JPS61257202A - Separation membrane - Google Patents

Abstract

PURPOSE:To obtain a separation membrane having high durability to org. liquid exhibiting effective behavior as liquid film for prompting transportation by heat treating an arom. polyamideimide polymer film at 300-450 deg.C. CONSTITUTION:A polyamide imide resin consisting of a unit structure as shown by the figure obtd. by the reaction of trimellitic acid with arom. diamine is used. The resin has superior heat stability, flexibility and toughness. The resin is dissolved in a solvent having 30-300 deg.C b.p. to 5-40wt% concn. The solvent is evaporated within 10min after casting and the film is dipped in a coagulating bath. the coagulation is performed at 0-15 deg.C, then the film is dried at 5-300 deg.C. The obtd. film is cured at 150-280 deg.C for 1-100hr and heat-treated at 300-450 deg.C for 1-100hr.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a separation membrane with excellent chemical resistance, particularly durability against organic liquids. Specifically, it is a divalent aromatic group mainly selected from the group consisting of derivatives of the general formula % and the like obtained by condensation of an aromatic tricarboxylic acid anhydride or its derivative with an aromatic diamine. ) A film of a polymer consisting of structural units represented by 300 to q
The present invention relates to a separation membrane with excellent chemical resistance obtained by heat treatment in the temperature range of 0°C.

[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. In other words, 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, carrier B solution may be permeated through the membrane. The problem arises of leakage to the sides. Therefore, it is essential that the base membrane supporting the carrier solution has durability against the carrier solution, and the base membrane must be thin enough that the barrier to permeation of the substance to be separated is not a problem [here, porous It refers to the thickness of the stratum densa supported by the stratum densa. ) 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 two compounds obtained by the condensation of an aromatic tricarboxylic acid anhydride or a derivative thereof and an aromatic diamine are mainly selected from the group consisting of derivatives having the general formula: is a valent aromatic group. ) A film of a polymer consisting of structural units shown in
The present invention was achieved by discovering that a separation membrane obtained by heat treatment in the temperature range of 0.degree. C. has excellent chemical resistance, especially durability against organic liquids.

[Structure of the invention]

These polyamide-imide resins exhibit excellent thermal stability due to their combination of aromatic rings and imide bonds, and they also contain amide bonds. It shows flexibility and toughness.

The polyamide-imide resin may contain a small amount of a structural unit represented by (wherein R has the same meaning as R in the general formula shown above).

Sa is prepared 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 base material, and then, depending on the case, under a stream of inert gas and/or by heating. This can be carried out by evaporating at least a portion of the organic solvent and then immersing it in a coagulating solvent. The membrane forming solution may contain certain additives.

Film formation involves dissolving the above polyamide-imide resin in various organic solvents and casting the dope onto a substrate, spinning it, or coating it on a supporting base material. After evaporating at least a portion of the solvent, immerse it in a suitable solvent and! Coalescence can be performed by solidifying.

The organic solvent used for film formation is not particularly limited as long as it can dissolve the polyamideimide resin, but a solvent with a boiling point of about 30 to 300°C is selected, such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, etc. Selected from N-methylpyrrolidone and the like. or,
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 dope is not particularly limited, but it is preferably 5 to 410% by weight. When forming a membrane from Dogue, the membrane may be in the form of a sheet, a tube, or a hollow fiber. The membrane may be formed only from the polyamide-imide resin described above, 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 dope can also be cast onto a fabric to strengthen the membrane. Depending on the case, it is desirable to perform a slight drying treatment to form a dense layer on the membrane surface after forming the membrane in the form of a sheet, tube, or hollow fiber.

In this case, the atmosphere on the surface of the membrane can be brought into a state where the evaporation of the υ solvent can be promoted by heating or air flow.

The time for one shot is not limited, but generally a time within lσ minutes is preferable. Next, these cast films are immersed in a suitable solvent to coagulate and remove the film-forming solvent, but the coagulating solvent is a non-solvent and chemically inert for the polyamide-imide resin. A solvent that is compatible with the film forming solvent or additives such as inorganic salts is preferred.

Examples of these solvents include water, alcohols, ethers, hydrocarbons, halogenated hydrocarbons, glyco-7++/s, 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 isoC, preferably from 3 to iooC. The immersion time is not particularly limited, but it is preferably long enough to remove the solvent or additives in the dope. Although it varies depending on the type of immersion solvent and the immersion temperature, a range of usually 0.7 seconds to 100 hours is preferable. It is also possible to change the solvent used for dipping in the middle of the process. The membrane thus obtained may finally be treated by preferably immersing it in water and heating it to a high temperature, but in order to fully bring out the performance of the polyamide-imide resin, it should be cured prior to the above heat treatment. Conditions such as a high temperature at 160° C. and finally a high temperature at 160° C. are exemplified. 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 process or concurrently with the drying process.

Although the physical properties of the film are improved by such post-curing up to 300°C, the chemical resistance (t') is insufficient, and if it comes into contact with an organic solvent as it is, it will dissolve or swell.

2. In the present invention, the film obtained by K as described above is directly cured or after the above-mentioned post-curing treatment, JOO~1IS is applied.
Heat treatment is performed at 0°C.

The temperature may be raised all at once or may be raised in stages. Although the time is not particularly limited, o, i to ioo times are preferable. The preferred heat treatment conditions are Jlo-4100℃ and 7
~/θ time. 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.

〔Example〕

Next, the content of the present invention will be specifically explained using examples.
The present invention is not limited to the following examples.

Comparative Example A polyamide-imide resin obtained by the reaction of trimellitic anhydride and aromatic diamine (trade name: 'TORIiON I', grade name: I
I000T, TORLON is a registered trademark of porous, 26S''C# moss, followed by heat treatment at successively higher temperatures for 3! This shows that the solubility of the yarn was improved by adding a heat treatment.

Example [The 700'c6 hour processing step of Example 1 was omitted]
The obtained yarn swelled at least for a month in both dimethyl sulfoxide and N-methylimidazole;
No dissolution phenomenon was observed.

Example 3 'TORLON'1ll17T Φ used in comparative example
The porous hollow fiber membrane was heat-treated for 72 hours and then for 3 hours at 10°C for 3 hours.
, 24tj°C, -43°C, time, -43;'ca, time treatment step was omitted] The obtained yarn was the same as in Examples 1 and 2.
No swelling or dissolution phenomena were observed for either dimethyl sulfoxide or N-methylimidazole for at least 5 months.

'TORLON' used in the example and comparative example
The porous hollow fiber membrane of
C74, O obtained by heat treatment for 5 hours (treatment temperature lowered compared to Example 3) is Example/,! , 3, no swelling or dissolution phenomena were observed for either dimethyl sulfoxide or N-methylimidazole at least in the S evening.

The results of Comparative Example and Example/-4 are summarized in Table-1.

Example S Same heat treatment conditions as Example Tei (/g s ℃-4-E
time, further 330℃ - 2.5 hours) Nitto thread membrane (length 1
lclrL) were bundled together, the ends were hardened with a botting material, and the permeability of nitrogen and helium was measured. Display the results -
Shown in 1. The separation performance between helium and nitrogen determined from the ratio of permeation rates was 72.0.

〔Effect of the invention〕

The separation membrane obtained according to 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, and is particularly useful for facilitated transport. It is effective when used in combination with an organic liquid film containing a carrier substance.

Claims (1)

[Claims] (1) aromatic tricarboxylic acid anhydride or its derivative;
There are mainly general formulas ▲mathematical formulas, chemical formulas, tables, etc., obtained by condensation with aromatic diamines. It is a divalent aromatic group selected from the group consisting of ▼, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, and their derivatives.) A separation membrane obtained by heat-treating a polymer membrane consisting of units at a temperature range of 300 to 450°C.