JPH022842A - Laminated hollow yarn membrane - Google Patents

Abstract

PURPOSE:To obtain a laminated hollow yarn membrane having performance between that of a reverse osmotic membrane and that of an ultrafiltration membrane by forming a very thin membrane based on cross-linked polyamide and having a specified partition mol.wt. on a microporous support membrane having the shape of hollow yarn. CONSTITUTION:A very thin membrane based on cross-linked polyamide and having 80-600 partition mol.wt. under 2-10kg/cm<2> operation pressure is formed on the inner or outer surface of a microporous support membrane having the shape of hollow yarn to obtain a laminated hollow yarn membrane. The cross- linked polyamide is produced by bringing multifunctional amine and multifunctional acid halide into an interfacial polycondensation reaction. Since the very thin membrane having separating performance is formed on the support membrane having no separating performance, the laminated hollow yarn membrane has separating performance between that of a reverse osmotic membrane and that of an ultrafiltration membrane and a liq. mixture is separated by selective permeation through the membrane.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a composite semipermeable membrane having a hollow fiber shape for selectively permeating components of a liquid mixture, and This invention relates to a composite hollow fiber membrane with performance in the intermediate range between a permeable membrane and an ultrafiltration membrane.

[Prior Art] As a semipermeable membrane for reverse osmosis, a composite membrane in which an ultra-thin semipermeable crosslinked polyamide membrane is formed on a microporous support membrane has been developed, and is disclosed in U.S. Pat. No. 3,744,642; Same No. 3.9
26.798, JP-A-55-147106, etc. are known.

In addition, as a composite hollow fiber membrane, JP-A No. 62-95105
The publication describes a technique for continuously forming an ultra-thin film containing crosslinked metaphenylenediamine as a main component on the outer surface of a hollow fiber-like support crotch. Also, Utsuko Sho 61-1072
No. 4 discloses a technique for forming a membrane containing polyethyleneimine as a main component on the inner surface of a hollow fiber support membrane.

[Problem B to be solved by the invention] However, these conventional composite membranes only have reverse osmosis performance, and do not exhibit sufficient separation performance under ultra-transient operating conditions. Met.

In other words, in conventional separation membranes, membranes with reverse osmosis performance as described above, and membranes with ultra-permeability performance,
Although various membranes existed, there was a need for a membrane with intermediate performance, but there was no such membrane.

The present invention aims to eliminate such drawbacks,
The object of the present invention is to provide a composite hollow fiber membrane having a molecular weight cut-off of 80 or more and 600 or less.

[Means to solve the problem] In order to achieve the above object, the present invention consists of the following configuration.

"In a composite hollow fiber membrane formed at least from a microporous support membrane having a hollow fiber shape and an ultra-thin membrane covering the support membrane, the main component of the ultra-thin membrane is crosslinked polyamide, and the operating pressure is 2~ 10k (a composite hollow fiber membrane characterized by a molecular weight cut-off at 110tf of 80 or more and 600 or less.) In the present invention, the ultra-thin membrane is mainly composed of crosslinked polyamide, It is a membrane with separation performance,
This film is formed by an interfacial polycondensation reaction between a polyfunctional amine and a polyfunctional acid halide.

The polyfunctional amine may be any amine as long as it forms a crosslinked polyamide film, and may be either an aliphatic amine or an aromatic amine.

The aliphatic amine is preferably a diamine, and more preferably a secondary amine. When an aliphatic amine is used, it is particularly suitable for forming a composite hollow fiber membrane having a molecular weight cut-off of 300 or more. Specific examples of aliphatic amines include N,N--dimethylethylenediamine, and N.

N--dimethylpropanediamine, piperazine, 2-methylpiperazine, 2.5-dimethylpiperazine, 1.3
-bis(4-piperidyl)methane, 1,3-bis<4-
Piperidyl>ethane, piperazine-based diamines that are capable of forming 1,3-crosslinked piperazine polyamides are most preferably used.

The aromatic amine is preferably a diamine or a triamine, and is preferably used alone or in the form of a mixture of an aromatic diamine and an aromatic triamine.

As the aromatic diamine, m-phenylenediamine, p
- Phenyl diamine etc., but for forming the composite hollow fiber membrane having a molecular weight cut off of 80 or more according to the present invention, a secondary amine is preferable;
In order to form a composite hollow fiber membrane with a performance of 0 or more,
-grade amines are preferred. Among these, m-phenylenediamine is preferred because it allows formation of an ultra-thin crosslinked polyamide film with excellent water permeability.

As the aromatic triamine, 1,3,5-triaminobenzene is preferable from the viewpoints of high salt removal rate, organic matter removal rate, and structural stability of the ultra-thin film layer due to high crosslink density.

The above amines are used after being dissolved in water.

The polyfunctional acid halide includes the diamine, and
Any material may be used as long as it reacts with the mixture of the diamine and the triamine to form an ultra-thin crosslinked polyamide film, such as trimesic acid halide, isophthalic acid halide,
Aromatics such as benzophenone tetracarboxylic acid halide, trimellitic acid halide, pyromellitic acid halide, terephthalic acid halide, naphthalene dicarboxylic acid halide, diphenyldicarboxylic acid halide, and lysine dicarboxylic acid halide, benzenedisulfonic acid halide, chlorosulfonylisophthalic acid halide Examples include polyfunctional acid halides. Among them, trimesic acid chloride or a mixture of trimesic acid chloride and terephthalic acid chloride is preferable in consideration of the solubility in the membrane forming solvent and the performance of the composite hollow fiber membrane. In particular, when a mixture of an aromatic diamine and an aromatic triamine is used as the amine component, it is preferable to use a mixture of trimesic acid chloride and terephthalic acid chloride in consideration of separation performance.

The polyfunctional acid halide is used after being dissolved in an organic solvent. Such an organic solvent must be immiscible with water, dissolve the polyfunctional acid halide, and not destroy the microporous support membrane, and must be capable of forming a crosslinked polyamide through interfacial polycondensation. Either is fine. Preferred examples include n-hexane, cyclohexane, trichloroethane, and the like.

The thickness of the ultra-thin film can be arbitrarily selected depending on the purpose, but is preferably 10 nm to 1,000 nm. If the thickness is less than 10 nm, the film cannot exhibit its performance, i.
When the ooo limit is exceeded, the water overspeed decreases. 20nm~
More preferably, it is 30 nm.

The microporous support membrane having a hollow fiber shape of the present invention is a membrane that does not substantially have separation performance and supports the ultra-thin membrane,
Any conventionally known microporous support membrane may be used, but a membrane having an asymmetric structure is preferred. Among them, considering the workability of ultra-thin film formation and the membrane area of the module, the inner diameter is 300 to 1200 (μm) and the outer diameter is 400 μm.
A range of 1400 (μm) is preferable. moreover,
It is desirable that the material can sufficiently withstand a pressure of 10 kg/cITf or less. Such a microporous support membrane can be selected from various commercially available materials, but can usually be manufactured by a known wet demolition method.

In terms of chemical resistance, heat resistance, durability, pressure resistance, etc., the components of such a support film include polyacrylonitrile,
It is preferable that the main component is at least one selected from polysulfone and polyethersulfone.

In the present invention, it is possible to apply the coating to the inner surface, outer surface, or both surfaces of a microporous support membrane having a hollow fiber shape, but when an ultra-thin film is formed on the outer surface,
In consideration of problems such as the pressure resistance of the outer wall of the module, uneven concentration of the supplied liquid between hollow fiber membranes, and pressure loss, it is preferable to apply it to the inner surface.

In the method for producing a composite hollow fiber membrane of the present invention, first, when forming an ultra-thin membrane on the outer surface of a microporous support membrane having a hollow fiber shape, the support membrane is mixed with a polyfunctional amine solution or a polyfunctional amine solution. An ultra-thin film can be formed by immersion in an acid chloride solution.

When forming an ultra-thin film on the inner surface of a microporous support membrane, it is preferable to create a module by bundling the support membranes and potting both ends with an adhesive, and form the ultra-thin film in the module state. That is, coating or cleaning is performed by feeding an amine solution, a crosslinking agent, a cleaning liquid, etc. into the lumen of the support membrane in the module using a liquid pump. In particular, it is preferable to feed the amine solution and the crosslinking agent into the lumen of the support membrane at a constant rate, rather than sealing the amine solution and the crosslinking agent into the lumen of the support membrane and allowing them to stand for a certain period of time.

In the present invention, the content is preferably in the range of 0.2 to 10% by weight, regardless of whether it is an aliphatic amine or an aromatic amine. If the concentration of the amine solution is less than 0.2% by weight, it is difficult to form an ultra-thin film, and if it exceeds 10% by weight, a uniform ultra-thin film cannot be obtained. When using a mixture of aromatic diamine and aromatic triamine as the aromatic amine, the concentration range of the amine liquid is the same, but it is more preferably in the range of 0.2 to 5% by weight. In this case, the mixing ratio of aromatic diamine and aromatic triamine is preferably such that the aromatic triamine is contained in an amount of 5% by weight or more. When the aromatic triamine is contained in an amount of 5% by weight or more, the desalination properties and the low-molecular organic compound exclusion properties of the composite hollow fiber membrane are further improved.

On the other hand, the concentration of polyfunctional acid halide, which is a crosslinking component, is
It is preferably in the range of 0.1 to 2% by weight. In the case of aromatic polyfunctional acid halides, they may be composed of one component or may be a mixture of bifunctional and trifunctional acid halides, and the mixing ratio can also be selected arbitrarily. If the concentration of the polyfunctional acid halide is less than 0.1% by weight, the crosslinking density will decrease and stable membrane performance will not be obtained.

Moreover, if it exceeds 2% by weight, there is a risk of damaging the hollow fiber microporous support membrane.

In the present invention, "molecular weight cutoff" is determined by measuring the exclusion rate of a membrane for a solute with a known molecular weight. That is, an aqueous solution with a concentration of 11,000 pp is prepared using sugars such as glucose and sucrose and water-soluble organic substances such as isopropyl alcohol, ethylene glycol, and diethylene glycol as standard solutes at a temperature of 25°C and a pressure of 5°C.
The molecular weight of the solute at which an exclusion rate of at least 80% is obtained with ko/ayf is defined as the molecular weight cutoff of the membrane.

The composite hollow fiber membrane of the present invention has a molecular weight cut-off of 80 or more, 60
0 or less, and is economically and efficiently used in the concentration, separation from inorganic salts, and purification of water-soluble organic substances having a molecular weight within this range. For example, amino acids, peptides, sugars,
It is preferably used for so-called bioproducts such as organic acids, vitamins, and constituent substances.

[Example] In the following examples, as selective separation performance, the rejection rate of salt was determined by measuring electrical conductivity, and the rejection rate of water-soluble organic matter was determined by measuring refractive index.

In addition, as permeation performance, water overspeed was determined by the amount of water permeated per unit area and per unit day.

Example 1 A hollow fiber microporous support membrane made of polyacrylonitrile was coated with 1.0% by weight of piperazine and 1.0% by weight of trisodium phosphate.
% by weight, and then air-dried for 2 minutes at room temperature. Thereafter, it was immersed for 1 minute in a solution of 0.2% by weight of trimesic acid chloride dissolved in trichlorotrifluoroethane.

This support membrane was lifted from the acid chloride solution to volatilize the solvent adhering to the membrane surface, and then immersed in an aqueous solution containing 0.2% by weight of sodium carbonate for 1 minute, followed by thorough washing with water.

The composite hollow fiber membrane thus obtained was heated to a pressure of 3 k (J
/cnf, 500 ppm NaCl aqueous solution at 25°C.
As a result of an ultrafiltration test by feeding into the hollow fiber membrane lumen under the following conditions, the desalination rate was 50% and the water flow rate was 0.4Tr1! /Tr
Show the performance of 12 days. The molecular weight cut off with polyethylene glycol was 400.

Example 2 An aqueous solution containing 1.0% by weight of piperazine and 1.0% by weight of trisodium phosphate was injected into the inner cavity of a hollow fiber microporous support membrane made of polyacrylonitrile and applied to the inner surface of the hollow system. After removing the excess aqueous solution adhering to the inner surface by blowing nitrogen gas under pressure at room temperature, a solution of 0.2% by weight of trimesic acid chloride in trichlorotrifluoroethane was poured into the hollow system. The cavity was sealed for 1 minute. The solvent adhering to the inner surface was evaporated by blowing nitrogen gas into the inner cavity under pressure. Thereafter, an aqueous solution containing 0.2% by weight of sodium carbonate was injected, and distilled water was further allowed to flow down into the hollow membrane lumen for cleaning.

The thus obtained composite hollow fiber membrane was subjected to an ultra-extreme test using a 500 ppm NaCl aqueous solution under the same conditions as in Example 1. As a result, the desalination rate was 43% and the water overrate was 0.36 t.
It showed a performance of n'/Trf·day. Molecular weight cut off is 300
showed that.

Furthermore, using this composite hollow fiber membrane, ultrafiltration was performed at a pressure of 5 kg/ci and a 0.5% by weight aqueous solution of raffinose (molecular weight 504) as raw water at 25°C. As a result, the raffinose rejection rate was 95%. Water overspeed 0, 75 Tr
15/, 2.Showed old performance. On the other hand, the molecular weight is 34
An ultrafiltration test at 25°C of a 0.5 wt% sucrose aqueous solution (2) under a pressure of 5 k(]/cnf revealed that the sucrose rejection rate was 92%, and the water permeability was 0.7 m''/v2.・Showed the performance of the day.

Example 3 N, N on a hollow fiber microporous support membrane made of polysulfone
After impregnating with an aqueous solution containing 1.0% by weight of dimethylethylenediamine and 1.0% by weight of trisodium phosphate, the sample was air-dried for 2 minutes at room temperature.

Thereafter, it was immersed in a 0.2% by weight trichlorotrifluoroethane solution containing pyromellitic acid chloride and trimesic acid chloride at a mixing ratio of 1:1. After that, the same treatment as in Example 1 was carried out, and the obtained composite hollow fiber membrane was evaluated, and it was found that the NaCl removal rate was 35%, and the water overrate was 1.2 m'/m.
On the 2nd day, the molecular weight cutoff showed a performance of 600.

Example 4 Polyether sulfone instead of polyacrylonitrile,
A composite hollow fiber membrane was obtained in the same manner as in Example 2 except that a 1:1 mixture of 1,3-bis(4-piperidyl)propane and pyrazine was used instead of piperazine. When this membrane was evaluated under the same conditions as in Example 2, Na and C1 removal rates were 40%, water overrate was 0, and 30711'/T112.
The molecular weight cutoff was 500. The raffinose exclusion rate was 85%, and the sucrose exclusion rate was 73%.

Example 5 An aqueous solution containing 1.0% by weight of m-phenylenediamine was fed into the inner cavity of a microporous support membrane made of polyethersulfone in the shape of a hollow fiber, and the inner wall of the support membrane and the amine were fed for 2 minutes. Contact the aqueous solution. Next, nitrogen gas is blown into the inner cavity to remove excess adhering amine aqueous solution. Thereafter, a solution of 0.2% by weight of trimesic acid chloride dissolved in trichlorotrifluoroethane is injected into the lumen and left in contact with the inner wall of the support membrane for 1 minute. After the solution adhering excessively to the inner wall of the support membrane was evaporated by blowing nitrogen gas, an aqueous solution containing 0.2% by weight of sodium carbonate was fed into the inner cavity for cleaning.

The composite hollow fiber membrane thus obtained was heated to a pressure of 5 kg1.
As a result of an ultrafiltration test by feeding a 500 ppm NaCl aqueous solution into the hollow fiber membrane lumen at 25°C at 0yf,
Desalination rate 91%, water overspeed 0°09Tr1! /Tr12
・Showed the performance of the day.

Example 6 A hollow microporous support membrane made of polysulfone was prepared using a mixture of 1.0% by weight of m-phenylenediamine and triaminobenzene (60 parts of m-phenylenediamine,
After being immersed in an aqueous solution containing 40 parts of triaminobenzene) and 1.0% by weight of sodium hydrogen sulfite, it was air-dried for 2 minutes at room temperature. Thereafter, it was immersed for 1 minute in a trichlorotrifluoroethane solution containing 0.1% by weight of a mixture of trimesic acid chloride and terephthalic acid chloride (a mixture consisting of 50 parts of trimesic acid chloride and 50 parts of terephthalic acid chloride).

This support membrane was lifted from the acid chloride solution to volatilize the solution adhering to the membrane surface, and then immersed in an aqueous solution containing 0.2% by weight of sodium carbonate for 1 minute, followed by thorough washing with water.

The composite hollow fiber membrane thus obtained was heated to a pressure of 5 kg/
As a result of an ultrafiltration test using a 500 ppm NaCl aqueous solution under the conditions of cnf and 25°C, the performance showed a desalination rate of 90% and a water filtration rate of 0.10 TII3/m2·day.

Example 7 A mixture of 1.0% by weight of m-phenylenediamine and triaminobenzene (60 parts m-phenylenediamine, 40 parts triaminobenzene mixture consisting of),
An aqueous solution containing 1.0% by weight of sodium bisulfite is fed to bring the inner wall of the support membrane into contact with the amine aqueous solution for 2 minutes. In the same manner as in Example 5, after removing the amine aqueous solution adhering to the inner wall of the support membrane, a mixture of trimesic acid chloride and terephthalic acid chloride (a mixture consisting of 50 parts of trimesic acid chloride and 50 parts of terephthalic acid chloride) was removed. A trichlorotrifluoroethane solution containing .1% by weight is injected into the inner cavity, and a crosslinking reaction is carried out for 1 minute. Next, a trichlorotrifluoroethane solution was allowed to flow down from the inner cavity to volatilize the solution adhering to the inner wall, and then an aqueous solution containing 0.2% by weight of sodium carbonate was fed into the inner cavity for cleaning.

The composite hollow fiber membrane obtained in this way was subjected to an ultraviolet resistance test of an aqueous NaCl solution under the same measurement conditions as in Example 1. As a result, the desalination rate was 95%, and the water overrate was 0.12Tr13/T11.
It showed a performance of 2 days. Furthermore, when this composite hollow fiber membrane was subjected to an ultrafiltration test of an aqueous solution of 11,000 pp sucrose (molecular weight 342) at a pressure of 5 kCI10 (25°C), the rejection rate was 99%.

It exhibited a water overspeed of 0.10 m'/m2·day.

Example 8 A crosslinked aromatic polyamide membrane similar to that in Example 7 was formed in the inner cavity of a microporous support membrane made of polyacrylonitrile and having a hollow fiber shape. This composite hollow fiber membrane was subjected to an ultrafiltration test for an aqueous NaCl solution under the same measurement conditions as in Example 1, and as a result, the salt removal rate was 98%.

It showed performance of water overspeed 0°06T111/Tn2·day.

In addition, the sucrose rejection rate of 11,000 pp is at a pressure of 5
kg/cJ, 99% under 25℃ condition, water overspeed is 0
, 13 m'/m2・day.

Example 9 A crosslinked aromatic polyamide membrane similar to that in Example 6 was formed on the outer surface of a microporous support membrane made of polyacrylonitrile and having a hollow fiber shape.

This composite hollow fiber membrane was measured with NaC under the same measurement conditions as in Example 1.
□ c) Trl! /, showed performance of 2 days. The sucrose rejection rate of 11000pp is
Under the same operating conditions as Example 3, rejection rate was 99% and water overspeed was 0.
．． It was 08TI13/Tr12.day.

Example 10 The composite hollow fiber membrane used in Example 7 was treated with various water-soluble organic substances having different molecular weights, namely isopropyl alcohol (molecular weight 60), L-alanine (molecular weight 89), glucose (molecular weight 180), and sucrose (molecular weight 1342). ',
Fractionation characteristics were investigated using each aqueous solution of raffinose (molecular weight 504). Measurements were carried out at solute concentrations of 11,000 pp and 2
The test was carried out at 5° C. and an operating pressure of 5 k (J/cd).

The figure shows the relationship between the molecular weight and exclusion rate of these solutes.

According to the definition, the molecular weight cut-off of this composite hollow fiber membrane is 90, when the molecular weight when an exclusion rate of 80% is shown is defined as the molecular weight cut-off.

[Effects of the Invention] According to the present invention, it was possible to provide a composite hollow fiber membrane having a molecular weight cut-off of 80 or more and 6°O or less.

BRIEF DESCRIPTION OF THE DRAWINGS The drawing shows the relationship between the molecular weight of the solute and the exclusion rate in Example 10 of the present invention. Patent application Daitoshi Co., Ltd.

Claims (1)

[Claims] (1) A composite hollow fiber membrane formed at least from a microporous support membrane having the shape of a hollow fiber and an ultra-thin membrane covering the support membrane, in which the main component of the ultra-thin membrane is crosslinked polyamide, and the operating pressure is A composite hollow fiber membrane having a molecular weight cutoff at 2 to 10 kg/cm^2 of 80 or more and 600 or less.