JPS58205503A - Oil-water separating film and its production - Google Patents

Abstract

PURPOSE:To form a porous film suited for separating oil and water selectively from a liquid mixture of oil and water by filming a hydrophobic polymer and a hydrophilic polymer so as to have the specific phase sepn. structure. CONSTITUTION:A hydrophobic polymer A such as fluorinated vinyl polymer, polyolefins, synthetic rubber or the like and a hydrophilic polymer B such as celluloses, PVA deriv., PVC deriv. or the like are mixed at a specific ratio and a film wherein one of the polymers is dispersed in a granular state is formed. The film is stretched at least uniaxially to form holes between the separated two phases of the polymer A and the polymer B. The film wherein the polymer B is dispersed in a granular state in the polymer A is used to separate water selectively from a mixture of oil and water and the film wherein the polymer A is dispersed in the polymer B is used to separate oils selectively. The film has the surface less vulnerable to contamination by oil and water and has a small decrease in the rate of treatment.

Description

[Detailed description of the invention] The present invention relates to an oil-water separation membrane and a method for manufacturing the same.

Conventional methods for separating water and oil from oil-water mixtures include specific gravity methods that utilize the difference in specific gravity - centrifugal separation methods that apply gravity greater than natural gravity, pressure flotation methods, adsorption separation methods, electrostatic methods,
There are methods that utilize magnetic properties, methods that use chemical flocculants, and membrane separation using porous membranes and selective separation membranes.

However, in the specific gravity method, centrifugation method, and pressure flotation method, the size of the suspended particles is important, and only oil-water mixtures with a large difference in specific gravity can be separated well. Processing time or a large gravity generator is required〇E, adsorption amount and air are a! L, j, male...

The separation effect is poor because other substances are also adsorbed, and there are problems such as the difficulty of reusing the adsorbent and the treatment method of the adsorbent.

Methods that use chemical agents have problems such as the generation of secondary substances and the infiltration of foreign substances into the separated liquid.

Membrane separation methods using porous membranes and selective permeability are described, for example, in JP-A-55-1291.14 and JP-A-56-1999.
There is a method using reverse osmosis as shown in Japanese Patent Application Laid-open No. 51206 and Japanese Patent Application Laid-Open No. 57-48305, but this method is permeable only to water, and water-in-oil type cannot be separated. In addition, the processing speed for oil-in-water type oil-water mixtures is very low, and the processing pressure is very high. Also, Japanese Patent Publication No. 55-45242, Japanese Unexamined Patent Publication No. 55'-15
Publication No. 4610 has the effect of so-called emulsion braking, which enlarges oil particles by passing an oil-water mixture through a non-woven Ti.After the treatment, an oil-water separation operation such as a gravity method or a specific gravity method is performed. It is necessary to carry out
Complete oil/water separation is difficult o'51. #Kaisho 54-9
No. 4167, JP 54-95072, JP 54-164061, JP 55-79011
The publication proposes an oil-water separation method using a microporous membrane made of a polymer with a certain critical surface tension.
There are limits to the degree of oil-water separation, as the processing speed is slow and separation becomes difficult when the oil-water composition exceeds a certain level.

The present inventors thoroughly studied the principles of oil-water separation and the shortcomings of conventional methods, and developed a porous chamber cA having a completely new structure and physical properties suitable for oil-water separation, and developed the present invention. An object of the present invention is to provide a novel porous 6-layer membrane with excellent oil/water separation performance, and a further object of the present invention is to provide a method for producing a novel porous membrane with excellent oil/water separation performance. Smell. , 1 The present invention is characterized in that each of the mutually incompatible water-flowing polymer and the hydrophilic/living polymer has a phase-separated structure, and there are two pores between the interfaces of each one of the polymers for phase separation. It is a porous membrane with excellent oil-water separation properties, and the method of the present invention is to form a thin film using a mixture of a hydrophobic polymer and a hydrophilic polymer that is miscible with the hydrophobic polymer and is incompatible with the hydrophobic polymer. The porous membrane of the present invention is characterized in that the porous membrane of the present invention is characterized in that it is formed into a shape and then stretched in at least one axis to generate pores due to phase separation between the interfaces of a hydrophobic polymer and a hydrophilic polymer. It consists of an incompatible hydrophobic polymer (hereinafter referred to as polymer A) and a hydrophilic polymer (hereinafter referred to as polymer B). Incompatibility means that when a mixture of Polymer A and Polymer B is melt-mixed, or when their respective solutions are mixed, they do not dissolve each other and form a single melt or solution, or when these melts or This means that each polymer component precipitates when the solution is cooled and solidified or the solvent is removed.

The polymer is hydrophobic, and the degree of hydrophobicity is, for example, a contact angle with water of 850° or more, preferably 90° or more. Polymer B is hydrophilic and has a contact angle with water of 85° or less, preferably 800° or less.

Polymer A includes the synthesis of y y fg vinyl polymers such as polytetrafluoroethylene, polytrifluoroethylene, and polytrifluorochloroethylene, polyolefins such as polypropylene, polyethylene, and polyethylene-globylene, polybutadiene, neoprene, etc. Rubbers, polyethylene, and polyalkyl rubbers include silicone rubbers such as xane, and blends and copolymers thereof.

Polymer B includes cellulose, acetylcellulose,
Celluloses such as cellulose sulfate, methyl cellulose, and carboxymethyl cellulose, polyvinyl alcohol,
Polyvinyl alcohol derivatives such as polyvinyl butyral, polyvinyl cyanethyl ether, polyvinyl methyl ether, polyvinyl chloride derivatives such as polyvinyl acetate, polyvinyl chloride, polyvinyl chloride-vinyl acetate,
6 nylon, 6 row nylon, etc. are preferred.

Of course, hydrophobicity and hydrophilicity are largely determined by the surface of the polymer, and can be achieved by surface coating, addition of hydrophilic substances or lipophilic substances, graft polymerization, oil treatment, Goodsma treatment, electronic or radiation treatment, etc. It may also be surface-modified tun.

These treatments can be performed either before or after deafening.O The mixing ratio of polymer A and polymer B is determined depending on the intended oil-water separation liquid and method. For example, when selectively separating a water component from an oil-water mixture, a membrane in which polymer B is dispersed in granular form in polymer A is used.

In this case, it is preferable that the amount of polymer A be larger than the amount of polymer B so that the above structure can be easily formed. The amount of polymer A is 50~
It is preferably 98%, more preferably 60-95%, and most preferably 70-90%. Polymerization/XA is 5
If it is less than 0%, the structure of granular dispersion of 1 cli coalescence B in polymer A will be particularly small, and if it exceeds 98% km, the amount of phase separation will be small and the processing speed will be low.

On the contrary, when selectively separating only the oil component from the mixture into the oil 7, a membrane in which the polymer A is dispersed in granular form in the monomer B is used. Here, if l of polymer B is larger than the amount of polymer A, it is easier to form a film having the above-mentioned structure. i of polymer B is preferably 50 to 98%, more preferably 70 to 95%
Polymer B, particularly preferably 70 to 9 oz.
If it is less than 5Q%, it is difficult to form a structure in which polymer B is dispersed in granular form. Moreover, if it exceeds 98'X, phase separation will be less likely and the processing speed will be lower.

Furthermore, when the purpose is to destroy the emulsion of water-in-oil or oil-in-water oil gamma mixtures by passing through the porous membrane of the present invention instead of selectively permeating oil or water, polymer A may be used. and Polymer B can also be used as the sea component.

In this case, the polymer Ac">i is preferably 30 to 7a, and the island component polymer Bi in the V'-o polymer or the island component polymer A in polymer B is dispersed in granular form. Teh
There must be.

Particulate dispersion can be easily generated by a continuous mixing operation when the polymer and polymer B have monocompatibility and have little compatibility. The dispersion form of the island component is preferably spherical, particularly spherical with a uniform diameter.

This can be achieved to some extent by changing the combination of polymer BA and polymer B, mixing ratio, mixing method, dispersant, etc.

In addition, if polymer A and polymer B are difficult to mix, for example, if polymer A has a high melting point such as polytetrafluoroethylene or is difficult to dissolve in a solvent, it can be made into a fine powder and then polymer B can be mixed.
It is also possible to mix and mold the mixture.

By stretching the film in at least one axis, pores can be generated at the interface between the polymer A and the polymer B due to phase separation of the polymer A and the polymer B. This is thought to occur because the cohesive force between the 12 phase-separated phases is smaller than the force required for each component to form a hairstyle. The pores are generated in the same way in the polymer and at all the interfaces of the polymer B, and the amount and size of the pores can be changed as appropriate depending on the size of the polymer 3, the stretching ratio, etc. The size of the pores obtained here is within the range expressed by equation (11).

2ku(λ-1)D ・・・・・・・・・(1) Here °
2: Maximum length of the pores in the stretching direction O: Length of the island component in the stretching direction In: Stretching ratio Normally 7 or less The size of the pores in the porous membrane according to the present invention, the key feature is the shape of the pores This is because the holes are very different from conventional holes, and the shape of the holes will be explained in detail using figures.

FIG. 1 is an enlarged explanatory view of the stretched film after molding. 1
indicates the sea component polymer, 2 indicates the island component polymer, and S indicates the pores generated at the interface, indicating that the island component polymer is dispersed in the sea component polymer in a spherical state◇ Figure 2 And FIG. 5 shows the pores of the porous film according to the present invention! Figure A shows the unstretched 71 lums in Figure 2, which has been stretched 141B in the right direction in the figure, and Figure 3, V, has undergone biaxial stretching in the horizontal and vertical directions in the figure. As mentioned above, the characteristics of the pores of the present invention are that the area and periphery of the pores are larger than the volume of the pores, and this makes it difficult for the pores to become clogged. Leads to improved performance. In addition, a granular dispersion of polymer A (9 or B) remains in the pores, and even when a large differential pressure is applied to both sides of the membrane, this provides support and makes it difficult for the membrane to become compacted. have Although the pores due to phase separation of polymer A and polymer B vary depending on the combination of polymer A and polymer B, mixing ratio, mixing conditions, and stretching conditions, the maximum flame of the pores is required for convenient use in oil-water separation. is preferably 0.05 μm to 50 μm. (10
If it is less than 5μ, the processing speed will be slow and the life will be significantly reduced, and if it is more than 50μ, the selective separation performance will be degraded.

As mentioned above, the uninvented microporous membrane with excellent oil/water separation performance has a phase-separated structure of hydrophobic and hydrophilic parts on the surface, and pores due to phase separation at the interface. Having it is a necessary condition.

Due to the phase separation structure of the hydrophobic part and hydrophilic part on the surface, the oil-water mixture is condensed and separated into each component on the membrane surface. In other words, the surface emits a kind of Emma Regicompoker effect. In addition, although the degree of hydrophobicity or hydrophilicity of the polymer or monopolymer in the porous pouring was similar, the blend membrane had no difference in the hydrophilic and hydrophobic parts of the surface, and the membrane surface is easily contaminated with oil or water, and as a result, the processing speed decreases (p≦large).

However, in the case of a membrane having a phase-separated structure of a hydrophobic part and a hydrophilic part as in the present invention, the membrane surface was less likely to be contaminated by oil or water, and the reduction in processing speed was very small. The reason for this is not known in detail, but it is speculated that the hydrophobic part and the hydrophilic part have a four-structure phase separation on the surface of the membrane in a mosaic pattern. It is thought that the adhesion of the oil component or water component to the sexual part will be limited to that area, and if more than a certain amount adheres, it will drop into the liquid.

These points are very important features of the present invention, and are new i-performances that are not available in conventional models. The form of the membrane can be either a flat membrane or a hollow system, and the manufacturing method can be conventional.

However, in the present invention, after forming into a flat membrane or hollow system, one united A
In order to promote the generation of pores due to the phase separation of the field 1 of the polymer B, stretching in the uniaxial direction is necessary at least.

The uninvented porous membrane is miscible with the hydrophobic polymer (Polymer A) and the hydrophobic polymer, but with the incompatible hydrophilic polymer (Polymer A).
It is manufactured by mixing the polymer B), forming the mixture into a thin film, and then stretching the film in at least one axis.

The method of mixing Polymer A and Polymer B is to heat and melt each polymer and mix them, or to mix them under heat under a pressure of Ω using an extruder, or to simply melt the mixture. Depending on the combination and purpose of the polymers, such as melting and mixing methods, or solid-liquid mixing methods in which one polymer is kneaded or the other polymer is made into fine powder and mixed together. Various mixing methods can be adopted depending on the situation.

Mixing operation is also done using Henschel mixer and Banbury mixer 1.
-A variety of equipment can be used depending on the purpose, such as a shaft or two-wheeled two-nostruder, homo mixer, lab body spar, ball mill, colloid mill, sand grinder, etc.◎ Polymer A and polymer B phase separate in the mixture, whether it is a melt or a solution. ing. In the state of phase separation, one or both of the polymers is dispersed in the form of particles in the other polymer. When making a thin film in which polymer B is dispersed in polymer A, the amount of polymer B is 50 to 98% by weight, and the amount of polymer B is 2 to 50% by weight, and more preferably 60 to 95% by weight of polymer B. The amount of polymer B is preferably 5 to 40 y, and preferably the polymer itself is 70 to 90 y and the polymer B is 10 to 30 y.

In addition, in the case of a thin film in which Polymer A is dispersed in Polymer B, Polymer B is 50 to ν8% and the polymer is 2 to 5%.
5L]J[i% is preferred, and more preferably polymer B is 60 to 95zt% and polymer A is 5 to 401zt%,
Particularly preferably, polymer B is 70 to 90% by weight and polymer A is 1% by weight.
is 10 to 30%.

Although the fractional state varies depending on the combination of bundles, mixing ratio, and mixing method, it is preferable that the fraction be dispersed in a +d spherical shape, and more preferably in a uniform spherical shape like a dogfish. It is also possible to add a dispersant to improve the fractional state during mixing.

In order to obtain a good fractional morphology, it is preferable to carry out the polymerization while checking the mixture by visual observation, microscopic observation, light scattering method, etc.

Conventional film forming methods, hollow system manufacturing methods, etc. are used to form a thin film from the mixture.The thickness of the film and the inner and outer diameters of the hollow system vary depending on the target oil/water separation, but thinner is generally preferable. The thickness is 0.1 to 0.21 or less.

Polymer A and Polymer B formed into thin films exhibit poor phase distribution, and by stretching these thin films at least in the -S direction, they can be divided into Polymer A and Polymer B. Two holes can be formed.

In the case of 11111 stretching, the stretching ratio is preferably 1.05 times or more and 7 times or less.If it exceeds 0.7 times, a high temperature may be required during stretching, or a larger one may be required. Or! If it is less than 1.05 times, pores will be generated at the interface due to elastic deformation of the polymer.

Stretching process is preferably 1.05 to 5 times, more preferably,
It is 1.5 to 5 times. The stretching is preferably carried out in hot water or in a gas or liquid medium that is inert to the thin film.Uniaxial stretching is easy to operate, produces good pores, and produces anisotropy in strength. Therefore, for applications that require mechanical strength, biaxial stretching is performed. Stretching may be carried out, or stretching may be carried out in both directions at the same time.The pores shown in the above-mentioned figure and equation 11) are observed in the stretched thin film.

After stretching, the thin film can be subjected to IC& treatment to improve heat resistance and strength stability. Heat treatment is usually carried out in hot water, steam, or a hot medium, but it is preferable to fix the dimensions of the thin film in order to prevent bending and distortion of the shape. Furthermore, it goes without saying that the heat treatment should be carried out at a temperature that does not eliminate the pores generated by stretching. This heat treatment often improves the morphological stability and mechanical properties of porous membranes.

The porous membrane obtained by the present invention has a phase-separated structure of a hydrophobic portion and a hydrophilic portion on the membrane surface, and has pores at the interface, and the shape of the pores is unprecedented. It has a completely different structure from the book separation membranes obtained up to now.
Something that has physical properties. In addition, note 11M regarding γ-field water separation of the porous membrane according to the present invention describes the emulsion M knob breaker-like effect due to the hydrophobic and hydrophilic phase separation structure, prevention of membrane surface contamination, and reduction of pores due to phase separation. It has an unprecedented advantage of selective overpressure of oil or water.

The membrane obtained according to the present invention can be used for general filtration such as solid-liquid separation layer or solid separation layer, air release separation, etc.
A paper on oil and water all over the place. It can be used for separation of two liquids and three liquids, such as separation of liquid mixtures that do not dissolve in each other.

Hereinafter, a more detailed explanation will be given with reference to Examples. In the Examples, unless otherwise specified, parts and % indicate weight. Also, capacity % is abbreviated as VoL%.

The size of the pores was determined by observing a single light microscope or an electron microscope. (Determined using formula 23.

Porosity v (to 49) = (+ -) x +o
o L2J However, A Apparent specific gravity of the thin film f Near J Deer's true ratio Apparent ratio was determined from the volume of the thin film in N- and water It is the ratio I in the state of a single integrated vacancy having the composition.

Example 1 80% of the A component polymer (sea component) shown in Table 1 and B
A dimethylformamide solution of a mixture with 20% of the component polymer (which will become the island component) was thoroughly stirred in a homomixer, cast onto a glass plate using a doctor blade, and dried in a hot air dryer.◎Drying The film was peeled off from the glass plate and stretched 1.5 times -am in hot water.The thickness of the stretched film was approximately 15μ.0 The oil-water separation test was conducted using a mixture of 80% kerosene and 20% water.
A mercury-in-oil emulsion was obtained by vigorously stirring with a body spar and used as a treatment liquid. The test equipment is a commercially available transient tester with a stirrer attached.

The polymer used in this test is an acrylic polymer composed of the following: Acrylonitrile: Acrylic methyl: Allyl sulfone or sodium = 90.0:9. Q2 1.0 (mm) Average degree of polymerization 115O WP table Cellulose...degree of acetylation 55'X Average polymerization t
170 Vinyl chloride/vinyl acetate copolymer...Vinyl chloride: Vinyl acetate = 88:12 (%) Average degree of polymerization 00 Polyvinylidene heptanide...Used the trade name Kynar at the Pennwalt Exhibition in the U.S. Polystyrene. ...Average molecular weight 1 [)000 Table 1! Refreshing Example 2 Rattan 2 85% of the λ component polymer shown in Table 2 (mixed with the sea component) and B
A 15% solution of each component (which will become the E-portion polymer island component) was mixed to prepare a film-forming stock solution. The acrylic polymer used in Example 1 was dissolved in a 55% aqueous solution of thione anhydride at a polymer concentration of 10%, and polyvinyl alcohol (average degree of polymerization j'500) was dissolved in water at a polymer concentration of 10%. It was dissolved to 10%. Polybutadiene (average molecular weight 130,000) was added to toluene at a polymer concentration of 10%.
It was dissolved to become

The film-forming stock solution was applied onto a glass plate using a doctor prude to a thickness of 200 μm, and then dried in a hot air dryer.

After drying, ExpNo.
A 5μ film was made. EII) No. 8 was dried, and then the polyvinyl alcohol was stabilized in 7QC in an aqueous solution of polyvinyl alcohol to obtain a film with a thickness of 20 μm. The unrolled film was rolled twice as much -S in hot water to form a porous film.
Got Lum.

For the oil/water separation test, a mixture of 95% water and 5% kerosene was vigorously stirred in a LabDesper and an oil-in-water emulsion was used. The test method was the same as in Example 1.

Table 2 Example 5 Porous films were obtained from the unstretched nXp4 film of Practical Example 1 by varying the stretching ratio in hot water. The oil/water separation test was similar to Example 1.

Table 3 Tonebo Gosen Co., Ltd. Procedures Amendment Book September 1982 φ8 11! Display of 1987 Patent Head No. 87167 @ Name of Z Invention Oil/Water ml! II and its manufacturing method 6. Relationship with the person making the amendment Patent applicant address: 5-17-4 Sumida, Sumida-ku, Tokyo Address: 1-5-80 Tomobuchi-cho, Bejima-ku, Osaka 554, Japan Patent Department, Kanebo Co., Ltd. 5. The number of inventions increased by the amendment None. 6. The following F is added next to the table on page 25 of column 7 for the content of the amendment in "WAta explanation of the drawings" of the specification subject to the amendment. .

4. Brief explanation of the drawings @ Figure 1 is an enlarged explanatory view of the stretched 11II film after forming, Figure 2 is an explanation showing the state of pores in the uniaxially stretched film, and Figure 5 is the biaxially stretched film. It’s a diagram.”

Claims (1)

[Scope of Claims] (1) Consisting of a hydrophobic polymer and a hydrophilic polymer that are incompatible with each other, each polymer having a phase separation structure, and a phase separation between the interfaces of each polymer. A porous membrane with excellent oil-water separation performance having pores of 3) The porous membrane according to claim 2, wherein the hydrophobic polymer is 50 to 98% by weight. (4> The porous membrane according to claim 2, wherein the hydrophobic polymer is 60 to 95% by weight. The porous membrane according to claim i. (5) The porous membrane according to claim 1, which has a structure in which a hydrophobic polymer is dispersed in granules in a hydrophilic polymer. (6) Hydrophilicity The porous membrane according to claim 5, in which the polymer content is 50 to 98% by weight. (71! [Claim 5 or 6, in which the aqueous polymer is 60 to 95% by weight (8) The porous membrane according to claim 1, which has pores of 0.05 to 50μ due to phase separation between the hydrophobic polymer and the hydrophilic polymer interface. (9 ) The porous membrane a (Kl) according to claim 1 or 8, wherein the pores due to phase separation between the hydrophobic polymer and the hydrophilic polymer are 11 to 10μ. ] A method for producing a porous membrane with excellent oil/water separation performance, which is characterized by stretching the hydrophobic polymer to be miscible with the hydrophobic polymer and generating pores due to phase separation between the interfaces of the hydrophobic polymer and the hydrophilic polymer. ◎ (11) The method according to claim 10, wherein either the hydrophobic polymer or the hydrophilic polymer is dispersed as a particulate island component in the other polymer. (t2) Hydrophobicity The method according to claim 10, wherein the polymer comprises 50 to 98% by weight. (S) The method according to claim 10 or 12, wherein the hydrophobic polymer comprises 60 to 95% by weight. Method. (S4) The method according to claim 10, wherein the hydrophilic polymer is 50 to 98% by weight. (i5) The method according to claim 10, wherein the hydrophilic polymer is 60 to 95% by weight. Or the method according to claim 14. (Powder) The method according to claim 10, wherein the stretching ratio is 1.05 to 5 times. (13) A method according to claim 10 or 16, in which the stretching is carried out in two directions.
Method 0 described in section 0