JPH0638899B2 - Membrane treatment method - Google Patents

Description

The present invention relates to a method for post-treating a membrane. More specifically, the present invention relates to a membrane treatment method of treating a cellulosic membrane having an average diameter 2ra of 10 μm or less with liquid ammonia or a mixed solution of liquid ammonia and a solvent to change various physical, chemical or physiological characteristics of the membrane.

[Conventional technology]

With the development of membrane separation technology, the performance expected of membranes is becoming more and more sophisticated. For example, regarding the pore size, make the width of the pore size distribution as narrow as possible, arrange a large number of pore sizes from large to large, withstand long-term use, and do not change the pore size during use, etc. Is. In particular, higher required performance is expected for the cellulose diameter membrane, which is most used as a biochemical or medical separation membrane. Conventionally, a technique for controlling the pore size during film formation has been developed by adopting various film formation principles or changing the concentration of a polymer substance in a stock solution for film formation. However, although such a pore size control during film formation is possible in principle, it is difficult to achieve more precise and continuous pore size control on an industrial scale, and it is also disadvantageous in terms of cost. Is.

On the other hand, a liquid ammonia treatment technology of regenerated cellulose has been known as a method for improving the dimensional stability of fibers (Japanese Patent Laid-Open No. 58-54071, etc.). Is not disclosed. The microstructure of regenerated cellulose fibers differs greatly from the microstructure of a membrane intended for substance permeation in terms of crystallinity and porosity. In particular, considering the pore characteristics of the membrane, the membrane is a three-dimensional structure in which the pore diameter and the pore length can be clearly defined, and the effect on liquid ammonia cannot be discussed in the same dimension as the fiber.

Further, JP-A-58-54070 describes a method for treating regenerated cellulose fibers with a mixture of an organic solvent compatible with liquid ammonia and liquid ammonia. This method was a method of suppressing the swelling property of the fiber surface layer portion and preventing fusion between yarns in order to prevent the flexibility of the fiber from being reduced due to the modification. In addition, both the action and effect of the present invention and the field of use of the treated product are different from those described above.

[Problems to be solved by the invention]

It is an object of the present invention to provide a method for controlling the pore size by post-processing of cellulosic membranes and thus modifying the physical, chemical and physiological properties of the membranes.

Here, the "cellulosic membrane" means a copper-ammonia method regenerated cellulose membrane, a viscose rayon method regenerated cellulose membrane,
Also, it refers to a membrane using a cellulose derivative such as cellulose acetate or cellulose nitrate as a raw material polymer, or a saponified regenerated cellulose membrane obtained by saponifying these cellulose derivatives. Further, the "membrane" means an average pore diameter of 2ra.
(Ra is an average pore diameter) is a structure having pores having a diameter of 10 μm or less and having a planar shape, a hollow fiber shape, or a tube shape. Depth type filters, such as so-called filter paper, on which fibers are deposited are not included in the membrane of the present invention.

[Means for solving problems]

The membrane treatment method of the present invention for solving the above problems has pores having an average pore diameter 2ra (ra is an average pore radius) of 10 μm or less, and has a copper-ammonia regenerated cellulose, a viscose rayon regenerated cellulose, or a cellulose derivative. And liquid ammonia which can be mixed with liquid ammonia or liquid ammonia in one-phase state on both sides or one side of a membrane made of a cellulosic polymer selected from regenerated cellulose obtained by saponification method and cellulose derivative Contact the treatment liquid consisting of the mixed liquid with, and then under tension or without tension while adjusting the tension below the breaking strength of the membrane.
It is characterized in that the film of the treatment liquid is evaporated under an atmosphere of 40 to 140 ° C.

In the membrane treatment method of the present invention, the membrane to be treated with liquid ammonia or a mixed solution thereof is a cuprammonium regenerated cellulose, a viscose rayon regenerated cellulose, a cellulose derivative such as cellulose acetate or cellulose nitrate, and cellulose acetate or cellulose nitrate. A membrane composed of at least one cellulosic polymeric substance selected from regenerated cellulose obtained by saponification method obtained from the cellulose derivative having a semi-uniform pore diameter of 2 ra (ra is an average pore radius).
Is a film having pores of 10 μm or less. Among these polymer materials having a cellulose diameter, copper-ammonium regenerated cellulose, viscose rayon regenerated cellulose, and saponified regenerated cellulose obtained from a cellulose derivative are preferable. In particular, the copper-ammonia method regenerated cellulose is the most preferable because it has good dimensional stability when the final product is swollen with water and the liquid ammonia treatment time is relatively short. Although the reason why the copper-ammonia method regenerated cellulose is superior in this way is unknown, it is considered that the microstructure of the film (skin / core structure, crystalline / amorphous region distribution, etc.) and the degree of saponification completeness have an influence. .

The cellulosic polymer material as described above may be a flat membrane or a hollow fiber membrane as long as its average pore diameter 2ra is 10 μm. Membranes having an average pore size 2ra of 10 μm or less are known, and the membranes treated in the present invention can be prepared by known techniques.

The treatment liquid is composed of liquid ammonia alone or a mixed liquid of solvent and liquid ammonia that can be mixed with liquid ammonia in a single-phase state. As a solvent used in combination with liquid ammonia, any one that can be mixed with liquid ammonia in a single layer can be expected to have a treatment effect, but water, alcohols, and ketones are preferable. The alcohol preferably has 6 or less carbon atoms, and the ketone preferably has 5 or less carbon atoms. More specifically, methanol and ethanol are preferable as the alcohol,
Preferred ketones are acetone and methyl ethyl ketone.

It is preferable to use a mixed liquid of liquid ammonia and the above-mentioned solvent as the treatment liquid, as compared with the case where the liquid ammonia alone is used as the treatment liquid, because the amount of decrease in the average pore diameter can be significantly changed. Further, the composition of the mixed solution is not particularly limited,
The average pore size can be controlled almost freely by changing the composition.

The treatment liquid can be treated by contacting one side or both sides of the membrane. When only the inner surface of the hollow fiber membrane is treated, it can be achieved by flowing the treatment liquid into the hollow portion. If the hollow fiber membrane is immersed in the treatment liquid with both end surfaces closed, only the outer surface can be treated. By immersing the hollow fiber membrane in the treatment liquid with both end faces open, both inside and outside of the hollow fiber membrane can be treated. The flat membrane can be treated on both sides by immersing it, and can be treated on one side by floating it on the treatment liquid.

Processing time is generally very short, at most 5
It is less than a minute.

After the treatment, the treatment liquid is evaporated from the membrane under tension or without tension while controlling the tension to be equal to or lower than the breaking strength of the membrane in an atmosphere of 40 to 140 ° C. In the present invention, the method of removing the treatment liquid by replacing the treatment liquid with water is not adopted. If the dry atmosphere exceeds 140 ° C, a part of the film is decomposed, which is not preferable. If the temperature is lower than 40 ° C, the water content in the air is condensed on the film, it takes time to dry, and the average pore size reduction rate is small, resulting in poor efficiency.

In the case of hollow fibers, if the inner diameter exceeds 2 mm, it is difficult to dry the hollow fibers while holding the hollow portions after processing. The hollow fiber preferably has an inner diameter of 2 mm or less.

Further, in the case of hollow fibers, as a drying method when the treatment liquid is fed into the hollow portion, a gas of 40 to 140 ° C. is positively introduced into the hollow portion,
(Usually, a method of feeding in and evaporating ammonia or an organic solvent gas and inert air, nitrogen gas, etc.) is efficient, and the treatment effect (average pore diameter reduction amount) is large.

Prior to the examples, the measuring methods of the respective physical property values are shown below.

Pure water having an average pore diameter of 2a at 25 ° C is filtered through a polycarbonate porous membrane having a pore diameter of 0.2 µm (trade name: unclepore, manufactured by General Electric Co.) to prepare pure water having no fine particles. If the filtration rate J (cm / sec) per unit area of the sample porous membrane at a constant pressure difference ΔP (cmHg) is measured using this pure product, it is 2
a (cm) is calculated by the following equation.

Here, ηw is such that the viscosity of pure water is usually 1 centipoise. d is the thickness of the film (cm) and is measured with a micrometer.

Porosity Pr Pr is calculated by the following equation from the measured value of the apparent density ρa of the porous membrane.

Pr = (1−ρa / ρp) × 100 (percentage display) (2) where ρp is the density of the porous membrane material, ρa is the measured value of the thickness d, weight W, and area S of the porous membrane ρa = W It is calculated by / S · d.

Examples Hereinafter, the film treatment method of the film of the present invention will be specifically described with reference to Examples.

Example 1 A regenerated cellulose microfilter (saponified cellulose derivative, manufactured by Toyo Roshi Kaisha, Ltd., nominal pore size 1.0 μm) was dipped in liquid ammonia, a mixture of liquid ammonia and ethanol or a mixture of liquid ammonia and methanol for 60 seconds, It was dried at 20 ° C, 45 ° C, and 160 ° C for 5 minutes without tension. After leaving in a desiccator for 24 hours and further drying, the porosity was determined from the thickness, area and weight of the membrane, and the average pore diameter was measured from the water permeation rate. The results are shown in Table 1. 160
At ℃, the film changed due to partial decomposition. At 25 ° C, moisture in the air was condensed, so that it was not completely dried in 5 minutes.

By treatment with liquid ammonia, a liquid mixture of liquid ammonia and ethanol or a liquid mixture of liquid ammonia and methanol, the average pore diameter of the membrane is reduced. When ethanol or methanol is mixed with liquid ammonia at a ratio of 50% by volume or less, the amount of decrease in average pore size due to the treatment is larger than that when treated with liquid ammonia alone. Drying at 20 ℃ requires more time to dry, and the average pore size is less reduced than at 45 ℃, resulting in poor efficiency.

Inventive Examples 1 to 6 and Comparative Example 8 were dried at 45 ° C.

Comparative Examples 9 and 10 were dried at 20 ° C.

Example 2 A regenerated cellulose microfilter (saponified cellulose derivative, manufactured by Toyo Roshi Kaisha, Ltd., nominal pore size 1.0 μm) was mixed with methanol, n-butanol, n-propanol, n-amyl alcohol, n-hexyl alcohol, ethylene glycol, water or Then, the sample was dipped in a mixed solution of these solvents and liquid ammonia for 60 seconds, air-dried (45 ° C.) in the same manner as in Example 1 and dried by a decanter, and then the average pore diameter was determined by a water flow rate method. The results are shown in Table 2.

When immersed in 100% liquid ammonia, the average pore size is 0.71
The thickness was 13 μm, the porosity was 0.54 and the film thickness was 132.9 μm.

As the proportion of liquid ammonia in the mixture increased, the average pore size of the treated membrane decreased. The average pore diameter of the membrane could be controlled by changing the mixing ratio of these solvents and liquid ammonia.

Example 3 Regenerated cellulose microfilter (keloid of cellulose derivative, manufactured by Toyo Roshi Kaisha, Nominal pore size 0.2 μm, 0.45 μm,
(1.0 μm, 3.0 μm) was immersed in liquid ammonia for 60 seconds, air-dried (45 ° C.) and desiccator dried in the same manner as in Example 1, and the average pore diameter was determined by the water flow rate method. The progress is shown in Table 3.

The pore size of all membranes was reduced to 1/10 to 7/10 of the untreated one by liquid ammonia treatment.

Example 4 Liquid ammonia or a 1: 1 mixed solution (volume ratio) of liquid ammonia and acetone was passed through the blood flow path side of an artificial kidney AM-10 (copper ammonia method regenerated cellulose hollow fiber module) manufactured by Asahi Medical Co., Ltd. The treatment liquid was brought into contact with the inner surface for 60 seconds, and 80 ° C. dry hot air was immediately flown into the hollow fiber.
Then, vacuum drying was performed at 40 ° C. for 18 hours. After the treatment, there were no abnormalities such as breakage and yarn breakage in the hollow fiber and the module.

Ovalbumin (MW = 43,00 at a concentration of 500 ppm in saline)
0), chymotrypsinogen (MW = 25,000), and cytochrome C (MW = 12,400) were each dissolved to prepare a protein solution stock solution. Each stock solution was independently introduced into the blood channels of treated AM-10 and untreated AM-10, and the membrane permeated filtrate was collected under a pressure of ² kg / cm ² with the blood channel outlet closed. The protein concentration of the stock solution and the filtrate was determined from the absorbance at UV 280 nm, and the protein inhibition rate of the membrane was calculated. The results are shown in Table 4.

From Table 4, the untreated membrane has a molecular weight cut-off (CMW) of about 30,000,
Approximately 15,000 for liquid ammonia treated film, liquid ammonia /
It was 12,000 or less for the acetone-treated film.

Example 5 Cellulose linter (clay average molecular weight 2.3 × 10 ⁵ ) was dissolved in a copper ammonia solution prepared by a known method at various concentrations of 4 to 12% by weight, and then 12% by weight of acetone was added to the solution. After adding and stirring, the solution is cast with a 250 μm-thick applicator onto a glass plate placed in an atmosphere of acetone vapor atmosphere of 30 ° C. where the concentration of saturated vapor pressure is 80%.
After leaving it in the atmosphere for 60 minutes, add it to a 20 ° C sulfuric acid aqueous solution for 15 minutes.
Soak for a minute, then wash with water, absorb the moisture with filter paper,
By immersing the film in acetone at 20 ° C for 15 minutes to replace the water in the film with acetone, and air-drying it with a filter paper for 30 minutes, the average pore diameter was 2ra = 0.1 μm, the film thickness was 25 μm, and the porosity was Pr = A 67% recycled cellulose porous membrane was prepared. The membrane was immersed in a liquid mixture of liquid ammonia and acetone in a volume ratio of 1: 1 for 60 seconds, and then the treatment liquid was evaporated from the membrane without strain for 5 minutes at 40 ° C. The film thickness, porosity, and average pore size were measured and found to be 22 μm, 40%, and 0.02 μm, respectively.

Claims (11)

[Claims] 1. The average pore diameter 2ra (ra is the average pore radius) is 1
A membrane made of a cellulosic polymer material having pores of 0 μm or less and selected from cuprammonium regenerated cellulose, viscose rayon regenerated cellulose, cellulose derivatives and saponified regenerated cellulose obtained from cellulose derivatives. A treatment liquid consisting of liquid ammonia or a mixed liquid of liquid ammonia and a solvent that can be mixed with liquid ammonia in a single-phase state is contacted on both sides or one side, and then tension is applied while adjusting the tension below the breaking strength of the film. Alternatively, a film processing method characterized in that the above-mentioned processing liquid is evaporated from the film in an atmosphere of 40 to 140 ° C. without tension. 2. A regenerated cellulose selected from copper-ammonium regenerated cellulose, viscose rayon regenerated cellulose, and saponified regenerated cellulose obtained from a cellulose derivative. The film treatment method according to item 1. 3. The method for treating a membrane according to claim 1, wherein the material polymer constituting the membrane is a copper-ammonia method regenerated cellulose. 4. The membrane according to any one of claims 1 to 3, wherein a hollow fiber membrane is used as the membrane, and a treatment liquid is flown into the hollow portion to treat only the inside of the hollow fiber membrane. Processing method. 5. A hollow fiber membrane is used as the membrane, and the membrane is immersed in a treatment liquid to treat both the inner and outer surfaces of the hollow fiber membrane or only the outer surface of the hollow fiber membrane. The described membrane treatment method. 6. The method according to claim 1, wherein a flat membrane is used as the membrane, and the membrane is dipped in the treatment liquid or floated on the treatment liquid to treat both or one side of the membrane with the treatment liquid. The membrane treatment method according to any one of 1 to 3 above. 7. The membrane according to any one of claims 1 to 6, wherein the solvent is water or a compound having a melting point of -30 ° C. or lower selected from alcohols and ketones. Processing method. 8. The film processing method according to claim 1, wherein the solvent is an alcohol having 6 or less carbon atoms or a ketone having 5 or less carbon atoms. 9. The membrane treatment method according to any one of claims 1 to 8, wherein the solvent is methanol, ethanol, acetone or methyl ethyl ketone. 10. The membrane treatment method according to any one of claims 1 to 5 and 7 to 9, wherein the form of the membrane is a hollow fiber having an inner diameter of 2 mm or less. 11. A hollow fiber is used as a membrane, the treatment liquid is fed into the hollow portion, and then a gas at 40 ° to 140 ° C. is fed into the hollow portion to evaporate the treatment liquid. 11. The film processing method according to any one of items 5 to 10, and 7 to 10.