JPH0242531B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a separation membrane having excellent chemical resistance, particularly durability against organic liquids. In detail, mainly general formulas obtained by condensation of aromatic tricarboxylic acid anhydride or its derivative with aromatic diamine (In the formula, R is

【formula】

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[Conventional technology]

Generally, permeable membranes are used to separate gases, liquids, liquids and solutes, etc., but it is important that the permeable membrane has durability against the gas or liquid that comes into contact with the membrane. If the substance in contact with the membrane is an ordinary gas or water, there is no problem because the membrane made from ordinary polymeric materials is durable, but if the substance in contact with the membrane is an organic liquid or a strong acid In the case of strong alkalinity or strong alkalinity, the durability of the membrane against these substances is very important. Problems with the durability of these membranes arise not only when the object to be separated is an organic liquid, but also in the case of separation membranes that use a carrier that has an affinity for a specific gas, which is called facilitated transport in gas separation. is important. That is, organic liquids are often used as carriers, their constituent ligands, or solvents for dissolving them, and when the durability of the membrane supporting the organic liquid of these carriers is poor, the carrier solution is used on the permeate side of the membrane. The problem of leakage occurs. Therefore, it is essential that the base membrane that supports the carrier solution has durability against the carrier solution, and that the base membrane is thin enough that the barrier to permeation of the substance to be separated is not a problem (in this case, a porous membrane is used). (meaning the thickness of the dense layer supported by the layer) is also required to have sufficient durability. [Purpose of the Invention] As a result of intensive studies based on the above-mentioned needs, the present inventors have found that the present inventors have developed a compound mainly of the general formula obtained by condensing an aromatic tricarboxylic acid anhydride or its derivative with an aromatic diamine. (In the formula, R is

【formula】

【formula】

【formula】

[Structure of the invention]

The present invention will be explained in more detail below. The polyamideimide resin used in the present invention is obtained by the reaction of trimellitic acid and aromatic diamine. It mainly consists of structural units represented by the general formula shown above, and such polyamide-imide resins have a combination of aromatic rings and imide bonds, so they exhibit excellent thermal stability, and they also have amide bonds, making them flexible. Demonstrates strength and strength. The above polyamideimide resin is (In the formula, R has the same meaning as R in the general formula shown above.) It may contain a small amount of a structural unit represented by the following. Film formation is performed by directly spinning, casting, or applying a film-forming solution obtained by dissolving the above-mentioned polyamide-imide resin in various organic solvents to a supporting substrate, and then, depending on the case, under a stream of inert gas and/or Alternatively, it can be carried out by evaporating at least a portion of the organic solvent by heating and then immersing it in a coagulating solvent. The membrane forming solution may contain certain additives. In terms of the form of the film, the film is formed by dissolving the above polyamide-imide resin in various organic solvents and casting the dove on the substrate, spinning it, or coating it on the support base material.
Depending on the case, the polymer may be coagulated by evaporating at least a portion of the organic solvent and then immersing it in a suitable solvent. The organic solvent used for film formation is not particularly limited as long as it can dissolve the above polyamideimide resin, but a solvent with a boiling point of about 30 to 300°C is selected, such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, etc. , N-methylpyrrolidone, etc. Alternatively, a plurality of solvents may be mixed. Further, in some cases, inorganic salts may be added thereto. The concentration of the polyamideimide resin contained in the dove is not particularly limited, but it is preferably 5 to 40% by weight. When forming a membrane from a dove, the membrane may be in the form of a sheet, a tube, or a hollow fiber. Further, a membrane may be formed only from the above-mentioned polyamide-imide resin, or it may be cast onto a flat or tubular support base material to form a composite membrane integrated with the support base material. The support base material is preferably a porous base material, and various organic and inorganic polymer materials, ceramics, metals, etc. are selected as the material. The membrane can also be reinforced by casting dove onto a fabric or the like. In some cases, after forming a film in the form of a sheet, a tube, or a hollow fiber, it is desirable to perform a slight drying treatment in order to form a dense layer on the surface of the film. In this case, the atmosphere on the surface of the membrane can be brought into a state where the evaporation of the solvent can be promoted by heating or air flow. There is no limit to the evaporation time, but in general
A time of 10 minutes or less is preferred. Next, these cast films are immersed in an appropriate solvent to coagulate and remove the film-forming solvent, but the coagulation solvent is a non-solvent and chemically inert for the polyamide-imide resin. A solvent that is compatible with additives such as a film-forming solvent or an inorganic salt is preferable. Examples of these solvents include water, alcohols, ethers, hydrocarbons, halogenated hydrocarbons, glycols, ketones, and alkyl cellosolves. Of course, a plurality of solvents may be mixed. The immersion temperature is generally below the boiling point of the solvent, usually from 0 to 150°C, preferably from 5 to 100°C. The immersion time is not particularly limited, but it is preferably long enough to remove the solvent or additives in the dove. Although it varies depending on the type of immersion solvent and the immersion temperature, the preferable range is usually 0.1 seconds to 100 hours.
It is also possible to change the solvent used for dipping midway through the process. The membrane thus obtained is finally preferably immersed in water, thoroughly removed from the organic solvent, and then dried. Drying conditions are not particularly limited as long as water evaporates, but drying is preferably carried out at a temperature of 5°C or higher and lower than 300°C. In order to facilitate the evaporation of water or a trace amount of residual organic solvent, the reaction can also be carried out under reduced pressure or under a stream of inert gas. In the present invention, the membrane thus obtained may be directly heated to 300 to 450°C for treatment, but in order to fully bring out the performance of the polyamide-imide resin, post-curing should be performed prior to the above heat treatment. It is preferable to keep it. That is, the molecular weight can be increased during the post-curing process, and its physical properties can be improved. Typical back pressure is 150-280
℃, for 1 to 100 hours, for example, 165℃ 20
Examples of conditions include further heating at 245°C for 24 hours, and finally at 260°C for 24 hours. It is desirable to raise the temperature of the post-cure stepwise from a low temperature to a high temperature. Therefore, post-curing can be performed following the drying step or concurrently with the drying step. Such post-curing up to 300° C. improves the physical properties of the film, but it is insufficient in terms of chemical resistance, and if it comes into contact with an organic solvent as it is, it will dissolve or swell. In the present invention, the film obtained as described above is cured directly or after the above-mentioned post-curing treatment.
Heat treatment is performed at ~450°C. The temperature may be raised all at once or may be raised in stages.
Although the time is not particularly limited, 0.1 to 100 hours is preferable. Preferred heat treatment conditions are 310-400°C for 1-10 hours. When the heat treatment temperature is high and the heat treatment time is long, the membrane material deteriorates and the membrane performance decreases. On the other hand, when the heat treatment temperature is low and the heat treatment time is short, the heat treatment effect is insufficient and the solvent resistance is not improved. [Examples] Next, the content of the present invention will be specifically explained by examples, but the present invention is not limited to the following examples. Comparative example Mainly by the reaction of trimellitic anhydride and aromatic diamine. The resulting polyamide-imide resin (product name “TORLON”, grade name
4000T, TORLON is a registered trademark) porous hollow fiber membrane (outer diameter 700μm, inner diameter 500μm) at 165℃ for 12 hours.
Heat treatment was performed by increasing the temperature sequentially: 245°C for 12 hours and 265°C for 24 hours. When the heat-treated hollow fibers were immersed in dimethyl sulfoxide and N-methylimidazole, the fibers were dissolved in about one hour, and the respective solvents were colored yellow. Example 1 The “TORLON” 4000T porous hollow fiber membrane used in the comparative example was heated at 165°C for 12 hours and at 245°C for 12 hours at 265°C.
After the same treatment as the comparative example for 24 hours at °C,
The yarn obtained by heat treatment at 300°C for 2 hours and then at 350°C for 3 hours was immersed in dimethyl sulfoxide and N-methylimidazole. The yarn did not swell in any of the solvents for at least 5 months, and no coloration was observed due to the respective solvents.
This indicates that the solubility of the yarn was improved by heat treatment at 300°C for 2 hours and then at 350°C for 3 hours. Example 2 The “TORLON” 4000T porous hollow fiber membrane used in the comparative example was treated in the same manner as in the comparative example, and then further treated.
Heat treatment was performed at 350°C for 3 hours. (The 2-hour treatment step at 300°C in Example 1 was omitted)
The resulting yarn has a resistance of at least 5 to both dimethyl sulfoxide and N-methylimidazole.
No swelling or dissolution phenomena were observed for several months. Example 3 The "TORLON" 4000T porous hollow fiber membrane used in the comparative example was heat treated at 165°C for 12 hours and then at 350°C for 3 hours. (The treatment steps of 245°C for 12 hours and 265°C for 24 hours were omitted) The obtained yarns were used in Examples 1 and 2.
Similarly, no swelling or dissolution phenomena were observed for either dimethyl sulfoxide or N-methylimidazole for at least 5 months. Example 4 The "TORLON" 4000T porous hollow fiber membrane used in the comparative example was heat treated at 165°C for 12 hours and then at 330°C for 2.5 hours. Similar to Examples 1, 2, and 3, the obtained yarn (treatment temperature was lowered compared to Example 3) did not exhibit swelling or dissolution phenomena for at least 5 months in both dimethyl sulfoxide and N-methylimidazole. I couldn't help it. A table summarizing the results of Comparative Examples and Examples 1 to 4.
Shown in 1.

[Table] Example 5 Heat treatment conditions similar to Example 4 (165°C for 2 hours,
Furthermore, 15 hollow fiber membranes (length 11 cm) were heated at 330℃ for 2.5 hours.
The bundles were bundled and the ends were sealed with bottling material to measure nitrogen and helium permeation performance. The results are shown in Table-2. The separation performance between helium and nitrogen determined from the ratio of permeation rates was 12.0.

〔Effect of the invention〕

The separation membrane obtained by the present invention is useful as a membrane for separations that require chemical resistance, regardless of gas separation, liquid separation, or separation involving various solutes. It is effective when used in combination with an organic liquid film containing

Claims (1)

[Scope of Claims] 1. Obtained by condensation of an aromatic tricarboxylic acid anhydride or a derivative thereof and an aromatic diamine,
Mainly general formulas (In the formula, R is a divalent aromatic group selected from the group consisting of [Formula] [Formula] [Formula] [Formula] and derivatives thereof.) 300～
Separation membrane obtained by heat treatment at a temperature range of 450℃.