the sample of the comparative example has an excessively large average pore size, has a low tensile strength, and requires a long time for immersion in the preparation thereof, whereas the sample of the example has a fine average pore size. It can be seen that the sample has excellent tensile strength and has an advantage that the immersion treatment in the preparation of a sample having a practical dissolution rate comparable to that of the sample of the comparative example can be performed in a short time.

[0032]

According to the method of the present invention, a porous tubular membrane made of polyolefin can be industrially produced by a short-time immersion treatment with a practical elution rate while easily controlling the pore size. Has a remarkable effect. The polymer porous tubular membrane obtained by the method of the present invention has a fine average pore size and excellent separation efficiency, and is particularly useful for separating suspended substances contained in industrial wastewater such as metal hydroxides. The present invention is also useful in that a polymer porous tubular membrane exhibiting excellent properties such as excellent strength and relatively narrow pore size distribution can be provided at any time.

[Brief description of the drawings]

FIG. 1 is an electron micrograph of a cross-sectional structure of a porous tubular membrane sample in Example 2.

FIG. 2 is a graph showing the pore size distribution of the sample of Example 1.

FIG. 3 is a graph showing the pore size distribution of the sample of Example 2.

FIG. 4 is a graph showing the pore size distribution of the sample of Comparative Example 1.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Ryusaburo Ohno 2107-3, Kamiyabe-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside of Nippon Filter Corporation (72) Inventor Naoki Oba 2107-3, Kamiyabe-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Nippon Filter Corporation

Claims (12)

[Claims] 1 to 100 parts by weight of a polyolefin, 10 to 55 parts by weight of a water-soluble polymer compound, average particle size of 3 to 50 parts.
50 to 210 parts by weight of a water-soluble fine powder of μm, and dispersant 1
A method for producing a polymer porous tubular membrane, comprising melt-kneading a mixture comprising up to 15 parts by weight, forming a tubular film, and then immersing the obtained tubular film in an aqueous solvent. 2. The method according to claim 1, wherein the dispersant is at least one selected from higher fatty acids, higher fatty alcohols, paraffins and higher fatty acid amides. 3. The method according to claim 1, wherein the water-soluble polymer compound is polyethylene oxide having a molecular weight of 400,000 or more. 4. A water-soluble polymer compound having a molecular weight of 1,000,000 or more.
4. The method according to claim 3, which is 5 million polyethylene oxide. 5. The method according to claim 1, wherein the water-soluble fine powder is pentaerythritol. 6. The method according to claim 1, wherein the aqueous solvent is water. 7. The method according to claim 1, wherein the polymer porous tubular membrane has an inner diameter of 2 to 8 mm and a wall thickness of 0.5 to 3 mm. 8. The method according to claim 1, wherein the film is formed by extrusion. 9. A water-soluble polymer compound is used in an amount of 10 to 55 parts by weight based on 100 parts by weight of polyolefin, and has an average particle diameter of 3 to 50.
50 to 210 parts by weight of a water-soluble fine powder of μm, and dispersant 1
After melt-kneading a mixture comprising up to 15 parts by weight, the mixture is subjected to extrusion molding, and the extruded high-temperature soft tubular membrane is mixed with 3 parts by weight.
Dry cooling and curing to lower the temperature within 50 to 100 ° C. within 7 seconds to form a tubular film, and then immersing the obtained tubular film in an aqueous solvent;
and a method for producing a polymer porous tubular membrane having a thickness of 0.5 to 3 mm. 10. The method according to claim 9, wherein the dispersant is at least one selected from higher fatty acids, higher fatty alcohols, paraffins and higher fatty acid amides. 11. The method according to claim 9, wherein the water-soluble polymer compound is polyethylene oxide having a molecular weight of 400,000 or more, and the water-soluble fine powder is pentaerythritol. 12. The method according to claim 11, wherein the water-soluble polymer compound is polyethylene oxide having a molecular weight of 1,000,000 to 5,000,000.