JPS6161840A - Manufacture of composite film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a novel method for producing a composite membrane having excellent performance as a separation membrane for pervaporation.

[Technology background]

A pervaporation method is known as an effective separation method for separating liquid components from an organic liquid mixture or an organic compound solution (hereinafter collectively referred to as a liquid mixture). The pervaporation method consists of minutes 1) i1
) [The liquid mixture is supplied to one chamber (processing liquid base) divided by KK, and the other chamber (permeation vapor chamber) is evacuated or under reduced pressure. This is a method of extracting it in a vaporized state.

Separation membranes used in the above pervaporation method include cell p-based polymer membranes, polyethylene, polypropylene,
Polyac 1) A film of lunitrile, polyvinyl alcohol, polyvinyl 7-7 tar, polystyrene, polyester, polyamide, polytetrafluoroethylene, or a copolymer thereof, or a film whose surface has been treated with ultraviolet rays, etc. Membranes with ion exchange groups such as sulfonic acid groups and carboxylic acid groups introduced into the molecular chains are known. These components FQIICI are calculated by the permeability coefficient (Q
) shows a certain value, but it is insufficient for practical use, and there has been a desire to improve the transmission performance.

[Conventional technology]

BACKGROUND ART Conventionally, as a method for improving the permeation performance of a separation membrane used in a pervaporation method, a method has been proposed in which a thin membrane having separation performance is supported on a porous support and used as a separation membrane. That is, a method of fusing a thin film having 0 separation performance to a support, (2) a method of adhering the thin film to a support, (2) a method of adhering a liquid monomer forming the thin film to a support in a layered manner, and then There are methods such as polymerization.

[Problems that Mitsukiri tries to solve]

However, in the method (2) above, at m7J, the pores tend to be clogged due to the dissolution of the support by heat, and the separation performance of the resulting composite membrane tends to deteriorate. Furthermore, in the method (2), the separation performance of the resulting composite membrane tends to decrease due to the presence of an adhesive layer. Compared to these methods, method (2) is effective as a method for improving separation performance, but sufficient research has not been conducted on its manufacturing method, and composite membranes obtained by conventional methods are There is a problem in that the adhesion is insufficient and the thin film may crack or wrinkle due to temperature changes during use or handling.

[Means for solving problems]

The present inventors have conducted repeated research in order to improve the adhesion between the thin film and the support in the method (2) above without reducing the separation performance of the resulting composite membrane. As a result, a porous sheet with a specific pore size is used as a support, and a liquid monomer adjusted to a specific viscosity is supported on it. The present invention was completed based on the discovery that it is possible to obtain a composite membrane that exhibits excellent separation performance in the pervaporation method without causing any wrinkles or cracks during use or handling.

The present invention uses a liquid monomer having a viscosity of 100 to 900 centipoise (hereinafter abbreviated as CP) at 20°C, and has pores with a pore diameter of 0.1 to 10 μ at a ratio of 70% or more of the total pores. and a method for producing a composite membrane, characterized in that the monomer is polymerized after being supported in a layered manner on the surface of a porous sheet that does not expand with a liquid substance of the monomer.

In the present invention, viscosity refers to a value measured using a single cylinder rotational viscometer, and pore diameter and percentage of pores having a specific pore diameter refer to values measured using a mercury porosimeter.

In the present invention, the porous sheet used as a support is
70% or more of all pores have a pore diameter of 0.1 to 10μ,
Preferably, it is necessary to have 80% or more. In other words, when the pores smaller than the pore diameter range mentioned above are supported on the sheet surface by means of coating, casting, etc., with a liquid monomer described later, even if the viscosity of the liquid is lowered, it will not penetrate into the pores. This is difficult, and the effect of improving the adhesion of the thin film due to the anchor effect produced by the infiltration of the liquid monomer into the pores is not exhibited. In addition, if the pores are larger than the above range of pore diameters, even if the viscosity of the monomer liquid is increased, the liquid will pour into the pores, substantially increasing the thickness of the formed thin film. This results in a decrease in permeation rate. Therefore, in the present invention, by controlling the proportion of pores having a pore diameter within the above range in the porous sheet used as a support to within the above range, the U The membrane can be supported on the surface of the porous sheet with excellent adhesion without a substantial increase in membrane thickness.

Note that in the present invention, the term "sheet" does not have a particularly strict meaning regarding thickness, and also includes "film."

The porous sheet may be any material as long as it has pores with the above-mentioned pore diameter and is not swollen by the liquid monomer, and any known porous sheet that satisfies the above conditions may be used without particular limitation. For example, porous sheets made of synthetic resins, ceramics, metals, etc. that satisfy the above conditions are used regardless of the organic material or OA material. Among these, porous sheets made of synthetic resins are preferred. are polyolefin resins, polysulfone resins,
Examples include fluororesins, polystyrene resins, vinyl resins, and cellulose. Further, as for the method of manufacturing the porous sheet, known general manufacturing methods such as a stretching method, a sintering method, a phase separation method, a mixed extraction method, etc. can be applied. A particularly desirable synthetic resin porous sheet is produced by mixing and melting pellets or powder of olefinic resin such as polyethylene or polypropylene with inorganic powder such as calcium charcoal or silica, or different polymer powder, and then extruding or calendering. After processing it into a sheet shape using the single-roll method, it is stretched in the -axial direction or biaxial direction. l! #
Examples include porous sheets that meet the above conditions by creating voids between seed solids. The above-mentioned porous sheet also includes a porous sheet obtained by stretching the porous sheet and then extracting an inorganic powder or a different type of polymer using rIl, an organic solvent, or the like.

The ceramic porous sheet may be made by mixing inorganic powders such as silicon oxide, aluminum oxide, titanium oxide, calcium oxide, wl, magnesium oxide, etc. alone or in combination with a binder, etc., and then forming the sheet by sintering. It is generally used in sheet form, such as by press molding.

Furthermore, as the metal porous sheet, nickel, Wll
Powders of pig iron and stainless steel or powders of these metal salts obtained by pressure sintering or thermal decomposition are generally used.

The porous sheet preferably has a surface wettability index of 40 dynes/cm or more, preferably 45 to 55 dynes/an, in order to further improve the adhesion with the monomer liquid described later. For example, in the case of the porous sheet made of polyolefin resin, the surface may be treated by means such as a coating discharge treatment to adjust the surface wettability index to the above range. Further, in order to form a homogeneous thin film, it is preferable that the surface of the porous sheet be smooth. Furthermore, the porous sheet preferably has a porosity that does not impede the permeation of liquid components through the thin film supported on its surface. Generally 50% or more, preferably 70-90%
A porous sheet having a porosity of .

The monomer liquid used in the present invention is generally one in which a membrane formed by polymerizing the monomer can separate liquid components by a pervaporation method.

In particular, it is preferable to use a liquid monomer having an ion exchange group or a functional group into which an ion exchange group can be introduced, since the effect of improving the permeability coefficient by forming a thin film is remarkable. For example, styrene, styrene-divinylbenzene, styrene-divinylbenzene to which polyethylene, polypropylene, polyJM vinyl, polybutadiene, polytetrafluoroethylene, etc. are added as a binder, styrene-divinylbenzene-vinylpyridine, styrene-divinylbenzene. - vinylpyridine with polyethylene, polypropylene, polyvinyl chloride, polybutadiene, polytetrafluoroethylene, etc. added as a binder, styrene-fluoromethylstyrene-divinylbenzene, styrene-chloromethylstyrene-divinylbenzene with polyethylene as a binder, A monomer liquid containing polypropylene, polyvinyl chloride, polybutadiene, polytetrafluoroethylene, etc. can be used. Appropriate plasticizers and polymerization catalysts are added to these monomer liquids as the case may be, and these liquid monomers are applied onto a porous sheet to a predetermined thickness so as to form a separation membrane, and then a known method such as heating polymerization is carried out. Polymerize to form a separation membrane. Moreover, if an exchange group such as a cation exchange group or an anion exchange group is added to the separation membrane through post-treatment, further improvement in separation properties can be expected. For example, a liquid monomer consisting of styrene-divinylbenzene, polyvinyl chloride powder, a plasticizer, and a polymerization catalyst is applied onto a porous polybupylene sheet, polymerized, and then sulfonated with concentrated sulfuric acid to form a cation exchange group. A 7-mer liquid consisting of styrene-divinylbenzene, polyvinyl chloride powder, a plasticizer, 2-methyl-5-vinyl pyridine, and a polymerization catalyst was applied onto a porous polypropylene sheet and polymerized, followed by dilution with a methyl iodide solution. There are methods such as grading and adding an anion exchange group.

Among the liquid monomers mentioned above, those containing a crosslinking agent as one component are extremely suitable for use because the thin film formed on the porous sheet has excellent heat resistance, one-dimensional stability, long-term strength, etc. It is. The proportion of such a crosslinking agent used is 2 to 40%, preferably 5 to 30% based on the total monomer.
Weight percentages are common.

In the present invention, the monomer liquid supported on the surface of the porous sheet described above has a viscosity of 10 at 20°C.
The range of 0 to 900CP, preferably 200 to 8000P is used. When the viscosity of the monomer liquid is lower than the above range, the monomer liquid supported on the surface of the porous sheet penetrates deeply into the pores, and the monomer liquid is combined to form a monomer liquid. Since this results in a substantial increase in the thickness of the thin film, the effect of improving the permeation rate of liquid components by thinning the film is hardly exhibited. Furthermore, if the viscosity of the seven-mer liquid is higher than the above range, it will not only be difficult to uniformly support the monomer liquid on the surface of the porous sheet, but also when using a porous sheet with a distribution of pore sizes. , it becomes difficult for the liquid monomer to penetrate into the pores having a pore diameter of 0.1 μm or less, and the anchor effect due to the polymerization of the monomer is not sufficiently exerted.

The method for controlling the viscosity of the monomer liquid within the above range is not particularly limited. For example, if the liquid monomer is a paste-like mixture of liquid monomer and thermoplastic resin, by increasing or decreasing the amount of the thermoplastic resin added,
Alternatively, the viscosity can be adjusted by adjusting the amount of plasticizer added. In addition, when using the liquid monomer alone, since the liquid monomer may be partially polymerized,
Its viscosity can be adjusted.

In the present invention, there are no particular limitations on the method of supporting the liquid monomer in a layered manner on the surface of the porous sheet. Generally, a method of applying a liquid monomer using a roller, spatula, etc.

A method is adopted in which a porous sheet is placed on a horizontal surface, a frame is provided around it as necessary, and a liquid monomer is cast. The thickness of the layer of the liquid monomer is 5 μ or more, preferably 1
It is desirable to set it to 0μ or more. On the other hand, if the thickness is increased, the effect of improving the permeation rate due to thinning is reduced, so the upper limit of the thickness is preferably 100μ, preferably 80μ.

The monomer liquid can be polymerized using a known polymerization method to form a thin film on a porous sheet, thereby obtaining the composite membrane of the present invention. The composite membrane obtained by the method of the invention has excellent adhesion between the porous sheet and the thin film, and can effectively prevent the occurrence of wrinkles, cracks, etc. in the thin film. Since the depth at which the membrane is filled with the polymer constituting the thin film is shallow, the effect of improving the separation characteristics of the membrane by thinning the membrane is extremely high. For example, when the composite membrane of the present invention is used as a separation membrane in a pervaporation method, it exhibits excellent permeation characteristics. In this case, the composite membrane is generally provided with a thin membrane facing toward the processing liquid chamber. Although the operating conditions in this case are not particularly limited, the pressure on the mixed liquid chamber side that supplies the liquid mixture is preferably in the range of 1 to 10 atm, preferably at or near atmospheric pressure. On the other hand, the pressure on the permeate gas chamber side is preferably below atmospheric pressure, preferably 100ml/g
A sub-column vacuum is preferred. In other words, in the pervaporation method, it is necessary to evaporate the liquid component that has passed through the membrane at the membrane surface on the permeate gas chamber side and take it out in a vapor state, so the pressure on the permeate gas chamber side is It is preferred to maintain the pressure as low as possible below the vapor pressure of the substance being permeated.

The temperature of the liquid mixture in the processing liquid chamber is not particularly limited, but a high temperature is preferable in terms of the permeability coefficient. However, if the temperature is too high, the film may crack or its durability will deteriorate, so the temperature is generally 10-100℃, preferably 30-100℃.
A temperature range of 80°C is preferable.

The pervaporation method using the composite membrane of the present invention is preferably applied to a liquid mixture in which at least one component is a polar solvent and does not have an adverse effect on the membrane. Examples of liquid mixtures consisting of two plates include methanol/water, ethanol/water, or n-propertool/
Water, methyl ethyl ketone/water.

Dioxane/water, methanol/7setone, benzene/n
-Liquid mixtures such as azeotropes such as hexane and near-boiling mixtures.

〔Example〕

An embodiment of the present invention will be described in more detail below using Example C, but the present invention is not limited to these Examples.

In addition, in the Tora Examples and Comparative Examples, the peel test was conducted by the following method.

Peeling test: 2 pieces of silica located on the surface of the test piece within 1d angle
Cut it into a base pattern at intervals, apply Nichiban Co., Ltd. cellophane adhesive tape to the surface, and when you peel it off,
The remaining percentage of the thin film was expressed as an area ratio x/100.

Example 1 Fine polyvinyl chloride powder was added to 70 parts of 4-vinylpyridine, 20 parts of styrene, and 10 parts of divinylbenzene (purity 50%) in the proportions shown in Table 1, and 2 parts of benzoyl peroxide was further added. A pasty liquid having a viscosity shown in Table 1 was prepared. A porous sheet was prepared in which a polypropylene sheet highly filled with calcium carbonate was made porous by biaxial stretching and the surface was subjected to corona discharge treatment. This sheet has a thickness of 120μ and a porosity of 70%.
, courtesy distribution 0.3-3μ, average pore 60.8 B + surface wetting index 47 dyns/m. Next, the above paste-like liquid material is uniformly applied onto the porous sheet using a roll, and wrapped in a Tetron film to prevent the monomer from volatilizing.
It was tightened between two iron plates and polymerized for 4 hours in an autoclave at 80°C. After the polymerization was completed, the obtained polymer sheet was immersed for 20 hours at room temperature in a quaternization solution consisting of methyl dihydride and methanol in a ratio of 1:1 to impart anion exchange groups. Subsequently, the composite membrane was obtained by immersion treatment in a mixed solution of water/acetone=1/2 (vot%) for 20 hours, followed by washing with water. When the composite membrane was observed under an electron microscope, a polymer separation membrane was formed on the polypropylene porous sheet with the thickness shown in Table 1.

The 7-ion exchange capacity of the thin film part of this composite membrane is 1.7 to 2
．． The dry weight was 2 meq/lΦ.

Next, using the Pi composite film, a mixture of water and i-propanol (water/1-propanol=10
/9oji amount ratio). On the mixed liquid side, the liquid temperature is 5.
The separation performance obtained was as shown in Table 1 at a temperature of 5°C and an atmospheric pressure of 52 mH9 on the vapor permeation side.

The results of the peel test are also shown in Table @1.

Example 2 A polyethylene sheet with a thickness of 70μ, a porosity of 85%, a pore size distribution of 0.2 to 8μ, and an average pore diameter of 2μ, made porous by a stretching method, was used as the porous sheet. Using the same material as /I62 in Example 1, a composite membrane with a polymer separation membrane portion thickness of 50 μm was produced in the same manner as in Example 1.

Using this composite membrane, water and a 1-propertool mixture were separated in the same manner as in Example 1.

Separation performance is permeated liquid amount sao, 9/m・hour.

The separation factor was 94. In addition, the results of the peel test are Zo
It was o/100.

Example 3 A porous sheet made by mixing diatomaceous earth and a binder, compression molding and sintering, thickness 3 mm, porosity 65%, pore size distribution 0
．． A composite membrane having a polymer separation membrane portion of 35 .mu.m was fabricated using a ceramic sheet having a diameter of 4 to 10 .mu.m and an average pore diameter of 1.5 .mu.m by the same paste-like liquid membrane forming method as in Example 101-2. Using the composite membrane, water and the 1-propertool mixture were separated in the same manner as in Example 1.

Separation performance is 7401 permeate volume! /7FLl・hours.

The separation factor was 80. Also, the result of the ifJ test is 9
It was 2/100.

Example 4 100 parts of 2-methyl-5-vinylpyridine, 40 parts of styrene,
10 parts of divinylbenzene, 20 parts of dioctyl phthalate 1. A paste-like liquid material having a viscosity of 600 centipoise was prepared from 90 parts of polyvinyl chloride fine powder and 4 parts of benzoyl peroxide. A porous sheet made of polypropylene used in Example 1 was used as the porous sheet, and a membrane was formed in the same manner as in Example 1 to produce a composite membrane with a polymer separation abdomen having a thickness of 70 μm. The exchange capacity of the composite membrane is 1.02meq/j'・
It was dry weight. Using this membrane, a mixture of water and methanol (water/methanol = 20/80.weight ratio) was prepared by pervaporation at a temperature of 50°C and under atmospheric pressure.
Separation was carried out at a vapor permeation side pressure of 5 m53H9. The separation performance was 1320 permeate volume, 9/i/time, 9 separation coefficient, 35. Moreover, the result of the peel test was 100/100.

Comparative Example As a porous sheet, a polypropylene sheet highly filled with calcium carbonate was biaxially stretched at a high magnification and then treated with an acid to extract calcium carbonate. This porous sheet has a thickness of 120μ and a porosity of 79%.

The pore size distribution was 3 to 17μ (45% of pores larger than 10μ), the average pore diameter was 12μ2, and the surface wettability index was 36dyne/α. A composite membrane was obtained using the above porous sheet in the same manner as /162 of Example 1. Using the obtained composite membrane, water and i-purpanol mixed liquid were separated in the same manner as in Example 1. The separation performance was as follows: permeate volume: 297II/7FLI, time: 1, separation coefficient: 1). Moreover, the result of the peel test was 80/100.

Claims (6)

[Claims] (1) A monomer liquid having a viscosity of 100 to 900 centipoise at 20°C, which has pores with a pore diameter of 0.1 to 10 μ at a ratio of 70% or more of the total pores, and 1. A method for producing a composite membrane, which comprises supporting the monomer in a layered manner on the surface of a porous sheet that does not swell when exposed to heat, and then polymerizing the monomer. (2) The method according to claim 1, wherein the porous sheet has a porosity of 50% or more. (3) The method according to claim 1, wherein the porous sheet has a surface wettability index of 40 dynes/cm or more. (4) The method according to claim 1, wherein the layer formed by the liquid monomer has a thickness of 5 to 100 microns. (5) The method according to claim 1, wherein the liquid monomer is a paste mixture of a liquid monomer and a thermoplastic resin. (6) Whether the monomer liquid has an ion exchange group,
Alternatively, the method according to claim 1, which is a liquid monomer capable of introducing an ion exchange group.