JPS6253211B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to selective separation membranes. More specifically, the present invention relates to a separation membrane for gas separation that has an appropriate separation ability and an excellent permeation amount. BACKGROUND ART In recent years, technology for separating and purifying mixtures of various substances using separation membranes has been attracting attention as an energy-saving measure. For example, desalination of seawater using asymmetric cellulose acetate membranes, and hydrogen and oxygen concentration using composite membranes using silicone-based polymers as a coating layer are known. The silicone polymer used in the composite membrane has a large gas permeation rate and has excellent properties as a material for separation membranes. However, it has the disadvantage that it has low strength and poor film-forming properties, making it difficult to produce extremely thin films. On the other hand, it has good film forming properties,
Further, polycarbonate and polysulfone are known as materials with excellent heat resistance. for example,
It is known that polycarbonate and polysulfone containing 2,2-bis(4-hydroxyphenyl)propane as a monomer have a high glass transition temperature and good moldability. However, these polymers have poor separation performance and permeation rate, and cannot be used practically. The present inventors have arrived at the present invention as a result of intensive studies aimed at improving the gas separation performance, particularly the permeation amount, of the above-mentioned polymer with good moldability. That is, it consists of bisphenol represented by the following general formula () and one or more types of bisphenols selected from the compounds represented by the following general formula (), and the bisphenol represented by the general formula () forms a polymer. It has been found that the gas permeation rate of a membrane obtained from polycarbonate containing 30 to 80 mol % of the total bisphenol contained therein is significantly improved. (However, A is -O-, -S-, -SO-, -SO ₂ -, -
It represents CO- or a divalent organic group having 1 to 12 carbon atoms. ) (However, R ¹ and R ² are the same or different groups selected from monovalent organic groups having 1 to 6 carbon atoms, and R ¹
When is a monovalent organic group having 3 or more carbon atoms, R ²
is a hydrogen atom or a monovalent organic group having 2 or less carbon atoms. R ³ and R ⁴ represent the same or different groups selected from a hydrogen atom or a methyl group. B is -O
-, -S-, -SO-, _-SO2- , -CO-, or a divalent organic group having 1 to 12 carbon atoms. ) In particular, when the copolymerized polycarbonate separates an organic gas and an inorganic gas, as shown in the examples, both the separation ability and the permeation amount are improved. This is thought to be due to the organic substituent that compound () has, but it is not clear. When the copolymerized polycarbonate is combined with a symmetrical or asymmetric porous membrane obtained from an inorganic or organic material, the separation layer can be made thinner, and an even better separation membrane can be obtained. As the bisphenol compound used in the copolymerized polycarbonate in the present invention, compounds represented by the general formulas () and () are used. In the formula, A and B are 2 having 1 to 12 carbon atoms.
The higher the valence organic group, the better the compatibility between the monomers and the better the polymer that can be used as a membrane material. Preferred specific examples of the compound represented by the general formula () include 4,4'-dihydroxydiphenylmethane, 1,1-bis(4-hydroxyphenyl)
Examples include ethane, 2,2-bis(4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)butane, and 1,1-bis(4-hydroxyphenyl)cyclohexane. Preferred specific examples of the compound represented by the general formula () include 2,2-bis(4-hydroxy-
3,5-dimethylphenyl)propane, 1,1-
Bis(4-hydroxy-3,5-dimethylphenyl)butane, 1,1-bis(4-hydroxy-
3,5-dimethylphenyl)cyclohexane, bis(4-hydroxy-3,5-dimethylphenyl)methane, 2,2-bis(4-hydroxy-2
-Methyl-5-tert-butylphenyl)propane, 1,1-bis(4-hydroxy-2-methyl-5-tert-butylphenyl)butane, 1,1-
Bis(4-hydroxy-3-tert-butylphenyl)butane, bis(4-hydroxy-2-methyl-5-tert-butylphenyl)methane, 2,2-
Bis(4-hydroxy-3,5-diethylphenyl)propane, 1,1-bis(4-hydroxy-
3-tertbutylphenyl)cyclohexane, bis(4-hydroxy-3-iso-propylphenyl)
Examples include methane. The bisphenols may be used as a mixture of two or more. The amount of bisphenols used is
It accounts for 30 to 80 mol% of the total bisphenols used in the copolymerized polycarbonate. A particularly preferred usage amount is 35 to 70 mol%. The method for synthesizing polycarbonate of the present invention does not require any special measures. For example, a method in which approximately equimolar amounts of diphenyl carbonate and bisphenols are subjected to heat melt polycondensation in the presence of a suitable catalyst, a method in which phosgene and bisphenols are subjected to interfacial polycondensation,
Reacting phosgene and bisphenols in solution,
Examples include a method of performing polycondensation. The resulting copolycarbonate is processed into homogeneous or asymmetric membranes. As a method for manufacturing the membrane, a conventional method is employed. For example, a method in which a homogeneous membrane is produced by a dry method from a solution of the copolymerized polycarbonate dissolved in an appropriate amount in a soluble solvent, and a method in which an asymmetric membrane is produced by an air gap film forming method after mixing appropriate additives with the solution. , a method of producing a homogeneous film by a melting method, and the like. The form of the membrane is not particularly limited, such as hollow fibers or flat membranes. The thickness of the film is preferably about 0.1 to 300 μm in the case of a homogeneous film, and about 0.005 to 10 μm in the case of an asymmetric film. Examples of methods for compounding a symmetrical or asymmetrical porous membrane obtained from an organic or inorganic material include a method in which a dilute solution of copolymerized polycarbonate is uniformly applied to the surface of the porous membrane and dried, or the method described above. Examples include a method in which a homogeneous thin film of the copolymerized polycarbonate prepared by is pressure-bonded to a porous membrane, and a method in which a thin film is formed by reactive polycondensation of phosgene and bisphenols on the porous membrane. The material of the porous membrane serving as the support is not particularly limited. Examples include cellulose such as cellulose acetate, aromatic polyamides and polyimides such as polyparaphenylene terephthalamide and polymethaphenylene isophthalamide, organic materials such as polysulfone, polycarbonate, and polytetrafluoroethylene, and inorganic materials such as glass. It will be done. The form of the porous membrane serving as the support is not particularly limited, such as hollow fibers or flat membranes. However, appropriate surface treatment is required depending on the adhesion to the copolymerized polycarbonate. The thickness of the copolycarbonate layer in the composite membrane is preferably about 0.005 to 10 μm. The present invention is characterized by the discovery that the amount of gas permeation can be improved by copolymerizing polycarbonate with a specific amount of specific bisphenols, and it is also possible to separate organic gases and inorganic gases. It has been found that both the separation power and the amount of permeation are improved when this is done. In the examples below,
Although such effects are specifically shown, the present invention is not limited thereto. Example 1 Diphenyl carbonate was placed in a polymerization vessel equipped with a stirrer, nitrogen gas inlet pipe, and distilled phenol receiver.
12.73g (0.0595 mol), 2,2-bis(4-hydroxyphenyl)propane 5.42g (0.0238 mol), 1,1-bis(4-hydroxy-2-methyl-5-tert-butylphenyl)butane 13.64g
(0.0357 mol) and 0.03 g of lithium acetate were taken, and the nitrogen substitution was repeated three times. Then 250℃
The monomer is melted uniformly by inserting it into an oil bath and stirring for 10 minutes under a stream of nitrogen. Afterwards, the pressure is gradually reduced to 1 mmHg or less over 120 minutes.
During this time, the oil bath temperature is set to 280°C for 30 minutes. 1mm
After continuing polymerization for 30 minutes at a pressure below Hg, the pressure is returned to normal using nitrogen gas and the polymer is taken out. The obtained polymer was a light brown solid with a reduced specific viscosity of 0.18. This polymer is called Polymer A
shall be. However, the measurement conditions for reduced specific viscosity are solvent phenol/1,1,2,2-tetrachloroethane614
(weight ratio), concentration 125 mg/25 ml, and temperature 30°C. Comparative Example 1 Polymers a, b, and c shown in Table 1 were obtained in the same manner as in Example 1.

[Table] Example 2 3g of each of the polymers shown in Table 1 was mixed in 1.1.
120 in 30ml of 2,2-tetrachlorethane at 50℃
Stir for a minute to dissolve. The solution was cast onto a horizontally held polypropylene film using a 100μ applicator. By leaving the mixture at 17 to 20°C for 12 hours or more, a thin film with a thickness of about 10μ was obtained.
After measuring the thickness of the thin film, it was cut into a circle with a diameter of 47 mm and placed in a gas permeability measurement cell. The cell was attached to a gas permeation performance measurement device adjusted to a gas pressure of 5 Kg/cm ² , and the amount of gas permeation was measured using a soap membrane flowmeter, and the permeation coefficient and permeation rate ratio were calculated. The results are shown in Table 2. Regarding Polymer C, the obtained membrane had no flexibility, and gas permeation performance could not be measured.

[Table] Polymer A has improved permeability coefficient and permeation rate ratio compared to polymers a and b. Example 3 Polymers B and C shown in Table 3 were obtained in the same manner as in Example 1. Comparative Example 2 Polymer d shown in Table 3 in the same manner as Example 1
I got it.

【table】

[Table] Example 4 Polymer membranes shown in Table 3 were prepared in the same manner as in Example 2, and their gas separation performance was measured. The film of polymer d was not flexible and broke during the measurement. The results are shown in Table 4.

Claims (1)

[Scope of Claims] 1 Consists of one kind of bisphenol of the compound represented by the following general formula (1) and one or more kinds of bisphenols selected from the compounds represented by the following general formula (), A selective separation membrane obtained from a polycarbonate in which bisphenol represented by the formula () accounts for 35 to 70 mol% of the total bisphenols constituting the polymer. (However, A is -O-, -S-, -SO-, -SO ₂ -, -
Represents CO- or a divalent organic group having 1 to 12 carbon atoms. ) (However, R ¹ and R ² represent the same or different groups selected from monovalent organic groups having 1 to 6 carbon atoms, and when R ¹ is a monovalent organic group having 3 or more carbon atoms, , R ² is a hydrogen atom or a monovalent organic group having 2 or more carbon atoms. R ³ and R ⁴ are the same or different groups selected from a hydrogen atom or a methyl group. B is -O −, −S−, −SO−, −SO ₂ −, −CO−
Or it represents a divalent organic group having 1 to 12 carbon atoms. 2. The separation membrane according to claim 1, which uses a composite membrane in which a thin film obtained from the polycarbonate is provided on a symmetrical or asymmetrical porous membrane obtained from an organic or inorganic material.