JPS58137405A - Preparation of semipermeable membrane - Google Patents

Abstract

PURPOSE:To contrive to increase flux, by immersing a polyacrylonitrile type semipermeable membrane in an amine or an alkali solution. CONSTITUTION:A semipermeable membrane comprising a polymer containing 40mol% or more acrylonitrile and having a bubbling point of 0.1kg/cm<2> or more is immersed in a solution of amines such as ammonia, primary, secondary or tertiary amines, quaternary ammonium salt, alkanolamine or hydroxyamine or an alkali such as sodium hydroxide or pottasium hydroxide until colored. After immersion, the colored semipermable membrane is pref. subjected to plasma treatment. This invention can be applied to the semipermeable membrane having either one of a flat, a tubular and a hollow fiber like configurations or a composite membrane and this semipermeable membrane can be used as a reverse cosmosis membrane and an ultrafiltration membrane.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a semipermeable membrane using reverse osmosis and ultra-isobaric ultra-permeation consisting of a single combination of 7-crylonitrile.

In recent years, reverse osmosis and ultrafiltration processes using semi-permeable M such as cellulose acetate and polyamide have been widely put into practical use in the fields of seawater desalination, wastewater treatment, electrodeposition bath management, food industry, and medicine. It's coming. In these membrane separation processes, the mold cost is the permselectivity of the semipermeable membrane used, that is, the material exclusion ability and flux, and especially the
It would be unfair to say that it is the size of the flux that determines the stability.

From ancient times to the present, numerous studies14 have been conducted to increase the flux of semipermeable membranes used in reverse osmosis and ultra-emission treatment, and the number of studies found in patents and academic papers is too numerous to list. There is no way. Many of these are closely related to the cast film production process, so it can be said that research on increasing the flux of semipermeable membranes is inextricably linked to research on cast film production methods.

Among these, methods attempt to produce an asymmetric membrane in which the thickness of the active skin layer on the surface is made as thin as possible, and methods attempt to independently produce an ultra-thin film corresponding to the active skin layer and composite it onto another porous support. Method (3) etc. can be said to be representative, but although these can be one of the legitimate methods for increasing flux, they cannot necessarily be said to provide a general or more practical method.

On the other hand, it has been known for a long time that acrylonitrile copolymers are a material that provides semipermeable membranes. Regarding the production of semipermeable membranes made of this acrylonitrile polymer, the method disclosed in JP-A-4/7-Ar was the first method, and although many attempts have been made since then, JP-A-Sho. As discussed in Sθ-3 and 7/, semipermeable membranes made of acrylonitrile polymers have a large flux, but have a low solute rejection rate, especially when the solute is sodium chloride, a low molecular electrolyte. Although semipermeable membranes made of 7-acrylonitrile polymers are said to have a particularly low ultraviolet rejection rate,
This is also the reason why it cannot be used for reverse osmosis. As a result of intensive research into a method for manufacturing a semipermeable membrane that can eliminate low-molecular electrolytes such as sodium chloride at a high rate, we have already proposed a method for manufacturing a semipermeable membrane that can eliminate low-molecular electrolytes such as sodium chloride. The innovative method of plasma treatment of a porous polymer membrane provides superior thermal, mechanical, and chemical properties and material exclusion properties compared to conventional cellulose acetate membranes when used in reverse osmosis, etc. We succeeded in obtaining a semipermeable membrane made of an acrylonitrile-based polymer having the following properties. This represents a major advance that clearly transcends the scope of conventional technology.
Brought to the area of the body consisting of a semipermeable membrane.

The present inventors have subsequently conducted extensive research to improve the performance of semipermeable membranes made of various 7-acrylonitrile polymers, including semipermeable membranes made of plasma-treated acrylonitrile polymers. We discovered that when a semipermeable membrane made of an acrylonitrile polymer is treated with amines and/or alkali 1 on a wound by plasma treatment after incubation, the flux can be increased more than K. The present invention has now been completed.

That is, the object of the present invention is to apply a semipermeable membrane made of an acrylonitrile polymer to a solution of amines and/or alkali. L immersion or further immersion f′1f
The purpose of the present invention is to provide a method for IJMing a semipermeable membrane with excellent material exclusion properties and high flux through plasma treatment.

It is well known that when an acrylonitrile polymer is dissolved in N,N-dimethylformamide, amines or alkalis are added, and the mixture is left to stand, it will turn brown, and the colored substance is naphthyridine. It is thought that this is due to the formation of rings. When the semipermeable membrane made of the 7-acrylonitrile compound of the present invention is immersed in an amine and/or alkali solution, the semipermeable membrane becomes colored, and its infrared spectrum suggests the formation of naphthyridine rings. It is thought that the formation of naphthyridine rings impairs the material exclusion properties of the semipermeable membrane and contributes to increasing the flux.

Below, additional embodiments of the present invention will be explained in detail.

First, the acrylonitrile-based polymer constituting the semipermeable membrane used in the present invention is a six-layer copolymer containing acrylonitrile as seven components, all of which can be obtained by known methods. As the comonomer constituting the comonomer with acrylonitrile, there can be mentioned various known nonionic and ionic monomers that can be copolymerized with acrylonitrile. For example, nonionic monomers include acrylamide, diacetone acrylamide, N-vinyl-1-pyrrolidone, hydroxyethyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, r) Vinyl, vinyl chloride, styrene, etc. are also ionic monomers such as acrylic acid, methacrylic acid, (7) ethylene sulfonic acid, methallyl sulfonic acid, sulfopropyl methacrylate, vinylbenzenesulfone PIl and these. Metal salts of covinylpyridine, govinyl and lysine, tertiary amines of dimethylaminoethyl methacrylate, and 4'N alkylated
Examples include amine salts.

The 7-acrylonitrile polymer referred to in the present invention is a copolymer containing at least 90 mol percent of acrylonitrile and 6θ to θ mol percent of one or more of these comonomers. Acrylonitrile is 90 mole percent.
a.

Even if the semipermeable membrane is immersed in an alkaline solution, it does not produce a sufficient flux increase effect.
Practical 1゛16 values are no longer recognized.Therefore, acry(ni)tolyl copolymers that can be used in the present invention are preferred.

In addition, the molecular weight is s in terms of sufficient mechanical strength of the membrane.
, ooo -sθθ ten thousand are preferable.

The semipermeable membrane that can be used in the method of the present invention refers to a membrane that exhibits selectivity in permeability of substances on the molecular order.
From reverse osmosis membranes and gas separation membranes that can eliminate low molecular weight compounds of 1!00 or less, to ultraf membranes that are used in the molecular weight range of jθθ~/θ, and furthermore eliminate ultrahigh molecular weight compounds that exceed the protein molecular weight IO. However, the semi-permeable membrane made of a wide range of 7-crylonitrile polymers is used to pass through the microfilter. put air into the
When the pressure of air 4 is gradually increased, the pressure at which air passes through the membrane and comes out to the water side) must be greater than θ,/(-).

In addition, in order to carry out the method of the present invention more effectively, it is necessary that the bubbling point of the raw material semipermeable membrane is 1.
Regarding No. 1, the manufacturing method is not particularly limited, but semipermeable membranes are formed by wet casting, which consists of the steps of normal solution casting, partial solvent evaporation, and gelation, and porous membranes obtained by this wet casting. Hydrothermally treated semipermeable membranes are particularly suitable.

Furthermore, the specific forms of these semipermeable membranes include various forms such as flat membranes, tubular forms, hollow fiber forms, filament forms, and composites with other porous supports, all of which are equally applicable to the present invention. It is possible to subject it to the method of

In the present invention, there are no particular limitations on the amines used to immerse the semipermeable membrane, and amines widely known in the world can be used.

For example, the general formula (R1, R2 and R3 are H, 01 to that alkyl group,
phenyl group, aralkyl group or cyclohexyl group), a compound represented by the general formula (R1, R2, R, and R4 are H, 01 to 8, alkyl group of 8, phenyl group, aralkyl group or cyclohexyl group X is hepgen) These include compounds represented by , alkanolamines, hydroxyamines, etc.

Specifically, ammonia, methylamine, dimethylamine, trimethylamine, methylamine, diethylamine,
Triethylamine, n-propylamine, 180-propylamine, n-butylamine, di-n-butylamine, tri-n-butylamine, 1BO-butylamine,
G1s.

-butylamine, tri-180-butylamine, t-butylamine, di-t-butylamine, tri-t-butylamine, laurylamine, ste (//) allylamine, aniline, diphenylamine, methyl 7
Niline, cyclohexylamine, their quaternary salts with inorganic acids, their quaternary salts with furkylparite, and ethanolamine, jetanolamine, triethanolamine, and hydroxyamine.

Xt Shikke dimethylamine, trimethylamine, diethylamine, triethylamine, n-protoylamine, n
-Butylamine, di-n-butylamine, tri-n-butylamine, 18o-butylamine, di-1so-butylamine, tri-1ao-butylamine, t-butylamine, di-t-butylamine, tri-t-butyl 7mine, ethanolamine, jetanol Examples include amine, triethanolamine, and hydroxyamine.

1. In the present invention, there are no particular restrictions on the alkali used to immerse the semipermeable membrane, but alkali metal hydroxides are preferable. The amine and/or alkali solution used for immersing the semipermeable membrane may be used as is if it is a liquid amine or the like, and there are no particular restrictions on the concentration when used as a solution; Although it depends on the type of amine or alkali, it is sufficient that the concentration is such that the acrylonitrile polymer film is colored. Further, there are no particular restrictions on the solvent for the solution, but water, alcohols, ketones, etc. are preferably used. Especially water, methanol, ethanol, propatool, acetone,
Methyl ethyl ketone is preferred.

Furthermore, there are no particular limitations on the temperature, time, and pressure of the immersion treatment.

Also, regarding the case of plasma treatment after immersion, for example, This may be done as disclosed in Japanese Patent No. 31915. Specifically, the pressure inside the vacuum container as shown in Figure 1 of the publication is argon, nitrogen, oxygen, -
A gas such as carbon oxide, carbon dioxide, or ammonia is introduced, and a plasma is generated by applying an alternating current or direct offshore voltage θ, j to SO kilovolts between the electrodes.

In addition, it is desirable that the processing time be in the range of χ1 (Iij seconds to 6θθ minutes).

As mentioned above, the special feature of the method of the present invention is to immerse a semipermeable membrane made of an acrylonitrile polymer in an amine and/or alkaline solution, or to form a semipermeable membrane by plasma treatment after immersion. It is possible to increase the flux without compromising exclusivity.

Half obtained by the method of the present invention! ! ! The membrane has significantly increased flux without impairing the material exclusion properties of the conventional 7-acrylonitrile polymer semipermeable membrane, so it has a large economic effect and may be practical in 11 industries. It is.

That is, the semipermeable membrane obtained by the method of the present invention can be widely used in the separation of substances by reverse osmosis, ultra-21"I filtration, etc., and more specifically in seawater desalination, wastewater treatment, and fruit juice concentration. , non-aqueous fluid separation and other processes, the present invention is also applicable to immersion in inorganic saline water or fi
Immersion in protons as disclosed in 1997 (-/3θ) or % Fu Show 33-7359/
The effects of the present invention are also significantly exhibited when combined with inventions such as hot water treatment as disclosed in No. 9, and these cases are also within the scope of the present invention.

The present invention will be explained in more detail with reference to the following examples, but the present invention is not limited to these examples in any way.

Note that the solute exclusion rate is defined by the following formula.

Rejection rate (@= (/-1 liter of permeate/concentration of stock solution) x/
θθ Example/A comonomer consisting of acrylonitrile zata mole percent and methyl acrylate/1 mole percent was synthesized by a known method. After dissolving 0 parts of this typical (/j) combination in a mixed solvent consisting of 70 parts of N,N-dimethylformamide and 70 parts of formamide, 90 parts of
IIy of F9ilrt on a glass plate warmed to °C.
After evaporation time of 01 minutes, the glass plate was cast to a thickness of 50 μm, and then placed in a water bath at 70° C. to gel. After one hour, the peeled film was taken out from the glass plate and dried for 2 hours at room temperature. Its bubbling point is 32
Ky, it was zrd. Then, under the treatment conditions shown in Table 1, it was immersed in amines or alkalis and subjected to τC treatment F11, washed with water, and dried at room temperature for q hours.
The plasma processing regulations are as follows: 0 Atmosphere Gas: Helium Vacuum Degree: θ, Co'rorr (/A) Discharge current :JjmA Processing time: 4/θ minutes Then do normal experiments with these films? Circulating reverse osmosis equipment used in (effective membrane area 2/3.0-) K! Wearing the 4th coat, we conducted a permeation test for saline <o, 5ytc amount percent)□
Add saline solution of jj”c to the cell for 1 s under the pressure of j OV-.
X) yxl/min and measured the flux and salt rejection rate for −q hours after the start of the experiment, as shown in Table/
The values shown are obtained. Increased flux due to amine or alkali immersion treatment; 0 examples observed - Acrylonitrile 90 mole percent and vinyl acetate 70
A co-l-coalescence consisting of mole percent was synthesized by known methods.

27 parts of this polymer was added to N,N-dimethyl Honlumami #t6.
? After dissolving in a mixed solvent consisting of #t/θ parts of formamide, the thickness of the solution is -jθμ at room temperature -5°C.
77 after evaporation time of 0/min cast to be
The glass plate was placed in a water bath at ℃ and allowed to gel.

The peeled film was removed from a glass plate for 1 hour and dried at room temperature for 1 hour. The bubbling point of the membrane is 35 (
This film was immersed in amines or alkali under the conditions shown in the table, washed with water, and dried at room temperature.

The desalting performance of these membranes was measured in the same manner as in Example 1 and rM1. The results are shown in Table 1, and it was found that the immersion treatment with amines or alkali increased the corrosion rate.

(−〇)

Claims (1)

[Claims] (1) Acrylonitrile from 90 mol percent to 10
A semipermeable membrane made of a 7-acrylonitrile polymer containing θ mole percent and having a bubbling point of θ, l(- or more) is immersed in an amine and/or alkaline solution. Method for producing a permeable membrane. R3 is HSCl, an alkyl group, a phenyl group, a 7-ralkyl group, or a cyclohexyl group.) (F!1, R
2, R3o and R3 are a, c, ~, 7 alkyl group, phenyl group, aralkyl group or cyclohexyl group,
Or halogen. ), alkal hepamines or hydroxyamines ◇ (3) The amines are aliphatic primary, primary or secondary amines. The method for producing a semipermeable membrane according to claim 1, wherein the alkali is tertiary amine, alkanolamine, or hydroxylamine.Claim 12, wherein the alkali is sodium hydroxide or potassium hydroxide. A method for manufacturing the semipermeable membrane described. 7) Consisting of an acrylonitrile polymer containing 0 to 1 mole percent of acrylonitrile,
A method for producing a semipermeable membrane, which comprises immersing a semipermeable membrane having a bubbling point of θ,/KfA or more in an amine and/or alkaline solution and then subjecting it to plasma treatment. R3 is 0° (R1,
-1R1 and to are alkyl group, phenyl group, aralkyl group or cyclohexyl group with H% Cl to 18, and x#'i halogen. ), an alkanolamine, or a hydroxyamine. (7) The method for producing a semipermeable membrane according to claim 1, wherein the amine is a primary, secondary, or tertiary amine of fat λ, an alkanolamine, or a hydroxylamine. b) The method for producing a semipermeable membrane according to claim 4, wherein the alkali is sodium hydroxide or potassium hydroxide.