JPH0331494B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas permeable membrane that can selectively transmit oxygen gas.

Currently, the most common industrial technology for separating oxygen or nitrogen from air is the cryogenic separation method, but recently a method for separating oxygen by an adsorption method using zeolite or the like has also been industrialized. These methods are advantageous for obtaining relatively high-purity oxygen or nitrogen in large-scale production volumes, but as small-scale oxygen generators, the equipment costs and energy costs are high, and the equipment is too expensive for the amount generated. There are also disadvantages such as the need for a large size. As a method for separating oxygen with less energy, it is ideal to use a polymer membrane that allows oxygen to pass through but not nitrogen.

However, existing polymer membranes generally have a low ratio of oxygen to nitrogen permeability coefficients, that is, a separation coefficient, or an oxygen permeability coefficient that is too small to be of practical use. In addition, even if the membrane has satisfactory oxygen permeability coefficient and separation coefficient, the elastic modulus of the membrane is too small, the membrane surface tends to block easily, and furthermore, it may be mechanically damaged due to the plasticization phenomenon due to moisture absorption. In some cases, membranes have poor strength and shape stability, and are difficult to handle, requiring further improvements before they can be put to practical use.

For example, a silicone rubber-based permeable membrane is 1×10 ^-8 ~
It shows a large oxygen permeability coefficient of 1×10 ^-9 cm ³ cm/cm ² sec cmHg, but the oxygen/nitrogen separation coefficient is 2 to 2.5.
Because of its small size, only one pass through the membrane removes air from the air.
Only about 30% oxygen-enriched air can be obtained, and in addition, thin membranes are prone to blocking and are difficult to handle, and due to mechanical strength constraints, increasing the membrane area requires larger equipment or membrane costs. There are disadvantages such as large size.

In addition, polyethylene terephthalate can be easily formed into hollow fibers and membranes, and has a high separation coefficient of 5.2, which means that it separates approximately 50% from air in one membrane permeation.
Concentrated air containing 100% of oxygen can be obtained, but the oxygen permeability coefficient is small at 2.8×10 ^-12 cm ³ cm/cm ² sec cmHg.
In order to obtain the same amount of permeation as a silicone rubber membrane,
Its permeation area is approximately
It is not very practical as it requires 1000 times the magnification. As described above, the permeability and separability of a membrane material generally have a tendency to cancel each other out, and a membrane material with a large oxygen permeability coefficient tends to have a small oxygen/nitrogen separation coefficient.

The present inventors found that a polymer having tertiary amino groups in the polymer side chain as an oxygen-selective permeable membrane has a large oxygen/nitrogen separation coefficient and oxygen permeability coefficient due to the interaction between oxygen molecules and tertiary amines. (Patent Application No. 129876, Showa 52). However, this polymer has poor shape stability due to the plasticizing effect due to moisture absorption, and furthermore, when formed into a thin film, the film blocks, making it difficult to handle.

The purpose of the present invention is to create not only a homogeneous membrane but also an asymmetric membrane having a homogeneous skin layer and a porous layer, which has a practical oxygen permeability coefficient and separation coefficient, and which is soluble in commonly used organic solvents. Shape stability that allows for film formation,
The object of the present invention is to provide an oxygen gas selective permeable polymer membrane with high membrane strength and good membrane formability.

As a result of repeated research to develop a membrane material with these functions and properties, the inventors of the present invention found that it has good membrane properties and is soluble in organic solvents, so it can be molded into hollow fibers with a highly permeable asymmetric structure. We succeeded in obtaining a practical membrane material by blending or copolymerizing available cellulose-based polymers with polymers containing tertiary amino groups in their side chains.

That is, the present invention has (1) a cellulose-based polymer (A polymer) soluble in an organic solvent and a tertiary polymer in the polymer side chain.
This is an oxygen gas selective permeable membrane made of a copolymer (C polymer) formed by copolymerizing a polymer having a class amino group (B polymer).

The oxygen gas selective permeable membrane of the present invention is a copolymer of a cellulose polymer soluble in organic solvents and a polymer containing a tertiary amino group in the side chain, so it has a large oxygen permeability coefficient and /Nitrogen separation coefficient is larger than that of conventional existing polymers, and is soluble in dimethylformamide, acetone, halogenated hydrocarbons, or mixed solvents thereof, and can be formed into an asymmetric membrane having a skin layer. It can also be formed into hollow fibers to increase the membrane area. In addition, shape stability, membrane strength,
It has excellent film forming properties and does not cause blocking development between films.

The cellulose polymer (A polymer) referred to in the present invention is nitrocellulose, diacetylcellulose, triacetylcellulose, cellulose acetate butyrate, cellulose propionate, ethylcellulose, hydroxyethylcellulose,
A general term for carboxypropyl cellulose, mixtures thereof, or mixtures thereof with small amounts of other polymers that do not significantly impair their oxygen gas permeability, film forming properties, and film properties.
Commonly used additives such as pigments, stabilizers, molding agents, etc. can be added to the A polymer to the extent that they do not significantly impair the desired membrane function. As mentioned above, the typical oxygen permeability coefficient of A polymer is 1×
10 ^-11 cc・cm/cm ²・sec・cmHg~1×10 ^-9 cc・
cm/cm ² seccmHg.

In the present invention, a polymer having a tertiary amino group in the side chain (polymer B) is a polymer having a tertiary amino group in the side chain, such as a dimethylamino group, a diethylamino group, a di-i-propylamino group, a di-n - A polymer having a propylamino group, a di-n-butylamino group, a pyridyl group, a dimethylaminophenyl group, a diethylaminophenyl group, etc., and specifically, poly-N,N-diethylaminoethyl acrylate, poly-4 Examples include vinyl polymers having a tertiary amino group in the side chain, such as -vinylpyridine, poly-2-vinylpyridine, and poly-p-(N,N-dimethylaminostyrene). This vinyl polymer may contain other vinyl monomers in addition to the monomer having a tertiary amino group in its side chain. Also, glycols having a tertiary amino group in the side chain, such as 2-methyl-2-N,N-dimethylaminomethyl-1,3-propanediol,
2-Methyl-2-N,N-diethylaminomethyl-1,3-propanediol, 2-methyl-2-
N,N-di-n-propylaminomethyl-1,3
-propanediol, 2-methyl-2-N,N-
Di-i-butylaminomethyl-1,3-propanediol, 2-methyl-2-N,N-dibenzylaminomethyl-1,3-propanediol, 2,
2-bis(N,N-dimethylaminomethyl)-1,
Polyethers made from 3-propanediol, 2-ethyl-2-piperidinylmethyl-1,3-propanediol, etc., glycols having a tertiary amino group in their side chains, or diethers of these glycols, Polyethers, such as diethers of 2-methyl-2-N,N-dimethylaminomethyl-1,3-propanediol, 2
-Methyl-2-N,N-dimethylaminomethyl-
Polyurethane, polyether urethane made from polyether of 1,3-propanediol, etc.
Examples include polyester, polyether ester, polyester urethane and mixtures thereof.

As a method for producing polymer B of the present invention, for example, a vinyl polymer is obtained by polymerizing N,N-diethylaminoethyl acrylate 4-vinylpyridine, 2-vinylpyridine, etc. in benzene using azobisisobutylnitrile as a polymerization initiator. be able to.

Further, glycol containing a tertiary amino group in its side chain can be kept under reduced pressure at 200 to 230°C in the presence of an acid catalyst to undergo dehydration condensation to form a polyether.

Furthermore, polyurethane and/or polyether urethane can be obtained by reacting the glycol or its polyether having a tertiary amino group in its side chain with a diisocyanate. Examples of diisocyanates include tetramethylene diisocyanate, hexamethylene diisocyanate, m-xylylene diisocyanate, 1,4-phenylene diisocyanate, diphenylmethane-4,4'-diisocyanate, and the like. Polymerization is carried out by a melt method or a solution method, with ice cooling or heating as necessary. Suitable solvents include dimethylformamide, dimethylacetamide, dimethyl sulfoxide, acetone, methyl ethyl ethyl ketone, N-methylpyrrolidone, and halogenated hydrocarbons such as methylene chloride and trichloroethylene. May be used. Further, in order to quickly complete the polymerization reaction, a heavy metal catalyst such as dibutyltin dilaurate is suitable.

The obtained polyurethane and/or polyether urethane may be treated with ethylene diamine,
Chain stretching is performed using a diamine such as m-xylylene diamine or 1,4-butylene diamine in a conventional manner,
The molecular weight of the polymer can be increased.

Furthermore, the above-mentioned tertiary amino group-containing glycol can be reacted with dicarboxylic acids to form a polyester. For example, dimethyl terephthalate and the above-mentioned glycol can be transesterified by a conventional method and then subjected to melt polycondensation. Polyester can also be obtained by direct dehydration polycondensation of terephthalic acid and the above glycol. The polyester thus obtained can be further reacted with a chain extender such as a diisocyanate or a carbonate ester to form a high molecular weight polymer, if necessary.

In the production of the above polymer, the tertiary amino group-containing glycol may be used alone or together with other glycols. Furthermore, these tertiary amino group-containing glycols and one or more other glycols may be copolymerized and used. Glycols other than tertiary amino group-containing glycols include ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, dibromneopentyl glycol, diethylene glycol, and dipropylene. Examples include glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like.

Further, it is desirable to copolymerize the A polymer and the B polymer in order to further improve the affinity and increase the mechanical strength compared to a simple blend. For example, polymer A and the above-mentioned tertiary amino group-containing glycol are dissolved in a common solvent or a mixed common solvent as the case may be, and as in the production method for polymer B, if necessary, in the presence of a catalyst, at room temperature or while heating, By adding a diisocyanate, an A polymer/urethane copolymer (C polymer) bonded to the hydroxyl group in the A polymer can be obtained. Cellulose polymer soluble in organic solvents (A polymer)
As mentioned above, a copolymer (C polymer) obtained by copolymerizing a polymer with a tertiary amino group in the side chain (B polymer) has a tertiary amino group in the side chain, which is the raw material of the B polymer. In addition to the method of copolymerizing vinyl monomers, glycols, diethers, polyethers, etc. having
It may be a copolymer obtained by a method of copolymerizing with a polymer. Next, a film can be formed directly from this polymerization solution in the same manner as in the blend system.
It is possible.

In order to increase the membrane area, these membranes can be formed not only into flat membranes but also into hollow fibers from a polymer solution.

The copolymerization ratio of polymer A and polymer B is A polymer/B polymer weight ratio of 95/5 to 10/90 from the viewpoint of oxygen gas permeation and separation performance and membrane properties, and preferably a weight ratio of 80 A ratio of /20 to 30/70 is preferred.

If the weight ratio of the A polymer is larger than this, the properties of the A polymer itself cannot be improved, and even if the membrane shape is good, satisfactory permeability and separation properties cannot be obtained. If the weight ratio of the B polymer is larger than this, the film shape will be poor, the strength will be low, and depending on the B polymer composition, blocking will occur, and if the B polymer has a small molecular weight,
This is undesirable as it may cause migration etc.

Applications of the oxygen enrichment generator using the oxygen-selective permeable membrane obtained in this way include aeration for sewage treatment, fermentation industry, boilers that require high combustion temperatures, incinerators, and medical oxygen. Examples include inhalation devices and aeration for fish ponds. Furthermore, the air impermeable through the membrane has a high nitrogen content and can be used as an insoluble gas to cover spaces such as fuel tanks.

Examples will be given below to more specifically illustrate the present invention. In the examples, parts simply indicate parts by weight.

In addition, in the present invention, gas permeability was measured using a gas permeability measuring device GTR-30 manufactured by Yanagimoto Seisakusho.
Permeate gas was determined by gas chromatographic detection at 25°C.

The separation coefficient was expressed as the ratio of the oxygen gas permeability coefficient to the nitrogen gas permeability coefficient.

Example 1 2-methyl-2-(N,N-dimethylamino)
44 parts of methyl-1,3-propanediol and 1 part of phosphorous acid were kept at 220 to 230°C at normal pressure in a nitrogen stream.
After distilling off water, polycondensation was further carried out at 230° C. under a reduced pressure of 25 mmHg for 6 hours while distilling off water to obtain a polyether with a number average molecular weight of 2970.

2 g of the obtained polymer, triacetyl cellulose LT-105 (manufactured by Daicel, degree of acetylation 60.5%,
Degree of substitution 2.8) 2g was dissolved in 40ml of methylene chloride to make a dope, and 3.5ml of a 10% methylene chloride solution of diphenylmethane diisocyanate was added dropwise to the resulting dope consisting of polyether, triacetylcellulose and methylene chloride at room temperature. ,moreover
After stirring for 30 minutes, a slightly milky white copolymer solution consisting of polyurethane containing polyether and triacetyl cellulose as alcohol components was obtained. Casting was performed in the same manner as in Example 1 to obtain a substantially transparent film with a thickness of 28.9 μm.

The oxygen gas permeability coefficient of this flat membrane is 4.1×10 ^-9 cm ³・
cm/cm ²・sec・cmHg, nitrogen gas permeability coefficient is 0.96
×10 ^-9 cm ³・cm/cm ²・sec・cmHg and the separation factor is 5.5
It was hot.

Comparative example Triacetylcellulose (Dial LT-105)
The oxygen permeability coefficient of the membrane obtained by casting in the same manner as in Example 1 was 8.4×10 ^-11 cm ³ cm/cm ²
sec・cmHg, nitrogen permeability coefficient 1.5×10 ^-11 cm ³・cm/
^cm2・sec・cmHg, the separation factor is 5.6,
It was remarkable that the permeable membrane of the present invention had high oxygen permeability without reducing the separation coefficient.

Claims (1)

[Claims] 1 Cellulose polymer soluble in organic solvents (A
An oxygen gas selective permeable membrane made of a copolymer (C polymer) formed by copolymerizing a polymer (B polymer) and a polymer (B polymer) having a tertiary amino group in the polymer side chain.