JP2505428B2 - Low-temperature dissolving stock solution and method for producing the same - Google Patents

Description

The present invention relates to a low temperature dissolution type stock solution and a method for producing the same.

[Conventional technology]

Conventionally, many polymer compounds such as cellulose acetate, polyacrylonitrile, polymethylmethacrylate, polyamide, polyolefin, polyimide, polycarbonate, polyarylate, polysulfone, and polyester have been used as membranes and coating agents. In particular, polyacrylonitrile / polymethylmethacrylate /
There are many membranes made of hydrophobic polymers such as polyolefins, polyimides, polycarbonates, polyacrylates, polysulfones, and polyesters. In particular, the following means has been proposed as a means for forming a porous film for a material having a strong intermolecular cohesive force such as a polysulfone resin.

A method that utilizes microphase separation between different polymers. (JP-B-48-176, JP-A-54-144456, 57-5)
No. 0506, No. 57-50507, No. 57-50508) A method having an extraction / elution operation after film formation. (JP-A-54
No. 26283, No. 57-35906, No. 58-91822) A method for forming a film in a metastable liquid dispersion state of a film forming stock solution.
(JP-A-56-154051, JP-A-59-58041, JP-A-59-58041)
No. 183761 and No. 59-189903) A method of devising a device during spinning (Japanese Patent Laid-Open No. 59-228016) However, this method only utilizes the difference in coagulation rate between polymers, and fractionation Large pores with a molecular weight of 100,000 or more have not been obtained. Moreover, since a large amount of blending is performed, the original good performance of the polysulfone resin is likely to be lost.

Further, the method (1) is roughly classified into two methods: extraction of blended polymer and elution of inorganic granules. In the former, polyethylene glycol and polyvinylpyrrolidone are the main polymers, but it was difficult to obtain a sufficient pore size and to perform the extraction operation. In the latter example, the above-mentioned JP-A-58 is used.
-91822 gazette, after forming a film by mixing silica powder,
Although it has been successful in making a large hole of 0.05 μm or more by eluting with an alkali, it is described that there is a defect in water leakage.

In the method (1), a large amount of a non-solvent of a polysulfone resin or a swelling agent is mixed with a stock solution for film formation, and a film is formed immediately before phase separation of the stock solution for film formation. In this way,
Only membranes with defective water leakage can be obtained.

The method of (1) realizes the expansion of the pore size on the surface by blowing a high-humidity air at the time of film formation, but the method has the effect only on one side, and in particular, the cutoff molecular weight is small in the hollow fiber membrane. You can only get a small range.

Each of these conventional stock solutions for film formation is characterized by phase separation at low temperatures. Therefore, even if the temperature of the coagulation bath is increased in an attempt to increase the exchange rate of the non-solvent in the coagulation bath and the good solvent in the coagulation bath during film formation, the stock solution for film formation moves equilibrium toward the homogeneous system, and It has the property of forming a dense layer and the difficulty of low-temperature storage. In addition, since it is hydrophobic, it has the drawback that it can only be manufactured once it is dried and it is difficult to recover its water leakage performance without special treatment. Did not exist.

[Problems to be solved by the invention]

The present inventors arrived at the present invention as a result of analyzing the above-mentioned drawbacks and making intensive studies. In particular, it is an object of the present invention to provide a stock solution that is a low-temperature dissolution type that undergoes phase separation on the high temperature side, is easy to utilize the temperature effect during solidification, and is stable in storage of the stock solution at low temperatures.

[Means for solving problems]

The present invention has the following configurations. That is, (1) a hydrophobic polymer, polyvinylpyrrolidone, a good solvent for the hydrophobic polymer and polyvinylpyrrolidone, a nonsolvent or a swelling agent for the hydrophobic polymer, and a good solvent for the polyvinylpyrrolidone. A low-temperature-dissolving stock solution, which comprises an additive as an essential component, undergoes phase separation on the high-temperature side, and becomes a solution on the low-temperature side.

(2) A non-solvent or a swelling agent for the main hydrophobic polymer in a solution prepared by mixing and dissolving the main hydrophobic polymer and polyvinylpyrrolidone having compatibility with the hydrophobic polymer. And a method for producing a low temperature dissolution type stock solution, which comprises adding an additive which is a good solvent for the polyvinylpyrrolidone.

The method for preparing the low temperature dissolution type stock solution of the present invention will be specifically described below.

In the present invention, the main hydrophobic polymer (I) is
Polymers such as polyacrylonitrile, polymethylmethacrylate, polyolefin, polyimide, polycarbonate, polyarylate, polysulfone, and polyester. Of these, a polysulfone-based resin will be described as an example, but the resin is not limited to the resin.

The low temperature dissolution type stock solution of the present invention basically comprises a polysulfone resin (I), polyvinylpyrrolidone (II), a solvent (II
It is composed of a four-component system consisting of I) and additive (IV). The polysulfone-based resin (I) referred to here is usually the formula (1) or the formula (2) However, it may be a functional unit-containing or alkyl-based repeating unit and is not particularly limited.

As polyvinylpyrrolidone, not only polyvinylpyrrolidone but also modified polyvinylpyrrolidone, copolymerized polyvinylpyrrolidone and the like are used.

The solvent (III) is a solvent that dissolves both the polysulfone resin (I) and the polyvinylpyrrolidone (II). Various solvents such as dimethylsulfoxide, dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone and dioxane are used, but dimethylacetamide, dimethylsulfoxide, dimethylformamide and N-methyl-2-pyrrolidone are particularly preferable.

The additive (IV) may be any as long as it has compatibility with the solvent (III), serves as a good solvent for polyvinylpyrrolidone (II), and serves as a non-solvent or swelling agent for the polysulfone resin (I), Examples include water, methanol, ethanol, isopropanol, hexanol, 1,4-butanediol and the like. Water is the most desirable considering the production cost. The additive (IV) may be selected after considering the coagulability with respect to the polysulfone resin (I).

Each of these combinations is arbitrary, and it is easy for those skilled in the art to consider a combination having the above properties. Further, the solvent (III) / additive (IV) may be a mixed system of two or more kinds of compounds.

In contrast to the normal phase separation behavior of the stock solution for film formation, that is, on the low temperature side, the phase separation is surprisingly performed on the high temperature side. This principle will be described below.

Now, it is assumed that this film-forming stock solution is a homogeneous system at a certain temperature T. In this case, the additive (IV) is shielded from the polysulfone resin (I) by the polyvinylpyrrolidone (II) and does not directly interact with the polysulfone resin (I). (I) naturally solidifies in a system in which polyvinylpyrrolidone (II) is not mixed, and even if additive (IV) is added to such a concentration as to cause phase separation, a homogeneous system is maintained without phase separation. It is a translation. Here, if you raise the temperature,
By increasing the mobility of the molecule, the bond between polyvinylpyrrolidone (II) and the additive (IV) weakens, the hydrogen bond is broken, and the appearance of the additive (IV) that is not bonded to polyvinylpyrrolidone (II) appears. The above concentration is higher than that at the temperature T, and the polysulfone resin (I) and the additive (IV) interact with each other, which in turn causes solidification and phase separation of the polysulfone resin (I). It will be. That is, the membrane-forming stock solution undergoes phase separation on the high temperature side. Further, when the amount of the additive (IV) in this system is increased, the additive (I) at the temperature T of polyvinylpyrrolidone (II) is no longer present in both the temperature T and the stock solution system.
By adding the additive (IV) in an amount greater than the amount of V), the stock solution for film formation undergoes phase separation. However, if the temperature is further lowered, the molecular drivability of polyvinylpyrrolidone (II) decreases, the amount of binding with the additive (IV) increases, and the apparent additive (IV) concentration decreases, resulting in a system It becomes homogeneous again. When the temperature is raised again, the system becomes inhomogeneous, but when polyvinylpyrrolidone (II) is added, the amount of polyvinylpyrrolidone (II) and the additive (IV) bound increases, and the system becomes homogeneous again.

As described above, the phase separation behavior of this stock solution for film formation is the reverse of the usual one, and the phase transition is reversible.

As the composition of the film-forming stock solution, the main hydrophobic polymer (I) is used.
Is in a concentration range capable of forming a film and having characteristics as a film, and is 5 to 50% by weight. In order to obtain high water permeability and a large molecular weight cutoff, the polymer concentration should be lowered, and in this case, it is preferably 5 to 20% by weight. 5% by weight
In the case of less than, it is not possible to obtain a sufficient viscosity of the stock solution for film formation,
A film cannot be formed. If it exceeds 50% by weight, it becomes difficult to form through holes. As polyvinylpyrrolidone, those having a molecular weight of 360,000, 160,000, 40,000 and 10,000 are commercially available, and it is convenient to use this, but of course, other molecular weights may be used. However, since one of the reasons for adding polyvinylpyrrolidone (II) has a thickening effect, the higher the amount of addition, the smaller the amount, and the reversal of the temperature dependence of the phase separation phenomenon. Since it becomes remarkable, it is advantageous for obtaining a film having high water permeability. The addition amount of polyvinylpyrrolidone is preferably 1 to 20% by weight, particularly 3 to 10% by weight, but it depends on the molecular weight of polyvinylpyrrolidone to be used. Generally, if the amount added is too small or the molecular weight is too low, the phenomenon of phase separation reversal is difficult to obtain, and if the polymer concentration is high and the polymer molecular weight is too large, washing after film formation becomes difficult. Therefore, it is also one method to mix and use those having different molecular weights by sharing the roles.

The polymers (I) and (II) above are mixed and dissolved in the solvent (III). Additive (IV) is added to this, and particularly in the case of water, the polysulfone resin of the formula (1) has a high coagulability, so 7% by weight or less, particularly 1 to 5% by weight is desirable. In the case of the same resin of the formula (2), it is necessary to add 15% by weight or less, particularly 3 to 13% by weight. Also, in the case of polyacrylonitrile, it is necessary to add 5 to 20% by weight.
It is easily presumed that the amount of addition increases when an additive having a small solidification property is used. Adjustment of the additives of these coagulant additives is also related to the equilibrium water content of the hydrophobic polymer. As the concentration of the additive (IV) increases, the phase separation temperature of the stock solution for film formation decreases. It is necessary to set the phase separation temperature in consideration of the required aperture radius of the membrane.

〔Example〕

The present invention will be described in more detail by the following examples.

The phase separation temperature referred to here means the temperature at which the undiluted solution kept at a constant temperature becomes cloudy from a uniform state with the naked eye.

Example 1 15 parts of polysulfone (Udel P-3500), 8 parts of polyvinylpyrrolidone (K90) and 7 parts of 1,4-butanediol were added to 70 parts of dimethylacetamide, and heated and dissolved at 80 ° C. This four-component stock solution was a low temperature dissolution type, and phase separation occurred at 65 ° C.

Example 2 Polysulfone 15 parts, polyvinylpyrrolidone (K90) 8
And 2.4 parts of the solution were heated and dissolved in 75 parts of dimethylacetamide at 85 ° C. This four-component stock solution is of low temperature dissolution type, and
Phase separation occurred at 65 ° C.

Comparative Example 1 Polysulfone 12 parts and polyvinylpyrrolidone 6 parts were N-
It was added to 82 parts of methylpyrrolidone, and dissolved by heating at 80 ° C. This ternary stock solution was a high temperature dissolution type stock solution that became more uniform as the temperature was raised.

Example 3 15 parts of polyether sulfone (Victrex 300p),
8 parts of polyvinylpyrrolidone (K-90) and 8 parts of water were added to 75 parts of dimethylacetamide and dissolved by heating at 100 ° C. This four-component stock solution was a low temperature dissolution type, and phase separation occurred at 90 ° C.

Example 4 13.5 parts of polyacrylonitrile (molecular weight: about 10,000), 7 parts of polyvinylpyrrolidone (K-90), and 5 parts of water were added to 75 parts of dimethyl sulfoxide and dissolved by heating at 110 ° C. This 4
The stock solutions of the components were of low temperature dissolution type, and phase separation occurred at 100 ° C.

Example 5 15 parts of polysulfone (Udel P-3500), 8 parts of polyvinylpyrrolidone (K90) and 3 parts of water were added to 74 parts of N-methyl-2pyrrolidone, and heated and dissolved at 85 ° C. This four-component stock solution was a low temperature dissolution type, and phase separation occurred at 25 ° C.

〔The invention's effect〕

The low temperature dissolution type stock solution of the present invention is easy to store at low temperature and can be very advantageously used for the production of a semipermeable membrane having a large pore size. Moreover, since it contains the hydrophilic polymer, a dry film can be easily produced. Further, even if the hydrophilic polymer is crosslinkable or water-soluble, it can be used in applications where water resistance and elution resistance are required.

Furthermore, because of the porosity and hydrophilicity of the film formed by using it as a coating agent, it is possible to form a film that can efficiently evaporate water, and by utilizing the heat of vaporization at that time, efficient heat dissipation can be achieved. It can also be used to manufacture machines.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location D01F 6/54 D01F 6/54 D 6/56 6/56 6/94 6/94 (56) Reference Documents JP 59-139902 (JP, A) JP 61-93801 (JP, A) JP 61-402 (JP, A) JP 60-246812 (JP, A) JP 58- 104940 (JP, A) JP 58-8516 (JP, A) JP 57-35906 (JP, A) JP 59-58039 (JP, A) JP 58-24305 (JP, A) JP-A-58-205503 (JP, A) JP-A-60-97001 (JP, A)

Claims (2)

(57) [Claims] 1. A hydrophobic polymer, polyvinylpyrrolidone, a good solvent for the hydrophobic polymer and polyvinylpyrrolidone, a nonsolvent or a swelling agent for the hydrophobic polymer, and a good solvent for the vinylpyrrolidone. A low-temperature-dissolving stock solution, which comprises an additive as an essential component, undergoes phase separation on the high-temperature side, and becomes a solution on the low-temperature side. 2. A non-solvent or swelling agent for the main hydrophobic polymer in a solution prepared by mixing and dissolving a main hydrophobic polymer and polyvinylpyrrolidone having compatibility with the hydrophobic polymer. And a method for producing a low-temperature-dissolving stock solution, which comprises adding an additive that is a good solvent for the polyvinylpyrrolidone.