JPS61161109A - Preparation of separating membrane - Google Patents

Abstract

PURPOSE:To obtain pervaporation membrane which does not become hard even if the proportion of org. liquid is increased by covering porous synthetic resin film with polymer contg. ion exchange group. CONSTITUTION:Porous synthetic resin film having 5-500sec/100cc air permeation velocity, 0.05-2mu mean pore size, >=30 dyne/cm surface wettability index, with 10-100mu film thickness, is impregnated uniformly with liquid monomer having ion exchange group or liquid monomer capable of introducing ion exchange group thereto, and the impregnated monomer is polymerized. Suitable viscosity of the liquid monomer is 50-500cP at 20 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a novel method for producing a separation membrane that exhibits excellent performance in pervaporation methods.

(Technical Background) A pervaporation method is known as an effective separation method for separating liquid components from an organic liquid mixture or a solution of an organic compound (hereinafter collectively referred to as a liquid mixture). In the pervaporation method, a liquid mixture is supplied to one chamber (processing liquid chamber) divided by a separation membrane, and the other chamber (permeation vapor chamber) is evacuated or under reduced pressure to permeate specific liquid components from the liquid mixture. This method takes out the gas in a vaporized state into a steam chamber.

[Conventional technology]

As separation membranes used in the above pervaporation method, polymer membranes having ion exchange groups, so-called ion exchange membranes, have been known. Although such ion exchange membranes exhibit good separation coefficients representing the selective permeation performance of liquid components, the values of the permeability coefficients representing the permeation rate of the liquid components are insufficient for practical use.

Therefore, attempts have been made to reduce the thickness of the ion exchange membrane to improve the permeation rate of the separation membrane.

For example, there is a method of using a separation membrane in which a thin ion exchange membrane is supported on a reinforcing sheet.

[Problem that the invention seeks to solve]

However, since the above-mentioned separation membrane is composed of two layers: an ion exchange membrane and a support, when separating water from a water-organic liquid mixture, for example, when the concentration of the organic liquid in the liquid mixture reaches an upper limit, There is a problem in that the ion exchange membrane becomes partially dehydrated, hardens, and becomes easily damaged. In addition, swelling of the ion exchange membrane layer due to temperature changes in the concentration of the organic liquid,
There is a problem in that the ion exchange membrane layer is peeled off from the support due to severe shrinkage.

[Steps to resolve the problem]

The present invention aims to solve the above-mentioned problems associated with thinning of ion-exchange membranes, and has an ion-exchange group in a porous synthetic resin film having a specific air permeability m, average pore diameter, and surface wettability index. Alternatively, the present invention provides a method for producing a separation membrane that achieves the above object by impregnating the membrane with a liquid monomer capable of introducing an ion exchange group and then polymerizing the membrane.

The present invention has an air permeation rate of 5 to 500 seconds/100cc,
The average pore size is 0.05-2μ, and the surface wettability index is 3.
A porous synthetic resin film of 0 dynes/arm or more is impregnated with a liquid monomer having an ion exchange group or capable of introducing an ion exchange group (hereinafter collectively referred to as liquid monomer), and then polymerized. This is a method for manufacturing a separation membrane.

In the present invention, the air permeation rate is a value measured according to JISP-8117, the pore diameter is a value measured by a mercury porosimeter, and the surface wettability index is a value measured according to JIS K6768.

The porous synthetic resin film used in the present invention has an air permeation rate of 5 to 500 seconds/100cc, preferably 10 to 500 seconds/100cc.
200 seconds/100cc, average pore size 0.05~2μ,
In order to achieve the object of the present invention, it is necessary to have a surface wettability index of preferably 0.1 to 1 μ and a surface wettability index of 30 dynes/cm or more, preferably 45 dynes/cm or more. That is, the air permeation rate is determined by the porosity, porosity, pore diameter, etc. of the porous synthetic resin film, which affects the proportion of liquid monomer impregnated into the film. That is, in a porous synthetic resin film with an air permeation rate lower than the above range, the ratio of the ion exchange resin part in the separation membrane formed by impregnating and polymerizing a liquid monomer decreases, and the ratio of the ion exchange resin part on the separation membrane surface decreases. As a result, a separation membrane having good values for both separation coefficient and permeability coefficient cannot be obtained. Also,
The higher the air permeation rate of the porous synthetic resin film, the better the separation state of the obtained separation membrane can be. However, if the air permeation rate is increased too much, the strength of the film will decrease and it will be more likely to tear during handling. Therefore, it is desirable that the air permeation rate be within the above range.

In addition, even if the air permeation rate of a porous synthetic resin film satisfies the above range, if the average pore diameter is larger than the above range, the ion exchange resin portion formed in the film will become coarse and the permeability coefficient will decrease. As mentioned above, when the separation membrane is dehydrated, it may harden and lose its flexibility. Furthermore, if the average pore diameter is smaller than the above range, it becomes difficult to impregnate the liquid monomer and it is not possible to uniformly make the ion exchange resin portion exist.

The value of the wetting index of the porous synthetic resin film is necessary to provide affinity between the porous synthetic film and the ion exchange resin part formed by liquid polymerization, and if the leakage index is smaller than the above range, When using a separation membrane, cracks occur between the film and the ion exchange resin portion due to changes in the concentration of the treatment liquid, and the separation coefficient decreases over time. In addition, if the retardation index is too high, the porous synthetic resin film will swell violently due to the liquid monomer used, and the strength of the resulting separation membrane will tend to decrease. Therefore, the wettability index of the porous synthetic resin film is 60 dynes/
It is desirable to keep it below cni, preferably below 55 dynes/cm. The wettability index of a porous synthetic resin film is mainly determined by the type of synthetic resin constituting the film. Examples of suitable synthetic resins include polyethylene,
Examples include polyvinyl chloride, polypropylene, polysulfone, and the like.

Among them, polyethylene is most suitable.

In the present invention, the porous synthetic resin film is not particularly limited in other properties as long as it satisfies the above-mentioned properties. Generally, the thickness is preferably 10 to 100μ, preferably 20 to 70μ in order to further improve the separation coefficient of the separation membrane obtained.

The manufacturing method of the porous synthetic resin film is not particularly limited, and generally known general manufacturing methods such as a stretching method, a sintering method, a phase separation method, and a mixed extraction method are applicable.

In the present invention, the liquid monomer can be used without particular limitation as long as it has an ion exchange group or a functional group into which an ion exchange group can be introduced.

For example, styrene, styrene-divinylbenzene, styrene-divinylbenzene with polyethylene, polypropylene, polyvinyl chloride, polybutadiene as a binder, etc.
Products with polytetrafluoroethylene added, styrene-divinylbenzene-vinylpyridine, styrene-divinylbenzene-vinylpyridine with polyethylene, polypropylene, poly(vinyl chloride), polybutadiene, polytetrafluoroethylene, etc. added as a binder. , styrene-
Chloromethylstyrene - divinylbenzene, styrene -
A liquid product prepared by adding polyethylene, polypropylene, polyvinyl chloride, polybutadiene, polytetrafluoroethylene, etc. as a binder to chloromethylstyrene-divinylbenzene can be suitably used. These liquid monomers are further added with appropriate plasticizers and polymerization catalysts as the case may be, impregnated into a porous synthetic resin film, and then polymerized by a known method such as heat polymerization to form a separation membrane.

Furthermore, if an exchange group such as a cation exchange group or an anion exchange group is provided to the separation membrane by post-treatment as necessary, further improvement in separation properties can be expected. For example, a method in which a porous polyethylene film is impregnated with a liquid monomer consisting of styrene-divinylbenzene, polyvinyl chloride powder, a plasticizer, and a polymerization catalyst, polymerized, and then sulfonated with concentrated sulfuric acid to impart a cation exchange group; - A porous polyethylene film is impregnated with a liquid monomer consisting of divinylbenzene, polyvinyl chloride powder, a plasticizer, 2-methyl-5-vinyl pyridine, and a polymerization catalyst, polymerized, and quaternized with a methyl iodide solution to form an anion exchange group. There are ways to give it.

Among the above-mentioned liquid monomers, those having a crosslinking agent as one component have excellent heat resistance, dimensional stability, long-term use strength, etc. in combination with a porous synthetic resin film, and are extremely suitable for use. The proportion of such a crosslinking agent used is 2 to 40% by weight, preferably 5 to 3% by weight based on the total monomer.
0% by weight is common.

In the present invention, the liquid monomer supported on the surface of the porous synthetic resin film has a viscosity of 50 to 500 CP at 20°C, preferably 100 to 300 CP. This is preferable in order to uniformly impregnate the liquid monomer into the liquid monomer.

(Functions and Effects) The method of the present invention maintains the skeleton of the film by impregnating and polymerizing a liquid monomer into a matrix made of a porous synthetic resin film having an appropriate pore size and high porosity. However, it can contain a high proportion of ion exchange resin.

Therefore, it is possible to obtain a separation membrane with a high separation coefficient and sufficient strength even when the membrane is thinned to about 10 to 20 μm and has a high permeability coefficient.

Further, the separation membrane obtained by the method of the fourth invention does not harden even if the proportion of the organic liquid in the liquid mixture treated in pervaporation becomes high.

The separation membrane of the present invention exhibits excellent separation characteristics when used as a #I membrane in a pervaporation method. Although the operating conditions in this case are not particularly limited, the pressure on the mixed liquid chamber side for supplying the liquid mixture is preferably 1 to 10 atmospheric pressure or less, preferably a vacuum of 100 mm H9 or less. In other words, in the pervaporation method, it is necessary to evaporate the liquid component that has passed through the membrane on the membrane surface on the side of the permeated gas chamber and take it out in the form of vapor, so the pressure on the side of the permeated gas chamber is It is preferred to maintain the pressure as low as possible below the vapor pressure of the substance.

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 to 100 degrees Celsius, preferably 30 to 80 degrees Celsius.
A range of ℃ is preferable.

The pervaporation method using the separation 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 components include methanol/water, ethanol/water, 1- or n-propertool/
Examples include liquid mixtures such as azeotropic mixtures and near boiling point mixtures such as water, methyl ethyl ketone/water, dioxane/water, methanol/acetone, and benzene/n-hexane.

(Examples) Hereinafter, embodiments of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 10 parts of polyvinyl chloride fine powder was added to 70 parts of 4-vinylpyridine, 20 parts of styrene, and 10 parts of divinylbenzene (purity 50%), and further 2 parts of benzoyl peroxide were added to make a paste with a viscosity of 200CP. A liquid substance was prepared. Next, polyethylene porous sheets shown in Table 1 manufactured by the mixed extraction method were prepared.

The properties of this sheet are shown in Table 1. Next, the porous sheet was impregnated with the above paste-like liquid material by immersion, wrapped in Tetron film to prevent the monomer from volatilizing, tightened between two iron plates, and polymerized in an autoclave at 80°C for 4 hours. I did it. After the polymerization was completed, the obtained polymer sheet was immersed in a quaternization solution consisting of methyl iodide and methanol (1=1) at room temperature for 20 hours to impart anion exchange groups. Next, the membrane was immersed for 20 hours in a mixed solution of water/acetic acid to 1/2 (vo 6%), and then washed with water to obtain a separation membrane.

The anion exchange capacity of this separation membrane was as shown in Table 1.

Next, using the composite membrane, water and i
- Proper tool mixture (water/i-beopanol = 10/
90 weight ratio). On the mixed liquid side, the liquid temperature is 55℃
The process was carried out under atmospheric pressure, at a vapor permeation side pressure of 5 mmHa, and at a water/improper tool amount ratio of 1/99. The membrane performance at this time was as shown in Table 1.

The flexibility of the resulting separation membrane in a dry state was also observed. The results are also shown in Table 1.

Margin below Table 1 1・ 1・ No, 6.7. H is comparative.

Claims (3)

[Claims] (1) A porous synthetic resin film with an air permeation rate of 5 to 500 seconds/100cc, an average pore diameter of 0.05 to 2μ, and a surface wettability index of 30 turns/cm or more, which has ion exchange groups or ion exchange groups. 1. A method for producing a separation membrane, which comprises impregnating a liquid monomer into which an exchange group can be introduced and then polymerizing it. (2) The method according to claim 1, wherein the porous synthetic resin film is made of polyethylene. (3) The method according to claim 1, wherein the porous synthetic resin film has a thickness of 10 to 100 microns.