JPH01310715A - Gas permselective membrane - Google Patents

Abstract

PURPOSE:To obtain a membrane with high heat resistance, solvent resistance and strength as well as high selectivity and permeation by using a reaction product of a specific aromatic polyester imide with polydimethylsiloxane modified with amino-group on one end terminal as a gas permselective membrane material. CONSTITUTION:A reaction product of a specific aromatic polyester imide having a repeated monomer unit expressed as a formula (I) with polydimethylsiloxane modified with amino-group on one end terminal having a repeated monomer unit expressed as formula (II) is used as a gas selective permeation membrane material, where (n)=1-7, (m)>=5, R stands for alkyl with number of carbon 2-6, and R' stands for alkylene with number of carbon 2-6. A membrane prepared from the composite polymer has excellent gas selectivity and permeability as well as high heat resistance, solvent resistance and strength.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a permselective membrane, and more particularly to a gas selective permselective membrane comprising a reaction product of polyetherimide and polydimethylsiloxane modified with an amino group at one end. .

[Conventional technology]

In recent years, active consideration has been given to separating and purifying gas mixtures using gas selectively permeable membranes. For example, attempts have been made to selectively permeate oxygen from air to obtain oxygen-enriched air for use in medical treatment or combustion systems. In addition, we selectively permeate, separate, and refine hydrogen from hydrogen obtained by steam reforming, thermal decomposition, etc. of coal, natural gas, oil sands, etc., and from synthetic gas containing carbon oxide, methane, etc. Attempts have also been made to produce basic chemicals such as methanol using this gas as a starting material.

Gas selectively permeable membranes used in these applications are required to have characteristics such as high gas selectivity and gas permeability, heat resistance, chemical resistance, and high strength.

Gas selectivity is a value expressed by the ratio of permeation rates between a specific gas and other gases, and a high gas selectivity means an excellent gas separation ability. Further, the gas permeability "b" means that the absolute amount of gas that permeates through the membrane is large, meaning that a large amount of gas can be processed.

For example, membranes made of polyetherimide (USF4.156,59
7) is known, and a membrane made of a silicone polymer such as polydimethylsiloxane is known as a membrane having a high gas permeation rate.

[Problem to be solved by the invention]

However, it is not possible to satisfy all of the above required properties with a single material of these polymers or copolymers; in other words, polymer materials with high gas selectivity have low permeability, and The problem with polymeric materials having excellent gas selectivity is that they have insufficient gas selectivity.

For example, the gas separation membrane made of polyetherimide described in US F 4.156.597 has a high gas selectivity, and the selectivity of oxygen to nitrogen is about 7 to 8 times, but its permeability coefficient ( Since the permeation rate (permeation rate per unit thickness) is extremely small, the range in which this membrane material alone can be used as a gas selectively permeable membrane is extremely limited.

In addition, polydimethylsiloxane has the highest gas permeability among polymer materials due to its siloxane bonds, but it has low gas selectivity, weak mechanical properties, and low compatibility with other polymers. It has some drawbacks.

In order to solve these problems, the present inventor developed two polymer materials: one with high gas selectivity and one with high gas permeability.
After studying component-based materials, we discovered a two-component gas permeable membrane with a large difference in gas selectivity and gas permeability, as well as excellent heat resistance, chemical resistance, and strength properties, and completed the present invention. Ta.

[Failure to solve the problem]

The gist of the present invention is a polyetherimide having a repeating unit represented by the following general formula % [where n is an integer of 1 to 7] and one end having a repeating unit represented by the following general formula. It is a gas selectively permeable membrane made of a reaction product with amino group-modified polydimethylsiloxane.

The polyetherimide represented by the above general formula is a polymer obtained by condensation polymerization of phenoxyphenyldicarboxylic anhydride and phenylenediamine, and the OnHfX group can have a linear structure or a branched structure.

As a representative example of the polymer, 2,2-bis[4-(54-
dicarboxyphenoxy)phenyl]7' o y<
It is obtained by a polycondensation reaction with anhydrous tometaphenylene diamine.

○ can be mentioned.

In these polyetherimides, the aromatic imide structure provides rigidity, the ether bond provides fluidity and processability, and overall they have excellent heat resistance, chemical resistance, and mechanical properties.

The polyetherimide used in the cage of the present invention may have the above structure, but preferably has a number average molecular weight in the range of 5,000 to 100,000 as measured by GPC.

The silicone-modified polyetherimide used in the present invention is produced by dissolving polyetherimide in an inert solvent, then adding polydimethylsiloxane modified with an amino group at one end (hereinafter referred to as "modified silicone"), mixing, and heating to form a polymer. You can get it by reacting. The structure of the reaction product is not particularly limited, but from the viewpoint of film-forming properties, it is preferable to have a structure in which polyetherimide is the main chain and modified silicon is bonded in a comb-like shape. The temperature of the mixed solution during the reaction may be approximately 60°C to 300°C, and is appropriately selected depending on the type of inert bath agent used.

Although the proportion of both components in the reaction product is not particularly limited, it is preferable that one component is in the range of 15 to 85% by weight. This is because if the ratio of one component is less than 15% by weight, it is difficult for that component to exhibit its useful properties. For example, if the proportion of polyetherimide is less than 15% by weight, high gas selectivity and excellent mechanical properties will not be fully expressed, and if the proportion of modified silicon is less than 15% by weight, high b gas The permeability is sufficiently developed.

More preferably, the proportion of both components is in the range of 6° to 70% by weight.

Next, the film forming method will be explained in detail.

The excellent gas selective permeability membrane of the present invention can be obtained by this method.

Film formation is usually carried out by applying, casting, etc. a polymer solution. Alternatively, a film may be formed on a suitable porous support by dipping, casting, or the like.

When using a porous support such as a tube or hollow fiber, the support is immersed in a polymer solution, pulled up, and blown to evaporate the solvent to form a membrane on the support. When using a film-like porous support, a method may be used in which a solution is thinly applied onto it and then the solvent is evaporated off. A method may also be used in which a membrane is bonded to a porous support. The method of forming a film on the liquid surface is one of the preferred methods because the solution can be spread extremely thinly and a thin film can be obtained.

In the present invention, modified silicon used as another copolymerization component imparts high gas permeability to the reaction product. It is sufficient if the molecular structure is as described above, and the molecular weight etc. are not particularly limited, but those having a number average molecular weight of 5[10 to 55,000 as measured by c) PC method are preferably used. As an example, silicone monoamine X-22-1717 manufactured by Shin-Etsu Chemical ■! One example is J-Z.

In addition, in the case of a reaction product with polyetherimide obtained by surrounding other silicon-based polymers, such as ordinary silicon-based polymers such as polydimethylsiloxane, a good balance between film formability and heat resistance is obtained. The problem is that it is strangely stiff and the gas selectivity of the separation membrane is poor.

〔Example〕

The present invention will be specifically explained below using Examples.

Example 1 - Polyetherimide 85? (General Electric Co., Ltd., Ultem 1ooo) was weighed into a 5-foot three-necked flask equipped with a stirrer, and 400 grams of chloroform was added thereto and stirred to dissolve the polymer. Then, in a 100-ml beaker, 50ml of chloroform and silicone monoamine 159 (manufactured by 4WM Chemical Company, X-22-171AE) were added.
+) and stirred at 50°C for 12 hours. After the reaction, the polymer solution was dropped into a beaker containing Methanol A/21, and the reaction product (composite polymer) was collected.

Similarly, composite polymers were obtained by varying the addition ratios of polyetherimide and silicone monoamine.

For comparison, composite polymers of unmodified polydimethylsiloxane systems were produced in the same manner, and the heat resistance and mechanical properties of these composite polymers were measured and are shown in Table 1.

Table 1 (Note 1) This is (unmodified) polydimethylsiloxane α with a molecular weight of 5000.

Next, the composite polymer thus obtained was dissolved in dichloromethane to prepare an 8% solution by weight, and the solution was coated on a clean glass plate to a thickness of about 100 μm, and the solution was applied at room temperature (20 to 30% by weight).
The solvent was evaporated at 0°C. Air was permeated through the obtained membrane to determine the oxygen permeability coefficient and oxygen/nitrogen selectivity of the membrane, and the results are summarized in FIG. It can be seen that as the ratio of polyetherimide in the composite polymer increases, the selectivity increases greatly, but it rises particularly sharply when the ratio exceeds 15.

〔Effect of the invention〕

The gas selectively permeable membrane of the present invention is composed of polyetherimide with high gas selectivity and a modified polydimethylsiloxane composite with excellent gas permeability, so it has excellent gas selective permeability, heat resistance, solvent resistance, and high gas permeability. Has strength.

[Brief explanation of the drawing]

Figure 1 shows the oxygen permeability coefficient and oxygen/nitrogen selectivity of various gas selectively permeable membranes with different polyetherimide contents obtained in Example 1.
0q. Boliether imi YΦ upper law (ma amount%)

Claims (1)

[Claims] Polyetherimide having a repeating unit represented by the following general formula ▲ Numerical formula, chemical formula, table, etc. ▼ [However, n represents an integer of 1 to 7] and the following general formula ▲ Numerical formula , chemical formulas, tables, etc. ▼ [However, R is an alkyl group having 2 to 6 carbon atoms R' is a methylene group having 2 to 6 carbon atoms n is an integer of 5 or more] A gas selectively permeable membrane made of a reaction product with amino group-modified polydimethylsiloxane.