JPS60125205A - Improvement in preparation of polyimide membrane - Google Patents

Abstract

PURPOSE:To enhance separation property without lowering a permeation speed, in preparing a membrane, by adding a definite amount of a specific aliphatic carboxylic acid compound in a dope consisting of polyimide and a phenolic compound. CONSTITUTION:A polymer used as a membrane comprises aromatic polyimide having 90% or more of a repeating unit represented by formula in its main chain. This polymer is dissolved in a phenolic solvent, especially, halogenated phenol with a b.p. of 300 deg.C or less to prepare a dope to which specific aliphatic carboxylic acid such as undecanoic acid, lauric acid or oleic acid is, in turn, added in an amount of 5-40%wt. of polyimide. A membrane with a thickness of 10-500mum is formed from this dope and immersed in a coagulation bath consisting of an org. liquid freely mixed with the phenolic solvent and water to be coagulated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the production of polyimide semipermeable membranes.

In particular, aromatic poly and imide semipermeable membranes are chemical resistant.

It holds great promise as a heat-resistant semipermeable membrane with excellent mechanical properties.

OQ (where RU is a divalent residue excluding the amine group of an aromatic diamine) is used to form a liquid thin film of the polyimide composition by using a ()0 reimide composition. This is a method for producing a polyimide semipermeable membrane, which is characterized by forming a polyimide semipermeable membrane, and then immersing the thin film in a coagulating liquid to coagulate it.

As a result of various studies to further improve the above invention, the present inventors have discovered that a polyimide composition consisting of polyimide and a phenolic compound, that is, a dope solution, is made by adding a certain amount of a specific aliphatic carboxylic acid compound. When a semipermeable membrane is manufactured by membrane coating, the semipermeable membrane has significantly superior gas permeation performance compared to the semipermeable membrane manufactured by the method of the invention described above.

In particular, it improves the resolution without reducing the permeation rate (C)
A polyimide characterized by solidifying a specific aliphatic carboxylic acid compound into a homogeneous mixture of the above polyimide and a phenolic solvent (where R is an aromatic compound represented by the general formula H2N -R-NH2). 90% or more of the total structural units, preferably 95
It is an aromatic polyimide that has a polymer main chain in a proportion of 1 or more, and is soluble in a melt of a phenolic compound.

The above aromatic polyimide has +:S++da, 4.4'-
Biphenyltetracarboxylic acid component, 2,3.3',4
A biphenyltetracarboxylic acid component such as '-biphenyltetracarboxylic acid component, and a general formula 112N '-H-N
Shi'-q obtained from the aromatic diamine component represented by H2 by a polycondensation reaction and an imidization reaction (imide cyclization reaction) has a melting point of about 1. OO'C or less, preferably 80.degree. C. or less, and its boiling point is about 300.degree. C. or less at normal pressure.

4 Preferably phenolic compounds having a temperature of 280°C or less are preferred 1 For example, phenol, o-, m-.

'1*Idp-monohydric phenols such as cresol, 3,5-xylenol, carvacrol, and thymol.

Alternatively, the hydrogen of the -valent phenol can be
i! Preferred examples include phenols which have been converted to

Particularly, the halogenated phenol has the general formulas R and R.

(However, in the above general formula, it is represented by 1 (M is hydrogen or an alkyl group having j-3 carbon atoms, and xu:] is a rogen atom), and its melting point is about 100°C or less,
Preferably, the temperature is 80°C or lower, and the boiling point is about 30°C at normal pressure.
The halogenated phenol compound having a temperature of 0° C. or lower, preferably 280° C. or lower is polyy'y', 3-chloro-6-hydroxytoluene, 4-chloro-2-hydroxytoluene, 2-chloro-4-hydroxytoluene, 2-chloro-6-hydroxytoluene, Bromo-5-human 10-oxytoluene, 3-7'bromo-5-hydroxytoluene, 3-7'bromo-6-hydroxytoluene.

Examples include 4-bromo-2-hydroxytoluene.

In the polyimide composition used in the invention, 5 to 40% by weight of a specific aliphatic carboxylic acid compound based on the polyimide is used as a polyimide composition, that is, a dope solution.

included in. If the above conditions are not met, it is not suitable because sufficient separation cannot be obtained or the permeation rate is low.

Saturated-basic acids such as mitic acid, eicosanoic acid, behenic acid, hentriacontanoic acid, stearic acid.

lO-undecenoic acid, elaidic acid, oleic acid.

Unsaturated basic acids such as brassic acid, lylic acid, erucic acid, stearic acid, behenolic acid, polybasic acids such as dodecanoic acid, crocetin, bixin, 8.9-dihydroxydioctadecanoic acid, 10-hydroxyoctadecanoic acid, g, xo-epoxystearic acid and other carboxylic acid derivatives.

The liquid polyimide composition, ie, dope, used in the method of the present invention contains (a) at least 5% by weight of the polyimide, based on the total composition, and (c) a specific aliphatic carboxylic acid compound containing the polyimide. It is necessary to contain at least 5 to 40% by weight of the component, and if the composition has a component ratio outside this range, it is difficult to obtain a semipermeable membrane with the excellent permeability performance that is the objective of the present invention. Undesirable.

As described above, the present invention is directed to the excellent properties of a semipermeable membrane produced by using polyimide and a phenolic solvent as a bobbing solution in which a specific aliphatic carboxylic acid compound is added to the polyimide. In addition to having the same heat resistance, chemical resistance, and similar properties, there is a marked improvement in gas permeation rate. Therefore, the semipermeable membrane obtained by the production method of the present invention is suitable for use in selectively separating a desired gas from a mixture of various gases.

Examples of combinations of gases constituting such a gas mixture are 9, for example, hydrogen and carbon monoxide, hydrogen and hydrogen, and diacid f.
Arsenic carbon and methane, helium and methane.

Examples include combinations of helium and nitrogen.

When carrying out the method of the present invention, if a phenolic solvent is used as a reaction solvent for the polyimide synthesis reaction, it is necessary to add more phenolic solvent to the reaction mixture as needed to maintain concentration, composition, viscosity, etc. After adjustment, a specific aliphatic carboxylic acid compound as described above is added and mixed uniformly, and used as a polyimide composition for film formation.

In the method of the present invention, the polyimide composition and the aromatic polyimide are heated at 30°C and at a concentration of 05.

, 97100m Solvent (more preferably 4 volumes of parachlorophenol) A wide range of i40.5 to 4.0 can be used.

In the method of the present invention, polyimide composition e.

The concentration of the total polyimide contained is preferably in the range of 6 to 30% by weight, more preferably 8 to 25% by weight based on the total composition. Further, it is preferable that the composition under Boli 5 becomes a uniform liquid composition of about 10,000 poise at a film forming temperature of 0 to 120° C.*i-, and becomes a dope solution for the # film.

In the method of the present invention, the above-mentioned polyimide composition is heated if necessary and used as a dope solution for film formation, and the dope solution of the polyimide composition is used to form a liquid thin film (for example, a flat film shape, a hollow fiber shape). , a tubular thin film) is formed.9 Then,
It is preferable to use the thin film in the center of the coagulation liquid or to sufficiently degas it to obtain a dope liquid for film formation.

A method for forming a liquid thin film from a dope solution of a polyimide composition can be carried out by a method similar to the conventionally known casting film forming method. Alternatively, the dope solution of the polyimide composition is cast on the surface of the roll and the dope solution of the polyimide composition is then formed into a liquid thin film with a uniform thickness using a Dr. The polyimide composition is supplied and cast to a uniform thickness with a doctor knife placed close to the roll surface to form a thin film, or the polyimide composition is extruded into a thin film from a T-die and wound around the roll surface to form a thin film. A continuous film forming method such as forming a film can be adopted. In the method of the present invention, the temperature of the dope solution of the polyimide composition during film formation should be set to a temperature that provides a rotational viscosity suitable for film formation, depending on the relationship between the rotational viscosity of the polyimide composition and temperature. However, if possible, 0 to 120℃,
Particularly within the temperature range of about 5 to 100 degrees Celsius, while forming a liquid thin film or after forming a liquid thin film. It is preferable to partially evaporate the phenolic bath agent from one side of the liquid thin film because an asymmetrical thin film is effectively formed by the ninth-order solidification.

A method of partially evaporating the phenolic solvent from one side of a liquid thin film is to apply 0 to
~100°C, especially 5-90°C gas for at least 1 second, especially 5 seconds to 30 minutes.

A method of spraying for 10 seconds to 20 minutes is preferable, but the liquid thin film on the peripheral surface of the plate or roll is heated and placed in a reduced pressure atmosphere for at least several seconds.

Especially for 10 seconds to 30 minutes, and further for 30 seconds to 20 minutes.

A method of leaving it alone may also be used.

In the method of the present invention, the coagulating liquid used to coagulate the polyimide liquid thin film formed as described above may be any liquid that is freely mixed and compatible with the phenolic solvent.゛: Ethers such as ethylene glycol monomethyl ether, amides such as dimethyl acetamide and dimethyl formalum amide, dimethyl sulfoxide, etc., or a mixture of water and the above-mentioned alcohols, ketones, ethers, and amides. etc. can be mentioned. In particular, as a coagulating liquid, the mixing ratio (relative to the unit amount of water used) is C1.1 to 10. Especially 0.2
A mixed solution of water and alcohols, water and ethers, water and ketones, or water and amides having a molecular weight of about 5 to 5 is preferable.

A method for coagulating a liquid thin film with the above-mentioned coagulating liquid is as follows.

Any known method may be used to form a thin film.

Together with the substrate on which the thin film is formed (cast).

It is preferable to immerse it in the above-mentioned coagulating liquid, and the temperature of the coagulating liquid is preferably 50°C or less, particularly -10 to 30°C, and more preferably about -5 to 20°C. The time for which the thin film is immersed in the coagulation solution as described above varies depending on the type of polyimide composition, the type of coagulation solution, and other conditions, but is generally 0.1 to 20 hours, 0.5 hours. to 10
After heating for about 1 hour, the film becomes a membrane with a porous layer.
℃ for about 0.5 to 10 hours, and post-treatment is performed to wash and remove residual fume, mail solvent, etc. in the coagulated film.

A dry semipermeable membrane is obtained by immersion treatment in aliphatic hydrocarbons such as , , , , , and the like, and then dried. If necessary, heat treatment may be performed.

Next, reference examples (polyimide synthesis examples), examples, and comparative examples are shown.

In the Examples and Comparative Examples, the gas permeation performance of the semipermeable membrane was determined by the following method.

Dry membrane area: 14.65c++! Set it in a stainless steel cell, and supply hydrogen gas to one side of the cell at I kg/art.
was introduced under pressure, and the rate at which hydrogen gas permeated through the membrane was measured using a flow meter. - Carbon oxide was also measured in the same way. Note that the measurement temperature was maintained constant at 30° C. using a constant temperature bath. The permeability and resolution were calculated from the obtained measured values according to the 9th order equation.

40 mmol of 4,4'-diaminodiphenyl ether, and 165 r of chlorophenol (:pcp) were added to a stirrer and a nitrogen sludge inlet pipe, 1, '', etc. Pour one reaction solution into a separable flask, circulate nitrogen gas, and stir while stirring.
The temperature was raised to 0'C in about 50 minutes, and the reaction solution was further heated to 1
The mixture was held at 80° C. for 8 hours to carry out one-step polymerization and one-stage ibedization to produce aromatic polyimide and produce a viscous and uniform solution of polyimide.

The polyimide homogeneous bath solution has a polymer crush degree of about 10
% by weight, and the logarithmic viscosity of the polymer (50°C, 0.5
9/100mj! PCiP ) is 2.2, and the imidization rate of the polymer is 95 as measured by infrared absorption spectrum.
It was more than 1.

Comparative Example 1 A homogeneous solution of polyimide produced in Reference Example was cast on a glass plate at 60° to form a thin film with a thickness of 0.2 nvn, and after being left at 60°C for 3 minutes (drying time), The thin film was coagulated with a mixture of 1 volume of ethanol and 1 volume of water, air-dried at 1°C for 5 hours, and then dried at 100°C for 1 hour to obtain a polyimide film.

Table 1 shows the film forming conditions and membrane permeability characteristics.

゛Comparison 2 Film formation was 800. Comparative lpH except that the drying time was 2 minutes.
This was done in the same manner as in step 1. Film forming conditions and results are shown in Table 1.

Examples 1 to 7 and Comparative Examples 3 to 5 Additives shown in Table 1 were added to a homogeneous solution of polyimide produced in the same manner as Reference 1911 at a predetermined level for the polymer.
- The same procedure as in Comparative Example 1 was carried out except that the film was formed under the film forming conditions shown in Table 1 after being added to the solution and oozing out to form a homogeneous solution.

The transmission characteristics of each are shown in Table 1.

Claims (1)

[Claims] (a) 1 g of polyimide whose general formula is 90% or more! or two or more: (b) phenolic solvent: and (c) add an aliphatic carboxylic acid compound represented by the general formula R+C0OH)n to a homogeneous mixture of the above polyimide and phenolic solvent in an amount of 5 to 40 times the weight of the polyimide. A liquid thin film of the polyimide composition is formed using a polyimide composition containing H, and the thin film is then soaked in a coagulating liquid.
A method for producing a polyimide semipermeable membrane, characterized by solidifying it by immersing it in a polyimide membrane.