JPS61146302A - Composite ultrafiltration membrane - Google Patents

Abstract

PURPOSE:To obtain a composite ultrafiltration membrane which is small in the demarcation mol.wt. and high in the water permeability by making the crosslinking epoxy resin an activated layer. CONSTITUTION:After coating a water-ethanol soln. of a monomer contg. epoxy group on a supporting layer such as a porous membrane of non-symmetrical polysulfone, the crosslinking reaction is made to cause by heat-treating it. Then the membrane is immersed in an aq. sodium lauryl sulfate soln. and washed with water to produce the composite ultrafiltration membrane making the crosslinking epoxy resin an activated layer.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a novel composite ultrafiltration membrane useful as an ultrafiltration membrane, which has high water permeability and a small molecular weight cutoff. be.

[Prior Art] Conventionally, membranes made of a single material such as polyamide, polyimide, polysulfone, polyolefin, etc. have been known as ultra-transparent membranes (for example, JP-A-57-159508, JP-A-5
9-87007, Special Publication No. 59-14494>, recently,
In order to realize the characteristics of low molecular weight cut-off and high water permeability that are expected of ultra-transparent membranes, active research is being conducted. However, it is currently extremely difficult to achieve both of these contradictory characteristics. To explain specifically, the molecular weight cutoff is
10,000 to 20,000 is common, whereas several thousand or less are produced as paper-fractionated molecules and membranes. However, these membranes have extremely low water permeability and are of poor practical use.

Ultra-filter membranes are economical at operating pressures of 5 kq/ciF or less, and large pressures cannot be applied, so even if they have a low molecular weight cutoff, membranes with extremely low water permeability do not make sense. do not have. Because it has excellent heat resistance, chemical resistance, and mechanical strength,
Even among the most well-studied polysulfone resins,
Although various improvements have been attempted (for example, Japanese Unexamined Patent Publication No. 1983
-42003, JP-A-59-80305 > Good reproducibility,
It has not always been easy to obtain a stable and good ultra-filter. Also, as a composite membrane, one in which triazine and amine monomer are cross-linked is known (Japanese Patent Application Laid-Open No. 58-1989-1).
49404>, although the molecular weight cut-off is 10,000 or less,
The water permeation rate when evaluated with a solution of polyethylene glycol with an average molecular weight of 2,000 is 0°2 to 0.3 m'/m2・day-(kq/atf), and 0.2 m''/atf with a polyethylene glycol with an average molecular weight of 6,000. Tn”日・(ki/
cJ) and is unsatisfactory in terms of water permeability.

[Problems to be solved by the invention] The present invention overcomes the above-mentioned difficulties and has a low molecular weight cut-off.
The membrane permeate velocity is at least 0.4 m'/m2・day・(
It is an object of the present invention to provide an ultra-permeability membrane having a high water permeability of more than ki/cJ.

[Means for solving problems] The present invention has the following features.

(1) A composite ultra-diaphragm membrane comprising a crosslinkable epoxy resin as an active layer.

Composite membranes with a crosslinkable epoxy resin as an active layer are being studied as gas separation membranes and liquid separation membranes (Japanese Patent Laid-Open No. 59-13
0505, Japanese Unexamined Patent Publication No. 58-92419). however,
Ultrafiltration membranes using cross-linked epoxy resins have hardly been studied.

The present invention is based on the discovery that a crosslinkable epoxy resin in a composite ultra-diaphragm membrane reduces the molecular weight cutoff and does not significantly impair water permeability.

The support layer of the composite membrane of the present invention is a so-called asymmetric porous membrane, and the material is not particularly limited, but polysulfone resin is preferred from the viewpoint of pressure resistance, heat resistance, acid resistance, and alkali resistance.

As is already known, some polysulfones have a repeating unit represented by the following formula, and any of these may be used.

As is well known, the method for manufacturing an asymmetric polysulfone porous membrane is performed by the following procedure (for example, as described in "Office of Saline Water Research and Development Progress Report" N. ,3
59 (1968)). A solution of polysulfone dissolved in a water-soluble solvent such as dimethylformamide is applied to a reinforcing material such as a polyester nonwoven fabric or taffeta, and then coagulated (gelled) in a medium consisting essentially of water.

Next, wash with pure water. The asymmetric polysulfone porous membrane thus obtained has micropores on the surface having a size of several tens to several hundreds of pores, which become larger from the front surface to the back surface. In addition, the area occupied by pores is about 10 to 20% on the surface.
It gets wider as you go from the inside to the back. When forming an asymmetric porous polysulfone membrane, using a surfactant in the coagulation medium may be effective in improving the performance of the porous membrane.

The crosslinkable epoxy resin that serves as the active layer in the present invention is made by crosslinking a monomer having two or more epoxy groups in the molecule on a porous membrane with a catalyst, and this monomer is used as the asymmetric support layer. It must be dissolved in a solvent that does not dissolve the porous membrane.

For example, preferred examples include water-soluble epoxy group-containing compounds and alcohol-soluble epoxy group-containing compounds. Also,
The average molecular weight of the epoxy group-containing monomer is preferably smaller than the molecular weight cutoff of the asymmetric porous membrane of the support layer. In other words, when the molecular weight is large, there are fewer crosslinked sites,
Even if cross-linked, the active layer may peel off, and even if there are many reactive groups, the pores of the asymmetric porous membrane will be filled, resulting in a decrease in water permeability even if the molecular weight cut-off becomes small. This results in an ultrafiltration membrane with low practicality. Therefore, the average molecular weight of the epoxy group-containing monomer is preferably 1000 or less.

Specific examples of the above-mentioned crosslinked epoxy resin are listed below, but the present invention is not limited thereto.

(However, n is an integer from 1 to 10) (Eponite, Bunacol EX-810, EX-811
, EX-851, EX-830, EX- (Bunacol E
X-313) (Bunacol EX-314) (Bunacol EX-512, EX-521>(Bunacol E
X-301) H (Bunacol EX-611) Denacol: Nagase Kasei Kogyo Co., Ltd. product Eponite Nikitto Kasei Co., Ltd. product These crosslinking reaction catalysts are generally known as:
Although acids and alkalis may be used, zinc fluoroborate is preferable because of the speed of reaction. Further, depending on the type of epoxy-containing monomer, a catalyst may not be necessary and crosslinking may be performed by heating.

Next, the formation of a composite membrane will be explained.

The epoxy-containing monomer and catalyst are dissolved in water or a water-alcohol mixed solvent to prepare a solution. At this time, if the concentration is too high, it will block the pores of the porous membrane, which is not preferable, and the concentration should be adjusted to 10% by weight or less. This solution is applied or impregnated onto the asymmetric porous membrane, and then the temperature is typically 80-150°C.
, Preferably, heat treatment is performed at 100 to 120°C to remove the solvent and cause a crosslinking reaction. Heating time is 1 to 60 minutes.
Preferably heat for 2 to 10 minutes. The manufactured composite membrane was immersed in an aqueous sodium laurate solution (5% by weight), washed with water, and then evaluated.

[Examples] Examples of the present invention are listed below, but the content of the present invention is not limited only to the examples.

defined.

Example 1 An epoxy group-containing monomer [Ebonit 012J (manufactured by Nitto Kasei Co., Ltd.)] with an average molecular weight of m300 was mixed at 0°02%,
Zinc borofluoride was dissolved in a mixed solvent of water and ethanol (weight ratio 1:1) to a concentration of 0.02% by weight to prepare a solution. This solution was applied onto the asymmetric polysulfone porous membrane formed by the procedure described above, and heat treated at 120'C for 2 minutes.

Next, this membrane was coated with a sodium lauryl sulfate aqueous solution (5% by weight).
) and evaluated after washing with water. The evaluation conditions were polyethylene glycol (Katayama Chemical Industry Co., Ltd.) with an average molecular weight of 19,000.
Co., Ltd.) at a concentration of 2500 pDm was used as the stock solution, and the temperature was 256 C1 and the pressure was 3 ki/+, +
I did it with f. As a result, the removal rate was 60.0% and the water permeation rate was 0.60Trl! /Tr12・Sun・(ki/c
f>.

Example 2 Eponite 012J (manufactured by Nitto Kasei Co., Ltd.) was dissolved in a mixed solvent of water and ethanol (weight ratio 1:1) to a concentration of 0.1% by weight and zinc fluoroborate was dissolved in a concentration of 0.1% by weight. A solution was prepared.The asymmetric polysulfone porous membrane used in Example 1 was immersed in this solution for 2 minutes, and then heat-treated at 120°C for 2 minutes.

As a result of evaluation in the same manner as in the example, the removal rate was 70.4% and the water permeation rate was 0.60Tr1! /v2・day・(ki/cnf).

Example 3 Triglycidyl tris(hydroxyethyl) isocyanerate rDEDNAcOL EX-301'' (manufactured by Nagase Chemical Industries, Ltd.) was formed into a composite film in the same manner as in Example 2,
evaluated. Removal rate is 68.2%, water permeation rate is 0.63m
'/m2・day・(kq/cnf).

Example 4 “Eponit 012J (manufactured by Nitto Kasei Co., Ltd.) was added to water so that the amount was 1.0% by weight and zinc fluoroborate was 1.0% by weight.
It was dissolved in a mixed solvent of ethanol (weight ratio 1:1) and a film was formed in the same manner as in Example 2.The supplied stock solution was polyethylene glycol (manufactured by Wako Tsumugi Kogyo Co., Ltd.) with an average molecular weight of 16,000.
Using an aqueous solution containing 000 ppm, the rest was as in Example 1.
It was evaluated under the same conditions. As a result, the removal rate was 88.2% and the water permeation rate was 0.47TIl! /1T12・day-(kg/cn
f).

Example 5 [Ebonit 012J (manufactured by Nitto Kasei Co., Ltd.) was dissolved in a mixed solvent of water and ethanol (weight ratio 1:1) so that 2.0% by weight and zinc fluoroboride were 1.0% by weight, A film was formed in the same manner as in Example 2. The stock solution supplied is an average molecule! 2000
An aqueous solution containing 5000 ppm of polyethylene glycol (manufactured by Wako Tsumugi Kogyo Co., Ltd.) was used, and the other conditions were the same as in Example 1. As a result, the removal rate was 90.0%,
The water permeation rate was 0.40 m'/m2·day (kl/atf).

[Effects of the Invention] a. The molecular weight cutoff of the ultra-permeable membrane can be reduced without significantly impairing water permeability.

b) The molecular weight fraction can be easily controlled by changing the concentration of the epoxy-containing top solution applied or impregnated.

Claims (1)

[Claims] (1) A composite ultrafiltration membrane comprising a crosslinkable epoxy resin as an active layer.