JPS60209207A - Treatment of separating film to acquire capacity for fractionating lower molecular weight fraction - Google Patents

Abstract

PURPOSE:To obtain a separating film capable of fractionating an object to fractions having smaller mol.wt. than the separating film before the treatment without impairing the high rate of permeation of the untreated film by immersing the separating film in an aq. soln. of sugar and drying thereafter. CONSTITUTION:The treatment can be applied to separating films consisting of wide variety of kind without being restricted by the structure and shape of the film. A separating film is immersed in an aq. soln. contg. monosaccharide or polysaccharide in water, or the aq. soln. of sugar is sprayed on the separating film. The aq. soln. of the sugar may contain inorg. or org. compds. which does not react with the sugar. Preferred concn. of the sugar is 1-5wt%, and preferred temp. of the aq. soln. is 10-50 deg.C, and preferred treating time is 10-24hr. After the treatment, the film is dried until the weight of the film attains a constant value by an appropriate method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for low fractionation of separation membranes, and its purpose is to provide membranes with controlled molecular weight cut-off and high permeability ii't-. This is to provide an easy way to obtain.

[Prior art]

In recent years, material separation using membranes has come to be widely applied due to remarkable advances in technology. Examples include the water production field, such as seawater and brine desalination, and wastewater treatment; the food and gas production industry; and the medical field, such as artificial kidneys.

The functions required of membranes are considered to be both unique to each field and common, but they are expected to be more sophisticated depending on the conditions of use.

The required performance specific to each field is its own physical and chemical stability. For example, in seawater desalination, chlorine resistance, #I resistance, heat resistance, hydrolysis resistance, and chemical resistance are required. , microbial resistant and neutral. In addition, in the food-related field, hygiene is
In the medical field, non-toxicity to living organisms is particularly required.

In addition to the unique demands of each field, more precise fractionation and a larger permeation amount are desired in each field, but in general, fractionation and permeation amount have contradictory properties. However, it is not easy to obtain a membrane with high permeability while maintaining fractionation.

Although many attempts have been made in the past, there still remain problems such as insufficiency and the need for advanced technology. That is, conventional methods for increasing the permeation amount include methods using hydrophilic polymers, methods for introducing functional groups, and methods for compounding.

Hydrophilic polymers include cellulose and cellulose, -
Although there are membranes based on gas derivatives, these membranes are most widely used for the purpose of filtration of water and bath liquids.

However, chemically stable hydrophilic functional groups such as chemical resistance and heat resistance are generally compatible with hydrophobic and hydrophilic polymers such as polysulfone, polytetrafluoroethylene, polypropylene, and polyethylene, which have excellent physical and chemical stability. The main thing is introduction. Functional groups include acidic groups such as sulfonic acid groups and carphonic groups, and salts of clouds, which are introduced in 69 different ways. However, the reaction conditions and performance must be tightly controlled, which often impairs the stability of the membrane.

- Various types of composite membranes have been developed, particularly as reverse osmosis membranes, and their feature is that the separation membrane material part and the support part are functionally separated.

However, special techniques are required for selection of separation membrane materials and membrane manufacturing methods. Therefore, at present, it has only been put to practical use in areas where mass production advantages can be achieved, such as desalination of seawater and brine water.

Among the above-mentioned problems, especially the highly transparent TL! Focus on low and medium molecule filtration in the field you are looking for. for example,
Between inorganic salts such as table salt and high molecular weight substances such as paint particles and proteins, there are a wide variety of useful and undesirable compounds such as amino acids, sugars, and pigments, and it is necessary to recover and remove them. These fields include refining, wastewater treatment, and recovery of valuables within processes in the food, gas, and pharmaceutical industries. Application of membrane separation in these fields is also being intensively researched, but it is fraught with various inherent problems.

Attempts have been made to adapt membrane materials for RO or UF, but a membrane with sufficiently satisfactory performance, that is, a membrane that maintains physical and chemical stability and fractionability and has a high permeation rate, has not been obtained. is the current situation.

For example, regarding fractionation, current RO membranes, that is, membranes with very small fractions, require high pressure to operate, and the amount of permeation, which is a problem, is too small.

On the other hand, a membrane for UP' having a molecular weight cut-off on the order of 10,000 can obtain a sufficient amount of permeation, but its fractionation performance is poor.

[Purpose of the invention]

In view of the above, the present inventors conducted extensive research and found that
It was discovered that by drying the separation membrane after immersing it in a sugar water bath, it was possible to maintain a high permeation rate and have a smaller φ cut-off molecular weight than the separation membrane before treatment, and further studies led to the invention of the present invention. This is what led to this.

Therefore, an object of the present invention is to provide a simple method for obtaining a membrane having a controlled molecular weight cutoff and a high permeation amount by using a separation membrane with a low fractionation method.

[Battle bottom of invention]

The present invention is a seventh method for low fractionation characterized by immersing a separation membrane in an aqueous sugar solution and then drying it.

The separation membrane referred to in the present invention includes a gas-gas thermothermal membrane, a gas-liquid separation membrane,
The membrane is not particularly limited as long as it can be used for the purpose of substance separation, such as a liquid-liquid separation membrane or a liquid-liquid separation membrane. It can be used in separation membranes used in the field of water production, food products, the gas production industry, the medical field, etc., and there are no restrictions on the fractionability of the separation membrane. Preferably a reverse osmosis membrane? Applied to ultrafiltration membranes.

Membrane materials can also be applied to a wide variety of materials, such as polyamide acetate, polycarbonate, polyacrylonitrile, polymethyl methacrylate, polyimide, polyetherimide, polysulfone polyethersulfone and their blends, block copolymers, and graft copolymers. etc.

The membrane structure may be an asymmetric membrane, a symmetric membrane, or a composite membrane, and the membrane shape may be flat, hollow, or tubular.

The term saccharides used in the present invention refers to monosaccharides and sub-long saccharides in which a plurality of monosaccharides are glycosidic bonded to each other. Synthetic sugars such as those with a straight carbon skeleton, those with branched carbon skeletons, and those with some of the alcoholic hydroxyl groups substituted with hydrogen atoms or other groups may also be used.

The aqueous solution of sugar referred to in the present invention is a solution in which sugar is dissolved in water.
A mixed solution system containing organic substances such as acetone and alcohol, or polymers can also be used.

There is also no restriction on the concentration of sugar in the aqueous solution.

However, if the aqueous solution concentration is less than 0.5 wt%, there will be no effect and the amount of permeation will be extremely low, which is not practical, so it is preferably 1 to 5. A concentration of wt.

As a method for treating the separation membrane with an aqueous solution, any of the following methods may be used: immersing the separation membrane in a standing or stirring aqueous solution, circulating and supplying the aqueous solution to the membrane, and spraying a water bath liquid onto the separation membrane. The temperature of the water bath should be adjusted within a range that maintains a homogeneous solution (usually treatment in the range of 10υ to 50°C for 10 to 24 hours is sufficient).

When drying the separation membrane after treating it with a sugar water bath, it may be dried naturally, by heating, by blow drying, or by vacuum drying, and the drying time is determined until the water in the membrane evaporates and the membrane reaches a constant weight. You can use either @t.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain a membrane that maintains the chemical stability of the separation membrane before treatment, reduces the amount of fractionated molecules per unit amount, and has a high permeation amount, by a simple method.

Particularly for low-middle molecule filtration, by treating conventional ultrafiltration membranes with the method of the present invention, their performance can be improved by high rejection rates,
It has a high permeation amount and can be applied to this.

Furthermore, since the present invention is obtained as a dry membrane, problems associated with storage, assembly, and transportation of conventional wet membranes are solved. Furthermore, since the treatment and drying are performed using an aqueous sugar solution, sanitary safety is improved compared to a method of immersing the product in a surfactant solution and drying it, or a method of processing using vapor of alcohol, ketone, or the like. Since the dry membrane according to the present invention can be easily rewetted, the time required for pretreatment before use can be significantly shortened, making it very practical.

〔Example〕

The effects of the present invention will be specifically explained below using Example 2 and Comparative Examples.

Example-1 Comparative Example-1 Aromatic polyetherimide ULTEM100O (manufactured by GE) 203! In a weighing section, N-methyl-2-pyrolydone was heated and dissolved in a 80-layer lid, and a resin solution of t-1111 was added. After degassing, it was cast onto a glass plate at room temperature and further immersed in 29'0 water to obtain an untreated film with a thickness of 100 to 110 μm.

In Comparative Example-1, the obtained untreated membrane was used for the entire time, and in Example-1, the untreated film was immersed in a 1 wt lactose aqueous solution at 80°C for 12 hours, and then heated and dried at 80°C for 2 hours. It was immersed in water at 20°0 for 12 hours. The performance of the separation membranes of Example-1 and Comparative Example-1 thus obtained was measured using a reverse osmosis device at an operating pressure of 20 hours/5wt of feed water in a tisucrose water bath solution and at a feed water temperature of 20°C. All are shown in Table 1.

Table 1.2. The time-dependent changes in the sucrose rejection rate and permeation amount reached a steady state 80 minutes after the start of the measurement, and there were no changes thereafter. Further, in this treated membrane, almost no change was observed in both the sucrose rejection rate and the permeation amount even after washing with water.

Examples 8-1lI-Example-IKj? 1wt% sig sugar aqueous solution? +-0
．． 1.0.6, 1.0.2.0wt% of each dextra
Table 2 shows the results of measuring the performance of treated membranes obtained by changing to the T-10 water bath solution and using other Qin systems.

Table 2 Comparative Example-2 The untreated membrane obtained in Example-1 was not immersed in the sugar aqueous solution8
It was turned at 0°0 for 2 hours and immersed in water for 12 hours. Permeation amount 4.2t/a with sucrose rejection rate 10.0%? It was hr.

Comparative Example-8 Example-I Vt spite 1wt% sugar water bath liquid r
.

When we measured the performance of the treated membrane obtained by changing to a 1wt% NhC1 aqueous solution and keeping other conditions the same, the sucrose rejection rate was 1.
4.5% transmission amount was reached after 20 hours.

Example-6 The performance of the treated membrane obtained by changing the aromatic polyether oxide to aromatic polysulfone (UL) ELP-1700 (manufactured by Union Carbide) in Example-1 and keeping the other conditions the same was measured. did. As a result, the elimination rate of sulfate sugar was 29.0%.
, transmission amount 4? t//wPhr was rare.

Claims (1)

[Claims] Aqueous sugar solution tlI inside and on the surface of the separation membrane! ! A method for reducing the fractionation of a separation membrane, which is characterized by contacting the membrane and drying it as is.