JPS5858103A - Separation membrane - Google Patents

Abstract

PURPOSE:To obtain a separation product containing a specific component in an increased ratio from a gas mixture, by mainly forming a separation membrane from a block copolymer having a polyamino acid molecular chain into which a polyurethane molecule is introduced. CONSTITUTION:A separation membrane is mainly formed from a block copolymer having a polyamino acid molecular chain into which a polyurethane molecule is introduced and the thickness thereof is adjusted to 1-500mu. In preparing this block copolymer, amino acid-N-carboxylic acid and an urethane polymer having an isocyanate group at the terminal thereof is copolymerized at 10-40 deg.C in the presence of amines. This membrane is excellent in selective permeability of a gas and can be utilized in separation of methane and helium in helium recovery from natural gas or separation of hydrogen and argon in the concn. of hydrogen from the waste gas of hydrogenation reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a separation membrane. More specifically, substance mixtures,
* Separation product with an increased proportion of specific seismic components from the gas mixture,
The present invention relates to a separation membrane formed of a block copolymer in which polyurethane molecules are introduced into the molecular chains of polyamino acids, which is used for the purpose of obtaining a composition.

In order to obtain a separated product with an increased ratio of specific components from a mixture of substances, conventional methods include distillation for liquid mixtures, extraction for solid mixtures, cryogenic separation, adsorption/desorption, and membrane separation for gaseous mixtures. For example, for solid and liquid mixtures, P uniform force is applied. Currently, membrane separation methods are
As water/solute permeation membranes, it is also applied to dialysis membranes, ultra-V membranes, reverse osmosis membranes, and ion exchange membranes, which are widely used in dialysis membranes, gas separation layers, Many organic liquid separation membranes and bio-related membranes are under research or development, and there are only a few examples of them being applied.

Separation by distillation has problems such as consuming a large amount of energy and making it difficult to separate substances with similar boiling points.Although there have been attempts to separate gases and liquids using membrane separation methods, they are still insufficient. I haven't gotten anything to be satisfied with. If the development of membrane materials that can freely separate and purify gases and liquids for this purpose is achieved, the development effects will be as follows.

(1) Innovation in separation and purification processes in the chemical industry (a)
Making chemical plants more compact and resolving location issues (b) Energy saving effect - Current method, separation energy (2) Waste water and waste gas treatment → Realization of a clean society without pollution On the other hand, currently under development Few gas separation membranes have sufficient performance.

The current status of gas separation membranes is as follows.

The performance required for gas separation membranes is of course that the ratio of permeation rates of various gases is high and the separation rate (gas selectivity) is high, but in addition, the permeation rate itself is also required to be ultimately high. It will be done.

The gas permeation rate through a membrane is compared as the permeation amount per unit membrane area, unit time, and unit pressure difference, but when the area, time, and pressure difference are constant, the ease of gas permeation is compared. Due to the properties of the membrane material itself and the fact that it is often substantially involved in separation, a high permeation rate can be obtained by using a material that is easily permeable to gas and making the membrane as thin as possible. However, materials that are easily permeable to gases have low separation properties, and if the membrane thickness is reduced below a certain limit, the inherent separation properties of the membrane will be impaired. It is difficult to achieve both.

In order to solve this problem, it is necessary to select a membrane material that has high separation properties even if it loses some degree of gas permeability, and to take on the challenge of creating an ultra-thin membrane.

Currently, the following types of film forming methods are generally known for increasing the permeation rate.

■ Making a uniform 51L membrane into an asymmetric membrane ■ Making a homogeneous ultra-thin membrane into a composite membrane ■ Development of liquid management and facilitated transport membrane ■ Hollow system module ■ is an asymmetric membrane consisting of a dense layer and a porous layer, and depending on the material, There are drawbacks such as the inability to obtain a solvent system suitable for the membrane forming method and the reduction in separation performance when the thickness of the dense layer is smaller than o or iμ.

(2) can take various composite forms.

For example, (a) a method in which a porous membrane is used as a support membrane and a homogeneous ultra-thin membrane made of another material is composited thereon.

(b) A method of polymerizing another material in the form of a thin film on the surface of a porous membrane to impart separability.

(c) There is a method of coating the surface of a porous membrane made of a material with high separability with a material with lower separability.

Among these, (a) requires advanced film-forming technology to obtain an ultra-thin film with a thickness of θ,/μ or less, and it seems that the materials used to composite this are also limited.

(B) depends on the pore size on the surface of the porous membrane, but if the thickness of the membrane obtained by polymerization is not at least 10 times the pore diameter, it is difficult to provide separability because defects are likely to occur. It is difficult to provide separability when the thickness of the layer deposited on the film is less than θ,/μ.

(c) The separation property of the membrane after coating is high and the permeation rate is high.This is a highly interesting method, but the separation property is 11iiiI (as long as it is based on a membrane material with a low permeation rate, the permeation rate is low. There seems to be a limit to improvement.

(Rike uses liquid, but also butterfly, reactive storehouse (support)
This is a membrane that attempts to provide greater separation and permeability through anchorage.

However, at present, liquid membranes have not been widely used due to their low separability. Furthermore, facilitated transport membranes have not been put to practical use because they lack stability.

(2) is implemented to increase the narrow area.

The main objective is to increase the amount of permeation, so in order to improve separation, the membrane area must be increased and the number of thread bundles must be increased to create a system.

Since the materials for manufacturing hollow fibers are limited, maintenance is difficult.

The currently used layer separation methods are: 1. The properties of the membrane material (
(Permeability and separability are in an inverse relationship), so in order to maintain separability and not impair permeability, the surface is coated with 15Ill. Therefore, since it is a thin film, it may not be able to exhibit sufficient separation properties, and defects such as pinholes may easily occur.
Yes, because it indicates unstable quality.

Therefore, in order to stably and economically produce a membrane that does not impair permeability using a material that has properties, the homogeneous polymeric material itself must not impair permeability.

Polyamino acids form a film similar to animal skin, exhibit good moisture permeability and heat resistance, and have a CO permeability of 02.
This is the only homogeneous polymer membrane that has permselectivity for □, and due to its biocompatibility, its application to special uses such as artificial lungs is also being studied. However, the elasticity, processability, and mechanical properties of the membrane are insufficient for use in many applications, and no method has been found to improve permeation.

On the other hand, polyurethane is a flexible and strong film with high elongation at break and high tear resistance, and has lower gas permeability than polyethylene, but it is known as one of the relatively large materials among plastic films. There are, but there are a few
Does not show body separation of less than Oμ.

The present inventors investigated materials that have the permselectivity of polyamino acids, the permeation rate of rubber-like molecules, and mechanical properties.The present inventors discovered a block in which a molecule having a urethane bond was introduced into the molecular chain of polyamino acids. The copolymer membrane is a separation membrane,
In particular, we have discovered that it has distinctive properties as a gas separation membrane, and have arrived at the present invention. 5. That is, the gist of the present invention resides in a separation membrane, particularly a separation membrane for gases, whose living body is a block copolymer in which polyurethane molecules are introduced into the molecular chains of polyamino acids.

The characteristics of the separation membrane made of a block copolymer in which polyurethane molecules are introduced into the polyamino acid molecular chains of the present invention are as follows: ■ It maintains separation properties without impairing its permeability. It has elasticity and post-resiliency, and has excellent mechanical properties as a membrane.

The present invention will be explained in detail below.

The polyamino acid-urethane copolymer resin used in the present invention is, for example, disclosed in Japanese Patent Publication No. 110-7, No. 33-73
It is a block copolymer in which a polyurethane molecule is introduced into the molecular chain of polyamino acids, which is prepared according to the method described in the publications of No. 236 and Japanese Patent Publication No. It is produced by copolymerizing a urethane polymer having the following formula and an amino acid-N-carboxylic acid anhydride produced by reacting an amino acid or an amino acid ester with phosgene in the presence of an amine.

Specifically, it can be produced by the following methods (1), (2), and (2).

- ■ Amino acid-N-carboxylic acid anhydride (in the following,
After mixing this amino acid (NCA) and a urethane prepolymer having an incyanate group at the end, amines are added and reacted.

(2) Main amines are added to a urethane prepolymer having an isocyanate group at the terminal, polymerized, and then the amino acid NCA is added and reacted.

(2) The reaction product of (2) is further reacted with a urethane prepolymer having an isocyanate group at the end.

The reaction formula is as follows: □ □ Reaction formula (a) When using a 7th class diamine 2 →...-HNR'5HcoNHR"yHco(NH
caao+n...(b) When using jN amine R1 Reaction formula of ■ (However, when the number of moles is B>A) Set this part as R1 Reaction formula of ■ % Formula % (These formulas, (R1-R4 indicate the residues of the respective components) Amino #NCAs include those obtained by phosgenation of α-amino acids or α-amino acid esters (where R7 represents hydrogen or -valent organic residues). It will be done. Examples of the α-amino acid or α-amino acid ester used as a raw material include glycine, alanine, aspartic acid β-methyl ester, lysine, and glutamic acid r-methyl ester (including D and Lm).

As a urethane polymer having an incyanate group at the end, the equivalent ratio of incyanate and polyol is NC01.
It is obtained by reacting under the conditions of 0H) /,
As the incyanate component, aromatic diisocyanate,
Aliphatic diincyanates and mausoleum diincyanates may be used alone or in mixtures thereof. For example, toluene diisocyanate, g'-diphenylmethane diisocyanate, metaphenylene diisocyanate, /, 6-hexane diisocyanate, /, lO
-decamethylene diisocyanate, /, j-cyclohexane diisocyanate, 3-incyanate methyl-,
i, s, s -)limethylcyclohexyl isocyanate (isophorone diisocyanate) and the like.

As the polyol component, polyether glycol and polyester glycol that are used in ordinary urethane products can be used.As the polyether glycol, polyethylene glycol, polypropylene ether glycol, polytetramethylene glycol, and bisphenol A and ethylene oxide or globin oxide can be used. Polyaddition reaction dynamics with etc. are appropriate.

As the polyester glycol, those obtained by reacting diols such as polycabrolactone glycol or ethylene glycol/≠butanediol with dihydrochloric acid such as adipic acid, sebacic acid, and succinic acid #2 are used. The number average molecular weight of these polyethers and polyesters is preferably 200 to 300 or more, and they are used singly or as a mixture thereof.

As the amines used in the production method (2), those represented by the following general formula are suitable.

Re (Re, Re, RI@ and R11 are hydrogen or a hydrocarbon group with a prime number l~/co.R1'' is a carbon number λ
~ 10 linear and cyclic alkylene groups or benzene and combination benzene mounds) 9) Alcohol amines such as human diamine, ethylene diamine, pupa/diamine, seven-class alkyl amine, methanolamine, ethanolamine, etc. , tertiary alkylamines such as triethylamine and tributylamine, and secondary amines such as diethylamine and dipropylamine. The amines used in the production method of
10 and Ru are hydrogen or a swollen hydrogen group having 1 to 2 carbon atoms, and are at least two active hydrogens or a group having active hydrogen, and R''' may be the same as in the case of production method (2).

Amino acid NCA and urethane prepolymer O weight ratio
:j-io: ri is in the range of 0, preferably ri o',
io~lo: 20 and preferably ♂Q:ko O~-
The amount of amines used in the production method (2) above is preferably 0.00/~i,o times the amount of amino acid NCA.

It is necessary that the amount of water or amine used in the above manufacturing method be greater than the amount of isocyanate consumed in the urethane prepolymer.

Reactions (1), (2) and (2) are preferably carried out in an organic solvent, such as methylene dichloride, ethylene dichloride,
Chlorinated expanded hydrogen such as chloroform, ethers such as dioxane, tetrahydro-72, diethylethyl, dimethylformamide, dimethylacetamide, etc. are used.

The resin concentration during the production of polybanoic acid-urethane copolymer resin is in the range of 3 to 30% by weight, but preferably in the range of 70 to 30% by weight. If Amasho #If is too low, the viscosity of the resulting resin solution will be low, and if 11 degrees is too high, the viscosity will be extremely high and it will become gel-like, making it difficult to obtain a practical product.
The temperature during production of the polyamino acid-urethane copolymer resin is preferably a temperature at which a high molecular weight polyamino acid can be synthesized from the amino acid NCA, and is preferably in the range of /θ to μθ°C. When the temperature is increased to 4Io℃, the amino acid chain becomes α- during copolymerization.
Since it becomes difficult to form a helipress form, the degree of polymerization of the amino acid chain may not increase, making it difficult to obtain a resin with a high molecular weight or high viscosity.

The resin solution obtained by the above method is emulsified and viscous.
/ 00 ap8~j 0,000 cps can be obtained with any viscosity.

Therefore, although the separation membrane of the present invention uses the polyamino acid and urethane gastrointestinal copolymer obtained as described above as a membrane material, it does not significantly lose its properties as a membrane. , an organic substance, an inorganic substance, and the like. The film forming method is not particularly limited, and the known in-solution casting method may be used. However, favorable results are obtained only under film forming conditions suitable for the present invention.

The separation membrane of the present invention is composed of two layers: a dense layer that provides second separation due to the dissolution and diffusion of gas into the membrane, and a porous layer that does not exhibit separation due to the dissolution and diffusion of gas into the membrane. Asymmetric membranes or composite membranes are used because they can easily achieve high permeation rates and separation performance at the same time, but even a single layer consisting only of a dense gas-separating layer is used. Even if you do not use an ultra-thin film, which is accompanied by technical instability, the material does not reduce the rate of permeation through the membrane material, so even a single membrane with a thickness of about lμ-5OOμ can be used. In addition to its separability, it does not reduce permeability, so it is suitably used.

Here, the term "dense layer" refers to a layer that is dense and non-porous and exhibits substantially the same separation of gas or vapor as the constituent material of the layer. , has a sponge-like structure through which gas can freely pass through the open pores, and because the gas or vapor moves along the pores, it has separation properties based only on the pore diameter for the gas or vapor passing through the layer. means layer. The thickness of the dense layer is preferably 0.0/~10μ in consideration of the transmission rate.

The thickness of the porous layer is preferably 70μ or more, especially 30~/θθμ in terms of mechanical strength, but it should be made even thinner when other porous membranes are used together as a support for the membrane of the present invention. I can do it.

A gas separation membrane consisting of a dense layer and a porous layer as described above can be manufactured, for example, by the following method. That is, (a) two types of solvents that have at least a JO°C boiling point difference and serve as a solvent for the polymer (among the two types of solvents,
(more volatile solvents are hereinafter referred to as "light solvents" and less volatile solvents are hereinafter referred to as "heavy solvents") or have a boiling point higher than the light solvent and are non-bathing solvents for the polymer. A solution prepared by dissolving a polyamino acid-urethane copolymer resin in a three-component mixture consisting of one type of solvent while maintaining the temperature below aO ℃ is heated on a support.b) Mainly, all or part of the light solvent is evaporated. c) Treating the resulting film with a coagulating liquid (non-solvent) and (d) drying the film. The light and heavy solvents are aliphatic and aromatic such as cyclohexane, benzene and toluene. The solvent is suitably selected from hydrocarbons, dihydrogen halides such as dichloromethane, dichloroethane, tetrachloroethylene, dichlorobenzene, and sulfur benzene, and water-soluble solvents such as dioxane, dimethylformamide, dimethyl sulfoxide, and the like.

Nonsolvents include water and alcohols such as methanol, ethanol, and primary, secondary, and tertiary butanols. A specific example of a combination of a light solvent, a heavy solvent and a non-solvent is dioxane-dimethylformamide-water.

When preparing the solution, it is preferable to keep the adjustment temperature below the following transition temperature, for example below aO'C6; if it exceeds 00C, the permeability of the membrane may drop significantly. The reason for this is thought to be that when the temperature exceeds 0°C, the α-wax transforms into a random coil or β structure depending on the type of amino acid and solvent. This is thought to be because, at -0°C or lower, the helices are plane-oriented due to the α-structure, and gas permeates through the spaces occupied by the side chains and polyurethane chains between the helices.

In the next step of removing light solvent, the proportion of light solvent removed affects the thickness of the dense layer. The smaller the proportion of light bathing particles that are removed, the thinner the dense layer is obtained. Specifically, IO- to 10 of the light solvent used depending on the evaporation time.
- is preferably removed, but less than 10% or 10%
-The above cases are also possible. Since the gas permeation rate through the membrane depends on the thickness of the dense layer, this step of removing the solvent is important in controlling the gas permeation rate through the membrane. In order to obtain a membrane with a high gas permeation rate, it is generally better to reduce the amount of light solvent removed and reduce the thickness of the dense layer of the membrane, but on the other hand, if the thickness of the dense layer is too thin, the dense layer may This is not preferable because it causes defects.

Therefore, it is desirable to control the amount of solvent removed to such an extent that such defects do not occur. However, with the membrane material of the present invention, the gas is dissolved into the membrane itself to a large extent;
Since there is no need to thin the dense layer to the point where defects occur, it has the advantage of being able to produce a stable film with good reproducibility.

The coagulating liquid serves the purpose of gelling the polymer solution or completing the formation of the gel by evaporation of the light solvent. Specifically, methanol, ethanol, water, a water-methanol mixture, etc. can be used as the coagulating liquid. The immersion time is not particularly limited, and may be any time sufficient to elute most of the solvent constituting the polymer solution.

Generally, at home temperature, about 7 minutes and 0 minutes is desirable.

The next step is the drying of the coagulated film, which can be carried out at a high ambient temperature of 111 degrees. The present liquid is thus removed and the separation membrane of the present invention is obtained.

On the other hand, a gas separation membrane consisting only of a dense layer can be manufactured, for example, by the following method.

That is, in the method for manufacturing an asymmetric membrane consisting of a dense layer and a porous layer described above, operations similar to those for manufacturing an asymmetric membrane may be performed, except that immersion in a coagulation liquid is omitted. In other words, a dense single-layer film can be obtained from the cast membrane material solution by evaporation and drying.

M of the present invention is a membrane with excellent gas selective permeability,
Furthermore, it has excellent mechanical strength and ease of handling that can be used practically, and can be used in many fields for the purpose of obtaining a larger proportion of a certain substance from a mixture.

Areas in which the membrane of the invention is useful are gas separations, for example in the separation of methane and helium in the recovery of helium from natural gas, in the enrichment of hydrogen from the waste gas of hydrogenation reactions. Separation of methane and argon, hydrogen and nitrogen, hydrogen and methane, separation of methane hexahydrogen and carbon monoxide and hydrogen in the coal silent process, concentration of air used in oxidation reactions,
These include oxygen concentration of air used for combustion, concentration of oxygen in air for medical purposes, and artificial lungs. Suitable for separating these gases from each other from gas mixtures containing 0. Other than gas separation, e.g. separation of liquid mixtures, seawater desalination, wastewater treatment, separation of hydrocarbons, separation of metal salts, separation of ions, It is suitable for separation of azeotropic mixtures, artificial organs, artificial skin, etc., and is suitable for selectively separating these substances from liquid mixtures containing organic liquids, ions, metal salts, dissolved gases, biological substances, etc.

Hereinafter, the present invention will be further explained based on Examples, Example K.
Fi limit is not added. In addition, in the following, rumors indicate weight -.

Example 1 r-Methyl-L-glutamic anhydride (10%) and urethane prepolymer (ton) (isophorone diisocyanate and polytetramethylene glycol (Mitsubishi Chemical Co., Ltd. product name - PTMG co□θ0), 1co10a-x/x)
was polymerized using diamine as a catalyst in a dichloroethane/dimethylformamide t:co mixed solvent, and Bl in a dimethylformamide/dioxane (7:j) mixed solvent at 27°C.
The measured value by the viscometer is /1411 cps (0,
JRPM) poly r-methyl-L-glutamic acid-polyurethane copolymer was obtained.

Next, the above polymer was mixed with dimethylformamide/dioxane (
7:j) Dissolved in a mixed solvent to make a homogeneous solution (solid content concentration/lIJ%, viscosity 2♂t 7 cpθ/co゛j℃, o
, JRPM). All solution preparations were performed at temperatures below μm°C.

This solution was cast onto a glass plate to form a film with a doctor knife to a thickness of 300 μm, and after being left in the air at room temperature for 30 seconds, the film was immersed together with the glass plate in a water bath at room temperature. After 3 minutes, the membrane was removed from the bath, air dried, and then vacuum dried.

The gas permeation rate through the poly-γ-methyl-L-glutamic acid-polyurethane copolymer film formed in this manner was measured. The gas permeation rate is measured using a membrane device (AM).
The membrane of the present invention was fixed on a 100N company J-type ultra-transient test device), and the film was tested. A specified gas is applied to one side of the membrane at °C.
A pressure was applied to the -/- gauge, and the amount of gas permeating out from the other surface of the membrane over a certain period of time was measured using a gas villet.

The results are shown in Table 7.

Example 1 Example/In! 11! In the membrane method, the same operation was performed except that the glass plate was air-dried without being immersed in a water bath, and then dried under reduced pressure. The results are shown in Table 1.

Example 3 r-Methyl-L-glutamic anhydride (jo-) and urethane prepolymer (jOlt) (/, G-hexamethylene diisocyanate and polytetramethylene glycol (
Mitsubishi Kasei product name-PTMGλ000), NOOlo
Using diamine as a catalyst, polymerize H 2 C) in a dichloroethane/dimethylformamide (t:co) mixed solvent, and dimethylformamide/dioxa y (7:J) at 2j°C.
The value measured by a B-type viscosity needle in a mixed solvent is l≠r hirorcp
s (0,! RPM) to obtain a polyphosphoric acid-polyurethane copolymer.

Next, the above polymer was mixed with dimethylformamide/dioxane (
7:3) It was dissolved in a mixed solvent to make a homogeneous solution (solid content once 10%), and all liquid preparations were carried out at below po°C.

This solution was spread on a glass plate, and a film was formed using a doctor knife to a thickness of 10 μm. Immediately after the film formation was completed, the film was immersed together with the glass plate in a water bath at room temperature. Perform the same operation as Iil.9. The results are shown in Table 1.

Comparative Example 1 r-Methyl-L-glutamic acid anhydride was polymerized in dichloroethane using an Azun catalyst, and the measured value with a B-type viscosity needle in λSC dichloroethane was /2000 cps (
0,! RPM) poly r-methyl-L-glutamic acid was obtained.

Next, the above polymer solution (solid content 1 on) was cast onto a glass plate, and a film with a thickness of -jQμ was formed using a doctor knife. Immediately after the film formation was completed, the film was placed together with the glass plate in a methanol bath at room temperature. immersed in.

Note that all operations were performed at room temperature.

Hereinafter, the same operations as in Example 1 were performed. The results are shown in Table/.

Comparative Example The same procedure as in Comparative Example/ was performed except that the glass plate was air-dried without being immersed in a methanol bath, and then dried under reduced pressure.

The gas permeability of the obtained membrane was so slow that no effective measurement could be made.Even after holding for 01 hours, the scale of the gas billet did not move visually.

EXAMPLE The membrane obtained in Example 1 was stacked on a commercially available porous membrane (Millipore filter - VEIWPJ (product manufactured by Nippon Millipore Limited)) support to form a composite membrane, and the gas permeation rate was measured. The results are shown in Table 2.

Comparative Example 3 In Example 1, Millipore filter as a support vs.
The same operations as in Example 1 were performed except that wPg was used. The results are shown in Table 2.

Claims (2)

[Claims] (1) A separation membrane mainly formed from a block copolymer in which polyurethane molecules are introduced into the molecular chains of polyamino acids, and used to separate specific components from a substance mixture. (2) Amino acid-N-carboxylic acid anhydride and a urethane prepolymer having an incyanate group at the end,
Separation membrane (3) according to claim 1, which is formed mainly from a block copolymer obtained by copolymerizing in the presence of amines; claim 1, which is used for gas separation; or Separation membrane according to item 2