JPH03296425A - Silicon-modified polyether imide and selectivity gas-permeable membrane - Google Patents

Abstract

PURPOSE:To obtain the membrane having an excellent character of selective gas permeability by a method wherein the membrane consists mainly of silicon- modified polyether imide, the product of reaction between a specific polyether imide and a specific modified polydimethylsiloxane. CONSTITUTION:The subject membrane consists mainly of the silicon-modified polyether imide produced by reaction between the polyether imide having the repeating unit represented by the general formula I (wherein n is an integer of 1-7) and the modified polydimethylsiloxane having the repeating units of dimethylsiloxane represented by the general formula II (wherein R is 1-6C alkylene group, m is an integer not less than 5, l is an integer not less than 1 and the number of primary amino group is one per one polymer molecule) and the primary amino group in the side chain. This reaction product is dissolved in chlorine solvents such as dichloromethane and chloroform to form the membrane. This selectively gas-permeable membrane has an excellent selective gas permeability and heat resistance, solvent resistance and a high strength.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gas selectively permeable membrane used for separation and purification of gas mixtures, and also relates to compounds suitable for gas selectively permeable membranes.

[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. Also, coal,
Attempts have also been made to produce basic chemicals such as methanol using hydrogen as a starting material from synthetic sludge containing hydrogen, carbon oxide, methane, etc. obtained by steam reforming or thermal decomposition of natural gas, oil sands, etc. being done.

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 expressed as the ratio of permeation rates between a specific gas and other gases, and a high gas selectivity means excellent gas separation ability.

Furthermore, the term "high gas permeability" 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, a membrane made of polyetherimide with excellent oxygen permeation selectivity in air (U.S. Pat. No. 4,156,5
No. 97) is known, and membranes made of silicone polymers such as polydimethylsiloxane are also known as membranes with a high gas permeation rate.

(Problem to be solved by the invention) However, it is not possible to satisfy all of the above required characteristics with a single conventional polymer or copolymer material.In other words, a polymer material with high gas selectivity cannot Another problem is that polymeric materials with excellent gas permeability have insufficient gas selectivity.

For example, the gas selectivity of the gas separation membrane made of polyetherimide described in U.S. Pat. (Transmission rate per unit thickness)
Since this membrane material 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 drawbacks.

The present invention has been made to solve these problems, and is directed to a material that has both high gas selectivity and gas permeability, and has excellent heat resistance, chemical resistance, and strength properties, and a material made from the material. The purpose is to provide a gas-permeable membrane with the following properties.

(Means for Solving Section 4) The present invention provides a polyetherimide having an edge-reversing unit represented by -Math.■ (where n is an integer from 1 to 7) and -Math.H2 (However, , R is an alkylene group having 1 to 6 carbon atoms, m is an integer of 5 or more, and 1 is an integer of 1 or more.The number of amino groups is one per polymer molecule. These are silicone-modified polyetherimide, which is a reaction product of a modified polydimethylsiloxane having repeating units and a primary amino group in its side chain, and a gas-selective permeable membrane containing the silicone-modified polyetherimide as a main component.

[For production]

The polyetherimide used in the present invention has a structural unit represented by formula 1, and is preferably a polymer consisting essentially of structural units represented by formula (2). Such polyetherimide is a polymer obtained by condensation polymerization of phenoxyphenyldicarboxylic anhydride and phenylenecyamine, and the CnH2 group can have a linear structure or a branched structure.

A typical example of the polymer is 2,2-bis(4-(3,4
Examples include those obtained by a polycondensation reaction of dicarboxyphenoxyphenyl]propane anhydride and metaphenylenediamine.

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 present invention is GPC
The number average molecular weight in the method is preferably within the range of 5,000 to 100,000.

The silicone-modified polyetherimide of the present invention is produced by dissolving polyetherimide in an inert solvent, then adding modified polydimethylsiloxane having a primary amino group in the side chain (hereinafter referred to as "modified silicone"), mixing, and heating to produce both polymers. It can be obtained 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 silicone is bonded in a comb blade shape. The temperature of the mixed solution during the reaction may be approximately 30 to 300°C, and is appropriately selected depending on the type of inert solvent used.

Although the proportion of the same 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 silicone is less than 15% by weight, high gas permeability will occur. tends not to be fully expressed. More preferably, the proportion of the same component is in the range of 30 to 70% by weight.

Next, the film forming method will be explained.

The excellent gas selective permeability membrane of the present invention can be obtained by dissolving the reaction product in a chlorinated solvent such as dichloromethane or chloroform and forming a membrane.

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 a porous support such as a tube or hollow fiber is used, the support is immersed in a polymer solution, pulled up, and then the solvent is evaporated to form a membrane on the support. When using a film-like porous support, a method may be employed in which a solution is thinly applied onto the support and then the solvent is removed by evaporation. 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, the modified silicone imparts high gas permeability to the reaction product. The molecular structure may be as described above, and the molecular weight etc. are not particularly limited, but those having a number average molecular weight in the range of 500 to 35,000 by GPC method are preferably used. As an example, silicone monoamine manufactured by Shin-Etsu Chemical Co., Ltd. can be cited.

In addition, in the case of reaction products with polyetherimide obtained by using other silicone-based polymers, for example, ordinary silicone-based polymers such as polydimethylsiloxane, the film-forming properties and gas selectivity of the separation membrane are inferior. becomes a problem.

〔Example〕

The present invention will be specifically explained below using Examples.

Example 1 70 g of polyetherimide (manufactured by General Electric Company, Ultem 1000) was weighed into a 1 liter three-necked flask equipped with a stirrer, and 500 mI of chloroform was added to the flask.
L was added and stirred to dissolve the polymer. Next, silicone monoamine (manufactured by Shin-Etsu Chemical Co., Ltd., X-22-098) 3
0 g was added and left at 50°C for 72 hours. After the reaction, the polymer solution was dropped into a beaker containing 2 liters of methanol, and the reaction product (binary polymer) was collected.

In addition, the above-mentioned polyetherimide has H3 (:, H2n- replaced with -C- in Formula 1) and has a molecular weight Mn=2
2000, H3 Also, in the above silicone monoamine, R is C1 in the formula (■).
12(:H2CH2, molecule JiMn=650
It is 0.

Similarly, composite polymers were obtained by varying the addition ratios of the 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.

(Leaving space below) Table *: Unmodified polydimethylsiloxane with a molecular weight of 5000 Next, composite polymers obtained by varying the proportions of the polyetherimide and silicone amine in Examples 1 to 5 and in the same manner as in Examples 1 to 5 were each mixed with dichloromethane. An 8% by weight solution was prepared by dissolving the solution and coating it on a clean glass plate to a thickness of about 100 microns, and the solvent was evaporated in room 1 (20-30°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 the selectivity increases as the proportion of the polyetherimide in the composite polymer increases, but it increases rapidly especially when it exceeds 15%.

〔Effect of the invention〕

The silicone-modified polyetherimide of the present invention has excellent heat resistance, solvent resistance, and high strength, and is a composite of polyetherimide with high gas selectivity and modified polydimethylsiloxane with excellent gas permeability. This provides a permselective membrane with excellent gas permselectivity, heat resistance, solvent resistance, and high strength.

[Brief explanation of drawings]

Figure 1 shows the oxygen permeability coefficients and oxygen/permeability of various gas selectively permeable membranes with different polyetherimide contents obtained in Examples.
It is a figure showing selectivity of nitrogen. Figure 1

Claims (1)

[Claims] 1. Polyetherimide having a repeating unit represented by the general formula ▲ Numerical formula, chemical formula, table, etc. (where n is an integer from 1 to 7) and the general formula ▲ Numerical formula, chemical formula, table, etc. etc.▼ (However, R is an alkylene group having 1 to 6 carbon atoms, and m
is an integer of 5 or more, l is an integer of 1 or more). 2. A permselective membrane comprising the silicone-modified polyetherimide according to claim 1.