JPS59203603A - Selective gas permeable membrane - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a selective gas permeable blend membrane having good gas separation properties and excellent gas permeability.

Structure of conventional examples and their problems Recently, separation technology using membranes has made remarkable progress, and has already been put to practical use on an industrial scale in several fields, such as seawater desalination and factory wastewater treatment.

On the other hand, separation of mixed gases using organic polymer membranes has problems such as the low selectivity of the membrane, making it difficult to selectively obtain high-purity gases, and the inability to produce large amounts of gas due to the small amount of permeation. For this reason, there are few practical examples of gas separation using membranes.

However, there are many fields where high purity gas is not necessarily required for the end use of gas. For example, in the case of oxygen, high purity oxygen is not required for combustion, medical breathing, etc. On the contrary, when high-purity oxygen is used for combustion, the combustion temperature varies too much, causing damage to the furnace and the risk of fire. Furthermore, even in the case of medical use, high purity oxygen often causes disadvantages such as blindness in premature infants. Therefore, in such fields, gas separation methods using membranes are advantageous. In the separation of oxygen from air using membranes, it is difficult to obtain air with high purity oxygen in one stage of separation, but it is difficult to obtain air with high purity oxygen in one stage of separation. Enriched air is relatively easy to obtain. In other words, the membrane separation method can directly produce oxygen-enriched air with an oxygen concentration of about 25% to 60% from air, and there is no need to handle mixers or cylinders, making it easy to operate and economical. This is an advantageous method. However, as there are already some differences in literature and patent publications regarding mixed gas separation using polymer membranes, in this case, there are differences in the permeability coefficient of the polymer membrane for gas and the thin film. The mechanical strength and film thinning technology are important issues.

Among the currently reported polymer materials, natural rubber, synthetic rubber such as polybutadiene, polyolefin, and silicone rubber are known to have excellent gas permeability. Silicone rubber outperforms any other polymeric material against almost all gases. However, the separation ratio of each gas becomes small, and when used to enrich air with oxygen, only air enriched with oxygen at a low concentration of about 23% to 30% can be obtained. Therefore, in order to obtain oxygen-enriched air of 30% or more, a material with a higher separation ratio is required. One of them is JP-A-66-
There is a gas separation membrane mainly composed of polyolefin or diene polymer, which is disclosed in Japanese Patent No. 92925. One of the materials shown in this publication, poly-4-methylpentene = 1, has an oxygen permeability coefficient of approximately 2.5 x 10
At cc-α/(24"S@C' CmHq, it decreases to less than one-tenth of that of silicone rubber, but the separation coefficient between oxygen and nitrogen increases to about 4.0. Also, US Pat. No. 33
Polyphenylene oxide (hereinafter referred to as PPO) shown in the specification of No. 50844 also has comparable performance. Therefore, when these materials are used for oxygen enrichment, air enriched with about 40% oxygen can be easily obtained. However, because the permeability coefficient is small, if the film thickness is the same as silicone rubber, the permeation flow rate will be less than 1/1Q.When using such a material, the film thickness must be increased to increase the permeation flow rate. Making it thinner is an important issue.

Several proposals have already been made for this purpose. However, poly-4-methylpentene-1 has poor solubility in organic solvents and extremely poor film-forming properties. On the other hand pp
It was found that in the case of o, the solubility was good and the film formability was also good. However, film formation using PPO alone is difficult due to its poor affinity with the support, so the present inventors
By forming the sandwich-type composite membrane shown in the specification of No. 07231, it was possible to obtain certain characteristics. Figure 1 shows the result and the permeation flow rate is 2.2 x 10CC/5eC-c
7+i-atm, and the oxygen/nitrogen separation ratio d was 3.0. The permeation flow rate shown here can be used in a small-scale device, but if the oxygen production cost is to be further reduced or the scale is increased, the device will become larger and the membrane properties will need to be further improved.

As mentioned above, polymers with better separability than silicone rubber or silicone copolymers generally also have lower gas permeability coefficients. Therefore, when trying to increase the gas permeation flow rate, thinning the film becomes even more important than in the case of silicone rubber or silicone copolymer. In the case of silicone rubber, fillers must be added or vulcanization treatment must be performed to form a solid film, and it is said that the limit for obtaining a homogeneous film is about 10 μm. On the other hand, in the case of a silicone copolymer, it is possible to achieve a thickness of about 0.1 μm since it does not require the same treatment as silicone rubber.

In order to obtain a gas permeation flow rate corresponding to the latter silicone copolymer using a polymer with high gas separation properties, such as poly-4-methylpentene-1, polyphenylene oxide, etc., it is necessary to make an ultra-thin film of approximately 0.01 μm. It's coming. It is technically very difficult to produce such an ultra-thin and homogeneous polymer film.

Purpose of the Invention The present invention has been made in view of the above points, and aims to obtain a selective gas permeable membrane that has high gas separation properties, a large permeation flow rate, and excellent film formation properties. be.

Structure of the Invention The present invention is a selective gas permeable membrane mainly comprising a blend membrane made of a material obtained by blending a feed type polymer containing a phenyl group in its main chain and a crosslinked silicone copolymer.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail.The present inventors used polyurecne, polysulfone, and polycarbonate, which are polymers with good gas separation properties.

When a clamp-type polymer containing a phenyl group in the main chain, such as polyester, is blended with a certain type of silicone copolymer,
It has been found that a composite membrane with extremely excellent permeability and high selectivity can be obtained. The feed type polymer containing a phenyl group in the main chain used here has a general formula selected from the alcohol residues shown above. ) In the polyurethane represented by the general formula, OR is a hydrogen atom, a hydrogen atom, or an alkyl group.

They are selected from halogenated alkyl groups and may be the same or different. ), polycarbonate whose general formula is 1 +-0-Z-0-C-0±U (where Z is the same as above), or polycarbonate whose general formula is 0 0 +o-c-z-c-o- ) n (where Z is the same as above), and examples of the silicone copolymer include JP-A-56-24019 and JP-A-56-2650 by the present inventors.
Publication number 6! A crosslinked silicone copolymer having a structure containing a polyorganosiloxane chain or a phenol nucleus as shown in Vf Publication No. 56-28605 and Japanese Patent Application Nos. 112466 to 112460 is used. In general, two types of silicone copolymers are used. When blending polymers, those with similar structures or properties have good compatibility, but other polymers usually have very poor compatibility. However, despite having different molecular structures and different properties, the 2-2 Silicov copolymer and condensed polymers with phenyl groups in the main chain are highly compatible.
They are compatible when the silicone copolymer content is about 40%.

A blend film of these polymers was formed on a uniform glass plate by a casting method, and its gas permeation properties were measured by a low vacuum method. As a result, the blend membrane prepared in this manner has an increased content of silicone copolymer. However, on the contrary, the separation coefficient between oxygen and nitrogen decreases, and at a silicone content of 30%, it is approximately α:2.
．． It decreases at 5 i. However, surprisingly, a film was formed on the water surface (Langmuir method) using the method shown in JP-A No. 66-26506 using a blend solution of the same composition.
When it was composited with a support and its properties were measured, it was found that the gas separation property showed a remarkable increase with an α value of 3.4. This is presumed to be because the film structure differs significantly between the casting method and the Langmuir method due to the difference in solvent evaporation rate during film formation.

In addition, the film forming properties at this time were very good, and the effective film thickness was approximately 500 mm.
A specific example of the present invention will be described in more detail below.

<Example 1> Polysulfone (MW=42,000) whose structural formula of the mesh type polymer (A) is H5Ll (MW=42,000) 0.5
Silicone copolymer 0-2 q 'c t- which is obtained by reaction-polymerizing αW-2 functional polysiloxane with a mixture of a phenolic resin having an aromatic ring in the main chain and a terminally functional polymer.
Luene was dissolved at 40 m°C, and a blend film of 180 μm was prepared on a uniform glass plate by a casting method. This gas permeation characteristic was measured using a low vacuum method.
ii Po2-3.5 x 109cc-cm/c
7i-sec-c7nHg, the separation coefficient α between oxygen and fish nest was 2.7.

<Example 2> A film was formed by the Langmuir method using a solution having the same composition as in Example 1, and Duragard 2400 (manufactured by Polyplastics) was used as a support. When forming a composite between the support and the blend membrane, due to poor adhesion between the blend membrane and the support, in order to prevent pinholes in the blend membrane, as shown in Figure 2, there is a gap between the blend membrane 1 and the support. Silicone copolymer layers 2 and 4 were provided on the support 3 and the blend membrane 1 to form a composite of the support 3 and the blend membrane 1. At that time, the gas separation characteristics were significantly improved, and the oxygen to nitrogen permeation flow rate ratio was α-3.54. In addition, the oxygen permeation flow rate (d4-12 x 10
It showed high permeability of cc/5eCcyA + atzn.

<Example 3> Polyurethane H whose structural formula is shown below □ -0 3 examples) 2 +5 (yw=25.ooo) o, eq and repeating unit R8
A silicone copolymer of polyorganosiloxane obtained by polymerizing a trifunctional organosiloxane of 10 p2 was dissolved in 5 o rJ2 of toluene, and a blend film of 200 μm was prepared on a uniform glass plate by a casting method. As a result of measuring this gas permeation property using a low vacuum method, the oxygen permeability coefficient PO27 was 7.32 x 10 CC.
"tyn/CIA" seC-CmHg,
Oxygen and nitrogen component*li coefficient α=2.75.

<Example 4> A composite membrane was obtained in the same manner as in Example 2 using the solution of Example 3. As a result, the oxygen permeation flow rate was 5.7 CC/5e.
With C-c7A・atm, the separation property is the permeation flow rate ratio of oxygen and nitrogen: d-=-3°10, and as in Example 2, the composite membrane has better separation performance and exhibits high gas permeability /ζ0 Examples 1 and 2 showed the properties of polysulfone, and Examples 3 and 4 showed the properties of a blend film of polyurethane and silicone copolymer, but other condensation polymers containing phenyl groups in the main chain, such as polycarbonate and polyester Similar characteristics can be obtained for .

Effects of the Invention As described above, the present invention is a selective gas permeable membrane mainly composed of a blend membrane obtained by blending a condensed cylindrical molecule containing a phenyl group in its main chain and a crosslinked silicone copolymer.
It is possible to obtain an excellent selective gas permeability film in which the gas permeation flow rate and the separation coefficient between oxygen and nitrogen are both large and the film formation rate is 4q3.

[Brief explanation of drawings]

Figure 1 shows the gas permeability of the composite membrane of PPO and silicone copolymer according to the inventors' earlier application! The characteristic diagram, FIG. 2, is a sectional view showing the cross-sectional structure of the selective gas permeable membrane according to the present invention. 2.4-Silicone copolymer, 3...Support.

Claims (6)

[Claims] (1) A selective gas permeable membrane mainly consisting of a blend membrane obtained by blending a condensation polymer containing a phenyl group in its main chain and a crosslinked silicone copolymer. (2) The condensation type polymer has the general formula %) Y is selected from alcohol residues having a valence of 2 or more. ) The selective gas permeable membrane according to claim 1, which is a polyurethane represented by: (3) The condensation polymer is selected from the group with the general formula (%). R is an alkyl group or a hydrogen atom. p is selected from a halogen atom and a halogenated alkyl group, and R may be the same or different. ) The selective gas permeable membrane according to claim 1, which is a polycarbonate represented by: (4) A condensation type polymer is selected from the general formula. Here, R is selected from a hydrogen atom, a halogen atom, an alkyl group, and a halogenated alkyl group, and R may be the same or different. ) The selective gas permeable membrane according to claim 1, which is a polysulfone represented by: (5) The selective gas permeable membrane 0 according to claim 1, wherein the crosslinked silicone copolymer contains a polyorganosiloxane chain or a phenol nucleus. (6) Selective gas permeable membrane 0 according to claim 1, which is produced by spreading the blend membrane on the water surface (7) Multilayer in which the blend membrane is sandwiched between silicone copolymers: The membrane is placed on a support. A selective gas permeable membrane formed according to claim 1.